Gunco Forums banner

Home Made Carbine Questions.

4K views 29 replies 11 participants last post by  Robert_Redbeard 
#1 ·
I am in the middle of drawing a prototype of what I call the AT-9.

It will be a 9mm carbine with a blowback semiauto configuration.

I need to know what legally has to be featured to make it okay to have a buttstock.

As in what overall length it must be and what barrel length has to be to not be considered an SBR.

Also, do you think a lcking type bolt would be a must for it to work in .45?

Because I am thinking of designing it in .45 instead so I can use the M1911 magazine to build it. I wanna use an existing magazine and I love the .45.
 
#2 · (Edited)
To avoid building an SBR it must have a bbl length of at least 16" and an overall length over 26" with the buttstock extended (if folding). Some states, notably Michigan, have their own regs regarding folding stocks and such.

Heavy enough bolt and recoil spring will make .45 work fine in blowback. All the subguns chambered in .45 have been blowback with the notable exception of the first Tommy guns. Even those were eventually converted to blowback operation with the M1 model.
 
#3 ·
It just has to have a barrel over 16 inches measured by putting a wood dowel down the bore with the bolt closed. OAL is 26". As far as I know the .45 doesnt have enough umph to operate with a gas system or at least very few examples exist because of practicality. Keep us posted on how its going.
 
#4 ·
I was thinking of using a 1911 recoil spring.

Would the bolt need to be heavier for a long barrel like that? You want the bullet to get out the barrel before the bolt chambers another round right? This is my biggest worry. Not having the bolt and barrel length knowledge.

I will of course do some more research befroe I get that far into design. I only have some basic design thoguhts right now.
 
#5 ·
As long as it wasn't a squib load, the bullet should be out of the barrel before the bolt starts moving backwards.

For some numbers, a Thompson bolt weighs just over a pound and a M3 Grease Gun bolt weighs 2 pounds. Both use fairly light recoil springs. I have a Mech-Tech CCU with a 1911 lower that also uses a 2 pound bolt and a 16" barrel. You can play with spring rates and buffers to come up with a system that doesn't batter itself to pieces.

p.s. If you're going with a .45 I'd suggest picking a higher capacity mag than the 1911 mag. That's my chief gripe with the CCU, it'd be a lot more fun at the range if it used Thompson or Grease Gun mags.
 
#6 ·
Tailgunner said:
As long as it wasn't a squib load, the bullet should be out of the barrel before the bolt starts moving backwards.

For some numbers, a Thompson bolt weighs just over a pound and a M3 Grease Gun bolt weighs 2 pounds. Both use fairly light recoil springs. I have a Mech-Tech CCU with a 1911 lower that also uses a 2 pound bolt and a 16" barrel. You can play with spring rates and buffers to come up with a system that doesn't batter itself to pieces.

p.s. If you're going with a .45 I'd suggest picking a higher capacity mag than the 1911 mag. That's my chief gripe with the CCU, it'd be a lot more fun at the range if it used Thompson or Grease Gun mags.
I was thinking a 1911 drum or extended mag. MAin thing being that it matches the mags one can use in a 1911.
 
#7 ·
Are you planing on basing it on the Feather AT-9? If so, I too have been considering building a carbine based off it. When I say based off it, I basically want to copy it. The tube receiver would be fairly easy to make. I think the hardest part would of course be the bolt. For a FCG you could just use one from an AR, ak, sks...etc...I've always thought adapting the 10/22 fcg to another rifle would be cool since you could just drop it in. Anyway, keep us posted, get your ass to work, and take lots of pics of the process.
 
#8 ·
I am just calling it an AT-9. It will be tube based of course but I am not really copying anything.

I am borrowing from some guns for ideas. Mostly from Bill Holmes, P.A Luty and some ideas I got from working on a friend's AK. Might use AK pivot pinsand retain them with snap rings.

The bolt is the only part I am really having a brain fart on. I have some ideas and have drawn up one of them. FCG will look like an open bolt FCG but I have figured a way to make it work closed. Another thing I learned from Bill Holmes' books.
 
#10 ·
kernelkrink said:
What equipment do you have? Lathe and/or Mill? That will determine some of your design right there.
One of my initial design requirements is design simplicity and being able to use the least amount of specialty equipment. You know, files, hacksaw blades, drill press, hammers, measuring tools and knowledge.

We may be getting a 3 in 1 machine after taxes come in. Maybe.

But I don't want those things to be essential. They will just make it easier and better quality.
 
#11 ·
BTW Tailgunner, how do you like your Mech-Tech CCU? Curious about accuracy/reliability (standard mags vs. extended ones), etc. I have been thinking about one of those for a while and never knew anyone that had one.
 
#13 ·
Rocster said:
BTW Tailgunner, how do you like your Mech-Tech CCU? Curious about accuracy/reliability (standard mags vs. extended ones), etc. I have been thinking about one of those for a while and never knew anyone that had one.

It's fairly accurate, but not as accurate as my Thompson replica. The Thompson has a longer sight radius and better iron sights. (assuming the rear one hasn't fallen off again) As the assembled CCU weighs half what the Thompson does it's a whole lot easier to hold on target though and carry around. It's MUCH more reliable than the Thompson, excepting the extended mag it hasn't hiccupped yet where my Thompson averages 2 to 3 jams per mag's worth of ammo. It's worth noting I'm a plinker and I buy and shoot bulk FMJ ball ammo through these, I don't know how well the CCU would feed hollowpoints.

If ya really want one I'd cut you a deal on my CCU, as I said I'm a plinker and I'd rather scratch build a .45 carbine that takes 30 round Grease Gun mags.
 
#14 ·
Robert_Redbeard said:
One of my initial design requirements is design simplicity and being able to use the least amount of specialty equipment. You know, files, hacksaw blades, drill press, hammers, measuring tools and knowledge.

We may be getting a 3 in 1 machine after taxes come in. Maybe.

But I don't want those things to be essential. They will just make it easier and better quality.

The lack of machine tools limits your options. You could always use an existing bolt, but if you are going to build one yourself a stepped diameter design is probably the easiest. Could be made from stock sized round bar.

The rear section is sized to fit the ID of the tube and the front section is just larger than the casehead. The rear section would be drilled to take the front section, which could be welded, pinned, or silver soldered in place. A center cutting end mill of the proper diameter could be used in your drill press to make the breechface, simple bent spring steel extractor screwed into the side.

You could also copy the Greasegun bolt mechanism in that it rides on two rods instead of the tube ID, would allow more flexibility on bolt size selection.

Probably the easiest firing method would be a striker assembly, but you could also slot the rear of the bolt to accept a hammer mechanism.
 
#15 ·
It is really nice to know I am not to far off of other people's ideas.

I was thinking of using a P.A. LUTY style bolt. But modifying it into a closed bolt. And pressing the bolt into a solid block instead of putting locking collars around it.

Like you said, I was thinging of using a striker and not a hammer. Kinda like I have seen in Hi-Point pistols. But a design of my own. Of course.

How do I figure out how much the metal I am going to use will weigh? So I have some clue as to how long the bolt will need to be.

I have been working on some drawings. I will post some as they become clearer. I don't wanna post something Unless I think people will get what I am drawing.
 
#17 ·
Ah, I assumed a round tube receiver, but the concept is basically the same. As for weight, I would build the rear section long and cut to match your ideal bolt weight. I would definitely make the rear section of the bolt hit a positive stop on the bbl mount, otherwise the breechface might go slammimg into the bbl when dropped on an empty chamber.
 
#18 ·
Robert_Redbeard said:
I was thinking of using a 1911 recoil spring.

Would the bolt need to be heavier for a long barrel like that? You want the bullet to get out the barrel before the bolt chambers another round right?

The barrel length doesn't matter, I'm guessing the wieght of the bolt would deside on the spring pressure.
I got a 1911 and just for the hell of it I got a 16" barrel and a folding stock for it, I didn't change the recoil spring and it cycles fine.
 
#19 ·
Here is the initial idea for the bolt carrier. I haven't figured out just how I am going to do the charging handle. So no hole for that so far.

And I haven't figured out how I am going to design it for field stripping yet so no notches for that either.
 

Attachments

#20 ·
Feather USA made a .45 cal. carbine, if your thinking of using a tube receiver, maybe utilize one of their .45 bolts. It also uses a dual recoil spring system which keeps it in line with the trigger group and using two springs helps return power and uses less recoil space. Just my 2 cents though. Good luck and lets see some pics during the build!
 
#21 ·
tony said:
Feather USA made a .45 cal. carbine, if your thinking of using a tube receiver, maybe utilize one of their .45 bolts. It also uses a dual recoil spring system which keeps it in line with the trigger group and using two springs helps return power and uses less recoil space. Just my 2 cents though. Good luck and lets see some pics during the build!
The firing plunger wil have a spring as well as the bolt return. One inside teh other kinda like one of the Bill Holmes gunns from his books.

I have all of his books that I could find. The Prototype Firearms book is a jewel. That's where I got the idea for my firingpin plunger. I haven't drawn it up yet.

The Bolt Head that fits into the carrier will be a 1/2 inch spring pin with a hollowed out steel rod silver soldered inside it. Kinda like the Bolt face of the P.A. Luty 9MM.

I think I will stick with 9MM to start. I just don't know what kinda mag I can get for .45 cal that is big enough.
 
#25 ·
I have to agree, if you want to do one in .45 go with the Thompson mags.

A 1911 mag is .545" from left to right, 1.370" from front to back and about 5" tall (that's a 7 rounder).

If you want to do a 9mm get some STEN mags, I see these on sale for $4 each. You'd have to find or make a mag well.
 
#26 ·
Thanks.

I was thinking of buying a 1911 drum. I have seen them some place before. That way in a pinch I could still use a regular 1911 mag from the pistol I wish to build too.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top