View Full Version : Promethus strike chamber jamming.

03-19-2009, 02:30 AM
I am having issues with the promy strike chamber jamming a lot. Compatibility could only be with the nozzle for the A&K sr-25 as the hop up rubber and barrel are also prometheus. The nub is the H-nub from element but i took that out and tested it again but it still jams. The only problem I had was with the hop up nozzle entrance being too wide. It would get stuck onto the gearbox shell where there is a hole for the air nozzle to come out of. I dremeled the hop up down a bit so it would not get stuck to the gearbox. My theory being that the barrel and hop up unit were not aligned with the nozzle because the position of the hop up relied on the gearbox where it would get stuck and not the outer barrel and or the tabs on the hop up. The stock metal hop-up was relatively loose compared to the prometheus one which also led me to that theory. So its still not working right but it seems to be working a little better. If anyone else has some theories let me know. Also I sprayed silicone oil down into the hop up, that seemed to work for about 30 rounds then it started to jam again I don't know if that means anything.

03-19-2009, 03:55 PM
cclark had a similar problem when he was building out his M21. It turned out that the Prometheus red hopup bucking was out of spec and the opening the BB is forced through was too small. He had to take a knife to it and open it up just a bit. Obviously, not the best solution, but it worked. Given the fact that a fresh coating of silicone spray worked for a short time leads me to believe you have the same problem or something very similar.

03-19-2009, 04:17 PM
That is very interesting. Did he use the red promy bucking along with the strike chamber? I had used the promy bucking along with the stock hop up and it performed fine. The only thing that has been upgraded where it could possibly jam is the strike chamber. Just trying to make it clear if cclarks issue was just because of the bucking or the combination of the bucking and the hop chamber. That bucking does fit really tight inside the chamber more so than I'm used to... The only replacement bucking I have are softer types. Would you reccomend that for use with an sp160 spring?

03-20-2009, 09:15 AM
The M21 is built off the M14 platform, so it's a totally different hop chamber.

I'm not familiar with the SP160 spring, so I can't answer your question. Who's the manufacturer? What's the reported muzzle velocity from this spring supposed to be?

03-20-2009, 10:07 AM
SP160 sounds like Guarder, which would be a M160-equivalent. The softer type of hop bucking will be fine, although it will wear faster.

It is feasible that the Strike chamber was dimensioned for thinner hop buckings, so the thickness of the Promy red hard one could be the issue. Also, another variable is the inner barrel, in that they are not all created equal in terms of outer diameter and hop-up cutout window.

Despite the 'standard' parts that most guns share, there are a lot of mismatched dimensions/incompatibilities between aftermarket parts.

03-20-2009, 04:49 PM
Yeah the SP160 is a guarder spring. I'm going to try to dremel the hop up some more, maybe its still a little tight. If that doesn't work the only thing I can do is switch buckings. How long do you think a Systema bucking would last? I'm hoping at least one full day of skirmishing.

Update: I put in a new Systema bucking and that fixed the problem. I just find it kind of weird that a Prometheus bucking wouldn't work inside of a Prometheus Hop-Up. I did compare the diameters of the two buckings, overall the Systema was actually wider also the BB entrance was wider than the Prometheus. If anyone could recommend a nice hard type bucking that would be cool I don't expect this Systema one to last that long.

03-20-2009, 11:11 PM
Run the Systema, it'll be fine for a while. If you aren't pleased with that, go to the purple Promy bucking. Those have always performed nicely for me, whereas the only red (hard) Promy I tried had troubles. It was in a M130 spring level RPK and had very poor muzzle energy, as the bucking's lips were so tight they would barely let a BB through. Switched to a different hop bucking and the gun shot the way it was supposed to.
I chalked it up to an out-of-spec part and tossed it, but in just looking around a bit online since you jogged my memory, it seems others have had the exact same problem with the hard red Promy bucking.