Hello All!  Got a serious question I can’t get a straight answer to.  I have a M45 and want to beef it up for .45 super.  I’ve been researching for a few days now and have come up with mixed answers.  Some people say they changes their recoil springs, msh and the stock fps to a flat fps.  Others have said that they just use a shock buffer with heavier recoil springs.  There is a conversion out there for over $400 but it seems that it’s the same as the total spring change with the flat fps and new barrel.  I’ve also read people saying that the 1911 platform is not rated for .45 super which sounds strange because the .45 super generates less pressure than a 10mm and 10mm 1911s are everywhere.

I want to shoot .45 ACP & +P out of my M45 and be able to load .45 Super safely for occasional shooting, as a woods gun and a hunting primary/secondary (whitetail as well as hogs).  Please help me out with the proper way to set my M45 up or advise if it’s a good idea at all.

Wow!  No replies since July, I wonder why, usually folks are helpful here.

The 45 super conversion is straight forward.  I converted my Para P14 to 45 super in 3 phases.
The Para will differ from your Colt in a couple of areas.  The Para is Series 80 based so it has the firing pin safety.  I am not sure if your M45 is Series 70 or 80.  Also the Para barrel has a ramp and fully supported chamber.  The 45 Super brass is thicker than the 45 ACP toward the bottom of the case so 45 Super case does not deform due to the increased pressure.  Should be fine in your M45 but you probably want to check fired cases closely before reloading.  My fully supported chamber ensures no 45 Super case bulge.

Phase 1 - I replaced the recoil spring with a 28# Wolff recoil spring (standard is 16#).  It was the heaviest one they offered.  I could have gone with a lighter spring but I thought I would start heavy and then go lighter if needed.  I am not sure if the pistol will shoot 45 ACP with the 28# spring but it works great for the 45 Super.  I also added a shock buffer to prevent any frame battering.  I have not noticed any wear on the buffer while shooting 45 Super.  Wolff also included a heavy duty firing pin spring.  I replaced the firing pin with a titanium firing pin and reassembled with a the HD firing pin spring.  The lighter firing pin and heavier spring prevent the firing pin from traveling forward once the slide has returned to battery.  The firing pin momentum has increased due to 30# recoil spring which increases slide velocity as the slide returns to battery.  With my series 80 this shouldn't be a problem because of the firing pin safety but I did it anyway.  I fired different brands of 45 Super with different weight bullets and some of my own reloads.  I inspected the pistol closely after each range session with no problems noted.  So far the changes are easy to undo.  The HD firing pin spring will work fine with 45 ACP loads.

Phase II - I replaced the firing pin stop with an oversized firing pin stop.  I bought an EGW oversized firing pin stop and fit it to my pistol some filing and stoning was required to fit the stop.  The new stop has a square edge at the bottom, the part of the stop that contacts the hammer first as the slide recoils.  I rounded the square edge just slightly.  The idea is to slow down the slide as it moves reward under recoil.  The firing pin stop that comes with the pistol is tapered toward the bottom where it would contact the hammer.  This allows the slide to travel farther reward accelerating more during recoil.  With the square edge stop the stop contacts the hammer sooner and reduces the rearward velocity of the slide.  This is just a very small distance but the slide is accelerating more due to the 45 Super load.  This is also to prevent any battering of the frame when firing the 45 Super.  There is no need to undo this mod to fire 45 ACP unless you run into malfunctions when going back to 45 ACP.  Simple to undo if needed.  I have not had any issues in my Para.

Phase II - I haven't completed this phase yet.  Replace the hammer spring (main spring) with a heavier spring.  Wolff springs has a pack of various spring weights.  I bought the pack and intend to start with the 30# spring (standard is 23#).  I purchased a new mainspring housing, cap and pin retainer so I had a complete assembled mainspring housing that I could install for 45 Super or go back to the original 45 ACP mainspring housing easily.  The idea of the heavier mainspring is again to slow the slide during recoil.  The heavier spring will probably affect the trigger feel.  I'll start with the 30# spring if I don't like it I'll go down in spring strength until I get a trigger feel that I like.

You can currently find loaded 45 Super ammo from Underwood and Buffalo Bore from 255 grains down to 120 grains.  MidwayUSA seems to have frequent sales and free shipping on this ammo so I stock up when I can.

Good luck and enjoy.

Awesome info, thanks so much dude!  Hopefully I can get it set up soon.

I did a lot of reading about it and came to the conclusion if I want to use .45 Super it's better to grab a USP .45 or MK23 (I have the latter), whose super-durable polymer frames are much better suited to the kind of stresses .45 Super introduces. Don't want to batter my M45's frame to death. YMMV.

Just for info I fed my colt rail gun a steady diet of .45 +p HST.  No issues whatsoever.