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Old 06-16-2021, 08:28 PM
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Nomercy448
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Default 6 Dasher: Case Forming & Load Development

I have the opportunity this summer that I just replaced a barrel and need to do new load development for my PRS match rifle AND just replaced a batch of brass and have to do some case forming, so I thought I might share some musings and photos of the processes.

Since Dasher brass is only available from a few select options, and because I have has some issues with the new Alpha brass, I choose to form Dasher from Lapua 6mm BR brass. There are generally 4 options to form Dasher from BR: 1) bullet jam fireforming, 2) Cream of Wheat fireforming, 3) false shoulder fireforming, and 4) hyrdoforming. Considering all of the fireforming methods consume powder and primers, and of course, components are exceptionally difficult to come by during this Covid crisis, and because I already have the gear, I opted to save powder, primers, and barrel life and hydroform.

Iíll share more photos and details in a few days, as I move out of the ďwet workĒ into the final sizing, and Iíll also share the seating depth and charge weight development process I use once the cases are done, but for tonight, Iíll share the gear I use, with results to follow.

A word of warning for anyone considering hydroforming - itís a labor of love. The process is tedious, time consuming, and itís certainly not something which is favorable to do on your conventional reloading bench in a typical reloading room. I end up with about a half liter of sizing lube laden water on my bench and floor for every hundred rounds.

The process is pretty straight forward, press empty primers into lubricated virgin 6mm BR brass to seal the case, insert the brass into the press, fill with water, raise into the hydroform die, top off the water, insert the piston plunger, whack the plunger with a hammer, remove the case from the press, deprime. Not having a full 100 of fired primers to use as plugs, I was at the mercy of cycling through 15-30 rounds at a time, which left me running around 1min each per piece of brass, finishing each hundred count box in a touch over an hour and a half.

Moving my press outside to accommodate the waterworks, I used a Black & Decker Workmate clamping bench to support a Lee Anniversary press. Follower beware, I have used this Workmate for this several times, and I have expected to break the little bench on every occasion. But it has held up for a few thousand rounds of hyrdoforming so far. I own the Whidden hydroforming kit, which includes a solid case holder (no primer hole), the hydroforming die and plunger, and a squirt bottle. Hornady also offers custom hydroforming die kits, including the Dasher die as a relatively standard (albeit not high inventory) stock item. Iíve used both kits and they both work similarly, and both work very well.

Since I had to cycle my spent primers among cases. I use a Lee hand press and a Lee Universal Decapping die for depriming - note: the Lapua 6BR brass I am forming uses small diameter flash holes, so I spun the decapping pin in a drill and sanded the diameter slightly to clear the smaller flash hole. To prime, Iím using an old round tray Lee hand primer. Work goes pretty smoothly if you 1) have enough spent primers to fill all of your cases in one batch, or 2) have a young helper to deprime and reprime cases - and my son has been a great help to speed up cycle time in this batch of brass.

And of course, a particularly important tool in this task is a hammer. John Whidden recommends a relatively light hammer, swung fast, but in my experience, I get better results using a beefy hammer, choked relatively short, and giving 3-4 solid whacks to cleanly form the case.

Not pictured here is my patio table, which houses all of the priming/depriming tools, extra water, case lube, and 4 buckets of brass (virgin, primed, formed, and finished). Whacking the die repeatedly makes this little bench bounce quite a bit, and tools have a tendency to walk off of the bench - so a second table to hold the ancillary equipment and brass is nice.



Iíll take some pictures tomorrow or Friday of the virgin brass beside hydroformed and final sized brass, and describe the set up and options a bit more. But I will say tonight that there are two options in setting up the hydroform die - or rather three. Whiddenís instructions state the die should be ran all the way down to touch the ram at itís highest point, which does work. In this particular barrel, it would have left about 4thou head room between the case shoulder and the chamber, so I elected to adjust the die slightly out to match my rifle. In this case, there are two options: 1) hydroform just far enough to just make contact, meaning screwing the die out progressively farther until the bolt wonít close, and then screwing back in slightly. Then these cases are loaded and the slightly radiused shoulder is final formed by fireforming. 2) hydroform sufficiently to not allow the case to be chambered, then push the shoulder back in the sizing die to match the rifle chamber. Considering my situation with match preparation and barrel prep, Iíll be shooting half of this batch of virgin brass at a 2 day PRS match in two weeks, so I set the hydroform die to over-blow the shoulder, so I can put it back precisely with my sizing die. Note - both methods do require final sizing to control neck tension.

Iíll be seating likely Friday and Saturday, and live firing for load development at least by Sunday, and using my standard Satterlee method with a twist of OCW, so Iíll detail my seating depth determination method and my load work up in following replies here over the next week or so (and will plan to have a more detailed thread on load development methods).

More to come...​​​​​​​
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