HELP velocity difference

grampyg · #1 10-21-2011, 04:49 PM

I have been reloading for years but I have never had use of a chronograph. Well I have use of one and I am getting 100fps or so diff. I use a rcbs 10-10 beam scale and weight out each charge. Is this common or am I doing something wrong. I know there is alot more to it beside the charge but I thought I should be closer than that. This load is 36grs imr 4895 with rem primers. I have been neck sizing. Hornady 100gr bullets Rifle is a older 20 inch remington 700 in 243. But it shoots like a dream with about anything I put in it. Sorry If I rambled on Thanks Rick

royinidaho · #2 10-21-2011, 11:33 PM

Hmmmmmm,

Shoot at a target at least 400 yards away and see if vertical stringing is apparent.

Chrono each shot. This should tell you something.

If groups show no vertical stringing then the chrony is suspect.

Otherwise it may well be the powder charge and primer combination.

If the load is on the very very mild size, that is, not much powder in the case, powder geometry differences may be the problem. I have absolutely no feel for the 243 cartridge and 4895 thus I don't have any idea of how hot your load is.

100 fps is a quite large extreme spread. Unheard of around my place.

Just some thoughts......

Mikecr · #3 10-22-2011, 09:32 AM

100fps difference in what you thought velocities should be? Or ES?

CRNA · #4 10-22-2011, 09:42 AM

Was the chrony in direct sun? My chrony will give all kinds of crazy numbers if it's in direct light. I nearly pulled my hair out with that thing once. I found that if I shot in indirect light my ES shrank to the teens with some of my loads. Never more than 20s for all of my loads. Before you go to changing everything around trying to re-invent the wheel, then try shooting through that chrony on a perfectly overcast day. When I say overcast, I don't mean passing clouds. Passing clouds I found to be the worst-case scenario because the light level is varying. Shoot on a day it looks like the bottom is getting ready to drop out of it and then report back. I bet you will find that your loads magically improve without touching them.