Inside neck reaming

[victor3ranger]

I am going to be fireforming brass using the COW method to make 7STW brass soon.

I need to learn from you guys about what I am going to need exactly as far as inside neck reaming so I don't run into donut problems since I have to neck down the brass
Any help would be appreciated.
What tools I will need exactly would be a great help to

 

[338 dude]

I am going to be fireforming brass using the COW method to make 7STW brass soon.

I need to learn from you guys about what I am going to need exactly as far as inside neck reaming so I don't run into donut problems since I have to neck down the brass
Any help would be appreciated.
What tools I will need exactly would be a great help to

I

use my Wilson case trimmer, and then you buy the inside neck reamers specific to your caliber

 

[QuietTexan]

^^^^^^^^^^^^^^^^^^^^^^^^^^

Yup, LE Wilson mic trimmer, fantastic tool.

That said, I've only have HAD to ream one set of cases ever, in my experience it's not a very common task.

Necking up is normally an issue, not necking down. When you neck up the formed shoulder/neck junction migrates up into the neck. If you're worried you can turn the necks and go slightly on to the shoulder before necking down and you should be fine without having to ream.

This is a 243 Win case I neck turned before necking up to .257 cal to create a false shoulder (the bulge in the case neck), you can see a bright ring between the expanded false neck and the shoulder where the old neck/shoulder junction was pushed out, that's what would make the donut if it hadn't been turned first:

Since you're necking down you're all set up to leave a false shoulder for fireforming, I don't see a downside to having the cases being snug for COW method, only takes a couple minutes to test fit cases when setting the die to neck down.

 

[Taylorbok]

IMO it'd be super hard to properly and consistently ream necks, an IDOD would be the best option but that is pricey gear for a few cases. As @QuietTexan necking down should not expedite donut formation since you are turning part of the neck into the shoulder. When you turn shoulder into neck (necking up) is when more issues occur. That being said I would opt for a set of bushing dies and just size 3/4 of the neck and forget about donuts.

 

[Phil Rizzo]

Depending on what caliber you start with, it may be best to neck down in multiple steps. Definitely use a good chamfer/bevel and adequate case lube.
Ive always used interchangeable neck bushing dies, and though they may not be 100% necessary they can make the process go smoother with the right bushing.

 

[victor3ranger]

The finished size will be 7mm.
Cases used to get there will be 8mm rem mag, 300 H&H and 300 weatherby.
I have already necked down some of those. The 8 mm mag I took down to 30 cal first then to 7mm, the 300 H&H was pretty easy to get to 7mm. But I forgot to make the false shoulder on those so I have stopped for now

 

[QuietTexan]

Turning is the pre-emptive answer. Reaming is a less-than-optimal solution after the problem has been created.

The larger the parent case caliber relative to the necked-down caliber the more likely you are to have excessive thickness issues. A ball mic is an effective way to actually measure neck thickness, if you've necked down the 8mms without turning then you should mic those and get them down to .0130-.0140" thickness if you can.

an IDOD would be the best option but that is pricey gear for a few cases.

I use an AutoDOD for benchrest cases, on some of those (ie 30 BR) there's so much movement going on, combined with chambers cut with tight necks, it's about the only way to make uniform brass.

 

[VinceMule]

Years ago, I made a lot of 7 STW from 8 Rem mag cases, accuracy was sub 1/2" at 100 fire forming, I do not remember any doughnuts. Reamer we had ground was for 120 and 140g Nosler Solid Base, 3850 fps and 3650 respectively, 27" Hart 9" twists, #5 contours.

I prefer to neck turn the parent case, then neck down. Then part of what you turned becomes part of the shoulder, mitigating brass migration.

 

[victor3ranger]

Years ago, I made a lot of 7 STW from 8 Rem mag cases, accuracy was sub 1/2" at 100 fire forming, I do not remember any doughnuts. Reamer we had ground was for 120 and 140g Nosler Solid Base, 3850 fps and 3650 respectively, 27" Hart 9" twists, #5 contours.

I prefer to neck turn the parent case, then neck down. Then part of what you turned becomes part of the shoulder, mitigating brass migration.

Wow
You were able to push 140's that fast?
My barrel is going to be a Shilen 9.25 twist 26"
I am thinking about 140's first and keeping them below 3400. Afraid my Nosler AB's won't expand like I want if I get past 3400

 

[Phil Rizzo]

Long barrels and lazy twist = mo velo

if that Accubond acts more like a ballistic tip that's not ALL bad? At least on deer. Ha!

 

[victor3ranger]

Long barrels and lazy twist = mo velo

if that Accubond acts more like a ballistic tip that's not ALL bad? At least on deer. Ha!

I love the regular ballistic tips in my 7mag, those and the silver tips are my go to.
I hope they perform as good being pushed a lot faster

 

[VinceMule]

victor3ranger, all brothers, cousins, friends and I have ever shot is the 140g Nosler Combined Tec, black bullets on deer, and half a dozen with Barnes 140g ttsx. In the 90s, we shot a lot with the old 120g Nosler solid base, till we ran out of them, Both IMR7828 and Reloader number 22 with fed 215s.

Reloader number twenty-two with the 120g Nosler solid base never failed on large Kansas and Missouri bucks, never. I shot some Barnes TTSX 120 and 140g, Jumping them .050 from the lands with amazing accuracy, the 140s never failed us on deer and never killed a deer with the 120g TTSX, paper only.

Note: the 120g Nosler ballistic tips are absolutely the most accurate we ever shot out of our 7 stw's, shooting three-shot groups below .250 that repeated time and time again. We found about the 120g Barnes late in the game, but we sure killed a bunch of deer with the 120g Nosler ballistic tip also. The 120g nosler ballistic tips we believe are tougher jackets than the 140g. We had a food plot set up to be 550 yards from one tree stand, and we named this stand the STW stand.

As you can expect, primer pockets do not last long at these speeds, but these are hunting rifles only.

As Winchester brass became available, We shot Winchester brass only, the reamer we have has zero freebore, and bullets seated below the shoulder neck junction has never been a problem...we are thankful.

If you ever find any PMC Safari grade 300 Weatherby brass, it is absolutely the toughest brass we ever found to make 7 STW cases out of. We have never shot any of the newer brands of brass, but I bet it is worth having a reamer ground around their dimensions.

 

[VinceMule]

This is a fantastic video on Doughnuts by a Champion F class shooter whose main caliber is the 284 Winchester.

 

[Phil Rizzo]

victor3ranger, all brothers, cousins, friends and I have ever shot is the 140g Nosler Combined Tec, black bullets on deer, and half a dozen with Barnes 140g ttsx. In the 90s, we shot a lot with the old 120g Nosler solid base, till we ran out of them, Both IMR7828 and Reloader number 22 with fed 215s.

Reloader number twenty-two with the 120g Nosler solid base never failed on large Kansas and Missouri bucks, never. I shot some Barnes TTSX 120 and 140g, Jumping them .050 from the lands with amazing accuracy, the 140s never failed us on deer and never killed a deer with the 120g TTSX, paper only.

Note: the 120g Nosler ballistic tips are absolutely the most accurate we ever shot out of our 7 stw's, shooting three-shot groups below .250 that repeated time and time again. We found about the 120g Barnes late in the game, but we sure killed a bunch of deer with the 120g Nosler ballistic tip also. The 120g nosler ballistic tips we believe are tougher jackets than the 140g. We had a food plot set up to be 550 yards from one tree stand, and we named this stand the STW stand.

As you can expect, primer pockets do not last long at these speeds, but these are hunting rifles only.

As Winchester brass became available, We shot Winchester brass only, the reamer we have has zero freebore, and bullets seated below the shoulder neck junction has never been a problem...we are thankful.

If you ever find any PMC Safari grade 300 Weatherby brass, it is absolutely the toughest brass we ever found to make 7 STW cases out of. We have never shot any of the newer brands of brass, but I bet it is worth having a reamer ground around their dimensions.

When experience talks it sure makes it easier to listen.