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Post by Robert on Feb 4, 2011 11:50:58 GMT -5
Using the .308 180gr RN Interlock bullets and Black Hills brass, how many grains of trail boss do I need to use to create an accurate subsonic round?
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Post by jwp6114usmc on Feb 4, 2011 17:05:30 GMT -5
There are a couple variables to keep in mind... But first of all My Disclaimer...
Any data I mention has been field tested through MY rifle, I accept no responsibility for anyone else's actions (or lack of). Read your reloading manual carefully.
Now, what length barrel are you shooting?
What twist rate?
Are you using a suppressor?
knowing all of these things will help me help you.
I have been using Lapua Brass, standard primers, 175gr sierra match king, with 10.5 grains of TB, in a 26" 1/10 twist
barrel, suppressed.
I would be more than happy to give my opinion/advice for your equipment.
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Post by robert on Feb 5, 2011 10:21:48 GMT -5
Hart Barrel is 20" and suppressed with 1/10 twist. I understand you have no responsibility, any advice would be appreciated.
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Post by jwp6114usmc on Feb 5, 2011 11:30:13 GMT -5
If you have a chronograph that will help. I would recommend you start with 10.8 grains of trail boss and work your way from there. I was seeing about 950 fps with 10.5 with a 175gr projectile. In my findings the 180 RN interlock's did not group for crap. but you may haver better luck with your twist.
MOST IMPORTANTLY, while you are cronographing and shooting your first batch, DO NOT USE your suppressor. put up a target at about 25 yards and shoot some at a plain cardboard on a target stand and ensure the rounds are stabilized fully. (i.e. no oblong or sideways holes through the cardboard.
If you don't have a chronograph load them up 0.2 grains higher at a time until you get a supersonic crack and then lower your load by about .3-.4 grains. you want to stay around 1000fps in a normal atmospheric conditions. changes in temperature and altitude can change the point of speed where the round will crack the sound barrier.
Good luck and let me know how it works out...
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Post by robert on Feb 5, 2011 13:41:45 GMT -5
Thank you very much, I will give it a shot!
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Post by jwp6114usmc on Feb 5, 2011 15:07:44 GMT -5
One other thing to keep in mind is when you are shooting sub-sonic rounds is to have a cleanbore. the less powder fouling and even more important coper fouling the less likeley you will be to have one go stupid out of the muzzel. Coper fouling has a greater effect of "bullet upset" on a sub-sonic round than one leaving the muzle at 2600+fps.
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Post by jwp6114usmc on Feb 9, 2011 12:50:34 GMT -5
Thr trick is ... All you gotta do is... NOT BLOW YOURSELF UP!!!!
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