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The quest to make the Masterpiece Arms MPA30 suck less continues!
A week or so ago I added a side-folding tailhook brace and some accessories to my MPA30 - see previous topic here: https://www.northwestfirearms.com/t...ding-tailhook-brace-mod-overview-pics.390786/.
After finishing that project I found that the folded MPA30 with magazine is basically a giant square - 13-5/8" long by 13" tall, including the RMR clone I have on their as a placeholder and the muzzle device. While significantly shorter in length than an AR pistol, it is also much taller. It would fit in the 5.11 Select Carry sling pack, but not a more nondescript bag like a Vertx Commuter or Transit. Even angling it in the bag so it rests on the muzzle and mag baseplate, it measures 14" muzzle to baseplate by 12-1/2" from the bottom of the bag to the tip of the folded brace (shown here in a Vertx Commuter for reference).
While I could easily use this as an excuse to go out and buy another bag (and I probably will anyway, because "reasons"), having a slightly shorter magazine would enable me to use the slew of bags and backpacks I already own instead. It would also make the weapon easier to draw from the bag, because that giant 30-rounder can get caught on things pretty easily.
They make no 20-round mags for this platform that are short enough for this purpose. There are 20-round Sten mags out there, but they all are just 30-rounders with guides on the inside of the mag body that limit them to 20 rounds in single stack formation. And they also do make 10-round mags, but if I was going to do that I might as well go live in California - nobody needs that kind of negativity in their life.
I thought I'd have to resign myself to using the 5.11 or buy a new larger bag (the Vertx Dead Letter would probably accommodate it with the full-sized magazine), but when looking at the sides of the mag I realized that the horizontal ridges are the same thickness as the lip that the magazine baseplate hooks on to, and the thickness of the magazine is pretty consistent from the groove the baseplate sits in to the ridges higher up on the mag.
A solution had presented itself, so I broke out some tools and took a stab at a magazine modification. Here's the walkthrough from start-to-finish - it's an easy mod for a newbie, and takes no more than 30 minutes to complete.
Required tools for this mod are:
- Hacksaw (metal-cutting blade recommended)
- Sandpaper (for cleaning up your cuts)
- Wire cutters (good ones - the magazine spring is pretty tough)
First I wanted to figure out where I should cut the mag. I decided that leaving 3 ridges below the base of the pistol grip (cutting between the "I" and the "E" on the "MasterPiece Arms" branding) would give me a short enough length to work well in a bag or backpack, but long enough to still hold a decent number of rounds and be able to manually strip the mag out with my support hand if needed.
Once that was decided, I broke out a hacksaw and went to work. To keep a clean line I used some duct tape to protect the ridge and carefully cut as close to it as I could. Once finished, I then cut grooves above the ridge to allow the baseplate to slide through. Here it is with the cuts completed, and no polishing:
I intentionally didn't use a dremel on this project because I wanted more control of the cuts and didn't want to risk going too deep or not straight enough. Instead I chose a hacksaw with a metal-cutting blade for its finer tooth pattern, and rotated the mag after getting each corner started instead of trying to cut all the way through. Doing this enabled me to slowly start a line between each corner and connect them bit by bit with a reasonable degree of precision. Not super clean, but it definitely worked well enough for my purposes.
I dropped the baseplate on there for a test fit, and it was perfectly snug. I was a little concerned that the lips of the baseplate would not have enough "meat" from the magazine to grab onto, but those concerns proved to be groundless - the baseplate lips slide straight into the grooves I cut above the ridge and grip it tightly with no play or wobble. Here's what the cut version looks like in comparison to the full length mag:
Next I had to chop the magazine spring, which was easy enough - I disassembled a second magazine, measured how far the mag came out the bottom when not under tension, and cut at the same approximate spot on the spring for the shorter mag.
I tested the spring function and was able to load 20 rounds in its present configuration, which is exactly what I was aiming for. I tried loading more, but there was too much spring tension. Maybe with a mag loader I could get more in there, but 20 works for my purposes. I probably could remove another link or two if needed because it is really tight from 12 rounds onward, but will confirm with test firing that it works properly before modifying further. Here's the end result in a side-by-side comparison:
With a final height of ~9.5" with micro red dot, it will definitely fit in a more discreet rapid-deployment bag now. In fact, the overall length of the MPA30 with 20-round mag is shorter than a normal 30-round mag by itself.
That's all there is to it. Hope you MPA owners out there find this useful - this mod is very easy to do, and I think it makes the MPA a much more useful firearm in the "truck gun" role. Will reply on this thread and let y'all know how the mag works next time I get a chance to take it out to the range. Feel free to ping me if you have any questions, or need more pics from the process!
A week or so ago I added a side-folding tailhook brace and some accessories to my MPA30 - see previous topic here: https://www.northwestfirearms.com/t...ding-tailhook-brace-mod-overview-pics.390786/.
After finishing that project I found that the folded MPA30 with magazine is basically a giant square - 13-5/8" long by 13" tall, including the RMR clone I have on their as a placeholder and the muzzle device. While significantly shorter in length than an AR pistol, it is also much taller. It would fit in the 5.11 Select Carry sling pack, but not a more nondescript bag like a Vertx Commuter or Transit. Even angling it in the bag so it rests on the muzzle and mag baseplate, it measures 14" muzzle to baseplate by 12-1/2" from the bottom of the bag to the tip of the folded brace (shown here in a Vertx Commuter for reference).
While I could easily use this as an excuse to go out and buy another bag (and I probably will anyway, because "reasons"), having a slightly shorter magazine would enable me to use the slew of bags and backpacks I already own instead. It would also make the weapon easier to draw from the bag, because that giant 30-rounder can get caught on things pretty easily.
They make no 20-round mags for this platform that are short enough for this purpose. There are 20-round Sten mags out there, but they all are just 30-rounders with guides on the inside of the mag body that limit them to 20 rounds in single stack formation. And they also do make 10-round mags, but if I was going to do that I might as well go live in California - nobody needs that kind of negativity in their life.
I thought I'd have to resign myself to using the 5.11 or buy a new larger bag (the Vertx Dead Letter would probably accommodate it with the full-sized magazine), but when looking at the sides of the mag I realized that the horizontal ridges are the same thickness as the lip that the magazine baseplate hooks on to, and the thickness of the magazine is pretty consistent from the groove the baseplate sits in to the ridges higher up on the mag.
A solution had presented itself, so I broke out some tools and took a stab at a magazine modification. Here's the walkthrough from start-to-finish - it's an easy mod for a newbie, and takes no more than 30 minutes to complete.
Required tools for this mod are:
- Hacksaw (metal-cutting blade recommended)
- Sandpaper (for cleaning up your cuts)
- Wire cutters (good ones - the magazine spring is pretty tough)
First I wanted to figure out where I should cut the mag. I decided that leaving 3 ridges below the base of the pistol grip (cutting between the "I" and the "E" on the "MasterPiece Arms" branding) would give me a short enough length to work well in a bag or backpack, but long enough to still hold a decent number of rounds and be able to manually strip the mag out with my support hand if needed.
Once that was decided, I broke out a hacksaw and went to work. To keep a clean line I used some duct tape to protect the ridge and carefully cut as close to it as I could. Once finished, I then cut grooves above the ridge to allow the baseplate to slide through. Here it is with the cuts completed, and no polishing:
I intentionally didn't use a dremel on this project because I wanted more control of the cuts and didn't want to risk going too deep or not straight enough. Instead I chose a hacksaw with a metal-cutting blade for its finer tooth pattern, and rotated the mag after getting each corner started instead of trying to cut all the way through. Doing this enabled me to slowly start a line between each corner and connect them bit by bit with a reasonable degree of precision. Not super clean, but it definitely worked well enough for my purposes.
I dropped the baseplate on there for a test fit, and it was perfectly snug. I was a little concerned that the lips of the baseplate would not have enough "meat" from the magazine to grab onto, but those concerns proved to be groundless - the baseplate lips slide straight into the grooves I cut above the ridge and grip it tightly with no play or wobble. Here's what the cut version looks like in comparison to the full length mag:
Next I had to chop the magazine spring, which was easy enough - I disassembled a second magazine, measured how far the mag came out the bottom when not under tension, and cut at the same approximate spot on the spring for the shorter mag.
I tested the spring function and was able to load 20 rounds in its present configuration, which is exactly what I was aiming for. I tried loading more, but there was too much spring tension. Maybe with a mag loader I could get more in there, but 20 works for my purposes. I probably could remove another link or two if needed because it is really tight from 12 rounds onward, but will confirm with test firing that it works properly before modifying further. Here's the end result in a side-by-side comparison:
With a final height of ~9.5" with micro red dot, it will definitely fit in a more discreet rapid-deployment bag now. In fact, the overall length of the MPA30 with 20-round mag is shorter than a normal 30-round mag by itself.
That's all there is to it. Hope you MPA owners out there find this useful - this mod is very easy to do, and I think it makes the MPA a much more useful firearm in the "truck gun" role. Will reply on this thread and let y'all know how the mag works next time I get a chance to take it out to the range. Feel free to ping me if you have any questions, or need more pics from the process!
