Velocity/Energy of bolts v. semis(30'06)


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Col. Plink
July 15, 2009, 11:02 AM
Hey y'all,

I have a bolt action 30'06 and a Garand, and wondered how much dropoff in velocity and energy there is between the two shooting the same ammo (not that I am, CMP says new ammo up to 180grain is OK but I'm sticking to surplus 150 except a few pops).

I know that semis use some energy to cycle the round, perhaps more so with a gas-tube action? Just wondering what the commonsense opinion is. Thanks!

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MTMilitiaman
July 15, 2009, 11:38 AM
I would and do expect 100 to 200 fps drop off in velocity from my M1A with its 22 inch stainless, medium contour barrel verses a bolt action. For example, I expect around 2700 fps from a standard 147 gr ball round verses about 2900 from a good bolt gun, or 2500 fps for a 175 gr SMK, verses closer to 2700 for a bolt gun.

When reloading for gas guns, esp the M1/M14/M1A, pressure curve and port pressure are at least as important as peak pressure. Powders must be kept within a certain burn range to insure that both peak pressure and port pressure are within spec. Powders that burn too fast have a tendency to spike and approach allowable peak pressures quickly, while possibly not allowing enough port pressure to reliably cycle the action. Powders that burn too slow, including many that are used in bolt guns, usually approach peak pressure more slowly. This allows for better use of longer barrels, but can result in port pressures that are too high, despite having peak pressures well within allowable levels. This can cause violent cycling problems that at the least tend to damage brass. In more extreme cases, you can bend op rods, crack receivers, ect. I remember an account on another forum of a man shooting Hornady Light Mag out of his Garand. A fine rifle became a grenade. The guy ended up with significant damage to his hands and face, but lived to fight another day. His rifle wasn't so lucky.

I would expect most surplus ammo in the respective calibers to be acceptable in their applicable gas guns, and I usually trust commercially available FMJ ammunition approximating the weight and velocity of standard ball loads to be acceptable as well. For example, I've shot hundreds of rounds of Win, American Eagle, and S&B 147 to 150 gr FMJs out of my M1A without issue. I would also expect specialized defensive and commercially available match ammunition, such as Hornady TAP or Federal Gold Medal, to be okay, due to the popularity of these systems for those applications. All other commercially available ammunition, including all hunting ammunition, is met with skepticism, regardless of its projectile weight or stated velocity.

BTW, I don't reload for my M1A, yet. I have picked up 1000 pieces of milsurp brass in preparation for doing so, and have been doing some reading. You might find this article, copy and pasted from Fulton Armory's website (M1 Garand Frequently Asked Questions), helpful:

http://www.fulton-armory.com/
On Reloading for US Gas Operated Service Rifles
by Clint McKee, with additional thoughts from Walt Kuleck & R.J. Suckow

Hi, Clint! Why don't you condone reloading for the US Gas Operated Service Rifles?

This should not be an honest surprise for anyone. Forgive my ignorance, but what firearms manufacturer recommends reloads, or warrants the product for such? In all the world? One might reasonably ask why this is so. Well, there's all the obvious stuff. Then, there's destruction, maiming and death.

Most of you are vastly more educated than I re reloading, and I apologise for my ignorance, and, for dissapointing you with my very unpopular position. Yes, it hurts business, and has even been the catalyst for the "trashing" of my business and myself personally on the Internet. So, why in the world don't I just "get with it" and give you guys and gals the "load of the month" (there have been so many over the years), and make even more money and then join the ranks of your "worth" class?

Because I do not want you to get hurt. If I do anything re: this 20 year position, I at least alarm the thoughtful ones, and maybe, just maybe, it'll save you from something you never thought possible, no matter what safe and serviceable rifle you may be shooting.

Always remember it's 50,000 PSI only a few inches from your face.

Be prepared, as I am, for the torrent of "reloading is safe", and "I've been reloading for 20 years and never had a prob", and "can't win witout reloads", and "only an idiot would say such things", and ........ ???

Facts:

* A man I know well in the mil rifle business (a supplier), was sounding a little down on the phone a few years ago, so I asked what was the matter. He answered, "I lost my eye.""—Ruger Mini-14, reloads.
* A man who I know well who has been building NM Service Rifles and Match rifles for 25 years blew up a customer rifle while test firing. Face peppered with brass, blood everywhere, no permanent damage, thank goodness. Reloads. His reloads. BTW, this guy holds more records than all of you on this forum, times a few factors.
* A man in the firearms business, a shooter, a person whose life was firerams, for over 20 years, was killed recently. Reloads. His reloads.
* We have a bunch of large rifles that fit into small boxes (rifles we did not build, BTW), because of reloads.
* Friend of a friend who has been reloading for decades, was unclogging primers in his primer feeder when the stack exploded. He's a man wanting several fingers and a thumb.
* DCM Garands in perfect mechanical condition, destroyed due to reloads.
* Military match M16's disintegrated, due to reloads.

And so it goes, and goes, and goes. This stuff happens all the time. But, like that accident we all heard of, we just know we would not have done such a dumb thing. The psychological libraries were filled with this proof decades ago. Sadly, "we" believe things will be different for "us." It's the way we humans are constructed. For those that have been in this business for more than a few years, it's deja vous all over again, and again, and...Oh, and remember, it takes only ONE catastrophic failure over your entire life to really ruin your day. So spare me the "I've been doing this for... years," "I'm a tool & die maker", ...

If you insist on reloading:

* NO firearms company should fix your broken rifle, or, broken body. So please, do not expect, nor ask them to. Some have extorted awards not deserved, due to the litigious nature of the American culture.
* Get ALL the gauges (Cartridge overall length, headspace of case, length of case). If you do not have these or know what this means, you are in very dangerous waters.
* When you use the Stoney Point Gauge (or similiar gauges) to determine actual cartridge OAL, remember that you must measure EVERY bullet for each cartridge, as the bullets DO vary substantially from one another, even in the same box! And stay about 20 thou off the lands. Closer can be safe, but begs for tolerance stacks, and, human errors, and offers NO accuracy improvement. This has been proven over and over, and over, ...for the past 40 years.
* NEVER assume "resized" brass is properly resized, and NEVER assume new brass is properly resized. These often are NOT. Use your gauges to verify.
* NEVER assume your sizing dies properly size your cases, for often they do NOT, and often need to be adjusted as they come from the factory.
* Keep in mind that there are lots of powders that are not appropriate, and, many that could destroy your rifle, kill or mame you.
* Keep in mind that you are loading for a military rifle, with a free floating firing pin (see the Fulton Armory FAQ articles on the subject) and designed, most likely, by people more knowledgeable than you and I. Understand the well documented historical record re: catastrophic failures over the past 66 years from slam fires.

--Clint McKee

I'm convinced that only rarely do we hear of rifle failures induced by reloads. I have a couple of AR blowups on file I'll bet you never heard of. Nobody wants to broadcast their mistakes.

Now, it may be that since every shooter drank milk as a child, milk causes rifle blowups. Correlation is not causation. It's just spooky when every rifle failure that comes into Fulton Armory (and there have been more than a few, over the years) can be associated with (note the wording, not Attributed To) reloads. You'd think at least one would come in that blew up with factory or USGI ammo in twenty years.

Just food for thought, no intent to convince anyone or condemn anyone. Be careful out there.

--Walt Kuleck

Maybe I'm wrong here guys,but I think you're missing the gist of Clint's position, especially in regard to the reasons for reloads being potentially dangerous.

Most military autoloaders, especially rifles like the Garand, are far stronger than their bolt counterparts. What blows a Springfield or Enfield makes a Garand hiccup, in terms of general ability to handle pressure. The cause isn't pressures, but out of battery firing.

Reread Clint's response. Little is said about weighing charges, this is general reloader responsibility. What is mentioned, conspicuously, and several times, are case length, length overall of loaded rounds, etc., hence the references to the Stoney Point gauge and cartridge headspace tolerancing. Expecting all bullets to have the same ogival profile can get you in trouble, even from the same box. I've made draw dies for a friends bullet swaging, ain't no way all the jackets are drawn the same from the same die, hence different ogival profiles, hence different LOA's, hence one hits the rifling a bit soon in that "really accurate load" and BOOM! Please note what Clint mentioned about bullet seating to lands depth.

Bottom line is, it isn't the pressures. It's the seating depth, cartridge headspace, primer seating, primer cup resistance, neck thickness, and cartridge basal sizing that will get you killed. This beyond the ken of what metellurgical condition the brass is currently in after sizing. That's why you better have your head on straight when you load for an autoloader.

Thanks for tolerating the rant.

--R.J. Suckow

Note that I am still going to reload for my M1A at some point. But this article was eye-opening for me, and so acknowledging my limits as an amateur reloader, I am going to wait until I have more experience, and all the necessary tools, dies, and measuring instruments. My dad also has a tendency to load things "hot," as he is a fan of milking every single FPS he can from every single firearm and load he shoots. This isn't a practice I endorse or encourage, so he won't be loading for my M1A, ever.

Here's a guy with some experience on the issue that isn't so pessemistic about reloading for gas guns as a whole, while still acknowledging the inherent associated risks involved. Note that while the article is about loading for the M14, I would expect much or most of it to be applicable to the M1 Garand as well:

http://www.zediker.com/downloads/m14.html

USSR
July 15, 2009, 01:12 PM
I have a bolt action 30'06 and a Garand, and wondered how much dropoff in velocity and energy there is between the two shooting the same ammo (not that I am, CMP says new ammo up to 180grain is OK but I'm sticking to surplus 150 except a few pops).

There is simply no way to know, unless you run it thru your chronograph. Example: I have two .30-06 match rifles. Both have 26" barrels. With the same load, one gets 2875fps, while other does 2950fps. However, assuming your bolt action rifle is a factory rifle with the same 24" barrel length that the Garand has, and you are using Garand suitable ammo in both, you are unlikely to see much more than 100fps difference between the two. But this brings on the question, why seriously download your boltgun by shooting the Garand ammo in it? The .30-06 boltgun is capable of much greater performance when freed from the port pressure constrained Garand ammo.

Don

Col. Plink
July 15, 2009, 02:29 PM
Right; not gonna bother shooting my surplus ammo in the bolt action, it has its own food supply. It kicks like moonshine, though, even with a Limbsaver. A nice buy at $250, though (WalMart, Mossberg 100ATR synthetic stock). Light, accurate, dangerous on both ends!

Jim Watson
July 15, 2009, 02:48 PM
The gas port on a Garand is so near the muzzle, I doubt you would be able to detect a difference. As USSR describes, there is enough difference between individual barrels to mask the effect of gas diverted to auto operation.

If you really wanted to know, I guess you could get one of those adjustable gas plugs or blocks for an auto so you could compare the same ammunition in the same barrel with the port completely cut off versus open for autoloading.

Vern Humphrey
July 15, 2009, 05:08 PM
The gas port on a Garand is so near the muzzle, I doubt you would be able to detect a difference. As USSR describes, there is enough difference between individual barrels to mask the effect of gas diverted to auto operation.
Absolutely 100% right.

The muzzle velocity of the Garand is governed by the loads for which it was designed -- which are around 200 fps below what we come to expect in modern ammo, loaded with slower burning powers -- not by loss of gas pressure to cycle the action.

rcmodel
July 15, 2009, 07:10 PM
It can be tested in the same exact barrel in any military rifle with a gas shut-off for firing rifle grenades.

Tests I have seen using the M-14 show no measurable difference in velocity at all with the gas system shut off.

The bullets are long gone down range before the action even begins to cycle.

rc

Vern Humphrey
July 15, 2009, 07:15 PM
You can also shoot the M1 wth the gas cylinder removed, if you're curious about possible muzzle velocity loss.

The M14, with it's internally vented short-stroke gas piston uses very little gas, in any case.

Gaiudo
July 15, 2009, 07:51 PM
That article from Clint..... another example of him, while still uneducated on the process, making gross claims. This is kinda par for the course with him. Regarding shooting warnings: you will get every malfunction listed above from factory ammo as well. Wear eyepro every time, and be careful.

stubbicatt
July 16, 2009, 11:23 AM
Vern Humphrey: If you removed the gas cylinder from a Garand, you would have done nothing to prevent gas from diverting through the barrel port, would you?

Vern Humphrey
July 16, 2009, 11:33 AM
Vern Humphrey: If you removed the gas cylinder from a Garand, you would have done nothing to prevent gas from diverting through the barrel port, would you?
Take a look at how close the gas port is to the muzzle. By the time the base of the bullet uncovers the gas port, the nose is nearly at the muzzle.

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