I'm about to build a pump mag. What do I need to know?

[rawbutter]

Okay, I've been collecting pump mag parts for the last year or so, and I'm finally ready to put it together. But I want someone to check my math and make sure I'm doing this right.

I have all the right parts. I have a pump milled rail (done by Luke) and a Rainman pump kit. (At least I think it's a Rainman kit. It's whatever kit is on this mag.) I also have a pump milled body, of course, and a stock Level 7 classic valve with a CF frame.

So what comes next after I put everything together? I know I need to replace the bumper with a wave spring (which I have). I also know that if I fire the marker with the wave spring installed and the bolt resets by itself, I might have to trim down the bolt spring. I don't know how much I should trim at a time, though. I'm figuring I'll just cut off a 1/4 coil at a time or so and then retest until I hit the right length. (I've got a few spare bolts springs, so I don't care if I screw one up beyond use.)

I've also read conflicting things about the wave spring itself. Some people seem to think that if the spring is trimmed to the "correct" length, then there's no need to add the bumper behind the wave spring. Others say that I should cut down the bumper to go inside the wave spring.

So yeah....any help would be appreciated.

[captian pinky]

Use a worn bolt spring it should be just past the tip of the bolt or even with the bolt. Don’t cut a spring it will only cause you headaches. Don’t trim the wave spring. Cut the bumper down to fit inside the wave spring.

If it’s resetting itself. Make sure it’s chronoed. Use a weaker bolt spring or your wave spring is toast.

If you have questions ask. A lot of people don’t know what they are doing when it comes to pump mags.


Sent from my iPhone using Tapatalk

[bowcycle]

The trimmed bumper helps keep the wave spring centered (although the body itself does that to an extent). So that is recommended.

If you do end up cutting on a bolt spring, I'd recommend even going with 1/8 instead of 1/4 and make sure to put the cut end against the bolt. I also suggest using a dremel or hack saw to make the cuts and not trying to do it with wire cutters. If using a dremel, go slow to keep the heat down; you don't want to make the spring more brittle by heating it up repeatedly.

I don't know that this is more extensively true or just my experience, but I always found it much easier to make pump mags work using a powertube spring instead of spacers.

Good luck!

[zulubravo44]

I might have just gotten lucky, but I chopped an old bolt spring about 1/8 rotation past where the curl leaves the flat terminal ring and it's worked for three years. Had to replace my wave spring last weekend because it wore out. I also had to make a new pump rod a few months ago, which was easier than I expected out of a wire hanger.

Oh, and if you're using a UL body, I'd highly recommend picking up one of KNM's snap on stock feeds. I've found that a lot of people don't really pay attention to movement if they're not cueing on a hopper, so you can dangle and sneak a lot more shots off with a stock class feed. Here's the link:
https://www.automags.org/forums/showt...90#post2916490

[bowcycle]

+1 for KNM's stock class feed.
If you want to go a bit further (and a bit more expensive), chop the feedneck off that body, drill and tap a 6x32 hole in front of it (like a phantom) and mount an Apocalypse springpheed to it.
I love my springpheeds!



This one is his model designed for ULE mags, but I used a phantom model on my riflemag.

[rawbutter]

Had to replace my wave spring last weekend because it wore out. I also had to make a new pump rod a few months ago, which was easier than I expected out of a wire hanger.
[/url]

How did you know the wave spring was wearing out?

[captian pinky]

when it not longer stops the bolt from resetting

[captian pinky]

Sounds like your bending it in the wrong spot.


Sent from my iPhone using Tapatalk