Subsonic load for .308 Win

[l115a3]

I had test loading subsonic round as publish on reloading manual.

8.0 gr of Titegroup with 168 SMK , COAL 2.800" chrono around 1,080 fps




But just wonder my new rifle with tight bore barrel (.299/.308) has a short chamber which measure 168 SMK to touch land with COAL @ 2.760"


So, if I seat my load at 2.750" , thus will increase mv of them?

Is it safe to reduce powder charger lower than 8.0 gr?

 

[Hawk Gunner]

With subsonic loads you want to work down in charge to keep from getting bullet stuck in barrel. I'd keep it where it was and go down in .1 increments.

 

[rjacobs]

you can go as low as you want. Check the barrel after each shot to make sure it exits the barrel.

I'm VERY VERY VERY leery though of running a powder like TG as a subsonic powder in .308. With only 8g you have a fair chance of the flame from the primer going right over the top of the powder charge or getting some weird powder light off because of this.

This(VERY VERY low case fill) is why most people try to run Trail Boss with subs in 308.

 

[biffj]

you can go as low as you want. Check the barrel after each shot to make sure it exits the barrel.

I'm VERY VERY VERY leery though of running a powder like TG as a subsonic powder in .308. With only 8g you have a fair chance of the flame from the primer going right over the top of the powder charge or getting some weird powder light off because of this.

This(VERY VERY low case fill) is why most people try to run Trail Boss with subs in 308.

This is one reason that subsonics in 308 really don't make much sense. If you want to shoot .308 bullets subsonic build a rifle that will shoot them right. Look at the 300 blackout/whisper/fireball etc because it allows the use of a wide range of powders so you can be accurate, quiet and not worry about micro amounts of powder not filling the primer pocket much less the case. The other thing that makes 308 subs a waste of time is the light bullets like the 168. The whole point of shooting subs is maintaining energy on target while reducing velocity to get rid of noise. With most 308 rifles the twist won't allow you to use bullets that make sense due to stability issues......on the other hand to each his own. Reducing below 8 gr of powder is pushing it so do as the others recommended and make sure you have a clear bore after firing. Don't expect the charge to maintain consistent velocity unless you do a little powder dance each and every time to insure the powder is in the back of the case. Hold the rifle muzzle up loaded....shake a bit, lower very slowly and carefully to keep the powder from being tossed forward. It may help a bit but not much.
If you really want to shoot lightweight bullets in a 308 case your best bet is to fill the case with epoxy, lead or something to take up space and leave a path from the primer to the bullet for powder and gas.


Frank

 

[rjacobs]

I agree that .308 subsonic is not the ideal sub platform and 300BLK is light years better. I shoot enough 300BLK.

However if a guy doesnt want to invest in a whole new setup than .308 subs in a bolt are an ok option. I shoot a bunch of .308 subs because I dont really have the $2500 to build up another bolt gun in 300BLK to mirror my .308 bolt so shooting subs out of the .308 is a decent option. I though have a .308 with a 10 twist barrel so I can shoot 220g SMK's out of it. For me subs are more of a fun thing anyway and to really show of what silencers can do. I am sure eventually I will build a 300BLK bolt gun.

 

[woostri]

Read about a trick but haven't tried it in my subsonic .308s yet: load SMK's backwards. Ha! It actually makes perfect sense. Pretty much all long range bullets have Cp in front of cg which is aerodynamically unstable. But the twist stabilizes them gyroscopicly. They have to be pointy to reduce wave drag whilst supersonic and that's what pushes the cg back so far. So... Subsonic bullets don't do well in the stabilization catagory due to lacking the velocity. It helps tremendously to have them at least be aerodynamically stable, which any backwards rifle bullet will be. Since the range of subsonics is only really about 100 yards anyways, the increased drag is of little concern. Like I said I've never tried it but it should work for those of us who do not have a dedicated .300 blk or whisper gun with tight twist. I use the 200 gr Lapua subsonic since it was designed from the ground up to be weight forward. It groups about 1.5 inches at 100 yards and chrony's at 1000fps give or take. My load:

10.5 gr trailboss
200gr Lapua subsonic
RP brass
CCI 250 primer

Oh yeah the trailboss was the other thing. Way safer than any of the pistol/shotgun powders for .308 subs. Around 10 gr pretty much fills the .308 case. Fluffy stuff.

--- aim small miss small ---

 

[winxp_man]

Just spotted this thread. I actually experimented with some sub load. But used waxed lead cast bullets 165-175 cant remember would have to look at some notes for exact grains. But I was able to get them down to 450 FPS with 4 or 5 grains of trail boss and used a magnum primer. Its fun shooting in my bullet catcher in the back yards. just a tab bit louder then a .22 CB short. @ 50 yards I was able to get the groups in at 1" but it has super amounts of power behind it. I would go through a 2x4 pretty easy and tried two 2x4's and it was able to still punch through. Not sure if Op is interested in such info but just putting it out

 

[SNOW]

Trailboss is the way to go. Always better to load "hot" and work your way down to get desired velocity. I load my subs at 1025-1150.