Well, the Allen Magnum family, which included three Allen Xpress wildcats as well is growing rather quickly. The very first of my Allen Magnums was the 257 Allen Mag. This round was designed as a step up in performance from the current kind of the hill in 25 cal magnum rounds which is the 257 STW that you were looking at.
To top what the STW would produce I used the 338 RUM case necked down to 257 and fireformed with less body taper and a sharper shoulder. The new case design offered roughly 3 grains more capacity then what the longer 25-300 RUM wildcat would offer but allowed a much shorter over all length to be used or allowed VERY heavy 25 cal bullets to be used with no worries about magazing length limits.
After building the first test rifle I had the opportunity to test the 257 STW head to head against my 257 Allen Magnum. Both with 30" barreled rifles designed for open country big game hunting.
I orderd some 130 gr Bonded Core FBHP bullets from Richard Graves, owner of Wildcat Bullets in Alberta Canada and had been using them in my personal 257 STW loaded to 3450 fps with top loads.
My 257 Allen Mag would drive these bullets in same length Lilja barrels to a legit 3650 fps.
Comparing lighter weight bullets which I personally feel is simply playing with either of these rounds with any bullet under 120 gr but I tested some 100 gr Ballistic Tips as well.
The STW ripped them out at 3975 fps with top loads while my 257 Allen Mag topped out in the 4080 fps range. Obviously with the smaller bullets my much larger Allen Mag has less of an advantage then with heavy bullets which I was about to find out in dramatic fashion.
Richard Graves made me some custom 156 gr ULD RBBT bullets designed for big game hunting and I loaded them up in both rifles. The STW just broke 3100 fps with this huge bullet while my 257 Allen Magnum comfortably hit 3300 fps and by pushing her hard you could top the 3350 fps level pretty easily.
I see no need to run things that hard so I load it to 3300 fps and leave it there. With a bullet drop derived BC of .820 with that velocity, its hard to improve on anything!!!
I have used the 257 Allen Mag for several field test hunts including a Fallow Buck in Colorado and my personal best Pronghorn here in Montana which was taken 5 minutes into the season at 545 yards with a single 156 gr ULD RBBT.
The 257 Allen Mag is not all warm and fuzzy though. It can not be loaded with any stick powders of any kind because powder bridging occurs and dangerous pressure spikes will result. That said, powders such as AA8700, Hodgdon US869 and WC872 work great in this big 257 magnum and are totally safe and reliable.
Here is a list of the current batch of Allen Magnum rounds: I will list the name of each wildcat starting from left to right, their parent case, primary bullet and velocity potential:
224 Allen Magnum
270 WSM case.........107 gr ULD RBBT.......3400 fps
257 Allen Xpress
300 Dakota case......142-156 gr ULD RBBT...3300-3100 fps
6.5mm Allen Xpress
300 Dakota case......142-165 gr ULD RBBT...3350-3100 fps
270 Allen Xpress
300 Dakota case......169.5 gr ULD RBBT.....3200 fps
257 Allen Magnum
338 RUM case.........156 gr ULD RBBT.......3300 fps
6.5mm Allen Magnum
338 RUM case.........165 gr ULD RBBT.......3300 fps
270 Allen Magnum
7mm RUM case.........169.5 gr ULD RBBT.....3400 fps
277 Allen Magnum
338 Lapua case.......195 gr ULD RBBT.......3200 fps
7mm Allen Magnum
338 Lapua case.......200 gr ULD RBBT.......3250 fps
338 Allen Magnum
408 Chey Tac.........300 gr ULD or SMK.....3400-3500 fps
THis is the latest Allen Magnum to be added to the family, the 510 Allen Magnum. The round on the left is the standard 50 BMG, the 510 Allen Magnum loaded with an 835 gr ULD RBBT in the middle and my 7mm Allen Mag on the right for size comparision.
I have just started testing this round but initial test show 2800 fps may be practical with an 835 gr bullet weight.
Coming soon will be a 50 Allen Tactical based on the 408 Chey Tac case designed to offer standard 50 BMG performance in a much more compact design for heavy tactical use.
Of all the rounds listed above, all are offered as standard chamber options through my shop, Allen Precision Shooting. The only one that is not is the 224 Allen Mag and that is because we are trying to design some bullets in the 100-107 gr weight range that will survive the velocity potential of this HUGE 22 cal round.
Drop me an e-mail at the address in my signature at the bottom of the page if you have specific questions.