[b789]

I can thoroughly recommend both the SSG Mini-extreme and the APA “Little Bastard”
Get your smith to thread the barrel, time the brake and your gtg.

[b789]

The HSS kit is excellent!

The Lumley Arms kit is “more” excellent.

Good choice nevertheless. You'll have no problems with the HSS.

[b789]

I forgot to mention the 1 inch Limbsaver fitted to the Helmic arms Tactical Thumbhole stock also played a substantial part in reducing the felt recoil of the 300WM!

[b789]

Hopefully I can make a meaningful contribution!

I have the T3 Super Varmint in  300WM. Early on I disposed of the light plastic stock in favor of a sturdy laminated stock from Chad Helmic- the Tactical Thumbhole.
The extra weight of the stock has significantly reduced the “felt” recoil.
Secondly, I had a local gunsmith here near home thread a Surefire Muzzle brake on for me. I don't recall the serial number. In any case they have a new series out now.
The combination of the heavier stock and the MB now has the 300Wm behaving like a “kitten”!! I could shoot it all day ( not that I do!) without any fatigue or sore shoulder.
You and your near shooting partners absolutely require  First Class hearing protection as it now has a very loud report and substantial concussive wave either side of the shooter.

As a gunsmith is not available to you I'd refer you to Jason's recommendation for the clamp on MB.
I'd also recommend a new stock from the performance centre. Preferably not a light “Tube” stock as I don't believe you will have any discernible recoil reduction benefit. I can recommend Chad's stocks.
The GRS isn't quite as heavy however my GRS is going on a 7mm08, so the increase in weight isn't as important with the smaller caliber.
I really do enjoy shooting my T3 after the mods.
I hope this may have helped.
Good luck!