Im considering buying a concentricity guage, but the more I get thinking about it, the more questions I have. First, I understand the idea about making your rounds as concentric as possible to keep the bullet lined up with the bore. What I dont understand, is once you find out your bullets arent concentric, what do you do to fix them?



Secondly, on inside neck doughnuts, what causes them and are they really that common? If you properly sized virgin brass before outside neck turning, wouldnt this take care of them? Thanks.

Are you concerned about a hunting rifle or BR rifle?
If you aren't going to compete there is not much to worry about in my opinion. Things like Redding bushing dies help prevent bad concentricity and neck turning does also. What you can do is try to eliminate the cause but I don't think you can do much to fix one that is not concentric.

Others with different experiences with offer more help soon.

Donuts occure when you neck turn your brass and the cut doesn`t go far enough into the shoulder. The brass moves foreward under pressure and the case neck "turns inside out" a ring then forms at the inside rear of the neck. If you don`t turn, which doesn`t work very well in a factory chamber, you won`t have to worry about them. Neck reaming will remove them.

Scott

Good concentricity gauges are expensive, as are neck turning tools. If you are talking about a factory rifle, or even a custom barrel job with a SAAMI chamber, you're not going to see much, if any, benefit from all your expense and time. Even with a custom barrel and/or chamber there are many cartridges where the improvements will be minimal. On a BR rifle the gains can only be measured in thousandths of an inch but BR is a game of thousandths. JMHO

Ray

Look at this post:

Runout

good luck

Reloader

quote:

Originally posted by Ol` Joe:
Donuts occure when you neck turn your brass and the cut doesn`t go far enough into the shoulder. The brass moves foreward under pressure and the case neck "turns inside out" a ring then forms at the inside rear of the neck. If you don`t turn, which doesn`t work very well in a factory chamber, you won`t have to worry about them. Neck reaming will remove them.

Hey Ol Joe

I've developed donuts after outside neck turning. It's hard for me to turn the neck a little into the shoulder brass like the instructions say. Seems like it might develop a weak spot if I go too far. I have a Forster outside neck turner and they don't offer an inside reamer like Sinclair (I think it was them I saw that had one when I went looking). Anyway they had cutter blades on the end of the caliber specific mandrel that was supposed to do away with a donut. Don't want to invest in a whole nuther trimmer.

I don't outside turn except one time on once fired brass. The donut does not seem to impede seating of bullets anyway.

you might also find this interesting....

http://longrangehunting.com/ubbthreads/showflat.php?Cat...&page=0&fpart=1&vc=1

Doughnuts- when i size down 308 win. GI brass to use in 243 win., this forms a doughnut. Neck turning standard 243 brass has never formed a doughnut for me. Forming 243 out of 308 brass is a waste of time in my experence.