OzFclass

Geoff,
I am not saying yours and Adams conclusions on your observations are not correct (and could be) but I would add a little side of caution. Other things can be happening as well (as per Bruces suggestion and many others including the reamer spec's aren't correct).

Some of the top level shooters I know still run <2 thou clearance on 1000 yard work with great success. 3 thou is generally considered adequate and slipping a projectile in a fired case is not an ideal test due to various rates of springback etc. I don't think Adam intended that his "rule of thumb" was meant as a scientific test method. You can certainly have a situation where you cannot slip a projectile back in the fired case but there is no impingement under firing.


BUT - if the outcome worked for you guys then that is the important thing and as I said before - I have no problem with lots of neck clearance.

but
0.004 MUST be right, because that is what they say on 6mmbr
keep safe,
bruce.

Bruce- heres a video you may appreciate
http://www.youtube.com/watch?v=CbnMws6973k

Dave,
No problems, I hear what you're saying. I've neck turned just a few cases for experimentation. What I will do for next weekend is I'll test both, turned necks & non turned cases all once fired. I 'll post the results as in smallest group size, 10 shot groups. 180VLD with 2217 & 15 thou jammed.
300yds should be ok.
Geoff

bruce moulds wrote:but 0.004 MUST be right, because that is what they say on 6mmbr bruce.

That's where I went wrong. I listened to John Giles who told me .0025-.003" clearance for the neck he cut me.

Hahaha that's classic Brad Y

^ second that!!!

very good brad.
there are a lot of them there.
keep safe,
bruce.

DaveMc wrote:Geoff,
I am not saying yours and Adams conclusions on your observations are not correct (and could be) but I would add a little side of caution. Other things can be happening as well (as per Bruces suggestion and many others including the reamer spec's aren't correct).

Some of the top level shooters I know still run <2 thou clearance on 1000 yard work with great success. 3 thou is generally considered adequate and slipping a projectile in a fired case is not an ideal test due to various rates of springback etc. I don't think Adam intended that his "rule of thumb" was meant as a scientific test method. You can certainly have a situation where you cannot slip a projectile back in the fired case but there is no impingement under firing.


BUT - if the outcome worked for you guys then that is the important thing and as I said before - I have no problem with lots of neck clearance.

Yep exactly Dave! It's not a hard and fast rule but I didn't find any noticeable loss in accuracy running MORE clearance where some people have found a dramatic loss in accuracy running less. So out of the desire to have something that was consistently accurate with less chance of any issues relating to cleanliness I decided on 4 thou

johnk wrote:

bruce moulds wrote:but 0.004 MUST be right, because that is what they say on 6mmbr bruce.

That's where I went wrong. I listened to John Giles who told me .0025-.003" clearance for the neck he cut me.

John also cut my 7mm neck and it shoots ok with 0.003" clearance but another rifle that I had built by another smith, with the same stated neck diameter of .312" needed 0.004" clearance.
I put this down to reamer wear. Its very easy for a reamer to loose its sharp edge in this area and the resulting neck diameter may not agree with the .312' stamped on the barrel........

I run between 3.5 - 4 thou and cut my case necks to .308 with .312 -.311 chamber neck.
RB

Apologies for dragging an old topic back but didn't want to create another...

Question: what are people using to next down from 300 SAUM to 7mm. I used my Redding bushing die that does not go all the way to the shoulder junction. As a result I have turned too much at the unsized portion and now have twice fired cases with neck separation... splitting and falling off.

I'm clearly not doing something right and although I now have 100 new cases to throw in the bin, I would prefer not to have 200....

Thanks for any advise.

Albert

Best way is a form die cut with the reamer for the chamber.

Basically a threaded piece of old barrel with the reamer run into it and it works like a full length sizer ask your Gunsmith if they can make you one up?

Ah, Brad Yates - what a pisser!!

ajvanwyk try making a neck bump (no bush) from a blank Newlon [url]http://www.newlonprecision.com/
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or Wilson
With your reamer

RB