Sig P220 9mm/45 Conversion Questions Answered

[SIG_Fiend]

Please bear with me as I do not yet have all the components, so this thread is a work in progress. First off I'll start by stating my intention. I'd like to help clear up some of the speculation, misconceptions, etc regarding differences in the P220 9mm and .45, and converting to either caliber on either frame. I have a older non-rail frame P220 .45., serial G 275 XXX, so it's a 220-1 and I believe the serial number puts the manufacture somewhere around '96-98 (correct me if I'm wrong).

My intention is to build an "American" P220 9mm using the necessary components from a Euro 9mm in my .45 frame. Why you ask? Because an American P220m 9mm with button mag release is an itch that P226's and P225's just can't seem to scratch for me. What can I say, I like obscure stuff and doing things the hard way. I also plan on swapping the left over .45 parts into the Euro 9mm just for the heck of it, and because I've seen mention of a few others that wanted to do that conversion to their Euro 9mm's.

 

[SIG_Fiend]

Well here's the first little tidbit I've learned. I recently received a Sig factory American P220 9mm mag. First off, the mag tube exterior dimensions are literally almost completely IDENTICAL between it and the .45 factory Mecgar mags. There are very minute differences, which I'd attribute to differences in manufacturing practices over the years. The mags I measured were a Sig factory 7rd .45 mag (flat baseplate), factory 8rd mag (plastic baseplate), and factory 10rd mag (plastic baseplate). All mags were Sig OEM, produced by Mecgar. Here's a pic of the mags:

The dimensions are as follows:

9mm:

-Width = ~13.85mm
-Length (front to back) = ~34.80mm
-Height = ~120.4mm

45acp:

-Width = ~13.85mm
-Length = ~34.8-34.95mm (variance between the 3 different Mecgar mags)
-Height (7rd mag) = ~121.5mm

Just fyi, the 220 9mm American mag fits my .45 frame perfectly, mag button locks in place properly, mag releases properly, nothing is overly stiff, not tough to insert or remove. It's almost identical to the .45 mag, just minor differences in the shape of the upper feed area. So the 9mm mags do in fact fit the .45 frame, .45 mag release functions properly and smoothly, etc etc. In fact, the mag actually activates the .45 slide lock, however once I get the gun up and running in 9mm we'll see if that actually works or not. We'll also see in the not too distant future if the thing actually feeds

 

[SIG_Fiend]

One other little tidbit. Up front I should say this is a work in progress, as doing this mod to the mag prevents it from fully inserting and locking in place. Sounds dumb, I know, but I'll see if there is a simple way around that as it's only a millimeter or so keeping the mag from fully seating and engaging the mag release properly. Just thought I would throw it out there though as I was trying to mix and match parts to see what's possible.

The 220 9mm mag has the old style baseplate securing method of the spring "leg" sticking through the "dovetail". What I found is that, if you take a pair of pliers, you can bend this bottom coil inwards a bit so that it doesn't stick out quite as much. After doing that, you can use the plastic 8rd .45 basepad with it's correct metal locking plate. With the spring bent properly, it will sit flat at the bottom of the plastic baseplate. Doing this gives you +1 round, so the mag now holds 10rds. With 10rds in there, the mag is fully compressed. Here's the downside though. For some reason I cannot get the darn mag to fully seat and lock in place with the plastic basepad. It appears to be only 1-2mm or so from fully seating and locking in place. It's VERY close, so I'm going to see if I can do some tweaking, to anything EXCEPT for the gun, to get this thing to fully seat. A 10rd single stack 9mm P220 would be nice. The only reason I can think of for this issue is that the 9mm mag release holes are either slightly off or maybe the lower mag "lip" for the baseplate is slightly different from the .45 mags. I'll get more in depth on this later as it would be neat to make it work.

 

[Texas Armadillo]

Thanx for the progress reports. Interesting little project you gave yourself. Question, how similar is this to what Para recently did on SigForum? He made a 9mm P220, but I think he used a American made 9mm slide and a P225 9mm barrel. I just skimmed his project and was just wandering if you had also.

 

[SIG_Fiend]

Oh, I've definitely seen his thread. It's the thing that got me started on wanting to build a P220 9mm. I decided the ultimate Sig for me would be a P220 9mm "tactical" (like the 226 tactical, w/ threaded barrel so I could suppress it). I've owned a P225, shot plenty of P226's, and while I like each of those guns, I really prefer the feel of the P220 frame as it's just right for my hands. The conversion I'm working towards is somewhat similar in principle to what Parabellum did, however he used a rare prototype 220 Stainless slide that has a breech face compatible with 9mm and an external extractor. His gun is quite a bit nicer considering mine will be made out of lowly carbon steel as opposed to stainless. I don't care about mine looking pretty and will probably never get the gun refinished as I plan on using it as a beater all purpose range gun.

Actually, he's using a P226 9mm barrel in his gun. P225 barrels are too small to work. There are a handful of others using stock P226 9mm barrels in their 9mm or .38 Super converted to 9mm P220's. It has been found that the P226 9mm barrel is literally identical to the P220 9mm barrel, locking lugs, barrel hood, etc are all identical. Sweet thing about that is that means once you've done the 9mm conversion, you can just swap in a 226 tactical barrel without any mods and you're good to go. Plug and play is always cool in my book.

From what I understand, the basics necessary for the conversion in the .45 frame include using the 9mm locking insert, 9mm slide catch, 9mm breech block, and P226 barrel. As far as the slide goes, technically since I have the older folded slide P220 with removable breech block, I should be able to just swap in the 9mm breech block (with internals of course) and then the slide is good to go. I'm sure then you'd need some new sights but, that's no biggie. The thing is, I priced out the components for the 9mm breech block, firing pin components, 9mm locking insert, P226 barrel from Numrich and all the parts would still total out to around $400-500. It's got to be nearly impossible to find a 9mm breech block or locking insert for sale elsewhere. So I've decided I'm simply going to buy a Euro 9mm for roughly the same price as it's easier, I get one extra mag out of the deal. Plus, the nice thing is I should technically be able to swap the 9mm locking insert and slide catch into my .45 frame, then just simply put the complete 9mm slide/barrel assembly on my .45 frame and I'm good to go, no new sights or anything. We'll see if it works out quite that easily.

 

[SIG_Fiend]

Here's a bit more about the mag. The only real internal difference in the P220 9mm mag and .45 mags is that the 9mm mag has a convex shaped metal plate welded to the rear section of the mag. This plate is there to account for the difference in length between 9mm and .45acp of course.

Here's a comparison pic between a disassembled .45 8rd factory Mecgar mag and the 9mm mag:

The 9mm mag spring is noticeably thinner, skinnier, and a bit longer in length. The follower is metal and similar to the old original 7rd .45 mag style follower, however it is shorter due to the convex plate at the back of the mag.

 

[SIG_Fiend]

Just a quick update. I re-measured the 7rd .45 mag and 9mm mag and I was a bit off on my height measurement. I'm using calibrated digital calipers but, due to the mag shape it's a bit tough to be 100% exact. The 9mm mag is roughly ~120.3-120.4mm in height from the base to the top of the rear section of the feed lips. The 8rd .45 mag is approximately ~121.4-121.6mm in height, so there is in fact a very small difference in overall height. I also noted that the mag catch holes on the 9mm mag appear to be approximately 1-1.5mm lower than the location on the .45 mag. These two differences should account for the reason I cannot get the 9mm mag to seat properly with the 8rd +1 plastic baseplate fitted. It looks like the only option now is to either modify the mag or the base of the frame itself, so it looks like sticking with the stock baseplate is the best idea for most people.

As for installing the plastic +1 baseplate on the 9mm mag, here's some pics to help you better visualize:

Here is the spring in stock form, showing the approximate angle it is bent at to properly engage the baseplate in the dovetail:

This next pic shows the bottom coil bent inward enough to clear the plastic baseplate and properly sit at the bottom:

Don't worry, it's just a small bend and can easily be pulled back out if you want to switch back, so no biggie. Here's a pic showing the completed product:

I've decided against modifying the plastic baseplate itself. There is too little material there, and to dremel any off I'd be afraid of compromising durability. No one wants there bullets falling out the bottom of their mags under any circumstances, at least no one I know. I'm going to stick with the stock baseplate for now as it works just fine. Once I get the gun up and running, I may toy with the idea of having the base of the frame machined down ~2mm so that it will work. Probably not but, I can't ever manage to leave anything stock! Computers, cars, guns, doesn't matter I always have to modify stuff. If I run out of mods to do, maybe I'll do that one. For now, one round isn't worth it. Geez, I could sure save myself a lot of time, money and trouble just buying a P6 couldn't I?! Been there, done that though, I want something different now.

 

[SIG_Fiend]

Well, to celebrate the SCOTUS ruling on Heller, a few hours ago I just picked up a euro P220 9mm on Gunbroker. Expect some updates on some of this comparison/conversion info over the next week or two. I'm sure there is all of 1 or 2 people here even remotely interested in this of course.

 

[U235]

I'll follow the thread. Good luck Travis.

 

[cowlickkid]

How's this project going? I registered at this site just to post here that I am really interested in this project and its outcome.