Prototype of +1 Magazine Extension

[Alfonse]

Here is a printed plastic prototype of a +1 round magazine extension. It allows me to get my pinky on a PM9 sized Kahr and makes the pistol 7+1.

I would love to hear thoughts on it.
https://lakelinellc.com/wp-content/uploads/2015/07/Mag-Extension-Resized.jpg

Here is another shot of it:

https://lakelinellc.com/wp-content/uploads/2015/07/Mag-Extension-on-PM9.jpg

[Dreams_of_Steel]

Looks great Alfonse! Will those base plates be interchangeable with the stock ones?

[Alfonse]

Looks great Alfonse! Will those base plates be interchangeable with the stock ones?

The real ones will look much better, but printed plastic parts are fantastic for testing and checking fits on things. You just take off the stock base plate and retainer. Compress the spring. Slide the new base plate over the bottom of the mag and insert the retaining screw with a 5/64" allen wrench. Removal is simple too. Remove the retaining screw and slide it off being careful to keep the spring from flying out and hitting something you don't want it to hit.

It fits 6 or more round 9mm magazines.

That photo is one of my test PM9s and has a grip sleeve on it. I should have used something without the grip sleeve so the contour at the interface to the pistol was more obvious. Oh well.

I have had no problems with any of my mags with feeding. For most of the mags, extra power springs are available from Wolff, but I have seen no need in my testing.

[JohnR]

Looks good. I'd rather see something that extends the whole grip cross-section like XD extended mags do.

[b4uqzme]

Looks good. I'd rather see something that extends the whole grip cross-section like XD extended mags do.

+1 something that really finishes off the bottom of the grip would be great. But I would only want that for my primary mag. It would be too bulky for backups IMHO.

[Alfonse]

I tried that. They get pretty bulky in 9mm. On the other hand, it works pretty well on the .380s. I do have some prototype sleeves, like the XDs uses, that fill it all in on a Kahr extended mag (7 round mag in 6 CM, PM, or MK), but rigged that way it is quite a bit larger.

The other thing that happens is you would have to have a gap for a slot to get it apart since the spring drops down in the extension. It won't come apart otherwise. The gap isn't great.

[Ronni3_J]

This would be great for the 380 modles

[Alfonse]

This would be great for the 380 modles

Because of the relative sizes of everything, the 380s will probably not curve out and just match the contour of the grip on the front. They are a bit behind the 9mm though schedule wise.

[Scarywoody]

If you told me even 5 years ago that you could design and print out a prototype I wouldn't have believed it. Amazing!

[Alfonse]

In the late 90s it cost about 800 bucks and took weeks to get stereo lithography prototypes. Now, I just send a file off over the internet and the part shows up in a few days. Most parts I would get change back from a fifty.

[JohnR]

What program do you use for the design?

[Alfonse]

Solidworks.

[JohnR]

I'd like a mag sleeve for the 8 round mag to fit in the CM9, so I won't have to but a CT9. :D

[Alfonse]

A sleeve would be easy. I don't know how many would sell though. I would design part that could be 3d printed though.

If a few folks want that, I would post it to Kahrtalk and maybe the mods could make it a sticky post. Anybody who wanted one could download the file and have a company print them a part. A printed part would be plenty strong.

Let me know. I would just need to borrow or buy an 8 round mag.

[JohnR]

I'm in!

[Alfonse]

If you have an 8 round magazine I could borrow to measure from, that would sure help. I don't want to guess and assume it is just the same incremental amount added to the 6 round to get 7 rounds. PM me if you want to do that. If you are happy with me just taking an educated guess, I can do that too.

[JohnR]

If I send measurements, how precise do you need them?

[Alfonse]

If I send measurements, how precise do you need them?

That is a better idea. The only measurement I need would be from a good reference point, like the flat on the bottom of the mag catch hole to the base of the magazine "rails" that slide into the slots of the base plate. I have everything else. Using calipers would be just fine, within a couple thousandths of an inch would be best.

The next question is whether you want it to extend the back strap of the pistol, or be like the factory sleeves and only be flush along the front?

[JohnR]

I don't have precise calipers, but the catch hole to end of magazine looks to be exactly 2 3/4".

I would propose a sleeve that continues the grip cross-section all the way down, curving at the back strap.

http://www.kahrtalk.com/attachment.php?attachmentid=12950&stc=1http://www.kahrtalk.com/attachment.php?attachmentid=12951&stc=1

[muggsy]

The longer the grip the more difficult it is to conceal the gun. If someone wanted a 7+1 they could just buy a CT380. I just don't think that there would be much of a demand for a mag extension, but I could be wrong. I thought I was wrong once, but I was mistaken. :)

[Alfonse]

The longer the grip the more difficult it is to conceal the gun. If someone wanted a 7+1 they could just buy a CT380. I just don't think that there would be much of a demand for a mag extension, but I could be wrong. I thought I was wrong once, but I was mistaken. :)

I guess we'll see Muggsy. The extension is no bigger than the finger extensions that seem so popular and gives you an added round. They are one of the most popular accessories for the Glock 43.

JohnR isn't talking about an extension, but more of a sleeve to fit over the 8 round magazine. I am only doing a file, gratis, for that. But the file will allow anyone who uses it to go out and get printed parts to make a sleeve like he has shown.

[Alfonse]

JohnR, your sleeve is all done. I can't figure out right away how to put up the files where people can download them, so just PM me your email address and I'll send them to you. To have the sleeve continue the back strap of the pistol, a separate base plate is required. The sleeve slides down over it. It is designed to work with the original Kahr plastic retainer. Be sure to find someone to 3d print it who will do a black color and the base plate would be best with some glass fill to give it a bit more strength. Here are some photos of how it works.

https://lakelinellc.com/wp-content/uploads/2015/09/Bottom-View.jpg

https://lakelinellc.com/wp-content/uploads/2015/09/Transparent-Assembly-View.jpg

https://lakelinellc.com/wp-content/uploads/2015/09/Side-and-Top-View.jpg

[Alfonse]

I would normally print a part like that in Nylon. It is sometimes called SLS (selective laser sintering) and can be done with glass fill. The base plate fits on a shorter mag as well. You might like that base plate on a 6 round mag. It fills in some of the gap.

[muggsy]

I guess we'll see Muggsy. The extension is no bigger than the finger extensions that seem so popular and gives you an added round. They are one of the most popular accessories for the Glock 43.

JohnR isn't talking about an extension, but more of a sleeve to fit over the 8 round magazine. I am only doing a file, gratis, for that. But the file will allow anyone who uses it to go out and get printed parts to make a sleeve like he has shown.

If they function better that the seven round mags John just might have something. It's something I might consider carrying as a spare mag.

[Alfonse]

If they function better that the seven round mags John just might have something. It's something I might consider carrying as a spare mag.

The plus one extensions which will be production available soon are machined aluminum. A 6 round mag with one of them is not as long as the 7 round factory magazine and a 7 round with an extension is not as long as an 8 round magazine..

[Harrylee]

I was doing this 3 years ago trying to sell them but no interest. I made mine out of wood, the problem with 9mm is it’s such a tapered round and does not like to be single stacked and that is why people didn’t like the 8 round mags much. The more you stack the more they want to curve. But here is what I came up with, it was all a labor of love to make these sleeves and not easy to boot


http://www.kahrtalk.com/attachment.php?attachmentid=7549&stc=1&thumb=1&d=1358602001

http://www.kahrtalk.com/attachment.php?attachmentid=7550&stc=1&thumb=1&d=1358091669


http://www.kahrtalk.com/attachment.php?attachmentid=7551&stc=1&thumb=1&d=1358091684

[Alfonse]

I was doing this 3 years ago trying to sell them but no interest. I made mine out of wood, the problem with 9mm is it’s such a tapered round and does not like to be single stacked and that is why people didn’t like the 8 round mags much. The more you stack the more they want to curve. But here is what I came up with, it was all a labor of love to make these sleeves and not easy to boot

I had a design for the 7 round mags that I just made a bit longer for JohnR. It didn't take but 20 minutes or so. Printing the parts is pretty easy, you just email the files and call them with your credit card and you will have parts in a week or so. I agree that I don't expect much demand so do not want to stock anything or run these in a production fashion.

I expect our followers would help any feeding issues since they get a little more spring pressure on the front of the round.

Nice Parts though Harrylee!

[JohnR]

Alphonse, that's awesome! Thank you for your effort, I'll report on the results.