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Questions regarding properly sizing belted cases

 
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  #1  
Old 04-29-2013, 11:04 PM
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Join Date: May 2012
Location: Northern Colorado
Posts: 92
Questions regarding properly sizing belted cases

I just purchased my 1st 7 STW. I have laundry list of questions regarding loading for this cartridge. I have some experience loading other beltless cartridges.
I'll apologize in advance if the answers are here but don't have time to study the forum in detail.

Belted cartridges are new to me and as I understand are head spaced off the belt, this would present a different set of challenges for me. To my understanding it seems that with belted cartridges head spacing would also need to be on the shoulder as well for best accuracy. With 2 head spacing points does the belt tend to interfere with proper center bore alignment from shoulder head spacing. Do the belted cartridges require less to no shoulder bump to properly align cartridge with bore upon firing.

My next question is: I have 2 sizer dies for this cartridge. Neither one seems to be able to produce concentric necks. A WAY, I've found to get fairly concentric necks is to rotate 90 degrees part way through, size a little more, rotate 45 degrees, rotate 90, size rest of the way. I've been expanding with Sinclair expander for consistent neck tension. The problem is, my accuracy went away after all the rotations in attempts to get everything strait. Could somebody give me thought on this?

The rifle is a McWhorter custom, which I've not even fired yet. I've had it for a week now, and can't wait to touch some rounds off. I have load data, and ammo loaded by McWhorter that somehow got destroyed during shipping. Hopefully more will arrive tomorrow.
I have plenty of all components to load for it, but the concentricity problems have me concerned. I am considering having a custom sizer die built to alleviate the problems I'm seeing with standard production sizer dies, and hopefully prolong case life in the process.
Any help and suggestions you guy's may have is much appreciated.
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  #2  
Old 05-01-2013, 08:27 PM
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Join Date: Jan 2010
Location: Leominster mass, originally Salisbury Maryland
Posts: 1,323
Re: Questions regarding properly sizing belted cases

Quote:
Originally Posted by cerwin View Post
I just purchased my 1st 7 STW. I have laundry list of questions regarding loading for this cartridge. I have some experience loading other beltless cartridges.
I'll apologize in advance if the answers are here but don't have time to study the forum in detail.

Belted cartridges are new to me and as I understand are head spaced off the belt, this would present a different set of challenges for me. To my understanding it seems that with belted cartridges head spacing would also need to be on the shoulder as well for best accuracy. With 2 head spacing points does the belt tend to interfere with proper center bore alignment from shoulder head spacing. Do the belted cartridges require less to no shoulder bump to properly align cartridge with bore upon firing.

My next question is: I have 2 sizer dies for this cartridge. Neither one seems to be able to produce concentric necks. A WAY, I've found to get fairly concentric necks is to rotate 90 degrees part way through, size a little more, rotate 45 degrees, rotate 90, size rest of the way. I've been expanding with Sinclair expander for consistent neck tension. The problem is, my accuracy went away after all the rotations in attempts to get everything strait. Could somebody give me thought on this?

The rifle is a McWhorter custom, which I've not even fired yet. I've had it for a week now, and can't wait to touch some rounds off. I have load data, and ammo loaded by McWhorter that somehow got destroyed during shipping. Hopefully more will arrive tomorrow.
I have plenty of all components to load for it, but the concentricity problems have me concerned. I am considering having a custom sizer die built to alleviate the problems I'm seeing with standard production sizer dies, and hopefully prolong case life in the process.
Any help and suggestions you guy's may have is much appreciated.
Cerwin, I read your thread starter the day you wrote it, but have been busy,so here goes. First of all, congrats on the new rifle. Those " macs" are art forms, and are usually tack drivers in what ever caliber they come in.
And, of course, Welcome to the Brotherhood!
As to concentricity issues, for the MOST part, it happens on the resizing stage, and more then probable, when you are on the expander. Better put, when you are pulling down on the case neck. It CAN happen during seating, but is more likely to be in the resizer set up. It can be as little as slightly worn press linkage, play in the die threads, or the shell holder not perfectly square with the ram. Remember, the taller the case, the more deviation is possible. I have driven myself nuts with it before, and finally, I was able to keep it below .002.
My best explanation is just cross tees, and dot eyes!!! This cartridge is NOT hard to load for. It is very readable, and SHOOTABLE. And I must stress proper initial die set up. That is a integral part of case life, and accuracy as well. Enjoy the ride, and don't be afraid to ask a question or two if needed. This is a " kick ass " round, make no mistake about it! And extremely accurate too!
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  #3  
Old 05-01-2013, 11:43 PM
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Join Date: May 2012
Location: N.D.
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Re: Questions regarding properly sizing belted cases

+1 on 7stw's comments.
I'll toss another thing in too. I hear more peopls having concentricity issues with turrets and progressives than O or C presses. You may want to size with a rather fresh single stage press and lube your necks so the expander doesn't pull the case out of square. Only the bottom half of the case itself really needs lube with this one if you are using a pad and lube; if you lube her all the way up you'll likely get lube dents after the die gets saturated. Just don't get too stingy or you'll stick one.
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  #4  
Old 05-02-2013, 02:46 AM
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Join Date: Oct 2011
Location: Bend, Or
Posts: 312
Re: Questions regarding properly sizing belted cases

Since all our action truing and reloading is about concentricity and parallelism, I find it odd that nobody takes once fired brass and single point turns the neck ID concentric to the case od.
Turning the neck od with a neck mandrel gives uniform neck thickness but it's not concentric with the od of the case. You then have to shoot the brass to get the neck od to conform to the chamber and hope the id stays concentric.
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  #5  
Old 05-02-2013, 05:55 AM
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Join Date: Jan 2008
Location: Northeast
Posts: 2,233
Re: Questions regarding properly sizing belted cases

Having gone through a few different lots of Norma brass in my 300 WM, if have found it to be very consistent in neck wall thickness running .0145". Great brass, but it should be for the price. With once fired cases I will neck size only for 4 firings, then use a body dye and FL size to .002" shoulder push back. All dyes used are Redding. I have found neck alignment with the case, and bullet run out to be consistently less then .002" by using a Redding S dye, with the busing sized to .002" of neck tension. I will back off the bushing knob on the S dye a small fraction of a turn so you can faintly hear the bushing click due to slight looseness in the dye. This seems to allow the bushing to float and follow the fire formed neck. I'll use a very small amount of Imperial wax on the neck. I have not seen the expander on my specific dye cause alignment issues but I remove it anyway. I will anneal the cases after every 4-5 firings. I have used this approach for several belted case cartridges I have loaded for and it seems to produce very good accuracy, ES and case life. IMHO.
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  #6  
Old 05-02-2013, 05:28 PM
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Join Date: May 2012
Location: Northern Colorado
Posts: 92
Re: Questions regarding properly sizing belted cases

Thanks for the input guy's. I'll keep a close watch on any variables that can lead to concentricity issues, and eliminate, or minimize.

I've been loading for 300 RUM for about a year, and have not had the concentricity issues with it, which is the reason I'm wondering if my dies are the problem. I dont use an expander ball (one of the variables I've already eliminated). I'm using a sinclair expander die to keep consistent neck tension, and so far this has not caused any problems. I do have a question though. In an effort to produce perfectly concentric ammo I tried rotating the case numerous times during sizing with a Redding type S neck bushing die. This gave me concentric necks, but the accuracy was not as good as necks that were not rotated, and sized in one step, but not as concentric.
My question is can rotating TOO much during sizing give inconsistent neck tension, which would lead to decreased accuracy?
I shot this STW for the first time Tues afternoon, right as a winter storm was blowing in so I didn't shoot much. 2 - 3 shot groups, with ammo from McWhorter. This thing ROCKS! I've never shot a rifle like it before. At 200 yds, 4 of the 6 shots were touching. The other 2 were right there as well but opened up to about 1". This was with virgin never fired brass.
My thought has been to neck only size for 3 firings, and have custom die made to minimally size cases, and improve concentricity problem. Would that be worth it?
I have a standard RCBS FL die,, and a Redding competition bushing set. I seem to have problems with both.
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  #7  
Old 05-02-2013, 06:17 PM
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Join Date: Jan 2010
Location: Leominster mass, originally Salisbury Maryland
Posts: 1,323
Re: Questions regarding properly sizing belted cases

Quote:
Originally Posted by cerwin View Post
Thanks for the input guy's. I'll keep a close watch on any variables that can lead to concentricity issues, and eliminate, or minimize.

I've been loading for 300 RUM for about a year, and have not had the concentricity issues with it, which is the reason I'm wondering if my dies are the problem. I dont use an expander ball (one of the variables I've already eliminated). I'm using a sinclair expander die to keep consistent neck tension, and so far this has not caused any problems. I do have a question though. In an effort to produce perfectly concentric ammo I tried rotating the case numerous times during sizing with a Redding type S neck bushing die. This gave me concentric necks, but the accuracy was not as good as necks that were not rotated, and sized in one step, but not as concentric.
My question is can rotating TOO much during sizing give inconsistent neck tension, which would lead to decreased accuracy?
I shot this STW for the first time Tues afternoon, right as a winter storm was blowing in so I didn't shoot much. 2 - 3 shot groups, with ammo from McWhorter. This thing ROCKS! I've never shot a rifle like it before. At 200 yds, 4 of the 6 shots were touching. The other 2 were right there as well but opened up to about 1". This was with virgin never fired brass.
My thought has been to neck only size for 3 firings, and have custom die made to minimally size cases, and improve concentricity problem. Would that be worth it?
I have a standard RCBS FL die,, and a Redding competition bushing set. I seem to have problems with both.
Cerwin, Greyfox is dead on , on all his accounts, and his approach is spot on. The other variable, or at ANother variable, is neck thickness, and consistency at that end of the case.
As for the accuracy you are getting, get used to it. ( especially with that rifle you have). Neck sizing will probably be your best bet for brass life, and accuracy too, but at some point, you will have to give the body a squeeze, and just bump the shoulder back, just a smidge, to keep the chambering reasonably snug, but not TOO snug. Find ing that sweet spot will be your homework. It's a little trial and error game, but the rewards are smoking accuracy, low ES, SD, and DRT deer. Forget federal brass, go with Winchester, or Remington brass, ( in that order, IMHO ), and better yet, fire formed Norma, 300 HH brass. THAT, is the " crem de LE crem" brass set up. That is my next project. That is a smokin set up you have there, feed it right, and it will continue to feed you for a long time!!!
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AIM SMALL,MISS SMALL. 7 STW
LIFE IS TOO SHORT! AND WE ARE A LONG TIME DEAD!!!
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