.308 help needed!!!

[Mr White]

I'm shooting a .308 match this weekend and have a borrowed M1A to use. I got some once fired .308 brass, a jug of I4895 and M72 bullets.

I'm trying to figure out a cartridge OAL. I don't have a comparator and am using a makeshift setup. I sized and trimmed a case and seated a bullet very long. I put the case in the chamber and pushed the bolt into battery. When I remove the cartridge, the OAL is 2.875. I got this same measurement 3 times.

Is loading .020 off the lands a good idea with an M1A? That would make my OAL 2.855. My Lyman book lists the max OAL for the .308 s 2.810.

Is 2.855 too long to seat a .308? If you're an M1A shooter, how long do you seat your match ammo?

This is my forst stab at loading .308 and this has me kinda confused.

 

[Grumulkin]

For the length, you have to go with what will feed through the magazine unless you're loading 1 round at a time. If you go by the recommended length in your loading manual, you should be fine.

The Hornady manual has loads developed especially for the M1A. If you load up at the lower to middle of the range you should be fine from a pressure point of view. To get the best accuracy, you would need to make up loads with incremental powder charges to see which was best.

 

[cdrt]

+1 on checking what will fit in the magazine.

My last load for the M1A was 41.0 grains of IMR 4895 with the Sierra 168 HPBT, CCI 34 primer, LC 90 cases, trim to 2.005, OAL 2.8.

I have also shot these out of my .308 M1 Garand with good results.

 

[Mr White]

I loaded some practice rounds with just about the same load you suggested, cdrt, and they shot pretty well.

Last night I did my test for length to the lands and got the numbers I mentioned above. Seating the bullets to .020 off the lands made for a cartridge length that seemed long to me.

Unfortunately I don't have time to do proper load development since I just got the gun last weekend and the match is this weekend.

I'll figure out what feeds thru the mags and seat to that length.

 

[Zak Smith]

OAL depends wholly on the chamber and the feed/magazine arrangement of the rifle.

 

[DaveInFloweryBranchGA]

Mr.White,

If the length you came up with will feed in your magazines, it'll be fine and I'd use it. With a magazine fed rifle, if you're using the magazine, the mag limits the over all length. If you're single loading, then you can go out longer than the magazine will take. So let the "magazine test" be your guide as to how far it will let you seat your bullet.

For my part, when I load .308, I load it out as long as the magazine will let me if the chamber is long enough to accept the cartridge and I use the same technique for this as you're using, except I measure 3-5 times and average the numbers I get.

Regards,

Dave

 

[Mark whiz]

One word of caution with loading for a M1A - DON'T make the OAL outside of max spec........................those rifles have a free floating firing pin and a cartridge that ends up too loang can be subject to an out-of battery (slam-fire) Ka-Boom.

 

[USSR]

I'll figure out what feeds thru the mags and seat to that length.

There you go.

Don

 

[Mr White]

I ended up loading them at 2.825". They feed thru the mag just find and aren't so long as to invite a slamfire.

I guess I'll find out how well they shoot on Saturday.

Thanks all for your advice.

 

[Sunray]

Slamfires are caused by improperly loaded ammo, not the rifle. Primers seated too high usually.
2.800"(given in my 45th Edition Lyman book) with 150 and 168 grain bullets works just fine out of my real semi'd M14. FL resizing only, be sure the cases are all the same length and chamfered and deburred.
When you get that far, IMR4064 gives more consistent accuracy than IMR4895. The .308 loves 165 grain hunting bullets or 168 or 175 grain match bullets with IMR4064. Varget works well too.

 

[30Cal]

I've run mine at 2.845" without problems. That's with an AMax bullet. With a Sierra, that's waaaay into the lands.

Shutting the bolt on a long OAL cartridge will get you bullets stuffed into the lands. If you want to find where the lands start, push a cartridge into the chamber with your thumb. If it falls out from gravity alone, all's clear.

 

[Slamfire]

I just seat everything LT 2.800". In fact, recently I have been seating my 168 Noslers to 2.750".

I use my 308 ammunition in bolt rifles and the M1a. The shorter length is easier to stripper clip in a bolt rifle. Less likely to have a clip jam.

To me, I prefer not busting fingernails when pushing rounds into magazines. Long rounds cause more problems then whatever "benefits" you get.

Bullet jump is not that critical in a 308. All of the 308 SMK bullets can skip a country mile and land in the X ring.

Can't say that about Bergers. Heard tales of woe about Bergers being jump sensitive.