Hi all, I had some time to kill today, so I ran some numbers through Quickload to see what might be feasible at what pressure levels. Could someone measure the water capacity in grains of a straight wall 4" 50BMG case? I measured a couple of cut down ones and estimated 332gns of H2O.
It looks like you should be able to get a 1000gn bullet to 2060fps at 26.9k and 2660 at 59k. I looked at some 1500 and 2000 gn bullets also. You would have to seat them out far to get high velocity, but it should be possible to get the 2000gn up to 2000fps in the falling block and keep it under 60k.
Will the 1:20 twist of the PacNor bbls be suitible for 750 or 1000gn cast boolits in the 1600-2000fps range?
Still haveing thoughts about my 10ga double action.

LAR--My 12GA FH cases are 3.8 in long and hold 340 gr
water.Holds 300 gr of ball powder and 270 gr of 4831,
to the base of the bullet.
A full load of ball powder will get a 1000 grain bullet
out at 2800 fps, at 45,000 psi.That is by my formula that
has worked on all of the big stright cases.Ed.

Lar--The 1-20 twist will work OK at those speeds, for
those weights of bullets..Be interesting to see what you
can do with that double..Ed.

LAR45- Pretty good estimate of water capacity!!!. I measured 331 grs on two cases. I've used 1:20 on the .700 RLG( Pretty similar to a .700 JDJ but my own minor changes) and it stabilized 1000 gr to 2000 gr Bore Riders just fine. This is consistent with Butch Searcy's observations so I don't see why a .729 Bullet won't work equally well. By the way, You can easily get 3000 fps out of a 1000 gr .700 with H414 powder and a 32 inch three groove barrel. I fired the 2000 gr Bore riders at 600 yrds and got a 3.2 inch, 5 shot group, so I think they were pretty stabilized.-Rob

Robgunbuilder, I am not a big bore shooter but make molds for them so I have an interest in this topic. When you say your gun shot accurately were you talking cast bullets or some other kind? Cast bullets do not like to be spun more than necessary which would be the case with a 1:20 twist. However, you have the experience here and I don't, so I would be curious to know more about your loads.

I'm going to order some 4140 and see if I can turn out a mono block to fit the 10ga action. I found a place that has 12ga blanks for $25. I still have to see what the outside dimensions are. I was thinking of a fully rifled barrel, but now I'm wondering about a rifled choke tube and if it would work in this application with the CHEAP $25 barrels. I think I would want more of a 12ga heavy or 725 Collarbone Express than the full 12gaFH. I would probably be better off getting the Pac-Nor barrels to make sure they were thick enough and made of the right material to handle higher pressures.