37mm pre engraved rounds.

[SG500]

Don't get too excited guys I don't have one of these!!
There's a photograph of one in a book called US Hypervelocity Guns and Ammunition - see link below. I bought a copy of the book and it really is a good read for anyone interested in such things.
My query is - has anyone got one of these elusive rounds. The book photos are in black and white. Some nice clear colour photos would be nice to see.
Dave.

http://www.auctionarms.com/search/displayitem.cfm?itemnum=8497013

 

[Falcon]

Are these necked down 40mm Bofors rounds?

 

[HAZORD]

I have 2 different projectiles. Till now, I never knew what they were for. I will take some photos when I get home tonight.

Is there any information about the cartridge case for them?

Thanks,

John

 

[SG500]

Fantastic, can't wait to see the photos.
To quote page 553 of the above mentioned report:

"Modified Bofors 40mm Mechanism
This gun was modified to fire 37mm pre-engraved ammunition by using six grooves of 0.030 inch depth, with the lands pointed on a 30-degree slope at the origin of rifling and by changing the feed mechanism to prevent roation of the previously indexed round. The projectile had six corresponding splines pointed with a 30-degree slope to match the lands. They were aligned in the case so that proper indexing of the case would automatically index the round. The case was the standard 40mm case, necked to fit the 37mm pre engraved projectile. A guiding groove was cut in the base to guide the case on a vertical aligning track. An extension of this groove was cut in the edge of the flange to guide the case along a horizontal track in the tray. The complete round assembled in the clip are show in figure 7 (see earlier in this thread).
The feed mechanism was modified by insertion of guiding tracks to maintain alignment of the rounds. A vertical track was mounted on the base guide to engage the slit milled in the base of the case, as it moved downwards. A similar track was mounted on the feed tray and extended in sections on the breech ring and breech block to engage the groove in the edge of the flange. Thus while the round was moving vertically to the feed tray it was guided by one track and groove, and by another track and groove while moving horizontally. A spring loaded guide latch acted as an extension of the vertical track to align the case during the transition of the vertical track to the horizontal track. While the round was being rammed by the feed rollers, a flexible guide above the case prevented the case flange from leaving the horizontal guide track. This work was not completed under NDRC auspices. It was continued during 1946 on an Army contract with the plan that the mechanism will be tested for functioning of pre-engraved ammunition under automatic firing conditions."

 

[HAZORD]

Dave,

Thanks for the information. Does it show the headstamp of a case or indicate the model or part number of the case? Now I need to find a couple of cases, or neck down a couple of 40s and mill grooves on the heads.

 

[SG500]

Dave,

Thanks for the information. Does it show the headstamp of a case or indicate the model or part number of the case? Now I need to find a couple of cases, or neck down a couple of 40s and mill grooves on the heads.

No there's no info regarding headstamps.
Dave.

 

[EODGUY]

There is another pre-engraved 37mm projectile out there also. It has the typical gilding metal rotating band that has been pre-engraved and was loaded in the center case of the photograph for an experimental recoilless system. I have never been able to acquire one to match the case and figure that my life expectancy isn't enough to ever find one. Still the case is a nice one.

 

[HAZORD]

I guess I will have to take a photo of that one too.

 

[EOD]

There is another pre-engraved 37mm projectile out there also. .

Thank you for sharing the image with us.
Is the lower one a composite plastic case?

 

[EODGUY]

Yes, black plastic and a brass base. I don't have any information on the case as to timeframe, purpose, etc. The neck length is slightly longer than the typical M16 case.

 

[SG500]

Nice cases Bob, thanks for sharing them.
Dave.

 

[Hoeksel]

Yes, black plastic and a brass base. I don't have any information on the case as to timeframe, purpose, etc. The neck length is slightly longer than the typical M16 case.

Not sure if it is related but I used to have a dummy of the American Armament Corporation 37x202R S.A.-gun. The dummy was made of wood and brass (from a normal case) and if I remember correctly ~ 2 mm longer then a normal case.

Always wondered why; maybe they are specifically made "not to fit"?

 

[HAZORD]

Submitted for your approval

Shot some photos and took some measurements of the projos.

Shorter projectile OAL 5.735 inches, length of steel body without windscreen 3.80 inches. Nose is counterbored .75 inch diameter 2.208 inches down. Body diameters 1.452 at grooves, 1.512 across lands, 6 grooves total.

Taller projectile OAL 6.0 inches, length of steel body without windscreen 4.045 inches. Nose is counterbored with a slightly tapered bore mouth opening .80 inches tapering to .75 inches .89 inches down.

The nose of both steel bodies is externally threaded for the aluminum windscreen. External threads 1 inch diameter, threaded boss .350 inches tall. The aluminum windscreens are interchangeable. The windscreens are 1.215 inches in diameter at the widest point, ranging in length from 2.285 inches tall to 2.297 inches.

Both projectiles have tracer bores in the base, .50 inches in diameter .60 deep.

The 37mm recoilless shown has 12 grooves total. Case length is 215mm, no headstamp.

 

[SG500]

Thanks Hazord, you have yourself some really really rare ones there. When I posted the original thread I thought I was being a bit hopeful expecting anyone to actually have any of them. Very nice, and the recoilless one too.
Dave.

 

[Grenademan2005]

Are they WWII or post war?

 

[HAZORD]

Dave,

That is why I was so happy when you started the thread as I didn't know what they were. I've had the taller one since 1985. It came from one part of the country, then I got the second one a few years back from a different part of the country and thought it was the same thing, till I put them side-by-side.

I wish that the recoilless round would come apart, but the projo is loosely crimped in the case (it rotates) but won't come out.

 

[SG500]

Are they WWII or post war?

Hi see post 4 above "It was continued during 1946 on an Army contract with the plan that the mechanism will be tested for functioning of pre-engraved ammunition under automatic firing conditions"

Looks like it may well have been WW2 or very soon after.

Dave.

 

[Grenademan2005]

I have readed the entire thread and didnt see it, sorry. But they seen auction in Europe, or just exp. in US?

 

[shelldude]

John,

Beautiful & RARE projectiles! Any idea why the counterbore?

Randall

 

[HAZORD]

Randall,

I have three theories for the counterbores. For the shorter one, my guess is that it could be a cavity for explosive for a future variation. Both of these had merely a screw-on aluminum windscreen. Neither would have been good for armor piercing or HE as built.

The second theory for the couterbores would be to regulate the weight and center of gravity to optimize ballistic coefficient and accurate flight by minimizing wobble etc.

The last theory would be as a cavity for a tungsten core. In the U.S. all antiarmor projectiles of any size have tracers. The 40mm Bofors had tracers in all of their projectiles, but the fact that these had tracers could push the theory that they were to have an armor piercing end-use when the design had been completed.