9.53x76 SR US Xpl Flechette

Hello guys,
please can anybody help me with ID of following two Flechette cartridges?
First one is quite ordinary with see-through sabot …but except the OTAN marking in the HS having quite interesting additional letter “S” (green primer seal). What does it mean?
The second one has slightly longer black opaque plastic sabot, it’s little bit heavier (exact weights I can provide on FRI), red primer seal and additional letter “R”. (same letter font like above mentioned “S”).
Both plastic containers have the injection lugs.
I have checked carefully - no signs of reloading or any handyman’s modification.
Any info will be appreciated!
Thank you
Tomas

1 Like

From HWS Vol III, Chapter 15:

9.53mm Multiple Flechette Cartridges

During 1968, Frankford Arsenal let a development contract to Winchester for a preliminary design study of a multiple-flechette rifle system. To satisfy the ammunition sub-task of the contract, Winchester utilized the ballistic test results from their earlier 10mm development project and proposed a 9.53mm Multiple Flechette Cartridge using a plastic pusher sabot holding four 9.4-gr. flechettes with a launch velocity of over 4,000 fps. To reduce the weight of the cartridge, Winchester developed an aluminum case made from a 7475 alloy which would readily withstand the chamber pressure of this type of round. The case configuration was rimmed with a long tapered body to accommodate the elongated sabot. The case length was about 3.00 in.

Apparently, 7.62mm NATO head forming tooling was used for early cases, which are headstamped WRA {NATO Symbol} 69. This case had a Winchester No. 120 brass primer that was either with or without red lacquer. A Winchester report indicates that the cartridge lots were identified by letters (A through V) and were to be included in the headstamp between the NATO design mark and the year date (69).

A brass version of this case was also made at the Olin East Alton plant for internal ballistic tests. These had WRA {NATO Symbol} 69 and WRA {NATO Symbol} 70 headstamps, initially using the 0.210-in.-diameter No. 120 primer with brass cup without sealant. Brass cases were also loaded with the 0.120-in-diameter Bloem primer, these using cases headstamped W C C 6 9 and W C C 7 0 with smaller letters and numerals. This primer used a separate anvil which was inserted in the vent hole prior to seating the charged cup. The reduced diameter allowed the use of a stronger case head to withstand the pressures needed to obtain the desired sabot velocity while still providing space for a sufficient propellant charge weight. Both brass and copper-alloy primer cups without seal have been noted with this primer. The Bloem primer was also loaded in the aluminum case headstamped W R A 7 0 (DAAF03-70-C-0012, 1 Feb. 71 and Olin-Winchester-Western Division Final Rept. Development of 9.53mm Multiple Flechette Cartridge, Part 1, 26 Oct. 70-Revised 1 Feb. 71).

An examination of 9.53mm Multiple Flechette rounds discloses that both the brass and aluminum cases were loaded with a number of different plastic sabots having different ogives and lengths, and loaded to various depths giving a cartridge overall length of between 3.333 and 3.360 in. Black, gray, opaque-clear, and white sabots have been noted in brass and aluminum cases. Green sabots have also been seen in aluminum cases. The rounds provided to Frankford Arsenal for test have aluminum cases headstamped W R A 7 0 with nickel-plated primers without seal, loaded with green-colored plastic sabots holding four 9.4-gr. flechettes of Winchester design.

This section of HWS Vol. III has more on this interesting experimental cartridge, including a box label.

Hi Mel,
thanks a lot for really comprehensive info! There are very few info available related to these projects on the web pages.
I have checked your pages and will try find out anybody visiting ECRA meeting who could bring me this book to Europe. Looking to the content - it’s a must for me :-).
Thank you
Regards Tomas

Paul Smith in his series Variations of Military Experimental Calibers speculates the " R " in the headstamp indicates a lot number designation. So the “S” in the other headstamp may indicate another lot number.