New barrel velocity change

[Boisblancboy]

Does anyone have any experience with their barrel, from new to after break in, increasing velocity with a particular load?

Now I understand that every barrel being different in length, twist, caliber, grooves that there is not one standard. But just interested in hearing what other may have experienced.

 

[Preacher]

Usually a barrel will increase velocity after the wrinkles have been ironed out, and after the cases are formed to that particular chamber....

 

[Steve Blair]

My barrels usually increase up to 200-300 rounds and then stabilize.

 

[Jay Christopherson]

Yep, I've documented every practice round through three barrels (different manufacturers) across three different calibers via chronograph (as well as mapped it in Excel with a graph) and all three showed fairly significant increases in velocity at around 150 - 200 rounds. One at a little over. Once it gets over that increase, it settled down and has been consistent.

I don't even bother varying my powder charge much during load workup until I get past that point.

Edit: Here's an old example from my 6 Dasher. This one shows about 400 rounds in total (last data point), whereas the current graph (that I don't have handy) has a little over 1000:

The powder charge for ALL of these data points, except for the last two, was identical (33.X grains RL-15). You can see how it started under 2950 and then crept up to it's current, stable velocity of about 3040 fps. Some of the variance you see is temp related (I'm tracking velocity vs. temp, as well as round count) here, but there's clearly a slope showing velocity increases that cannot be explained by temperature variance- in fact, the temp only varied about 10 - 15 degrees across the entire set in this graph. Since I have seen this same slope on three brand new barrels, in three different calibers, across three manufacturers, I'm fairly convinced it's something to do with the barrel "settling in".

 

[bricktop]

I would guess then that it's not really a waste of barrel life to fireform the dasher brass using bullets (as opposed to cream of wheat), since the break in is useful.

 

[Boisblancboy]

Jaychris that's some interesting documented information!

 

[Jay Christopherson]

Yeah, I had a hard time with that at first, but I think you are right. I don't use COW anymore- I use a hydro-die to get an almost-there form (mostly so I can shoot without doing the whole false shoulder thing) and then just shoot. The hydro-formed brass does great in matches. I've never felt like I was handicapped by using hydro-formed brass.

I would guess then that it's not really a waste of barrel life to fireform the dasher brass using bullets (as opposed to cream of wheat), since the break in is useful.