Thanks to Kevin for doing this. Got mine back today. Test load was 2-5 times fired Nitro hull, Win 209 primer, 20.4 grains Green Dot, DR XL-1 wad, 1 oz 7 1/2 hard shot. Average pressure 8200 and Average velocity 1260. Hi low spread on velocity of 69. Was not happy with velocity deviation but don't really know whats normal.
LOL...2 hours after my initial post got the results.
Loaded on a 15 yr old MEC 9000G. The MEC bushing used drops 17.6 grains of Claydot time and time again, the bar was bored out to drop exactly 1 oz. of hard #8. I randomly selected seven of twenty five shells for the testing. No attempt to cull shells for the different lengths (as seen by the crimp depth) or any other differences. Anyway... here's the data, pretty much what we all expect.
This is the load I use for single and handicap practice, 16 yd. registered targets, and all sporting clay targets both registered and practice.
Thank you Down Range Manufacturing, you guys are the best.
Here's how Kevin @ Downrange Mfg. measures crimp depth during tests:
Modify a $20 digital caliper with an abrasive grinder...<br><br><br>
Set the caliper to the overall length of the shell...<br><br><br>
Zero the caliper while measuring the overall length...<br><br><br>
Shift the caliper a bit, set the cutouts in the fixed jaw over the crimp shoulders and measure the crimp depth...<br><br><br></center>
Take the measurement right next to the shoulder roll. The shoulder depth determines the resistance the crimp provides to the movement of the shot load and the amount of chamber pressure that can build up before everything goes "POP". The depth of the center of the crimp has no meaningful effect on peak pressure and serves only to hold the shot in place.
Crimps are important because as crimp depths vary so does the peak pressure produced by the load. A depth of .055" is considered the standard. A .010" change in crimp depth can produce a 1000 PSI difference in pressure. As pressures vary so does velocity.
MK--Thanks i didn't know that. I think i'll take my cheap Harbor Frieght caliper and modify it to keep an eye on my crimps. Heck gives me something else to do. I'm curious as to what mine measure now. Have to get out the Dremel in the morning.
For those that don't have an accurate caliper or want a quick check. Here is a trick someone showed me, a dime is almost exactly .055 inches thick, the standard depth for shotshells. Grind it down to a diameter that fits inside your crimp and voila ...instant depth gauge. Also, as was pointed out to me by Unknown1..... a new dime weights 35 grains, a great scale check. Unbelievably our government made something useful and affordable (dont worry, they wont make that mistake again).