Need help 308 cannelure seating depth.

[Jacob36g]

I'm new to reloading and dont want to mess up tremendously. I am reloading 308 win for my m1a. All the Info I've found says the COL is 2.810. So I got hornady 150 gr fmjbt with cannelure. Using new brass( starline) , ramshot tac powder and cci primers. So I did a dummy round after installing the dies. And the cannelure is nearly to the case mouth but my COL is 2.767 . Now I've read and heard you dont want to seat the bullet to deep as that could increase pressure...dangerously.

So my main question is should I seat the cannelure to the case mouth? Even though it's under the 2.810? I've done the mag test and chambered the dummy round it all seems fine but I just dont wanna have a big problem over a tiny measurement difference.

 

[spclark]

Which bullet’s that info for that you’re citing gives a COL of 2.810?

Different bullets - with or w/o cannelure - will have different base-to-tip lengths even if they weight the same.

Those two numbers differ by only 0.043” which isn’t much at all.

What’s more important is how bullets differ in length from base to cannelure. You’re using that dimension to determine seating depth rather than the more common base-to-ogive dimension where distance to lands is more a consideration than mag-length loading.

My take would be to back off half a grain if you think that 0.040” difference is a significant risk of putting pressures over what they ought to be.

Or use the exact same bullet that’s spec’d for that 2.810” COL.

 

[Bc'z]

Or....
Forget that there is a cannelure and load them to your desired length.
You shouldn't need to crimp if your neck tension is around. 003.

I load some midway specials that resemble a 140amax in wife's 260 cannelure is roughly .2 away from case mouth

 

[spclark]

Or....
Forget that there is a cannelure and load them to your desired length.

Yep, there is that option!

 

[Mad_Charlie]

Ignore the cannelure, unless the load spec's in your manual for C.O.A.L. just happens to land it there. Most folks usually start at 2.800 for the M1A.

Max in my mags is about 2.820, but make sure you aren't jamming the bullet into the lands, (not likely, but worth checking) As noted, you shouldn't need a crimp with .003 neck tension. The Sierra 2115's have the cannelure in a better location than the Hornady's and they shoot better in my M1A's.

 

[Rdlningcltchdmpr]

Ignore the chanelure. But do make sure neck tension is adequate as you resize brass. And switch to a match type bullet . fmj bullet's are not up to par in accuracy.

 

[Mike7.62]

I use the same bullet (HRN 150 gr FMJ) for making training ammunition, as well as Starline or LC brass, CCI #34 .mil style primers and 44.0 gr IMR 4895 powder. I load to the cannelure, which is under mag length for my M1A. The accuracy is not something that I would use in a High Power match, but it is definitely MOH out to 400 yards, and is very much less in cost than match bullets. Match bullets are the cats a$$ for matches or long range shooting, but for high volume shooting where MOA isn't a requirement they will serve.

Whether you use the above advice IRT seating depth with the FMJ's, or just seat to the cannelure is up to you, but going to a great deal of trouble when using a bullet not designed or known for great accuracy can absorb your time for little return. I will take the time to assure consistent seating depth when assembling ammunition to be used where accuracy is paramount, but not for high volume short range training or plinking.

BTW, the COAL of 2.810 is the maximum length for the generic loaded cartridge, not the recommended COAL for every bullet used in that cartridge. Many bullets will be much shorter than the max COAL due to differences in bullet weights, profiles, and lengths.

 

[Rsadams]

If your not loading a max or close charge just seat them were the cannelure is there , and crimp... I do crimp for an automatic as cheap insurance... That's not that much difference as said above in seating depth.... Start low and work up and you won't have a problem , you shouldn't be loading as hot for your automatic as you would for a bolt gun... Most of the time a screaming hot round isn't an accurate round and unless there's some reason you need that extra fps there's no need for it especially in practice ammo... The paper can't tell the difference....

Yup seating a bullet deeper will increase pressure but if you start low and work up you won't have a problem.... This is how you should be doing it anyway... You may want to do some reading on why to not load hot rounds for an automatic... I use TAC in my .223/5.56 rounds but for .308 I use a stick powder like IMR 4064.... You will probably get a better powder burn but the stick powder doesn't meter very well out of a powder thrower.... For .223 I do use the powder thrower on my Dillon but for large cases like .308 etc I weigh each one by hand and /or use the trickle up method...