I bought a mystery barrel for a Stevens 44 1/2 that is marked 17 A&M.  I had assumed it was something Paul Marquardt had done using a 17 Javelina reamer and cutting the rim recess on a lathe.   

When it got here today, it’s a dandy looking barrel, but for sure it was not chambered to use a cartridge based on the 222 Rimmed case.   

So I grabbed a piece of 32-20 Winchester and the rim fitted perfectly.  Next I tried a fired 17 Ackley Bee case and it went in snug as a bug in a rug.  A 218 Bee case stands about .022 out from seating.  Taking a look in the Handbook of Cartridge Conversations, that is about the right neck length for a 17 HeBee.   

I was unaware of there being a 17 A&M, but in poking around on the internet looking for more on the 17 HeBee I stumble on this 

“Besides the Ackley Bee there's a 17 A&M, 17 Killer Bee , 17 HeeBee and your 17 Mashburn. Some where on the internet is a picture that shows all 5 lined up. I spend a half hr trying to find it with no luck. I was thinking your case has the shoulder blew forward and was between the Killer Bee and HeeBee case. Maybe Ken Howell book on cartridge conversions would have it but I don't have access to my copy right now. Hopefully another member has a copy available.”

I’m wondering if anyone can point me in the right direction to find a bit more on the 17 A&M.

maybe this article will help?

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The barrel arrived and first thing I did was to cast the chamber and it is a 17 A&M Bee.  Almost, but not quite identical to the 17 HeBee. I have reamer prints for both.  

It should be easy to make from 218 Bee, but given the current state of things, I have a couple bags of brand new Winchester and then it's a matter of making it up from Starlinebrass 32-20 Winchester. 

I'm thinking that by annealing, then using a 25-20 and 218 die and running them in short, annealing again and then my 17 Ackley form die or Bullberry double ended die until the action just closes will get the neck and I'll be about there. I should only be left with reamming if it needs it and/or turning the neck.   

Might be quicker getting there by starting out with .25-20 WCF brass.