.308 with a 14" twist. What ammo to use?

[Dorset_Dave]

Afternoon all,

I've just picked up my first full bore rifle. It's an FN Mauser action, fitted with a Schultz & Larsen target barrel, all set in a nice (but slightly dinged) Monte Carlo style stock. I paid the whooping sum of £36 at auction for it. But after a little research it appears that an 14" twist is rather uncommon for .308 (1:10 and 1:12 being the norm)
I was wondering if any of you have had any experience with this caliber and twist and could recommend a bullet weight/type that would be suitable for punching paper up to 500m.

Many thanks

Dave

 

[Art Eatman]

Odds are that any bullet longer than a 150-grain won't spin fast enough to be stabilized.

 

[Bart B.]

That twist has been used in 30 inch target barrels shooting 147 to 155 gr bullets very accurate in 800 to 1000 yard matches when the weather is warm. They leave about 3000 fps from 308 cases spinning fast enough to stabilize nicely. The Brits were first to do that back in the 1960's when their fullbore long range target rifles switched from 303 Brit to 7.62 NATO shooting M80 arsenal ammo with 147 gr bullets. 1:13 twist worked better in cool temperatures.

If the barrel is the typical 22 to 25 inch range, 135 grain bullets should do well. Use IMR powders 3031 and 4895 or other stick powders in that burn range. Load them 3000 to 3100 fps for best accuracy.

For comparison, The 30 BR cartridge used in benchrest matches shoots 110 to 120 gr bullets leaving about 3000 fps most accurate from 1:17 or 1:18 twist barres.

 

[Dorset_Dave]

Thanks for the quick replies, I'll measure the barrel length when I get home.

The age of the rifle and the fact I'm in the UK would support your info Bart. Looks like I'll be using lighter ammo in her

 

[Bart B.]

Dave,

One top ranked rifleman on this side of the pond shot 250 grain bullets out of 308 Win cases through a 1:8 twist barrel at 2150 fps. Very accurate and bucked the crosswinds very well.

 

[stoky]

I think you're going to have the best luck with lighter bullets, of the shelf cartridges might be called varmint.
http://kwk.us/twist.htmlhttp://kwk.us/twist.html
might need some algebra
hth

 

[The_Next_Generation]

Dont overlook some heavier options. Ive shot 208gr amax bullets out of a 26" 1:12 at 2550ft/s. You might be surprised by what your rig will do, even with a slower twist.

 

[Sunray]

"...used in 30 inch target barrels..." I wonder if that was what was used in Aussie Sportco barreled target rifles. Those rifles loved IVI crap.
Sounds like an M58E. Made by Schultz & Larsen for the Brit market. How did you determine the twist?

 

[Llama Bob]

I would definitely stay at 155gr. or below. The 150s and 155s may well be marginally stable - OK at higher altitude and/or warmer weather, but prone to tumbling in cold, dense air.

The 125-140gr weight range may serve you better. I'm not sure what's available on your side of the pond, but for a first try at an accuracy load I'd look at the Nosler 140gr custom comp - it's pretty stubby for its weight so it stabilizes well, and has an acceptable BC all things considered.

You can use the berger twist rate calculator to figure out if a given setup will stabilize. I'd shoot for a SG of 1.5+.
http://www.bergerbullets.com/twist-rate-calculator/

I should mention the Berger calculator is pessimistic for tipped or hollow-nose bullets. You can use the JBM calculator for those:

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi