New ultra precision dies. Got a set!

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spamassassin
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New ultra precision dies. Got a set!

Post by spamassassin » Thu Aug 30, 2018 10:57 am

While I was in South Africa a few weeks ago I managed to pick up a new sizing die that's made there. I actually got to meet the man behind the magic through an introduction by a mutual friend. I got to see and use the die I was extremely impressed. So impressed I had to have one. They have a standard (though still super precise) die for SAAMI/CIP chambers and a "Custom Collection" version for those of us with more persnickety requirements. I got the custom collection version made to my specs while I was in country. I also got to have a nice chat with Jaco, the man behind the magic, and have a nice long chat with him about how the things were made and some general chit chat. Turns out, the level of precision they craft these with apparently required a ton of effort just in building testing instruments so they could measure sufficiently precisely to hold their amazingly tight tolerances.

The box is nicely jointed and finished wood.
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Inside everything is set in custom cut foam. Given the precision, cost and purpose, you'll want to keep things orderly and clean and not bumping into each other.
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All of the little bits from the die kit.
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All the mechanical stops are in the die itself so it's a little different to use than I'm used to but dramatically different. It does mean the die can move from press to press without readjustment of the die. One tiny bit of note, it's not a standard 7/8" die body. It's a 1"-14TPI body so a different press bushing is on order for my RCBS Rockchucker and I'm having a local machine shop cut one of my Dillon tool heads for it.

The benefits for me are setting of neck tension & head spacing very precisely. It came with 5 neck bushings at .0005" increments so I can now get consistent tension between lots of brass. Normally I neck size only until I have to bump the shoulder back but that causes issues with rounds that decides they won't chamber without a lot of force to close the bolt. Slows me down in a match and breaks my concentration. There are click adjustments on the die for the shoulder bump which I've seen and measured to be extremely accurate. Want to knock the shoulder back .0015, 3 clicks. It works just that easily.

The cost is fairly high (retail is almost $600 shipped to the USA) but real precision costs real money. If I can't magically be a better shot, I can pay to take a little more slop out of my ammo.

It's a little different in how it works to other dies I've used in one nifty respect, the body sizing and shoulder bump happens first without touching the neck, then the neck sizing operation happens as its own part of the stroke and neck sizing depth is controlled by virtue of a shim pack that adjusts it in .0020" increments.

They have a seating die coming out too which I've already asked for a copy of. I have a couple buddies using one of these already and they're reporting very good things. As soon as my press bushing and tool head are done I'll be doing a vigorous bit of comparison testing against my existing redding dies both in group sizes and dimensional consistency.

spamassassin
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Re: New ultra precision dies. Got a set!

Post by spamassassin » Wed Sep 12, 2018 3:23 pm

I've now had a chance to wring this sizer out just a little bit. I'm doing a lot more fiddling around than I normally would so I can get good measurements. I'm getting consistent .0005 shoulder bumps so far. More as more develops.

spamassassin
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Re: New ultra precision dies. Got a set!

Post by spamassassin » Thu Sep 20, 2018 9:59 am

While my seating die is being engraved I've taken some time to wring out the sizer properly. Accuracy of neck sizing is perfect. Accuracy of shoulder bump has been perfect as well. Both things one would expect from a 550 dollar die.

Actually that precision turned out to be a little bit of an issue in a way. Some of the brass I was working with hadn't fully formed to the chamber (the brass was a mix of 1-fire, 2-fire, 3-fire and 4-fire) and was coming in short. I thought there might be a die issue so I smoked the shoulder on one and found out it wasn't making contact with the shoulder bumping part of the die. Then instead of assuming all cases were uniform length to the shoulder, we measured with the included headspace gauge and figured out what was going on. It needed really 3 firings before pushing the shoulder was going to be required or possible anyway. Hooray! So not an actual die issue so much as a brass issue and a me lumping lots of brass together and forgetting about that detail.

Along the way I had to have some machining done. My RCBS shellholder clearly wasn't parallel between the top face where the die contacts it and the flange that holds it into the press ram. I took that over to my machinist and had him tinker on it. That made setup a little easier even though it wasn't totally necessary. It eliminated me using a feeler gauge around the circumference of the shellholder to verify where "touching" actually was. I still had to use a feeler to verify that I was at "just touching" versus -.0005 or +.0005.

Once we got it set up against the included gold master, then the fun times with lube selection came up. The body section of the die is very tight and the base of Coach's 6xc chamber is not. I was getting a rough time running brass in and out of it with stickiness. Hornady One-Shot case lube was not going to be it. It wasn't slick enough. Fine in my Hornady/RCBS/Lee/Lyman/Redding dies but not in this one. I then tried pad applied RCBS case lube which definitely was better but still not as slick as I thought it should be. Next we tried Imperial Sizing Die Wax which takes longer to apply and is messier but it offered no stickiness on sizing. That was a recommendation from the manufacturer and it turned out to be a good one.

To check neck tension we grabbed a bunch of 6XC and .243AI brass and I pulled the body/shoulder sizer out of the die and ran with just the neck bushing. My .243AI necks are thinner than our 6XC necks by about .003 total. The outside diameters were identical as one would expect but inside diameters showed the expected .003 difference. The little shims that are included for setting the neck sizing depth allowed for coach's neck setup and mine to be accommodated with ease and repeatably. Coach sets his necks up so the last .020 isn't constricted so it rides the walls of the neck area in his chamber. I size my necks all the way to the shoulder/neck junction. Pull one shim, switch sides for it and done.

Everything being so precisely machined is helpful but the real money was the click adjustments for the shoulder bump. It required buying a much better quality micrometer to be sure (I was using cheapies before but they were showing variability so I upgraded) what I was getting but once that came in all questions were answered. Definitely getting .0005" per click of shoulder push back. We'll be running some grouping tests this weekend and then shooting a match with ammo loaded with this die. Between the super consistent neck tension and shoulder push I'm expecting an incremental improvement specifically in SD's and more consistency of chambering ease. No more having a few cases that needed the bump and didn't get it making for hard bolt closure.

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Jason
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Re: New ultra precision dies. Got a set!

Post by Jason » Thu Sep 20, 2018 10:17 am

Thanks for posting this here. The technical details are fascinating to read. Is this rifle planned to be used exclusively for silhouette or will it be used for other competitions that require even more accuracy also?

spamassassin
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Re: New ultra precision dies. Got a set!

Post by spamassassin » Wed Oct 03, 2018 10:26 am

The 6xc's are really meant for PRS and prone long range matches. My silhouette coach and I are going to campaign identically performing loads for the next couple years. We get better scores when we can share wind data and the walking courses are less brutal when we can share a single rifle. So, we'll trade off match to match.

Soon enough I'll have my new 6.5CM built which is specifically being built for silhouette and is getting of these dies too. The consistency of the output product is simply unreal. That, of course, relies on what you start with so things like neck turning for consistency, case weighing, primer pocket uniforming and such come into play which we've avoided strictly wherever possible so far and can no longer ignore. I'm setting up the new brass I just got to do some data gathering around neck tension and case headspace as soon as the barrels are ready to spin on. So it I'll be spending the next few evenings neck turning and uniforming new brass so everything that can be perfect is. I weighed them last night and all but 1 from the lot were within .7gn (Tubb brass) of the median so I'm calling that good to go till neck turning is done. I'm setting up lots brass to .011" neck thickness (from .011-.013 across the lot) and sizing the necks in .0005" neck tension increments across 5 increments up and down from .003" and against factory thickness and .003 neck tension which we'll use as a control and initial load development set. Then I'll take the winner and run that neck setup in .0005" headspace increments down from 0 to .0015 and see if there's any actual difference to be had from tweaking those. Then we'll finish up the unturned brass into turned brass and size with the final winner.

I've got the barrels and brass and bullets for all 3 rifles but still trying to find a receiver I like for the 6.5CM. Coach uses a Savage rifle in a wood stock in 6xc already and I've been on a .243AI chambered Savage in an aluminum chassis stock. The loads are super close but not identical and we want identical this time around.

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