I dont know if any of you have a cx4, much less the black sheep .45 version. I bought one with the intention to have a pistol and a carbine that uses the same mag and uses .45. I had intentions to get the 45 PX4 and use the same mags.
Naturally after I got one, the only company that makes the PX4 45 mag conversion sleeve stopped making it under the guise that they are getting the configuration right on their new 3d printer. They are a full 2 months behind their original date that they would be back in production and never answer my calls or emails about it. The name of the company is Sierra papa, they make a mess of mods for the cx4.
So now that getting the PX4 sleeve is out with no production date in sight I decided a few months ago to start looking for an alternative mag that would hold additional bullets, and preferably work without permanent modification to the lower of the CX4 that would make original mag use impossible.
I did lots of looking at different .45 mags and finally have found one that works, and works without the sleeve needed. 8)
SIG P227 14rd mags! Almost double the original capacity! :P
Here is what you have to do.
1: Remove the original mag sleeve from the lower
2: Remove the mag release spring from inside of the magwell
3: Slip the mag release out of the lower
4: Use a file and take some material off the inside of the mag release opposite the actual catch. This allows you to press the release in far enough to clear the mag with the additional width of the p227 mag vs 8045 mag.
5: This is optional depending on how deep you want to cut the new slot on the mag. Use a file and trim the mag catch down so that it doesn't stick so far to the back of the mag.
6: Depending on which side you had the mag catch, you will need to move the catch to the bottom slot in the plastic.
7: Use a file to remove a bit of material from interior of the back of the magwell. This will allow the mag to drop free once you finish the fitting of the mag catch.
8: Take the guts out of the mag as now you will mod the mag to get it positioned right.
9: File the section of the mag that is directly under the bolt catch when inserted. This will allow you to put the mag in far enough for proper feeding without having the actual mag body engage the bolt lock.
10: Using a small grinding wheel, something like you find with a dremel, you will use this to cut a new notch into the mag body. The top of this notch will need to be just more than 1/8th of an inch below the factory cut. This will be a bit far, but ensures that you don't cut it too high to start with. If you cut too high on one side, it's not a total loss, you can always move the mag catch to the other side and cut the opposite side of the mag.
11: Assemble the upper and lower and place the mag catch in the lower without the spring.
12: insert the mag and see if it catches, you will need to manually hold the catch so that it doesn't hang on the first (factory) mag catch.
13: If the magazine won't catch on the new slot, do the following. Slowly and very carefully remove just a hair at a time at the top of the new cut. Each time that you take a hair off, check and see if you can get it to catch even if it's seated really far in. Repeat this until the mag will seat and you can get it to catch.
14: Once you have the mag capable of catching, lock it in place and check that you can manually cycle the action. You may need to take additional material off of the top of the cut in the mag as it may sit too high and drag on the bolt.
15: When the action is cycling by hand without hang up, put the spring back in the mag catch, this is a bit tricky.
Try the gun out, mine runs wonderfully and now I have 14rd mags instead of 8!
If you want to go back to factory mags, simply do the following.
1: Remove the mag catch spring and pull out the mag catch.
2: Remove the metal catch plate and turn it around 180* so that the notch and trim you made to it is facing the front of the magwell when the mag catch is inserted.
3: Re-install the mag catch and spring
4: Re-install the mag sleeve
Voila, you are back to 8045 mags, if Sierra Papa ever gets off their rump and makes the sleeve for the px4 mags, then you can use them too without the mods you did above causing a problem.
Plus none of the mods that you did affected the reliability of the P227 mags which means I now have my pistol carbine .45 combo that uses the same mags. I have not tested any of the 10rnd mags to see if it fits, it might be too short.