tight .308 barrels?

P

peterdobson

CGN Ultra frequent flyer
Business Member
Rating - 100%
109   0   0
Location
Halifax
Some(many?), TR shooters are using tighter, .3075/.298 groove barrels for .308 Win. with 155 grain bullets. Can anyone offer any tested results showing these barrels should be used over .308/.30 groove dimensions with match 155grain bullets?

We are aware of the concept of tight barrels for milspec ammo, but this inquiry related to match bullets.

Regards,

Peter
 
I looked it up for a rifle project and here is what True-Flite has to say on this subject:

Bore and Groove Diameters; Recommendations.

Now that the much-reviled military spec bullets are largely no longer in use, there is only a very limited need for the tighter bore and groove diameters of past years. The excellent 154 to 155 grain match bullets by Sierra, Lapua, Hornady, Nosler and BJD work just fine with standard .30 calibre barrel dimensions. Of course these bullets work very well in tight barrels too but pressures may be higher and bore fouling may increase. Simply put...if you are using match bullets, don't use the tighter barrels. The only application for the tighter spec barrels may be with UK shooters who feel that the Radway Green military issue ammunition groups better out of tighter barrels.
Click to expand...
http://www.truefliteriflebarrels.co.nz/13544/9297.html

Alex
 
One thing that I forgot to mention:
Around 20 years ago, I asked Leo D'Amour why long distance 7.62 NATO shooters used a tight bore and his answer then was that it increased pressure and therefore bullet velocity to insure that standard issue 7.62 NATO FMJ was still supersonic at 1000 yards. The point being that bullet often become unstable in the transonic zone.

Alex
 
The confusion was caused by metric to imperial measurements. the 7.62 bullet measured .307, not .308. Gas would go past the bullet in a 308 bore causing a reduced velocity and accuracy. It has been standarized at 308 bullets now for everybody as far as I know. I dont think you can find any 307 dia bullets anywhere these days inc. 7.62 new ammo.
If you have a stash of old Nato ammo it may have 307 bullets.
Useing 308 bullets in a tight bore will raise pressure as the bullet will have to be swaged down during firing. Not a good idea but doesnt seem to create a problem.
Mick McPhee
 
Brian Litz is brilliant, but Nammo Lapua Oy recommend CIP spec barrels and we've seen considerable success with standard spec barels in .308 Win. Terry Perkins' opinion hold's weight, as he is a top FClass shooter and his knowledge helped him win a Western FClass Championsip. This M. McPhee is one of Canada's best gusmith, so lots of worthwhile input.

Supporting tight barrel results are Maynard and other experienced shooters and it's results that count.

Hopefully we can do some longrange testing later this year and meanwhile, appreciate views.

Regards,

Peter
 
Peter,
I think you're going to find that Alain Marion, Scott Murray, Des Vamplew and just about any TR/Palma shooter I know still use the tighter bore, 4 groove barrels. I used my McLennan tight bore last spring with Lapua 154grs with no problems. I admit after 10yrs off, my wind reading skills need practice, but I have targets that show 5 shot groups in the .2's @ 100yds.

I've also built several 7.62x39 and own a Ruger with a .308 bore and shoot .309/.310 bullets regularly through that bore. It seems tighter bores and short bearing surface .30 cal bullets work.
 
I don't have any experience with 0.3075/0.298 with 155's, but I do with 190's. With the 190 SMK, I don't see a difference. But, when I tried the 190 Nosler Custom Competition bullets, none of my regular .308 barrels would group. It was bad, like 6" groups at 300 yards bad. The tightbore shot them better, still not as good as 190 SMKs, but the groups were at least reasonable (~2").
 
You'd think .3075/.300 would make more sense then .3075/.298. You get less bullet deformation which I always thought was a good thing.
 
The crotchety Paul Reibin concurs with clatartar. J.Marshall, NS, a longtime TR shooter and gunsmith, the oldest person to qualify for second stage Bisley, says "no need for for tight barrels".
 
kombayotch, we know that are an engineer: why do you think the tighter barrel worked with the Noslers?

Armafix, we assume Mr, Litz recommends tigher barrels for Palma: does he state reasons? Is it because of more stripping in longer barrels?

Regards,

Peter
 
Peter,

I didn't really investigate it since knowing the reason wouldn't have made them shoot any better. It could have to do with bullet diameter, jacket thickness, or any number of things. The Nosler is made with a J4 jacket which is thinner than Sierras. That could be a factor. Without taking some measurements and sectioning both bullets, I can't really say.

EDIT: I pondered it over lunch and my best guess is that the rifling has more difficulty biting into the lighter jacket (more deflection) and the regular barrel isn't putting as good of a spin on the bullet. In any case, the Sierras shot better in both the regular barrels and the tight bore one than the Noslers did in either.

Kris
 
Last edited:
peterdobson said:
The crotchety Paul Reibin concurs with clatartar. J.Marshall, NS, a longtime TR shooter and gunsmith, the oldest person to qualify for second stage Bisley, says "no need for for tight barrels".
Click to expand...

Johnny was/is the oldest person to shoot in the Queen's Final (3rd stage)
 
You must log in or register to reply here.
Back
Top Bottom