Comments for Instead of a Whatziss, a Whyziss

Instead of a Whatziss, a Whyziss

2009-06-11T12:54:41Z

Alrighty then - two weeks ago we had this Whatziss, the Czech RPG-7 sub-caliber trainer.

Here's a picture of the Arsenal's RPG-7 with the PG-7 sub-caliber trainer inserted. Note this is the basic RPG-7 - not an RPG-7V, which is more common. The RPG-7V has the provision for the telescopic sight, though it's not always fitted. The original RPG-7 was just an evolutionary step up from the RPG-2 - in terms of a bigger warhead with a greater range, and adjustable iron sights, vice fixed. The markings on the trigger group of the Castle's RPG (which is deactivated, though I'm considering applying to reactivate it so that I can use the trainer in it) are not the ones you commonly find on Soviet RPGs, which has led to speculation that the one we hold at Castle Argghhh! (which came out of captured stocks sold by Israel) may be one of the early prototypes. But, we don't know, that's just speculation from the experts who've examined it. It could also just be from an unknown maker in some Pact nation. It's not Chinese.

Now that we know what it is... let's address the "why's" of those features that led you down the primrose path - the 'eccentric' nature (that is, off-center) of what looked like a splined shaft and bearing, which in fact was a rifled barrel held in place by a fixed collar.

So, here's a few views of the trainer to refresh your memory. Now that you know what it is - the question becomes, "Whyziss?"

A view without the collar.

Why is it made the way it is?

Comment from John of Argghhh! on 2009-06-12

2009-06-13T02:16:54Z

But, Og, I've got *tests* to run this weekend...

Comment from og on 2009-06-12

2009-06-13T00:40:36Z

OK< dude, come clean before I lose the rest of my mind.

Comment from John of Argghhh! on 2009-06-12

2009-06-12T19:38:31Z

Of course, what JW *meant* to say was deep grooves...

Comment from JW on 2009-06-12

2009-06-12T19:34:41Z

I would guess the deep lands are to permit blowby and reduce the muzzle velocity so the trajectory better replicated the normal RPG munition. We used to have a 9mm tracer sub cal device for the AT-4.

Comment from Sgt. B. on 2009-06-12

2009-06-12T06:03:49Z

I'd just like to know where you get all this neat stuff!

I mean, used to be we could just pick 'em up on the side of the road next to the unfortunate whose tried to fire it at us, but what about one (suitibly demiled) to mount on the wall behind the bar?

"Whyziss?" - Making room for the "gun" part of the trainer? Positioning it flight of the training round to replicate the flight of the war shot? (The SMAWs spotter rifle operated under the same idea - duplicating the flight path of the main rocket...)

Comment from John of Argghhh! on 2009-06-11

2009-06-12T03:32:55Z

Pogue: Dream-killing bastard.

Comment from Pogue on 2009-06-11

2009-06-12T02:25:51Z

"The 14.5mm trainer. If Sarco ever gets permission to import 'em... "

Uh-huh... Then you'll want to get the DEWAT M109, then you'll want to REWAT it so you can set up the reduced range and use all your reduced range FDC stuff, then you'll be saying, "You know, I've got enough land for a 5 Green Bag..." Before you know it you'll be upsetting the neighbors. :p

Comment from ry on 2009-06-11

2009-06-12T02:17:00Z

I'm coming in from left field here and saying that it's built that way to induce some type of spin to stabilize flight path. EIther that or is pertaining to the airfoil nature of the rocket and which direction the 'lift' works. By putting it off kilter and down, at least in your photo it's down, you could over come a downward force somewhat.

But that's me. Now how do I put the *good tequila* back into the catapult suspension?

Comment from John of Argghhh! on 2009-06-11

2009-06-12T01:10:57Z

Tripper - many of the rockets we find in the Iraq and Afstan theaters are of Soviet, Chinese, or Iranian origin. Many of the russian/Soviet rockets may have come from stockpiles in Syria, Iraq, or elsewhere in the world.

Most of the new manufacture rockets (as far as I know) have a Chinese or Iranian origin.

Comment from Tripper on 2009-06-11

2009-06-11T23:31:56Z

Yes, yes. More to the point - where do all these RPG rounds come from? Malicious Folks are firing them off in large numbers all over ME/Central Asia. These rounds don't grow on trees. There must be factories somewhere producing them. And they are just like any other round of ammo. They must get broke, corroded, etc. I cannot believe that all the rounds being fired off by the Malicious Folks have been in store since the Good Ole Bad Ole Cold War. Why don't we find the factories making RPG rounds. Make 'em an offer they can't refuse...

Completely missing the Whatziss/Whyziss point, I know, but fascinated to know who the RPG minters de jour are. I want to add them to my mailing list.

Comment from rikkochet on 2009-06-11

2009-06-11T18:24:46Z

It's cruciform rifling, copied from a rare Puckle gun. Round bullets for Christians, square bullets for Infidels, cruciform for anyone else.

Comment from John of Argghhh! on 2009-06-11

2009-06-11T17:49:24Z

We're not trying to take down the RPG - what little of that there is to do I know how to do. I'm referring to the sub-caliber device. If you missed that discussion, click on the first link in this article.

The sub-caliber trainer mimics a rocket.

Comment from Old Gaijiin on 2009-06-11

2009-06-11T16:51:30Z

Which manual are you using to to take down your RPG?

Comment from John of Argghhh! on 2009-06-11

2009-06-11T16:41:51Z

The 14.5mm trainer. If Sarco ever gets permission to import 'em...

Comment from Pogue on 2009-06-11

2009-06-11T16:29:17Z

My guess is the offset bore allows a point of impact that is in the same vicinity as the grenade - since the grenade is fin and spin stabilized the point of impact isn't going to be the same as borsight. I'm going out on a limb here, but the deep groves could be to allow sufficient blowby to reduce the velocity of the 7.62 X39 round, again to better simulate the POI of the grenade. We would develop a special training round for this... (Remember that nasty subcaliber device for the 155?)

Comment from og on 2009-06-11

2009-06-11T15:54:26Z

hey, I'd send it in an envelope it it would help. The rifling is cut far too deep for that caliber by far, and I'm trying to understand the reasons for it. I'd also like to see if the rifling is cut to the same depth through the bore, or if it has deeper grooves toward the muzzle. Based on the proportions I can see, it looks as if the groove diameter is about .020 more than the land diameter, which is excessive. More than excessive. insane, in fact.

the normal land/groove for a 7.62 round is 308 groove diameter and .300 bore diameter (land diameter)

Comment from John of Argghhh! on 2009-06-11

2009-06-11T15:16:29Z

Oh, and by the way - should any *users* of this thing drop by, I'd love some disassembly instructions. I've figured out how to do everything except remove the bolt.

Comment from John of Argghhh! on 2009-06-11

2009-06-11T15:15:20Z

Og, do you need my Paypal address? 8^ ) Of course, I'll have to dig up some military ball ammo. The bulk of the 7.62x39 I have at the moment is soft-points, which will make recovering a useful-for-inspection round a bit trickier.

Comment from og on 2009-06-11

2009-06-11T15:02:30Z

To allow the point of impact of the 7.62 x 39 round to duplicate as closely as possible the point of impact of the RPG.

As for the rifling, I cannot imagine why they'd rifle anything like that, and I'd give a dollar to see the round after it exits that muzzle.

Comment from John of Argghhh! on 2009-06-11

2009-06-11T14:59:11Z

The hole in the warhead is centered on the bore. The collar and the barrel are off-center.

Comment from LaMigraa on 2009-06-11

2009-06-11T14:53:32Z

"Why is it made the way it is?"

Boresighting.

Comment from Rivrdog on 2009-06-11

2009-06-11T14:50:04Z

Hmmm. Does anyone else notice that the nosepiece is off-center? The whole grenade appears off-center in the launching tube, but the fiddly-bit inside of the nosepiece-fuze ring seems off-center as well.

Whyzzat?

Comment from Argent on 2009-06-11

2009-06-11T13:26:47Z

My best guesses

a)

1) Yellow because that's an easily seen 'training' colour
2) Barrel (and 'gun') to provide an emulation of the force and shock of using the real RPG for training familairisation purposes
3) Bolts in order to allow the angle to match the direction of force in the real RPG
4) Paint to ensure the angle isn't played with by the hoi polloi
5) the collar, ring etc is for structural reasons.

b) it's cheap.

Comment from AW1 Tim on 2009-06-11

2009-06-11T13:22:20Z

John,

   My guess would be allow the sub-calibre training round to more closely emulate the flight characteristics of the actual RPG.

   The slower RPG will have a more parabolic flight path than the higher-velocity training round, and so you want to see the training round hit where the RPG is supposed to.

   Anyway, that's my 2-cent's worth :)