Fire forming 6 BR brass and CBTO

[Dave Zander]

So I got some new Lapua 6 BR brass. I thought I would fire from it in my previously used barrel. Its headspace is within .002" of my new barrel. There were about 2200 rounds on my old barrel and about 250 on my new one. Figured I'd fire with some 8208 XBR I don't use and some 108 ELD-m's I hadn't used. When the older barrel was new I had the dimension where the 108's touched the rifling. I figured with 2200 rounds that dimension would have surely move out. I started at the touch dimension when that barrel was new. I started moving out in .003" increments towards the throat. It seemed I was getting more and more pressure as I moved out. I stopped at .009" longer than my touch dim. It didn't appear I was into the lands , I didn't see any marks on the bullet after chambering. Is that normal to see as effectively I'm expanding the case capacity. Just wonder what others have found in general. as I normally start at .020" off the lands and shorten the cartridge length. I've never tried seating in the lands either as it seems some of you guys do. My new barrel shoots pretty good running around 2850 at .040" off the lands with the new formed brass. I'm not a bench rest guy but shoot steel out to 1000 yards.

 

[K redden]

I don’t keep the best notes in this particular department. But it seems my dasher moves approx .003 every 400 - 500 rounds. As far as the pressure, it May need slightly less powder as you start to jam Hope this is the info you were looking for

 

[moondog]

I did the same with my old BRA barrel. Just shot crappy cheap 6mm bullets with a fairly light load. Didn't really worry about jamming them.

 

[JEFFPPC]

With your application why are you worried about fireforming. Load it to your proper length and go shoot a match. I believe your over thinking it. But.....new barrel sweet spot will probably need some tuning, especially if it was not cut with the same reamer.

 

[Mike TackleBerry]

So I got some new Lapua 6 BR brass. I thought I would fire from it in my previously used barrel. Its headspace is within .002" of my new barrel. There were about 2200 rounds on my old barrel and about 250 on my new one. Figured I'd fire with some 8208 XBR I don't use and some 108 ELD-m's I hadn't used. When the older barrel was new I had the dimension where the 108's touched the rifling. I figured with 2200 rounds that dimension would have surely move out. I started at the touch dimension when that barrel was new. I started moving out in .003" increments towards the throat. It seemed I was getting more and more pressure as I moved out. I stopped at .009" longer than my touch dim. It didn't appear I was into the lands , I didn't see any marks on the bullet after chambering. Is that normal to see as effectively I'm expanding the case capacity. Just wonder what others have found in general. as I normally start at .020" off the lands and shorten the cartridge length. I've never tried seating in the lands either as it seems some of you guys do. My new barrel shoots pretty good running around 2850 at .040" off the lands with the new formed brass. I'm not a bench rest guy but shoot steel out to 1000 yards.

Why worry about fireforming it in the old barrel, Go shoot it in the new barrel and begin load development tweaks if necessary. Even with Peterson new brass during load development I maintaining a handful of 1/4 moa groups.

 

[Rat Rifle]

Why worry about fireforming it in the old barrel, Go shoot it in the new barrel and begin load development tweaks if necessary. Even with Peterson new brass during load development I maintaining a handful of 1/4 moa groups.

My answer to this is, #1, to save barrel life on My best barrel. #2, I feel that an un fired case is not worthy of any load development, until it is fire formed. This theory, not mine, is easy to prove on target. I don’t think many people go to a match with virgin cases, and expect a good result.

Your Mileage May Vary

 

[Mike TackleBerry]

My answer to this is, #1, to save barrel life on My best barrel. #2, I feel that an un fired case is not worthy of any load development, until it is fire formed. This theory, not mine, is easy to prove on target. I don’t think many people go to a match with virgin cases, and expect a good result.

Your Mileage May Vary

They don't go to a match with virgin cases because they've developed their loads before hand. I was talking about taking it to the range and fireforming it in the new barrel, Not taking it to a match. Not sure why you even mentioned that. When I build a rifle I also buy a extra barrel cut with the same reamer by the same Smith. Depending on the chamber it may take more than 1 firing to have it fully fireformed, Sounds like a lot of wasted powder and components to just toss away. That's just me though.

 

[Carl S]

I've shot some excellent groups fire forming new brass in old and new barrels and I'm pretty sure there is a few people on this forum who have done the same.

 

[Dgd6mm]

I've shot some excellent groups fire forming new brass in old and new barrels and I'm pretty sure there is a few people on this forum who have done the same.

I'm guilty, and I've shot good too. HM scores in every relay that I've done it in.