Do semi autos mess up bullet seating depth?

E

Ervin

Moderator
This something Ive been pondering for a while now as I was checking and re-checking the seating depth of my bullets.
I got an M1.....so you should see where Im coming from.
I dont load the bullets to be close to the rifling, (84.00mm +/- .02 = is my current seating depth on all M1 and 1903 loads, which is .84 less than max seating depth) I havent measured the exact dimensions of my chamber yet but Id just like to know if there is a theory or practice to seat semi auto loads deeper so during the feeding and chambering phase the bolt doesnt push the bullet farther into the case from the simple brute force of the return spring.

btw: I use Greek HXP brass, so its not a case of weak brass not gripping the bullet sufficiently.
Im not crimping either, I dont believe in that practice.
 
There's no way to know this without your gun. Find a good combination that works well for both, then crimp with either the standard or taper die to keep them from backing out during cycling.

-7-
 
I use Greek HXP brass, so its not a case of weak brass not gripping the bullet sufficiently.
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Yes, neck tension alone will hold the bullet tightly enough to prevent setback in an M1. The bullet profile isn't blunt and the feed angle is quite shallow, compared to something like the 1911 feeding .45 ACP.

As long as the brass hasn't work-hardened (or been annealed to dead soft), and if the case thickness at the neck is correct for your expander button size, you can get proper neck tension. If not, you may have to replace cases, anneal cases, or polish an expander button down 0.025mm or so.

If you figure head separation concerns into the equation, you may decide to replace the brass after 5 reloadings, long before the necks would have to be annealed to restore proper tension.

Generally, if you can take your reloaded ammo and push it firmly against a desktop edge without the bullet moving, it won't cause trouble in an M1.
 
Well for one thing you are limited to just how far out you seat a bullet with the M-1 Garand as the En Bloc well limits how long a cartridge is. As you know loading bullets too long will not allow you to seat a clip. If the bullets are too long the only way to fire them is loaded one at a time.
I too load for the M-1 and I have never had a problem with bullet set back. I don't crimp either. The ony time you would have problems with bullet set back is 1 your brass is worn out and can't hold your bullet in place or 2 repeated chamberings.

I have not loaded Greek brass although I have some on hand. I have loaded Lake City and TW GI brass. The best money I've found for making smaller groups is uniforming the primer pocket. Also with GI brass there is the primer crimp to remove. I like the "feel" of a swaged pocket for seating primers. I use the Dillon Super Swage which makes short work of swaging a large amount of brass.
 
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What bullets are you guys using? I have some Hornady 150gr FMJBT that I am looking to load in Greek brass. I will have to seat it at an OAL of 3.195 to reach the cannelure. This is considerably shorter than the standard 3.34".

Mals
 
M118 LR, SMK I think, no cannelure.
I can only seat this bullet in HXP brass, it literally slides right into commercial brass by hand.
 
Yes, neck tension alone will hold the bullet tightly enough to prevent setback in an M1.
Click to expand...

I had issues with bullet setback in my M1, and after trying to adjust my sizing die to no avail went with a FCD which fixed the problem. As Ervin mentioned some of the bullets would slide in by hand pressure.
 
I'm also loading Hornady's 150gr FMJBT, and I'm having no trouble with Winchester brass, which I believe is thinner than HXP.

My COL is 3.185", and there are no feeding or setback issues.

If you're able to push the bullets into commercial brass by hand, it looks like something is wrong with the expander button. It should be creating the same ID in HXP or commercial brass. The HXP may have a little more spring and that could explain the different (smaller) diameter.

However, a .30-06 resizing die should be able to resize commercial brass properly for a .308 diameter bullet.

Get a spare expander button and polish it smaller and see if that fixes things. It will increase neck tension for the HXP brass, too.
 
First thing that I will try to do when I get back out to the range is load 2-3 clips into the M1, and manually operate the bolt, to cycle each of the 8 rds in and out of the chamber. I'll re-measure each round for bullet setback.
Im glad to say theres no effect of this in the 1903 bolt action, no matter how hard you slam the bolt forward.

What initially got worried me about this was in the case of the M1. I was trying to load a new clip into the rifle, it was pretty chilly out and the ammo wasnt lightly lubed (which is gonna be my new practice with semi autos from now on...) anyways, the bolt stripped the 1st round and instead of driving it straight into the chamber, it slammed it 1-2mm right above it. Causing a jam.The bullet being a shorter soft point (Hornady) was pushed about 1/3 of the way back into the case.
Luckily the M1 has a quick clip eject feature so in a match situation you could have an extra clip ready to try again with 8 dependable rounds.

Great rifle, just gotta be aware of its little quirks.
 
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