G3 at the Range

[Grunt]

Hmm, I should try setting up the chronograph to see what the velocity is of an ejecting case. Probably higher than the bullet! They do love to fling them out quite a ways, don't they!

 

[stoky]

They throw them far, so you don't see how badly they mangle the cases.

 

[joem1945]

I've got a CETME that gave me problems from the get go. I found out that it needs steel cased ammo to run right. I replaced the stock wood stock from HK that made it more confortable to shoot.

 

[HKGuns]

Mine doesn't mangle cases, it just flings them. There is an occasional case mouth dent, when it hits the side of the rifle just right, but nothing that isn't fixable.

 

[Grunt]

Yup, mine too. Not really mangling cases, especially with the port buffer installed but it has some vigorous ejection.

 

[Holescreek]

High speed video is a little blurry but shows a full auto Cetme firing. Cases aren't really being thrown a long way as they are getting bounced off the receiver. The port buffers get them redircted before they build up a lot of momentum. For the guy building his own, Numerich sells the steel weld-on HK port buffer for $10 that everyone else sells for $30.

https://www.youtube.com/watch?v=sJVlkJ4T-uc

 

[Slamfire]

I love the engineering in the HK 91 rifle. It is a well thought out rifle and the semi rigid locking mechanism is fascinating from a mechanical engineering veiw point.

Prior to WW2 there were lots of delayed or retarded blow back mechanisms. But they all used active lubrication in the form of oil, grease, wax lubricants, or oilers.

soon to be General Hatcher discusses the state of the art in this 1933 article:


Army Ordnance Magazine, March-April 1933

Automatic Firearms, Mechanical Principles used in the various types, by J. S. Hatcher. Chief Smalls Arms Division Washington DC.

Retarded Blow-back Mechanism………………………..

There is one queer thing, however, that is common to almost all blow-back and retarded blow-back guns, and that is that there is a tendency to rupture the cartridges unless they are lubricated. This is because the moment the explosion occurs the thin front end of the cartridge case swells up from the internal pressure and tightly grips the walls of the chamber. Cartridge cases are made with a strong solid brass head a thick wall near the rear end, but the wall tapers in thickness until the front end is quiet thin so that it will expand under pressure of the explosion and seal the chamber against the escape of gas to the rear. When the gun is fired the thin front section expands as intended and tightly grips the walls of the chamber, while the thick rear portion does not expand enough to produce serious friction. The same pressure that operates to expand the walls of the case laterally, also pushes back with the force of fifty thousand pounds to the square inch on the head of the cartridge, and the whole cartridge being made of elastic brass stretches to the rear and , in effect, give the breech block a sharp blow with starts it backward. The front end of the cartridge being tightly held by the friction against the walls of the chamber, and the rear end being free to move back in this manner under the internal pressure, either one of two things will happen. In the first case, the breech block and the head of the cartridge may continue to move back, tearing the cartridge in two and leaving the front end tightly stuck in the chamber; or, if the breech block is sufficiently retarded so that it does not allow a very violent backward motion, the result may simply be that the breech block moves back a short distance and the jerk of the extractor on the cartridge case stops it, and the gun will not operate.

However this difficultly can be overcome entirely by lubricating the cartridges in some way. In the Schwarzlose machine gun there is a little pump installed in the mechanism which squirts a single drop of oil into the chamber each time the breech block goes back. In the Thompson Auto-rifle there are oil-soaked pads in the magazine which contains the cartridges. In the Pedersen semiautomatic rifle the lubrication is taken care of by coating the cartridges with a light film of wax.

Blish Principle….There is no doubt that this mechanism can be made to operate as described, provided the cartridge are lubricated, …. That this type of mechanism actually opens while there is still considerable pressure in the cartridge case is evident from the fact that the gun does not operate satisfactorily unless the cartridges are lubricated.

Thompson Sub-Machine Gun: … Owing to the low pressure involved in the pistol cartridge, it is not necessary to lubricate the case.

If you remember, the Pedersen rifle was a delayed blowback, and used wax lubrication on the cartridges. The Army, to say it mildly, hated it.




This Japanese Nambu had an oiler on top. The owner/operator had to keep the thing filled.










Oil, grease and wax were all very messy. Apparently the Russians came up with the fluted chamber idea first, and the Germans adopted a good idea when they saw it. Fluted chambers are such a good idea that the historical memory of greased, oiled, waxed cartridges has been forgotten by most. The US Army has forgotten this part of history and blamed oil for the problems created by cooking their 5.56 ammunition in an 160 F oven, and then firing the stuff in a SAWS, also at 160 F! The Army popped case heads, and blamed oily cases, not the high pressures!

Anyway, this is how flutes work.



One characteristic of the fluted chamber is that you have to keep the flutes clean and use ammunition that is relatively clean burning or the flutes get clogged up.

 

[ttarp]

One characteristic of the fluted chamber is that you have to keep the flutes clean and use ammunition that is relatively clean burning or the flutes get clogged up.

Other than PTRs run of improperly fluted chambers has anyone actually had dirty flutes cause malfunctions? I haven't had this issue with my PTR, and I've never bothered to clean the flutes once.

 

[Panzerschwein]

Love the replies guys, keep em coming!

That's really what these guns were designed for, to be a battle rifle. The rear sight only goes to 400 meters, which is actually beyond the range of most infantry combat. I bought this rifle not as a long-range gun to tuck behind a giant 20X scope while sitting on my butt at the range, but as a heavy-hitter no holds bar in your face slap yah mama silly bad ass battle rifle, a close range stopper, an AK-47 that grew a pair!!

I've got 400 rounds of Tulammo I might have to go shoot downrange tomorrow at the outdoor range!!

 

[mshootnit]

I knew the system, just not the acronym

 

[czhen]

Let see how it works for me, I put an order for 18" ptr 91 last week. To begin the 2016 with a semi 308

 

[Girodin]

This gun, to me, ... it's more like an AK-47 that fires 7.62x51mm NATO

I bought this rifle . . . as . . . an AK-47 that grew a pair!!

That is what this is:

This is an old picture and the gun is set up a bit differently now. I also have PTR 91 and some others. One day I'll have to do a write up or video comparing and contrasting them.

 

[briansmithwins]

I've always been interested in the HK roller delayed blowback weapons.

From an engineering standpoint the design has obvious advantages in theory: no gas system so you can make lighter and cheaper firearms and the weapon stays cleaner.

In practice the engineering and materials required to make the guns work make them as heavy and as expensive as gas operated guns, while dumping carbon in the receiver.

BSW

 

[Slamfire]

I've always been interested in the HK roller delayed blowback weapons.

From an engineering standpoint the design has obvious advantages in theory: no gas system so you can make lighter and cheaper firearms and the weapon stays cleaner.

There were a lot of historical delayed blowback weapons and I believe the primary reason was the higher cyclic rate of the things. I know the 20mm Oerlikon, which used greased ammunition, was at the time, the fastest single barrel 20mm of the period. The US wanted a 20mm that fired 1000 rounds per minute, the Oerlikon fired around 750 to 800 rpm. It was also light, around 100 lbs for the barrel and breech mechanism. The mount had to weigh more to control the recoil. Mechanisms with locked breeches take time to unlock. Rotating bolts have to rotate, for example. The roller bolt simply pops open when the pressures are low enough. A roller bolt was used in the MG42, I don't remember if it was a delayed blowback.

In practice the engineering and materials required to make the guns work make them as heavy and as expensive as gas operated guns, while dumping carbon in the receiver.

I do not disagree with the carbon in the receiver comment. My PTR91 is filthy. So much gas is venting from the case as it is extracted that the chamber and breech are sooted very quickly. I have read that the reasons the Germans put the delayed blow back roller bolts into production was cost: they were cheaper to make. I have read numbers about the number of man hours it takes to make a HK91, and it is low. It is far lower than the M14, FAL.

Ludwig Vorgrimler https://en.wikipedia.org/wiki/Ludwig_Vorgrimler and his team made the post war versions using lessons they learned from WW2. One very important lesson was that German Armies and their entire equipment had a tendency to disappear in Russia. I have read a statement to the effect that a production year's worth of equipment was lost when the Sixth German Army surrendered at Stalingrad. That was equipment the German state could have used for its new recruits. I am of the opinion that the HK91 (or G3) was designed to be built fast, and that the German design team decided it was more important to build rifles fast than repair them. The roller bolts I have handled, used sheet metal for the receivers. It is a lot easier to stamp out the receiver from sheet metal and train someone to weld them, than it is to create cutting tools, milling machines, and the highly skilled work force it takes to machine a receiver from a billet. There are some major structural parts in the roller that are not cheap steel, namely the bolt, and the trunnion. But again, from what I have read, it still took less time and manhours to make these mechanisms than any other competing design.

 

[briansmithwins]

MG42 uses a roller bolt, but the action is recoil powered, with an assist to speed things up using gas on the muzzle.

The problem with the HK design is you need decent steel to manufacture the bolt head, rollers, and locking peice. If you use crap steel those parts will be beaten into unusable shape before the first basic load goes through the gun.

Automating the manufacture of those critical pieces is certainly possible, but it's not ever going to be easy or cheap. My understanding is that to get the parts to be in spec the steel is roughly machined, heat treated, and then ground to the final shape and tolerance.

The rest of the rifle is fairly simple, even if it requires experienced welders.

BSW

 

[Panzerschwein]

All I know is this gun is VERY fun!!

I had fun at the indoor range the other day. There were several others there with pistols.

They were like "pop, pop, pop" and I was like:

BOOM!!! BOOM!!! BOOM!!!

I did feel a bit bad though. In the next lane over, there was a couple shooting a handgun and the woman unit looked over at my direction and said "I don't like that". I am sure it was extremely loud in the other lanes. But hey, they're the only range that allows rifles for miles that was open at the time.

 

[barnbwt]

Oil, grease and wax were all very messy

The Pedersen used a hard wax, something along the lines of cured carnuba, not paraffin. More like the poly coating seen on 5.7. Army just didn't want to switch ammo at the end of the day, since 276 basically exceeded all competition in testing. Didn't really matter ultimately, though, since a quality rifle was chosen.

The problem with the HK design is you need decent steel to manufacture the bolt head, rollers, and locking peice. If you use crap steel those parts will be beaten into unusable shape before the first basic load goes through the gun.

To be fair, the CETME/G3 design does require a lot more precision than most/any other designs to function right (bolt gap, chamber depth, locking piece angle, cocking tube gap, receiver straightness). Reproduceable enough via tooling (and quality control), but kind of a pain to develop or assemble, compared to something like a long-stroke gas action or anything with a barrel-extension lockup design (which the CETME sorta kinda is; the cocking system is what causes the most complexity imo)

TCB

 

[Slamfire]

The Pedersen used a hard wax, something along the lines of cured carnuba, not paraffin. More like the poly coating seen on 5.7

Pedersen was granted a patent for coating cartridges with wax, ceresin was his preferred wax, but he was patenting all wax coating in this patent claim:

PATENT OFFICE JOHN DOUGLAS PEDERSEN, OF SPRINGFIELD, MASSACHUSETTS, Nov. 4, 1930
http://www.google.com/patents/US1780566

In the preparation of cartridges having metal cases for storage and for use, it has been found desirable to apply to said metal case a relatively thin coating of some protective substance which will preserve said metal case for comparatively long periods of time against-deterioration, such as season cracking. In the present invention, the material for said coating has been so chosen as to perform the additional function of acting as a lubricant for the case of the cartridge, both for facilitating introduction into the chamber of the gun and the extraction thereof after firing. The most suitable wax which I have found for this purpose and which I at present prefer is ceresin, a refined product of ozokerite; but I wish it to be understood that other waxes having similar qualities may exist which might serve equally well. Some of the desirable features of ceresin are that it is hard and non-tacky at ordinary temperatures having a melting point somewhere between 140 and 176 Fahrenheit. It is smooth and glassy when hard and does not gather dirt or dust. However, when the ceresin on the cartridges is melted in the chamber of a gun, it becomes a lubricant.

Other lubricating waxes have been employed for coating cartridges, and the method most generally pursued for applying said coating to the cartridge case has been to prepare a heated bath of a solution of the wax in a suitable solvent, dip the cartridges therein so that a film of the solution will adhere thereto, and finally withdraw the cartridges to permit the solvent to evaporate from the coating film. This former process is comparatively slow and has been found lacking in several important respects.

As for the polymer coat on the 5.7 rounds, I wish I knew the composition of the coating. I have picked up fired cases at the range and they don't feel all that slick. I am of the opinion the "polymer" term was picked by the advertising bureau for two reasons. The first is to protect their proprietary coating technology. The second is to prevent the typical ape **** reaction of Americans who have been taught to believe that lubricated cases will cause their fire arm to blow up. You read this all the time: oil or grease on the cartridge dangerously raises pressures and bolt thrust". This is an Army coverup of long standing, recently updated in 2010, and one that the American shooting public believes to their core. Incidentally, grease, oil, wax, teflon are all "polymers".

 

[Don357]

I too love my roller locked rifles. I have a Century CETME that I have had no problems with. I had another one awhile back but traded it for a PSL. Didn't like it as much as the CETME so l sold it and made $700 profit above the price I paid for the CETME. And bought another CETME. Ordered some wood furniture for it that should be in today. But with the price of ammo being what it is, I don't shoot it much. I would like to have a Century C93 to go along with it, but l guess I'll have to settle for my new SKS para until I can find and fund a C93.

 

[bfoosh006]

Very nice ! I have always wanted one... some day !

You might find this video interesting....just for giggles...

https://www.youtube.com/watch?v=Pe-ViHSG2xg

 

[Nature Boy]

...the woman unit looked over at my direction and said "I don't like that"....

Was she talking about you or the rifle?

I don't have that problem, especially when I'm shooting the M1A/M14. Women seem it be attracted to it's innate power, flowing lines and masculine beauty.

 

[MachIVshooter]

The CETME pattern are nice looking rifles. Unfortunately, the balance and recoil impulse kind of offset the aesthetic appeal to me. Much prefer the AR and FAL, followed by the M1A. G3 ranks above SCAR-17 for me, though!

I do own a CETME, and not planning to part with it. But my .308 AR and FAL Para see infinitely more range time.

just curious, but has a more awesome weapon than the HK91/G3 family of rifles ever been made?.

Many.

The only appeal of that "family" to me is that a registered FA fire control pack can be used in host weapons from the MP5 to the HK21/23. 'Course, at $30K+, those are a bit out of most of our price range.

 

[M1key]

Review from a fanboy, complete with warts:

http://mountainpreparedness.blogspot.com/2011/04/personal-critical-review-of-firearms_2941.html

Note comments about receiver dents. A healthy one on or near the charging handle can cause it to bind and bingo you are out of the fight. A pretty rare occurrence, but it has happened.

The rest of the review mirrors my experiences. Also those rollers need to be oiled to operate reliably. Wet climates will rust them if left unattended (i.e. Central American jungles).

The HK/PTR is NOT as reliable as a Kalashnikov. But, YMMV.



M

 

[stubbicatt]

No matter the design, there will be issues with filth. What is interesting to me is how the blast of firing residue into the trunnion in the G3 doesn't stop the rifle. The design just blows through that filth and the action keeps running. So long as maintained properly, the G3 is a very reliable rifle. Grease and oil is used sparingly, and the action will run when dry, due to linear force on the bolt. Rust? You would have to park that rifle in caustic material for some time to lock up that action due to rust. I seriously doubt that atmospheric moisture will rust the action shut. The bolt head and trunnion are buried deep inside the receiver to prevent ingress of moisture or dirt. Consider that if you disassemble once a day, wipe down with thin oil and reassemble, any surface rust can be mitigated. And *if* you had some surface rust on the roller/trunnion interface, sufficient to impair opening the action, one round would blast through that stuff like right now.

From my perspective, it is a great rifle, and probably the best infantry rifle of its era, and a design overall which was ahead of its time. I mean, have you seen the period accessories for the FAL for mounting optics? Scarcely better than those cheesy Chinese top cover mounts for AKs back in the 80s. You lose zero on your optic when they are removed and replaced, and sometimes while in use. The M14 optic mounts from the era? Holy Moses those were a retchid assembly of Rube Goldberg contraptions. Look at the G3 claw mount. Simple, reliable, readily removable and easy to install AND the optic stays zeroed. Every time. This is because the rifle and optics interface were designed together, not an afterthought. Not until the recent advent of Pic rail has there been a better system. And the claw dates from the 50s. G3 has a free floating barrel as a standard design element. Even now the as issued M4 may not have a floated barrel.

The magazine is without doubt the most robust magazine design of the big 3. The magazine box surrounding the feed lips is easily capable of withstanding impact due to dropping without distorting the feed lips. Can't say that about the M14 or FAL mags.

There are drawbacks. The location of the safety/selector could have been improved, and the long reach to the cocking handle could have been improved.

Fellas, shoot which ever rifles you like. They are all pretty good. For me, after having owned and shot NATO rifles over the years, I have settled on this design as the best choice. You are free to choose what you like.

 

[M1key]

You might "blast" the rollers loose if you happen to have a round in the chamber. If not you are out of action.

Reportedly the Contras had issues due to poor maintenance practices. This from a fellow who claimed to be an armorer for them.

Keep the rollers clean and oiled if you live in humid climate and you shouldn't have a problem.

M