I have the AX-ELR and an AR-50 and was surprised how well the AX brake performed on the lighter rifle. There are not too many people making brakes threaded M24x1, I did find this one
https://terminatorproducts.co.nz/t6-brake/ but their own video shows that it actually increases recoil over the factory brakes tested...
I searched real hard. Where did you find M24x1 for the MRADELR? If that is in fact the factory spec, then have an extension built, threaded for whatever you need.
BTW, Barrett is normally 7/8-14 or 1-14 thread.
Bad link on the Terminator YT video, s/b
The AR50 brake is, as best I know, and have shot, the most effective at recoil reduction for .50BMG and variants. Alex, please try and find the VHP comparo article. Was the K&P compared?
State Arms/East Ridge builds a 3" fish gill but I have no idea if they would cut one with a metric thread. See
http://www.statearms.com/rifles/accessories.php
US Arms showed what looked like a very efficient brake at SHOT, maybe 5 years back - the very, very big brother of their current offering of that design (volume sales opportunities most certainly moving the company to the current offering). Suggest you contact them (see
https://www.usarmsco.com/product/talon-905-muzzle-brake/) to see if their "XXXL" model is available AND if it has ever been compared head-to-head to the AR50.
ALSO, look real hard at the buttpad on the MRADELR - and compare it to the Pachmahr 1.20" thick "XLT Ultra Soft Magnum Trap pad (
https://www.lymanproducts.com/brands/pachmayr/recoil-pads/trap-pads/xlt-ultra-soft-magnum-trap). I'd definitely change to that pad (its ground to fit by the installing smith).