Necchi:
They use 1137 GB quality for ML barrels.
Here is what I think occurred that caused them to "abandon" you.
From what I have read they had a military contract.
The military, unlike most ML builders, takes barrel steel alloys VERY SERIOUSLY.
If GM had 1137 in the same BUILDING or maybe even the same property, that they were making contract barrels in and it was found by inspectors the entire contract would instantly be null and void, done, over, no payment, nothing. So companies that do military contracts are pretty well "stuck" once they get the contract.
So they can suspend ML barrel production for a year or so and make a LOT of money or they can not bid on and win a military contract and keep making barrels for what is a relatively tiny market. OR they could set up and make ML barrels from 4150. Of course then people would whine because they were hard to file. The complain enough about 1137
From a BUSINESS standpoint what would YOU do?
Personally I am glad they are back in production.
Its not like a certain powder maker who years ago told all the ML shooters to shut up and be glad they could buy powder at all since they made (and still do) a LOT of money on military contracts. But of course at that time there was no competition. If the complaints got too loud they threatened lawsuits. Yeah...
So remember there is a big difference between can't and won't.
So cut GM some slack its not like they were telling ML shooter to shut up and take it or leave it.
Dan