Loading subsonic 308 win

[dbledoc]

I am going to have spine surgery in 2 weeks and anticipate having some free time to play around at my reloading bench. I reload 300BO for my gas guns, but I don’t have a bolt action 300 BO. I do have an 18inch bolt action 308 with a suppressor mount, hence, I am debating developing some subsonic loads for it. Covid really devastated my practice income so I don’t wont to spend any of my cash reserves. I have lots of cases and WLRP (not many SRP left).

So, I did a search online and found that the most common powder used is Trail boss because it seams to fill the case, I have bullets I use for 300 BO (Hornady 208 gr AMAX and a few 220 grain Sierra, I also have some coated lead bullets I got from TomKat). What is the collective experience with different powders for these loads?

 

[Melnic]

I used a 150gr sierra pro hunter flat base which is a lead soft point and 10gr Trailboss.
I know that in the reloading site on Hodgdon, it shows the velocity of that load just over subsonic but I have a threaded 18" barrel and with the suppressor, it sounds like an airsoft gun.
My notes show OAL 2.795" and chrono at 980fps
Hodgdon website shows min OAL 2.800" but that is a boat tail

 

[Sundazes]

I bought some 308 subs from Tomcatt a while back. While very quiet, the bullet drop was incredible at 150-200. I don't know the load that was used, but I consider them a novelty.

Good luck on your surgery Doc!

 

[dbledoc]

I bought some 308 subs from Tomcatt a while back. While very quiet, the bullet drop was incredible at 150-200. I don't know the load that was used, but I consider them a novelty.

Good luck on your surgery Doc!

I am assuming the bullet drop should be similar to 300 BO. Same type of bullet and same velocities.

 

[E.Shell]

I am assuming the bullet drop should be similar to 300 BO. Same type of bullet and same velocities.

It's ALL about time of flight. Sub-sonic is sub-sonic, and at sub-sonic speeds, BC becomes less important as well...

 

[lazarus]

It's ALL about time of flight. Sub-sonic is sub-sonic, and at sub-sonic speeds, BC becomes less important as well...

Sorta. I mean, a 220gr .308 caliber bullet is still going to have shorter time of flight and less drop and wind drift with a MV of 1000fps than a 40gr .223 caliber 22lr with an MV of 1000fps.

Either way, practical ranges are maybe 150yds and at that, it’s very much a rainbow trajectory.

You can generally use most pistol powders if you are careful. Don’t just start messing with it. Certainly look for load data. I’ve found 308 subsonic load data for 150 flat base up through 220gr for bullseye and CFE223 when looking (what I have handy).

 

[Balzer94]

I have a 26” bolt 308 with a suppressor. 10 grains of trailboss puts me just under the speed of sound with it jumping over every once in a while. I’ve used the 200-220gr Sierra match kings and hornady eld-x. Her recently I’ve been practicing with berrys 300blk bullets. My groups aren’t as tight as the Sierras or Hornadys but for the price they work just fine.

With the sierras I was able to keep a nice 1” group at 100yds which I’m happy with for my shooting skills.

 

[dbledoc]

I should clarify, I am loading these just for the fun of it. I have everything but the powder and figured why not. I have a surplus of LRP, 100’s of 308 cases, and a supply of bullets. I shoot at the AGC so really limited to 100-200 yards.

 

[alucard0822]

Be sure to shoot a few without the can first, even a "fast" 1:10 308 twist can keyhole with some heavy bullets that 300BO's faster twist handles just fine. I played around with 308subs, and haven't had any issues, but have heard enough people that got baffle strikes they kinda make me nervous, so I usually use a 9mm can instead of a 30cal one.

 

[Speed3]

This is on my list to load for when the snow melts. I have some 150gr and 180gr bullets. Flat base bullets will be your friend for this application. Trail boss is the go to powder of you can find it.

Also, the trick is to start above sound barrier and work down. Going too light have be dangerous.

 

[punchBIGholes]

I load a 200 gr lapua boat tail over 10.8 gr of trail boss with a WLRP I can’t recall the COAL but I have great results out of a 22” 1:10” barrel. Your POI will seem to drop like a rock at sub velocities, so keep that in mind


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