I'm just about done with the final update to my mega-DMR, assuming it doesn't explode. The gears have been switched to the Guarder ITU's, the piston is a Guarder Half-Tooth, wiring harness is G&P and it's been installed in the 8mm bearing lower. Right now, it's running VERY smoothly and so far is showing no ill effects from the custom bushing setup.
Since it's now running smoothly, I can give more details on the lower. The holes on the lower were bored out to hold 8mm bushings on a wire EDM. However we did not have a way to replicate the bevel so the bushing stick a little further inwards then normal. This caused us some concern as ICS's use almost no shims to begin with but so far it's working very well. The next issue was that the ICS Anti Reversal latch would not clear the massive ITU gears. Unfortunately there was no way around this, so the gun is using a standard TM compatible ARL. This means no spring release on the gun but other than that no ill effects as of yet. Last but not least, the holes on the bushing were to small to fit the ITU gears so we had no choice but to ever so carefully grind down the axles on the Gears with a dremel. Again, no ill effects as of yet, but it's still early.
The next issue I've just ran into (as of last night) is what I can only call a failure of the MAG MS190 spring. I was getting crap compression on the Modify Boreup assembly and the nozzle had shattered so I decided to chuck it and put in a standard full capacity set. The gun is only running an M16 barrel at this point anyways. The only one I had was the one from my SRC HK416. While I'm not a fan of SRC parts, I do have to admit that after relubing it was getting a nearly perfect airseal. So I put it in and went about the task of reinstalling the spring. Now, bear in mind, it took two people (both experienced techs) almost 10 minutes of fighting to get it in last time. This time it went in easy as pie. I looked at my brother (who was assisting) and he just says "so, what did you need me for?". I was rather confused at this as it was so easy I probably could have done it myself.
So, I look the whole gearbox over and everything looks fine. So, I load the gun up and take it out side to chrono....
463fps-479fps with .20's.
Hmmm, that's a 200+ fps drop from the last chrono earlier in the week. So I completely take the upper apart, recheck everything. Confirm again that the airseal is nearly perfect. I test the spring with my hand and I could swear it feels softer than before, but that could just be my mind playing tricks on me. I reassemble it (without assistance this time) and chrono again. I use a separate batch of BB's just to be safe.
So, for lack of a better word, the MAG spring has suffered a failure. The spring makes a great M130 at this point but that's not what I am looking for. So, I'm planning on ordering an M210 spring some point this month to replace it.
With all that said and done, I do have to say, this whole experience has actually been pretty fun. It also, once again, reinforces my opinion about the quality of ICS's gearboxes. This gearbox has been tortured like no other and is still kicking. I also give props to the Deep Fire Titanium piston. They suck for high ROF setups but it didn't have a single hiccup in a high FPS role.
The finish has been worn off the teeth rack but other than that, the piston looks great. The teeth do not appear to be worn down at all.