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ronas
06-27-2012, 2:19 PM
I am having a 308 rifle built. Currently shoot to 800 yards new range will have 1000 yards.

Shot at sea level
175 SMK or 175 Nosler
use 45gr. varget, get about 2750 fps
Currently shoot these loads with 26" barrel TRG-22

New rifle will be 308 Kreiger heavy varmint barrel contour #17 which is 1.25 to .900 with 1:11 twist.
I can make it as long as 28" I believe.

Weight is not a major concern and it will have a 9" suppressor on the end too so it's going to be long no matter you look at it.

At what point if any do I reach a point of diminishing returns as far velocity and accuracy goes?

phish
06-27-2012, 2:39 PM
shorterisstifferthereforemoreaccuratebarrelharmoni cs

first :p

ronas
06-27-2012, 2:50 PM
shorterisstifferthereforemoreaccuratebarrelharmoni cs

first :p

When you put a weight on the end does that dampen the harmonics? I ask because it wil be shot with a muzzle brake or a suppressor.

FMJBT
06-27-2012, 3:44 PM
When you put a weight on the end does that dampen the harmonics? I ask because it wil be shot with a muzzle brake or a suppressor.



Not sure about dampening, but it will definitely change the harmonics. With that change will come a shift in the point of impact compared to running the rifle without the suppressor. A shorter barrel is less likely to be affected by changes in harmonics as it will be stiffer than a longer barrel of the same contour. A shorter barrel will potentially have less shift in impact between suppressed/unsuppressed use than a longer barrel. For shooting 175's, I'd think you are probably already approaching the point of diminishing returns for velocity at around 22"-24". I'd actually suggest going a bit shorter at 20". Accuracy will be a bit more consistent and the overall length with a can won't be too akward.

Mute
06-27-2012, 3:48 PM
I don't know about you, but I wouldn't particularly enjoying running anything much longer than 20" if I'm going to be throwing a 9" suppressor at the end of it. Even with the shorter barrel you'll have more than enough velocity to 1000 if you reload.

russ69
06-27-2012, 4:07 PM
I don't know about you, but I wouldn't particularly enjoying running anything much longer than 20" if I'm going to be throwing a 9" suppressor at the end of it. Even with the shorter barrel you'll have more than enough velocity to 1000 if you reload.

The 308 can be tricky at 1000 yards. You are trading velocity for B.C. and at 1000 yards it seems you can shoot light bullets at decent velocity or heavy bullets just a tad slower than would be ideal. The Palma guys have done all the work for you but you need all the velocity you can get, so longer barrels are in order. Here's some work from a top shooter.

http://riflemansjournal.blogspot.com/2010/10/cartridges-308-palma-preparation-and.html

"Doing the Math
The ballistic challenge of a Palma match is the 1000 yard stage. That's where the rubber meets the road and the load either works or it will cost you the match. Somewhere between 901 yards and 999 yards, a bullet fired from a .308 runs into a wall, and that wall is the transonic region which roughly begins as the bullet's velocity drops to 1.2 mach. Ideally, we can remain over 1.3 mach and avoid problems, but that's not always possible within safe pressure limits."

Fjold
06-27-2012, 4:24 PM
What Russ says:

At 1,000 yards you need velocity. Look at what the guys who shoot 1,000 yards all the time are using. F class and Palma shooters are all shooting long barrels because velocity is king! Look at the line at all the big matches, all you see is long barrels (26" is a short barrel there).

Bullets have higher ballistic coefficients at higher speeds and therefore less drift.

Accuracy is not so much a factor of barrel length as much as it is of barrel quality. Since you're starting with a Krieger start long since you can always cut and crown it shorter if you want to later.

ronas
06-27-2012, 6:08 PM
Since you're starting with a Krieger start long since you can always cut and crown it shorter if you want to later.

That's what my gunsmith said.

Mute
06-27-2012, 6:42 PM
I know you're pushing it with a shorter barrel, but a 26"+ barrel with a suppressor at the end is no fun. Besides, a suppressed rifle is a different game than the Palma and F-class stuff. If I were shooting the latter two I'd go with a longer barrel too.

ronas
07-11-2012, 9:06 AM
I decided to go with the 26" for finished length. That's the same as my TRG-22 and it works to the length of our current range, 800 yards no problem.

Richard Erichsen
07-11-2012, 2:20 PM
The 308 can be tricky at 1000 yards. You are trading velocity for B.C. and at 1000 yards it seems you can shoot light bullets at decent velocity or heavy bullets just a tad slower than would be ideal. The Palma guys have done all the work for you but you need all the velocity you can get, so longer barrels are in order. Here's some work from a top shooter.

http://riflemansjournal.blogspot.com/2010/10/cartridges-308-palma-preparation-and.html

"Doing the Math
The ballistic challenge of a Palma match is the 1000 yard stage. That's where the rubber meets the road and the load either works or it will cost you the match. Somewhere between 901 yards and 999 yards, a bullet fired from a .308 runs into a wall, and that wall is the transonic region which roughly begins as the bullet's velocity drops to 1.2 mach. Ideally, we can remain over 1.3 mach and avoid problems, but that's not always possible within safe pressure limits."

What limits are imposed by the rules for bullet length, weight (if applicable), etc? I've noticed many of the barrels setup for Palma have very long barrels of 28" with very slow twists, on the order of 1:15" if this is the same competition I'm thinking of.

R

phish
07-11-2012, 3:29 PM
What limits are imposed by the rules for bullet length, weight (if applicable), etc? I've noticed many of the barrels setup for Palma have very long barrels of 28" with very slow twists, on the order of 1:15" if this is the same competition I'm thinking of.

R

depends on which rule set is declared on the entry form

International Fullbore rules restrict bullet weight to 156 gr for .30 caliber, 81 grains for .22 caliber.

registered matches shot here usually use domestic Palma rules which lifts the bullet weight restriction. The Nationals at Camp Perry use domestic rules. However, some regional matches like the Spirit of America Match in Raton and almost all of the registered long range matches shot in CA use International rules with the bullet weight restriction. Confusing? not really, the match programs for the big ones always state which rule set will be used