Introducing Our New Third Generation 16 Round 10mm Magazines for Rock Island Armory High Capacity 2011-Style Pistols

This is our third generation of magazine for the Rock Island High Capacity 2011-style 10mm and .40 S&W pistols that use the 16 round magazines – not the single stack 7-8 round mags.

This is one of the new mags. You can see a dummy 10mm round poking out from during testing.

These are converted Mec-Gar Para P14-45 magazines that have the feedlips adjusted and fine tuned to properly retain and feed 10mm rounds.  Note, a normal P14 mag can’t securely retain a 10mm round.  These tuned mags will only work with 10mm and .40 S&W.  They will not work on any other calibers or in a pistol that requires P14 mags.

To properly retain a 10mm round, the feed lips must be properly spaced plus this must be done correctly or the feed angle will be wrong.

The adjustment process and tooling took some work because Mec-Gar uses surprisingly resilient hardened steel magazine bodies and feed lips.  I had to develop a means to convert the magazines using a forming jig I developed.

Here’s a closer look at the mag lips. The finish wear is from the adjustment process.

Compatibility

These custom mags should work with RIA pistols that use the OEMP164015B magazine including the following pistols:

  • 51994 TAC Ultra MS 10mm
  • 51914 TAC Ultra FS 10mm
  • 56862 TAC Ultra Threaded 10mm
  • 52000 PRO Match Ultra 6″ HC 10mm
  • 52009 Rock Ultra FS HC 10mm
  • 51738 Pro Match Ultra H – 40S&W – note, I tune for 10mm as I don’t have a .40 so some minor adjustments might be needed.

Observations

Based on my past experience and some research, there are some really cool benefits from the new Mec-Gar P14 design:

  • Hardened steel bodies and feed lips will hold up very well with extreme use
  • Mec-Gar developed an anti-friction coating that aids in feeding
  • The magazine spring is made from type “D” music wire and holds up nicely
  • They developed a polymer base plate that fits very nicely in the large RIA mag well funnels
  • The slightly taller magazine body clears the RIA mag-well funnel very easily.  It’s longer than our previous generations of magazines and is even slightly longer than the original RIA/Act-Mag magazine
  • The magazine’s capacity is 16 rounds of 10mm. I was able to get 17 rounds in during testing but I feel that last round is just too tight. Thus, I am listing it as 16 rounds.

The polymer base plates work very nicely with the RIA pistols. You don’t need to change them unless you prefer longer plates. We do sell Dawson base plates if you wish to have one that extends further than the included Mec-Gar plate – The Dawson +100 plate is about the same height so if you do want the mags to be taller, you’d need either a +200 or +300 to see a difference. Please click here if you are interested in the Dawson plates.

These are all P14 mag bodies but with the different base plates installed so you can see the difference in thicknesses. The plates just change how tall the magazine is – they do not add capacity.
The OEM Mec-Gar base plate fits the RIA mag well funnel just fine. I set aside four mags for myself and am using the original base plate for them.

The Mec-Gar spring seems pretty robust.  If you want an even stiffer spring, we do sell Wolff magazine springs that are 10% stronger than the originals.  Please click here if you are interested.

The top mag is the Wolff +10% model. The middle is an OEM Mec-Gar without the floor plate and follower and the bottom is one with the floor plate and follower. Note, the Wolff Spring does require bending at the top to properly hold the follower.

After the mag lips are tuned, each magazine is tested in both my 10mm RIA 52009 Rock Ultra FS HC and 10mm 56862 Tac Ultra pistols to ensure proper fit and feeding.  You may find some final tuning is needed on your particular pistol and it is easy to do – please click here for more information.

This is my 56862. You can see one of the new mags peaking out of the bottom of the big flared mag well.
Here, one of the new magazines is in my 52009 that is locked open.

One small detail, since these were originally for .45 rounds, the mag round indicator counts doesn’t match since you will be loading either 10mm or .40 – usually you have one or two more rounds of 10mm/.40 compared to what the round count hole label says.

These holes were calibrated to .45 ACP rounds so the slightly thinner 10mm / .40 rounds don’t quite match up. You can fit 16 rounds of 10mm in here – not just 14.
Ok, this is pretty interesting. The magazine that Rock Island ships with the high cap pistols is made by Act-Mag and is in the middle. Notice that the original Mec-Gar P16 is a bit shorter and the P14 is just a tad taller. For anyone who found our earlier mags to be a tight fit, I’d bet the new ones will fit a lot better.

Conclusion

I feel like we’ve come a long way since the first P16 conversions. This mag is solid and comes in at a far more affordable price point than the P16s that needed the Dawson base plates also.

Click here to order if you are interested!


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