Going through the pages in this thread will show you some DTAC loads, note many of them have longer than .104 freebore.
I run 115 DTACs in 6 Dasher. Alpha brass. CCI450s. Suggest you start at 30 grains of Varget. I tried 30, 30.5, 31.0 of Varget with 115 DTACs - all shot great groups with low SDs. I chose 30 grains of Varget with 115 DTACs because I want to "see" impacts so choose lowest speed/recoil. Proof 7.5 twist prefit, Competition Contour, 26 inch. 30.0 grains Varget = 2705 and SD 4.9 sample size 5.
I ran 105 Berger Hybrids over Varget in previous barrel. I had DTACs left over from previous 6XC barrel so I am running them for this barrel. I wanted to see if the 115s would make any difference seeing impacts. For me, they are both accurate. I got tired of chasing Bergers but they seem more available now.
If your running alpha brass cut that load down another 1.0 gr at least and work up. I run 112gr match burners with 31.4gr of Varget in Alpha brass. I think Lapua holds about a grain more.
That would be my plan with alpha brass. You will probably find a load for 105's in the 31.x - 32.0 range but it's worth it to start low and work up.
It depends on the cartridge being tested, a 50BMG 2 full grains barely changes the speed of a 750 gr bullet...it takes 5 grains to get the big bullet to move a bit faster.
IMO I’d start at 31.4 and go up .1 increments. Your group size should be the determining factor more than the velocity. Or you can get your velocity as close to 2850 and fuck around with seating depth to tighten your groups. Again depends on your tools and how much time you want to spend down that rabbit hole
So you say one round velocity drops just over 800 FPS?! That is crazy and, even after thousands of Dasher rounds down barrels, I have never seen or talked to anyone that has seen that.
AT4 and FX120. Calibrated before each session and apparently works perfectly...
Yep, and it happens for just one round and the subsequent one does say 2790 and then all the other hammer back at 2815...
While I have no idea what the cause of the drastic loss of velocity is, I feel like the drop in the round after is caused by all the soot (maybe even unburned powder) left over from what I would consder a "dud" round. As far as it being caused by media left in the case, I would think it possible if it clogged the primer hole enough but not sure it would cause that big a drop (if at all) in velocity.
31 gn, pretty average afaik. not on the hot side but also can not be considered low.
I add a little of brass polish to the corn cob in the tumbler it can be that some is left inside the case very randomly and since the load is just around 90% of case fill, this could be one possible root cause. I will hold back my OCD about shiny brass and avoid the polish and see what happens.
Can not exclude that in principle. I store them with powder in temp controlled wine cellars, so it's not my fault and my usual gun shop is also storing everything properly but 450s are becoming so scarce that you have to try new suppliers and then you never know how they have been kept.
Yep this happened to me as well and this could be wel be a short charging scenario. In fact once the powder is dispensed into the case I don't have a last check routine just before seating that ensures that the right powder amount is really in each case. I usually seat one-by-one and have a visual quick check of the level of powder in the case but I don't have a bullet proof check tool like an hedspace gauge or the lovely case neck gauge from ballistic tools...
at least two options are more than reasonable thanks!
Thanks!
If your going with an Alpha reamer I'd go with at least a .130....my BRA reamer is .145 and works well with 105s through 110s I don't shoot 115s but I am sure they would work fine...If your going with the heavies .154 might be even better.
