308 Win subsonics with Trail Boss

gelandangan · Posted: Sun Sep 13, 2009 4:47 pm Post subject: 308 Win subsonics with Trail Boss

Anyhow, a few months ago I think Dimitri (was that you Mr D?) did mention about subsonic for 308 Winchester.

So just for grin I thought I should try to make a batch of loads.

I use Trail Boss powder and 180gn SMK 2220 projectile.
My rifle is a Ruger 77MKII that were re barrelled to .308 Win using factory Ruger barrel (it was a .243 Win in its previous life)
I measure that the barrel twist rate is about 1 in 10.
It has standard light weight Ruger profile, not heavy barrel.

I loaded batches of 5 from 10.0gn to 11.5gn with variation between batches of 0.3 gn.

Yesterday was an un seasonally warm day of September in Sydney, we hit 32 degree Celcius (thats about 90F, Bushy) in the range.

So here I am expecting groups of 2 - 3 inches in 100 meters..
and getting about 1.5 inch at the extremities of the loads (10gn and 11.5gn),
less than 1 inch for the rest of them, and 0.5 inch clover leaf at 11.2gn Shocked

.
it is definitely a great fun to shoot, almost no noise and recoil (like a 22 magnum)

This rifle usually shoots just a tad under one inch with standard .308 loads !!
Now out of the blue it shoots clover leafs !!! YEAH!!

sfelt · Rookie Member Joined: Aug 21, 2008 Posts: 1

gelandangan,

I used your formula and got sweet results from the 11.2gn of TB w/ 180gn SMK, Remington primers, and Lapua brass. Was running 1060 +- 7 ft per second out of a TC encore 17 inch barrel, with a Coastal 7.62 supressor. Shooting MOA at 100 yards to boot out of a new barrel. Temperature was 38 degrees F and I am 750ft above sea level in GA.

Thank you very much !!

Steve
Very Happy