Quote:
Originally Posted by Medic650
I'm having trouble getting my velocity to be consistant. I loaded 50 rds today with 168gr bthp on top of 1680 powder. I checked several rounds and was within a 1/10th gain on my powder charge. I had up 347fps extreme spread. I'm using a Dillon 550 and Reminton 223 brass. I'm loading for subsonic. Do I need to trickle charge my powder for each round?
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There is a possibilty you may be overlooking completely. I had an extreme case of velocity variation with a 300 whisper I was experimenting with. What calcultated to be a 900 fps load when fired left the bullet still sitting in the chamber though there was a loud report as the propellant went out of the barrrel. That firearm was a TC Contender using 221 brass and if memory serves me the bullets were 168 SMKs. I do remember though they were about 0.1" off of the lands. I don't know if this is your problem but it's worth checking.
If the bullet is seated too far back in the case, a large amount of the propellant gas can go around the bullet and out the barrel before the bullet moves forward far enough to seal against the lands. My suggestion is to move the bullet forward far enough to just seat on the lands. Depending on your chamber and the bullet shape you use that may not be practical. If the bullet won't reach the lands choose a different bullet which will touch the lands. Yes touching the lands and/or using a heavier bullet will produce higher pressure so work up a new load carefully.
A few tenths of a grain in powder weight nor a couple of grain in bullet weight cannot account for a 35% velocity variation. A 35% drop in velocity requires about a 50% loss of propellant energy being transferred to the bullet.
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