Minimum Neck Clearance?

[Andy]

I shot my 6.5/300 Win Mag for the first time today. All went well, but when I compared the before and after neck diameters, I became a bit concerned.

After firing, the neck measures just 0.001" larger than before firing. I know there's some brass springback, so I estimate I have 0.002-0.003" of clearance - which is safe, but minimum, right?

I'm accustomed to milsurps and hunting rifles with three-four times that (and more) where a bullet would drop to the bottom of a fired case, so I'm out of my comfort zone here.

Do I need to neck turn a couple thou off?

 

[thesilverfox]

Did your simth tell you to trim your neck?
Are you resizing with bushings. If yes, then what size?

 

[Kodiak99317]

Your fine Andy but keep an eye on it and clean the insides of your necks and see how it shoots at range. Over time the necks will get thinner too if you use 0000 steel wool, or ... you could turn off .0005 thou if you like, which becomes .001 thou for the two sides. I have run as close as .0002 thou of clearance in my 308 bench gun and that only works great for a couple of reloads. For on the dirt, 3 thou is probably best and safer, grass, sand etc., but 2 thou is fine IMO. How did it shot???

 

[JasonYuke]

I shoot about the same in my 6 ppc, load a bullet and measure it!
You can also turn the necks as needed, if needed!

 

[Obtunded]

That's excellent. As long as the rounds are chambering without problems, that is good news. Many people dream of those kind of tolerances. The less your brass gets stretched, the longer it will last.

Do keep us posted on your barrel life with a wildcat like that

 

[Andy]

Thanks guys, I'll just outside turn off enough to make them concentric and go with it. I haven't much to report yet - I've only shot a half dozen rounds to try a few loads and see how it feeds, etc.

This is not a serious Bench Rest gun, just something I've put together to test the waters. Mauser action, 24" 1:9 twist barrel. I'll play with it over the summer, do some trigger work and other tweaking and of course load development, and next stop would be to rebarrel to something 30" and heavy with a 1:8 twist.

It's not really strictly speaking a 6.5/300 Win Mag, as I have turned off the belt to make it look like my "8mm ARP". So far I have 120's at 3400 fps. It should launch 140's at 3200 fps at sane pressures.

 

[Mystic Precision]

Sounds like a great wildcat. Always wanted to get rid of the belt but don't have a lathe. Very interesting indeed.

If you can find some 123gr or 139gr Lapua Scenars, you have the velocity to go to 1 mile without any issue.

If you put a brake on, you can spot your own shots and watch the bullet trace. That's half the fun.

Enjoy and let us know how this project continues.

Jerry

 

[Andy]

Thanks Jerry, will do. I know the search for accuracy can be addictive and I don't need another addiction (milsurps, casting, etc.).

I'll be looking for recommendations for a barrel in the next while - 6.5mm, 1:8 twist, Mauser Large Ring, 30" long, no taper 1.125" diameter.

 

[dan belisle]

I had a 6.5-300 Wby a long time ago Andy. Shot very well, but the only powder that would wring it out was surplus Thunderbird 5010. Bought it off a guy who had set it up for 1000 YD BR shooting in the early 70s, if I recall. Barrel twist then was 1-9 or 1-10, I'm not sure. I eventually rebarrelled it to 300 Win Mag and sold it, but always liked the caliber. I think with today's powders and quick twist barrels, big 6.5s are going to really work a lot better. I know back in the day I never saw a 264 win that would equal factory quoted ballistics, but that should be fairly easy with the powders we now have. - dan

 

[Andy]

Dan,

The 6.5-300 Wby sounds like the 6.5/300 WWH - I have a set of dies.

Funny you wou1d mention 5010. I was just in a gunshop this morning that had a pound of Hodgon 5010 for sale, but I passed as I don't want to get hooked on an orphan.

I agree that today's powders provide better choices than in the past. Looking forward to some fun.

I had a 6.5-300 Wby a long time ago Andy. Shot very well, but the only powder that would wring it out was surplus Thunderbird 5010. Bought it off a guy who had set it up for 1000 YD BR shooting in the early 70s, if I recall. Barrel twist then was 1-9 or 1-10, I'm not sure. I eventually rebarrelled it to 300 Win Mag and sold it, but always liked the caliber. I think with today's powders and quick twist barrels, big 6.5s are going to really work a lot better. I know back in the day I never saw a 264 win that would equal factory quoted ballistics, but that should be fairly easy with the powders we now have. - dan