6br NECK CLEARANCE WITH THE "NEW" REAMER

[Citysmasher]

All of my 6Br brass is the old gold box Lapua. My loaded rounds measure .269". The new 6 BR reamer that everyone is using is .2705". The old standard reamer was .272". I am getting a new barrel and they are using the .2705" reamer.

Is this enough clearance?

 

[Shynloco]

From what the "guys in the know" are telling me, you want a .002 - .003 clearance. I believe I recall that's the reason why Lapua thinned their newer brass (blue box).

 

[bward]

If you are not going to turn your necks, the new reamer won't have enough clearance.

 

[Citysmasher]

Does anyone know the outside diameter of a loaded neck of the current 6BR brass from Norma?

 

[AndyTaber]

Loaded necks on current Lapua Blue box is running .267 on my rounds. I just saw that you asked about Norma.

 

[areaone]

New NORMA brass is running about 2.69-2.695, for me it is a good alternative to the old Gold Box lapua for my 2.72 neck. Blue Box lapua works out at 2.675 on my 2.7045 neck 6 br. I have had no primer pocket problems with the new NORMA brass after five firings, BUT I do not press the max out of them either.

 

[coford]

My Blue Box Lapua is .268 loaded with a Sierra 107.

 

[jonbearman]

I have shot both in the .272 neck and cannot tell the difference on the target.I would just go with the new brass and avoid being boxed into the the older stuff as the supply is dwindling.

 

[dbaird]

I HAVE A 6BR WITH A .270" N.D. I HAVE BEEN SHOOTING THE GOLD BOX LAPUA BRASS (LOADED ROUND MEASURES .269"). HAVE FIRED THE CASES 15+ TIMES WITH NO PROBLEM-GETTING GROUPS OF .250". JUST BE SURE TO MEASURE EACH LOADED CASE TO MAKE SURE YOU HAVE CLEARANCE.

 

[Frankr]

It seems i maybe having some trouble with my new 6 Dasher. the reamer is a .2704 neck.
my loaded rounds are mic'n .270 at the pressure ring. this was to be a minimum clearance no turn neck.
I can not get a bullet to slip into a fired case at all. I know from experience that is not a good thing for extreme accuracy. but i have been shooting it that way and my groups in very windy conditions have been mid .300's at 100yards so it does shoot well. I have not shot enough or tuned a load yet,just playing around a bit. but if i get .0025 to .003 neck clearance maybe i could tune a load to the mid .100's. that is what I'm going to work on.
But new blue box lapua brass bought this year. I am going to have to turn neck's. It's alot of work, but it maybe worth it in the end. But dang i really wanted to try a no turn neck for a change.
I would say NO a .270-.2705 neck is not going to be enough clearance.

 

[Frankr]

If you are not going to turn your necks, the new reamer won't have enough clearance.

bward can you tell us why it wont be enough clearance?

 

[tclaunch]

I can not get a bullet to slip into a fired case at all.

I would say NO a .270-.2705 neck is not going to be enough clearance.

I agree

 

[expiper]

you guys are all bouncing around the best ND of all,,,,,.271" some are a thou bigger,,,so'me .0005 smaller ....but it is ju'st rite,,,,I have used it for 10 yrs and now with the NEW blue box stuff it is still perfect,,,,Roger

 

[areaone]

Three of my 6 brs are .27045 ND, No problem at all with Blue Box and Sierra, Berger, Hornady, Nosler or BIB bullets all from 55 gr to 95 gr., Neck is .2675 or .2670 loaded. Gold box is .269 loaded and I use that in a .272 neck chamber. New Norma brass measures .2685-.2690 loaded.

 

[tclaunch]

Too much clearance is much better than not enough.

 

[Frankr]

Sorry guys my new Blue box lapua brass. My loaded rounds are measureing .2695
after playng around some last night with a micrometer to measure loaded round and a ball micrometer to measure neck thickness. It takes some time to get a good feel for a mic to get a accurate reading and i checked the mic's with a calibration bar.. so they are reading right. But the tell tell sign is i can not fit a bullet into a fired case neck.
I can seat the bullets with out sizeing the case neck. neck tension is light but enough you cant move the bullet with you fingers. i can pull it out with a pair of plyers and some effort. berger 105 VLD measure's 2434 at the pressure ring. necks are around .0128 -.013 some ..0125 it allmost does not make sence to me But there is no doubt i dont have enough neck clearance.

 

[Hal]

FJIM

Your thickest cases measure .013 per side, .013+.013 =.026. .026 neck thickness +.2434 bullet diameter = .2694.

You should have .002 at the very minimum (..001 per side of the case neck) clearance between the case diameter and the chamber neck diameter.

.001 clearance isn't much when dealing with a high pressure cartridge and staring at the back of the bolt.

Hal

 

[Citysmasher]

I am sticking with my .272 reamer. Screw this...

 

[jrm850]

I ran my old .262nk 6br with .0015 total clearance for the life of the barrel, which I thought was common practice for benchresters. The brass lasted forever.

My current Dasher has the .2705" neck in it and I have shot the first hundred rounds of blue box through it without turning the necks. It shoots well and I am not seeing any irregular pressure indicators, but now you guys have me worried. I'm wondering if the tighter clearances that are used with very thin neck wall thickness might have stuck a number in my head that may not be safe with thick factory necks. I may be skim cutting from here on out. hmmm... maybe the tight clearance even has something to do with why my fireform lengths are short.

I do have a brand spanking new .271" neck and throater from PTG that I could probably be persuaded to loan if anyone thought the extra .0005 would make a difference.

 

[Frankr]

Im going to turn some of mine and see how it goes. but i have the rest of this 100 lot of cases all ready step necked ready to load and fireform. I will have to find a way to neck these ones down(the ones fireformed) then run em on my expander iron to get a good fit on my neck turning mandrel. as that is ultra important. I guess i will clean and anneal them first. But I want .0025 clearance. I have used that in a few rifles and it seems to work well as they all shoot. I turn for .003 clearance and end up with .0025. if i turn for .002 i end up too tight. Heck if i knew this i would have just went with a .269 neck as my turner is all ready set up for that. I have three barrel's all .269's.