155.5 berger fullbore in .308

[armike]

Ok looking for some advice. I picked up 500 fullbores to shoot in my rem 700 308 lrt. It has a 1-12 twist barrel. I loaded some with imr 4064 at 45 gr. And getting a velocity around 2921. But the accuracy is not to good. I can only load to magazine length which is 2.825. I have heard they don't like to jump. Should I try another powder? Ideas please.

 

[Dgd6mm]

Do you know how far you are jumping them? What kind of accuracy are you getting? IMR 4064 is an excellent powder for the .308.

 

[armike]

One of the better groups measured 1 1/4. I have no way to measure the jump. I just made them as long as I could. I'm looking for about half. This is the worst groups I have seen from this rifle.

 

[ShootDots]

For that weight bullet, IMR 8208XBR has proven itself many times over. That is the direction I would be moving in..

 

[armike]

I did pick up a pound of that the other day to try out. So I will give it a go and see what happens thanks again.

 

[watercam]

The Fullbores are very tolerant of seating depth. The sweet spot for one of my Palma rifles is jumped .018", for my back-up rifle it is .025". These are not VLDs, they can most certainly be jumped and sometimes quite a lot. Try .020", .030" and .040" off the lands.
In Lapua cases/Tula SR primers I am stuffing 47.3 grains of 4064 or 46.5 gr. of Varget in for 3050 fps from 30-32" barrels.
At some point you will need to be able to measure your ogive seating depth - may as well spend the $40 and buy a Hornady OAL gauge/modified case and get started.

 

[ShootDots]

I did pick up a pound of that the other day to try out. So I will give it a go and see what happens thanks again.

I know you presently have no way of determining your actual seating depth. I want you to know that just as importantly as powder selection and maybe more so , is where the bullets are seated in relation to the lands. You R-E-A-L-L-Y need to rectify that situation.. If you don't, you may being fishing for accuracy that may never come. It's potential may be there, however, you need to wring it out.

 

[armike]

I agree with the need to know the seating depth of the rifle. But I don't believe I will be able to load them to the proper length and still feed from the magazine. Eventually I will put a detachable magazine system on it and still I don't know if I will be able to get the length I need.

 

[Dgd6mm]

The Alpha II mag will let you get out to 2.90" or so.

 

[CJ6]

For that weight bullet, IMR 8208XBR has proven itself many times over. That is the direction I would be moving in..

+1

 

[Keith Glasscock]

Sometimes, one must look at the result of various components. The nose length of the 155.5 Fullbore is ~.825" If I load it to a COAL of 2.825, then the entire bearing surface of the bullet is inside the case neck. Not having bearing surface in the freebore can cause all kinds of weird problems.

I theorize that the problem is related to the case being pressed on by the ejector without the benefit of the bullet in the freebore. On firing, the bullet first has to "find" the bore before it can even jump to the rifling. The result is similar to extremely bad runout.

When loading to magazine length, it is best to find a bullet that will help you. The design considerations for that job are well within the 168-175 SMK series of bullets and the Berger 175 OTM.

BTW, the 155.5 Fullbore does like to jump. I have proof.

 

[truchot1]

I am jumping these 40 thousandths in my Palma rifle. Outstanding accuracy! Every gun and every barrel is different. It took me a while to test longer jumps and glad I did.

Cheers!

Greg

 

[armike]

Thanks for the replys fellas. I'll keep working at it!

 

[people]

You could also try different primers.

 

[SWRichmond]

Factory throat is no doubt horribly long. I recall trying to find the lands in a factory Remington 26" varmint barrel and I could not touch them with 155's. They were jumping almost 0.100".

 

[Shooter2112]

armike -

What I shoot - Savage 12FTR 1:12 .308. It loves 155.5 VLD's the best. Unbelievably consistent bullet.
Busdriver is dead-on when he says that the VLD's don't mind some jump. I also have had the same experience.
The best load I have is 155.5 VLD, 47.0gr Varget, .010 off, Lapua brass necked .335. I don't turn necks. I'm getting sub-sub-MOA at 600-900 all day long if I do my part @ 3040fps. Keep in mind, my barrel is 30".
I know this may not be perfect advice, because you are trying to use IMR4064. I shoot that powder in my other 308's as well - mostly my M1A - however I have learned that with I4064, you will see pressure signs before you get to full capacity in a commercial/mil 308 case, and way before you even think about compressing it.
During load development, I shot RL15 and I4895 with good results, but none of those loads got over 45gr and 2900fps without the pressure signs that made me think I might be pushing my luck with those slower powders.. These powders are in the same burn range as I4064, but you have to go real slow with the mil-speed powders because pressure sign starts to show up in a hurry........big changes in as little as half a grain. Watch I4064 in hot weather too because it will 'get faster and hotter' in hot weather too.

All the best,
S