New 270 Allen Mag prototype....

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   Well, got some work done in the shop and actually had some time to play with my stuff.  As most of you  know my 270 Allen Mag was based on the 338 RUM case just as its 257 and 6.5mm brothers are.  
Well, after testing the 270 AM out I wanted to see how it would perform punched out to use the longer 7mm RUM case as a parent case, which by the way is dramatically easier to form cases out of then the 338 RUM.
I pulled the barrel on the Savage test rifle, punched out the chamber to accept the longer 7mm RUM based 270 AM and screwed her back on and headed to the range.

These are from left to right, the 257 Allen Mag loaded with the 156 gr Wildcat  ULD to 3300 fps, the 1st generation 270 Allen Mag loaded with the 169.5 gr Wildcat ULD to 3350 fps and the 2nd generation 270 Allen Magnum  again loaded with the 169.5 gr Wildcat ULD.  I do not have the velocity data for this round yet as I have not reached even good working pressures yet.
I started with 18 test load/ fireforming loads loaded with 8700.  Startign with 90.0 gr and stopping at 95.0 gr each with three rounds to test group size at 500 yards as well as velocity and consistancy.
All groups averaged less then 3" at 500 yards with the first three groups coming in under 2" ctc at 500 yards.  The last three opened up to around the 3" range I am sure because of the powder fouling created by the low pressure loads using 8700.
Velocity was very consistant with the highest extreme spread being 25 fps for the six test groups and starting at 2945 fps at 90.0 gr and 3035 fps at 95.0 gr.  Pressures were barely high enough to blow the shoulders out.
Still groups were very good for fireforming loads at 500 yards in spite of the low pressure levels.  This group was from the 92.0 gr load and is one of my personal best three shot groups at 500 yards.

Not to bad for fireforming loads!!!  Again, this is not what this rifle averages.

  Average group size for the six groups was in the 2.7" range.  Still getting an average of 1/2 moa at 500 yards with fireforming loads is not to damn bad!!!
I will continue up the powder scale until things top out.  The shorter version hit 3350 fps using Retumbo with a top comfortable load being 3300 fps.  Even in the shorter case with the heavy 170 gr class bullet, Retumbo was a bit fast burning.  
I would be suprised if the 2nd Gen 270 AM does not push 3450 fps with 8700 as load densities will be able to reach nearly 100% I am sure.  Powder capacity for this version is 8 grains more then the first when seating bullets to the same OAL length.
I will keep you posted.  From what I have seen as far as just forming brass, this 2nd Gen design is vastly superior to the first.  
Good Shooting!!
Kirby Allen(50)

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Fiftydriver Members Profile Send Private Message Find Members Posts Add to Buddy List .243 Winchester Joined: 06 April 2004 Location: United States Status: Offline Points: 189	Post Options Post Reply Quote Fiftydriver Report Post Thanks(0) Quote Reply Topic: New 270 Allen Mag prototype.... Posted: 30 January 2005 at 13:25
	Well, got some work done in the shop and actually had some time to play with my stuff. As most of you know my 270 Allen Mag was based on the 338 RUM case just as its 257 and 6.5mm brothers are. Well, after testing the 270 AM out I wanted to see how it would perform punched out to use the longer 7mm RUM case as a parent case, which by the way is dramatically easier to form cases out of then the 338 RUM. I pulled the barrel on the Savage test rifle, punched out the chamber to accept the longer 7mm RUM based 270 AM and screwed her back on and headed to the range. These are from left to right, the 257 Allen Mag loaded with the 156 gr Wildcat ULD to 3300 fps, the 1st generation 270 Allen Mag loaded with the 169.5 gr Wildcat ULD to 3350 fps and the 2nd generation 270 Allen Magnum again loaded with the 169.5 gr Wildcat ULD. I do not have the velocity data for this round yet as I have not reached even good working pressures yet. I started with 18 test load/ fireforming loads loaded with 8700. Startign with 90.0 gr and stopping at 95.0 gr each with three rounds to test group size at 500 yards as well as velocity and consistancy. All groups averaged less then 3" at 500 yards with the first three groups coming in under 2" ctc at 500 yards. The last three opened up to around the 3" range I am sure because of the powder fouling created by the low pressure loads using 8700. Velocity was very consistant with the highest extreme spread being 25 fps for the six test groups and starting at 2945 fps at 90.0 gr and 3035 fps at 95.0 gr. Pressures were barely high enough to blow the shoulders out. Still groups were very good for fireforming loads at 500 yards in spite of the low pressure levels. This group was from the 92.0 gr load and is one of my personal best three shot groups at 500 yards. Not to bad for fireforming loads!!! Again, this is not what this rifle averages. Average group size for the six groups was in the 2.7" range. Still getting an average of 1/2 moa at 500 yards with fireforming loads is not to damn bad!!! I will continue up the powder scale until things top out. The shorter version hit 3350 fps using Retumbo with a top comfortable load being 3300 fps. Even in the shorter case with the heavy 170 gr class bullet, Retumbo was a bit fast burning. I would be suprised if the 2nd Gen 270 AM does not push 3450 fps with 8700 as load densities will be able to reach nearly 100% I am sure. Powder capacity for this version is 8 grains more then the first when seating bullets to the same OAL length. I will keep you posted. From what I have seen as far as just forming brass, this 2nd Gen design is vastly superior to the first. Good Shooting!! Kirby Allen(50)