Yep, its the 224 AM. Just started the testing and development a month or so ago. I have been held up a bit by waiting for a neck reamer to get in so I do not have to turn my case necks. Is a real pain.
Anyway, got the 107 gr ULD RBBT up to 3400 fps but had some bullet failures in the 1-7 twist barrel. I suspect a 1-8 6 groove would be a much better choice.
The 100 gr pills do not seem to come apart as easily but I have not tested them as hard either yet.
The 224 AM is based on a full length 270 WSM case necked down to 22 cal with the Allen Magnum shoulder and body configuration.
I am waiting on the neck reamer to do more testing to determine if I have enough case taper in the design. I was getting some sticky extractions at +3350 fps with the 107 gr pills with no other pressure signs so want to test this more before submitting the specs for dies.
From early limited testing it looks like 3400 fps will be easy with the 107 gr ULD RBBT and we will see on the 100 gr ULD RBBT. I may have to try another barrel as this 1-7 3 groove seems a bit hard on bullets.
Also, this is only a 26" barrel as well.
I expect the neck reamer to show up anytime so when that gets here I will fix my chamber and get back to testing. From early drop numbers it looks like the 100 gr and 107 gr bullets are producing BCs in the .600 and .625 range but this is from very limited testing so much more testing needs to be done.
There are several guys shooting Richards 100 gr ULD RBBTs with good results.
Here is a pic of the 100 gr ULD RBBT. Those are 140 gr and 160 gr 7mm Accubonds flanking the skinny, long 22 cal bullet. Not to bad, a 22 cal bullet longer then a 140 gr 7mm Accubond!!!