KPV, Anyone?

Lord knows how, but apparently someone managed to get a demilled parts kit over here . From what I gather, it's a gigantic short-recoil operated belt fed that uses a rotating bolt, which sounds like a fairly unique operating system (I thought the various WWII recoil operated MG42's/etc. were long recoil, and none were rotating bolt). Not that I would, but I think it'd be cool to try a 50cal conversion to a box/hopper fed semi-auto 'anti tank rifle' (which technically puts it beyond the purview of this forum, but whatever ).

Anyone here ever see one of these at an OFAST or Knob Creek, or better yet, have a chance to shoot one? Are they soft shooters in 14.5mm?


Doesn't look that big...I'll bet I can make it fit in the trunk if I fold the seats down

TCB

Anyone?

Well, we're doing this . Seller came down a bunch on his price, so I couldn't refuse. So now I get to figure out what to do with 110 lbs of awesome. I'm still not sure whether to rebuild this as it was (and find a towed ZPU mount) or turn it into a stripped down shoulder fired "tank rifle" like the L39, PTRS, or S18/100 (last one is the coolest). The barrel is demilled at the chamber, so I most likely cannot reuse it. That means 14.5 is probably out, but I might be able to use a take off 20 mm (for a DD build) or 50cal for something cheaper and more available.

TCB

I would appreciate that greatly! I found a section view schematic from such a manual, but that's it so far. Not much documentation out there.

TCB

I'm reviving this one since the weight training equipment (KPV parts) came in the other day. The condition is pretty (okay, very) rough, but I think I have nearly everything needed to attempt a reconstruction. The torch cuts are in very advantageous locations, and should present little problem. The terrible, awful, Titanic-like rust pitting internally is pretty much limited to an easily fabricated tubular section of the receiver; a splice should be fairly easy to do if drain pipe is the right alloy . Even the barrel is demilled in a way that can probably be overcome. The bolt is pretty hard up, but I think it can be salvaged or replaced if needed.

The coolest part came when I was able to get the bolt (hammered) out of the receiver tube and disassembled; the firing pin setup lends itself to a straight-forward closed-bolt (i.e. legal semi-auto) configuration with a little modification. Since I have no mount or fire control group for the weapon (it's basically a chopped-up barreled action) I am very tempted to get creative with the reconstruction. It's not like a rewelded thing with no providence is historically significant or anything, so tweaking the layout some is certainly an option.

My thought is to add a large padded stock to the rear, a grip/bipod fire control group unit on the underside, scope mounting provisions, and a tripod at the barrel/shroud root or receiver nose, for a Soloturn S18/100 lookalike, only bigger and awesomer and belt-fed*. The tubular receiver body and extremely long top cover lend themselves well to the look. I suspect that a tunable muzzle brake of some sort will be a requisite here, since I'll bet a mounted field gun operates quite a lot harsher than you'd ever want a shoulder-fired weapon to do (for reliable full auto function). The design is a recoil-operated gas assisted action, so perhaps the gas assist can be dialed back a bit to make things easier on the ol' collar bone (or a brake incorporated into the stationary expansion chamber to reduce net recoil, but not operating energy)



I had planned to hog out the barrel and reline it in 50cal so as to avoid expensive-er bullets and a tax stamp while also reactivating it, but this barrel actually looks reparable, so I'm loathe to cut on something so rare and valuable (5k$ for an intact KPV barrel, apparently ). Keeping things 14.5 does at least simplify some aspects of the built, and it's not like I'd realistically be shooting this thing enough to bankrupt myself on ammo, even at 40$ a pop (or rather, Earth-shattering boom ). At least it's not so much larger than 50cal that it can't be loaded on the same presses (I think).

I have to say the design of this thing is brilliant.
-Every single operational part in the top cover that drives the belt is reversible, so the belt can be run either direction with some quick armory work
-Both halves of the feed tray are the same casting, and are also symmetrical so they can flip over
-The bolt lockup is a sight to behold; dozens upon dozens of interrupted thread teeth, engaged with about 10deg of rotation
-Bolt rides on 8 rollers leaving ample clearance for debris and reducing wear/friction. Bolt is guided by large crosspins following receiver slots
-Bolt rotation is incredibly simple; rotated into battery by the bolt tail telescoping down on it, unlocked by ramped cuts on the receiver slots. This means the design has a lot of slop built into everything but the bolt/barrel lug interface (sort of like an AR, where the bolt/barrel nut interface is the only truly critical dimension for proper lockup)
-That 5ft barrel is quick-changeable, as far as a 5ft barrel can be, via a BREN-like locking collar that clamps both barrel and shroud, allowing the shroud to act as a sort of insulator if needed
-The gun appears to be entirely serviceable without tools (as in every moving part can be accessed if not removed without armorer help), and in issued condition, I suspect without the need for hammers

Gonna have a lot of fun messing around on this build, I think. This'll probably be the one I finally learn how to weld on (because there's so much metal, I don't have to worry about screwing up and not being able to fix my mistake )

For the photos, keep in mind the scale;
-Receiver is about 6" external diameter
-Barrel is about 5ft long, receiver 4ft long (8ft total or so)
-Barrel/shroud are around 40lbs, +100lbs total
-Each half of the bolt body is about the size of a fist

TCB

*probably short belts, though. They're sold by the 10-strip, apparently.

If anybody can read Russian, please let me know; there are a few specific operations (namely removing the barrel) that I'd like to verify from the manual. I think the barrel should just slide out once the locking collar is rotated (meaning that wailing on the locking collar and severed barrel stump with a 3lb hammer is the correct thing to do to get them unstuck ), but it seems even more firmly affixed than the welded on (literally and by rust-erosion) bolt body. I wants to make sure there's nothing else in the way that needs to move first

Downsides of being an illiterate peasant, I know

TCB

Looks like I just scored a complete bolt assembly, so hurray 'more parts I won't have to restore and/or fabricate' and his friend, crippling debt ()

The bolt I have is seriously nasty, well the bolt head at least; check out the erosion on the near side collar. But I can't exactly buy just a bolt head (that'd be too easy). The tube is even nastier, but it's far less critical to function, and can be more easily fabricated (it's basically a piece of drain pipe with some milled slots and stuff riveted onto it, so I'd be tempted to replace it entirely if a splice to too big a hassle, and weld on all the little pieces)

TCB

I suppose I should give an update;
-I'm pretty sure at this point that I want to do this as a proper 14.5mm, unless reloading for the round truly is untenable (I'm most concerned for powder that is slow enough to run). A friend raised a valid point that there was a good chance the mere terrifying size of the thing could easily get it classified as a DD even if it was done as a fifty cal, 50x114mm, or 14.5x99 wildcat. If I'm paying the stamp, might as well go for the gusto (might be easier to do this with my barrel situation, too)
-I got the barrel chunks out of the receiver (finally) but still have to get the barrel locking-collar unstuck. Gonna be one heckuva job, that.
-In a shoulder-fired configuration, I don't think 922r will be a problem, since I'm not using original furniture or fire control components. My most conservative count came up to 10, and I "have a feeling" I will require a new muzzle break (since I wouldn't care to cut on the original) to keep things manageable, so at most the number would be nine, unless parts in the top cover count towards 922r, now.

Quick recoil calcs;
-28.0gr powder (that's 432grains, btw )
-1000gr bullet
-1000m/s
-120lb rifle (I assume all the stuff I'm adding will be a dozen or so pounds)
=Recoil impulse of 22.22lb/sec (a 10lb 308 is 2.76lb/sec)
=Recoil velocity of 5.96ft/sec (8.88ft/sec for the same 308)
=Free recoil energy of 66.23ft/lbs (12.24ft/lbs for the same 308)

What this tells me is I will be thrown back 10X further at 2/3 the speed of my 308 semi-auto, so...skids on the bipod and a slip-n-slide? Also do keep in mind that the gun is recoil operated, so some of the juice is going to that, and that these numbers are for no muzzle break and ignore any padding/damping effects. I would also likely dial back loads to the bare minimum needed to operate the thing for brass preservation purposes.

FWIW, a 15lb 600NE appears to have 1/3 the recoil impulse, nearly 4X the velocity (ow), and 115% the free recoil energy of the KPV-rifle. So I suppose that means this is a soft-shooter by comparison, but it's not like you shoot a 600NE prone, either...

EDIT: A Lahti L-39 in 20mm clocks in at;
33.29lb/sec Impulse
10.72ft/sec velocity
178.46ft/lbs Energy

If the L-39 didn't kill the Finns shooting it, logic dictates neither should the KPV (the Lahti was ~100lbs, apparently; about the same as the recoil-operated S-18/100 in 20mm, which is functionally very similar to the KPV)

TCB