Project Resizing and Concentricity

With another Redding Type S FL Bushing Die on order; I am starting on a project to compare different resizing methods vs concentricity. My intention is to measure neck concentricity on 10 case batches - 10 collet sized, 10 collet + body sized, 10 bushing sized w/ Redding FL bushing dies, and 10 conventionally FL sized with the Lee FL die. This will be done with my 4 calibers - 223, 243, 7mm-08, and 30-'06. It'll take me a month or two to get it all done. I'll publish the results, here. I started yesterday.
I sized 10 fired, 30-'06 cases, with the Lee FL die, then checked neck runout. I did the same thing, this morning with 10 .223 cases, also with a Lee FL die. Interestingly enough, all 20 cases neck runout measured under .001". That may not surprise some of you; I really didn't know what to expect. I'm just getting started, but, I'm starting to wonder if this is all a function on how small the neck is sized and then what occurs in the seating process.......

This will be interesting to watch. From my experience, I think alot of the "which die/process works" will be determined by the difference in the neck OD of the sized case versus the sized case. Just makes sense to me that the more you have to move the brass, the more opportunity for "error" introduced by any process. That's why the first thing I do before buying dies is measure a factory round neck OD and then measure a fired case from the rifle. I select dies based on how much I need to compress the brass. Also, brass quality would need to be consistent across the calibers so you don't get any quality x process interaction.....I guess what I'm saying is if you want to test just the sizing method, you'll need to control as much non-die-related variability as you can or you won't get credible results - the results will be commingled with whatever factor you didn't control...That being said, I applaud you for doing the test.

Two things I hope you'll keep track of and report:
1. for each caliber - difference between fired case neck OD and sized neck (as per above)
2. Mark/number your cases so that you can discard one or two if the continuously show poor concentricity (i.e. high variation in neck wall thickness.

Elkbane

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Originally Posted by Elkbane

This will be interesting to watch. From my experience, I think alot of the "which die/process works" will be determined by the difference in the neck OD of the sized case versus the sized case. Just makes sense to me that the more you have to move the brass, the more opportunity for "error" introduced by any process. That's why the first thing I do before buying dies is measure a factory round neck OD and then measure a fired case from the rifle. I select dies based on how much I need to compress the brass. Also, brass quality would need to be consistent across the calibers so you don't get any quality x process interaction.....I guess what I'm saying is if you want to test just the sizing method, you'll need to control as much non-die-related variability as you can or you won't get credible results - the results will be commingled with whatever factor you didn't control...That being said, I applaud you for doing the test.

Two things I hope you'll keep track of and report:
1. for each caliber - difference between fired case neck OD and sized neck (as per above)
2. Mark/number your cases so that you can discard one or two if the continuously show poor concentricity (i.e. high variation in neck wall thickness.

Elkbane

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Good, clear suggestions....
The .243, 7mm-08, and 30-'06 brass are all Winchester; each caliber (brass) from one bag apiece, when I bought it. The .223 brass is Hornady. These were originally purchased as one box of loaded ammo with the the 52 grn HPBT. I got a good deal on the ammo and bought it for the sole purpose of using the brass.
As for case neck O.D.'s; I hadn't intended on reporting that, but, do have the data. As I've been purchasing Redding Bushing Dies, I've found out - the wrong way - one needs to know the fired neck O.D. (in addition to the loaded neck O.D.) so one can select an intermediate size bushing as most factory chambers dictate two bushing sizing steps for optimum concentricity.

But, one question for you - other than for bushing sizes, what's the reason for measuring fired brass neck O.D. when selecting conventional dies? I can understand it for bushings, but, for conventional dies I'm not seeing how it matters unless you know how much one manufacturer's die is going to compress the neck.......?

Interesting test!

My bet is the seating process will introduce the most run out in the finished round. ;)

You may also want to look at the technique suggested by German Salazar on his riflemansjournal website. For full length sizing he suggests using an o-ring, very similar to how the Lee dies are setup, which allows the die to adjust itself slightly during the process in order to achieve better concentricity. It would be interesting to see how this compares with your other methods.

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Originally Posted by CharlieNC

You may also want to look at the technique suggested by German Salazar on his riflemansjournal website. For full length sizing he suggests using an o-ring, very similar to how the Lee dies are setup, which allows the die to adjust itself slightly during the process in order to achieve better concentricity. It would be interesting to see how this compares with your other methods.

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I read him alot - he's a master at brass prep and I think its kinda neat that he competes with a 112 year old cartridge. I've read the article you're referring to. Its a bit confusing - he's talking about a little bit of float so the case and neck is centered. I **believe** he's referring to conventional sizing dies. He makes another statement, with regard to Redding Bushing Dies, about backing off the bushing nut slightly to get the float. This is also spelled out in Redding's instructions and I back the nut off very slightly - about 1/16 - 1/8 of a turn.
The conventional dies I have are all Lee's (so they have the o-ring) - part of the Deluxe Rifle Die sets I purchased for the collet dies...except for the 7mm-08. It appears Lee doesn't make a deluxe rifle die set for that one - just the collet die set (which I have).

Beartooth,

This is an interesting post. I am "in the middle" so-to-speak, of doing the same thing. I am or have, done this with two calibers. The first is the .223 and it's shot through my Savage Carbine.

I have my .223 Lee F\L sizer die set up so that it just bumps the shoulder back to where the .223 has 1-2 thousands of headspace when chambered. I then make sure that the brass is at or under the SAMI spec for length, and if not, I trim and chamfer outside and inside. Then load and seat a 68gr. Hornady Match bullet.

When I check the concentricity of these .223's it's rare that I find one out more than .001. These give me one-hole groups at 100 yards, and my rifle is zeroed at 200.

Now, my "other" cartridge is the 6.5 Swede which I could only get about 50% of "quality" concentricity from either a Lee seating die or Hornady seating die, and even using a Redding competition seating die, I could get no better than 75%. So, I figured I'd spring the big $$$ and try the Redding competition bushing neck sizer die. Very pricy....but I am now getting 98% of my reloaded 6.5 bullets to have concentricity of +-.001. Now....that is consistency!!

Have I got to the range yet? No. I went to a different scope (from a Vortex to a Leupold) and I have finally got it mounted, and with the crazy weather we have been having here in South Western Pa., I haven't had a chance to get to the range yet. However, I will post my results when I get them.

Just a side note on the .223.....I previously owned and shot for about 5 years a Contender single shot .223. I loaded 45gr bullets with that as I mostly shot to 300 yards at maximum. It was a fine groundhog killing bullet, and I found that simply seating the bullet to the SAMI max worked better than "fooling" with the OAL. For this Savage .223, I found the same thing. Seating the Hornady match bullet to the SAMI max gave me the most consistent groups. I dunno....maybe for the little .223 it's just me. But I thought I'd let you know.

FWIW

Dave

I would be interested in seeing your measured concentricity vs shooting performance results; that may make me spring for a concentricity gage.

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Originally Posted by CharlieNC

I would be interested in seeing your measured concentricity vs shooting performance results; that may make me spring for a concentricity gage.

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Well.....that's the ultimate "goal" of the entire experiment. I'm not planning on changing OAL, bullet type, powder type, powder charge, or primer. Even the neck tension, as measured by the OD of the neck sized brass (a bit expensive to find the right size bushing. I got it after buying 3 bushings @ $27 per bushing!!!)

And BTW, I DO turn the necks of my brass.

Dave

I agree with Apache, seating bullets and measuring runout on the bullet is the acid test. Just because a case neck has little or no runout on the OD, doesn't mean that the ID is exactly the same. Case necks can be thicker on one side than the other. Seating a bullet straight is the end game. I have never done what you propose to do in a scientific or organized way, but I am interested in seeing if your findings agree with what I have observed over my years of handloading. Best of luck on your project and keep us informed. Luckus

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Originally Posted by CharlieNC

I would be interested in seeing your measured concentricity vs shooting performance results; that may make me spring for a concentricity gage.

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Since receiving my Forster Coax Case & Cartridge Inspector (about 3 weeks ago), I've been checking and sorting my loaded rounds by concentricity. For every five rounds, I get 2-3 rounds under +/- .001" runout, 1-2 which are a little over .001", and one which is around .002". I rarely get one over +/- .002".
So, I usually shoot the best three out of every five rounds, using the other two for foulers. If you saw my recent post "Finally....Range Day",
http://www.savageshooters.com/showth...ally-Range-Day
both sets of the 7mm-08 groups and the .223 H335 & IMR4895 groups were sorted.

I am re-reading Tony Boyer's book again; too much to digest the first time. Interestingly reported that he and another guy checked some of their loads for concentricity and got quite variable results, but upon shooting all were good. He concluded since they load into the lands, that this took care of centering before firing. So you may want to factor jamb length into the mix when evaluating the effect of concentricity.