Garand OAL question

[Mals9]

I am new to reloading, have yet to make a working round, and am looking for advice on OAL. I have measured some Greek surplus and all the rounds fall between 3.150" and 3.220". So I have some Hornady 150gr SPBT and have trimmed the cases to 2.890". When I made my test dummy rounds I set the OAL to 3.20", and I am no where near the cannular. I believe I have about .3" of bullet in the case and I have not crimped. Now I have read that Hornady recommends setting the 150 SPBT to somewhere around 3.1XXX. Is there something special about the Hornady round that they want it to seat shorter than the surplus and much shorter than the 3.340" max. I am trying to avoid getting to much jump before the lands.
Thanks

Mals

 

[Hardtarget]

I had the same question in my first run at loading for my M1. I have the Hornady 150gr fmj and it loads shorter than the Greek ammo from CMP. It was suggested to me that it may be the difference in bullet material. All I know is my reloads, that I've shot, seem to work very well. I thought they were too short and even looked into an all copper bullet to get a longer projectile still weighing 150gr. They cost too much for my needs. I'm only putting holes in paper and don't need the most expensive bullets on the market for that.

Load a few.See how they work in your gun.

Mark

 

[Sunray]

Milsurp ammo isn't loaded for great accuracy. It's loaded for reliability.
"...trimmed the cases to 2.890"..." Hi. That a typo? If not, it's way too long for a .30-06 out of any rifle. The trim-to is 2.484". Max case length is 2.494". 2.490" is ok though.
"...no where near the cannular(SIC)..." You can ignore the cannelure altogether and use 3.340" for any bullet weight. 3.340" was the OAL for .30 M2 ball with its 152 grain bullet too. There's no cannelure on match bullets at all. A crimp isn't required either.
Literally millions of rounds of .30-06 have been loaded long before Hornady created their M1 Rifle chapter. Where Hornady came up with 3.1XX" is a mystery.
The only thing that is important is full length resizing, every time, the correct case length(best to have 'em all the same length) and a suitable powder. IMR4895, H4895(close but not the same), IMR4064 or Varget work well. IMR4064 gives more consistent accuracy than IMR4895 though.

 

[Mals9]

Yeah Sunray that should have been 2.489" for the case. I got that from the Lyman 49th edition and the Lee trimmer worked out perfect. I guess my secondary concern was if the round has a short OAL what kind of headspace issues would be created. I will make some 3.20" rounds and maybe increase the OAl length a little at a time and see what that does for accuracy.
Thanks for the replies.

Mals

 

[dmazur]

Most non-magnum bottleneck rifle cartridges headspace off the shoulder, at a point called a "datum" (which is just a standardized diameter).

Cartridge OAL is not involved with headspace. Headspace determines how "loose" a case would be in the chamber. For a Garand, it's usually measured with a set of headspace gauges, to determine if it's safe to use or if a new barrel is in order. The bolt has to be disassembled to remove any interference from the extractor/ejector, and then the bolt is slowly closed on the headspace gauge to see if the action closes or not.

These gauges are referred to as GO, NO GO, and FIELD. If I'm remembering correctly, the GO gauge is usually used to set up (finish ream) a new barrel, and NO GO gauge is used to check a rifle to see how much useful life it has (like could it be reissued) and the FIELD gauge was evidence the rifle needed to go to the armorer for a new barrel. These conditions were for wartime use, with new brass, and do not necessarily translate to current reloading practice for the M1 Garand.

If you can't close the action on a loaded round because OAL is too long, you have the bullet in the lands and problems with pressure spikes will occur, or a slamfilre. Both these conditions are dangerous. This is definitely a problem, but it isn't a headspace problem. It's a seating depth problem.

However, headspace is still a concern for reloaders. You should get a low-cost gauge referred to as a case gauge, or sometimes as a cartridge headspace gauge. This gauge is very helpful in setting up your FL resizing die for the correct length to permit the action to close reliably (for safety) as well as minimize working the brass to extend case life.

As I understand it, even if you set up the die for a headspace of 0.003" or so, the M1 is hard enough on brass that you should plan on starting over with new brass after 4 or 5 firings. (3 or 4 reloadings.)

The other thing that has to be watched is case length. If the case gets too long from repeated resizing, it can be crimped by the lands and cause dangerous pressure increases. This is usually a problem with bolt-actions, but it can affect the M1 as well. The same case gauge described earlier will also function as a case length gauge. You'll need some kind of trimmer to shorten the case to spec.

Good luck.