Matt Robert's WE HPA Hi-Cap GAS MAG

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Category News & Announcements
Author AR1U5
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Creation date March 03, 2014
Views 3063
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Language English
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Keywords: Gas, WE, GBBR, HiCap, High, Cap, Mods, HPA

One of many within our community in the UK has innovatively come up with a new way to compete with the AEGs on the field. This new method is otherwise known as the Hi-Cap HPA Gas Magazine for the WE GBBR series. Here is what he had to say regarding the project:

"This started as an idea by my good friend Adam Davies, both me and Adam are big fans of gas blowback rifles between us we've owned many we's, inokatsus, G&P WOC's, vfc mp5's to name a few, now we mainly play cqb, but no matter what on cold days the gas guns did struggle especially when your trying to compete with other players using hi caps. So Adam being an old skool air softer he came up with the idea of using hpa. After some google work there were a few people kicking about that have done this and a few different designs. So we planed and sourced the parts and got to work. We had a few different mag ideas but we started with the easiest idea which was this on. A green gas we mag with a hi cap mag feeding it.

So first of we tapped a gen 1 co2 mag where the inlet valve is, this was just as a test to see if it work. We used a 1/8 bsp tap as that was the fitting on the gas line that we had. We then checked to see if it would work and to our surprise at approx 400/500 psi (set at 330 fps) it cycled lovely with a standard rate of fire. So we moved on to a green gas mag to see which would be the best to use, so we tapped a green gas mag in the side. Now we guessed that the co2 mag would need more psi, so we tried the green gas on approx 80 psi to start with and perfect. It cycled great however the rate of fire increased and is quite tasty now. So we stuck with the green gas mag as my fire base regulator only goes up to 140 psi.

Now that the mag works we went on to work out the hi cap feeding into the gas mag, so our first idea was to use a spring like the m249 box mag uses as we new it would be needing to move and bend. Also a big must which we found out rafter a few attempts is no matter how you do it the bbs need to be in single stack formation all the way to the feed lips. Otherwise they jam and you loose the required pressure to feed them fully. So I used box section aluminium and brass tube which fits inside the box section and also loosely fits the bbs inside. So I started by disassembling the gas mag and all the parts to do with the bb channel. And got rid of them as there no longer needed. I then cut a section out the mag and then cut a new section of my Ali box section. I cut the box section so it has 2 prongs that go right up to the feed lips of the mag and glued into place using liquid metal. This then allows me to remove a section of brass pipe in and out of the bottom.

Next I needed to do a similar process on the flash mag internals. So I started by cutting away everything that was in the way just leaving the mechanism, I then again cut a section of Ali box section to lip over the square hole where the bbs come out. Again this allows me to add and remove a section of the brass pipe.

Then I used a tension spring approx 70 mm long and one that fits a bb loosely inside. I cut 2 small sections of the brass barrel and twisted into each end of the spring. The spring holds these in place very securely.

Now you can do a test to see if it all fits so connect the spring to each part and that it a nice slide in fit and all is good.

My next issue was i wanted the hi cap to be in a real steel m4 mag with the inert rounds in for a better look. However the flash mag internals did not fit, so instead I used the flash mag case and modified the top of it to look like the real steal mag and then I used the internals of the RS mag and cut the bottom of them then put them inside the flash mag and checked that it fitted the inert rounds in. After I got it looking and working well I cut a section out the top of the RS mag internals so that once the inert rounds were removed you can fill up the bbs. Then I was a case of making a hole in the case for the spring to come out of. Then assemble it back up including the flash mag mechanism and spring attached and thread the spring through the hole. That's the hi cap part done.

Now I then marked the cut outs of the gas mag case to allow for the spring and the thread of the 90 degree 1/8 bsp elbow fitting. Once that was done I checked it all assembled ok and took it all apart again. Then I gave it all a coat of matt black paint just to tart it up a bit as let's face it, us airsofters love to look good. Ha ha.

One that was dry I reassembled it and attached the hpa fitting to the mag using Phyfe tape for a good air seal, and tested just the gas mag first to check again that it was gas tight and worked in the gun itself. Then the fun part! Fully assemble the 2 mags joining them together using a cheep mag clamp I bought and filled up the hi cap. And I'm sure you can imagine the smile on my face, after 6 pulls of the flash mag cord, when I took my first shot, then it just kept going and going full auto was no issue and it emptied the mag all but maybe 40 rounds. The mag itself holds approx 340 so that's 300 rounds of gbb awesomeness with not a single bit of cool down. Worth every minute and penny I spent on it. So happy to share my work and I hope it inspires others to build bigger and better. Both mine and Adams plans are to eventually get it so you can still use mid/low cap mags but with a hpa air source. But that's quite tricky so far."


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