.50 BMG with pre engraved steel bullet?

This came from the Berk Lewis estate. Nothing found in HWS volume 2 or 3, although there is a somewhat similar projectile for a .50 caliber in Volume II, page 241, figure 225D, but it uses a broad copper rotating band with the pre-engraved grooves with clipped corners at the front.

Headstamp F A 42 although the A has been cut away by what is probably an index or alignment notch in the rim.

Bullet diameter .527 over the high points and .488 ahead of the “rotating band” area and in the grooves. Bullet is steel and attracts a magnet.

Neck length reduced so overall case length is 3.60”/91mm instead of the nominal 12.7 x 99mm standard case. Other dimensions appear standard.
Overall cartridge length 5.40”/137mm
Primer in place, does not feel like there is any powder. Bullet is very tight fit, not crimped.

What is this?
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Possibly related, Aberdeen Proving Grounds report EFFECT OF VARIOUS DRIVING BANDS ON THE AERODYNAMIC PERFORMANCE OF PROJECTILES AT HIGH VELOCITIES, 1946 :

0.50 Projectiles With Pre-engraved Driving Bands, 20 mm - 0.50 High Velocity (HV) Aberdeen, 1946.pdf (1.8 MB)

50%20Pre-engraved%20projectiles%20WW2%20a1_zps4lt0xafd
50%20Pre-engraved%20projectiles%20WW2%20a2_zpshv3xjfo5
50%20Pre-engraved%20projectiles%20WW2%20a_zpsctlsftni
50%20Pre-engraved%20projectiles%20WW2%20b_zpsvglmughj
50%20Pre-engraved%20projectiles%20WW2%20c_zps4ng3cnl1

Brian

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John, that’s a really great find, thanks for sharing. It is loaded with a pre-engraved projectile for tests in a modified .50 cal. machine gun having a barrel with four grooves. The slot in the case is used to properly index the cartridge in the belt.

Regards,

Fede

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With the slot in the case, does it also have a pressure test hole?

Jesse, the slot is part of the test cartridge design and is used to index the projectile with the barrel grooves. It is not a pressure test.

Regards,

Fede

Only the slot, no pressure test hole.

Standard U.S. .50 BMG barrels used EIGHT groove rifling, and this experimental round is made for FOUR groove.

Once again, Fede comes up with a great answer and documentation. THANK YOU!

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The pics posted by Fede are from "Hypervelocity Guns and the Control of Gun Erosion" pages 551-552, published by the US National Defense Research Committee (NDRC) in 1946. Here is a download link:

Lots of interesting stuff (nearly 700 pages) on taper bore guns and ammunition, bore liners (chrome, Stellite, Molybdenum and how about Tantalum!), the FISA protector, powder gases, bore friction, armor piercing cores and terminal ballistics, and much, much more (I sound like an advertisement).

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Larry, thanks a lot for this document! Great info in there!

Also in IAA journal 472 pg. 54 are “40-year old black & white photos courtesy of the Woodin Laboratory and Dr. J.R. Crittenden Schmitt” of several Cal. .50 US Pre-engraved Projectiles and Projectiles with Driving Bands. No details, but interesting photos. John, I think yours is shown in the bottom photo, second from the right.

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image

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Any chance for larger images? Source?

Thanks,

Brian

They are from pages in the doc Larry posted above…

Thanks, in a hurry and didn’t pay enough attention

Brian

Here is a portion of a photo posted by USSubs, IMG_0503, Bill Woodin’s Laboratory in pictures II, showing some loaded .50 BMG pre-engraved projectiles mixed in with .50 BMG fitted with FISA protectors:

Brian, what is a FISA protector?

From the left, cartridges 1, 3 and 7 in the above picture of pre engraved bullets.

It’s the protector around the neck, to reduce bore erosion

HWS Vol2 pg183

Jestertoo, thanks! I was guided to the FISA device already.

Here is a quick photo of the few related ones I have.

Rhys, the .50 on the right is not fired, right?

The case and the steel collar around the neck seem to be fired, the projectile does not however.

Casing is a 1942 dated Frankford Arsenal case with fires primer, and the collar has slight cracks around the grooved section at the mouth. Projectile looks too clean to have been fired, and the base is stamped “489”. 2 of the other variants are also stamped with numbers on the base.