I understand the spring weight for the 45 Win Mag is 27 lb?  Anyone experimented with other options?  Does anyone know what is typically used for the 357 mag conversion (not the 357 Grizzly Mag)?  Thanks

I'm not sure of the spring weights, but the original springs had coils dyed to identify each caliber as follows.

White - 50AE
Gold - 44 Mag/45 WinMag
Purple - 357 Mag
Red - 45 ACP
Blue - 357/45 WinMag
Green - 10mm
Unknown - 9mm WinMag

However, I have seen some factory conversion kits where the springs had no color identifier on them.

Tony

Thanks.  For 357RemMag, maybe I'll try a 22lb like the Coonan or 20lb to account for the heavier slide. 

The spring for the 45WinMag I just got didn't seem as stout as I was expecting so thinking I might replace before shooting.

Another quick question, Tony (or others).  I notice the Underwood 45 Win. Mag. ammo is considerably more potent than the Winchester loadings i.e. - 1300 ft. lbs v 1000 ft. lbs. 
Is anyone aware of any issues running stronger loadings in the Grizzly?

If you run a bunch high pressure ammo through a Grizzly, you will deform the recoil spring guide so bad, the slide will bind up.
The flat part of it gets pinched between the slide and frame at full recoil and batters the hell out of it. 
Oh, and don't try one of those plastic/rubber buffers.....one shot will blow the thing into little pieces that you will be picking out of your gun for a week.

Also, the Grizzly doesn't have a fully supported chamber, so if you run the pressure up enough, you can blow out a case, destroy your magazine, and damage your grips.

I know all of the above unfortunately from personal experience.

Tony

Thanks for the response.  I am assuming that you would not shoot any amount of Underwood in the Grizzly?

I have never handled the 50AE MKV version but I'm assuming LAR must have beefed that one up even more, and not just added a heavier recoil spring.