View Full Version : 6mmbr trim length

12-24-2007, 08:41 AM
I would like to know the correct trim length of this shell. I have a manual but it only gives me the length of the 6mmBR remington which is 1.510 which cannot possibly be right. I didnt realize there was a difference. Can someone help me as to the correct trim on the 6mmBR Norma? Thanks...Gene from Pa

Nor Cal Mikie
12-24-2007, 10:07 AM
6BR "Norma" is listed with a max length of 1.560. Trim length is 1.555.
If you measure "your" chamber length you might be surprised just how long it really is!
I've got 2 6BR rifles and both chamber lengths are different.
One is 1.580 and the other is 1.579.
I havn't had to trim to length for a "very long" time. Bump the shoulders a touch and full length resize if they get tight in the chamber.
I use a Stoney Point gauge with a plug from Sinclair to get my chamber measurements. G-243 is for the .243 / 6MM. It fits in the modified case. Works like a charm! I measure all my chambers and all are longer than the listed trim lengths. HTH. Mike.

Dick Grosbier
12-24-2007, 09:07 PM
If you measure "your" chamber length you might be surprised just how long it really is!
I've got 2 6BR rifles and both chamber lengths are different.
One is 1.580 and the other is 1.579.
That doesn't strike me as very different did you perhaps mean 1.569" ?


12-24-2007, 09:15 PM
Some background I got from one of the developers of the 6BR Rem (not me). The original, termed as a 6 CBR Rem, was just a 1.5" long 308 Win and the chamber was 1.525" long. I've used that original reamer. Later the cartridge was named 6BR Rem and the chamber was 1.550" long.

Lesson - take the time to know your chamber dimensions on all these factory adopted wildcats.

Nor Cal Mikie
12-24-2007, 09:22 PM
Dick: The point being, all chambers are cut to different length. Depends on the reamer used and most are cut longer than the Max trim length.
The actual measured length of the chamber will tell how long to leave the cases before they really need to be trimmed. And those measurements are correct. Just .001 difference between the two chambers but both are longer than the listed max trim length.
Would it have been any different if I had listed them as 1.579 and the other as 1.580?
Know your actual chamber length and save yourself some work.

Nor Cal Mikie
12-25-2007, 09:03 AM
And it wasn't me that came up with that idea. Someone else around here mentioned it so I checked it out. Now I just bump or resize as needed. Havn't had to trim in a long time. Sure cut down on the brass prep!;)
If you want all your brass the same length,trim.
Measure all your chambers and know ahead of time just how far you can let your brass get before you "need" to trim.

jackie schmidt
12-25-2007, 09:32 AM
This would be a great time to heve a actual reamer print.
I have two "modern" Dave Kiff Pacific Precision 6BR reamers that have a length at 1.560. They will accept a Lapua case right out of the box.
Since it is Christmas Morning, we really do not want to go into the entire history of the 6BR, a search on the archives will offer up just about everything you would ever want to know.
Chamber a case without trimming it, using a stripped bolt. If it goes in easy, you probably have a chamber that is designed to take a case right out of the box as far as length goes. If it is, you sure don't want to trim back to 1.500.
If the case won't chamber, and you see evidence of the case mouth hitting the end of the chamber, (it will be curled over), then it's trial and error time. Trim them back .005 at a time, (a seated bullet will help add to the resistance if anything is hitting), untill you are sure it is not hitting, and go .005 more. It might take a kittle trial and error, but in lue of a chamber print, or the Gunsmith who chambered it, that is the best you can do with no other tools, such as cerasafe.
Good Luck.........jackie

12-25-2007, 10:27 AM
Sinclair sells a Chamber Length Gauge that fits into a fired, unprimed, shortened case, their $8.50 ea. The front of the neck in the chamber will finish seating the gauge, measure and deduct .010" from that. This is your trim to length. I trim my 6BR to 1.555".

12-25-2007, 10:52 AM
as was stated earlier....we are all guessing ....dont ever get a chamber done by any gunsmith that cant prvide you with a chamber drawing....it is amazing how many "gunsmiths" do chambers and dont know what they have ..or even what they shuld have ....deal only with competent Benchrest gunsmiths that compete or are in constant contact with competitors who are shooting their work.....only YOU can tell what the actual chamber dims. are.....measure or use trial and error...but you gotta do it...!!!!!!!....my modern Kiff reamers cut a 1.570 chamber ...the new brass is "suppposed to be" aprox.....1.555-1.560 from the box....which is a good trim length also......but you are asking us what ur girlfriend likes....you gotta figger it out for yourself.....Of cours nuthin like the advice from an "old guy" about the fairer/weaker sex...hahaha.......Merry Christmas.....Roger

12-25-2007, 01:09 PM
Dave Kiff was a great help and provided me with a reamer spec drawing of the reamer my gunsmith used when I contacted him. I wanted to know just exactly what I had chambered and he was great to provide his drawing for me. Thanks Dave.