First Shot after a brake always faster

[Blacktornado]

I have a new FOpen class gun , 300 WSM, I have 120 rounds on it and it happens something very strange. I have a certain experience but it never happened before. I'm fouling my barrel first and then I have five shots groups and between two groups I stop for 4-5 minutes to cool down a little the barrel . The first shot of the new group is always 30fps faster than the others . Others 4 shots are grouping great but the first one not . Very strange . Did you have similar experience ? Thanks

 

[Clancy]

I bet it’s cooking in the chamber while you’re preparing to fire. I don’t ever chamber a round until I’m ready to put it on target.

 

[Blacktornado]

Me too . No way of cooking it . When I close the bolt I shoot right away

 

[BartsBullets]

I have a new FOpen class gun , 300 WSM, I have 120 rounds on it and it happens something very strange. I have a certain experience but it never happened before. I'm fouling my barrel first and then I have five shots groups and between two groups I stop for 4-5 minutes to cool down a little the barrel . The first shot of the new group is always 30fps faster than the others . Others 4 shots are grouping great but the first one not . Very strange . Did you have similar experience ? Thanks

Yes, I’ve seen this myself. It’s got something to do with how long the barrels sits and cools down between groups/shots. Usually it’s slower but there’s a break over point where it comes out significantly faster. I avoid it by firing a heater round before starting a group. But what you’re seeing is definitely a thing.

Bart

 

[Fuj]

I've seen it go both ways. If I let the barrel cool a bit, I'll fire a sighter and
maybe a second before starting the next group.

 

[antunRC]

I have a new FOpen class gun , 300 WSM, I have 120 rounds on it and it happens something very strange. I have a certain experience but it never happened before. I'm fouling my barrel first and then I have five shots groups and between two groups I stop for 4-5 minutes to cool down a little the barrel . The first shot of the new group is always 30fps faster than the others . Others 4 shots are grouping great but the first one not . Very strange . Did you have similar experience ? Thanks

I’ve seen that too, and I don’t like it. In my case it was happening when I seated the bullets into the lands, but it might not necessarily be related to that. Something is creating extra pressure on the first shot. My guess is that the powder may not be 100% burned, or it leaves something in the barrel that adds a bit of pressure for the next round. But who knows. Maybe even changing neck tension could help.

 

[RDavies]

Yes this is common. When you take a break for a while and the barrel cools, the fouling hardens and it takes more pressure for the bullet to start moving down the barrel which increases pressure on the first shot.