lack of recoil-operated semi rifles?... why?


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jason41987
April 17, 2012, 10:20 AM
ive been studying various designs of different firearms.. gaining a better understanding of them, how they function, the physics and engineering behind it all... and well, i seem to find an utter lack of recoil operated rifles... you have the 1941 johnson which wasnt much more than a prototype.. but after that one rifle... nothing

it should be clear that the FAMAS, and HK family rifles are delayed blowback (FAMAS being lever delayed, HK rifles being roller delayed)...

anyway.. blockback rifles have their problems, they usually run on the dirty side, though the simplest of designs, they can be the most dangerous too..

then you have the gas operated family of rifles... long-stroke, short stroke, rotating or tilting bolt, and each of these have their pros and cons as well... long stroke being more reliable, short stroke having less felt recoil.. and well, currently the short-stroke rotating bolt rifles dominate the autoloading market

and then theres the recoil operated design, of which the short-recoil action is in almost every single handgun out there now... long-recoil action was used in the old browning auto 5 shotguns i think..

so besides the johnson rifle which, to my understanding wasnt produced much due to reliability issues with a bayonet attached, and higher cost of production, slower reloading... why hasnt anyone ever went further into the developement of a recoil operated rifle?

advantages would be no gas loss, probably fewer moving parts, some say the '41 johnson had lesser felt recoil, the entire action could be in-line with the barrel and stock, reducing muzzle lift when firing, less weight, not needing a gas tube or piston... so what disadvantages would there be?

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TrickyDick
April 17, 2012, 10:30 AM
I think it may be due to when the bullet is travelling down the barrel, the bolt is moving rearward, thus causing lower accuracy (Equal & Opposite reaction). The idea of gas operated rifles is that the bullet is already exiting the barrel before any parts move. It's not that it won't work, it's just unsuitable for accuracy. this is why recoil operated firearms are usually; pistols, submachineguns and shotguns, where distance/accuracy isn't a huge factor.

jerkface11
April 17, 2012, 10:31 AM
Remington model 8 and 81, for more modern ones there's Highpoint carbines, Kel-tec sub 2000, and the Beretta carbine.

jmr40
April 17, 2012, 10:31 AM
The bolt does not move until after the bullet has left the barrel with any gun design.

Sam1911
April 17, 2012, 10:33 AM
Another recoil-op rifle was the Remington Model 8 (http://en.wikipedia.org/wiki/Remington_Model_8) (later 81).

Several basic issues come to mind. The first, and probably most important, is that when you disconnect the barrel from the action and make it part of the reciprocating mass, accuracy suffers. It HAS to. When you consider how precision rifles focus so heavily on making the barrel and receiver into on solid unit, and stabilizing them against any motion, having the barrel bang back and forth, and then to have locking assemblies with loose enough clearances to be able to disengage and re-engage, and keep working when fouled, there's just no good way around the issue.

(Yes, there were plenty (Auto 5/Rem Model 11, on up the 11-48) and are still a few recoil-operated shotguns (Benellis...sort of). They obviously don't have the precision accuracy concerns to live with.)

Another concern is reliability as you mentioned. Even the shotguns using the recoil action have been known to be temperamental. Gotta be clean. And dry. Or oiled, just right. Or ... who knows? :confused:

And another is that confusingly, recoil-op guns actually tend to produce a stronger recoil sensation than gas-op guns. Strange but true.

briansmithwins
April 17, 2012, 10:37 AM
Recoil operated rifles suffer from the problem that if anything touches the barrel you get a stoppage. You can put a shroud over the barrel but that adds weight.

BSW

animator
April 17, 2012, 10:39 AM
The Barrett M82 is a recoil action with acceptable accuracy.

jmorris
April 17, 2012, 10:42 AM
The first, and probably most important, is that when you disconnect the barrel from the action and make it part of the reciprocating mass, accuracy suffers. It HAS to. .

While I agree with this principal I was shocked to learn my 1919 grouped better at 100 yards that more than a few bolt action rifles I have come across.

68wj
April 17, 2012, 10:45 AM
advantages would be no gas loss, probably fewer moving parts, some say the '41 johnson had lesser felt recoil, the entire action could be in-line with the barrel and stock, reducing muzzle lift when firing, less weight, not needing a gas tube or piston... so what disadvantages would there be?
What does gas loss matter? There isn't enough to cause any effect to the bullet in a gas operated rifle.

Probably fewer moving parts? The old standard M2 .50 cal has many moving parts that have to work in unison together to function. It is more finicky than many believe.

Never shot a Johnson, don't know.

In line with barrel and stock, like a direct impingement AR-15?

Less weight? Part of a recoil operated system is based on the moving masses of its parts. Weight may be increased depending on design.

I am okay with a gas tube or piston, but deleting these parts would be a benefit if someone was opposed to them.

There are modern recoil operated guns though that do work well. Look at the success of Benelli's line of "intertia-driven" guns. However, one of their downsides was discovered when the .mil was looking for a new shotgun in semi-auto form. What happened? Benelli developed a gas piston gun and abandoned its ultra reliable claims of the ID system. This was primarily because of the modular necessities of the military and adding of weight (lights, side saddles, etc) to the gun that affected the recoil mechanism.

Can it be done? SURE. There may not be anything to gain though. Time will tell.

earplug
April 17, 2012, 11:09 AM
Its been about thirty years since I shot a Johnson. I recall the perceived recoil was stronger then a M1/m1A.
Many would agree that a A5 Browning gives more of a kick then a Remington 1100 of the same era.
Accuracy of the recoil operated gun with a moving barrel would be harder to engineer into the design and wear would effect the zero.

jim243
April 17, 2012, 11:15 AM
and well, i seem to find an utter lack of recoil operated rifles...

I really don't understand the question or post. Are you saying that delayed blow back is not a recoil operated rifle??

From the Browning machine gun (M2) to the Thompson Sub-Machine Gun to the Uzi or Mac-10, the MP-5 and of course the Grease Gun of WWII all were and are recoil operated as are all pistols with the exception of the Desert Eagle which is gas operated.

How can you say there has been no development. I believe the M-1 carbine is a recoil design as well (I may be wrong). Just because they do not have a moving barrel does not make them not a recoil operated design (at least in my opinion).

Jim

Oh, yes, I forgot the Remington 74 and 7400

MachIVshooter
April 17, 2012, 11:15 AM
Recoil operated rifles work, but the bottom line is gas operated works better and generally results in a much lighter weapon. The original AR-15 was barely 5 pounds, IIRC. It got heavier to soldier proof it, of course.

Carl N. Brown
April 17, 2012, 11:16 AM
Shooting the Remington 81 in .300 Savage is supposed to be a kick.

You have the momentum of the bolt and barrel recoiling together, and when they stop and seperate, it is supposed to be jolting.

jerkface11
April 17, 2012, 11:17 AM
Shooting the Remington 81 in .300 Savage is supposed to be a kick.

You have the momentum of the bolt and barrel recoiling together, and when they stop and seperate, it is supposed to be jolting.

Mine is a .35 rem and the recoil isn't jolting at all even with a steel buttplate.

rcmodel
April 17, 2012, 11:21 AM
I believe the M-1 carbine is a recoil design as well (I may be wrongShort stroke gas piston.

rc

Tirod
April 17, 2012, 11:26 AM
Recoil operates by causing parts of the weapon to move in the opposite direction of the bullet. Small calibers simply don't offer enough operating mass for reliable actions.

As for those "dirty" blowbacks, consider that what you are really experiencing with any semi auto is "delayed" blowback. Timing has to be advanced enough to get the bolt unlocked as long as the case pressure is low enough to prevent blowing it out. That doesn't mean there isn't any. Gas still blows back past the case onto the action.

Got a piston rifle? Rub a dozen fired cases on your white t-shirt at the range bench and tell me what you get. Fire 40 rounds and then clean the bolt with your t-shirt tail.

Self loading actions all initiate unlocking early enough that the case can be forced against the bolt face. The Army showed in tests with the extractors removed that the M4 will still fire full auto. Under the dynamics of actual operation, extractors slipping off has a lot more to do with bouncing as the bolt is suddenly shocked into reverse - which is why Crane added more spring pressure and an o-ring to counteract it. That stopped the one in a thousand failure to extract, likely caused by a sticking case too swelled from gas pressure to move.

Recoil operated weapons need mass moving to finish the cycle of action, and small calibers don't offer enough. Nonetheless, they get just as dirty as the rest, as those of us who've cleaned the M2 and Mk17 can tell you about.

There's no free lunch there.

Gtscotty
April 17, 2012, 12:01 PM
I really don't understand the question or post. Are you saying that delayed blow back is not a recoil operated rifle??

From the Browning machine gun (M2) to the Thompson Sub-Machine Gun to the Uzi or Mac-10, the MP-5 and of course the Grease Gun of WWII all were and are recoil operated as are all pistols with the exception of the Desert Eagle which is gas operated.

How can you say there has been no development. I believe the M-1 carbine is a recoil design as well (I may be wrong). Just because they do not have a moving barrel does not make them not a recoil operated design (at least in my opinion).


I think you are confusing Blowback/Delayed Blowback actions with Recoil operated actions. I believe recoil operated actions are partially defined by the fact that they are locked during firing. The recoiling barrel/bolt/action/slide, etc, starts moving rearward together upon firing, and at some point in the cycle the action is cammed open to allow for ejection of the spent casing and insertion of a fresh cartridge.

Blowback weapons, on the other hand, fire from an unlocked bolt, only spring tension and the mass of the bolt keep the chamber closed long enough for pressure to drop. For this reason, only relatively low power rounds are generally used in blowback weapons (more powerful rounds would require a much heavier heavier bolt/slide and stronger springs).

Delayed Blowback weapons operate in the same manner as blowback weapons, but incorporate some method of delaying the blowback cycle longer than simple spring weight and bolt mass would. Regardless, it is still just a modified blowback action (as opposed to a recoil operated action), and the bolt is not truely locked during firing.

I'm fairly certain the Rem 74 and 7400 is also gas operated by the way.

I'd agree with pretty much everybody who has answered this post, its harder to achieve top accuracy when most of our action/barrel is moving around with each shot. Also, as some have said, I would not expect a recoil operated rifle to, on average, exhibit the reliability of a similar gas operated rifle.

56hawk
April 17, 2012, 01:00 PM
I'm not sure why there aren't more recoil operated rifles, but I can say it's not because of accuracy. If you look at the longest confirmed sniper kills three of the top ten were with recoil operated rifles. All the others were bolt action.

http://en.wikipedia.org/wiki/Longest_recorded_sniper_kills

BigG
April 17, 2012, 01:22 PM
Weight generally weighs against recoil operation in a shoulder fired rifle. If you look at the operations of a recoil system you know the weight of the operating parts have to equal the recoil of the cartridge less spring which I believe is small. In other words a breech block of a recoil operated 30-06 would be around 7 pounds or so, IIRC. Most people do not want to carry a rifle that weighs more than 7 pounds so the gun would be too heavy. Then there is the moving barrel to deal with... etc.

briansmithwins
April 17, 2012, 05:22 PM
There are only two types of self loading firearm actions: Gas and Recoil.

Blowback and delayed blowback are variants of gas operated: the case is a one use, throw away gas piston.

Recoil actions always involve the barrel moving backwards. Some stay locked for a distance shorter than the case length (short recoil) some stay locked for a distance longer than the case length (long recoil).

There are advantages and disadvantages to both recoil and gas operation. Every design is a compromise.

BSW

Jim Watson
April 17, 2012, 06:40 PM
The shortage of recoil operated rifles is balanced by the plethora of recoil operated handguns.
Gas operation runs the other way.
Like, why is the sky blue and up not down?

Carl N. Brown
April 17, 2012, 08:00 PM
I did overlook that the Barrel M82 .50 rifle is recoil operated: bolt and barrel are locked together, and they recoil locked together for a distance calculated to allow the bullet time to exit the barrel and pressure to drop from its peak, then are un-locked, to allow the bolt to recoil to the rear, with a boost from an accelerator trip (much like the Browning machineguns).

PercyShelley
April 17, 2012, 08:02 PM
I can personally attest that the perceived recoil of a remington 81 in .35 Rem is extremely unpleasant and snappy.

A friend of mine bought one and we took it to the range along with a Swiss Schmidt Rubin m1911 rifle and twenty rounds. We shot about five each and decided it simply wasn't fun. The Schmidt Rubin, 7.5x55 chambering and steel buttplate, was downright tame by comparison.

I suspect what's going on is that the barrel and bolt, which travel quite a ways in this long-recoil design, don't greatly slow down from compressing the recoil and barrel spring and rebound elastically off the receiver. This would make the recoil energy much higher than you would expect for a rifle that heavy. Hatcher's Notebook (http://www.amazon.com/Hatchers-Notebook-Julian-S-Hatcher/dp/0811707954) mentions evidence that something similar happens in 1911 pistols.

jason41987
April 17, 2012, 08:08 PM
yeah.. i dont think accuracy is as much of an issue as believed.. the johnson of WWII and barrett rifles are recoil operated and had better accuracy than many modern battle/assault rifles do now... easily surpassing the poor accuracy of an AK... exactly what the grouping on the johnson was i dont know, never fired one but the claims ive heard that it was pretty close to the garand....

as for recoil.. you can shoulder fire a barrett without just a small fraction of a kick youd get from a bolt action .50bmg... but its well made compensator/brake certainly helps...

i cant seem to find any information on actual accuracy of the 1941 johnson though.. and only on the 1919, but indications are they were still more accurate than a lot of military rifles...

with such limited samples of recoil operated rifles, its hard to say what its limits are.. and if someone made one now, most military carbine rifles arent any longer than the forearm anyway, so a shroud/forearm to cover it wouldnt add much weight

68wj
April 17, 2012, 09:18 PM
yeah.. i dont think accuracy is as much of an issue as believed.. the johnson of WWII and barrett rifles are recoil operated and had better accuracy than many modern battle/assault rifles do now... easily surpassing the poor accuracy of an AK... exactly what the grouping on the johnson was i dont know, never fired one but the claims ive heard that it was pretty close to the garand....

as for recoil.. you can shoulder fire a barrett without just a small fraction of a kick youd get from a bolt action .50bmg... but its well made compensator/brake certainly helps...

i cant seem to find any information on actual accuracy of the 1941 johnson though.. and only on the 1919, but indications are they were still more accurate than a lot of military rifles...

with such limited samples of recoil operated rifles, its hard to say what its limits are.. and if someone made one now, most military carbine rifles arent any longer than the forearm anyway, so a shroud/forearm to cover it wouldnt add much weight
How can you say the Johnson "easily" surpasses the AK when you then say you are unfamiliar with how a Johnson groups (almost a Garand?)? And the Barrett is an apples to oranges comparison when you are talking about a 30 pound, purpose built rifle that IS capable of great accuracy, but gives up the mobility of a service rifle or carbine.

Gtscotty
April 17, 2012, 10:05 PM
And the Barrett is an apples to oranges comparison when you are talking about a 30 pound, purpose built rifle that IS capable of great accuracy, but gives up the mobility of a service rifle or carbine.

It also gives up economy.... at $8-9K a copy, they certainly aren't giving them away. That price level allows for the custom fitting necessary for a recoil operated rifle to achieve the Barrett's excellent level of accuracy. I really don't think you'd be able to build a recoil operated AR-15/AR-10-like rifle with equivalent accuracy for the same price... Having the barrel AND action jump back and forth with each shot is just really not as conducive to accuracy as having the barrel remain in one spot, and the bolt move linearly. I'm not saying it can't be done, its just not the cheapest/most efficient way to go about building an accurate yet reasonably light weight self loading rifle.

Blowback and delayed blowback are variants of gas operated: the case is a one use, throw away gas piston.

.... Correct, in a somewhat esoteric sense, but not really useful. When someone refers to a gas operated action, I think we can safely assume they are generally not referring to a blowback action.

PercyShelley
April 17, 2012, 10:48 PM
Interesting that other posters' experience with the Remington 81 does not mirror my own. I wonder if there is a friction buffer that gets worn out over time. I seem to recall that the auto 5, which is a related design, has something like that.

I have heard, but have not personally verified, that Johnson 1941s are prone to vertical stringing. Whether that's a function of the moving barrel, I would not venture to speculate.

While fussing with a 1911 I noticed something that might limit the scaling on Browning-style tilting barrel short-recoil designs. Because the barrel is tilted out of engagement with the slide while unlocked there is a slight angle between the bore axis and the bolt axis during feeding. This is not a huge issue with stubby pistol rounds (although some have fingered this angle as a potential source of feeding problems in sub-compacts because the angle is larger due to the shorter barrel), but with the long, skinny rifle rounds it seems possible that the round could catch during feeding, or slip from under the extractor.

Most recoil-operated rifles use a separate bolt and bolt carrier, but this would suggest that the most common recoil operated design does not scale up well.

jason41987
April 18, 2012, 07:41 AM
hmm.. ive been thinking about it.. and i wonder... what if there was a recoil operated rifle in which the barrel didnt actually move.. more so like a rear-piston gas system..

imagine this.. the inside of the breach of the barrel is hollowed out.. inside this fits a chamber block that holes and supports the cartridge... when you fire it, this block holding the cartridge slams back, hits a block, forcing the bolt to continue without it, extracting the cartridge... since the breach plug wouldnt completely exit the rear of the barrel, no gasses would escape into the action, they would all be sent forward while the barrel remains still giving the rifle a recoil operation, or an enclosed blowback action, or the breach block could act as a short-stroke piston....

thats one idea ive been working on designing in 3D

jason41987
April 18, 2012, 07:43 AM
hmm.. i can see a problem with fouling in that last idea... might give you the same problems an HK rifle has with buildup in the roller recesses in the barrel

Sam1911
April 18, 2012, 07:53 AM
Have you looked into how the Benelli inertia system works? http://www.benelliusa.com/innovations/

PercyShelley
April 18, 2012, 08:18 AM
jason41987, look up the "floating chamber" .22 adaptors for the 1911. They work similarly to what you describe.

68wj
April 18, 2012, 08:58 AM
jason41987, look up the "floating chamber" .22 adaptors for the 1911. They work similarly to what you describe.
To increase felt recoil.;)

I still don't get the fear of a gas system. Oh noes, gas gets in the action and it is dirty. It is debatable there is any affect on function, and proven that even when stoppages are blamed on fouling, it takes a massive amount of fired rounds to do anything other than make a mess.

Considering cost, accuracy, weight, and reliability, there is currently no better system than gas operated for high power firearms. An autoloader requires an energy source to function, but where does the energy come from? The simple rearward energy (recoil) of a .308 gives ~19-22 ft/lbs while some of that is also absorbed by the shooter and affected by the weight of the firearm. All the while, the action must contain ~60,000 PSI of pressure inside of the chamber. A gas system taps some of that high pressure and uses the energy to cycle the action independent of the shooter's shoulder or weapon's weight. There is the variable of gas pressure for various loads, but a much larger operating window. A 9mm pistol is approximately half the pressure, and a 12ga shotgun even less, so alternate operating systems are more suited here and sometimes ideal.

PercyShelley
April 18, 2012, 09:13 AM
To increase felt recoil.

I still don't get the fear of a gas system. Oh noes, gas gets in the action and it is dirty. It is debatable there is any affect on function, and proven that even when stoppages are blamed on fouling, it takes a massive amount of fired rounds to do anything other than make a mess.

Considering cost, accuracy, weight, and reliability, there is currently no better system than gas operated for high power firearms. An autoloader requires an energy source to function, but where does the energy come from? The simple rearward energy (recoil) of a .308 gives ~19-22 ft/lbs while some of that is also absorbed by the shooter and affected by the weight of the firearm. All the while, the action must contain ~60,000 PSI of pressure inside of the chamber. A gas system taps some of that high pressure and uses the energy to cycle the action independent of the shooter's shoulder or weapon's weight. There is the variable of gas pressure for various loads, but a much larger operating window. A 9mm pistol is approximately half the pressure, and a 12ga shotgun even less, so alternate operating systems are more suited here and sometimes ideal.

More to the point, it increases the recoil velocity of the moving parts, an important consideration if you want to shove around a slide originally dimensioned for a .45 with a mere .22.

I recall a test on arfcom or somesuch were a barrel was chronographed before and after the gas port was drilled. The difference in velocity was slightly above the level of statistical noise (~30 FPS). Most gas systems on semi-auto rifles are designed to bleed gas off after a certain distance. The problem is not finding sufficient energy to cycle the action (excepting weird corner cases like .22 conversions). The problem is managing the enormous amount of energy that there is.

That said, I don't see anything dreadfully wrong with the idea of a recoil-operated rifle. Certainly, it would take a hit in accuracy, but for many applications this wouldn't be enough to matter. A recoil-operated rifle that were only as accurate as, say, an HK USP or custom-tuned 1911 would be more than accurate enough for whacking tasty ungulates at typical distances.

You would shed the mass of the gas system, but you would have to reinforce the receiver where the barrel would be bonking into it. The action is locked, same as a gas-op weapon, so it could handle quite powerful cartridges (as the M82 proves). There would be some sensitivity to using different barrel lengths due to the extra weight, but retarded blowbacks and gas-op rifles usually have to compensate for the longer pressure curve in different length barrels by roller geometry or gas port diameter. So really, it doesn't make an enormous difference which of the three major* self-loading operations cycles a design uses.

The one big advantage I see is that since the barrel is already floating in the receiver, it's fairly easy to remove on most recoil-operated designs. A recoil operated rifle would lend itself well to being a takedown design, and indeed the Remington 81 I've shot could be broken down into two reasonably small halves.


*Now, blow-forward actions, those are just silly.

earplug
April 18, 2012, 09:34 AM
A recoil operated firearm may be very accurate when new. But the barrel sliding and recoiling parts would wear over time. Consider the wear on a match grade pistol.
A fixed barrel design does not have this problem.

jason41987
April 18, 2012, 12:32 PM
seems a floating chamber would give you most most the benefits of a recoil operated design without the negatives which all seem to be present because the barrel itself moves...

this post doesnt neccessarily mean im looking for anything recoil operated, or that it may or may not be a better design... but as this conversation moves on it seems it has roughly the same number of benefits and tradeoffs as any of the other action types (blow back or gas)... which actually doesnt answer any questions... just makes me wonder even more why they, for the most part, just dont exist in rifles... as a student of engineering (i say this not to say im still in school for it, but to emphasize that you'll never stop learning) its in my nature to ask "why" especially when the answers seem to be so elusive

briansmithwins
April 18, 2012, 02:49 PM
seems a floating chamber would give you most most the benefits of a recoil operated design

Floating chambers amplify blowback operation. Useful when doing .22LR conversions but overkill otherwise.

Look up 'primer actuation' for kicks.

If you're a engineering student interested in firearms you need to read The Machine Gun by Col. Chinn. More ideas have been discovered pertaining to firearms than stars in the sky.

http://www.germanmanuals.com/Links.html

BSW

moxie
April 18, 2012, 03:34 PM
Gtscotty is correct. Blowback does not equal recoil operated. the M3 and others mentioned are blowbacks, mostly operating from an open bolt.

SlamFire1
April 18, 2012, 04:17 PM
That said, I don't see anything dreadfully wrong with the idea of a recoil-operated rifle. Certainly, it would take a hit in accuracy, but for many applications this wouldn't be enough to matter. A recoil-operated rifle that were only as accurate as, say, an HK USP or custom-tuned 1911 would be more than accurate enough for whacking tasty ungulates at typical distances.


The basic problem is that it has been so long since these issues where actually hashed out as hardware, no one who was alive then when the downselect occurred, is around now. It is beyond living memory.


LTC Chin's book of the Machine Gun Vol IV goes over the advantages and disadvantages of different mechanisms.


Whatever the theorical advantages of one type over another, what we do know is that gas operation is the most common mechanism for high powered semiautomatic rifles.

And, I don't know exactly why, but it must be because it worked better.

conhntr
April 18, 2012, 04:35 PM
//It also gives up economy.... at $8-9K a copy, they certainly aren't giving them away. That price level allows for the custom fitting necessary for a recoil operated rifle to achieve the Barrett's excellent level of accuracy. I really don't think you'd be able to build a recoil operated AR-15/AR-10-like rifle with equivalent accuracy for the same price//

There is a 1911 manufacturer that can gurantee 50 yard accuracy of 1.5" for 1500$.

briansmithwins
April 18, 2012, 05:31 PM
The big advantage of gas operation is you've got a lot of power to work with and can change the variables a lot. Gas port location, size, and gas piston diameter can all be changed to get the desired result. It's also a lot easier to protect the reciprocating parts (gas piston, operating rod) with some type of shroud than it is to enclose a reciprocating barrel.

BSW

Gtscotty
April 18, 2012, 11:26 PM
There is a 1911 manufacturer that can gurantee 50 yard accuracy of 1.5" for 1500$.

That's interesting, but I'm not sure what a pistol with a mechanical accuracy of 3" at 100 yds has to do with the accuracy of reasonably priced recoil operated rifles. I bet for $1500 you could buy a gas impingement AR pistol that will shoot a group half that size at the same distance. Regardless, I think we are getting into an apples and oranges situation again.

Elkins45
April 19, 2012, 11:29 PM
I have a Marlin Camp Carbine in 9mm and the bolt is a fairly big chunk of steel with a relatively stiff spring. It's a straight blowback design with the barrel rigidly attached to the receiver. AFAIK it's the only blowback centerfire rifle I've ever encountered.

Wonder how heavy the bolt would need to be to build a straight blowback rifle in a powerful centerfire caliber like 30-06? I suspect you would need some serious mass to tame that sort of recoil impulse.

jerkface11
April 19, 2012, 11:53 PM
I can personally attest that the perceived recoil of a remington 81 in .35 Rem is extremely unpleasant and snappy.

That's odd I don't find mine unpleasant at all.

Matthew Courtney
April 20, 2012, 07:21 AM
The bolt does not move until after the bullet has left the barrel with any gun design.
Patently untrue. Most bolt's/breeches stay locked until the bullet leaves the barrel, but most(if not all) of them move the instant the powder is ignited. With recoil operated firearms, the barrel moves with the bolt, which complicates accuracy.

68wj
April 20, 2012, 08:53 AM
Patently untrue. Most bolt's/breeches stay locked until the bullet leaves the barrel, but most(if not all) of them move the instant the powder is ignited. With recoil operated firearms, the barrel moves with the bolt, which complicates accuracy.
In a gas operated weapon, the bolt does not begin to move until after the bullet has passed the gas port and the pressure begins to manipulate the cycling mechanism, relatively long after the powder is ignited. You can also see in many recoil operated firearms how the bolt and barrel remain locked together until a certain point. All of these variables are manipulated through weapon design (timing, tension, mass, etc).

Watch the first few seconds of this pistol here: http://www.youtube.com/watch?v=Rqu9jCuR5P0

jason41987
April 20, 2012, 09:03 AM
i think when you guys talk about accuracy of the recoil operation losing accuracy due to the moving barrel, its not so much the barrel moving before the bullet leaves the barrel, as much as its the likeliness of the barrel not returning to perfect zero every time would be my guess...

unless a chamber could be made to move independant of the barrel... which it could very well be made to do, then it seems like delayed blowback or gas is the way to go for a rifle with a goal of 1 to 1.5MOA in mind

Sam1911
April 20, 2012, 09:37 AM
...its the likeliness of the barrel not returning to perfect zero every time would be my guess...

unless a chamber could be made to move independant of the barrel

Either way, any movement of the barrel or portion of the barrel that is independant of the sighting mechanism, or which has the potential to alter any critical (or even secondary) relationships between the parts of the rifle from shot to shot is the antithesis of the principles of building a precision rifle.

FWIF, the Barrett M82 is not known for being especially accurate, compared to other styles of .50BMG rifle. In fact, Anzio builds a stabilization system to try and help improve things by controlling/limiting barrel movement. All in the attempt to try to bring up the precision of that system to something more like a bolt-action rifle.

jmorris
April 20, 2012, 09:55 AM
The only specimen I have is the 1919 and would say the limit is how far you can haul it.



There is a 1911 manufacturer that can gurantee 50 yard accuracy of 1.5" for 1500$

I have SV's that shoot one hole groups at that distance but at twice the cost. What's the point though, that kind of accuracy is no problem for a 1919 either and more to the point of the thread.



I have a Marlin Camp Carbine in 9mm and the bolt is a fairly big chunk of steel with a relatively stiff spring. It's a straight blowback design with the barrel rigidly attached to the receiver. AFAIK it's the only blowback centerfire rifle I've ever encountered.

There are a lot of centerfire pistol caliber carbines that work the same way, the 9mm AR being a good example, for this thread, as all rifle chamberings use the gas system.

If you wanted a rifle round to work the same you would need to add weight or spring. You would also need to add a hydraulic jack system to rack the bolt if you simply added spring tension.

.45Guy
April 20, 2012, 12:08 PM
Wonder how heavy the bolt would need to be to build a straight blowback rifle in a powerful centerfire caliber like 30-06?
~27 pounds if I recall correctly. (M2 ball)

Really though, everything else aside the reason that recoil operated longarms fell to the wayside is simple economics. I love my 8s and 81s, but I don't foresee anyone bringing such a complex design back into production anytime soon.

briansmithwins
April 20, 2012, 12:10 PM
The bolt does not move until after the bullet has left the barrel with any gun design.

Nope.

On blowback and delayed blowback firearms the bolt starts moving back as soon as the cartridge is ignited. You can get away with this on low pressure, straight walled pistol cartridges, rifle rounds tend to get the case heads torn off because the bolt is opening while the front of the case is still stuck to the chamber walls.

This phenomenon is why HK's delayed blowback weapons have fluted chamber to keep the cases from sticking. The other work around is to oil or grease the cartridges.

BSW

briansmithwins
April 20, 2012, 12:16 PM
On springs:

The spring hardly adds any force to keeping the bolt closed on a blowback operated weapon. Say 9mmP runs at 30k psi. The pressure acting on the head of the case (~0.1^2") is 3000 psi. What spring are you going to use to counteract the 3000 lbs of force that trying to blow the bolt open?

The spring can slow down the bolt (less force acting over a longer travel) and stores the energy needed for cocking, stripping the next cartridge, feeding, and chambering, but it doesn't hold the bolt closed against the force of the cartridge in any design I'm aware of.

BSW

cat9x
April 20, 2012, 12:27 PM
As other's have said there are advantages and disadvantages to recoil operated firearms. The Remington Model 8 & 81 are among the better known long recoil rifles. There were plans once upon a time to scale up the 8/81 action for the 30-06 cartridge but this of course never came to fruition. Felt recoil of 8/81's in 35Rem and 81's in 300Sav are not that bad, but they have more than you would think the round would have. For a video of seeing how the 8/81 platform can be shot, check out the youtube video below,

http://www.youtube.com/watch?v=zILCO-SzVdY

.45Guy
April 20, 2012, 12:41 PM
Great vids!

PercyShelley
April 20, 2012, 12:45 PM
That's odd I don't find mine unpleasant at all.

Yes indeed, I noted the discrepancy. I wonder if the barrel spring was worn on the example I fired, or if there's a friction buffer like in the auto 5 that gets worn out and was in need of replacement.

Obviously, it was some mechanical reason, and not at all possible that I just have daintier shoulders than you do.

~27 pounds if I recall correctly. (M2 ball)


I have lent out my copy of Hatcher's Notebook, but that's about the figure I recall from it for a theoretical straight-blowback .30-06.

Interestingly, straight blowback does scale up very well on cartridges with rebated rims. The Becker family of aircraft cannons (including the type 99 zero-sen wing cannons and the Mk 103 ME-262 nose cannons of WWII fame) are essentially straight blowback. Yes, the firing occurs while the bolt is still moving forwards, but that contributes far less to the reduction of bolt mass than the case head design. I think these used lubricated cartridges.

FWIF, the Barrett M82 is not known for being especially accurate, compared to other styles of .50BMG rifle. In fact, Anzio builds a stabilization system to try and help improve things by controlling/limiting barrel movement.

That is also my understanding. Are M82s even used in competitive shooting alongside bolt action .50s?

I hadn't heard of the Anzio aftermarket tweaks before. That is interesting, thank you.

Sam1911
April 20, 2012, 01:17 PM
I hadn't heard of the Anzio aftermarket tweaks before. That is interesting, thank you.


Looks interesting...

http://www.anzioironworks.com/BARRETT-M82-UPGRADES.htm

Matthew Courtney
April 20, 2012, 03:33 PM
In a gas operated weapon, the bolt does not begin to move until after the bullet has passed the gas port and the pressure begins to manipulate the cycling mechanism, relatively long after the powder is ignited. You can also see in many recoil operated firearms how the bolt and barrel remain locked together until a certain point. All of these variables are manipulated through weapon design (timing, tension, mass, etc).

Watch the first few seconds of this pistol here: http://www.youtube.com/watch?v=Rqu9jCuR5P0
The force of the brass pushing rearward moves the bolt rearward against the locking lug surfaces. If the bolt didn't move back until the lugs mating surfaces were firmly against one another, the lugs would not be needed.

Matthew Courtney
April 20, 2012, 03:38 PM
On springs:

The spring hardly adds any force to keeping the bolt closed on a blowback operated weapon. Say 9mmP runs at 30k psi. The pressure acting on the head of the case (~0.1^2") is 3000 psi. What spring are you going to use to counteract the 3000 lbs of force that trying to blow the bolt open?

The spring can slow down the bolt (less force acting over a longer travel) and stores the energy needed for cocking, stripping the next cartridge, feeding, and chambering, but it doesn't hold the bolt closed against the force of the cartridge in any design I'm aware of.

BSW
3000 psi only equals 3000 pounds of rearward force when the area to which said pressure is applied equals one inch.

68wj
April 20, 2012, 03:50 PM
The force of the brass pushing rearward moves the bolt rearward against the locking lug surfaces. If the bolt didn't move back until the lugs mating surfaces were firmly against one another, the lugs would not be needed.
Yes, force is exerted on the bolt, but that is not moving the bolt outside of any play between the parts. The bolt is not considered a moving part until it begins to unlock.

briansmithwins
April 20, 2012, 05:52 PM
3000 psi only equals 3000 pounds of rearward force when the area to which said pressure is applied equals one inch.

I was using a rough number of 30,000psi for the pressure generated by the burning gas, and I used 1/10th inch for the area. Using those numbers would indeed give a force of 3000psi on the bolt face.

BSW

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