Hi
Has anybody expierence with loading .223 subsonic or nearly subsonic ?
I was thinking N32C for that purpose. Any better ideas?
Mihkel
It can be done but is a hassle. A 22lr rimfire rifle is a much more usefull idea in this caliber class.
N32C is probably the best powder there is for that purpose. However muzzle velocity variation is going to be the problem with jacketed bullets. Don't even consider using jacket bullets with long barrel but if your barrel is short you could do with coatings like moly etc... It's easier to get low velocity spread with lead bullets but those are not usually as accurate as jacketed ones.
As HJu suggested 22 lr. is the easy way to go...
Barrel is 16" 1:10 twist.
Yeah, that's pretty short but not short enough that jacket bullets wouldn't slow down in the barrel. So use of some kind of lubricant is recommended.
You can use this calculator to estimate which bullets would be stable:
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
It's just for estimating gyroscopic stability factor for supersonic speeds. For more accurate stability calculation you actually need to use different approximation formula and consider dynamic stability also. This is where it gets complicated. However experience has shown that when using abovementioned calculator SG:s higher than 2 are usually stable for subsonic speeds at least for short ranges. There are of cource exceptions but if the formula shows SG below 2 then the bullet is probably not even worth testing. Yet for subsonic use stability should always be test fired.