Dies for bolt vs semi-auto.

[knowledge_is_power]

I'm a nooby to reloading. When I first bought everything I figured that my .308 die would be just as good for my Rem 700 as for my M1A. Well, I was told that's not in fact true and that I should get a die that's for semi-autos. What truth is there to this? As well, if it is true, what are all the little details that I should know about. Thanks in advance!

[dab102999]

Dies will work for all of them. Only thing is if you have neck size dies only would be best to keep brass with gun that shot it.

[jimkim]

What your friend is talking about are small base dies. You may, or may not need small base dies. It depends on your M1A's chamber. Look under dies in FAQ'S. It should explain it. http://www.rcbs.com/guide/#faq

I'd suggest trying the dies you have first. If they don't work, buy a small base sizing die.

[Slamfire]

There are those who use standard based dies for gas guns and get away with it for a time, but sloppy reloading practices will always catch up in time for gas gun shooters.

I highly recommend using small base dies and setting them up with case gages. You will never get the proper cartridge headspace following the instructions that come with the die. The old “to the shell head and add a quarter turn”. You need case gages and you should simply size to gage minimum.





There are practical safety reasons for this. The Garand/M1a/M1 Carbine/Mini 14 all share a similar bolt mechanism. The firing pin is only retracted on cam down. Until that last .00?” where the receiver bridge touches the firing pin, the firing pin is free to wack the primer. All of these actions have had slamfires, in battery, and out of battery. You want a case that drops in the chamber without any resistance to closure. A tight case or a long case, the bolt has to stop and crunch fit that round to the chamber. In that period that free floating firing pin is rebounding off the back of the primer. If the lugs are not engaged, you run the risk of an out of battery slamfire.

These mechanisms will still slamfire in battery given a sensitive primer so always avoid primers that are advertized as “more sensitive”. That includes all Federal primers, all match or benchrest primers. Given a milspec primer I believe the slamfire probability is about 1:64 million. This is the slamfire probability William Davis calculated was acceptable for the M16, so I believe this is what they were looking for in a M14 with Mil Spec primers. I heard the chances of dying of snake bite in the US is about 1:50 million, about five people die of snake bites in the US. So your chances of a slamfire with good mil spec primer are about the same as dying from a snake bite. With sensitive commercial primers William Davis calculated a 1:9000 chance of a slamfire in a M16, don’t see any reason why a M14 mechanism would be that much different. Two primers on the market are advertized as mil spec: CCI #34’s and Tula7.62. These are your first choice of primer for these mechanisms.

Here is an example of a minimum headspace chamber, a fat case, and benchrest primers.


http://www.snipercountry.com/HotTips/Slamfire.htm

Torsten <[email protected]>
Germany - Thursday, February 11, 1999 at 08:50:34 (ZULU)

M14/M305: I looked at my personal "slam fire" and here is what happend. I have a NM TRW bolt in a Norinco M305, I shot realoads that were made for and previously shot out of my G-3, the local hunting clubs range I shoot at does not allow magazines, or slings,(go figure) to be used.

My conclusion: headspace is really on the tight side after lapping the bolt in, the realoads even though full sized still had the H&K flutes on them and may not have seated all the way in the chamber, I used thin CCI Bench rest primers in tight PMC brass pockets that were seated real flat, and I had to load the round into the chamber and then close the bolt onto it which causes a higher bolt speed forward that if it would feed a round out of the mag. BAM, Slammfire !

Clearly not the Guns fault, but operator failure. The only damage that I found so far is a small deformation in the OP rod cam were the bolts giudewheel runs. I´ll take her to the range again and fire some factory FMJ out of a Magazine to see if the little deburring I did solved the problem.

The straight wall, no neck .308 case is in a special glass case I reserved for little reminders. This case also includes a 1" truck wheel nut and bolt that I stripped. It was stamped L for left hand thread, but in the heat of battle, what do I know.
"Ende"

Even if you don’t have a slamfire with oversized, fat cases, cases sized in standard dies will eventually cause problems. Mike Venturino is a gun writer who for decades has been claiming you don’t need to use small base dies. Then, in the July 2012 Guns Magazine, he is testing a M1a and AR10 and both of the rifles are jamming with his reloads. The rounds were so tight that he could not get the bolts in battery to shoot them out and he could not manually extract them. He resorted to beating the bolts open with scrap lumber. Ha, Ha. Even Gunwriters have to eat crow at some point.

So, this is what I recommend:

Size all your cases with small base dies. Use a good lube, such as RCBS water soluble or Imperial sizing wax. Spray on lubes will stick a case in a small base die.

Set up your dies with a case gage and size to gage minimum.

Trim to length.

Clean your primer pockets, I recommend reaming pockets to depth.

Always prime by hand and verify that all primers are below the case head. You do not want high primers as they could cause a slamfire by themselves.

[Jimro]

If your rifle doesn't need small base dies, don't use them. In my experience anything with a factory chamber doesn't need small base dies (although there have been reports from folks with different experiences).

For an autoloader 4 reloads and chuck 'em is a good idea to follow for brass. Autoloaders are hard on brass.

I full length size, trim to minimum with the first reload, then just full length size for the remaining three reloads. This is the method for a lot of high power shooters.

Jimro