I didn't discover this, there is chatter on the internet about it.  The claim is that MDT Tac AICS magazines fit in the CTR bottom metal.

I bought one to try it out. It was a very tight fit, but it did technically fit.  I also confirmed that it feeds properly, though the bolt rode over the first round of the mag the first time I tested it.


Because it was a very tight fit initially, so I measured it to compare it to the CTR magazine.

CTR magazine dimensions:

Width: 0.98"
Length: 1.05"
Height from top of mag to magazine release hole: 1.30"

MDT AICS magazine dimensions:

Width: 0.97"-1.00"
Length: 1.07-1.10"
Height from top of mag to mag release peg: 1.39"


The MDT magazine is not square, the top is narrow and gets wider as you go down the magazine body.  This makes for a very tight fit.

I sanded the sides and front down a few thousandths and the magazine fits much better.  Its still tighter than a CTR magazine and won't drop free, but it doesn't get stuck in the magwell.

I got some pictures.  You can see the spots that needed to get sanded down some, the sides near the back of the mag, and the front edge.  The same spots that wore down on the Tikka mag.

What coal will the MDT mag accept? I love the Tikka mags because I can load to 2.92 or a hair more, if I replace the stock I'll have to find something that takes the ctr bottom metal.

I can confirm that I've seen the same with a MDT mag in my CTR.  My CTR is currently sitting in a XLR Element and oddly enough the MDT mag actually latches in easier w/ the factory stock and bottom metal.

It measures 2.855 in my magazine.  That's a fair bit shorter than the Tikka mag.

Manners inlets for the CTR bottom metal, and McRees precision makes a chassis that accepts CTR magazines.

Those are the two I found as well, I'm going to go with the Manners when the time comes.

I like that color scheme. Was thinking of painting my stock but I think the barreled action looks much better.

Its going into a Manners stock painted in their woodland pattern eventually, so there should be very little black left on the rifle.

I bought two MDT mags and factory length 308 would not fit in them, I had to return them.

Just for reference, factory hornady 140 ELD fits in my MDT mags, as well as 130 gr prime

6.5 creedmoor on both

Good find. What does the MPT Magazine weigh?

Where's the best place to pick up one? I've gots CTR arriving tomorrow. So looking for some mags.

Just thought I would post a heads up for y'all...The factory CTR magazines have magically dropped in price by about 50% now and can be had for  $72.43 CTR Mags. As good as the factory mags are, and at the newly discounted price, I will continue running them.

They've been back ordered for quite some time now, cheap is only good if you can actually find them in stock

They just had some in stock a couple of weeks ago, they just sell out very quickly. I picked up a few more this last time around. You just have to check the website daily.

At that price, im staying with the ctr double stack mags as well.

OP, I just wanted to say thanks.  When I saw this, I ordered an MDT polymer mag from Raven1Tactical.  When it arrived, I pressed it into the CTR and paid attention to the rub spots.  I ended up sanding it just a little on the top of the back side--above the protruding mag catch.  I took off very little, then rounded the corners just a bit.
The mag fits now, but it is definitely tighter than the factory box.  You have to depress the mag release fully and pull straight down to remove it, but after doing it a few times, it became reasonably natural.
It won't be my primary mag for this rifle, but in the principle of "one is none," it makes a good backup.

Finally had a chance to take it out this past weekend and, oddly enough, I had the same results you did--the first time I tried it, the bolt rode over the cartridge! 
Wondering if maybe I hadn't seated it fully, I reloaded the mag, firmly seated it and closed the bolt again--and this time it fed normally.
I then cycled three rounds as quickly as I could work the bolt and had no problem.  The mag (and rifle) worked fine with FGMM 168gr ammo. 

Those first three rounds, incidentally, grouped just under 1", which impressed me because I was focusing on working the bolt more than on accuracy.
The rifle will stay on the family farm where it will probably never see a shot past 400 yds, but I'm sure it'll serve well in that role.