Pump mag binding

[robertreed711]

So I just picked up a pump mag with a rainman pump kit. It works well if you pump it using the pump handle, very short and smooth stroke but if you try to pump it using the hitman mod it binds up.

All I can tell is there is just too much play between the center guide rod and the pump handle.....

I have no experience with these so I may be missing something, any advice is appreciated.

Of course, a pic for good measure
http://i946.photobucket.com/albums/ad310/snowboardguy7605/Mobile%20Uploads/20140728_174746_zps85afe307.jpg (http://s946.photobucket.com/user/snowboardguy7605/media/Mobile%20Uploads/20140728_174746_zps85afe307.jpg.html)

[need4reebs]

looks like tha pump rod is bent.

[robertreed711]

It is slightly bent but I don't believe that's what is causing the problem. Good eye though.

[BLachance75]

The rod does look bent down, at least in the middle.

Try taking the pump handle off of the back plate. I had to adjust my guide rod a little to get the pump to slide smoothly.

[dboggs79]

I've yet to see one of these pump kits that I've been impressed with yet. Every one I've seen, in person or in pictures seems to be off. I'm guessing a lot is due to loose tolerances. The other part i believe is because the two pump guides aren't long enough to give it a steady position at the front of the pump stroke. They all appear to be "nosed" downward when in the forward position. A lot of this honestly guessing . I've never had one taken apart and thoroughly inspected it. I did see where Rainman himself commented on the last run of these kits being poorly made. Or atleast certain components anyway.

Edit: Try moving the spring to the rear of the pump plate and putting another on the bottom guide rod.

[need4reebs]

yeah i thought it appeared nose down as well…but from only one pic its hard to tell? but that pump rod shouldn't look/be like that and would be my first guess for binding.

[BLachance75]

Let me know if you're interested in selling the hitman

[dboggs79]

yeah i thought it appeared nose down as well…but from only one pic its hard to tell? but that pump rod shouldn't look/be like that and would be my first guess for binding.

I would guess not since he said it seemed to work fine using the pump handle. I'm guessing the hitman handle is producing enough leverage to bind what appears to be a sloppy kit.

[river031403]

Link to original sales thread
http://www.automags.org/forums/showthread.php?268072-FST-All-Black-ULE-PumpMag!!!!&p=2857128#post2857128

[river031403]

And most recent shooting video
http://youtu.be/XR7s30tpJCk

[need4reebs]

definitely a sloppy kit…from tha pump rod to tha hit man kit to tha pump plate to tha guide rods to tha pump handle.

[robertreed711]

And most recent shooting video
http://youtu.be/XR7s30tpJCk

Yes, this is exactly how it functions, a very short smooth stroke when using the pump handle.

I have read that the binding was common with these kit and that rainman has a remedy for it. I have contacted him on MCB and will see what he has to say.

http://www.automags.org/forums/showthread.php?260502-Rainman-Pump-Kit-Binding

[OPBN]

If it's a stock AGD milled rail his solution is going to be have it milled deeper. I'm his own words this kit is not milled to AGD specs and he doesn't guarantee it to work with any bodies or rails not milled by him. I had mine on a factory milled rail and it bound as well. Put it on another 3rd party milled rail and it works better. Still not as smooth as my AGD or XM15 kit. I always thought part of the problem was the mounting plate did not sit flush with the rail due to improperly milled angle.

[robertreed711]

If it's a stock AGD milled rail his solution is going to be have it milled deeper. I'm his own words this kit is not milled to AGD specs and he doesn't guarantee it to work with any bodies or rails not milled by him. I had mine on a factory milled rail and it bound as well. Put it on another 3rd party milled rail and it works better. Still not as smooth as my AGD or XM15 kit. I always thought part of the problem was the mounting plate did not sit flush with the rail due to improperly milled angle.

He may claim this but from what I can tell the problem is actually that the pump plate tips when using the hitman mod forcing it to bind on the center guide rod.

[captian pinky]

i have tried to warn everyone about the gen 3 kits. some people say theres are fine others say they are crap.

i was one of the original buyers of the gen 3 kits and i sent mine back to rainman to get multiple issues fixed and he said he didn't have a kit that met my expectations and refunded my money.

[OPBN]

He may claim this but from what I can tell the problem is actually that the pump plate tips when using the hitman mod forcing it to bind on the center guide rod.

Could be as well. I wasn't using a hitman mod so I was just going by what I was told in my circumstance. I will say that when I dry fit mine and messed around with it I found it pumped much easier if you kind of pushed up on the handle when pumping it. I could see how the hitman mod would excacerbate the issue.

[BLachance75]

My thinking is that part of the problem is the design of the lower guide rod itself along with some subpar milling. The use of a skinny bolt as a guide rod and the fact that the handle rides on the bolt head is a poor idea. I would have made a little thicker rod and put a hex on the end, similar to what CCM does. All the holes are milled oversize making the kit have wobble, more than I would have liked at least. Mine does slope down like almost all the others and it did bind on a rail that was milled to AGD spec. Rainman milled the channel slightly wider for me and that stopped all binding issues.

If I were to go about building another pump mag I would hold out for an AGD kit or buy a gun that already had one.

[thecroatiansensation]

I am guessing this is the pump that I put together. The reason that the rod is slightly bent in the middle was because it was rubbing against the front lip of the ule body. Since I didn't want that to happen, I bent the pump rod a little down, then back up. It worked fine and pumped smooth as silk when it left my hands.


I have also had an issue trying to use a hitman mod. One thing that you can do is bend the pump rod a little bit to make up for the upwards movement that will occur when you are using the hitman mod (does this make any sense to anyone?). What I have found is that when you use this hitman to pump most of the force is used to push backwards, but since you aren't pushing directly backwards, the back of the pump handle kicks up a little bit and contacts the guide rod. This will cause enough friction to mess up your pump stroke.

I also put a little bit of lube on the guide rod as well. Just tinker with it for awhile and you should be able to get it working right. PM me if you would like any more info.

[BigEvil]

I have never seen a pump kit that there is not at least some issues with. On the RM kit, in addition to the slop, the pump stroke is also ridiculously and unnecessarily long. I have shortened them up and it helped the binding issue mainly because it didn't have that far to travel to get cocked and then bind up. In reality, you can make the pump stroke less than 1/2".

[BLachance75]

Hmm, my kit it only about 1/4" and I didn't do anything to it. I've thought about making it shorter but even now it is almost to short.

[river031403]

This pump in this thread has a short stroke and smooth. I had to sell it to get a football helmet for my son.
http://i1083.photobucket.com/albums/j381/river031403/72ADF700-1D24-4D5C-892C-2EE3D23C3901_zpsctbycrss.jpg (http://s1083.photobucket.com/user/river031403/media/72ADF700-1D24-4D5C-892C-2EE3D23C3901_zpsctbycrss.jpg.html)

[bowcycle]

And most recent shooting video
http://youtu.be/XR7s30tpJCk

Here's your primary problem...never buy anything that involves hairy man-boob! ;)

[river031403]

Here's your primary problem...never buy anything that involves hairy man-boob! ;)

Fresh out of the shower.^^^but as you can see in the video no issues

[SPLATTER-ZONED]

All I can tell is there is just too much play between the center guide rod and the pump handle.....



That's the problem on my gen3 kit. It's binding when using hitman mod even without the pump rod installed.

I don't have the tools to do it, but maybe the handle could be bored and sleeved. Make the tolerance a little tighter.

That being said, my gen2 kit is beautiful, smooth, short, and fast.

I'm going to light my gen1 kit on fire, throw it under a lawn mower, and pour acid on whatever is left. POS.


SZ