I have a 20" heavy barrel 308 shooting 168 amax using IMR 4064 at 42.9gr.What are some of the muzzel velocity's you guy's are getting with close to the same set up im just looking for a good average being I don't have my chronograph yet.
Printable View
I have a 20" heavy barrel 308 shooting 168 amax using IMR 4064 at 42.9gr.What are some of the muzzel velocity's you guy's are getting with close to the same set up im just looking for a good average being I don't have my chronograph yet.
With my 26" barrel, and Sierra 168 HPBT with a similar load I'm getting between 2500 and 2600. With 41.5 grains of Reloder-15 I'm getting an average of 2450 fps. With 43.5 gr of RL-15 I'm getting an average of 2640 fps.
Reason being my groups at 100 are great 200 and up they just get worse I was thinking I might need to speed it up a little more to get the bullet to stabilize better further out
Your bbls twist rate is "king" here. If it is a 1:10 your rotational velocity should be good.
The twist rate of a bbl means a lot more than the bullets forward velocity.
Check this with: JBM Calculations (Stability) It uses the Miller Stability Factor. You are looking for a figure between 1.300 and 2.00. --- SAWMAN
Using 167 grain Lapua Scenar and 43.0 of 4064 I was at 2666 fps in my 20 inch. Your velocity should be just fine. As SAWMAN suggested, check your twist. If slower than a 1:10 you may want to consider the 150 grain area.
What I wish they made was a .308",140'ish gr.,long sleek boat tail and ogive, poly tipped bullet. Something with about a .525-.575 B.C.
These,coupled with a 10 twist 26" bbl would all but render the 6.5Creedmoor useless. ( Actually . . . I think it is useless anyway.) --- SAWMAN