Suomi Drum / M11 (RO) Conversion

[greenpeas]

Here's something totally unrelated....

The feed lip plates on some of these drums are not spot welded very well. I have a drum you can actually flex the tower because the spot welds on the original Suomi drum were pretty weak. I've started to add extra welds on the plates to make them stronger.

 

[medphys]

Another tip...

I have found that the joint where the inside-back of the magazine and inside-back of the drum meet, need to be as close to flush as possible.

If not, there is a twist introduced that seems to really slow down the feeding. I noticed this on one of my drums that wasn't feeding well. Once I realigned everything, it ran great.

Hopefully this will help out those having feeding issues.

 

[fred9x21]

1 click of spring tension puts the pusher arm in the "home" position. I then wind the spring 4 full revs and reinstall the arm. Then wind it and fill it. Is this right?

 

[medphys]

1 click of spring tension puts the pusher arm in the "home" position. I then wind the spring 4 full revs and reinstall the arm. Then wind it and fill it. Is this right?

I wind mine 5 full turns before attaching the arm. I have not had good luck with only 4.

 

[greenpeas]

Any tips on how much forward cant and any details on spacer that is used in the RO mags.

Buried somewhere in here I read...


"The internal width where the rounds are measures .412"

I measured the internal width of my tower and subtracted .412,
Now I knew how much space I needed to consume inside the tower.

I cut a sheet metal divider to fit the tower and went to the hardware store with micrometer in hand to find some spacers. I figured it would be easier to buy something than make it (I'm lazy). I found a good selection of woodruff keys and there were some the exact thickness I needed for around 80 cents each.

To make the divider I weld the spacers to the divider. I drilled 3
holes in the side of the magazine. Insert the divider/spacer assembly, clamp it and plug weld the spacers to the magazine.

I make my dividers extra long and use a hacksaw to cut the divider flush with the bottom of the tower.

The original C&S magazine appears to have been done in the same manner.

(the bumps on the magazine photo are for converting madsens to fit the M11, not part of the drum conversion)

I hope this helps.

 

[fred9x21]

Greenpeas,
How high up in the mag do you put your spacer?
And, do you put the zip ties in your drums?

 

[Stout]

Bicycle Chain Dummy Rounds

Has anyone looked into using bicycle chain for the dummy round spacers? I know that every two would be connected but the one I just checked has the same diameter as a 9mm case. It is narrow but a single dummy round on the end could make it guide properly.

I just checked and most chains are available in double rows.....

 

[greenpeas]

Greenpeas,
How high up in the mag do you put your spacer?
And, do you put the zip ties in your drums?

I don't set the spacer all the way up/flush with the top. I'll try and measure one this afternoon and add that information. I'd guess it's maybe 1/4 inch from the top? (The mags I'm using are different from the RO mags)

You really need to use the zip ties. (Medphys came up with that, he's a genius!) Use regular old JB Weld and lots of clamps, I've tried some various "quick" epoxy type stuff & it didn't work very well.

 

[greenpeas]

Has anyone looked into using bicycle chain for the dummy round spacers? I know that every two would be connected but the one I just checked has the same diameter as a 9mm case. It is narrow but a single dummy round on the end could make it guide properly.

I just checked and most chains are available in double rows.....

I think that was brought up before. I don't know if anyone tried it or not. I have a feeling it would bind up. I thought about using some timing chain sections from some old 440 engines I have laying around. I haven't tried it. I'm still not using any dummies.

You could use 1 dummy round to stop the drum. This way when you went to reload you would already have live rounds in your tower.

If you reload you could try to load some primerless 9mm brass for your dummies?

 

[medphys]

I don't set the spacer all the way up/flush with the top. I'll try and measure one this afternoon and add that information. I'd guess it's maybe 1/4 inch from the top? (The mags I'm using are different from the RO mags)

I have the spacer stop equal to about the distance of one round. My spacers are thick too, so I use the grinder to taper it so it matches the flow on the inside of the tower.


You really need to use the zip ties. (Medphys came up with that, he's a genius!) Use regular old JB Weld and lots of clamps, I've tried some various "quick" epoxy type stuff & it didn't work very well.

I wish I could take credid for it, but it wasn't my idea. tyromeo55 came up with it. Also, I use quick set JB Weld so you don't need to wait too long for it to cure.

.

 

[tyromeo55]

........I wish I could take credid for it, but it wasn't my idea. tyromeo55 came up with it.

It's a pretty simple fix really so I'm sure if I wouldn't of come up with it someone would of sooner or later. I finally got to shoot the three PAM mags that I have and think I have nailed one down that I'm going to hack up as a donor mag. I have a ton of projects at the moment (like getting a new heater in before it starts getting cold and finishing up my reloading room at the new house running electric to my shop.....) but, I'm going to try to to grind off the lips of the drum this weekend and get some measurements. If and when I get the thing put together I'm planning on parking it and could dip anyone else's if they want.

Here is a video of my buddy shooting the mac for the first time for everyone's viewing pleasure.....

 

[bucktim]

Im in the middle of the build, second attempt. Still working on friction issues but I think I will be okay once I install the zip ties, go 5 on spring tension, and clean everything up.

But I've read everything and I can't seem to get my rounds from nose diving. What is the angle on the mag to drum. It seems as if they are just coming up the stack parallel, instead up nose up? Currently at 8 degrees, measured from back.

A side pic of a working one would be great.

Thanks

 

[medphys]

20 degrees. Jammies not necessary.

 

[bucktim]

I redid the making of a RO single stack. Things are feeding much better, wont get to give it a try till later in the week. If still no go then I will make it 20 degrees.

Thanks

 

[clay5769]

Dummy rounds

Hi I'm new here I been kind of skimming this post and WOW some real smart people here..

 

[clay5769]

FYI I found some 9mm dummy ammo if anyone is still looking for some
.082 cents a round.. I have not bought any yet just wanted to pass this on.http://www.stactionpro.com/9-mm-action-trainer-dummy-rounds-p-1.html

 

[attherange]

When I built my Suomi drum for my M11/9 years ago, I used standard alum. round (which I cut to size) common at any hardware store. For my second Drum I used blank rounds (without the primmers) and used small washers to gain the needed spacing.

 

[clay5769]

I'm going to try and build a few different drums.
I have some 9mm Suomi drums and some PPSH41 7.62x25 drums

I want to make a drum for a 9mm carbine hi-point and some drums for my PPS 43 7.62x25 and my Sterling Carbine and Sterling Colefire pistol both are 7.62x25

 

[davep32618]

Cool stuff, I've skimmed the whole thread and I have learned a great deal. I have started building a couple of firearms and will probably take up a drum project at some point. The information here is fantastic!

 

[anm2_man]

I too have been working on a drum for my S&W76. But I found some aluminum tubing that I found has worked really good for dummy rounds.