Question about O.A.L. and powder charges

[kdsd731]

I just have a question about changing O.A.L.. I've been loading 30-06 150gr FMJBT to the cannelure which is an O.A.L. of 3.266" with 46gr of H4895. I recently decided to check the length that my bullet gets seated by sticking a long round in the chamber and closing the bolt on my rifle to seat the bullet to my rifles max C.O.L.. After backing down the bullet another .025" the C.O.L. is now at 3.395". Now with that O.A.L. being longer than what my Hornady book says to seat it to do I just use the same load data for the H4895 powder as the books O.A.L.?

[russt]

Yes, it will be safe to do so.

[russt]

You might have to rework up your load though as this will change the pressure.

[mark501w]

Pull the bullet out lowers the pressure push it in raises the pressure. Unless you have contacted the lands & grooves then pressure goes up fast!

[JagerDog]

0.025 off the lands will be safe. Might be able to speed 'em up (more powder) a bit since you increased case volume. Try a few and see if it enhances accuracy. Some guns are sensitive, some not so much. The throat could be eroded too, but an 1/8" longer doesn't sound bad. Most rifle bullets for bolt actions don't even have cannelures.

If you ever shoot copper, it tends to like more freebore.

All this is assuming bolt action. Autos/pumps generally like spec lengths to feed properly.

[Ahhnother8]

Pull the bullet out lowers the pressure push it in raises the pressure. Unless you have contacted the lands & grooves then pressure goes up fast!

Actually, the first part is backwards. Lots of bullet jump gives the gas a micro-second to escape around the bullet before the bullet contacts the lands, hence lowering the pressure. Try it and see.

[kdsd731]

Thank you for the input guys! I look forward to making up some new rounds to these new specs and seeing how they do. And

And yes, it's a bolt action.

[FLIGHT762]

Just be aware that the 150 grain FMJ bullet doesn't have a lot of bearing surface. When you seat bullets, you should to try to get at least one caliber (.308" in your case) of the bullet's bearing surface to contact the case neck to get proper neck tension and to retain the bullet properly in the case when you seat a bullet.

I do seat many bullets a little further out than the cannelure is set, but I make sure there's enough bullet in the case neck to hold the bullet properly.

[kdsd731]

OK, that's a good pointer. What is a good method of determining proper neck tension? I can tap the bullet on the table and it doesn't change C.O.L.. Is that good enough? I just made up these 30-06 rounds using some 7383 powder I got for cheap and a two different bullets I have on hand at the moment. The left is using 168gr HPBT set to 3.375" and the right is using some 142gr inert tracers set to 3.440". I hope I find a good round with the inert tracers and this powder. Both are new components for me. But if they work well, I can't beat it for $3.20 a box of 20.

[FLIGHT762]

SAAMI Maximum COL for the 30/06 is 3.340". Why on earth are you loading past that???

As long as you're not jamming the bullets into the lands, you'll be okay, but for reliable feeding from the magazine COL you shouldn't be much past 3.340".

Will these rounds feed from your rifle's magazine without having to single load them?

As far a proper neck tension, you can take a couple sample loads and press the bullet tip into the side of your steel bench and check to see if the bullet moves into the case. If it doesn't move using hand pressure, your tension is sufficient.

[kdsd731]

Yes, both rounds amazingly fit in my magazine. The rifle is an old Interarms Mark X. I can press the round on my table without changing the length. I have .025" before the ring lands.

[JagerDog]

IMO, pressing them on a bench is not a very good test and will only identify really poor grip. The acid test is multiple recoil actuations. Verifying 0.002 interference helps. Soft case necks (over annealed) can still create issues.