I ask for chamber neck size advice.

L

LorenC

New member
I have a 7BR in my old bench gun that I'd like to get recut with a tighter neck. I think it's a factory chamber now. I'll be forming cases for it of course, so my dilemma comes from not knowing what works best for the new neck in this situation.

I'm understanding that an extra thick neck from not turning them after sizing the body down from .308 probably isn't the best bet, right? They definitely need turning to close to oem BR ammo neck size?
 
LorenC said:
I have a 7BR in my old bench gun that I'd like to get recut with a tighter neck. I think it's a factory chamber now. I'll be forming cases for it of course, so my dilemma comes from not knowing what works best for the new neck in this situation.

I'm understanding that an extra thick neck from not turning them after sizing the body down from .308 probably isn't the best bet, right? They definitely need turning to close to oem BR ammo neck size?
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Well, this is moot point, I just found Norma 6br brass to use. Yippee.
 
LorenC said:
Well, this is moot point, I just found Norma 6br brass to use. Yippee.
Click to expand...

Norma, Lapua, Remington 6 or 7BR is all very much preferred to forming the cases from 308 brass, even the special thin walled small primer cases. I did that back in 1982 and it made very poor brass.
 
Good to know. What size do the Lapua come out if unturned? You answered my next question with the .306". Thinking I'm going to hunt for a good gunsmith with a proper size reamer too.
 
LorenC said:
Good to know. What size do the Lapua come out if unturned? You answered my next question with the .306". Thinking I'm going to hunt for a good gunsmith with a proper size reamer too.
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You are not going to like what I am going to say. Unless you know a Gunsmith who works for peanuts you are going to pretty much waste money having a 7-BR rechambered just to get a different sized neck. You never have mentioned particulars of the current barrel except you say it probably has a "Factory Chamber". If it is a factory barrel it surely has a fair number of rounds through it at this point and is not worth spending any large amount of money on. If it is a custom barrel the same can probably be said unless it is a known to be a very, very good barrel. Your gunsmith dollars would be far better spent if put into a new barrel , and due to the limited number of custom 7mm bullets around I would go with a 6BR or even better a 30BR.

If it has a good barrel and a decent chamber at this time recutting chamber for a better neck fit may extend your brass life, but will have negligible effect on accuracy IMO.
 
I've been thinking of all that but there's a reason for my madness. I think it's a McGown barrel, it does have quite a few rounds threw it but was shooting it's best when I quit shooting. Short of finding someone to chamber it, I'll buy a reamer and do it here. And, the SMK were doing just fine last time they went down range.

I'm going to have to class this more as a learning project than a competitive shooter project, but getting it to shoot great while experimenting with longer range is the goal.
 
I did not measure the brass neck thickness after sizing up to 7mm/7BR.

My use for the rifle is High Power Silhouette, so at the time I turned several hundred.

I have over 4,000 rounds through the barrel and it still gets the job done and I am still using the same barss that has been annealed a few times.

All bullets, Sierra 130's and 168's, are moly coated by yours truly.

Powder Benchmark for the 130's and Varget for the 168's.

BTW I don't think a Gunsmith with a Tight Neck 7BR reamer would be willing to rechamber a "used" barrel. Gunsmiths cutting tight neck chambers are sort of unusual in more ways than one:)
 
John S said:
I did not measure the brass neck thickness after sizing up to 7mm/7BR.

My use for the rifle is High Power Silhouette, so at the time I turned several hundred.

I have over 4,000 rounds through the barrel and it still gets the job done and I am still using the same barss that has been annealed a few times.

All bullets, Sierra 130's and 168's, are moly coated by yours truly.

Powder Benchmark for the 130's and Varget for the 168's.

BTW I don't think a Gunsmith with a Tight Neck 7BR reamer would be willing to rechamber a "used" barrel. Gunsmiths cutting tight neck chambers are sort of unusual in more ways than one:)
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Didnt think of that. Hmmm.
 
Reamers

For your consideration Shilen lists 11 different reamers in stock to do 7mm barrels.
Possibly other barrel manufactures offer similar services.
Take a look and see if what is listed will work for you.

Another possibility is 4-D Reamer Rentals which lists 25 different reamers to do 7mm barrels.
Centerfire
 
Update on my confusion process.

I ordered 6br Lapua brass, neck expander mandrel and die body. Still slightly undecided but I think I'll unsrew the barrel and check the neck, along with some other things. Depending on what I find there I may get a reamer sized to my preference. Since a real shooter is just plain out of my league now, I'll have little in doing it this way, will be able to chamber a new barrel when that time comes around, and I really want to see how this things will shoot if I keep improving it a bit more. Just found out this is evidently a m48 or 48a Mauser, large ring but not long enough to eject a loaded '06 round.
 
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