TECHNICAL ADVICE FROM THE GURU
LETTER OF THE MONTH
Accuracy From Hot and Cold Barrels
Q I’ve been told that when shooting over a chronograph, a hot barrel makes no difference to recorded velocities. I have also heard that, in theory, if a barrel gets hot after a number of rounds, the round in the chamber will heat up and produce more velocity and may not shoot into the same group as a cooler barrel. I have been letting the barrel cool down when shooting groups for accuracy. Is one way better than the other?
– Dave Collins
A Some rifles shoot just as tight groups from a hot barrel as a cool one, but in my experience light sporter barrels are more prone to tossing bullets outside the original group. My Kimber .25-06 does this. It will group the first three shots in 3/4”, but by then the light barrel is warming up. The next two shots group within 1/2” but now the barrel has really gotten hot and the sixth shot will land about 1-1/2” to the right. For accuracy purposes, it is wise to allow the barrel to cool between groups.
The Cause Is Barrel Vibration
Q For a quite a while now I've been using a 180gn bullet in my
