• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

.266 6BR

maxscm

Gold $$ Contributor
I just picked a used Rem 40xBR for the single shot action for a future build. Have no history on it. I decided to shoot it some to see what it'll do.
The barrel is stamped .266 neck 6BR. Appears to be a Remington Barrel by the stampings. Maybe a 12-14 twist.
Does that mean my brass necks should measure .264-.265 loaded?
I preped 5 rds Lapua Brass and loaded them necks measured .265 loaded. Chambered well.
Fired them. The necks measure .271 fired and rechambered nice and snug as a fired round.
Now,,,,do i have a .266 neck? or ?
why do the fired necks measure .271?
 
Sounds like PFM to me. :)
How would you get a fired case to measure .271 with a .266 necked chamber?
Is this David Copperfield???? ;)
 
Yes, or real close to it. There may be some shrinkage, but yes real close to .266.
I would guess that your barrel was cut back and rechambered but it is confusing as to how it would still say .266.
hmmmmmmmmmmm.
 
I suspect the same. But the barrel stampings all line up with the stock like the orginal chambering.
I tried chambering an unturned Lapua brass and the bolt won't close. Still that might just be the OAL . I'll try some more solutions.
 
Tried to chamber an unturned new Lapua Brass.
Bolt won't close.
Trimmed the new Lapua brass .005 at a time till bolt closed.
Bolt closed on new Lapua Brass at 1.540 OAL.
Seated a bullet. Outside neck of loaded round measures .269.
The Round chambered snug, but bolt closed.
Conclusion, Must not be a .266 neck as Stamped on the Barrel!
 
Hunt up some cerrosafe and do the chamber, thats the only way to be 100% sure of the chamber....
 
Numbers don't seem to make a lot of sense. The original Remington 6BR in the 40-X was supposed to have a max case length of 1.520". Your neck seems to be shorter than the current standard, but longer than the original, and larger in diameter than stamped. Seems someone has been working on it.
 
maxscm: First 6BR I had built had the chamber cut with a reamer my 'smith had at the time. .265" chamber neck and chamber over-all-length of 1.540", exactly half way between the Norma/Lapua length of 1.560" and the old Remington length of 1.520". You could use the Sinclair chamber length gauge to determine your actual length. Sounds to me like your barrel may have originally had a .266" chamber neck diameter, and that's what the barrel ident was marked for, then sometime after that someone got tired of outside neck turning their brass and had the chamber neck opened up to a .272" no turn diameter. Every one of my cases have measured neck diameters of .001" smaller than what I know the chambers neck diameters are. I buy my own PTG chambering reamers and spec the neck diameters. For example, a .272" reamer will produce as fired necks of .271". A new .270" chamber neck produces brass with .269" as fired dia. And I could go on and on, but it's always .001" of springback.
 
Sounds like you have a 6mmbr Remington chamber instead of a Norma to me. Also it has been opened to a .272", no setback or any other cutting has to be done to do this. I'd have someone run a .272" 6mmbr Norma reamer in there.
 
Make shure that the twist rate and throat length match. 12 or 14 twist use a short throat, 8 twist- long throat for the heavy bullets. I ruined a chamber by using a Norma reamer on a 12 twist, the 70gr bullets had to jump a long distance. I wanted to go to a no-turn neck to shoot Lapua brass out of the box.
 

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Forum statistics

Threads
165,825
Messages
2,204,324
Members
79,157
Latest member
Bud1029
Back
Top