Question About "internal" case threads on Russian 100MM case


Thanks to an overseas collector and IAA Member, I was able to acquire this beautiful inert, Russian, 100mm BM20 APFSDS-T projectile. Last week, I was fortunate to purchase a Russian, brass 100mm case (also from an IAA Member - Bruce) that I hope is the correct match for this projectile fitted with a non-matching primer assembly. The case was captured by Israel and at some point re-marked with hebrew stenciling. Upon careful examination, I observed that there looks to be internal threads on the inside of the case mouth, stopping at the case neck/shoulder. Does anyone have any ideas about this? The treads are VERY shallow so maybe they serve as an increased friction point to help keep the projectile seated??? Totally made that up. I am pretty sure this case was originally fitted with a different 100mm projectile and not an APFSDS-T projo. Anyhow, any ideas on these threads would be appreciated.



Jason, the case crimp is for HE or APHE projectiles. Also the case date and the projectile date are very far apart. Not that the case could not have been reloaded but as said the crimp is simply not for this projectile.
Also the Israeli marking is featuring a number which is identical to the year of the case, so the Israelies will not have loaded this projectile (if they had the chance to puchase single ones) as then a later year matching the proj. (if the 58 is the year in that text) in the Hebrew markings should be mentioned.

The grooves inside the case neck are no thread but just the marks from turning the case to the required diameter. If the rough surface is intended or just an allowance in manufacturing I can not tell, this is usually given in the production specifications (technical drawings for the workshop).


Thank you so much for the great info, EOD! Super appreciated.

My understanding was that this case was captured live, fitted with the Russian loaded HE or APHE projectile when Israel captured a Russian made tank used by an attacking country? I know Israel often utilized captured ammunition and equipment in the Countries early years to study and in many cases utilize in combat. I bought it hoping that regardless of HS markings, stenciling and crimp style that it would be a correct case match (in shape, size and profile) as the case used by the 100mm BM20 APFSDS projectile developed years down the road, hopefully for the same tank gun system. Wishful thinking on my part :-) I love when I can display a matched up inert projo with its inert case. In a perfect world, I strive to find the exact case with the correct marking, primer assembly and projectile so I can section it :-)

Anyhow, THANKS BIG TIME! Those threads / tool marks were driving me nuts.



Yes, Israel used planty of T-55 and other captured armor. At least in 1990-1991 they had T-55 variants or the chassis in service (they rebuilt many into heavy IFVs “Achzarit”) as Germany delivered (for free) huge stocks of spare parts from GDR stocks.
Besides spare parts also complete “samples” of all sort of military armor etc. declared as “agricultural equipment” was sent there. Some of which raised questions with customs officers due to their very green paint jobs…

Your assumption on captured ammunition is pretty much correct I think. Even though the case does not fit the particular projectile it is quite interesting with the Hebrew markings on.

The Achzarit: … ier.12847/