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Allen Mags?
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<blockquote data-quote="Fiftydriver" data-source="post: 86220" data-attributes="member: 10"><p>Brian,</p><p></p><p>For the requirements you list for your upcoming project, the Dakota would be my very first choice as it will meet everyone of your requirements nearly perfectly. I am not sure if you will reach a full 3100 fps with the 156 in a 26" barrel but you may come very close. Will be interesting to see. I guess I need to build a 257 AX and find out!!!</p><p></p><p>My 257 Allen Mag with the 142 and 156 gr ULD RBBTs actually has about 10 grains more capacity then it really needs with the current powders available such as WC872. IT certainly works well but it would work even better with slower burn rate powders but that would equate to using coal for gunpowder I think /ubbthreads/images/graemlins/grin.gif! </p><p></p><p>That said, I would predict that the 257 AX would come withing 200 fps of matching the performance of the much larger Allen Magnum. Perhaps even a bit closer then that but we will have to see. With the 257 caliber, I will admit the AX will be a much more user friendly design as would your wildcat and very similiar in performance.</p><p></p><p>In the larger calibers though the Allen Magnums will offer a larger peformance advantage simply because the current powders are more appropriate for these bore volume to case volume ratios.</p><p></p><p>The reason I went with the 300 Dakota over the 7mm Dakota was that I wanted to drop case capacity roughly 10-12 grains off the 257 and 6.5 Allen Magnums. Playing with some sample brass of both the 7mm and 300 Dakot I found the 300 would give me exactly what I wanted.</p><p></p><p>TO be honest, the 7mm case would work just as well and if you like longer necks it would be the one to use for sure.</p><p></p><p>I did not move the shoulder forward on the 6.5 AX. When I neck down the brass, I simply maintain the original 32 degree shoulder and then use a 0.004" crush fit to headspace the chamber on a virgin case to control case stretching. This is the simplest way to do things, no shoulder position changes really, just the fact that decreasing the neck diamater will move the shoulder/neck junction farther forward.</p><p></p><p>I ordered in 200 pieces of 300 Dakota brass and instantly found some problems with consistancy. It appears they are in the process of switching over to a different alloy as I got two very different types of brass in this order. Three of the 20 round boxes had brass that was very bronze in color. Similiar to the Lapua cases. The other two boxes were bright yellow, like that of Winchester or Remington.</p><p></p><p>The interesting thing is that the bright yellow colored cases weighed on average 23 grains less then the bronze colored cases!!!!</p><p></p><p>Internal case capacity was within 3 grains on average with the lighter cases having more capacity. Obviously the heavy cases are using a denser alloy in the brass.</p><p></p><p>In load testing, the light cases would top out sooner in pressure then the heavy cases. This is the performance differences I have found so far.</p><p></p><p>Light cases:</p><p>120 gr Ballistic Tip...........3410 fps</p><p>140 gr Partition...............3200 fps</p><p></p><p>Heavy cases:</p><p>120 gr Ballistic Tip...........3525 fps</p><p>140 gr Partition...............3320 fps</p><p></p><p>With the light cases, it was at these velocities that the primer pockets were maintaining tightness. Anything over this would result in loosening primer pockets on the third firing or so.</p><p></p><p>Same with the heavier cases but I did not push the issue to the point of opening the primer pockets to find the limit. The 140 gr Part. level is pretty comfortable as I have 4 firings on these cases and they are still plenty snug.</p><p></p><p>I feel I got a mixed batch of brass as they are trying to switch over to the new brass. Lapua is supposed to be producing the Dakota brass starting this fall and winter so when that happens consistancy will be top notch.</p><p></p><p>Good Shooting!!</p><p></p><p>Kirby Allen(50)</p></blockquote><p></p>
[QUOTE="Fiftydriver, post: 86220, member: 10"] Brian, For the requirements you list for your upcoming project, the Dakota would be my very first choice as it will meet everyone of your requirements nearly perfectly. I am not sure if you will reach a full 3100 fps with the 156 in a 26" barrel but you may come very close. Will be interesting to see. I guess I need to build a 257 AX and find out!!! My 257 Allen Mag with the 142 and 156 gr ULD RBBTs actually has about 10 grains more capacity then it really needs with the current powders available such as WC872. IT certainly works well but it would work even better with slower burn rate powders but that would equate to using coal for gunpowder I think [img]/ubbthreads/images/graemlins/grin.gif[/img]! That said, I would predict that the 257 AX would come withing 200 fps of matching the performance of the much larger Allen Magnum. Perhaps even a bit closer then that but we will have to see. With the 257 caliber, I will admit the AX will be a much more user friendly design as would your wildcat and very similiar in performance. In the larger calibers though the Allen Magnums will offer a larger peformance advantage simply because the current powders are more appropriate for these bore volume to case volume ratios. The reason I went with the 300 Dakota over the 7mm Dakota was that I wanted to drop case capacity roughly 10-12 grains off the 257 and 6.5 Allen Magnums. Playing with some sample brass of both the 7mm and 300 Dakot I found the 300 would give me exactly what I wanted. TO be honest, the 7mm case would work just as well and if you like longer necks it would be the one to use for sure. I did not move the shoulder forward on the 6.5 AX. When I neck down the brass, I simply maintain the original 32 degree shoulder and then use a 0.004" crush fit to headspace the chamber on a virgin case to control case stretching. This is the simplest way to do things, no shoulder position changes really, just the fact that decreasing the neck diamater will move the shoulder/neck junction farther forward. I ordered in 200 pieces of 300 Dakota brass and instantly found some problems with consistancy. It appears they are in the process of switching over to a different alloy as I got two very different types of brass in this order. Three of the 20 round boxes had brass that was very bronze in color. Similiar to the Lapua cases. The other two boxes were bright yellow, like that of Winchester or Remington. The interesting thing is that the bright yellow colored cases weighed on average 23 grains less then the bronze colored cases!!!! Internal case capacity was within 3 grains on average with the lighter cases having more capacity. Obviously the heavy cases are using a denser alloy in the brass. In load testing, the light cases would top out sooner in pressure then the heavy cases. This is the performance differences I have found so far. Light cases: 120 gr Ballistic Tip...........3410 fps 140 gr Partition...............3200 fps Heavy cases: 120 gr Ballistic Tip...........3525 fps 140 gr Partition...............3320 fps With the light cases, it was at these velocities that the primer pockets were maintaining tightness. Anything over this would result in loosening primer pockets on the third firing or so. Same with the heavier cases but I did not push the issue to the point of opening the primer pockets to find the limit. The 140 gr Part. level is pretty comfortable as I have 4 firings on these cases and they are still plenty snug. I feel I got a mixed batch of brass as they are trying to switch over to the new brass. Lapua is supposed to be producing the Dakota brass starting this fall and winter so when that happens consistancy will be top notch. Good Shooting!! Kirby Allen(50) [/QUOTE]
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