View Full Version : SGN-22 article
04-21-2009, 01:55 PM
I couldn't find a thread specifically on the sgn-22 so I thought I'd start one. The sgn-22 is a single shot self ejecting design that I belive can be easily adapted to semiauto with a few changes. The bolt design my help those of us that want to make their own 22lr, 22mag, or 17hmr semiauto. While I don't think I'll make a sgn-22, I do think I may try making a 17hmr bolt for use in a standard ar15 upper with a 17hmr barrel using savage mags with an adaptor.
The first article basically listed the concept and showed the receiver construction which is basically a tube with a ejection port with a 10-22 barrel turned down to fit. Part two shows more of the bolt design which uses a modified ar15 firing pin and an ar15 type plunger ejector. It looks promising so far.
04-24-2009, 08:42 PM
In part two, Matthews describes how to build the bolt. As I looked at the pics, I noticed that he has a recessed bolt face resulting in what appears to be feed lips. You might want to modify the bolt face to make it legal for a semi auto.
04-24-2009, 09:50 PM
If you were making a semi gun and going to keep the ejector pin then you would also have to keep the recessed bolt face and once cut to take a magazine the feed lips would have to stay there. The atf does take a dim view of tube guns with feed lips, but there are guns out there where it is acceptable. I read once that if the original gun had a fixed firing pin then the semi version had to have the feed lips removed. I don't know if thats true of not but it may have some merit. If you modify a suomi or sten bolt to semi then the feed lips need to be removed. There is a new made semi sten bolt that is baft approved and has the feed lips. Its really not needed for the most part except for designs like the sgn-22 that use a spring loaded ejector to eject the spent case. I think the only real way to get an answer of its legality is to write into the atf and ask them a specific question on a specific bolt design. Since there are easier designs out there to make that don't have a feed lip or ejector pin which might get you in trouble I agree with you and would stay from his design. That was the "can be easily adapted to semiauto with a few changes" I spoke of earlier. I think the design would be much easier to make if it used a fixed ejector and had a bolt face similar to a ruger MKII shown below. If I was going to make the bolt as he did I probably would make it in 2 parts. The front part could be the actual bolt with the last 1/2" of it reduced and threaded for a like sized pipe to be screwed on or welded with cut outs for the hammer and the same 1/2" of it a solid ring where it connects to the bolt head.
04-26-2009, 04:30 PM
I agree, a fixed ejector is the way to go. I must admit that I am kind of taken with the simplicity of the SGN22 and am considering building one, although I am not too keen on the feed lip bolt. I'm thinking that if you cut a slot in place of the ejector tunnel on his bolt, you could user a fixed ejector and eliminate the feed lip.
Of course then you would have to rework the firing pin return spring, but that shouldn't be to hard. I would probably use a Galil barrel and reline it as Sarco has them fro $2.00 each with bad bores.
You might be on to something with the multi part bolt.
04-26-2009, 05:17 PM
Of course then you would have to rework the firing pin return spring, but that shouldn't be to hard.
You might be on to something with the multi part bolt.
I'll admit I haven't sat down and drawn out the bolt yet, but if I went with his design for the firing pin and spring with a slot for the ejector why would I have to rework the firing pin return spring? I should be able to cut a slot in the bolt at least as deep as the plunger hole that he uses on the sgn-22 bolt with out cutting into the firing pin channel. I could just be all nyquilled up though! I thought it might be a lot easier and slightly cheaper to machine the bolt if it was a two piece. You wouldn't have to file the front of the cocking slot and use long extended drill bits, and if you messed up a front section you wouldn't waste as much of the good bar stock.
04-28-2009, 07:37 PM
I was thinking that the firing pin return would need to be reworked if I went with a fixed ejector because he used the same spring for the ejector plunger and the firing pin return, I hadn't thought about using the back of the fixed ejector as a spring keeper. Great Idea!!. The more I think about it, the more I like your multi part bolt. You could probably get away with mild DOM tubing for the back section.
04-28-2009, 08:51 PM
See I was all nyquiled up! I'm going to go with a coil spring around the firing pin like I did on my suomi build. Its a simple coil spring .225" od, .168-9" id, 1.65" long .028" diameter wire. Since I'm building this for an ar15 I'll have to shorten the spring and just make a new firing pin probably the same length/style as my m261 22lr adaptor kit uses. You lost me on the "fixed ejector as a spring keeper" thing. If I get some time later on I'll put up some pictures of the m261 firing pin.
04-29-2009, 01:01 AM
Here's the bolt face and firing pin of the M261 22lr adaptor for the ar15/m16. Since the chamber insert brings the bolt back about .3" the firing pin is that much shorter than a regular ar15 pin. If I make a 22mag or 17hmr upper for my ar15 then I will use the same length firing pin as the M261 depending on how I run my magwell adaptor and how far back my barrel is in the receiver. The diameter of the bolt is .990".
05-01-2009, 01:06 PM
The Galil barrels came today. They were definitely rusty, but the bores cleaned right up and are nice and shiny! I sandblasted the the outside to clean them up. I think they will work nicely after I turn the barrel threads off.
I'm thinking I can just reline the .223 chamber with a short piece of .22 rimfire liner, cut a .22LR chamber and use the original chromed rifling. This will eliminate the need to deep drill the barrel.
I will try and post some pics
05-01-2009, 02:50 PM
That sounds interesting. For $2 thats a great find. I shoot 22lr in an ar15 (a lot more lately) and the larger .224" bore and long throat still provide acceptable accuracy for plinking.
05-01-2009, 08:29 PM
I bought several barrels just in case I screw one (or more) up during the build. I should have some more time tomorrow afternoon to have a go with rechambering. I will try to post some pics.
05-03-2009, 06:43 AM
Here are some pics of the barrels before and after cleaning up
05-03-2009, 06:54 AM
I turned the threads off and bored the chamber out with a 13/32" drill bit 2" deep. I then lined it with a short section of .22 rimfire liner. I still need to cut a new chamber and an extractor slot and weld the gas port shut and the barrel will be finished
05-03-2009, 07:57 PM
Looks good, I'm going to have to order some steel for the bolt soon or just make one out of mild steel for practice.
05-05-2009, 06:59 PM
I've got an Amish machine shop close by for plain old mild steel, but for decent 4130 I have to go online to get it.
05-07-2009, 09:03 PM
05-08-2009, 06:25 PM
Thanks, I'm hoping to get some more time this weekend to work on it some more. Between work and helping the kids with school projects and now yard work, time gets almost as tight as money.
Moleman, do you see any leading at the beginning of the rifleing with the long chamber throat and oversize bore on your AR?
05-08-2009, 08:30 PM
A little, but only if I shoot a lot. I have ar barrels in 1 turn in 7",8", 9", 12", 14". I was mostly shooting it in the 1-14" twist barrel (that I thought was a 1-9" until I shot 62gr ammo in it) and a 1-9" barrel. When I get more time I'll see if the adaptor is more accurate with the slower twist rate rifling. Where I get the most fouling is in the neck area of the chamber where the insert ends. I clean the chamber after every time I use the adaptor because the only time I didn't the 5.56 case rim ripped mostly off and the extractor pivot pin bent. Your barrel shouldn't have that problem since you're not switching back and forth between 22lr and 223. The fouling I do get is light and comes out in a couple passes of the bore brush.
05-10-2009, 03:32 PM
Ive got all the articals so far and I keep thinking that the ejector pin will fork for a singel shot but a semi auto it wount work that long. I think the spring would fail or cause FTE. what Im getting out of his build is the bolt is closr to a AR type of bolt. and this got me thinking that I could pattern this after an AR upper using a slot in the side for a fixed ejector. what do you think so far? muttman
05-10-2009, 04:01 PM
I'm also going with the fixed ejector only comming up from the bottem. I think I'm going to use a spare A2 upper I have and make the ejector be part of the magwell adaptor, perhaps even spring loaded a little bit so that it's always up against the bolt even if there's a little slop in the fit of the magwell adaptor. I thought about comming in from the side with the ejector, but I've seen pistol cal magwell adaptors for the ar15 that use an ejector mounted to it.
05-10-2009, 07:13 PM
ejector from the botom. I dint think there was the space to, but then I dont have a AR just a how to biy a lower. muttman
05-10-2009, 07:29 PM
Muttman, I'm just going to make mine an upper for an ar15 in either 22mag or 17hmr. Here is the picture of the magwell adaptor I spoke of. It has an ejector comming up from behind where the 9mm mag would be. I figure I'd make the same thing only to fit savage 22magnum magazines. C PRODUCTS AR 15 9mm magwell block AR15 : for AR-15 at GunBroker.com (http://www.gunbroker.com/Auction/ViewItem.asp?Item=128817790)
05-11-2009, 10:32 AM
well that solves one of my problems, the other is saving some $$$ for a barrel. muttman
05-11-2009, 06:51 PM
The third article comes out next week right? I'm wondering how he's feeding the .22lr. Do you think he is chambering them with his thumb and then closing the bolt? I can't figure out how to get the shell up a ramp with that bolt.
I got my barrel almost finished, I am going to wait until I weld it in the receiver to Acraglass in the chamber liner.
05-15-2009, 01:34 PM
I've re-read the first two articles several times and I don't really understand how the bolt works. As I understand it, on a blow-back bolt the pressure pushes the bolt back (usually against a spring) and the spring controls the distance the bolt is allowed to travel. I'm not seeing any spring behind the bolt, so is this build relying solely on the mass of the bolt and it travels back until the bolt handle hits the end of it's slot in the receiver? Another question - it seems that since there is no way to lock the bolt in the forward position, the ejector would tend to hold it back slightly from the chamber - how does that get resolved?
These questions might be addressed in the next issue, and maybe for this build are unimportant. I'd just like to understand how the design works in order to transfer the knowledge to other potential projects.
I've given some thought to how I would approach some of the aspects of this rifle. I'm thinking that the two-piece bolt suggested earlier would really simplify its construction and I will probably have some questions on that later. I'm also toying with the idea of putting a AR-15 collapsible stock on it - adds a lot to the build cost, but I think it would be more aesthetically pleasing. Just have to make sure it meets the BATF requirements in the fully collapsed position.
Thanks for your thoughts and insights. I don't post much but I do get a lot of good info here.