Importance of brass length-7.62x54R

[Sam Adams]

I am about to handload some 7.62x54R brass for my Finn M39. I got some new cases from Graf's and ran them all through a full-length RCBS resizing die. I was going to trim the brass last night, and looked at the specs in the Sierra and Hornady manuals, as well as online.

The longest acceptable length for the cartridge is 2.114 in. Sierra and Hornady say to trim to either 2.104 or 2.105 in.

OK, fine. I was going to trim to 2.105 and then start loading...except that when I measure the cases they were all at 2.095-2.100, much shorter than the TTL listed by Sierra and Hornady. Are these cases unsafe to load and shoot, or are they OK? Thanks, in advance, for your answers.

 

[Crosshair]

No, they will be fine. The only problem you will have is you will loose a ever so small ammount of powder capacity because you have to seat the bullets deeper due to the short neck. They will strech from use.

 

[Sam Adams]

Thanks. I thought that they'd be fine, but I wanted to hear from someone else. I'm not too worried about losing a bit of powder capacity, especially since this is my first go around with reloading this cartridge and this rifle...and since I have a 108-year-old rifle, I don't know how much abuse it has suffered and I'd like to work up to loads from the bottom end of the scale. Again, thanks.

 

[Cosmoline]

There's a wide variation in case length. Lapua brass is actually classed as 7.62x53, but function is the same.

 

[Sam Adams]

Cosmoline

Could I surmise, then, that if I accidentally overtrimmed some of my Graf's 7.5x55 Swiss (by up to 5/1000ths of an inch) that it would be OK to use them as well?

 

[Cosmoline]

Could I surmise, then, that if I accidentally overtrimmed some of my Graf's 7.5x55 Swiss (by up to 5/1000ths of an inch) that it would be OK to use them as well?

7.5 Swiss headspaces on the shoulder, and Swiss rifles tend to have very tight tolerances. 54R headspaces on the rim and most Mosins have very generous chambers. The shoulder and neck on a 54R does not play as vital a role as the shoulder and neck of a 7.5 Swiss or other more modern rifle cartridge.

That said, such a minor overtrim wouldn't cause me any big concerns.

 

[Sam Adams]

Thanks, Cosmoline. Now I'll have about 10 more of my Swiss cases to use (I was simply going to recycle them). Of course, I'll load them lightly for the first firing and check the cases very well before reloading, just to be sure.