# Neck Turning Winchester brass (7wsm)

1. ### jcannActive Member

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Sep 27, 2011
I’m shooting a 7wsm with a neck chamber of 0.320”. I have measured all my unfired brass neck wall thickness and have determined in order to get consistent neck wall thickness I need to turn the necks to a wall thickness of 0.0125”.

My question is, is the neck chamber too loose (0.320”) for this dimension (2 x 0.0125”) + 0.284” = 0.309”? I had planned on trying one of the three Redding neck bushings of 0.306”, 0.307” or 0.308”.

Any guidance would greatly be appreciated.

2. ### MikecrWell-Known Member

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More of a nightmare in reloading than a solution to thickness variance..

What brass is this?
How thick is it?
Who chambered it?

I think it's too much sizing.
The brass will expand to chamber neck and spring back to ~.318". While your bushing selection is good for .309" it's too much bushing sizing -from .318".
The brass will curl in at too high of an angle, leaving necks way overworked(possibly splitting), and undersize of calculated.
Because there is almost no taper in bushings, you wanna be within ~5thou with them.

If this is Win reloading brass, I would think it would be ~15thou thick. If this is the case why not cull the brass with so much variance, instead of turning it all to an undesirable value?

3. ### jcannActive Member

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Sep 27, 2011
The brass is Winchester.

The rifle is a GA Precision. George uses a reamer with a 0.320 neck. I want to use it as a long range hunting rifle.

I've been in the reloading room and have decided to turn (clean up) the necks to 0.0145".

(2 x 0.0145) + 0.284 = 0.313"
With a 0.320 neck chamber will this be much better? Also would you buy bushings at 0.310, 0.311, and 0.312 to get started?

4. ### MikecrWell-Known Member

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That's better, but GA Precision needs to purchase a better suited reamer.

Maybe they figure you'll slop muddy ammo in there, and then toss the brass, or reform it everytime(into something 'similar' to a 7WSM) with a FL die?
Maybe they need to stick with .308...

5. ### woodsWell-Known Member

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At .320" that is not a "tight necked chamber"

My 280AI from Hart is .313" and that is not real tight and I turn to ~.0125"

If you get good brass (<.001" thickness variation) and it is <.0165" (.320"-.003" clearance=.317"-.284"=.033"/2=.0165") per side then you don't need to turn. IMO you want your neck brass to expand and be resized the least amount possible.

6. ### dbhostlerWell-Known Member

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With all my rifles I usually cast the chamber to see exactly what I am dealing with. That said, I just clean up the neck on my 7 WSM. I'm using Win brass and a .311 button on my FL die. The loaded round comes in with a .315 neck which would be a bit loose in a .320 chamber, but works in my shooter. So just clean up the neck, and use a button that will reduce the neck .004 to .005 and see what happens. BTW, I wouldn't reduce the neck wall thickness to under .010.
db

7. ### JeffVNWell-Known Member

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Like I said on the other site, .320 is VERY roomy. If you are going to neck down to .313, you''ll want to consider doing so in 2 stages, as the chances are good you'll induce concentricty problems trying to take it all down in one step.

Plus you are going to work the necks a bunch each time you size the brass, you'll want to anneal that brass every other time you fire it (no more than every three) or it will split on you fairly fast.

Jeffvn

8. ### jcannActive Member

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Sep 27, 2011
Jeffvn,

I did do it in two passes. After neck expanding with a K&M expander die I measured case neck wall thickness. All of them measured between 0.0145 and 0.0153 after I culled a few pieces of brass.

Maybe I made a mistake turning the necks for a"no turn" chamber. I'll find out at the range. I can always start over with new brass. Like I said on the other site, this is going to be some what trial and error on my part. Hopefully with good advice from people like you I can I can learn from my mistakes. I really appreciate all the help from everyone.

Jcann

9. ### JeffVNWell-Known Member

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620
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Mar 19, 2004
Jcann

I can't and don't fault your decision to opt for as uniform a neck tension and bullet release as possbile. I do that with all my rifles. But none of my rifles (except one - discussed below) are running a standard size chamber. All of my rifles run 0.004 thou clearance over the loaded rounds or less; most run 0.003 total clearance. As an aside, I own all my reamers, so that I can strictly control the size of my chambers and the number of chambers that each reamer has cut.

Given the decision you have made, I see no reason to stop your desired progress. I would neck down in two or possibly even 3 stages with no more than 0.005 in any one stage, depending upon the final numbers of your loaded rounds. Were I in your shoes, I would be annealing every other firing to keep the neck tension under control.

Depending upon how hard you run your 7WSM, you may well burn that barrell out in a year or two (mine do not last any longer than 2 years), and then you can decide what to do on the next one. Barrels are consumables, so I look long term, not just at the decision immediately in front of me.

My tactical 7WSM (a Terry Cross, KMW built in 2004; the ONLY Rifle I do not control the reamer) has a much looser chamber than my snug chambered rifles. It is now running its 3rd barrel (true story - I love this rifle and its my go-to rifle for hammering steel and my back up for running the Mile+ in the desert). I use "cleaned" brass (0.0145) neck on it. I sized it in two stages (until I got a custom sizing dies from Neil Jones). I anneal that brass every other firing; it shoots like a beast and I recently used it to set a personal record relay in a local 600 F-Class match. The KMW continues to be one of my best shooting rifles - if that makes you feel better....

Jeffvn

10. ### AZShooterWell-Known Member

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I don't see an issue in neck sizing your brass after you trim them. The difference between the mandrel sized necks and the bushing should be close.

Here is an alternative way to neck down fired brass without several progressively smaller bushings. Take out the sizer ball from a FL sizing die. Run the brass into die using it as a partial FL sizing die. This will easily reduce the necks to a small dimension as there is a ramping effect within this die. Then run each case into the sizing mandrel followed by the correct bushing die. In some instances if enough brass is removed from a neck wall the FL die will give you the exact dimension without any further sizing. I did that with a tight necked 30 BR, I turned the necks to fit the RCBS FL die which gave me a perfect .0015" neck tension.

I went through the exercise you are attempting with a 284 win with a large chamber neck dimension. Only turned the necks enough to clean up the necks all the way around with hopes of getting more consistent bullet release. Didn't get any improvements in accuracy but did crack case necks in a few firings. Learned not to bother with chambers with factory sized (read huge) chamber neck dimensions.