Setting the shoulder correctly in 308

[uneasy_rider]

I had a problem with my first 308 reloads a few weeks ago not working in my M1A, but working fine in 2 different FALs. My M1A would not cycle. Sometimes the fired case would not eject, and if it did eject, it wouldnt move the bolt back far enough to strip a new round out of the magazine.

I was not using a case length gauge at the time. I ended up getting a Lyman case length gauge and discovered my sized cartridges would not go all the way in. I also took some measurements with the comparator you can attach to a caliper, and confirmed my shoulders were not pushed back far enough.

So I screwed my sizing die in further, and resized some more brass. Now everything seems to be OK. My cases fit in the Lyman case length gauge and the comparator says my datum line on the shoulder is in the same place as some factory cases I checked.

My question is, I am not sure why screwing the sizing die in further fixed the problem. i don't see why screwing in the die moves the shoulder back. There is a constant distance, it seems to me, between the part inside the die that contacts the shoulder and the shell holder. When I screwed the die in further, didn't that mean i just made contact between the shellholder and die without having to pull than handle quite as far? The distance between the shell holder and the contact points inside the shoulder of the die should not have changed.

I hope what I have asked makes sense.

 

[30Cal]

The press should cam over-center when you reach the end of the stroke. There's some flex in the press.

 

[Dave P]

When I screwed the die in further, didn't that mean i just made contact between the shellholder and die without having to pull than handle quite as far?



If there is a gap between s/h and die (when case is fully inserted), screwing in (or out) the die will change the headspace.

But if your s/h always touches the die, then screwing in won't make any difference. That is pretty obvious.


Shoulder/headspace issues should not effect extraction. Test your loads in your m1a - do they insert fully and extract easily by hand? If they do not, you MAY need a small base die, which minimizes the diameter of the case. This is what your original extraction problems sound like to me.

 

[rcmodel]

Forget the comparator, forget the shoulder not moving.
You just need to adjust your sizing die correctly is all.

Screw the sizing die in the press all the way until it contacts the shell holder, then screw it in a little more. (1/4 to 1/2 turn more)

You should feel a definite "bump" when the press linkage toggles over.

Any less then that, and press frame springing & linkage slop is not going to allow you to full-length size the case completely.

You don't need a small base die just because your M1A is short-stroking.

What you need is more powder.

Your load is not developing enough gas pressure to operate the action!


rcmodel

 

[ready4shtf]

+1 on the low powder charge. Remember, the FAL has a fully adjustable gas system and will function properly on a wide range of ammo. The M1A is much more pickey. If they were sized wrong, you would have feeding/chambering problems, not extraction.

 

[jenrob]

Take your mic and open it to .001 it looks like it is touching same wit your shell holder and die. You screwed it in to just touch the shell holder. Now when you put the pressure of sizing the brass against the press, Die, linkage, and the space between the shell holder and ram you now have that .001 or more of a distance between your die and shell plate. It still looks like it is touching but if you took a good bright light you would now see a gap. This is why you run the die down 1/8-1/2 turn more to take out the sloop that you don't see.

+2 on the above comments on more powder. just keep working up til it cycles complete. I then go up another .2-.4 above this if not at max to ensure if I go out for a lot of shooting once the gun gets a little grime in the action that it will still have that little bit of extra pressure to cycle the action throughout the day. this is if I'm just out plinking and blowing off rounds. I try to keep as low of a pressure to extend my brass life. If I'm going for accuracy Then I don't mind bumping my loads up or down to get the best.

 

[uneasy_rider]

Shoulder/headspace issues should not effect extraction. Test your loads in your m1a - do they insert fully and extract easily by hand? If they do not, you MAY need a small base die, which minimizes the diameter of the case. This is what your original extraction problems sound like to me.

Yes, they feed and extract easily by hand.

I am already using a small base die (RCBS).

I was told by other posters in another thread that some headspace issues will make you cartridges behave like low pressure rounds.

I am alreading using enough powder. I am using 43.5 grains of W748. This is giving me a velocity of about 2700 fps. I started with a load that was giving me 2400 fps, and worked up to 2700 fps. I still had the problem even at 2700 fps until I moved the shoulder back and fixed the head space problem.

I am not really looking for a solution to a problem, just trying to understand why I was able to move the shoulder back by screwing in the die. I went rom 0% reliability to 100% reliability, and the only change I made was bumping back the shoulder enough that the case would easily drop into the Lyman Case Length Gauge.


Here is the previous thread on this subject:
http://thehighroad.org/showthread.php?t=324124

 

[ATAShooter]

Are you using .308 commercial cases or 7.62 nato cases? My M1A doesn't like .308 much. Some eject and some stay in chamber. USGI extractor made an improvement, however using 7.62 never fails for me.

 

[uneasy_rider]

This is Lake City once fired brass, some undoubtedly through machine gun.

 

[Slamfire]

I am not really looking for a solution to a problem, just trying to understand why I was able to move the shoulder back by screwing in the die. I went rom 0% reliability to 100% reliability, and the only change I made was bumping back the shoulder enough that the case would easily drop into the Lyman Case Length Gauge.

There has to be flex in the press or screwing the die in would not have changed much of anything inside the die.

On a couple of calibers, I had to grind on the base of the die because I could not get the die to size the brass down to cartridge headspace minimum. The die was hitting the shell holder, and I had screwed the die far enough down that there was absolutely no flex left in the press/ram.

 

[jenrob]

Now that you have your problem solved with just taking the slack out of the equipment I would try a regular sizer die and see if it will work. If you don't have one see if you can borrow one from a friend. If you can get away with sizing without the small base you will be ahead. The small base works the brass more.

 

[rcmodel]

+1 to what jenrob said.

Sm. base dies are very seldom, if ever, truly "needed" except in a few tight-chambered Browning semi-auto & early SAKO bolt rifles.

I have been reloading GI 30-06, .308, and .223 brass, for every type of rifle action, for over 50 years.

I have never owned a Sm. base die in my life, or ever found the need for one!

BTW: "Shoulder problems" can be caused by "mix & match" selection of different brands of shell holders & dies.

Not so much anymore, but at one time, RCBS dies & Pacific shell holders, for instance, did not result in correct headspace on a sized case. The same was true of other brands as well.

It's always wise to use the same brand shell-holder as the dies you are using.


rcmodel

 

[30Cal]

If it's once fired MG brass, it'll probably need to be SB resized the first time you use them.

 

[USSR]

If it's once fired MG brass, it'll probably need to be SB resized the first time you use them.

+1. After they've been fired in your rifle, then a regular FL die is usually fine.

Don