What are the reasons for the interchangeable comps on the 4" 500? One is supposed to be for cast and the other for jacketed? Why? Will something blow up if you use the jacketed one for lead? Better performance?

I bought a 4" 500 used. The previous owner told me that the lead comp is the longer one of the two. Is this correct? I wasn't able to find an owners manual online.

Thanks!

Your second question answered your first
Yes-long is for cast

To prevent leading from locking the comp in place when using jacketed comp. The top ports go through the shroud and comp which if leadin occurs makes it diffucult to remove.

No

No- some report less muzzle flip with jacketed comp compared to lead comp.

I personally have not had any problems with using either comp with either type bullet but should note I only used correctly sized cast bullets and 90% of those are gas checked.

So I presume that this .501 bullet is properly sized and I will be fine with either?

440 Grain Wide Flat Nose Gas Check (.501) [501-440-WFN-GC] - $20.00 : Matts Bullets

Thanks for all the help!