Hi folks. I didn’t learn reamer-speak in school – I took Spanish. I’m ordering a reamer for a 6.5/7mm PRC (necked up 6.5 – not the 7mm PRC standard cartridge). The easy part first: If brass has pre-turned wall thickness of 0.015”, and I turn it down to 0.014, loaded round will have a diameter of 0.312”. So, if I since I want 0.006 clearance for loaded round, I’d need a chamber neck of 0.318. So far so good. But I also want to order a sister die to resize with. I was recommended dimensions of: “0.004 body and 0.014 neck”. First question, is that body contraction typical (it sounds like a lot)? I don’t want to overwork brass neck. I like to size, then run mandrel through, which typically ‘re-expands’ neck by about one thou. Not only did I do poorly in Spanish, but my learned math is pretty ordinary too. Given my uncertainty of the effect of spring-back, along with my aims as indicated above, what neck (and body) dimensions should I ask for in reamer for resizing die from the manufacturer? Sorry for the apparent lack of reamer experience – hopefully someone patient will spell it out for me.
Need help with reamer dimensions for resizing die
- Thread starter John Weigel
- Start date
Dusty Stevens
Shiner
Your brass will change every firing so your neck tension will get real loose after a couple firings and be inconsistent. As far as reamer dimensions go id call jgs and get what they are putting out right now, see what it cuts to then get your die made accordingly. They are doing a lot of prc stuff right now and have it down real well
Given changes every firing - and I'm aware of that, I shoot 284s, Shehanes and 7SAUMs. Does anyone who has purchased a chambering and resizing reamer combo have a suggestion for sizing die reamer dimensions in respect to chamber reamer dimensions? I'm Australian - we don't give up easily.
Kurz
Silver $$ Contributor
Years ago when custom dies were really thought to be the best solution we were asked to send the manufacturer several cases FIRED AT LEAST 3 TIMES.
You cannot account for the variations in spring back or the changing neck tension for every single firing. That's why we spend SO much money on all those expensive toys trying to eliminate the variables in our reloading. We strive for consistency shot to shot and case to case by using the techniques which try to control these variables. Annealing is one such idea.
It's easier for me to make my own dies so I don't have to worry about their schedule and their constraints.
If you want the best dies, call Warner Tool Co.
https://www.warner-tool.com/
https://www.warner-tool.com/reloading-dies/
Be prepared to pay more for these dies. Read the description carefully because you get a lot for your dollars.
Enjoy!
.004 is about right on the body. I'd use a bushing for the neck. .002-.003 smaller than a loaded round.
Dusty Stevens
Shiner
Most precision reloaders use a bushing die to account for the changing neck tension springback. I cant imagine buying a non bushing die in todays situation.Years ago when custom dies were really thought to be the best solution we were asked to send the manufacturer several cases FIRED AT LEAST 3 TIMES.
You cannot account for the variations in spring back or the changing neck tension for every single firing. That's why we spend SO much money on all those expensive toys trying to eliminate the variables in our reloading. We strive for consistency shot to shot and case to case by using the techniques which try to control these variables. Annealing is one such idea.
It's easier for me to make my own dies so I don't have to worry about their schedule and their constraints.
If you want the best dies, call Warner Tool Co.
https://www.warner-tool.com/
https://www.warner-tool.com/reloading-dies/
Be prepared to pay more for these dies. Read the description carefully because you get a lot for your dollars.
Enjoy!
divingin
Gold $$ Contributor
If he's going to use a mandrel to set the final diameter, it's not as critical.
Go a thou or four smaller than where you're going to end up and choose the mandrel that gives you what you want. Make sure you're small enough that thinner brass (or thinning brass) still gets you smaller than desired, so the mandrel sets inside diameter.
Send 3 rounds without primer and powder, with the brand of brass you are using and neck turning diameter of your choice ... to a die manufacturer...they will send you back a completed sizing die...most die manufacturers offer this service from cheap to expensive. The .006" clearence is excessive IMO only need .003" or .004" at the most in diameter for non neck turners, neck turners even less like .003" max ... This excessive clearance will result in split necks in the brass sooner from the cycle of firing & expanding to resizing...work hardening the brass more...causing inconsistency in neck tension and more annealing will be required to help save the brass, and make more consistent neck tension.
Kurz
Silver $$ Contributor
Dusty, yes I only use bushing dies currently. But can a sizing die reamer be designed to accommodate bushings? I want to shoot this cartridge, but by Jeez it’s complicated getting a sizing die.
Sure it can. Not that complicated. Your .004 is very good for the body.. .004 smaller than the chamber reamer works great in larger cases. I'd go .003 on a smaller cartridge. and I'd want a bushing die either way. Heck, you're already there. I've spec'd reamers this way for years. You can also work the other direction, spec'ing the chamber reamer around existing die dimensions. Now that makes a lot of sense when you think about it. Been doing it since about 2006 or so.
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Final comment: Gawd - it's so much easier to spec a sizing die reamer for wildcat cartridge than I was making it! Wish someone had hit on this initially. For future considerations of anyone searching this forum in same position of sweating sizing die reamer specs: Newlon die blanks allow for neck bushings, so sizing die reamer neck specs aren't life and death decision to achieve precise neck clearance in chamber (whew!), and 0.004 body spec is standard figure.
It's standard because it works. In this game where so many things are truly custom, I don't know if there's any such thing as standard. But in the end, what works for one may well work for many or even most. So by nature, it's common...errr, standard.
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