There seems to be quite a lot of concern about blowing sabots, in particular, HLBS. I believe they can be used at pressures and speeds well beyond most people’s expectations. I’ve never had a problem at even 38-39g VV110/195B or 200 SST in 209 ignited rifles. Likely less in LRMPs.
If the barrel is rough, lap it! Lightly knurl bullets, use a wad, preferably a dry Maine wool wad, allow cooling after the 2nd shot, and don’t worry about sabot failure.
Concerning pressure. Powders burn the cleanest, have the least temp sensitivity, etc when used at their design operating pressures. Always change to a faster powder and get a load within its operating pressure if wanting a reduced load. 17g Blue Dot/195/200g bullet is much better for a reduced load than 25g of H4198(A terrible load) .
Stay in a powder’s design presdures.
My opinion, using H4198 56-60g in a 24” barrel is far less desirable than 35-37g VV110 for saboted bullets. 10g VV110/50 H4198 is a great 2700+ load.
Additionally, bore sized 250-300g bullets out of a break open with 60-65g H4198 - WHY? For what? Recoil, poorer trajectory, why? A 228g AccuMax or 250g Fury or 200SST or 195B at 2400-2500+ out of a sabot will be as accurate, less recoil by far, and every bit as lethal and with a much flatter trajectory.
I have an acquaintance (crossbow board) who bought a package deal converted Scout. He was having trouble sizing bullets, getting good accuracy, etc. He even missed a deer <100 yards because of some mishap. I had recommended (he had 4759) HLBSs, wool wad 35-38g 4759 and a 195 knurled Barnes/200SST (all anticipated shots <150 yards).
I heard from a mutial friend that this person sold the Scout and went back to smokey MLers, since they’re “easier to use”. Even though I own and shoot exclusively 40 cal MLers now, sabotless only, of course, I believe that 45 cal saboted shooting is seriously underrate! A 228 Pittman, 250 Fury shot with a VV120 load or H4198 (26” barrel) with a HLBS/Wad can reach out to 300+ yards with excellent reliability, accuracy, great trajectory, and comparatively light recoil.
Just some thoughts after 22 years of shooting smoke free.
OOPs!
Please excuse this somewhat inappropriate placement of this post. I understand that Hank’s 9/16” BP has an extension to fill the chamber.