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View Full Version : Barrel twist & length for 308 Win ??



miele
02-08-2008, 07:34 PM
Well I pretty well decided to go with Benchmark Barrel on my model
10 Sav Tactical rifle:D:D
Now I gotta pick a twist and barrel l My savage model 10 had a 1x10
I think:confused: my DPMS LR 308 has a 1x12 both have shot bullets from
150 gr to 178 grains very well ;) The sav is 24 inch as is the LR308.
Which length and twist would you guys pic ??
Sorry for all the questions,but you guys really know your rifles :D
Thanks
John

JeffVN
02-08-2008, 09:08 PM
How far out are you planning on going, and what are you goin to use it for?

For punching paper, the Palma and F-Class TR guys tend to use the Sierra or Lapua 155 grain bullets and readily go to 1,000 yards - running them between 2,900-2,950fps. At that speed, you'll get roughly 4,000-5,000 rounds of target grade accuracy using a 30-32" tube. (Twist tends to be 12-14)

Tactical competion and hunting guys run the 175 grain or heavier bullets out of anything from 20-26" at roughly 2,600+ and get the same useful life (twist can be anything from 10 to 12).

JeffVN

miele
02-08-2008, 09:58 PM
Well most of my shooting will be done from 100 to 200 yards but someday
I would like to try F class type shooting,however I doubt this will happen:rolleyes:
So I guess this would put me in the Tactical/hunter group.
Wouldn't the 175 gr bullets be suitable for the really long shots :confused:
Lets say up to 1000 yards,the only place around here for 1000 yards
is in Williamsport PA range maybe someday I can get a chance for that
type of range:D

Robert_in_MT
02-09-2008, 04:16 AM
I believe the palma and f/class target rifle are still limited to 155 grain max. You could go heavier in 1K F/class open though, .338 or .35, I can't seem to remember right now. Most 1K are going with a fast 6 now 107-115 VLD at 3200fps+, or else with a 6.5/284 140-165 VLD at 2900+. Old school was a 30/378 with 220-240 at 3000+, you noticed when you pulled the trigger.
RC

Asa Yam
02-09-2008, 01:05 PM
I believe the palma and f/class target rifle are still limited to 155 grain max.
Not in the US they're not. Read the NRA highpower rifle rulebook, and see for yourself. Link to the index (information is accessable by clicking on links in the index) is at http://www.nrahq.org/compete/RuleBooks/HPR/hpr-index.pdf . Sections 3 and 22 cover rifles. Section 3 also covers ammo.

jo191145
02-09-2008, 01:26 PM
I'd go with the 12 twist. If you ever decide you want to reach way out there you should be able to develop a suitable load in the 155-175gn range.

mcm308
02-27-2008, 05:52 PM
12 twist is fine for 100-300 yard with 168's...If you ever plan on going beyond that. I suggest the 10 twist for the heavier 175 bullet and up. JMO.

J. Valentine
02-27-2008, 07:16 PM
Using the .308 Win at 1000 yards you need to keep the bullet supersonic at that range.
The .308 Win has not got enough powder space to do that with the heavy bullets so you need to stay at around 144 to 155 grain and a ballisticly efficient bullet to boot.
Keep the barrel long as possible and use a 1 in 12 or 13 twist .

JeffVN
02-27-2008, 09:24 PM
I'm not sure what others are finding, but I routinely shot Sierra 175 smks out of my 12 twist 24" barreled .308 tactical rig at 2,620fps in Houston and it was supersonic at 1,000 yards (Bayou Rifles was the range). I have seen others do it shooting the Sierra 190smks out of a 24" 10 twist barrel too. It generally takes 2,900 or more with a Sierra 155 to keep it going pointy end first at a 1,000, but the 175s only need to ge launched at 2,550+ to make it down to the pits pointy end first. I'm not saying that is optimal by any stretch, but it will get there and be supersonic.

My brother is currently doing well in F-Class TR with his 24" tactical rig with a 12 twist Broughton shooting the Lapua 170 lockbases at 2,675fps.

JeffVN

J. Valentine
02-28-2008, 02:59 AM
How did you measure the actual velocity at 1000 yards ?

JeffVN
02-28-2008, 07:38 AM
If you are asking me about veloicity, we didn't measure the velocity at 1,000 yards. We looked at the targets and saw that the bullets were going through the target pointy end first and that they were accurate - as accuarate as a tactical rifle at that range should be. Sierra 175s are predictably notorious for their erratice response to transitioning back through the sonic barrier. If you've ever shot or seen the Federal Gold Medal Match Sierra 168 ammunition shot at 1,000 yards you know what I mean - bullets keyholing through the targets and not capable of holding 2-3 MOA.

Faster is always better, and when you shoot on the ragged edge of stability you will eventually get bitten when it does not work because of low temperatures or other resaons. But if someone has a barrel and ammo combination capable of pushing a 30 cal. Sierra 175smk to 2,620fps, they will, in my experience, be stabalized and accurate to 1,000 yards.

My statement is based upon my experience and that of a host of others that come from the military background who have shot military ammunition out to and beyond 1,000 yards.

I realize this is a Benchrest forum, but I find it hard to leave my roots totally behind.

JeffVN

tylerw02
02-28-2008, 11:54 AM
Ideal bbl length and twist for .308 Win for general shooting to me is 22", 1:11.5" twist, 3 grooves.

If I'm shooting 1,000 yards, give me all the bbl I can get and a 1:12" or 1:14" for 155 gr Lapua Scenars. But if I really need to shoot 1,000 yards, I'm picking my 6.5-284 or 6mm Ackley. The .308 Win really isn't that potent of a 1,000 yard gun, but is a great compromise for 800 yards and less.

J. Valentine
02-28-2008, 03:56 PM
That is fair enough I just wanted to know if you were actually getting accuracy that would indicate that the bullets have not become subsonic.
My question was the best way of drawing out the info because I knew it was very difficult to do.

CWPINST
02-28-2008, 06:54 PM
The 168's are the ones that get squirrely when they get hit in the butt by the shock wave. The 175 was designed to be more tolerant of the transition. It has a little longer boat tail.

John Kielly
02-28-2008, 07:14 PM
The .308 Win has not got enough powder space to do that with the heavy bullets so you need to stay at around 144 to 155 grain and a ballisticly efficient bullet to boot.
If you were to say with a standard throat, I'd go along with you, but along with a number of British & Aussie 1200 yard match rifle shooters, I get velocities better than 2775 fps out of 210 grain Bergers or SMKs & nearly 2800 fps out of 200 SMKs with MOA accuracy at 1000 yards. I'm loading the Bergers out to 3.15" OAL & yep, the 200s are jumping a tad with that throat.

J. Valentine
02-28-2008, 10:52 PM
I think you are correct that is the real problem , tight match chamber and short throat = less powder space with the longer heavier bullets.