308 subsonic

[Jimbeaux82]

I will be experimenting with 308 Win , 220 gr subsonic loads. Right now the only pistol powders I have available are Longshot and H110. has anyone had success using either powder? If not , what other powders have you had success with?

Thanks

Jimbeaux

 

[RL338]

I never shot 308 sub but did in other calibers and TrailBoss is what I used. With 220s barrel twist might need to be faster to stabilize bullet.
Good luck with your project.

 

[JD338]

The Nosler 220 gr BT was designed for the 300 Blackout velocities. Would be interesting in the 308 Win if it will stabilize.

JD338

 

[Jimbeaux82]

Well you guys are no fun! I might just have to buy a dedicated 300 BO bolt rifle!

 

[JD338]

They are fun!
Effective too, I shot a deer with mine a few years ago. Used the 125 gr BT and pinned it to the ground.

JD338

 

[jimbires]

lately I've only been using H4895 for reduced loads . I have messed with light bullets and light loads in a 308. I used IMR4198 . here is the info I have . it looks like you should be able to start at 24.0 and work up towards 28.0 . I've included some lighter bullets , so you can see the powder charge doesn't change much .

125 / 130 grain




180 grain





200 grain

 

[Guy Miner]

Funny, am working on an article about Subsonic 308's right now!

At this point I'd recommend looking at H4895 or Trail Boss and heavy bullets. Make sure your rifle has a fast enough twist to stabilize the bullet used.

Guy

 

[Jimbeaux82]

I guess great minds think alike! Lol. May have to drop to a 200 gr or even 180 gr to stabilize. I was hoping to use 220 gr BT’s but now understand they don’t stabilize in normal 308 twists. Only data I’ve seen for subs is with Trailboss. Maybe I can locate some. Yesterday I ordered a Ruger American rifle in 300 BO and will play with that as well. What twist rate do I need to stabilize the 220 gr BT?

 

[RL338]

Your new Ruger would have a way faster twist (1:7) will have no problem with 220gr. TrailBoss is impossible to find unless you know someone who has some.

 

[jimbires]

according to quickload the Hornady RN , 220 grain bullet is 1.283" long . the Nosler Partition is 1.370" long . I don't have a 220 grain ballistic tip listed .

here is a link to Berger's twist rate calculator .

https://bergerbullets.com/twist-rate-calculator/




here is a question I have , how slow can you have a jacketed bullet go ?

I seem to remember reading that below a certain speed you should go to a lead bullet , that jacketed bullets could get stuck . I'd have to do some digging on this to try to find what I seem to remember reading .

I've done a fair amount of reduced loads , but never to this low of velocity .

 

[RL338]

Nosler has 220gr load data for 300 BO all subsonic.

 

[Jimbeaux82]

I have an AR 15 in 300 BO. I was able to develop some good subsonic loads for it with 220 gr jacketed bullets and H110 powder. Problem was when I put a suppressor on it it would not cycle reliably with the 220 gr BT's. That is why I am going to a bolt action rifle in 300 BO. Since all of the major ammo companies offer jacketed bullets in subsonic loads for 300 BO, I will assume there is no problem going subsonic with jacketed bullets. I had no issues with bullets getting stuck in barrels with those I reloaded.

I, like you, use H4895 when making reduced loads in the 2000-2400 fps with normal deer calibers and have used the 65% rule successfully. Not sure you can get down to subsonic levels with it.

 

[Guy Miner]

Hodgdon's subsonic load data for the 308 Winchester, using the 190 grain Sub-X bullet:

 

[Jimbeaux82]

Guy,

thanks for the data. I'll be very interested in the results of your latest project on 308 subs!

Jimbeaux