M1 Garand (straight pull) proud primers...

[safetyfirst]

So I took my brand new bucket list M1 Garand out today with some 180Grain Federal and some 160 grail Barnaul.

Both exhibited some proud primers after firing, not too bad, just 1mm average, perhaps 2mm.

I stopped after the first clip when I found the issue.

These rifles are supposed to be able to handle most ammo with ease, it’s not like an original 40’s rifle that needs strictly M2 Ball ammo.

I’m going to try Privi 150gn and see if that’s the same but does anyone have any advice?

I’m borrowing a friends no-go gauge which I’ll test the rifle with but this is a brand new gun, just been proofed.

BTW, it’s completely awesome to shoot.

PING!

[bnz41]

You have a PM

[Furiouspilgrim]

Most owners will tell you they are ammo fussy and you need to reload at the lower end of the charge weights.

[snayperskaya]

A chap at my club has one, lovely rifle to shoot, and he has had a similar issue along with hard extraction with some ammo.If I see him on Saturday I'll ask him about it.

[safetyfirst]

A chap at my club has one, lovely rifle to shoot, and he has had a similar issue along with hard extraction with some ammo.If I see him on Saturday I'll ask him about it.

That’d be great, thanks Comrade.

[safetyfirst]

Most owners will tell you they are ammo fussy and you need to reload at the lower end of the charge weights.

I plan to load for it so that’d not be an issue, I’d just like to make sure the rifle isn’t dangerous or faulty.

[Laurie]

Backed out primers are usually a symptom of a combination of excessive headspace and low to moderate pressure. If there is a bit of headspace (or rather a bit more than there should be, as some is nearly essential for easy chambering and operation), the firing sequence sees:

Case is a slack fit longitudinally in rifle chamber but as chambered will likely be against the bolt face with any headspace gap at the shoulder end.

The firing pin pushes the cartridge forward until the case-shoulder contacts the front of the chamber. Only once the cartridge can go no further forward will full primer cup indentation / ignition occur.

Ignition! The firing pin retracts into the bolt and there is a small gap between case-head and bolt-face. Internal pressure rises in the case and the thinner front end case-walls obturate first in the chamber gripping its sides and holding the case shoulders tightly against the matching part of the chamber.

With the front of the case held, and a gap at the rear, the primer backs out until it contacts the bolt face and stops.

At this point, one of two things happen depending on the load / pressure / case construction.

1) Low / modest pressure. The case retains most of its original head to shoulder length leaving a headspace gap and on extraction the primer cup remains slightly proud of its pocket. (The primer may also look very 'flat' confusing people into believing it is an excessive load - it flattens because it is a relatively weak brass cup and when unsupported will flatten out against the bolt-face losing its radius.)

2) Full or high pressures. The case body stretches ahead of the web until the case-head contacts the bolt face and is stopped. The primer is in effect reinserted fully in the process and is now flush with the case-head on extraction. If resizing pushes the shoulders back again to their previous position, the case-body will fail in a few cycles due to separation.

These processes are shown in two photographs here of 7X57mm cases from factory ammunition after firing in a Mauser 2000 sporting rifle with excessive headspace:

http://www.targetshooter.co.uk/?p=1750 ..... and scroll down to the two pics of fired cases.

The full-power RWS ammunition saw case-stretch, has flush (but very flat) primers and is close to incipient separation - ruined and not reloadable.

The low power PMC load produces an unstretched case but proud and slightly flattened primer cup.

This was a bad example of a faulty rifle. In your case, it may be simply a result of the tolerances allowed - ie a mazimum length chamber and minimum length case in headspacing (case-head to shoulder) dimensions. PPU brass has a track record of 'issues' here, but the cases that are reported tend to be the other way - max case in a min chamber causing chambering difficulty, a frequent complaint about PPU 243 ammunition on the Stalking Directory Forum. (Great ammunition, very cheap, but in some factory rifles hard or even impossible to chamber.)

If this is the cause, the answer is to fully fireform the brass in the chamber by firing a full/standard pressure load so it produces full obturation and a close case to chamber fit and on subsequent resizing only push the shoulder back enough to chamber easily and safely. In a semi-auto / straight pull this can only be done with callipers and a case gauge such as the (misnamed) Hornady 'Headspace Gauge'. For precision bolt rifles, shoulders are set back ('bumped') by 0.001-0.002; for semi-autos straight pulls, 0.004-0.005 is needed to ensure full bolt lock up before firing. (The amount of shoulder bump depends on the die setting in the press and may see the die screwed in less than the default setting of hard against the shellholder if this is the issue, but the use of some sort of gauge is essential for this type of rifle. For turnbolts, the rifle itself can be used as a gauge, backing the die out and screwing it in in small steps until a sized case just chambers without resistance to turning the bolt handle down.)

[safetyfirst]

Thanks Laurie, great write up.

I’ve spoken to a few more owners and they’ve said S&B ammo exhibits no issues and the softer end of handloads with 150gn bullets are also good, probably due to the fire forming of the brass...

[safetyfirst]

Ok. So the rifle bolt closes flat on a Forster 30-06 no-go gauge.

They are collecting it at their expense with profuse apologies. Very nice chap.

[Furiouspilgrim]

Literally how long does it take for an RFD to check headspace. Can’t believe shops would sell a new gun without checking. At least you’re getting it sorted. What shop was it if you don’t mind me asking?