6mm/284 neck case diameter question

[P1ZombieKiller]

I have a 6mm/284 and it has a stamp on the side of the barrel that says ".2675 ND". This is a Kreiger barrel. Can I assume that the ND means "NECK DIAMETER"? I have just bought some new Norma 6.5/284 brass, and when sizing it down, they do not chamber. I assume when sizing the brass from 6.5mm down to 6mm the brass has to go some where, and it makes the necks thicker. I do not have a micrometer to measure the diameter of the necks of the brass I just bought, but assume that I need to trim them back to .0120 each size,.0120 + .0120 + .243 = .267).

I did buy a RCBS neck turner with a 6mm dowel. I noticed that when zero'd, and placing the old fired brass on the neck turner, that they seem to be roughly .012 - .013 thick. This is what I am basing all my ASSUMPTIONS on.

OK... with all that said... I'm getting tired of all this work to shoot this gun... I want to rebarrel it with another 6mm caliber. In reading all the info on this site.... I think I have decided to go with the 6BR. Would my barrels be worth selling or should I just keep them in case I want to shoot them again? I have 2 barrels... 1:9 and 1:11 twist.... 1:11 has 492 rounds in it, and 1:9 has approx 200 rounds,it was on the gun when I bought it, and I took it off to shoot the V-max 65 and 87 bullets)

 

[CJ6]

I don't have any Norma 6.5-284 brass, but the Lapua 6.5-284 that I do have and use in my 6-284 using a .273 nk bushing measures .2745 loaded with 87gr V-Maxes.This is a NO TURN neck in my rifles.the .2675 ND designation on your barrel though different Dia. is the same style marking as mine are,.276 ND ) noting chamber Neck Dia. followed by Cal. 6mm-284. buy a set of good calipers/neck mic and do the measuring correctly. Also Cerro-Cast the chamber to get the measurements of it. IMHO it looks like you have a neck Dia. that would warrant the turning of the case necks. It's not that tough to turn the necks,just go slow measure properly.

 

[P1ZombieKiller]

CJ6,

With your being .276 and mine being .2675, looks like I will be turning some necks.

 

[zorak]

I have a 6mm/.284 and I am using the standard .284 brass with no problem loading shell in it.I know we used the factory 6mm barrel because the gun was a factory 6mm.We just had it reworked by a local gunsmith.

What I have seen is a big difference in the neck area.The standard .284 has more of a neck than the norma 6.5/.284 case does.Being that the neck is sharper on the 6.5/.284 and the barrel may be cut in the throat for the standard .284 case necked down to 6mm.

So you just might want to try necking down a standard .284 and give that a shot.

We also have a 25/.284 using the the standard .284 case's also with no problem loading in the chamber.

 

[CJ6]

Zorak, Do you know what the Neck Dia. is for your chamber? P1 was asking what the .2675 ND marking on HIS rifle was,not what brass to re-size .All brass is slightly different in neck thickness I use both Win 284 brass and Lapua 6.5-284,with Lapua being MORE consistent).When you start getting a ND of less than.272-3 your going to have to look at turning your necks it's that simple

 

[janderson0]

QUOTE:I just bought, but assume that I need to trim them back to .0120 each size,.0120 + .0120 + .243 = .267).

If new to all this and the neck is .2675 I suggest you target about .2655 loaded round dia.,.002 clearance) And measure your bullets, do not assume they are all .243.

Jim

 

[zorak]

Wes check your pms,also was I just wondering if you are trying to check and empty case or a loaded case in your barrel.Because if your trying a loaded case maybe the bullet it self is bottoming out and not the case just a thought.

Doug

 

[P1ZombieKiller]

Measuring the empty case, gives me a slightly different measurement than a loaded case. I did trim all my necks down to .012, and I pressed my 87 grain v-max bullets in the first 10,unprimed and uncharged), and all 10 chambered just fine, with 1 of them chambering much easier than the rest. I pulled all the bullets in those 10 rounds, and the 1 was trimmed a little thinner than the others,I have no idea if this was case #1 or case #10 as I did not leave them in order). I made no adjustments to the neck case trimmer, so I came to the conclusion that I needed to re-zero after every 5 rounds or so.

Doing this, I checked the next 20 rounds with the same process... except this time I did it 1 by 1 keeping them in the same order as trimmed. All measured within .0005 of any other neck turned.