Loading for a new barrel

[TTE]

Edit :
Read the replies, perhaps I am not being very clear in my question.

IF and WHEN the barrel speeds up, will a max load I find in my initial load testing become an over pressure load when the barrel speeds up ?
Example - say I have flattened primers at 50.0 grains with my first trip to the range. No flattened primers at 49.5 grains. Will that 49.5 grain load become an over pressure load later, if and when the barrel speeds up ?

edit:
With a starting load working up in .5 increments of powder weight, I will certainly find/get to max pressure within 25 rounds.
will the load become over pressured as the barrel speeds up ?
- - - - - - - - - - - -
Had a 35 Whelen Douglas barrel put on a hunting rifle.
Read an article that said with a new barrel velocities would be slow. And as the barrel speeds up, a load that was close to maximum when the barrel was new, would become an over pressure load. I never heard that before.
True or just internet BS ?

 

[6.5 forever]

I generally plan on fire forming 100 cases with a moderate load. By then the barrel is ready for load testing so I shouldn't have any speedup problems.

 

[KMW 1954]

I shoot with a group that shoot competitively that are changing barrels at least once a year. They all state their loads speed up and it effects accuracy but never heard one state if presents a pressure problem.

 

[MGYSGT]

Why would you go straight to Max Load. Start in the middle and see where it shoots the gest group

 

[demarpaint1]

Why would you go straight to Max Load. Start in the middle and see where it shoots the gest group

That's what I've been doing.

 

[TTE]

Why would you go straight to Max Load. Start in the middle and see where it shoots the gest group

Was not planning on going straight to a max load.
Start low and work up.
My question was will the higher loads become over pressured as the barrel speeds up ...... e.g. If I put 25 - 30 rounds through it and come close to what would be a max load, when the barrel speeds up would that load become an over pressure load.

edit:
With a starting load working up in .5 increments of powder weight, I will certainly find/get to max pressure within 25 rounds.
I never shoot very close to max pressure anyway, always 1 - 1 1/2 grains under max is where I usually find the best accuracy. However with a 1 to 1 1/2 grains under max, will the load become over pressured as the barrel speeds up ?

 

[danny]

Had a 35 Whelen Douglas barrel put on a hunting rifle.
Read an article that said with a new barrel velocities would be slow. And as the barrel speeds up, a load that was close to maximum when the barrel was new, would become an over pressure load. I never heard that before.
True or just internet BS ?

That sounds more like stupid to me. IF, and that's if the loads start speeding up, it's because barrel friction on the projectile has lowered, or the throat has worn (which will take a while) and those changes will lower the pressure on the load. Remember this, Weatherby ran long throats in their barrels so that they could be sure to get their magical velocities without the loads being over pressure.

Danny

 

[Rickhem]

Was not planning on going straight to a max load.
Start low and work up.
My question was will the higher loads become over pressured as the barrel speeds up ...... e.g. If I put 25 - 30 rounds through it and come close to what would be a max load, when the barrel speeds up would that load become an over pressure load.

edit:
With a starting load working up in .5 increments of powder weight, I will certainly find/get to max pressure within 25 rounds.
I never shoot very close to max pressure anyway, always 1 - 1 1/2 grains under max is where I usually find the best accuracy. However with a 1 to 1 1/2 grains under max, will the load become over pressured as the barrel speeds up ?

This goes contrary to what my thought process and logic seem to indicate. I'd think that the new barrel would be the one that would generate the most pressure with a given load, due to it not having been through the "smoothing" that happens with the first bullets being pushed through it. (lapped barrels aside) Maybe an exceedingly rough barrel could build up enough copper fouling to cause an increase in pressure, but I'd think that would be an anomaly, and you'd notice that in poor groups and flat or cratered primers too.

Sounds like maybe there was more to that original claim that explained why someone thought that. I, for one, would be interested in hearing why they thought loads would gradually become over-pressure as the barrel was used more and more.

 

[KMW 1954]

My question was will the higher loads become over pressured as the barrel speeds up ...... e.g. If I put 25 - 30 rounds through it and come close to what would be a max load, when the barrel speeds up would that load become an over pressure load.

None of these people I mention are ever shooting near max loads. Seems they all find best accuracy well below max. But again, they are not loading for max speed, they load for max accuracy.

 

[bks22345]

There are articles everywhere on this website that discuss barrel speed up.

 

[TTE]

There are articles everywhere on this website that discuss barrel speed up.

Yes there are, I read most of them. However, none deal directly with my question

 

[searcher]

I know nothing of your caliber, but my own experiences, I do believe there is validity to new barrels speeding up - but that is only a temporary phenomenon. I've never had a barrel chrono more than 50 FPS since the first shot fired. Fron that point on - it is a slow, gradual decline. Every barrel is different, too.

 

[danny]

This goes contrary to what my thought process and logic seem to indicate. I'd think that the new barrel would be the one that would generate the most pressure with a given load, due to it not having been through the "smoothing" that happens with the first bullets being pushed through it. (lapped barrels aside)

That is exactly what I think.

Danny

 

[Evan]

I have a big pile of old, burned out barrels for my BR rifles and none of them did what you describe. They all sped up in the first hundred or so rounds but, if anything, pressure dropped in that time and they could take a little more once the speed stabilized.

 

[Bill Norris]

I have a big pile of old, burned out barrels for my BR rifles and none of them did what you describe. They all sped up in the first hundred or so rounds but, if anything, pressure dropped in that time and they could take a little more once the speed stabilized.

Seems to me as the barrel becomes more polished and smoothed by the first 100 or so rounds down it then the bullet would move more freely and the load could stand a touch more powder as well.

 

[mgunderson]

Barrels can and do speed up. The lapping is better than it was 20 years ago and the speed changes are less than they used to be or maybe it was just our chronograph error is less.
I expect a pressure changed that was observed is likely due to something else like fore formed brass or temperature.

Sure there is likely some combo that behaves with increases pressure, but it wouldn't be common.

 

[Liven The Dream]

Was not planning on going straight to a max load.
Start low and work up.
My question was will the higher loads become over pressured as the barrel speeds up ...... e.g. If I put 25 - 30 rounds through it and come close to what would be a max load, when the barrel speeds up would that load become an over pressure load.

edit:
With a starting load working up in .5 increments of powder weight, I will certainly find/get to max pressure within 25 rounds.
I never shoot very close to max pressure anyway, always 1 - 1 1/2 grains under max is where I usually find the best accuracy. However with a 1 to 1 1/2 grains under max, will the load become over pressured as the barrel speeds up ?

Could if you get a Carbon Ring ???

 

[urbanrifleman]

Weather getting hotter most likely.

 

[boltfluter]

Yes there are, I read most of them. However, none deal directly with my question

It is a real thing and does happen. I believe as the bore laps in or smoothes out you get a better seal on the bullet and pressure definitely goes up. Less blow by if you will. My 6 x 47 Lapua is a great example. Worked up a great load in about 25 rounds/Brux barrel. Absolute tac driver of a load. 50 rounds later it is now a nuclear load, way over pressure. Gonna rework the load shortly. So yes, it does happen and is a real thing.
Paul

 

[SKWERLZ]

I generally plan on fire forming 100 cases with a moderate load. By then the barrel is ready for load testing so I shouldn't have any speedup problems.

This is what I do as well