Can a barrel get faster?

[Jay Christopherson]

Ok, maybe this is a stupid question, but...

Is it possible for a new barrel to get faster after some use? I noticed that loads that I have previously used are running quite a bit hotter now, even accounting for temperature swings. For example, I just ran twenty shots at the range (65 deg. F) with what is my finalized load- 33.7gr. RL-15, 107SMK, CCI450.

Previously, in various load tests, this particular load would run about 2955 fps in my rifle. Looking back at my range log, this is confirmed in at least 3 separate range sessions. This time out, it averaged out around 3085 fps. These are the same primers (same lot even), same powder (still working on the same jug), and same bullets. Cases have 4 firings on them.

Looking back at results from different loads, it looks like velocities have creeped since at around 150 rounds through the barrel. I can't account for it. I've been super careful about loading powder lately and my E.S.'s are pretty good, so I don't think I am measuring out the powder wrong.

I *have* gotten a lot better about my loading practices in the last month or so, so maybe I was measuring light in earlier sessions, but I just can't imagine I was that sloppy 2 or 3 times in a row before this. Even in those sessions, my E.S.'s were not very high, although somewhat higher than now.

Anyhow, this whole long post is basically me wanting to know if it's possible (if it's been an experienced phenomenon) for a barrel to pick up velocity after it's been worked in.

 

[fdshuster]

My thoughts, without any way of proving it would be yes. Firing the jacketed bullets down the bore will remove any slight roughness and inconsistancies left from when it was new/ unfired. So the bore is smoother resulting in less drag on the bullet. I'd like to hear Kevin Thomas's opinion on this one. You did not mention the barrel: custom or factory, and if it's a factory then I believe my theory (and that's all it is) would be even more valid.

 

[ericskennard]

Yes they can but usually after the first 150 to 200 rounds. However you said something magic with the RL15. It is very tempurature sensitive. The same weight loaded and shot in the cold will show pressure signs once you shoot in the heat of summer.

 

[Kenny474]

Pretty much every new rifle or barrel I have owned since I bought a chrono has gained velocity as the round count has gone up on the barrel, usually stopping at around the 200 round mark. The factory barrels have gained far more, while the custom barrel has been minimal.

Carbon fouling or a rise in temperature can cause the velocity to rise as well.

 

[Jay Christopherson]

It's a Broughton 5C chambered for 6 Dasher. I am definitely aware of the temperature sensitivity of RL-15, but it was 65deg. at the time of shooting, which is only about 5 - 8 degrees higher than the other recorded sessions at that load of 33.7. I don't see a 5 - 8 degree temperature swing adding 130fps by itself and I was careful not leave the loaded rounds out in the sun or anything while shooting.

These were also the first shots out of a squeaky clean barrel- as Kenny474 mentions, I do usually see few fps gain after the barrel fouls, but I don't think that was the case here.

 

[blawton]

Most barrels will shoot faster the more you shoot them up untill a point. I have seen them gain very little MV to 125 FPS in extreme cases but it doesnt just happen quickly. It will take usually 75 to 200 rounds for this to happen.