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Suomi build

18K views 78 replies 18 participants last post by  BIG 54R 
#1 · (Edited)
Since I chronicled my first suomi-ish build that started out as a sgn-9 build I figured I'd start a new thread since build #2 is definitely going to be a suomi when I'm finished. I started with a suomi kit froms copes and 1.5"x.188" wall thickness 4130 steel tubing from wicks aircraft supply. I turned the approx 10-3/4" receiver tube down to 1.465" between centers and threaded the last .450" (the original suomi's have .4" threading) of one end 20 tpi for the end cap. I noticed that the front 2-3/8" section measured 1.455" diameter so I turned it this receiver down to that measurement. On my next one I will leave the front section full size until I weld in the barrel bushing. That way I can just turn down the welds and hide them. Next I took a cylinder hone and lightly cleaned out the receiver tube. I then took a 5" section of 1-1/4"x.250 wall tubing and cut it into a barrel bushing. The section that fits in the receiver tube needs to be 1-2 thousands over the i.d. of the receiver tube for a press fit. I copied the lug area from several different suomi receiver sections as well as using measurements from my first build for overall length. The length from where the barrel collar rests (not including the indexing nub) in the front to the back where the bolt is stopped on my first build was around 4.24" to obtain the proper headspace. I left this barrel bushing at 4.270" (with the extra length in the section that goes inside the receiver tube) so I can turn it down later to get the correct headspace. Since this is a blowback type gun it isn't as critical as a locking action, but on my first build if I let the leading edge of the bolt contact the barrel it would buckle the cases of my dummy rounds because of the short headspace. I used a max trim length 9mm dummy round as a guide and added a few thousands for good measure. This left me with 4.245" for my barrel bushing length.
The inside of the barrel bushing is around 3/4" and a suomi barrel is around .78". To keep from getting a sbr violation on my first build I: lengthened the barrel to 16-1/4"; turned the barrel shank down to 3/4"; enlarged the indexing nub to 1/4" and welded on the barrel jacket since I didn't cut the lugs into it. Even without welding on the barrel jacket there was no way an unmodified suomi barrel was going to fit in the receiver. On this build I am using the same larger indexing nub, reduced barrel shank and welded on extension to avoid a sbr violaton.
Since this is a work in progress I'll add some more pictures over the next few days to bring the build up to where I'm at. Here's a pic of my first build That I still need to put a finish on and some pics of the receiver and barrel jacket of this build.
 

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#4 ·
Thanks, I really like the suomi. My first one is a bit rough but I've relearned alot of what I forgot in machine shop from highschool over the past year so this one is turning out much better. I left the stock on my first one as I got it and it was by far the worst of the bunch, but I think it gives it that battle field pickup look.
 
#3 · (Edited)
barrel bushing

Here's a drawing of the barrel bushing with the barrel jacket lugs. The actual specs may be a little different as I have changed some such as the indexing nub to prevent the insertion of an unmodified barrel. I got these measurements from the the largest dimension off of several demilled suomi receivers, figuring anything smaller was a result of wear. I basically started with a 5" section of 1-1/4"x.250" wall 4130 seamless tubing which has a .750" inside diameter. Turned both ends and turned down to 1.240" between centers which was pretty much as light of a pass that would take metal off all the way around the bushing. On my first build I left the lug area the full 1.250" and it was just starting to fit snug. The bushing diameter on my suomi receivers at the lug area is 1.235" on average. Since I know a 1.25" lug will fit I decided on the 1.240" so it would have some room to turn when dirty. I then turned the bushing down to the basic profile leaving the front area longer to cut out the indexing nub and making sure the section that goes inside the receiver tube is 1-2 thousands over the inside diameter of the receiver tube. A quick note of on the 1.040" diameter section between the receiver section and the lugs. I had measurements of between .395"-.4" for this width. I went with the .4" as any looseness in the barrel jacket fit can be eliminated by pushing the barrel bushing deeper into the receiver. If you make this area the .395" then make sure to lengthen the receiver section of the bushing to maintain the 4.3" overall length.
The next step was to cut the barrel jacket lugs. If you look at a suomi barrel jacket lug it's .4" front to back. Top to bottem it is tapered smaller to the center. The bottem of the lug measures .4" but the top on the 4 receivers I checked measures anywhere from .440"-.460". The smaller measurements came from well worn receivers. The one I have that looked almost new had the .460" lug measurement. Since the bottem of the lug is .4" you have a wide range of what they could be and still work. I tried to get it as close to what the new receiver was at .460". I don't have a dividing head so I used the tape method to mark off the lugs. I took a piece of scotch tape and ran it around the lug collar, trimming it for width and cut through the overlaping ends (removing the extra scrap) to end up with a piece of tape that was exactly the size of the lug collar which I taped to a steel ruler with the end and a side matched to the ruler. There are 4 lugs each .460" so I multiplied that by 4 and subtracted that from the tape length. Then I divided what was left by 4 to get the spacing between the lugs. I then colored the tape black with a sharpie and alternated scratching lug or space lines with my dial calipers in the black sharpie on the tape. I then covered the first piece of tape with a second piece to keep the sharpie from smearing. I put the tape back on the barrel collar and used a piece of 1/2" angle iron as a guide to cut the tape with a utility knife through each scratch line. I removed the larger sections of tape leaving the smaller .4"x.460" lug tape. I then squared up the bushing on the milling machine with one "lug" on top. I ran a dial indicator across the top to make sure it ws totally flat after each time I moved the bushing. I cut the front of the lug collar until the 1/4" 4 flute end mill touched the tape. I then cut the back side of the lug until the lug was .460". Then I repositioned the bushing and repeated until I had the 4 lugs roughed out. I made one cut in the center of the "lug gap" to remove most of the extra material. I then locked a section of 3/4" rod in the vise with 5-6" sticking out and slid the bushing over the rod. Using an air cut off tool I rested one side of the cut off tool wheel cover on the 3/4" rod and ground between the lugs while I rotated the bushing lug to lug. When I though it looked good I colored the gap area in sharpie and tried to fit it in a barrel jacket. I reground any high spots until the bushing turned in smoothly.
To cut the index nub I marked off a 1/4" nub centered on one of the lugs. I clamped the barrel bushing in the milling machine and ran the dial indicator around the top and adjusted the bushing until it was level. I then milled away everything that wasn't the indexing lug until I got close to .305" from lug to bushing front (not indexing nub). I would cut .001", bring the table all the way to one side and test fit a modified barrel and barrel jacket. When the barrel jacket would finally lock up easily I was at .300" after that I rounded the indexing nub with a file. The section that goes in the receiver is still oversized at this point and will need to get trimmed down for proper headspace, somewhere areound 4.24"-4.245".
For some reason I keep getting an invalid file message for the bushing blueprint. I know its been over 25years since drafting class but I didn't think it was that bad. I'll try again in a bit.
 
#5 · (Edited)
barrel and shroud mods

The short suomi barrel needs to be lengthened and made so it will fit the modified barrel bushing, and the barrel shroud need to be modified for the longer length of the barrel. I first modified the barrel by chucking up the barrel stub and a live center on the muzzle end. The barrel has a slight taper to it so I turned the section just forward of the barrel collar a few thousands to remove the taper in that section. Then I turned the last inch of barrel down to .585 to match my barrel extension. I then turned the chamber end down to the same size as the inside diameter of the barrel bushing (.750). I fitted a section of 3/4"x.156" tube that I had previously drilled slightly over 1' deep with a 37/64" bit which made a .584" I.D. to the muzzle end for a press fit of .001". I then welded around the joint and cleaned the weld up with the lathe. I cut the extension end so that the barrel was now 16-1/4" long. I then enlarged the indexing slot in the barrel collar to 1/4" for the larger indexing nub.
The barrel shrouds I have are the comp type. There is a little nub that looks like a muzzle in the front of the comp. I cut this nub off in the lathe and drilled/bored out the comp a couple thousands over the barrel size at the same spot. The barrel jacket now allows the longer barrel to slide through and lock into the barrel bushing. A quick note, I removed the front sight and used a center rest with the contact points running on the section that would be under the front sight so it would not leave a mark.
Here's a pic of the muzzle being turned down for the barrel extension and a unmodified barrel shroud (upper left) and a barrel shroud modified for the 16" barrel on the lower left.
 

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#7 ·
Thanks Gunco! I've actually got quite a bit more done on the build and took pictures along the way which I'll add on in the next few days. Hopefully it will make the suomi a little easier for people to build from scratch. They're a lot of fun to shoot and surprisingly accurate.
 
#8 ·
Moleman, awesome work... but I am still not getting how you cut the lugs... I feel like I am being terminally stupid... can you describe that process one more time... just not understanding how you cut the lugs and kept the lugs square and the rest was nice and round...

Mark
 
#9 ·
Mark, I didn't take any pictures while I was cutting the lugs (I didn't think it would turn out good the first time). When I order more steel I'll cut a few more barrel bushings and take a picture at each step to better illustrate how its done. The first picture shows the bushing mocked up in the milling machine. You basically cut one side of the lug then the other and repeat until all the lugs are cut out (I'll go into greater detail when I cut the next one). This will leave you with a large ridge between each lug. I cut this mostly off which left me with two smaller ridges. To remove the ridges I slid the bushing on a 3/4" rod that was mounted in a vise. I then took an air cutoff tool and while keeping the tool stationary and resting one side of the air tool wheel housing on the 3/4" rod to keep it steady, turned the bushing on the rod and ground the high peaks off between each lug. The round area in front and behind each lug is the same size. I tried to remove as little material as possible and still make it rounded. The suomi receiver sections I have appear to have been milled in a similar fashion and have a slightly reduced diameter between the lug area. When you think you've got it, color the ground areas with a sharpie marker and try to slide the bushing in a barrel jacket. any high spots will have the marker rubbed off. Just hit the high spots with the grinder again and recolor/test fit and repeat until it slides in correctly. Hope this helps, like I said I'll take more pics of the next bushing and add to this thread. Heres some mock up pics of the lugs getting cut.
 

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#11 · (Edited)
Sideplates

You can save yourself some time and buy premade sideplates, but here is how I made two sets of them for about $10. They are slightly oversized for a final fitting in the area of the rear filler and the bottem edge. You need about .040" overlap above the stock tang, trigger group, and rear filler since the receiver is round. You could in theory measure the stock tang and trigger group heigth and just make it .040" taller, but it would leave you no room for error. I first made a rough template from some thin cardboard (a pepsi box) that had a square corner and long straight top. I mounted a trigger group in a demilled stock tang and mocked up a rear filler onto the front lug of the trigger guard and rough measured it a little under 8" from the rear of the sideplate to the inside front of the rear filler. I then removed a stock tang from demill receiver by knocking out the rivets with a drift that was about 1/2 the diameter of the rivet. Hit them hard or you'll just expand the rivet more and you'll have to drill it out. Then I traced the demilled tang section on the cardboard. Once I had my rough template I cut two, 2"x9" strips from a 9"x9" section of .080" 4130 sheet steel from wicks aircraft. I squared up the two pieces and tack welded them together at the lower left end that would end up as scrap and the right edge. I traced out my template on the steel and cut the bottem profile. When I was happy with it I cut the end of the stock tang area out of the sideplates, leaving the rear filler weld to hold the two sideplates together at this point. Next I clamped the stock tang in its spot and aligned it so it was square by measuring the distance from the bottem of the little shelf right in front of the charging handle guide to the top of the sideplate (with the .040" overlap on top) and making a mark about 5" forward of this same measurement (about a half inch). Then I took a straight edge and placed it in the cocking handle shelf of the stock tang and adjusted the stock tang until the straight edge was on the mark I had made. I put another clamp on the tang and sideplates and drilled the sideplates through the 3 rear stock tang holes with a 5/32" drill bit. Then I cut the rear filler area of the sideplates off at 8" which will leave me about 1/8"+ for final fitting. I will not cut the rear filler rivet holes or trim the sideplate length until after I repair the rear filler.
 

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#12 · (Edited)
Bolt modifications part one

The bolt in the suomi kits needs to be modified from its closed bolt/fixed firing pin to a closed bolt/ hammer or striker design. I sort of followed the directions shown in the shotgun news article SGN-9. I started by cleaning the bolt and removing the felt wad (if any) in the recoil spring hole. Next before you do anything else REMOVE THE EXTRACTOR before it gets ruined in the following steps. Do this by taking a small screwdriver about the same size as the width of the extractor and put it in the extractor groove. Then slowly push the extractor away from the boltface. When you can see the pin that retains the extractor then lever the extractor forward out of its pocket and out. Then I drove out the firing pin retaining pin located about 3/4" behind the front of the bolt. I drive them out from the top as it appears they were driven in from the bottem.
The bolts as they come are too hard to machine with high speed steel cutting tools, so like in the sgn-9 article I annealed my bolt. I use the "fires of hell" brush torch from harbor freight - Harbor Freight Tools - Quality Tools at the Lowest Prices . I got mine on sale for about $25 and they have a cheaper version without an ignitor that goes for $20 on sale. Hang the bolt by a small wire and heat it until its a dull red color, then let it air cool or throw it in the grill set on high and slowly bring down the temp. Then I drill the firing pin channel from the rear with a lengthened 11/64" bit to a depth of just behind or to the firing pin retaining pin hole. Now you can drive out the firing pin from the back with a lengthened 1/8" drift. It should come out easily since when you drilled it you also releived some of the pressure holding it in.
In order to use the original bolt you also have to make it so that an unmodified bolt cannot fit inside your gun. This is usually accomplished on tube guns by reducing the bolts diameter or installing a blocking rail in an original diameter receiver and milling a matching slot in the bolt. On this build I reduced the diameter of the bolt by turning it between centers until it slid freely inside my receiver tube. If you go with the 1.5"x.188 wall tubing like I did the bolt will need to be turned down to 1.115"-1.118" as shown by the two middle bolts in the picture of the 4 bolts. IIRC the prexis bolts need to be 1.170"-1.175". If you decide to cut a slot in the bolt a great spot for the slot is where the rear sight groove is in the bolt already. If you choose this route then just mill the slot the rest of the way to the rear of the bolt. I slightly deepened the one in the photo just for good measure. I did this to the top bolt in the bolt pictures.
I will add more bolt info soon on how to slot the bolt and drill it for the firing pin.
 

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#13 · (Edited)
Bolt mods part two

In order to use the bolt with a hammer or striker system you need to cut a slot in the bolt. The slot on the top of the bolt is .390" so I shoot for this width. The slot needs to come to about .675"-.7" away from the step in the bolt, and about 1.5" from the rear of the bolt. On my first one I drilled/filed out the slot. It wasn't fun, but it was "do"able. On the bolts Ive done since then I milled the slot and squared up the front with a file.
Next I remove the full auto feed lip by either filing it off or milling it off. Then I take a small file that has no cutting grooves on one end and the front corner on that side rounded. I file the two sides of where the feed lip was until a 9mm case will just slide up into the bolt face. Then take the sharp edges off of the bolt where the feed lip was cut off.
Next I like to set the firing pin protrusion to be limited by the large step in the firing pin so it does't peen the weaker firing pin hole in the bolt face. I take a 27/64" drill bit and slowly deepen the recoil spring hole, stopping to check often how close the firing pin tip comes to the bolt face. When The firing pin tip is close to the bolt face I measure how close it is with a set of dial calipers. The firing pin needs to extend .035"-.40"above the bolt face. I don't cut it all at once, and always make sure the inside of the bolt is clean before I measure the firing pin protrusion. When you get the protrusion between .035"-.040" you're done with this step.
Next I tap the firing pin hole with a #12-28tpi tap so that .7" or less of a 1" bushing will screw into the hole when tight. If you go over this measurement you will have to drill the bushing from the rear to the .7" measurement or the firing pin will stop there and give you a false firing pin tip protrusion. The danger here is that if you don't realize it you could drill through the bolt face with the next size up drill when setting final firing pin protrusion and wreck the bolt.
You can screw in and red loctite a #12-28 screw and drill the next two steps, but a better way is to drill the bushing first. I made a simple fixture to hold a machine screw so I could drill it with a 1/16" bit half way from the front and a 7/64" bit about halfway from the rear. Then you can locktite and screw in the bushing until its tight. I then chuck the bolt up in a lathe and remove most bushing above the bolt face except for a couple thousands. I then file the bushing flat with a small flat file that I've rounded the head on.
Your firing pin will now fit in the bolt but will be below the bolt face. When the locktite has set, verify that the bushing extends no more than .7" into the bolt from the boltface. You can use a 1/16" bit to get an idea of how deep the firing pin tip is in the bolt, and how much the last step in the bushing needs to be drilled in order to get the proper firing pin tip protrusion. Now is a good time to drill the clearance in the firing pin channel for the return spring. I use the original suomi sear spring or you can use a 7/32"x1.75"x.028' wire diameter spring. drill the bolt from the rear with a 1/4" bit to a depth of about 4.95" measured to the drill bit tip. This will let you step the rod you used to lengthen you 7/64" bit to reach further into the bolt. We've already set how the max firing pin protrusion, but the larger 7/64" hole in the back of the bushing now needs to be drilled deeper from the back with a lengthened bit to reach the .035"-.040" we set the protrusion at earlier. use the same clean the bolt, measure, cut as we did to set the initial headspace. Stop and check often until you reach the correct firing pin tip protrusion.
In the next step I'll finish the bolt.
 

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#14 · (Edited)
Final bolt mods

There's not much left to do to finish the bolt. If you're going to use a section of sten gun recoil spring you just need to drill the firing pin retainer hole. On the first bolt I did, I copied the setscrew method in the sgn-9 article. I really didn't like the setscrew and even though it hasn't worked loose in about 1000 rounds I'm still concerned that it will. I have since switched to a pin on the side of the bolt like an ar15. To simplify things I made a jig to spot the retaing pin location. The center of the hole for the pin reguardless of the type you use needs to be about .350"-.360" back from the step in the bolt. If going with the setscrew just center it in the slot on the top of the bolt and tap it shallow so that the setscrew is in there tight. I made a jig out of .080" sheet steel scraps from the sideplates and a 1/4" rod. The jig fits in the extractor groove and needs to be peened/dimpled so that it fits in there snug with no wobble. The extractor groove is tapered at the end and your jig will have to not contact this area to seat correctly. I cut a step in the jig so it would locate the drill hole .350" back from the bolt step. Then I drilled a section of 1/4" rod with a 3/32" bit and squared it up and welded it to the flat stock. Double check the squareness and install the jig backwards in the bolt with a drill bit installed. Adjust the jig until the drill bit just misses the original suomi firing pin body as it is slightly larger than the part of the ar15 firing pin we're trying not to hit.
With that done, color the area where the hole needs to be in sharpie marker and flip the jig back around and make a mark with the bit to locate the holes location. The bottem or down hill side of the mark you made in the sharpie coloring is the center of the holes location as only the uphill side of the drill bit contacts the bolt. Don't try to drill the hole using the drill guide because it will wonder off center as the hole isn't a straight on cut on the round bolt, and when you break through to the inside the drill bit will break when it hits the opposite side. To prevent this I made a snug fitting removeable plug and pushed it into the firing pin recess where the retainer pin hole would be. This way the drill acts as though you're drilling a solid piece of metal. I mount up the bolt in a drill press or mill and make a plunge cut deep enough for the retainers head with a 1/4" end mill. Then I put a center drill with a 3/32" tip and drill and taper the bottem of the hole slightly. Then drill through the bolt with a 3/32" bit and remove the plug. Debur the hole and test fit the firing pin with its return spring. Use the receiver endcaps recoil spring guide to push the firing pin in enough to get the retaing pin in.
If you're using a sten recoil spring you're done. If you're using a two stage recoil spring then drill the recoil spring hole in the back of the bolt with a 17/32" or 9/16" bit to a depth of about 3-1/4" and bevel the hole slightly to remove the sharp edge. Another option for a two spring recoil setup would be to drill the bolt recoil spring out with a 1/2" bit to a depth of 1.9" then turn a tight fitting button to fit inside the recoil spring hole with a hole for the recoil spring guide rod. You will have to shorten the original recoil spring quite a bit and use a a section of a sten type spring with a rubber bumper that will limit the recoil spring guide from ever hitting the back of the firing pin.
Here's a picture of a bolt with a retainer screw and one with the ar15 type retainer. The jig pictures show the profile and proper firing pin clearance. I've also included a picture of the plug for drilling the retainer hole and a 3/8" tapered shaft I used to center the drills bit on the location mark.
 

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#16 ·
Trigger group

There are several options for the trigger group such as ar15, m1 garand and carbine, striker fired, and my favorite the remington sear and hammer. One consideration with converting any trigger system to fit the suomi is the width of the narrow suomi triggerguard. The remington 870, 1100, 11-87, 11-48, 11-58, 742, 7600, 7400, 552 ect... use a very narrow hammer and sear. I used an 870 on my first suomi build and I believe this is a 742 trigger guard that I'm using for this build. It could be for any of the rifles I suppose, but it was incomplete when I bought it. You really only need the hammer, hammer spring, and sear out of the remington trigger group. The rest will not be used in the build.
Here is a picture of a completed trigger group using 870 parts, an unmodified suomi trigger guard, the donor remington trigger group, and a block of steel milled to 1.206" tall, approx 4-1/4" long and .315" thick. I will be cutting the new hammer and sear mounting blocks from this steel block.
 

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#17 ·
wow, please keep posting details. this will help me IMMENSLY when i get around to building my SUOMI M31's
can i legally keep the shorter barrel, but extend the barrel shroud?
im cheap and dont want to buy another barrel. i will probably do one of my kits as a SBR and not have to wory about 922R or the barrel issue...
 
#18 ·
I just lengthened the barrel with a section of heavy walled 3/4" tubing and welded it on. I think you would want to get an actual letter from the baft as to whether or not you could just lengthen the shroud. My gut feeling on it would be no, as the barrel is still too short and you could replace the shroud with a normal length one at any time. I think you'd have to weld the lengthened shroud to the barrel and receiver for it to even be considered though.
 
#21 ·
The suomi barrels as they come are a hair over 12-1/4" long. With the compensated shroud you're at 14-1/2". So in that respect you're only adding 1-3/4" to the overall length of a suomi by making the barrel 16-1/4" long. The ant eater look sucks, but its not as bad with the longer comped shroud. Eventually I want to lengthen a shroud another 1-3/4" so the barrel only sticks out the 3/8" or so as the barrel looking nub on the end of the comped shroud does.
 
#25 ·
Makes those $599.00 prebuilt Suomi's look more attractive.
If you have to buy all the SA parts you are better off buying a built gun, it's only a few $$ difference.
A friend just got one from CFS, I'm going to check it out tomorrow, I'm going to try and have him field strip it and take some pics.
 
#26 ·
Yeah, you pretty much need a lathe and a mill to complete this receiver from tubing. You can make due with out the mill, but the lathe is a must have. The sa 80% receivers and sa bolts look very nice, but bring the price of the build up fast.
 
#28 ·
I'm bringing this over from the M11 M10 Builds thread, don't want to hijack his thread.
Your ppsh41 looks nice. The only real problem I've had with the suomi is not trimming the ejector enough. The cases were ejecting too soon and I've had to trim the section just forward of the step that kicks out the shells, but a little touch up with the dremmel fixed that. I built the first one without the aid of a milling machine and although it took a lot longer but was still "do"able. I want to blue this next one and have everything except the steel tanks to do it. Thanks for the kind words on the writeup. I've only seen a few writeups where people have built them from either rewelding or a prexis tube. I'm hoping to give people a cheaper alternative so that more people will start building them as they're neat guns. Of course the downside is you need a lathe or access to one and a milling machine is nice also.
And this also fits
Yeah, you pretty much need a lathe and a mill to complete this receiver from tubing. You can make due with out the mill, but the lathe is a must have. The sa 80% receivers and sa bolts look very nice, but bring the price of the build up fast.
Thank you on the compliment about the PPSH41, it's not a top quality build but it looks decent and functions. I worry more about function then finish, I'd rather play with a build for a little before worrying about how it looks. :D

Yes I agree a lathe is a must and a small mill would be very helpful. I was going to go with an 80% blank and some of the other semi stuff for a few builds but after watching the SG9 build I realized I'd save money buying the equiptment, minimum tooling and raw tubing to do it myself. And after I'm done I can always sell the tools if I don't find another use, yeah right there's always something new to make.
I got a SUOMI, a PPS43 or two, STEN(s), Yugo M56, CZ26 and a pistol caliber AK (most likely 9mm) I want to do yet. Also got a DP28 but I know I'll need pro help with that.


So keep posting the great info and pics, I'm sure there's quite a few people your helping that don't even reply.
 
#29 ·
After what Coils wrote, I sort of feel like I have to jump in here.

If you plan to build more than one or two guns, or something more involved than assembling an AK or AR, then I would say that I would get the small mill first, but in reality you'd want both.

You can do a lot with a little time, ingenuity, and thought. You can do it much faster with a lathe or a mill. The question is how serious are you about building vs buying. Don't build to save money, by the time you purchase all the tools, tooling, and consumables you'll be dollars ahead buying guns, unless you complete all your builds with a dremel tool and a HF scratch start TIG.

I am not trying to discourage anyone from building, lots of great benefits of BIY. One of which is knowing your weapon intimately and not having to guess if someone else did the job right, another is the ability to brag about your build, and finally to build uncommon weapons that have a true collectors feel. How many of your friends have AK's and AR's? They all do, they have Glocks too. How original, but when you go to the range and bust out your semi-only PPSh-41 and TTC, people stop and stare... they want to know all about the cool guns you have and where they can get them.

Coils is right, the right tools make the job much easier.

Mark
 
#31 · (Edited)
Trigger group part #2

Since I'm using a remington hammer and sear in my build I will need to make some blocks to hold the sear, hammer and hammer spring + plunger in position. I started with my solid block and rough cut out the two blocks as shown in the drawing. They are on 1/4" scale paper (I traced them and cleaned them up a bit). The new remington trigger groups are made of plastic so I used mild steel for these blocks which seems to hold up just fine. The front block has a lowered and smaller lug to prevent the insertion of an unmodified trigger group in the finished build. This pattern is for the 870 hammer and sear, which will work, but will require some fitting for the slightly different 742 hammer and sear for this build. Lastly is a picture of how the fire control system will be layed out. The completed set of blocks I hacksawed/filed out, and the profiled ones I milled.
 

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#34 ·
barrel latch repair

The original suomi barrel latch which was riveted into the front filler had its rivet removed as a part of the demil. In order to install the latch you'll need to reconstruct either the rivet or tap it for a machine screw. I chose to just use a machine screw as no matter how hard I try its still not going to be a real suomi. If you want to turn this style fix into a rivetted in latch later you can, but more on that later. I started by making a jig to hold the latch out of 1-1/4" aluminum rod and bored a tight fitting hole in the center so that I had to press in the latch stem. I also put a setscrew to hold the latch stem as some of my more worn stems were several thousands under what the newish looking one was. I then turned off the old rivet and drilled a hole with a #25 drill bit in its place just shy of the spring in the latch handle. Then I tapped the hole with a 10-24 tap. Here's a picture of from left to right a demilled latch, a latch with the "rivet" turned off, and a completed latch threaded for a 10-24 button head screw. When removing the old rivet try not to remove any material from the step in the latch stem as it sets the distance so that the latch doesn't rub on the front filler. I even left a few thousands of the old rivet to make sure I wouldn't alter that surface. This can be done with files and a drill if you're careful. If you want to rivet the latch back in place just thread a section of rod that is the same size as the inside diameter of the rivet washer. Leave enough of the rod sticking up to form a rivet and red loctite it in.
 

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#36 ·
Thanks, I haven't had much time to work on it the past month because of family comittments. I also broke the 1/8" end mill I was using on the barrel bushing and need to order another one before I can continue.
 
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