Ultralight Folding 9mm Pack Rifle Begins

Couple of questions if you please.
Curious as to your choice for the Beretta magazines ?

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Because I have lots of them. But if you read back a little, I changed my design to use Diamondback DB9FS mags as the primary and detailed the reason

Why have the barrel fold up as opposed to just having the hand guard and barrel remove like on the just right carbine ?

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Because take down pack/survival rifles are stupid if the design can be made to fold neatly. Then you have two separate pieces rattling around in your pack that you need to isolate from each other as well as everything else, and assembly is slower, requires fine motor operations. My design you just unfold, The latch is automatic, no thumb screws or other nonsense to mess with. It's as quick as drawing a handgun; you could walk around with the thing folded for compactness, waiting to lock it into firing position until you see the critter you want to shoot.

I assume the handguard will have to be removed before the barrel will fold up, will it lock into place in the up position for transportation ?

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Negative. Look at my .22 Ultralight thread linked in an earlier post. This will function in exactly the same way.

As an aside, I HATE the new forum format. I'm gonna take a few days off and check back to see if it's palatable once things are ironed out. I've been here for a long time, but this new system is so irritating to look at and use that I may be calling it quits with THR.

Lots of progress the last few days, just still having a real hard time dealing with the new THR format. Test theme is better, but not great.

Anyway, still have a few parts to make, and lots of hand finishing to do, but it's moving along:

The_Next_Generation said:

Are you going to add a simple buttplate to the end of the receiver extension to act as a stock?

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Yeah, just like the .22 pack rifle

What if you made the stock fold as well? Maybe that wouldn't be very advantageous, since the barrel folded rearward means the shortest the entire package will get is 16.6" anyways. But maybe the folding stock would still be worth it somehow.

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Well, I do intend to SBR this one, and if I do, yes, a right hand folding stock is what I'd like to do. Whole package would come in around 10" x 3.5" x 7.5" when folded. But I first need to get it operational, and if my bolt proves too light, I will have only two options. 1, bore out most of the bolt and replace the removed steel with a piece of (extremely expensive) tungsten alloy. 2, a hollow rod through the back of the receiver and a buffer and recoil spring in the stock tube. #2 is definitely more cost effective, but would pretty much eliminate the possibility of a side folding stock without some really trick parts that add a lot of weight and complexity.

But it may work just fine with the light (12.7 ounce) bolt. That's about half the recommended weight of a 9mm blowback bolt, but that doesn't mean it won't work. High bolt velocity can be offset with a stronger recoil spring and a rubber bumper, as long as it keeps the bolt closed long enough to prevent case head rupture. My .22 pack rifle bolt is also very light at 5.1 ounces, but it functions fine, even with hyper velocity ammo.

"When guns are banned, people like MachIVshooter will still be able to make them."

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Yes. But so can any of you! True, the builds I do require expensive precision equipment and machining experience, but there are plenty of ways to build without that. It may not come out as light weight or pretty as what you can do in a machine shop with aerospace materials, but can still be plenty functional, from the simplest slam fire guns to open bolt, pipe-based SMGs (if they're all banned anyway, why worry about NFA, right?).

Ammo is the bigger issue, but there are ways around that, too, albeit pretty risky to do in the kitchen or garage.

It has now been test fired, and we have established that a 12 ounce bolt is heavy enough to keep the breech closed . Bolt velocity is high (~27 FPS), but that can be mitigated with strong recoil springs and bumpers, like the 1/4" UHMWPE piece I machined to fit the back of the receiver bore.

I haven't done the ejector yet, so it's a fancy single shot at the moment, but I have fired over 20 rounds with no signs of case head bulging whatsoever. I wasn't sure I could get away with a bolt less than half the recommended weight, but now that I know it works, I'm free to finish up the rifle! All that's left is ejector, bolt catch (undecided if I'm doing that or not), rear sight and butt plate, and then lots of hand finishing to take out tool marks.

Curious as the final weight if you will. Under 5 lbs ?

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Way under. This is with everything but the ejector, safety lever, rear sight and mechanism for keeping the barrel in the folded position, all of which will probably come in under 2 ounces combined:



That's 55.4 ounces (3.46 lbs) if you can't see it well.

MachIV, how do you come up with the bolt velocity figure?

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Mark Serbu calculated that one. I had asked him what his thoughts were on running a bolt this light. I don't know that any production gun ever has. The Marlin Camp 9 bolt is light, but I don't think it's that light. Not gonna lie, was fairly concerned about case head failures, and actually remote fired this one the first time.

The Derek's Tweaks style has a touch more contrast if you'd like to try it. It's subtle, but more usable IMHO.

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I like that better! That contrast makes it easier to read, easier on the eyes, easier to distinguish between posts. And I much prefer the black font in the reply box.

Derek Zeanah said:

I absolutely love what you're doing with this.

Well, I hope uploading images is better at least.

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Haven't tried, actually. I use Photobucket for all photos, because I share in more than one place.