Older Promag Duckbills

[Justin Hell]

I cannot seem to find any information about this anywhere...

About eight years ago, I picked up a used 20 rd Pro Mag out of a parts bin at a LGS for a few bucks. I didn't notice at the time, but one of the feed lips was missing about a third of itself, as a result...it was rather picky about feeding. I didn't really think much of it...but I did notice the body of the magazine had lips for both 10 and 5 round options...fast forward to today, I decided to perhaps reduce the spring tension on the mag, and cut it down to the 10 round position.  I cut the spring down a few coils less than 50%, ultimately ending up with a one coil less than 50%, yet it will not allow for anything but exactly 10 rounds, with no give to put it into a drop free modded gun.

Is this the way old Pro Mags were? Was it a safety thing where you HAD to install and chamber, or leave the bolt open?   

I suppose it doesn't matter much to me, I have a detachable I can use from a bench rest, and load with stripper clips.  I cut the thing pretty much exactly as a ten round mag should have been from the factory, maybe I should still remove more coils?  If anyone has a PM 10 rounder, I would be curious how many coils are on the spring.

[firstchoice]

Hey Justin.
 
  Just found your post on the ProMag Duckbills. I have a collection of older drop-free mags for SKS but I'm not sure which is which. Do you have a pic of the mag or the spring?

  A link to pics or the pics themselves may help me to know if I have anything to help you.

  Let me know.

  firstchoice