MeccaOz wrote:Hi gurus, is there anyway to find out how much powder is being burnt in a certain barrel. For example say I'm using AR2208 in my .223 and the barrel has been chopped off and is now 18" long, how would I find out how much powder from my old loads was being wasted, is there a formula or ballistics program I could use ?
Nope no program is available only trial and error, other than a chronograph the best way is to fire at night, you will get a visual of what is going on.(I know it sounds rough but I did it with a Jungle carbine and the results were surprisingly similar to what the chronoggraph indicated.
Just what I have found:
You still need to load at the same rate as before, there is only minimal efficiency to be gained by short loading to suit.
Heavier pills seem to get going better in short barrels with medium powder (2208 and 174grain projectiles in .303) but lighter pills run better with a faster powder(2206 and 125 grainers in .303).
The pressures don't seem to be any less in a shorter barrel but if you go to a longer twist they seem to reduce slightly.
Suck it and see really, I was still able to shoot successfully at 600yards even with the Jungle carbine, it generally is not as much a reduction in velocity as people think.
Rule of thumb in a .308 is 30fps less per inch removed with the same powder charge, so if you are shooting at 1000yards it may make the difference between staying supersonic or not but at 500 it will just mean a small adjustment for elevation.
The .223 is less sensitive to being docked, simply by the one docking I have done with a .223 barrel which in itself is not proof positive. If you do experiment let us all know the results as I would be very keen to know.