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Discussion Starter · #1 ·


Howdy fellers, I just wanted to show off my new magazine extension I've been working on and finally got done. I redesigned it to match the curves and contours of the pistol grip a little bit better. I also printed it at about a 45° angle which gives it much better strength than before. This allowed me to go thinner on the top portion where the magazine versus building it up around the sides as I had done previously. I also created a slot in the bottom so that the follower will protrude out like the factory magazine when fully loaded. This had the side effect of essentially gaining another round in capacity, so it went from +5 to +6. The hardest thing was coming up with a redesign for how the magazine locks to the extension. The previous method with the tab-in-slot design worked well enough but I was never really satisfied. I had wanted to avoid using any hardware but I finally decided that the best way was a bolt holding in a block. I think it's much more secure at the cost of require something I couldn't just print, which is fine. I think it's a better looking and more intuitive solution. Now if I could only get me some of those flatwire springs Keltec is putting in their new mags (or just some new mags) I'd be sitting pretty.

Live fire demo here
 

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Howdy fellers, I just wanted to show off my new magazine extension I've been working on and finally got done. I redesigned it to match the curves and contours of the pistol grip a little bit better. I also printed it at about a 45° angle which gives it much better strength than before. This allowed me to go thinner on the top portion where the magazine versus building it up around the sides as I had done previously. I also created a slot in the bottom so that the follower will protrude out like the factory magazine when fully loaded. This had the side effect of essentially gaining another round in capacity, so it went from +5 to +6. The hardest thing was coming up with a redesign for how the magazine locks to the extension. The previous method with the tab-in-slot design worked well enough but I was never really satisfied. I had wanted to avoid using any hardware but I finally decided that the best way was a bolt holding in a block. I think it's much more secure at the cost of require something I couldn't just print, which is fine. I think it's a better looking and more intuitive solution. Now if I could only get me some of those flatwire springs Keltec is putting in their new mags (or just some new mags) I'd be sitting pretty.

Live fire demo here
Cool, and even cooler video. I'll take two or three.
 

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I got all 7 of the new extensions in this week. Shipping was quick and everything came in good order.

There ended up being a few more artifacts than the earlier version but nothing a few minutes, a thumbnail and a lighter couldn't take care of. Just part of the game with 3d printed parts. I'm super picky, to be fair.

My first mag was a complete ****show. I obviously wasn't holding my tongue right and the spring plate kept getting cocked and the spring kept getting bound up. I had to remove the extension multiple times, while trying not to break anything. The spring took some odd bends each time but were easily corrected. I finally got it to go and the rest went easy as pie, the first time. I did adjust my technique with the wrench and found the method that worked best and closely matched the instructions. Without a visual, you could use the wrench incorrectly, in a number of ways.

Once I nailed the wrench technique, they all went on fast, the first time. I did the last 6 in half the time of the first one. One other tip is once you slide the extension back and remove the wrench, if the spring plate doesn't seat on the extension by itself, give the mag a good firm tap on a hard surface and it should pop into place.

The locking piece is interesting and a good solution. They all fit very well, with close tolerances. The screws are of good quality and all but one had very similar resistance, while installing, and locked in flush. One was noticeably looser than the rest, but it still locked in with enough tension that I'm not worried about it. Hole diameter can get tricky with 3d prints, so that's not surprising and the tolerance shift is actually ridiculously small. I think this will be plenty to keep the extensions locked onto the mags.

The included wrenches worked ok but both ball ends rounded easily and made it near impossible to turn the screws, even when not turning from an angle. The short end remained useable throughout, so I expect possibly an uneven heat treat or perhaps undersized machining. Neither side fit the fasteners as tight as I would like but that's super common with generic wrenches and really no fault of the seller.

My one regret is that I was too stupid to realize I was standing right next to a full set of long shank t-handle allen wrenches, the whole time. I wised up on the last mag. That would have made the slowest part much faster.

The new design is pretty cool, well thought out and quite strong. I like it quite a bit, off the gun. In the gun, I'm not sure which version I like better. The new one is more streamlined, likely stronger and will probably work better, ergonomically, than the earlier version. The older version seems to fit the design a bit better, but the new one fits the profile better, if that makes any sense. The only design improvement I can think of would be to remove the side indents, and incorporate some "keltec grip blocks", to match the grip. That's purely cosmetic and subjective.

In the end, the new version holds more ammo, so that's a first place finish, regardless of the cosmetic differences. I would gladly buy again and would highly recommend to anyone looking to hicap their hicap.
 

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Discussion Starter · #11 ·
All good observations HoldenMcGroyne. I probably need to come up with a more clear set of instructions for installation. Those artifacts you mentioned had been kind of intermittent with some prints, but I changed my bowden tube setup just last week which appears to have eliminated them altogether. Installation seems to be on the tricky side, I probably need to include some better instructions or maybe even a second tool of some kind beyond just the wrench. The wrench method works, but like you said you've got to get it just right on the release when you slide it out. As far as tolerance with the screw resistance, at this point I expect more variation with my hardware than I do my prints, I feel like my print tolerance is pretty consistent. Obviously the hardware I can't make myself so I'm at the mercy of that manufacturer's QC. All this is good feedback for improvement. Sounds like I need to reassess my wrenches/screws.

Be sure to follow up with some range reports when you get a chance to do some shooting!
 

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I got all 7 of the new extensions in this week. Shipping was quick and everything came in good order.

There ended up being a few more artifacts than the earlier version but nothing a few minutes, a thumbnail and a lighter couldn't take care of. Just part of the game with 3d printed parts. I'm super picky, to be fair.

My first mag was a complete ****show. I obviously wasn't holding my tongue right and the spring plate kept getting cocked and the spring kept getting bound up. I had to remove the extension multiple times, while trying not to break anything. The spring took some odd bends each time but were easily corrected. I finally got it to go and the rest went easy as pie, the first time. I did adjust my technique with the wrench and found the method that worked best and closely matched the instructions. Without a visual, you could use the wrench incorrectly, in a number of ways.

Once I nailed the wrench technique, they all went on fast, the first time. I did the last 6 in half the time of the first one. One other tip is once you slide the extension back and remove the wrench, if the spring plate doesn't seat on the extension by itself, give the mag a good firm tap on a hard surface and it should pop into place.

The locking piece is interesting and a good solution. They all fit very well, with close tolerances. The screws are of good quality and all but one had very similar resistance, while installing, and locked in flush. One was noticeably looser than the rest, but it still locked in with enough tension that I'm not worried about it. Hole diameter can get tricky with 3d prints, so that's not surprising and the tolerance shift is actually ridiculously small. I think this will be plenty to keep the extensions locked onto the mags.

The included wrenches worked ok but both ball ends rounded easily and made it near impossible to turn the screws, even when not turning from an angle. The short end remained useable throughout, so I expect possibly an uneven heat treat or perhaps undersized machining. Neither side fit the fasteners as tight as I would like but that's super common with generic wrenches and really no fault of the seller.

My one regret is that I was too stupid to realize I was standing right next to a full set of long shank t-handle allen wrenches, the whole time. I wised up on the last mag. That would have made the slowest part much faster.

The new design is pretty cool, well thought out and quite strong. I like it quite a bit, off the gun. In the gun, I'm not sure which version I like better. The new one is more streamlined, likely stronger and will probably work better, ergonomically, than the earlier version. The older version seems to fit the design a bit better, but the new one fits the profile better, if that makes any sense. The only design improvement I can think of would be to remove the side indents, and incorporate some "keltec grip blocks", to match the grip. That's purely cosmetic and subjective.

In the end, the new version holds more ammo, so that's a first place finish, regardless of the cosmetic differences. I would gladly buy again and would highly recommend to anyone looking to hicap their hicap.
What is this wrench technique?
 

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Discussion Starter · #15 ·
What is this wrench technique?
Use the long end of the hex wrench to hold the spring and floor plate flush with the magazine body. Then you can slide the extension on about 3/4 of the way. Slide out the hex wrench from the side and push the extension the rest of the way on until you hear the 'pop' of the floor plate seating into the extension. It's really easy just kind of convoluted to explain. I've been meaning to make a video on installation like I had for the previous version but I've just not had the time to sit down and do it.
 

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Gotcha. Thought/hoped it might be a disassembly technique once the extension was installed. That is what I need. LOL
 
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