March 11, 2010, 07:15 AM | #1 |
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Neck sizing for Garand?
I mentioned in post yesterday that I wanted to try a neck size die for my 30-06 rounds for a Garand. The issue was that I was breaking pins in a de-capping die but one response was that I'd be sorry if I used the neck die for an auto loader. I was afraid that they might get too tight to feed but he got me thinking... Will they get stuck and not eject? Maybe saving a few bucks by getting a few more rounds out of the brass isn't going to be worth it in this case.
I read somewhere that as long as the round was fired in the same chamber that it was shot in previously that they should be fine but I don't know if they were referring only to a bolt action. I never reloaded for an automatic other than straight walled pistol. Is it worth trying or is this totally the wrong application for neck sizing? Thanks! David |
March 11, 2010, 07:28 AM | #2 |
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Haven't tried it and I wouldn't
I have read enough of these over the past few years to completely persuade me from even trying to neck size for an autoloader. The physics and logic behind all of the explanations makes perfect sense so I have never tried it. I understand how it sounds tempting based on the fireforming theory, but autoloaders really expand the cases and I don't know that it would work. If you try it and it works, let us all know.
Also, how much accuracy do you want. My autoloaders are well within 1 inch groups, 1.5 if I'm not shooting well that day. I don't know that neck sizing will only will really get me much better than that. For the extra one millionth of a second that it takes to full length resize vs. neck sizing, I personally see no advantage. However, for bolt action guns, I do neck size and see a noticeable difference. |
March 11, 2010, 07:47 AM | #3 |
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http://www.exteriorballistics.com/re...sgunreload.cfm
And This. http://www.zediker.com/downloads/14_loading.pdf For one, the M14 has about the quickest operation of any auto-loading rifle — so much so that the bolt can unlock before the case has fully retracted from its expanded dimensions. We’re talking about milliseconds, but that’s all we have devoted to the entire process. The net result is that some amount of additional expansion frequentlyoccurs in a case fired through an M14. Compounding this condition is that LC brass is liable not to contract as readily as other cases fired in other rifles. It’s very, very (comparatively) hot and getting jerked on by an extractor, and most seem to think this is responsible for a lot of the additional measured case growth. Don’t be fooled into thinking that brass from an M14 “fire formed” to fit the chamber; it may well have “fire deformed.” A spent case from a 14 will often have the shoulder blown farther forward than chamber specs should allow, and may also exhibit more case head expansion than it “should.” I've found this over sized fired brass in my Browning BARs, Mini-30, Rem 742-308, Ar-15 6.5 Grendel and AR-15 223. Not so much in the 223, but it's still there.. I have no doubt that this will occur in your Garand as well. Last edited by steve4102; March 11, 2010 at 08:33 AM. |
March 11, 2010, 08:27 AM | #4 |
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I did some experimenting with neck sizing for my M1 Garand some years ago. I discovered that neck sized rounds were difficult to load into the eight round enbloc clips. The clips with the neck sized rounds were difficult to load into the rifle also. Therefore, I ceased the practice of neck sizing for my M1.
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March 11, 2010, 08:44 AM | #5 |
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My dad did it for years
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March 11, 2010, 09:47 AM | #6 |
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I've never tried it with mine. Lots of people swear you need to not only full-length size for the M1, but that you also need to use a small base die, and that's certainly not necessary with my M1. I suspect it depends on the rifle, so if you're curious you could go ahead and buy a neck sizer and give it a try. If it doesn't work out and you have no other need for a neck sizer in .30-06, you're not going to have any trouble selling it to someone else.
There are lots of "conventional wisdom" concepts out there that, while having a reasonable and factual basis, often prove false in many cases. I say just give it a try and see if it works in your rifle. Mike |
March 11, 2010, 02:13 PM | #7 |
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If you're determined to do this, a more productive approach may be to set your FL sizing die using an RCBS Precision Mic. Used with care these are supposed to help limit case stretching, thereby increasing case life. Several on the CMP Forum claim to have used it with success.
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March 11, 2010, 03:06 PM | #8 |
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It can be done, but there are problems. First, even in bolt rifles, neck-sized-only rounds often will not feed from a magazine without catching. They are strictly for single-loading if feed reliability matters to you?
Second, the floating firing pins in military rifles like the M1 can cause a slamfire if the cartridge hesitates to enter the chamber. Slamfires are not usually damaging to the Garand because, if the safety bridge is in good shape, the bolt should be at least partly closed before the firing pin can go far enough forward to initiate one. But, if the gun has a bent safety bridge or is otherwise not in perfect shape, they can happen early enough in the cartridge entry to the chamber that they can cause damage. A member on another board who used to work for Aberdeen Proving Grounds said he once had to investigate a machine gun slamfire that killed the man to the right of the ejection port with metal fragments blown out and off the bolt face. That's pretty unusual, but it tells you that slamfires are not something to take lightly. The most common cause is a high primer, but anything that makes the round hard to chamber can cause them too. The more times a case is neck-sized and fired, the more tight fit becomes an issue. The case gradually fills out tighter in the chamber with each firing. So, eventually neck sized cases stop fitting the chamber without a lot of bolt torque and need to go through a full length die for a load cycle. Alternately, they may be used with a Redding body die (which sizes the body but leaves the neck alone) or something similar to bump the shoulder of the case back a thousandth or two. The case stretching problem from semi-auto extraction can be solved in the Garand by using a vented gas cylinder plug. These are plugs that vent a portion of cylinder gas from the gas port forward rather than applying it all to the piston head on the op-rod. They are adjustable so you can set the op-rod to barely eject the round or even to prevent semi-auto function altogether, and just operate it manually. With single-loading, that would work fine. Even setting them so the ejection merely drops cases right next to you will greatly reduce extraction force. These devices are available from Brownells, among others.
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March 11, 2010, 05:30 PM | #9 |
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This all sounds too difficult and risky just to try to get a couple extra reload cycles out of the cases. I'm just going to go back to full length sizing and be done with it. Cases are a pretty insignificant cost factor anyway. I'll just use the neck die for my bolt action gun.
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March 11, 2010, 07:09 PM | #10 | |
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Neck sizing is a great way to induce an out of battery slamfire.
Quote:
Nada? |
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March 12, 2010, 11:36 AM | #11 |
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Excellent point Slamfire. However, please don't claim that I'm intentionally giving risky advice though--I just never thought about the possibility of a slamfire.
As a wise man said, never attribute to malice that which can be easily explained by stupidity. Mike |
March 12, 2010, 09:09 PM | #12 | ||
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Quote:
First slamfire, standard sizing die and Federal primers. Second slamfire, Bonaza match sizing die, reamed to depth pockets, and Federal primers. So when I read statements like this: Quote:
"Conventional wisdom" is and was that primer sensitivity has nothing to do with slamfires. "Conventional Wisdom" is and was that oversized cases have nothing to do with out of battery slamfires. "Conventional Wisdom" is and was that only high primers cause slamfires. It took the second slamfire to convince me that "Conventional Wisdom" is all bunk and it was not something that I did. |
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March 12, 2010, 09:27 PM | #13 |
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Interesting story. I've always heard conventional wisdom is that slamfires are usually caused by high primers, but you are quite correct that it's not the only mechanism. Glad that bad one didn't kill you. It sure seems like it tried.
I think one issue with the Garand has always been that the safety bridge and firing pin and bolt length all have to be right, yet few individual owners have the gauges to check. They buy and swap around parts with abandon. I've also never quite trusted the extra power op-rod springs not to shove the bolt home too hard. Maybe not so likely a problem with feeding from the en bloc clip, but more potential for a slamfire single-loading where there is no cartridge or follower drag on the round to slow the bolt a little.
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March 13, 2010, 04:48 PM | #14 |
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I don’t believe the receiver bridge works as promoted by “conventional wisdom”, or ever has. My evidence is based on the numerous slamfires that have occurred with military ammunition. And this, the original round Garand firing pin.
This firing pin is so rare that I have never seen one, only this picture. It is so rare that Orion 7 sold their lot at $100.00 a firing pin. This firing pin is so old that the memory of why it was needed is gone. The Army modified the early round firing pin to the scalloped version that we are all familiar. The round firing pin would be stronger and easier to make. So why did the Army add cost to the Garand: Slamfires. They had to lighten the Garand firing to reduce the kinetic energy of the firing pin as it bounced off the primer. This is something they did for the M16 and that account is in the book “The Black Rifle: An M16 Retrospective” http://www.amazon.com/Black-Rifle-Re.../dp/0889351155 If early Garands were slamfiring so often that the Army had to modify their firing pin, and this with new production Garands, then the receiver bridge was ineffective and is ineffective in preventing slamfires. I wanted to know just when the receiver bridge stops the forward movement of the firing pin. I moved the bolts on the receivers pictured below until the firing pin tang touched the receiver bridge. Incidentally these are CMP receivers with the correct HRA and IHC parts. Based on the original finish wear, these receivers are barely used. The firing pin can rebound unobstructed the entire bolt travel up to this point on these receivers. If you look, cam down is probably in thousandths of an inch forward, not tenths of an inch. I am confident that the receiver bridge only supports the bottom of the bolt during lockup. As a firing pin block, it is too little, too late. HRA receiver original finish IHC Receiver original finish |
March 13, 2010, 11:12 PM | #15 |
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Slamfire, this makes for fascinating reading for someone like me who knows very little about slamfires. I very much appreciate you taking the time to post such good detail.
Mike |
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