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Discussion Starter · #1 ·
I'm trying to reload a few rounds for my M1a and thought I would try just doing a neck resizing instead of a full length. After resizing, I always check case headspace with a wilson case headspace gauge. All of the resized rounds were too long. I checked a few once fired cases and they also were too long.

I had dropped my rifle off at the gunsmith for rebedding and he checked the headspace while there with a no-go gauge. Bolt did NOT close and he said I was good to go. Should I email him to see if it's possible to get a actual measurement on the headspace?

Also, would it be safe to load rounds using only the neck resizing? I assume they will chamber fine since they came out of the chamber at that size.
 

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Neck sizing dies are not designed to change any part of the case except the neck's diameter. They are not designed to push the shoulder back at all.

After firing, the case will expand and swell and depending on op rod/bolt dwell time (how long it takes for the bolt to start to open) and a few other things your cases can expend in length enough to exceed the SAAMI headspace specification. This is why, at a minimum, full length resizing dies are recommended. Some rifles, with tight chambers, require a small base die but that is the exception.

Full length and small base dies can be adjusted to push the shoulder back (bump) a few thousandths of an inch. The small base die also reduces the diameter of the base of the case.

As an aside, are you greasing your cases or just leaving them greasy from the resizing step. Some people recommend applying a thin coat of grease or oil to the case before firing; I don't and neither does Springfield or the military. While the lubricant can increase case life, by allowing the case to move toward the bolt face upon firing and thereby reducing the stretch at the base of the case, that puts more pressure on the bolt lugs and it forces more stretch on the other end of the case...the shoulder area.
 

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Would suggest you take a look at something that gives you a numerical value as to just what size your cases are after firing. In short, use of calipers to provide length of case from base to shoulder area, datum line on shoulder. I use a Moe's gauge or the Sinclair kit which does the same thing(RCBS offers similar tool.) Measure new unfired case vs fired case in your gun and you gain a picture of the amount of growth of the case upon firing. Then you can set your full length die to bump shoulder back to something less than reading from fired case to insure chambering. Compared to a bolt gun, the M1A's/M14's are "case eaters" for there is a whole lot of action taking place upon firing. Round is jammed into receiver, fired, yanked back out and that brass sees a lot of violent action. Reason for most not using brass more than a few times, say three or four at most to avoid case separation. The gun does not know that a partial case is in the chamber and it's going to send another one right behind it. As well put in above post, you do not want any grease/oil on brass or chamber for that can lead to big pressure spikes and problems. Just a suggestion.
 

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The M14/M1A fired brass NEEDS to be FULL LENGTH re-sized. The shoulder needs to be pushed back to within spec.

What MFD and RAMAC said above is true. The brass gets stretched because the action is yanking the brass out of the chamber while the brass is still expanded from the shot.

Download this, then read it. It is considered the bible for reloading practices for the M1A and the M1 Garand.

 

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You will not find a manual or a die manufacturer that says neck sizing for semi-auto's is safe. If I remember right, back in the 90's we had a guy that stopped in here and said he did it all the time. So that's one guy in several hundred.

Your smith would need a full set of headspace gages to give you a numerical measurement. I don't think it'd be all that useful; it changes over time and doesn't readily translate into what you should do with your fired brass.

Set your FL die with a case gage or comparator using the instructions.
 

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It's not unusual for M1A brass to be too long to go back into the chamber it just came out of. That's because the bolt starts twisting and yanking on it before the pressure has fully gone away and allowed the brass to let go of the chamber walls. You end up with not enough headspace to re-chamber the case - the base to shoulder measurement on the brass is longer than the bolt face to shoulder measurement of the chamber. This is also the reason the M1A eats brass faster than just about any other gun.

The brass must be f-l resized before it can be used again.
 

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Discussion Starter · #8 ·
I remember now. I've read zediker's guide many a time, just forgot that part. Guess I'll do a FL resize now.
 

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RAMMAC,

Forster Neck Bushing Dies will push the shoulder back. I use mine (without the bushing insert) to push back the shoulder on full length sized cases that still don't have enough headspace clearance.

JD
 

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RAMMAC,

Forster Neck Bushing Dies will push the shoulder back. I use mine (without the bushing insert) to push back the shoulder on full length sized cases that still don't have enough headspace clearance.

JD
That's because the Forster "Bushing Bump Neck Sizing Die" isn't a true neck sizing die. They use the word "Bump" in the name of the die because it is designed to move the shoulder in addition to the neck sizing capability.

http://www.forsterproducts.com/store.asp?pid=27654

This die is a combination of the Redding S type die that uses bushings to adjust the neck diameter and a standard full length die.
 

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I apologize if this is off topic with regards to the OP.

Is there any kind of a rough, rule-of-thumb ratio of case expansion (after firing) to case length prior to firing that can tell you if you need to adjust your full length die one way or the other to bump the shoulder back more/less?

In other words, if your cases measure for example 2.005 prior to reloading and then measure out to 2.0XX, is there a certain ration of:

(2.0XX - 2.005) / 2.005

that can indicate insufficient or excessive case headspace? I don't literally mean running mathematical equation above, but just if anybody here has actually found a deviation amount that is a red flag on headspace issues.

I know that I probably should buy an RCBS Precision MIC gauge, but I don't really want to. GI1 I never really worried about this particular when reloading for my M1's, but I want to obviously get the most out of my brass life and also wring out the absolute most accuracy from my new M14 as possible.
 
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