7mm rsaum questions

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DaveMc
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Joined: Mon Aug 22, 2011 6:33 pm

#16 Postby DaveMc » Mon Mar 17, 2014 11:54 am

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.

bruce moulds
Posts: 2087
Joined: Sun Jun 19, 2005 4:07 pm

#17 Postby bruce moulds » Mon Mar 17, 2014 12:14 pm

but
0.004 MUST be right, because that is what they say on 6mmbr :!:
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880
http://youtu.be/YRaRCCZjdTM

Brad Y
Posts: 1916
Joined: Fri Jun 26, 2009 8:21 pm

#18 Postby Brad Y » Mon Mar 17, 2014 12:44 pm

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

Rebel105
Posts: 504
Joined: Fri Jun 13, 2008 12:22 am

#19 Postby Rebel105 » Mon Mar 17, 2014 1:25 pm

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

johnk
Posts: 2128
Joined: Sun Sep 07, 2008 7:55 pm
Location: Brisbane

#20 Postby johnk » Mon Mar 17, 2014 2:01 pm

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.

Courtz Day
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Joined: Fri Feb 11, 2011 9:32 pm

#21 Postby Courtz Day » Mon Mar 17, 2014 3:36 pm

Hahaha that's classic Brad Y

Nathan P
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Joined: Tue Oct 15, 2013 11:03 am

#22 Postby Nathan P » Mon Mar 17, 2014 4:36 pm

^ second that!!!

bruce moulds
Posts: 2087
Joined: Sun Jun 19, 2005 4:07 pm

#23 Postby bruce moulds » Mon Mar 17, 2014 4:53 pm

very good brad.
there are a lot of them there.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

BATattack
Posts: 902
Joined: Mon Dec 29, 2008 10:29 pm

#24 Postby BATattack » Tue Mar 18, 2014 9:02 am

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

Norm
Posts: 833
Joined: Fri Jul 23, 2010 10:21 pm
Location: Gippsland, Victoria

#25 Postby Norm » Tue Mar 18, 2014 11:18 am

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........ :?

RAVEN
Posts: 1893
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Location: Adelaide South Australia (CTV)
Contact:

#26 Postby RAVEN » Tue Mar 18, 2014 3:20 pm

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

ajvanwyk
Posts: 168
Joined: Tue May 17, 2016 5:50 pm

Re: 7mm rsaum questions

#27 Postby ajvanwyk » Sat Oct 07, 2017 8:33 pm

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
Albert
Rosedale Rifle Club

Singo85
Posts: 112
Joined: Tue Mar 08, 2011 11:04 am
Location: NSW

Re: 7mm rsaum questions

#28 Postby Singo85 » Sat Oct 07, 2017 8:39 pm

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?
Cheers
Michael "Machine Gun" Singleton

williada
Posts: 643
Joined: Wed Jul 22, 2009 12:37 am

Re: 7mm rsaum questions

#29 Postby williada » Sun Oct 08, 2017 7:59 am

Ah, Brad Yates - what a pisser!! :lol: :lol:

RAVEN
Posts: 1893
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Location: Adelaide South Australia (CTV)
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Re: 7mm rsaum questions

#30 Postby RAVEN » Sun Oct 08, 2017 1:22 pm

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

RB


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