View Full Version : Low velocity on first shot
03-02-2009, 12:00 PM
I have not shot cast bullets in rifles until now. The temperature was 30 F. Two guns were used both 9.3x72r. The guns were allowed to cool between strings, but were not cleaned. The first shot was always the low velocity shot and by 150 to 250 ft/sec. below the next lowest shot. I only shot 5 shot strings. Always the first shot was low and the next 4 were closeer together in velocity to each other than to the first shot. I want to try this at about 70 to 80 F and will wait for warnmer weather. Does anybody know if this is usal?
03-02-2009, 12:49 PM
I grew up in Michigan and we always carried our ammo in an inner pocket during the cold days. Possible your load(powder) is temperature sensitive. Some powders do not ignite or burn as well when cold. By firing that first round the chamber warms up enough to transfer some of that heat to the next cartrige before firing.
I once had a Marlin miss fire during some cold days. There was a tad of grease in the firing pin way and the first hammer strike would get it loose enough to fire on the second wack. But I do not think that is your problem.
God bless you.
03-02-2009, 02:40 PM
What was your load? might be the first shot is powder away from primer and the following powder is closer to the primer.
03-02-2009, 03:15 PM
Was the barrel clean and lubed for each first shot? That is why you should always fire a fouler or two before shooting groups.
03-02-2009, 03:25 PM
The load was 30 gr IMR3031. Fill about 1/2 the case, but I don't think it would be different for each first shot. I did 7 strings of 5 shots each.
The guns were not cleaned at the range. I had shot them before using the chrono.
I have not seen this with jacked bullets.
03-04-2009, 08:16 AM
your jacketed loads don't have cold lube in the bbl and ..
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