Here's some vendors to check. I might not use the screws on Stalon style (very bad idea to have separate metal parts and several hundred bar (if not thousand) pressure together. Note the huge price spread.
Not in stock, for price reference:
Stalon Muzzle Break - M15x1 Max 308Stalon muzzle brake effectively reduces recoil and barrel flip from shooting the rifle.With the help of the supplie
www.shootingsportsuk.co.uk
The Blaser Dual Brake M15x1 muzzle brake reduces both recoil as muzzle flash of your rifle and also prevents muzzle lift.
www.sportsmanguncentre.co.uk
Claim to have stock:
RCC Muzzle Brake Available in various styles and threads - Suits all calibres from .22 up to .375 An effective recoil brake that dampens felt recoil by 60-90% (calibre dependant), resulting in more comfortable shooting. Made from aluminium with a durable anodized surface. Conical Available to...
www.mcavoyguns.co.uk
Vais Muzzle Brake.
www.swillingtonshootingsupplies.co.uk
Older SD thread, maybe worth contacting member Lateral:
Looking for a muzzle brake m15x1 (possibly m18x1 considered as have an adapter) in 30 cal. Can’t see it being used much but just like to have these things in the kit bag. Thanks for looking.
www.thestalkingdirectory.co.uk