.308 Small base question

[Cerberus]

Maybe someone here knows the reason for this. I am about to run some 7.62 Nato brass thru the SB sizer and have read not to use this stuff in bolt action rifles. What is the reasoning for this? I know I can use surplus 7.62 in .308 chambered bolt rifles.

 

[Leo]

I never needed a Small base sizing die, even in the tight chamber of a true Springfield Supermatch M1a. If the brass goes through a regular full length sizer, it is fine, including in your bolt action. I do not know how this stuff gets started. SAAMI specs are all fully published and the firearms and reloading manufacturers make their stuff within those tolerances. I have also fooled with wildcat cartridges for which there is no SAAMI specs to standardize manufacturing. Those can be all over the board. The 6.5 X 284 cartridge was like that when had the first one built. I had to have a custom neck sizing die made to match my rifles chamber. A few years later it was standarized. 7.62 and .308 have been standardized many years ago. Don't worry.

If you have a micrometer you can double check every dimension. Companies like Wilson also make a full body case gauge with minimum and maximum dimensions already milled in. You can always double check with one of those.

 

[red_zr24x4]

I've never used a small base die either. I don't own a .308 bolt gun (I do own a M1A), but I know people who do and they run 7.62 brass through them. I do own a .223 bolt gun and use 5.56 brass in it with no ill effects.

 

[gun_nut]

I run .308 through a small base die when I purchase Milsurp brass. Machine gun tolerances have too much slop and need to be sized with a small base die (once). To bring the brass back to specs. After the first sizing, I use full length dies.

GN

 

[x10]

I've got a Bolt gun that I had built for me to the very minimum spec and because I know the smith personally he put it a bit tighter than he normally would,

I have to use a Small base die on this one and military brass just is tight but my supply of small primer benchrest brass fits very well, but I only use certain ammo in this rifle.

I would say if its a production gun and the military brass hasn't been run through a M60 or the like then standard dies will be ok

There are always exception to everything out there

 

[Cerberus]

Well, I can say with lots of surety, that almost all of surplus 7.62 brass sold nowadays is ran thru M240 MGs.

 

[downzero]

Well, I can say with lots of surety, that almost all of surplus 7.62 brass sold nowadays is ran thru M240 MGs.

It's too bad the price doesn't reflect it.

What kind of die are you using? My FL .308 die is a Dillon; supposedly they are small base.

 

[Cerberus]

My standard FL and SB are both RCBS.

 

[Broom_jm]

Are you planning to use this 7.62 brass in a bolt action, after it's been resized? Do you recall any of the logic given for why you shouldn't use this brass in a bolt-gun, even after using a SB sizing die to get it back down to spec?

Fundamentally, you should size brass only as much as it needs to be sized to function in your firearm. If you've got the camming action of a bolt-action and you're sitting at a bench with all the time in the world, your brass can actually be just a tiny bit larger than your chamber. This gives you a "crush" fit that can result in excellent accuracy and increased case life. If you took that 7.62 NATO brass, ran it through a normal FL resizing die, and it came out small enough to run through your bolt, or even your semi-auto, that's good enough. In other words, you don't have to use the SB dies...unless you HAVE TO use the SB dies. Is that confusing enough?

Now, some guys like their 308/7.62 brass to be plenty small, when running it through a semi-auto, just so they don't have any jams. I get that and it's probably smart. The same logic does NOT apply to a bolt-action, where the much slower, and more controlled, feeding of cartridges does not warrant sizing brass excessively.

YMMV -- n' all that

 

[Cerberus]

Are you planning to use this 7.62 brass in a bolt action, after it's been resized? Do you recall any of the logic given for why you shouldn't use this brass in a bolt-gun, even after using a SB sizing die to get it back down to spec?

Fundamentally, you should size brass only as much as it needs to be sized to function in your firearm. If you've got the camming action of a bolt-action and you're sitting at a bench with all the time in the world, your brass can actually be just a tiny bit larger than your chamber. This gives you a "crush" fit that can result in excellent accuracy and increased case life. If you took that 7.62 NATO brass, ran it through a normal FL resizing die, and it came out small enough to run through your bolt, or even your semi-auto, that's good enough. In other words, you don't have to use the SB dies...unless you HAVE TO use the SB dies. Is that confusing enough?

Now, some guys like their 308/7.62 brass to be plenty small, when running it through a semi-auto, just so they don't have any jams. I get that and it's probably smart. The same logic does NOT apply to a bolt-action, where the much slower, and more controlled, feeding of cartridges does not warrant sizing brass excessively.

YMMV -- n' all that

Nope, not primarily for a bolt gun. Primarily for the M1A.

 

[red_zr24x4]

Nope, not primarily for a bolt gun. Primarily for the M1A.

I use RCBS FL dies for .308 for my M1A as long as you bump the shoulder back you should be GTG.

 

[Cerberus]

Cool. I plan on getting out the mics and measuring a piece from each die, and one before the die just to see how much each will sqeeze them down. I've been known to make a dummy or two to check if everything is going to work out before I start the LD.

 

[Broom_jm]

Yeah, don't talk yourself into thinking you have to use the SB dies. Start with the standard FL die and see if that's enough. If it is, that's all you want.

 

[Aszerigan]

SB dies are used with AR's and semi-autos with exceedingly tight chambers. Wylde chambers often require small base dies. If I remember correctly, they're only made in mil-match calibers, .223, .308 and .30-06.

If you're gun doesn't need an SB die, don't use it. It'll lead to more frequent trimmings and weakening of the brass.

 

[bdybdall]

The last issue of Rifle magazine had an article about M1's, M14's, and M1A's. It stated that a lot of M1A's had a chamber that was on the tight side of tolerances and therefore needed a SB resizing die. Pick up a copy at the newstand. I get mine at Krogers.