Neck bushing for new brass

[South6BR]

I have a Remington 6BR which possibly has a .269 or .270 neck. Once fired brass is measuring .268 and this is new blue box Lapua brass. Unfired new brass is .266 and my loaded rounds with a 90 grain Berger BT target projectile are .267 to .267.5 or .268.
So my question is with so little neck tension for new brass, do I run new cases through my competition neck die with a .265 bushing before I load them for the first time? Currently my smallest bushing is .265.
I haven’t struck this before with other rifles in 6BR and I am not the most experienced reloader. I have been having some accuracy troubles and now I am suspecting it may be due to the light neck tension - after checking everything else.
This rifle likes the 90 grain Bergers only so far, the reason why I just bought some more!
Thanks for any help.

 

[BoydAllen]

I usually figure on about .001 spring back from chamber neck for fired brass. It looks to me like your clearance for a loaded round in the chamber neck is too small. Fixing this will require a skim cut on the necks, with a turner. In addition to possible pressure issues for your thickest cases, this would effect accuracy by not allowing a clean and consistent bullet release.

 

[Bill Norris]

Agree with Boyd. Slight neck turn clean up and then start with a bushing .002 less than a loaded neck dia. round.

 

[South6BR]

Neck turning? I thought that was only for a tight neck chamber and the case wouldn’t fit. If the case chambers ok what does a light turn do? I’m really not set up for neck turning so there’s some research coming up.

 

[BoydAllen]

Can you insert a bullet in the neck of a fired case with no resistance?

 

[South6BR]

Can you insert a bullet in the neck of a fired case with no resistance?

No I can’t, Boyd.

 

[1shot]

I have found that it's always better to have a little extra neck clearance that just barely enough. A clean bullet release and an accurate rifle goes hand in hand.

Lloyd

 

[gunsandgunsmithing]

No I can’t, Boyd.

That's likely your problem. Listen Boyd. He'll get you on the right path

 

[Bill Norris]

Neck turning? I thought that was only for a tight neck chamber and the case wouldn’t fit. If the case chambers ok what does a light turn do? I’m really not set up for neck turning so there’s some research coming up.

Light turn clean up will allow for proper release in some cases such as yours.

 

[mikecr]

I have been having some accuracy troubles and now I am suspecting it may be due to the light neck tension - after checking everything else.

What do you mean when you suggest 'after checking everything else'?
Your load development was not with new/unfired brass, right?
What do you think neck tension was during load development?

If you developed with 1thou clearance and 2thou interference their should not be a problem -with brass matching to that developed with.

 

[South6BR]

What do you mean when you suggest 'after checking everything else'?
Your load development was not with new/unfired brass, right?
What do you think neck tension was during load development?

If you developed with 1thou clearance and 2thou interference their should not be a problem -with brass matching to that developed with.

Yes Mike it was with new brass so I haven’t done any brass sizing, only chamfer, debur and round the necks with a 6mm mandrel in a Sinclair die. This lot of brass had a few case necks that were out of shape.
The Bergers I managed to get in the centre of the target but everything else shoots to the left, by several inches. I checked the scope, rail, action screws and there’s no build up of fouling. Scratching my head now and contemplating having a smith spin the barrel off and look at the chamber.

 

[South6BR]

Can you insert a bullet in the neck of a fired case with no resistance?

I just re-read this, Boyd. In fired brass I can insert a bullet. In new brass, no I cannot. That likely changes things? Thanks again.

 

[BoydAllen]

Yes

 

[mikecr]

Yes Mike it was with new brass so I haven’t done any brass sizing, only chamfer, debur and round the necks with a 6mm mandrel in a Sinclair die.

So if you load developed with NEW brass, and you're concerned with results of new brass, what did you change from load development?
Your question began with neck tension, did you change that?

None of this thread makes sense yet

 

[South6BR]

Well, I read that neck tension can effect accuracy and I’ve been having some accuracy issues and wondered if the light neck tension might be enough to cause a problem. If so, should I run it through a neck bushing die before seating a bullet? I will run some once fired brass through a .266 bushing and try that.
It made sense when I was thinking about it.

 

[Dave M.]

Try 2.5-4 thou neck tension

 

[Bill Norris]

Well, I read that neck tension can effect accuracy and I’ve been having some accuracy issues and wondered if the light neck tension might be enough to cause a problem. If so, should I run it through a neck bushing die before seating a bullet? I will run some once fired brass through a .266 bushing and try that.
It made sense when I was thinking about it.

I would go back and re-visit this before moving forward.

Boyd Allen - I usually figure on about .001 spring back from chamber neck for fired brass. It looks to me like your clearance for a loaded round in the chamber neck is too small. Fixing this will require a skim cut on the necks, with a turner. In addition to possible pressure issues for your thickest cases, this would effect accuracy by not allowing a clean and consistent bullet release.

 

[Ccrider]

Boyd is making an educated guess about the size of your chamber/neck being .269 since you don’t seem to known what it is.

Assuming that is correct, with a .268 finished round you do not have enough clearance.

If you have a .25 caliber sizing die, lubricate it and slightly expand enough of the neck on a fired piece of brass up to .272 or so and see if it will chamber. If it will not, use your 270 bushing to size it down and try again. Measure the brass as you continue to size it down until it will chamber. This will tell you what size your chamber neck is and you can make decisions about what ti do next from there.