hard to cock pump

Set-up:

Rainmain 229 kit
Luke's milled rail and body


Everything works, and can cock and fire in pump mode, but it's really takes a lot of strength to cock. There is heavy resistance somewhere.

If I loosen the bolt that attaches the Rainmain apparatus to the rail, then the pump shaft arm glides without resistance, but the whole thing is flimsy, and it doesn't cock.

I tried a washer between the rail and pump back bumper, but then I couldn't get the pump rod shaft to connect with the bolt correctly and it wouldn't cock.

Thank you for your thoughts.

any pics of the pump arm? or how you have it mounted?

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any pics with out the body to see how the pump are sits in the pump slot? with the pump kit mounted to the rail the pump arm should sit in the pump slot and you should be able to move the pump back as if you pumping the marker? it looks like the pump arm is screwed into the pump handle pretty far tho...so you might have to adjust the pump arm length as well?

Does the bumper sit INSIDE the wave spring? It should. If it is behind or in front of it, it will make it very tough to pump.

It's a tricky setup with three moving rods. I usually end up pulling everything apart except the pump kit and rail to find the binding points. You can hold the body on the rail and check the action after that, and work your way up to full assembly. Sometimes you have to bend the rod to get it set. It seems drastic, but it's hard to tell after you get all together.

Make sure your bolt bumper is inside the spring washer, not full size and behind the spring washer. With an old bolt spring that is about the length of the bolt, you should just need a "tap" on the bolt, not a stroke.

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Quote:

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Originally Posted by BigEvil

Does the bumper sit INSIDE the wave spring? It should. If it is behind or in front of it, it will make it very tough to pump.

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Thank you. The bumper is inside the middle and fits nicely.

Allow me to be annoying but how did the OPs title not trigger the language filter? :D

Not that it's the whole problem, but it looks like your rod tip is scraping. You want to bend the tip up enough to where the rod rides up the ramp on its "elbow" or bend, not on the tip. That means the bend is at a slightly higher angle than the ramp in the rail.

Check your rod length too. When the pump is back, the tip of the rod should be just past the catch surface of the sear, since that is where the bolt has to be pushed back. All the way forward should be clear under the slot in the pump body, to be sure of no interference.

If the bumper is in the wave spring then the only other 2 possibility are...

1. the rod isn't hitting the lip of the bolt like it should be

2. you cut too much off your bolt spring

A good way to tell where the rod is hitting is by removing the body and positioning your valve on the rail with the thumb screw installed. The thumb screw will secure the valve in it's correct place and you can see where the rod is hitting on the bolt when you slide the handle back.

It should hit right on the lip of the bolt. If not then bend the tip of the rod either up or down to achieve that mark.

As for your spring, you want just enough tension on the spring that it doesn't cock the bolt. If you cut too much off the spring then your going to be running into the issues your getting now. Ideally worn bolt springs are best for this. I always give back people their worn springs and tell them to label and keep them in case they ever want to convert their mags over to pump. Cutting is usually NEVER necessary and it's a easy conversion over from semi.

That pump rod doesn't look the right shape at all

The one on my XM15 kit has a definate hook to the bolt end, and the part that makes contact in the rail slot has a smooth radius for zero friction.

I can re-cock it with one just finger and very little effort on pump.

you know you're setup is awesome right when you can cock it by jerking the marker back and forth :D

I just recently watched cockerpunk's review of this pump kit. Is the set screw that holds the pump handle onto the pump rod in too far?

Quote:

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Originally Posted by emcl29

Allow me to be annoying but how did the OPs title not trigger the language filter? :D

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Great minds think alike. :D

Ive always used a Uncut RT bumper in my purple pump-mag. Been doing it for near 10 years.
Yes they wear very fast. Youll go thru a couple a season if you use it alot. So always keep a couple around.

A example. At tunaball 4 Dirge was showing me his pumpmag. I asked why hadn't he used it. He said it was difficult to cock. Sure enough you nearly had to stand on it to get it to cock. I went & got my gun pulled the bumper off my valve & pulled his valve, removed the bumper he had on it & put the RT bumper onto his valve. Instantly easy to cock. That was the only change.

Thanks to all for the comments.


Update: I put a metal washer and an O- ring between the rail and the pump attachement. This made the pump rod glide in rail more correctly. It works now, but it's erratic. It miss-cocks and causes a leak.

Does the pump rod ever get bent, or need to be bent a different way? Does one have to tune the pump rod shape?

I screwed the pump rod into the handle 360 degrees, thus moving it forward.

It seems to be working pretty good now.

Take your body off and install your valve only like so and see where the rod is hitting and yes you can adj (bend) the rod to where you need it. It should hit like so
http://i283.photobucket.com/albums/k...psdfaafcd1.jpg