Barrel Speed during reloading

[jdmecomber]

There are plenty of documented cases of barrels that speed up until you reach 100-150 rounds. We experienced it at around 70 rounds in our current project. We need to use almost a grain lower in powder to get the same speed. We have shot 85 rounds now.

How do others deal with this?

 

[SealT5]

Depending on the cartridge I usually don't start "load development" until I get a hundred or more rounds down range. Again that is all subjective and case by case. But with that said I do generally locate a node as well as what bullet and jump/jam the barrel will like.

 

[jdmecomber]

Depending on the cartridge I usually don't start "load development" until I get a hundred or more rounds down range. Again that is all subjective and case by case. But with that said I do generally locate a node as well as what bullet and jump/jam the barrel will like.

That makes sense. I guess you could always relocate your node like we are doing.

 

[ShtrRdy]

Also, it seems once fired brass will give a little higher velocity than new brass.

 

[jdmecomber]

Also, it seems once fired brass will give a little higher velocity than new brass.

We just tested this yesterday, it was about 15 fps higher for once fired, so it wasn't that much difference

 

[ShtrRdy]

Maybe it depends on the cartridge, and possibly powder, primer, bullet? On the 6mm Creedmoor I saw about 40 fps difference.

 

[jdmecomber]

Maybe it depends on the cartridge, and possibly powder, primer, bullet? On the 6mm Creedmoor I saw about 40 fps difference.

for sure, probably lots of variables

 

[Deviant]

Maybe it depends on the cartridge, and possibly powder, primer, bullet? On the 6mm Creedmoor I saw about 40 fps difference.

I saw 25 fps with my creedmoor. I always fire form 100 rounds of brass and wait for the barrel to speed up before any load development. I have had some major issues with my 28 Nosler and virgin brass and had to start over.

 

[jdmecomber]

You always hear ladder tests and ocw tests, but not many people wait till 100/150 rounds. Good to see I am not crazy. .

I would assume a node is the same, it wouldn't matter if it's in the first 100 or the second 100. But you could waste 12 rounds like we did two days ago.

We loaded up 3 four shot groups right around the node. However they were 50-60 fps faster so it was kind of a waste, but at least still getting the first 100 down the barrel.

 

[nmbarta]

I use the first 100 shots for fire forming and initial load development.
Usually by the time this is done, all I have left to do is tweak the charge a little bit to get to the velocity node I liked best. 100 pieces of once fired brass is a good way to start on a fresh barrel with 100 rounds down it. Depending on what cartridge it is, I might go 200 here. (longer barrel life rifles) 100 pieces of good brass might take the barrel out of some rifles, so no need to form any more than that on those ones.

 

[TG-5150]

Until joining this forum, I had zero knowledge of new barrels speeding up. I also have always bought factory ammo to build my brass supply.
Having an Ackley chamber, I used this as a chance to fire form.
The comment about virgin brass not being as fast as once fired. What causes this, carbon buildup?

 

[Rhovee]

It depends on the barrel. my experience as follows:
Benchmark 6.5 WSM 120 FPS
Rock Creek 28 Nosler 70 FPS
Broughton 7 saum 0 FPS
Proof 30/28 Nosler 15 FPS
Broughton 338 edge 60 FPS
Broughton 30/28 15 FPS

I start working on things right away after break in and cleaning. You can find seating depth. You may or may not have to reduce powder charge. I haven't noticed it happening right away, but more gradual. I shoot every shot and record velocity over a Labradar. I believe that cleaning the rifle well and removing copper after each 20-25 rounds seem to bring on any velocity change faster. Depending on how your headspace was cut during rifle chambering determines how much your virgin vs fired brass velocity will change. I measure volume of virgin and fired to see the difference and load accordingly. Biggest difference that i have seen is with belted magnums and velocity increase on fired brass..

 

[jdmecomber]

Until joining this forum, I had zero knowledge of new barrels speeding up. I also have always bought factory ammo to build my brass supply.
Having an Ackley chamber, I used this as a chance to fire form.
The comment about virgin brass not being as fast as once fired. What causes this, carbon buildup

It depends on the barrel. my experience as follows:
Benchmark 6.5 WSM 120 FPS
Rock Creek 28 Nosler 70 FPS
Broughton 7 saum 0 FPS
Proof 30/28 Nosler 15 FPS
Broughton 338 edge 60 FPS
Broughton 30/28 15 FPS

I start working on things right away after break in and cleaning. You can find seating depth. You may or may not have to reduce powder charge. I haven't noticed it happening right away, but more gradual. I shoot every shot and record velocity over a Labradar. I believe that cleaning the rifle well and removing copper after each 20-25 rounds seem to bring on any velocity change faster. Depending on how your headspace was cut during rifle chambering determines how much your virgin vs fired brass velocity will change. I measure volume of virgin and fired to see the difference and load accordingly. Biggest difference that i have seen is with belted magnums and velocity increase on fired brass..

That's very neat, looks like broughton maybe is doing something different???

 

[jdmecomber]

Until joining this forum, I had zero knowledge of new barrels speeding up. I also have always bought factory ammo to build my brass supply.
Having an Ackley chamber, I used this as a chance to fire form.
The comment about virgin brass not being as fast as once fired. What causes this, carbon buildup?

My guess is virgin brass is usually headspaced .020-.030 from what it should be. I would assume all the pressure is used to fireform that brass, so the speed is slower. Fireformed brass is already expanded, so the pressure is instant and faster