well, for those of you who might be interested, here is some data that I compiled from shooting different rounds through my 6.5" Tracker 455. Now I do not advocate doing this as your results may vary. These loads are above published limits for this gun but seem to be ok. I actually ended up shooting/loading these rounds by sheer accident. I was not planning on doing this the 1st time out but a set of unfortunate circumstances got me these results in a hurry.
A while back I purchased a pound of what I was told was AA#5 to use for loading 45acp. The guy who ran the store sold reloading stuff and had a large container marked aa#5 which he used to give me my 1 lb to try. For everyone out there, if it isn't a sealed factory container of powder, don't buy it!!! This was a first for me and now I know better. Without knowing what AA#5 looks like, we loaded about 10 rounds with 9 grn behind a 185gn Hornady XTP bullet. This is a safe middle of the range load for a 185. I shot these 10 rounds from my full size 1911 and they felt fine. We loaded 150 more. These were the 1st rounds I fired through the 455 when I got it. They seemed much stouter in the revolver. I grabbed a box of ww white box 230 ball and shot a couple of those rounds and they were noticeably softer :???: I figured we screwed up something and stopped shooting. When I got home , I pulled a few bullets and weighed the charge. 9 gns exactly. Things didn't seem to jive so I took my chrono out the next time. Shot the 1st round and got 1250fps from a 185gn bullet. shot 10 more and all the same. Shot some of the ww white box and got somewhere around 900. What ever I was loading was way above what I should have been getting from AA#5. The powder is a flake and I believe it to be Unique. If so pressures are much higher than standard acp loads. By the velocities I am guessing near 45 super levels. maybe a tad less. Maybe around +p+. anyway, we stopped shooting and counted our blessings.
The gun is fine and seemed to handle the ammo without issue. I checked the cylinder and it shows no signs of bulging. The brass was also just standard 45 acp brass and showed no pressure signs or cracks. It came out easy and can be slipped right back into the cylinder. We also shot a few rounds through my 1911 and my hk45c. both showed no brass issue. However, on my Taurus 24/7 oss, the chamber is the most unsupported of all my 45's. Fired brass from this gun has a bulge at the base and will not re-chamber. The HK seems to have a fully supported barrel as well as my 1911. Of course the revolver is 100% supported. I think with a slower burning powder than unique, one can achieve these velocities with even less pressure than I was probably creating and have a load that comes close to 45 super. It would seem that the brass issue is over rated if you have a fully supported barrel.
I can also say that the kick is pretty stout. It definately lets you know you are shooting something more powerful than standard 45 acp. I don't think I would want to even shoot something along the lines of 460 Rowland out of this gun due to the light weight and recoil.
Oh, and we also had loaded 10 rds of 7gns behind a 230 fmj rn before we had figured out what was going on. They clocked around 1050fps out of the tracker.