Anyone else see the article in the april 20th SGN about the suomi based 9mm rifle? It looks pretty straight forward and the guy said he built it for about $175. I'm sure I have a complete spare set of AR15 fire control parts which would bring the price down as well as various other scrap that could be used. I think I'll order 2 suomi kits and give it a try.
The prices might of gone up in the past 2 years, but for the sten build he has the cd listed at $9.95 including shipping. Stone Axe Engineering, P.O. Box 125, Dept. SGN, Scott Ohio, 45886.
I worked on the Suomi bolt today. I removed the firing pin bushing and except for finding something to push it out with it wasn't anywhere near as hard as an AK barrel pin. The back of the firing pin bushing was soft and it looked like whoever put it in smacked it with a hammer a couple times so it would fit tightly in the bolt. I had the firing pin bushing chucked up in the lathe and the carbide cutter took the pin nub off so I thought I was home free but a HSS bit just left a mark on it and didn't cut any. I annealed the bushing and bolt to be able to cut them better. I drilled out the bolt for the AR15 fireing pin. I drilled the narrow spot in the front of the bolt just behind where the bushing sat with a .155" (5/32) bit. I used a .385" bit to drill out the back and set how far out the firing protrudes. I got the "honey its time to come" in before I could get the bushing drilled. The firing pin hole in my AR15 is 1/16" and thats the size I'll use on the front of the bushing. Because several Suomi builders have come across bolts that the center hole isn't centered, I went ahead and turned the bolt down .003" between centers to assure when I was later drilling the firing pin hole It would be better centered.
It just uses the bolt and barrel out of the Suomi kit. I had also thought about building it so it would take the suomi mags and drums. All you would have to do is put a suomi style magwell on it. On that gun it should be easier to get the suomi style magwell on the gun as you don't have the takedown feature to contend with. I am also going to try and use the original barrel shroud on my sgn-9 build. I got two kits both non matching and I am keeping the best parts for a future Suomi build.
That article will definitely get more guys interested in homebuilding. Much more so than the Sten articles. I was thinking it could also make for an interesting platform for a bolt action single shot or magazine fed carbine design.
I'm kinda torn on following his design or branching off a little. But I guess thats the great thing about home building, you can make what you want. I'm pretty sure I'm going with a bigger tube size than Matthews used and possibly a different recoil system. But we'll see, I've been kinda busy with build #3 Emily.
Moleman that is a great build. :thumbup1: Did you anneal the whole bolt or just a portion? I have heard they are very hard. Others have questioned the safety of an annealed bolt. I guess reheat treating is an option, but I would like to avoid if possible. Does anyone have good pictures of a Suomi mag well and mag lock-up. I was thinking about using Suomi mags/ drum.
Thanks. I annealed the whole bolt and the firing pin bushing after I removed the firing pin. Mine was hard enough that a file wouldn't cut it. You can get carbide drill bits to drill the hardened bolt, but I was planning on just re heat treating the bolt but not making it as hard as it was. I suppose if you didn't temper it enough it would crack or shatter. I"ve been working on the old firing pin and have turned it into a bushing for the new AR15 firing pin. Theres still a little fitting left to do before I put a picture of it up.
I think this particular "public build" (for lack of a better term) will spawn more than its share of interesting variations as guys use what they have and adapt to their own preferences.
I was thinking the same thing, but this might be to much for me at this time since I don't have a lathe. I'll have to think it through before I do anything, I don't want to turn a good part into scrap.
I also think there will be a lot of variations, people will just use the article as a rough starting point.
I was thinking the same thing, but this might be to much for me at this time since I don't have a lathe. I'll have to think it through before I do anything, I don't want to turn a good part into scrap.
I also think there will be a lot of variations, people will just use the article as a rough starting point.
If you have a drill press I think you could make the bushing pretty easy by making a drilling fixture. Just drill about a 1/2" blind hole the same size as the old fixed firing pin in a piece of metal held in the drillpress vise. Without moving the piece change the bit to the .062" bit and drill the rest of the way through. Repeat making another hole only using a .108" bit. I would secure the pin in a vise and place the drilling fixture over it and drill it with a hand drill/drill press and the same drill bits you used to make the fixture. I'd drill 1/2 way through both ends with the .062" bit and then use the .108" bit to set your firing pin protrusion. You may or may not have to set back the shoulder on the firing pin like I did. I'm sure someone here could help you out with turning down the bolt and making the barrel bushing. I've used this method to replace the Lee "unbrakeable decapping pins" that usually start braking after about 50,000 rounds.
I got the firing pin bushing done today. Here it is fitted to an AR15 firing pin. The firing pin tip hole is .062" and opens up to .108" for the first step of the AR15 pin. The only difficulty I had was I had to use my dremmel to set back the second step (red arrow) on the AR15 pin about .015" in order to get enough firing pin tip protrusion. I did this by turning the fireing pin in my lathe (but a drill would work just as well) and used the dremmel to lightly contouring the shoulder slightly back keeping the radius in the step. After I get the hammer slot done I plan on reharden both the bolt and the firing pin bushing then pressing in the bushing using red loctite and the pin that originally held it in. Then I'll run a drill bit down the firing pin hole to remove the section of the bushing retaining pin that will pass through the firing pin hole.
I probably should, I break at least 1 a year it seems. I'm usually in the middlle of a run of 5-10k when it happens so I just want it fixed. Heres the tool I came up with about 12 years ago before I got my lathe. It seemed that the decapping pins would break right as they entered the decapping stem leaving you with nothing to grab onto to pull it out. I would just chuck it up in the drill and file the pin stem down to the broken decapping pin which is much harder, heat it up and remove it with a set of pliers. Put the decapping stem in the block of steel and drill the pin hole a little deeper. Then loctite an RCBS pin in its place and trim it to .4" long. The first picture shows the 1" block with the stepped hole in it that I made with the drill press. The second one shows it with a RCBS decapping pin and the Lee one inserted.
I got a little more of the bolt done today. I still need to: square up and deepen the front of the slot for the hammer; fit a fireing pin return spring; and a fireing pin retaining screw. I made the slot by drilling some 13/32" holes and hacksawed/filed out the slot. It took about 2 hours. Heres a before and after.
I was re-reading the SGN article and looking at the ar15 fire control parts, firing pin and recoil spring and I got to thinking about another possible direction for this build. The ar15 9mm bolts and barrels are expensive compaired to a 223 bolt and barrel. The Suomi bolt can be turned down small enough to fit in an AR15 upper. The difference in lenght of the two bolts from the back of the firing pin to the front of the bolt is only .030" The differences being in the lip that protrudes past the bolt face. One problem that I see is that .450" of the AR15 bolt goes into the barrel extension so to use the ar15 firing pin set up you would have to recess the 9mm barrel in the same fashion to get the correct angle of the hammer striking the firing pin. I suppose you could just make a barrel bushing modeled after the ar15 barrel shank with a built in feed ramp of sorts. The Suomi mags and drums won't fit an ar15 magwell. but a modified sten mag will. The bolt would have to be modifed for the ar15 firing pin like the SGN-9, and a key added like the ar15 bolt so you could use the charging handle; the barrel bushing made (and barrel extended); and the magizines modified. Perhaps less work than the SGN-9.
I got a little more work done on the bolt. The front of the hammer slot has been squared up and the 8-32 firing pin retaining screw installed. Heres a picture with the firing pin installed. I'm going to try and use an inertia firing pin as I set the hammer .050" off of the firing pin at its full forward fired position. About .065" of the firing pin head sits out of the bolt body in the unfired position for the hammer to hit. If it doesn't work I'll keep trimming the front of the hammer slot until I get good primer hits.
The Prexis semi bolt counts a a US made part for $215, and they will also will modify your bolt for $120. The SGN-9 article said it took the guy about 8 hours total on just the bolt and I'm well on the way there. I'm going to try to make or modify all of the parts myself for this build. Today I got the feed lip squared to the bolt face and will try to get a picture of it up tomorrow some time.
if sombody scans the SGN artical I would like to have a copy of it. all of the racks were empty in all of the stors that I know carry SGN.
please and a big thankyou
muttman
I MAY BE JUMPING AHEAD BUT I WAS LOOKING AT THE REAR OF THE BBL SHROUD AND THINKING THAT IF I CUT THE LOCKING LUGS OUT THE 1 1/4 4130 TUBING SHOULD FIT INSIDE NICELY, W/ A BBL BUSHING IN FRONT. I LIKE THE LOOKS OF THE SOUMI BBL SHROUD AND IT SHOULD SAVE SOME $.
Neat idea to just cut the lugs out of the barrel shroud and slide it over the 1 1/4" receiver tube. The first time I read it I thought you were going to take the front section of the old receiver and weld that in place to get the receiver lugs for the barrel shroud. If you don't want to mess with a take down feature then that might be the quick and easy way to go.
The front of my receiver is cut right behind the lugs for the barrel shroud so I think it would be easier for me to just make another one. I was thinking about taking a section of solid round bar and making it sort of like the original Suomi receiver front from where it steps down for the bolt snout, all the way to the shroud lugs. I would make it small enough to slide inside the reduced diameter tube and weld it in place. It would be great practice for a real suomi build. Of course With all that work the prexis receiver might start looking real good.
I got a little more done on the bolt. The feed lip was trimed back so its flush with the bolt face. Heres a before and after. Except for turning the bolt down, making a slot to help cock the hammer, and heat treating its done. If you need a firing pin spring get a use the original suomi sear spring. It fits perfect over the firing pin and is plenty strong enough to prevent the firing pin from hitting the chambered round when the bolt closes.
I had a little more time to measure my receiver chunks and look at what would be a good alternative. I got (approximatly, they were dirty and I didn't clean them) receiver outside diameter 1.455", wall thickness .125", bolt diameter 1.215". At Wicks aircraft supply I found 1.5" steel tubing with a wall thickness of .188" and an inside diameter of 1.125". I plan on turning the tube down to the 1.455" outside diameter and the bolt to fit the inside diameter. The Suomi receiver is pretty thick, and this will end up just being a little thicker, but will look like the original.
YES,THATS WHAT I MEANT.GOING FORWARD WITHIT WHEN TUBING ARRIVES.
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