6mm BRX Neck Turn and Fire form question

[Dutchman]

I'm somewhat new at reloading for Benchrest and my question has to do with fire forming both old (once fired) 6mm brass and some new 6mm Lupua brass for a tight neck BRX chamber on a recently purchased used gun. The current neck size I measured on a fired round from the previous owner is .265" so I'm guessing the chamber is .266" but not 100% sure on that since I don't have the reamer print. An existing loaded (turned neck round) case neck size with Berger VLD 105's is .264" when I use a .263 Bushing die. With both the once fired 6mm BR case and new Lupua 6mm BR cases I'm assuming that I will need to turn the necks first before sizing with my bushing die .263 that I plan on using for the neck tension I want. After I turn the necks then I plan on chambering and fire forming a round with the Berger 105's touching the lands and using 29.5 grains of Varget with cci 450 primers. My question is am I going about this the right way or not?

 

[johara1]

If it's a tight neck chamber it should be marked on the barrel……. If you measure .265 on the fired brass it could be .266 you must allow for spring back. Check the wall thickness of the brass, and find out what bullit dia. you have. size one case and seat a bullet and mic. the neck dia. It should be at least .002 under a fired case for starters to be safe. ……. jim

 

[Dutchman]

Thanks Jim for the come back..........the chamber was not stamped on the barrel and the brass thickness on the "turned" brass is measuring .100" and the bullet dia. is .241". The fired case neck is .265" dia. and the bullet dia. is .241". The seated bulled neck dia. is .264" and the fired case neck is .265" or .001" under. I use a .263 bushing die to neck size only my cases.

 

[johara1]

Thanks Jim for the come back..........the chamber was not stamped on the barrel and the brass thickness on the "turned" brass is measuring .100" and the bullet dia. is .241". The fired case neck is .265" dia. and the bullet dia. is .241". The seated bulled neck dia. is .264" and the fired case neck is .265" or .001" under. I use a .263 bushing die to neck size only my cases.
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What are you measuring with? Neck wall thickness should be around .010 and bullet diameter should be .2428 - .2441 You need mics. that measure to the .0001 ……. jim

 

[Catfish]

You are thinking correctly, and I agree with Jim on .002 neck expansion. I think you meant to say the the bullet dis. was .243, not .241. If your mandrel on you neck turner measures .243 you can easily figure the case neck thickness nessary, or just mic. the neck while on the mandrel to get .002 under neck size in chamber.

 

[Judd]

Just match the existing brass (especially if it's shooting well) and turn it to .1....jam the bullets, use Federal 205's (softer and great for forming, might even shoot better than the 450?).

 

[johara1]

Just match the existing brass (especially if it's shooting well) and turn it to .1....jam the bullets, use Federal 205's (softer and great for forming, might even shoot better than the 450?).

Turn to .1 ????? Tube mics. measure in .0001 and so do outside 1" mics. that is what you need ………. that measurement is a .100 ? a neck wall is only around .012 +=……… jim

 

[Judd]

Just match the existing brass (especially if it's shooting well) and turn it to .1....jam the bullets, use Federal 205's (softer and great for forming, might even shoot better than the 450?).

Turn to .1 ????? Tube mics. measure in .0001 and so do outside 1" mics. that is what you need ………. that measurement is a .100 ? a neck wall is only around .012 +=……… jim

You're correct.

I assumed he was saying .010...the point is, regardless of the measurement....if the current brass works, then match it.

 

[Dutchman]

Thanks guys and I think I'll give the Federal 205's a try..............current brass seems to shoot well so I'll stick with those measurements.