Jump to content


KWA LM4 PTS - Feed Ramp Polishing

feed ramp bb double feed lm4 polish jam

  • Please log in to reply
5 replies to this topic

#1 General Pickle

General Pickle

    Specialist

  • Members
  • PipPipPip
  • 313 posts
  • Gender:Male
  • Location:Oregon
  • Interests:tactical stuffs(airsoft, real steel, knives etc.), mechanical and manufacturing engineering, computers, gaming, the great outdoors
  • Country:

Posted 30 June 2013 - 12:18 AM

Hello guys! I've been gradually adding new parts to my LM4 to get the most performance possible and I've run into a hiccup that I could use some help with. For reference, my LM4 has an HNBR o-ring installed, an EVO II hop up set, I have shaved the back end of the nozzle in hopes of making the nozzle work properly (still may need more shaving), I have done the 'powerstroke' mod and I've installed a RS Magpul ASAP. My LM4 seems to shoot great when I'm firing slowly but only for about half of a magazine, and after that the shots all drop about 50 feet in front of me and double feeds have been happening much more than I would like. When this happens I open the gun and clean the bucking then put it all back together to fire a few rounds and the performance is great again for another half mag or so. I think I've narrowed it down to a couple of things: 1) My BB choice is no good and needs to be changed (BIOVAL .30's), though I don't think this is true because they feed and fly like gods except for when the double feeds happen. 2) The feed ramp needs to be polished. I think this is more likely since it would seem that the BB's are being 'shaved' as they enter the chamber, leaving dust and bits of BB on the bucking, eventually leading to crappy hop and seal. Perhaps this is also why the double feeds are happening.

My question is this: How should I go about polishing the feed ramp and what should I be looking for exactly? Any tool recommendations? I am an engineering student so I love a challenge and I generally have any tools needed but I would like to double check with people who have already done this to see if there is a 'best' way to do it.

Thanks guys, happy airsofting!

#2 -wigs-

-wigs-

    Enthusiast

  • Members
  • PipPip
  • 131 posts
  • Country:

Posted 30 June 2013 - 11:49 AM

Best way to do it is the take the 3 piece upper apart to get the whole feed ramp out. Then take a dremel with a felt polishing wheel and go to town.

#3 thatguyx

thatguyx

    Enthusiast

  • Members
  • PipPip
  • 89 posts
  • Gender:Male
  • Location:Edison, NJ
  • Country:

Posted 30 June 2013 - 02:51 PM

Besides polishing the feed ramp, I think you should try netpoc's o ring mod to keep the hop up in place. I think that could be a big reason for the 50ft droppers and double feeds. If you're uncomfortable dremeling the barrel, a small dollop of super glue on the black collar (dont get it anywhere else but the channel the brass tab rides in) could be used to test the idea.

#4 General Pickle

General Pickle

    Specialist

  • Members
  • PipPipPip
  • 313 posts
  • Gender:Male
  • Location:Oregon
  • Interests:tactical stuffs(airsoft, real steel, knives etc.), mechanical and manufacturing engineering, computers, gaming, the great outdoors
  • Country:

Posted 30 June 2013 - 04:17 PM

View Post-wigs-, on 30 June 2013 - 11:49 AM, said:

Best way to do it is the take the 3 piece upper apart to get the whole feed ramp out. Then take a dremel with a felt polishing wheel and go to town.
That seems like a good plan, though I'm a little worried about the 3-piece upper. If I were to take that apart wouldn't it be super wobbly in the future?

View Postthatguyx, on 30 June 2013 - 02:51 PM, said:

Besides polishing the feed ramp, I think you should try netpoc's o ring mod to keep the hop up in place. I think that could be a big reason for the 50ft droppers and double feeds. If you're uncomfortable dremeling the barrel, a small dollop of super glue on the black collar (dont get it anywhere else but the channel the brass tab rides in) could be used to test the idea.
I doubted the need for that mod originally but now that you mention it I think it may have some relevance and possibly the solution to my problem, or at least part of it. Thanks guys!

#5 -wigs-

-wigs-

    Enthusiast

  • Members
  • PipPip
  • 131 posts
  • Country:

Posted 04 July 2013 - 10:07 AM

Mine hasn't been wobbly since and I took it apart a few times. I just always punch out the pin for the top rail first and slide it off carfully, then take the two little screws out that are on the take down "arms" and then it all separates if I remember correctly. If your going to do it this way I would say since it's all apart and easy access to the inside I would polish the Chanel on both sides where the bolt rides as well.

#6 General Pickle

General Pickle

    Specialist

  • Members
  • PipPipPip
  • 313 posts
  • Gender:Male
  • Location:Oregon
  • Interests:tactical stuffs(airsoft, real steel, knives etc.), mechanical and manufacturing engineering, computers, gaming, the great outdoors
  • Country:

Posted 08 July 2013 - 04:24 PM

Alright here's a little update:
I used a dremel with a polishing head to clean up the feed ramps and such, then I reassembled it to try again. Double feeding seems to be fixed but the consistency was still an issue. I decided to dig deeper and found that my EVO II tension arm had snapped from the rest of the metal piece, meaning I had absolutely no tension being applied to my bucking. That explains all of the insane inconsistencies and other issues! I returned all of the stock hop up parts to the gun and now it functions like it did from day one. While I now need to buy another EVO II there was still quite a bit of good that came of this; I now know the insides of the LM4 pretty well and in the process of trying to fix it I've only improved it substantially in other places. New EVO II, maybe a new barrel, and this thing will be an absolute terror on the field. Thanks for the help y'all!





Also tagged with one or more of these keywords: feed ramp, bb, double feed, lm4, polish, jam

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users