Velocity changes with barrel heat in my .223?

[diebythebow]

Just trying to understand this??? So My Rem 700 VS .223 W/26" barrel picks up velocity as the barrel gets hotter, I verified this with 2 different chrono's now & tried both varget & benchmark powders with same 53gr vmax bullets on multiple occations while developing accurate handloads & same results. As i shoot over the chrono the velocity will increase 50fps or so usually after the first 5-8 shots out of a cold bore POI & groups @ 100 yds remain the same. So today my most accurate load of varget 27.3gr first handful of shots 3,250-60 fps as the shooting progressed its goes 3,280-3,308 fps & stayed in that range. What Gives???

 

[Quickoz]

How quick are you shooting the groups?

How well is the barrel clean? Verifyed with borescope?

 

[diebythebow]

My routine has been the same, I clean the barrel with wipeout & always run fowlers thru the barrel to be sure the bore is ready for chrono & accuracy data. I dont time my five shot groups but I'd say I take my time settle in & slowly squeeze shots off. So my finding have been the velocity rises continuously for first half dozen or so rounds then stabilizes into its heated fps range. I haven't had anyone take a peek with a bore scope. I'll try some of the recommendations next time at the gun club. Mabey I need to bring a propane torch everywhere to heat up my barrel! Lol

 

[dkhunt14]

I have seen some barrels take as high as 10 shots or more to foul. Depending on the barrel and how it is cleaned. Most of mine settle in 2 to 3 but they are custom hand lapped barrels. gstaylorg gave you some good advice. matt