How to resize headspace on belt fed fired 308

M

Machineguntony

New member
The 308 rounds below fail the headspace gauge test, right? They're above the top step on the Lyman headspace gauge.

For the life of me, I can't get cases that I've fired through my 240 or M60 to resize back down to spec.

These rounds will not fit in a bolt action. They run fine in the 240, though.

So far, I've trimmed the brass down to spec. Turned the decapping die all the way down as far as it can go in the shell plate (I'm using a full length resizing die). I thought that would resize the brass. Still no luck.

Any recommendations on how to get these cases back to spec, so that it can have proper headspace?





 
And I am thinking its a typo for Bolt fed, phew.

I will make no comments on headspace on a belt fed!

Not my non MOS (so to speak)
 
I would suggest separate brass for the bolt action.

Due to the big chamber (can you say non SAMMII) on a machine gun, you are blowing up your cases and trying to squeeze them back down.

As its not my MOS I don't know how fast this will be but something to think about for the machine gun, crack is one thing, blow out is another and no idea what that means for those.

You will get case separation shortly, ergo the above. I would guess under 5 reloads.

You have to do not only small base but force the neck back down to SAMMII specs to get to shoot in a bolt action rifle.

Or you can buy a Savage (or do a Remage) and see if you can set it to match the machine gun chamber.
 
I am segregating my bolt action brass from my belt fed brass.

Also, I'm using a small base die. Without the small base die, rounds won't even pass the plunk test on my belt feds. The rounds pass the plunk test fine with a small base die. They just don't pass the gauge test.

I'm trying to get them to pass the gauge test. There has to be a way to get the brass into SAMMI spec. It's not efficient or ideal to have 308 that can't be shot in most 308 guns.

And yes, case separation happens after about three to five reloads. I always have a broken shell extractor for that reason.

This has been a project that I've been delaying for the past year. I'm now getting to it. There has to be a way.
 
The brass could be too long, or too fat. But why does it matter? You are not selling the rounds to the public, so why do they have to meet saami specs? It is OK if they chamber fine in your machine gun.

-TL
 
Just another thing to check. Check the rims on your belt fed cases to make sure they aren't nicked. A nick or ding may not let the case head drop down in your gauge. Good consistent sizing lube is needed plus lube inside the neck. I use a nylon neck brush to lube inside the necks. May need another shellholder that you can stone or sand a couple thousandths or more off the top so your die can push the shoulders back a little more. Since you have a shell plate you could remove the material from the die so it could come down a few thousandths. Like mentioned close inspection of your brass to prevent case separations is necessary and keep your brass separated.
 
Tangolima, one reason is because I want to combine all my 308. Right now I have two batches of 308: one belt, one bolt. This sounds like a small deal, but it's actually become a pain in the butt.

In addition, I have have two types of 308 rounds. The finished 308 belt fired rounds will not allow the bolt to close on my bolt guns. But the same round passes the plunk test on a belt fed chamber.

Also, just from an acedemic perspective, I'm thinking that after brass is resized, it should go back to SAMMI specs.
 
Just a general comment that most users of machineguns really don't worry about re-loading, since Uncle Sam (or the local equivalent) is buying the ammo.

Actually, many MGs will allow the brass to stretch since they will begin to open while the pressure is still high. That is a deliberate design feature and part of the steps designers take to ensure functioning under adverse conditions and achieve rapid fire. Unless the brass shows a line indicating incipient separation, a heavy bench press on a solid mount might allow the cases to be resized, but the case life will be short so separation of cases might still be necessary.

(Ain't machineguns fun?)

Jim
 
Now, take this for what it's worth,
In my 16 years of military weapons training, we never had a single machine gun in the arms room that didn't have a chamber/erosion gauge,
From M16s to M60s to mini guns.

If you are talking brass,
As we have discussed endlessly,
Current military machine guns DO NOT have support in the rear of the chamber.

Tapered chambers to guide rounds into the chamber don't support the brass, and every single machine gun I'm aware/familiar with has a chamber that doesn't support the bottom 1/8 of the case.

This means Case bulge or bloat at the bottom.

The ONLY 'CORRECT' way for a home reloader to remove that bloat is to roll it out of the case, from bottom to top.

You 'Can' buy a punch press and dies to properly resize cases, but you are looking at $7,000 to $10,000 for a small punch press,
It takes a very high pressure punch press and specifically made set of dies to do things this way, and quality control is a pain in the butt.

While a case roller (Case Pro) runs about $1,100 to $1,200 for a manual unit,
About $2,000 for a powered unit.

A case roller does just what it sounds like,
Rolls the case between two dies, rolling the bulge from bottom, up the sides to the top of the case, leaving you with a case bottom/sides that are specifically resized to factory specs (or some other specification if you desire).

When the market is there, I can roll up to 250,000 cases a month, and I've done up to 500,000 cases in a month, but it's WAY more work than I want to do.
SO, you might take that for what it's worth... it's not like I'm talking out by butt about something I read about and never done.

Buying a roller will leave you butt hurt about the price,
On the other side of the coin, not only will it eliminate failure to chamber, but it resizes the extraction groove, straightens the extraction rim, rolls minor defects back in where they belong, and on smaller cases, it will push back expanded Case heads.
The driven units will do all this at 1,500 to 1,700 an hour, when it's running full speed, it's actually a full time job to keep the case feeder loaded.
For a machine gunner, that's a good thing!
Last machine gun shoot I went to we dumped about 200,000 rounds in older (less than optimum) chambers so the roller has been a real help, even though I bought it for speed gun pistols originally.

It has simply stopped failure to feed issues in everything I have dies for, from 9mm, 45acp, 40/10mm, .223/5.56, .308/7.62, and I have to run it a little slower, but .30US/.30-06

No more boogered case rims snagging on links! I like that part a bunch.

If nothing else, check out this page,
http://casepro100.com/how_it_works.ydev
 
Yeah, what others have said. I worked on a 99 Savage lever action once that had the same problem. It turned out the guy loaded the ammo so hot it was "Springing" the receiver and expanding the head on the brass. The gun headspaced OK because the receiver would go back to where it was originally. The brass was impossible to to resize. You would have had to swage the head back to spec.
 
Any recommendations on how to get these cases back to spec, so that it can have proper headspace?
Click to expand...

I could say the case has more resistance to sizing than the press, die and shell holder can overcome, it seems that little piece of information is beyond a reloaders comprehension.

And then there are bad habits; I can not think of logical reasons why a reloader would not measure before and again after. I do not find it necessary because I always save unfired cases for comparison. When the case head expands the primer pocket increases in diameter, the flash hole increases in diameter and the case head starts to separate from the case body and the thickness of the case head decreases from the cup above the web to the case head. (Life is not fair). When my case heads increase in diameter there is no jump back, snap back or spring back, once the case head is crushed it stays crushed and (Life is not fair). forget the small base die. The small base die does not size the case head (Life is not fair) again, my shell holders have a deck height of .125" meaning the die can not size anything .125" above the case head plus the radius of the die.

I have from the big inning used feeler gages to increase the presses ability to overcome the cases ability to resist sizing. I can increases the presses ability to reduce the length of the case from a go-gage length case to .12" shorter than a minimum length sized case. For those without pencils that would be .017". Why? I have a use for cases that fit short chambers. And then there are long chambers, same thing; I have a use for cases that fit long chambers.

I have grinders that reduce shell holder deck height, I have grinders that reduce the length of a sizing die from the bottom of the die to the shoulder; I do not grind shell holders or dies because it is not necessary. The one thing I do find necessary is the RCBS shell holder. My RCBS shell holders fit like a hand-me-down shirt; they fit the case only where they touch. On the other hand or in another box I have Herter shell holders, Herter shell holders fit the case head. And? There are advantages to shell holders that fit.

I suggest a reloaders learn to measure before and again after. There is before firing and after firing. There is before sizing and again after sizing. And then there is jump back, snap back and spring back; When I hammer a case with a heavy load my cases have no memory of what they were before I pulled the trigger.

F. Guffey
 
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