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View Full Version : C Products DPMS .308 20 Round Mag - Blocking


ugimports
05-14-2010, 2:12 PM
Can someone tell me where to rivet the mag to block it at 10 rounds? If not, I'll go buy some rounds to figure it out, but wasn't sure if someone already is blocking these and can tell me the measurements.

Thanks,

The Custard Pirate
05-14-2010, 3:25 PM
This brings up an interesting question. Is it legal to modify your own mag. to only hold 10 rounds and are there any rules about how it has to be done?

ugimports
05-14-2010, 3:40 PM
This brings up an interesting question. Is it legal to modify your own mag. to only hold 10 rounds and are there any rules about how it has to be done?

The Calguns wiki has some information about "permanence". If you have your own legal hi-cap mags you're better off keeping that way since you'll never get them again. Purchasing parts kits allows you to build up blocked mags.

In general the most common way people block mags are:
1) Rivet follower
2) Rivet follower+some kind of block+epoxy/welded floorplate
3) Modified follower with some type of rod or plug that stops it at 10
4) Some kind of insert in the mag body that stops the follower either welded or epoxied to the mag body

Now 1-4 may or may not meet what Calguns Wiki/Legal minds determine as permanently altered, but the market conditions have pretty much shown nobody has been busted for these (yet of course) so I feel the risk is fairly low on it being classified as a "hi-cap" mag in a fixed mag rifle.

I'm going the route of #1 -- also note, I'm a dealer and the reason I'm doing this is that I need to deliver a 10 round mag for my customers rifle since the distributor sent me a 20 round mag. I could give it to my customer as parts, but he'd be quite annoyed that he'd have to block it on his own after spending 4k on a rifle (and I would be too).

Here's a reference to that particular page:
http://wiki.calgunsfoundation.org/index.php/Large-capacity_magazine_restrictions

Anyway, back to my original topic -- anyone can help me with measurements? :)

shark92651
05-14-2010, 8:08 PM
It can be a bit tedious to get it right, even if someone had the exact measurements for you. Trying to block a single magazine may take a couple tries, therefore you may end up with more than one hole in the mag. Try this:


Remove floorplate and spring.
Turn the mag upside down and load 10 rounds in.
Insert a thin rod or a wood dowel along the edge of the mag until it makes contact with the follower at the location you need to rivet.
Mark the rod and remove it.
Now you have your measurement. Add about 1mm to allow some give to insert on closed bolt.
Drill hole, insert rivet and test capacity before you pop it.
Test load it. If it holds < 10 or > 11 try again (this is why it's best to consider the first one a throwaway prototype).

ugimports
05-14-2010, 8:37 PM
It can be a bit tedious to get it right, even if someone had the exact measurements for you. Trying to block a single magazine may take a couple tries, therefore you may end up with more than one hole in the mag. Try this:


Remove floorplate and spring.
Turn the mag upside down and load 10 rounds in.
Insert a thin rod or a wood dowel along the edge of the mag until it makes contact with the follower at the location you need to rivet.
Mark the rod and remove it.
Now you have your measurement. Add about 1mm to allow some give to insert on closed bolt.
Drill hole, insert rivet and test capacity before you pop it.
Test load it. If it holds < 10 or > 11 try again (this is why it's best to consider the first one a throwaway prototype).


Thanks, I figured as much.. I bought a box of rounds at Big 5 today. So I guess we can consider this thread closed ;)

My plan of action was pretty much spot on to what you recommended as well. It helps to confirm that my strategy seems like it would work.