Dave,
Velocity potential is an interesting topic with the Allen Mags. I will go through each one and respond to the powder issue.
With the 257 and 6.5mm Allen Mag, you simply do not have an option to use the stick powders. This is a safety issue here. In fact the rifles I ship in these calibers are clearly marked on the barrel that they have to use only Ball powder.
This is because the case capacity is so large and they are so wide in the shoulder for their bore size that a powder bridging problem occurs with stick powders. Even powders of the correct burn rate.
For light weight bullets in the 100-120 gr range, Magnum from Ram shot is showing promise but for all around use, AA8700 is working best for bullets from 100-130 gr. For bullets from 130 to the top of the scale(156 in 157 and 169.5 in 6.5mm) WC872 is the best powder I have found to use.
In these two Allen Mags you simply don;t have an option. As far as velocity. The 257 Allen Mag will drive a 100 gr Bonded Core FBHP to 4090 fps in a 29 3/4" barrel with 107.0 gr AA8700. In the same exact barrel as a 257 STW at a full 30", it would top out at 3950 fps with Retumbo so youcan take what you will from that comparision. Again these numbers are out of the same barrel, originally a 257 STW, and then slightly shortened and rechambered to my 257 Allen Mag.
270 Allen Mag.
This round has a bore diameter large enough to allow use of teh stick powders. In fact with the 130 to 140 gr bullet weights you will get higher performance with powders such as Retumbo and Rl-25 but again at the expense of higher bore heat and top velocity will only be 50-75 fps faster then with the ball powders. Again, I would much rather get longer barrel life and cut 50 fps off the load. This amount of velocity is totally meaningless at extended range, well, any range for that matter.
For the heavy bullets such as the 169.5 gr ULD, I honestly have not tried any stick powders. I started with WC872 at 90.0 gr and worked up to 105.0 gr until the primer pockets loosened up and then dropped back down to 102.0 gr for a max working load.
Top velocities averaged 3394 fps with extreme spreads for ten shots in the high teens, low 20's which is fine with me.
The load I actually use is 100.0 gr WC872 which produces right at 3275 fps. Nothing flashy but a .750 BC bullet at nearly 3300 fps is a thing to behold when she lands at 1000 yards. I am still amazed at the quickness that bullets get on target at this range. You better be ready or you will miss the hit.
Compared to the 338 Kahn driving a 300 gr ULD to 3050 fps, it makes the Kahn seem like a lazy dog as far as time of flight is concerned. Again this is about 20% because of the round design and 80% of the Wildcat Bullets.
I want to stress this to everyone. The Allen Magnums are great high performance rounds in and of themselves but it is only when combined with the amazing Wildcat ULD RBBT or ULD Bonded Core FBHP bullets that you see the extreme performance potential of these rounds.
Without the hard work and genious of Richard Graves who has offered as much to these projects as myself, the results would not be nearly as impressive as they are. He has been an equal partner in every Allen Mag so far and the ones in the works and I just hope he knows how greatly I respect his knowledge in bullets and ballistics and above all else how much I honor his friendship. Without Richard Graves there are no Allen Magnum rounds.
So back to the question of velocity and powder choice. I don't know with the 270 AM and the heavier bullets. I have not had a reason to think the grass may be greener somewhere else. This is my point with the Allen Mags, you find a load that is a good consistant load and then use the system in the field and you will see the rewards first hand.
I will say I am not going to try the stick powders in my rifles but I will develope loads in customers rifles for the componants they want to use before I ship the rifle.
7mm Allen Mag
Obviously this round will work well with a variaty of stick powders, for light bullets, H-1000, IMR 7828, RL-25, Retumbo. For middle weight bullets, Retumbo, RL-25, H-50BMG. But I suspect for the heavies, 175 to 200 gr ULDs, WC872 will again be a top performer and again with the increase barrel life, I will take even 100 fps drop in velocity. These rounds have plenty of horsepower as is, even if you are 100 fps off the top velocity potential, again this is because of the Wildcat ULDs.
So yes, in some cases, top velocity may be with stick powders but I hold barrel life to a higher premium then getting the last fps of velocity out of my rounds.
Flame cutting is more controled by throat to bullet fit then by the rifling design in my opinion. The way I look at it, I want the bullet to seal the gas behind it in the throat area so that it does not blast around the bullet and flame cut the throat and origins of the rifling. This is my theory, take it for what you will.
In my rifles, when you chamber a round loaded with a Wildcat bullet, often you will see contact rubs on the bullet body from the throat. This is how tight the throats are. While this does increase pressure slightly it is of no concern since the loads are developed for this throat design from the ground up. Kind of like seating bullets into the lands. If you develope the load from the start with this seating method, there are no pressure problems, same thing here.
As such they are very tight fits to the bullets which is by design to limit flame cutting as much as possible. This is the killer of the throat, limit this as much as possible and the battle to good usible barrel life is much easier to contend with. Again, this is my theory and so far it seems to be holding true.
I actually started doing throats like this by accident. When I designed my 338 Kahn, I had the reamer come with a .3385" throat diameter. Well, I quickly realized that most 300 gr bullets, Sierra or Wildcat, have a bullet diameter of roughly this same diameter. I have shot the rifle and while I can probably not reach the peak velocity I could with a slightly looser bore, I have about 500 rounds down the pipe and the throat is still in VERY good shape, even using H-50BMG for most of my shooting which I have now switched for WC872.
So this is the system I started using and so far it has been producing longer barrel life then the standard 0.0005" over bullet diameter system.
Good Shooting!!
Kirby Allen(50)
