Suomi Drum / M11 (RO) Conversion

[medphys]

youtube: carlson tower test

Have fun, let me know what you think.....maybe I'll dust it off soon.

Nice! It's hard to believe that it keeps up with a stock upper.

[attherange]

Yea, I had to "tweek" it a little. It's not your average conversion, I used two flats inside that are independent of the tower. These same two inner liners/walls also have small tabs that I can flex for proper feeding of the rounds. There is a lot more to this conversion than just cut and weld.
Thanks,Greg

[medphys]

I used two flats inside that are independent of the tower.

And I may do this as well. Right now I am only using one.

There is a lot more to this conversion than just cut and weld.
Thanks,Greg

Yeah, no kidding!

Thanks for your input!

[strobro32]

I only had a few hours to work on mine.

I had to change the feed ramp guide design twice and I may need to do it again. I added notches to the race way for the drum lids. I also am thinking about shortening the tower as it will take 43 dummy rounds to work as it is now. I think I can get it down to 36.

I hope you guys can figure out the low friction strips before I get to that part.

[attherange]

It was a while ago, I had a detailed thread (uzitalk) on the process of construction. I can't remember if I had any before and after pic's.

[medphys]

I only had a few hours to work on mine.

I had to change the feed ramp guide design twice and I may need to do it again. I added notches to the race way for the drum lids. I also am thinking about shortening the tower as it will take 43 dummy rounds to work as it is now. I think I can get it down to 36.

I hope you guys can figure out the low friction strips before I get to that part.

I was pleasently surprised that the zipties worked. Chili used a cut-up zytel mag so my guess is that anything slick will do the trick.

[tyromeo55]

I was pleasently surprised that the zipties worked. Chili used a cut-up zytel mag so my guess is that anything slick will do the trick.

Its amazing how so many problems are fixed by simple solutions. I'd hate to have to cut up a zytel (I dont have any bad ones to cut up). Are the ties you used taller then the metal ridge?

[medphys]

Are the ties you used taller then the metal ridge?

Yes, the dimentions are almost perfect. It is thicker than the ridge, but thin enough that the inner piece fits right in.

[tyromeo55]

Just for grins... You might take some 100 grit + sandpaper and run it over the ziptie strips lightly just to abrade it up a bit. That should lower the resistance a little more

[medphys]

Just for grins... You might take some 100 grit + sandpaper and run it over the ziptie strips lightly just to abrade it up a bit. That should lower the resistance a little more

Good idea. I think the strips help keep the rounds from getting double stacked in the drum too.

[medphys]

Still having issues feeding the first 20 rounds. The malfunctions are rounds nose diving into the magazine or feed ramp.

After that, it runs just fine.

[attherange]

Check the spring tension, and the check the feed lips.

[medphys]

Feed lips look good and are nice and smooth. I adjusted the mag catch so the mag sits as high as possible in the well without the feed lips rubbing on the bolt too.

The spring came wound with 3 3/4 turns. I was reluctant to try another turn, but I'll give it a shot.

[attherange]

If there is enough spring tension to feed the rounds without issue, you can try to open up the font of the feed lips. This is going to be a VERY MINOR adjustment. Do not over bent the lips.

[chili17]

nose dive = to much friction and or not enough spring tension

[strobro32]

Version 3.0 is on my bench. I've got my dummy round count down to 28.

I'm having serious doubts about a double drum working, if you guys are having trouble feeding a lite single stack.

[trek45]

I have a C&S M11/9 drum, and the first time I tried it, it ran flawlessly until it got to the last 5 rounds (I loaded all 72 rounds in there). For the last 5, the rounds would stick straight up. So when I got home, I took it apart and cleaned everything down, oiled it up, and reassembled. I took it back to the range loaded with maybe 50 rounds, and I maybe got a few shots out of it before giving up.

I made sure to count the number of revolutions when I took the rotor off, and it sure seemed like 3. But maybe I counted wrong. I'll take it apart again and check it out, and if nothing is out of whack, I'll add another spring revolution.

FWIW, the drum has teflon (or some kind of plastic) strips around the inside perimeter of the drum.

[medphys]

Version 3.0 is on my bench. I've got my dummy round count down to 28.

I'm having serious doubts about a double drum working, if you guys are having trouble feeding a lite single stack.

After taking a closer look at things, I think my problem is the feed angle. On my stock magazines, both the rear and front of the rounds are held up tight against the feed lips. With the drum, only the rear of the rounds are tight. The bullet end of the rounds are kind of "floating" there so when the top round is stripped, the rims catch and the next round in the tower is pulled forward a bit and tilted downward. This puts the feeding round in the wrong orientation to be fed properly. Reluctantly, I am going to adjust the forward tilt of the tower one more time. I'm sure there is a happy medium with the tower angle which will give the optimal feed angle with minimal friction between the primer side of the case and back of the magazine.

[Vegas SMG]

OK, here's the dumbest question yet... Does Centerfire have the best price on the drums? I find myself needing a half dozen or so.

I had a bunch of drums, (nice ones!), and Suomi coffin mags when I owned the SCA upper but I sold them all off.

[tyromeo55]

It's the best price I could find. They charged me 9 bucks and some change for shipping though so as long as the shipping price does not get too high then they would be hard to beat