I plugged it into QuickLoad, but found that top velocities were not possible with StaBall 6.5 and either 130-gr. or 150-gr. bullets. It is a little higher up on the burn rate chart than the typical choices for the .270 Win.
QuickLOAD predictions for StaBALL 6.5 in some test batches I loaded and shot against H4350 in 6.5X55 with the old 140gn Berger BT bullet were 'out' by some 40 fps equivalent to c.2,500 psi PMax, 'out' as in the program underestimated MVs / pressures. Interestingly, in this application, QL was further 'out' in its predictions for H4350, but in this case by heavily overestimating MVs and presumably pressures. I wouldn't therefore rely on the program with its current S-B default values too heavily.
I wasn't too bothered by QL being inaccurate with either powder as I had expected that. Firstly charges were based on Hodgdon loads data from its online Reloading Center facility for the 140gn Speer SP and being in line with the lower US MAP for the cartridge were pretty well guaranteed to be safe at Hodgdon's c. 45,600 CUP pressure units when fired in a modern match rifle (CIP MAP is over 55,000 psi for the SE variant and many people on this forum load the cartridge and improved variants to 60,000 psi or more with Lapua or other quality brass.) Secondly, I didn't know the water capacity of the Norma brass I was loading it being on the first firing, so used that for Lapua. Also, and to greater effect, the COAL employed saw a huge jump to the lands which will depress pressures vs QL had I input the likely COAL at the lands (but would have seen the bullet hardly, if at all, held by the case-neck). The QL incremental charge runs were done purely to gain an idea of possible pressures when actual MVs were matched to those predicted by the program.
The purpose of the exercise was to compare results between H4350 and S-B 6.5 which being in the UK, the former has been banned by health & safety regulations and the latter is one of its possible alternatives, moreover actually available here right now unlike many suitable European powders.
Hodgdon's 6.5X55 140 Speer SP max loads of 44.0gn H4350 and 45.0gn S-B 6.5 were worked up to, According to Hodgdon, StaBALL should have produced
considerably higher velocities at those levels - 2,722 fps vs H4350's 2,617 fps both at ~45,700 CUP chamber pressure in a 24-inch test barrel.
Actual results gave very similar MVs in my 30-inch Bartlein - 2,768 fps for 44gn H4350; 2,761 fps for S-B 6.5 at 45gn. QL predicts very similar pressures too at those MVs, ie c. 49-50,000 psi which is exactly what you'd expect from a US powder supplier for this cartridge given its relatively low SAAMI pressure ceiling. On this basis, in this application, S-B 6.5 appears to be a tad slower burning than H4350, but the two are similar enough for the new powder to be suitable in those applications where IMR and H4350 are used and proven.
What is missing is the extra performance that Hodgdon claims in order to 'push' this powder 'family' publicity and marketing-wise over the imported ADI-manufactured Extreme grades. (I'd imagine the company is desperate to see VarGet to S-B 'Match' and H4350 to S-B 6.5 transfers given lower StaBALL costs and possibly better availability with this domestic [St. Marks, Florida] product.)
The loads I used are well under European CIP 6.5X55 SE MAPs and also what the cartridge and better brass are capable of. It may be that the StaBALL grade will allow considerably higher charges and MVs to be worked up to in this cartridge, 270 Win and others over existing grades. TBH, I'm a bit dubious that any improvements in this respect will be significant, so it may well be that better price and availability will end up being its main selling points. However, if H4350 is a top choice for the 270 with your bullets, it should do OK; if you load the 4831s for peak performance, then it'll likely not do so well for MVs.
Using QL's 270 Win default case 'water overflow capacity' of 67gn and my fireformed Lapua 6.5X55 brass' 58.1gn equivalent, 270 Win has an estimated capacity to bore ratio of 1,111 and 6.5X55 in my actual circumstances a slightly lower 1,056 which isn't a large enough difference to need any significant change in powder burn rate requirements. So what I found in the 6.5 should apply in principle to the 270, but of course with your actual rifle, brass etc YMMV.
