Mag extension for lar15
- Thread starter Dave P
- Start date
I'm pretty sure the content was still in the context of how the mag extensions work, and allowed me to do well in my last match. We don't get much positive NEA talk around here either, and I thought a line or two about the rifle in the photo was warranted.
Clearly not though. I'll be sure to run everything by you before I post next time.
.................... so in other news, I printed off some 30s today.
Nice! How are they attached? Are they durable? I want one.
They're attached with one 1" screw through the hole in the baseplate. There are four posts that cradle the sides of the baseplate and two other features that engage with the stamped indents to prevent/limit rotation.
Because of the locations of the posts, you have to insert the baseplate about halfway in, screw on the extender and then push the baseplate on fully.
As for durability, they're printed with PLA plastic which is pretty rigid. I did a few drop tests on my floor and the edges get rounded off but the integrity of the mag remains unchanged. As long as you're not actively trying to snap it in half, they should be durable enough.
The only issue I see with the design is that if you push the extension and magazine apart from the side opposite to the screw, there is about 1mm of play because of the baseplate flexing. I fixed this with a small piece of duct tape, but it's not really necessary to.
I'd consider selling them, ~$13 a piece is easily managable. I'm just almost out of grey PLA at the moment. If you want one in red or white, shoot me a PM
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These look pretty good, and, are an excellent use of 3D printing.
You're just using one screw though to hold them to the baseplates. How tight is the screw, and, how easily do they twist? The key is that we monopod off them, and, can be a little rough getting down on the ground. I'd hate for one of these to snap off. Have you tried stressing one to failure? Also, why type of screw did you use?
For my wooden ones, I used pretty hefty screws, that had a rather large button head on them. This made sliding the baseplate on, and getting the spring over the screw heads really tricky. It works, but, you really have to massage them on.
Edit
Ahh, wait, I see. You're only using one screw because you're attaching them partially assembed. I see.
There are low profile head type screws on the market that would be more ideal, and, with you being able to model in the pilot holes, or bosses already, could really make assembly easy. The catch is you have to put extra holes in the baseplate.
http://www.mcmaster.com/#cadinlnord/94090a100/=n6datq
Not ideal, but, I'd think these would make it ideal for having the baseplate already instealled to the extender. Then you wouldn't need the side tabs for keeping is square, as, you could just use two screws.
You're just using one screw though to hold them to the baseplates. How tight is the screw, and, how easily do they twist? The key is that we monopod off them, and, can be a little rough getting down on the ground. I'd hate for one of these to snap off. Have you tried stressing one to failure? Also, why type of screw did you use?
For my wooden ones, I used pretty hefty screws, that had a rather large button head on them. This made sliding the baseplate on, and getting the spring over the screw heads really tricky. It works, but, you really have to massage them on.
Edit
Ahh, wait, I see. You're only using one screw because you're attaching them partially assembed. I see.
There are low profile head type screws on the market that would be more ideal, and, with you being able to model in the pilot holes, or bosses already, could really make assembly easy. The catch is you have to put extra holes in the baseplate.
http://www.mcmaster.com/#cadinlnord/94090a100/=n6datq
Not ideal, but, I'd think these would make it ideal for having the baseplate already instealled to the extender. Then you wouldn't need the side tabs for keeping is square, as, you could just use two screws.
Clamping anything to the floor plate is flimsy at best. The floorplate needs to be replaced or the body needs to also be clamped. The nicest solution I've seen so far is the metal wedge coupler with a cover (boot) protecting the bottom mag from getting full of mud. These are rock solid. Plus, they allow you to carry 60 rounds in the same footprint as three 30 round mags.
Get three of these and make a removable boot to protect the bottom mag:
You have tons of time in SR to do mag changes, so there is no issue switching the boot cover between mags.
Edit: apparently Tapco makes magazine covers.
Get three of these and make a removable boot to protect the bottom mag:
You have tons of time in SR to do mag changes, so there is no issue switching the boot cover between mags.
Edit: apparently Tapco makes magazine covers.
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High Caliber Services sells the mags/coupler/boot as a combo:
http://www.hical.ca/apps/webstore/products/show/3060752#
http://www.hical.ca/apps/webstore/products/show/3060752#
Bolivar
CGN Ultra frequent flyer
Hmmmm, I like that idea. So the boots do a good job of protecting the bottom feed lips?
Hical also sells the boots ($2.50) and the couplers ($18.00) separately for those of us who all ready have a stack of LARs. I'm debating whether to spend the coin to go to a more compact package for my mags instead of having 6 extended LARs.
Hical also sells the boots ($2.50) and the couplers ($18.00) separately for those of us who all ready have a stack of LARs. I'm debating whether to spend the coin to go to a more compact package for my mags instead of having 6 extended LARs.
If you don't think the rubber boots give enough protection, you could always do what the shooter who showed me this did and cut down a mag loader to create a hard plastic one.
Wolverine sell the couplers for $9.99 each.
Wolverine sell the couplers for $9.99 each.
Bolivar
CGN Ultra frequent flyer
I might go that route. Their site does not say for sure if they are metal though and neither does their CGN forum. I sent an email to confirm. It is tempting to switch, especially it it can get rid of the slight wobble I have right now with my extenders. I think I want to go metal though, with the set screw to make sure they are rock solid. No point in spending coin to get the same slight wobble I have now.
I'm using 6x1 wood/metal screws, hand tight. I could've used longer screws, but it would be unnecessary. The PLA is a pretty solid anchor material, and up-down pulling forces that would pull the screw from the extension would probably also be strong enough to bend the floorplate off of the magazine. The only type of motion that the extension is really susceptible to is yaw at the plane where the extension attaches. The only real-world situation where that would occur to a great degree is sticking the bottom of the mag into the ground and trying to spin your rifle around it. The screws are pretty low profile but you still have to get the spring to pop over them.
Well I'm not sure what would be considered flimsy for a magazine extension, I guess it depends on the competition/conditions you need it for. I'd like to test the extension to failure, but I don't really have any idea what is involved in the matches you shoot.
The only things I could think of were stressing the joint by placing weight on the magazine and extension.
530 rounds of 5.56 ~7kg
Full 27kg case of 7.62x39 "monopoding?" if I used that correctly ...
If you have any other ideas for tests, let me know.
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Runningfool
CGN Ultra frequent flyer
- Location
- SW Ontario
Great stress tests. Nicely played! 
Strength and rigidity are two different things. Since we want to use the extension as a monopod in SR, we don't want there to be any play or bending between the magazine and the extension, none at all. We want them to feel solid, like a 30 round magazine would.
Looking at the pics above, it appears that there is some bending at the interface point. If you flipped it to the other side, it would probably bend in the other direction. We cannot have that. It would be wobbly. The extensions Bolivar showed me wobble. The magazines with the metal couplers that I have been shown do not.
Looking at the pics above, it appears that there is some bending at the interface point. If you flipped it to the other side, it would probably bend in the other direction. We cannot have that. It would be wobbly. The extensions Bolivar showed me wobble. The magazines with the metal couplers that I have been shown do not.
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I have tried using the floor plate to mount extension using 2 screws,it is strong enough for normal use but it flexes too much to use as a monopod. Probably the ideal solution would be the metal couplers with a plastic extension attatched to simulate dimension of 30 rnd mag
If you have any other ideas for tests, let me know.
Simple test: If you do this, or apply any kind of lateral force, and there is any bending (i.e. the magazine and the extension don't stay parallel) it will not work well for our intended use.
It's going to be hard to compete with couplers for SR, even if you can make the extension as rigid. The couplers allow you to cut the the number of mags you need to carry in half. It's even better than Beowulf mags in that regard. Unlike 3-gun, etc... there is no need for a fast magazine change, so having to flip the mag around and remove the cover isn't an issue.
