My gun is headed out to the Smith Friday and the Smith said he has a semi tight neck reamer (.339) and I have never used a tight neck chamber before..I was wondering the benefits there is for a tight neck and problems that are associated with it? My brass I turned down to .328 OD and .305 ID sized plus with a .308 diameter bullet seated the out side is .330...Any suggestions with the #'s I just gave or problems?
- Thread starter raythemanroe
- Start date
I don't shoot the 300WM, but I have brass here that I've collected over the years, however it's buried in the closet somewhere and I can't readily get to it to measure.
What's the typical neck wall thickness?
Let's say it's similar to the 308 Win stuff--that is to say .014"-.015". Going on the thin side, .014"+.014"=.028"+.308"=.336", so a .339" chamber will leave you .0015" on either side of the neck, which is about right for guys shooting BR tight throated chambers, from what I've read.
However, .015"+.015"=.030"+.308"=.338". That doesn't leave you all that much room at all, so turning your brass down to anywhere below .014" thick, should be fine, even taking into account that some bullets might be .3085".
Neckwall thickness of <.0140" is where you want to be, if that chamber throat is .3390".
Chris
That's pretty handy info
what would be the maximum preferred? There about .010 thick right now I hope I didn't junk them!
what would be the maximum preferred? There about .010 thick right now I hope I didn't junk them!
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That's pretty handy info
I'm just a hack and don't turn my necks, but if that chamber/throat is a true .3390" in diameter, than you can live comfortably with a neck wall thickness of .0135"-.0140". Turning your necks down to .0100" seems a bit excessive, with regards to that particular throat measurement that you're throwing out, but maybe 300WM brass isn't typically .014"-.015" thick? It could be that you're starting off at only .0130", I just don't know where 300WM should be.
Usually, you'll want to turn to your necks to 'just clean up' the high spots and turn down, what...about 90% of the neck's length?
You don't want to thin them out too much, as that will weaken things a bit more, moving forward and you're spending a lot of time doing this, so you don't want to throw your cases away after only a couple of cycles.
Find out where your necks mic at before turning and use a precision ball mic at a few spots around a decent sample size of cases. Get an average 'thickness'. If you're above .01400", turn them down from there. If you're at .01350", turn them down a bit more just to clean them up and call it a day, since you're below where you need to be for that particular throat.
You're mainly focused on removing high spots around the circumference, unless you have to thin them out to get them to fit, in which case, you probalby should have gone with a wider throat IMO.
Chris
ray,
0.010" is too thin and makes the cases very susceptible to dings and dents. I just turned 200 Federal and 200 Remington 300 WM cases to 0.012", about 65% of the cases for both brands completely cleaned up at this thickness and met my spec for match brass. I'll use the remaining cases to make hunting ammo for buddies. Don't forget to turn far enough into the shoulder to prevent donuts.
HTH,
DocB
0.010" is too thin and makes the cases very susceptible to dings and dents. I just turned 200 Federal and 200 Remington 300 WM cases to 0.012", about 65% of the cases for both brands completely cleaned up at this thickness and met my spec for match brass. I'll use the remaining cases to make hunting ammo for buddies. Don't forget to turn far enough into the shoulder to prevent donuts.
HTH,
DocB
Tell the smith to rent a different reamer that gives you some slack. Don't complicate your life too much. After all...it is YOUR rifle. If you plan on hunting with it, it pays to be able to use factory ammo when the airlines lose or you forget your customized neck ammunition.
A .339 neck isn't super tight and some factory ammo such Winchester may fit and I have neck turning tools.
I hate having to do anything to brass to make it work so I have never neck turned or used tight neck chamberings. A 300WM isn't a benchrest cartridge so I don't really see a need for tight necks as I get excellent accuracy with a standard match chamber. I just went and measured some fired Win 300WM cases I have and the necks are .338-.339". I use a .330 bushing on them to give them .003" of neck tension so my loaded is .333". .339 neck would be a little tight and I would worry about reliability after continued fire and fouling build up.
How much brass do you have that you turned? It would suck to get a tight necked chamber for a couple hundred pieces of brass and then have to continually turn? If not alot then why not have him use a standard 300WM match chamber and not a tighter neck so you aren't wedded to turning?
How much brass do you have that you turned? It would suck to get a tight necked chamber for a couple hundred pieces of brass and then have to continually turn? If not alot then why not have him use a standard 300WM match chamber and not a tighter neck so you aren't wedded to turning?
