Twin barrel, different load?

[The boogalorian]

I had a custom rifle built in 6x47L. I hadn't loaded for that chambering yet. I knew that I would shoot a few different combos of bullets and powders, so I had (2) barrels chambered when it was made. I just assumed that I would shoot one out testing loads.
Is it a reasonable to assume that a good load in the one barrel with be very close to good in the other barrel? Maybe just minor tweeking?

Same barrel manufacturer, same reamer, same gunsmith. Both done at the same time.

 

[Dud]

By the time you have worn out the first, the throat will be different enough that accurate loads will be different.

Close probably.

 

[Dusty Stevens]

No two women are the same

 

[dmoran]

@1badgoat
Repeatedly it has worked for me, where what I use in one barrel will be very near what works in others.
Have even won 1000-BR matches sharing the same pet-load in two rifles (LT & HV).
Tony Boyer qualifies barrels he may or may not use by how well they shoot one particular petload.
My 2-Cents

 

[The boogalorian]

@dmoran

Thanks for the reply.

So, when I spin on the new barrel should I say adjust the cbto for the same jump/jam and lower the powder charge say 5-10% for break in, then increase the powder charge till I get the same velocity as the previous barrel? (Obviously checking for signs of pressure.)

 

[dmoran]

@1badgoat
That is pretty much how I go at a new barrel; drop back at least 1 full grain from a proven petload and work back up, with all other aspects of the petload being left the same. After refining the powder charge, seating depth is my next tune adjustment. Neck tension after that.
Good Luck

 

[ballisticxlr]

I've built 3x 6XC's on the same reamer after a shooting partner and I burned out a fourth. 1 on an old flat back savage, one on a new savage and one on a howa 1500. All were set up with zero headspace and all on the same brand/model/profile/length of barrel blank. They all shoot within ~10 feet per second of each other and all group similarly well with the same load. I didn't go looking for a load that wouldn't group well, I started with one rifle and built a load that worked on it and then tested it on the others. So, since I didn't do the other side of the data gathering what we have really is low grade anecdote on my data. Nonetheless, all 3 rifles shoot 10 shots into a ragged hole the size of a thumbnail. All 3 get the same velocities and all 3 see pressures climb at the same point. The whole purpose for doing the identical chambers is, I'm doing a set of long term experiments to discover some facts about barrel life in polygonally rifled Columbia River Arms barrels and about the claims made by Modern Spartan Systems about their products. Testing seating depth across all 3 showed consistent though not identical results. I guess that there's only so much one can aim or claim to "duplicate" one rifle in another.

I personally do not co-develop loads doing one development cycle for one barrel and another for the other barrel. If I develop one that works in one barrel for my purposes (PRS, NRA Sporting Rifle, F-Class, screwing around) then I can bet my bottom dollar that it'll do as close to identically in the other ones. That's a major factor for me. I like to shoot this rifle this time and that rifle the next time but I'm only going to load 1 set of ammo so it better work in any of them identically.

 

[butchlambert]

@dmoran

Thanks for the reply.

So, when I spin on the new barrel should I say adjust the cbto for the same jump/jam and lower the powder charge say 5-10% for break in, then increase the powder charge till I get the same velocity as the previous barrel? (Obviously checking for signs of pressure.)

Spin on a barrel? Breakin?