Why do my velocities climb

moosehunter

moosehunter

Regular
Rating - 100%
2   0   0
Location
Prince George
After careful and meticulously prepping my 300wm brass and powder charging with my RCBS chargemaster my velocity will stabilize for 10 or so rounds. Then they will climb sometimes to as much as 100fps or more. Kreiger SS match barrel no copper or carbon fouling. Any ideas?
 
So you're saying that when your rifle is nice and clean, with a fresh set of handloads your velocity will hold steady for the first 10 or so rounds, then start climbing? If so, how many rounds does it take for things to level off again? Is the increase in velocity consistent - that is, does each round go a bit faster than the last until you hit a plateau?
 
How many rounds through the barrel? I've found in general things aren't very stable and will speed up quite a bit over the first 100-150. After that it usually just takes 1 or 2 rounds after cleaning to get stable velocities
 
Keep shooting, new barrels often pick up speed as they break in, then velocity should stabilize.

This is assuming you aren’t shooting really rapid fire, too. :)
 
good guess
when shooting in the cold also a new round chambered will pick up ambient temp, longer it is chambered the warmer it will shoot
 
I don’t fire more than 3 then cool it down. I used to do 10 shot strings for unlimited class 1000yds. I was amazed how quickly it destroyed the throat. No more of that.
 
I don’t see how continued fowling would be the issue. Cold clean shot is 1/2 minute low then on the mark after that unti the velocity starts climbing. Cleanup is 10 passes with a nylon brush soaked in hoppes one pass with a patch soaked in hoppes then 2 clean patches and they come out clean. Borescope shows nothing in the barrel.
 
Sure, it's possible that a 25 year old Shooting Chrony can get erratic. You can pick up Labradars for pretty cheap these days and they work just fine if you want to upgrade your velocity measuring instruments. Fouling has nothing to do with it.

But Post #3 And post #7 have your most likely answer.
 
My experience differs from things you have said here, and I would like to see photo/video evidence from the bore scope.

Specifically: immediately before cleaning, capture from the start of the chamber to 12" into the barrel - pause often enough that the video is clear. Then again right after cleaning.
 
There are so many variables to consider - ambient temp, barrel temp, natural variations even between "identical loads", chrony margin of error, etc. Then there's sample size.

Even with all of that considered, if these observations are from 2-3 outings of a few shots each time, you can't say it's a trend.
 
I have found most velocities lost a little as the barrel loosened up, but with R-25 powder each shot in a three shot string increased. In that cartridge, that powder was a reject. I used R-25 in another cartridge with no issues.
 
You must log in or register to reply here.
Back
Top Bottom