Looking more into it. That picture is just a mockup it isn’t a functioning model.
Spookstons interview with an HSTV/L engineer makes me question that. He specifically mentions the XM274 in his questions to the engineer.
That’s wrong, the ADMAG on the HIMAG is evidently different than the XM274 on the HSTVL. I added more photos
Isn’t that photo of the mock up from 1979?
The first two are from 1979.
The ones on the stabilization motion testing device with the XM274 are from 1983 which aligns with the timeline in the document that the bug reporter posted.
Further info, HIMAG came first with the HSTVL being it’s evolution
The HIMAG definitely has a different gun, or at least gun length, compared to the HSTV-L.
But, according to the Eugene Stoner tapes on the 75 mm gun, the XM-274 is distinctly different from the AD(MAG), most notably having 3 holes on top of the gun instead of the 5 that the HSTV-L has. So unfortunately, it seems that the XM-274 wasn’t actually mounted on any vehicles, just like the 90 mm variant wasn’t either.
Spoiler
Looking at all the information given. I am confident the HSTV-L didn’t have the XM274 installed. But had it gone into full rate production would have. The idea that the XM274 wouldn’t fit is poor given the fact the turret was able to be dropped in and out for replaced technologies. Both ADMAG and XM274 used the same loading system aswell. There is no question the XM274 was designed to be installed into a production HSTV-L.
So question comea does Gaijin go with production gun (XM274) or Developmental gun (ADMAG)
Also side note is the ADMAG the listed 1.5sec limit gun if so then the ROF needs to be nerfed.
I still believe that it uses the XM274 before it was named as such. You can see in this heavily redacted congressional meeting that the “Super 75mm” was installed on the HSTVL. This Super 75mm fired longer apfsds rounds and had a different weight and firing velocity. (lines up with the stoner video that there was a longer round) It even mentioned the penetration and at what distance. :(
We know the RDFLT was based off the HSTVL so it wouldn’t be strange for it to use this version of the cannon as well.
I really wish it wasn’t redacted because that would be our golden egg.
If anyone wants to try and find it, it’s from
Hearings on Military Posture and H.R. 10929
Department of Defense Authorization for Appropriations for Fiscal Year 1979 Before the Committee on Armed Services, House of Representatives, Ninety-fifth Congress, Second Session · Part 3, Book 2
Page 1549
@Conraire Do you have some knowledge concerning this?
It’s just that the document says which will be installed.
That is proof that the XM274 was designed for the HSTV-L. Honestly I think the XM274 should be the variant of the tanks life cycle used. Especially because if the ADMAG is used then the HSTV-L probably needs to return to an 1.5 second reload.
ADMAG on the left, XM274 middle, 90mm right
From the Stoner video
The two cream colored center section telescoped rounds are 75s
“the 75 on the right is the early advanced development gun projectile, the one on the left is the current 75mm projectile or cartridge”
We can now 100% say that the HSTVL and RDFLT used the XM274. HSTVL uses MC-AAAC, later confirmed to be designated as the XM274. This was a weapon jointly made by ARES and DARPA.
ARES made the ADMAG which was mounted to the HIMAG which was developed into the XM274. It all makes sense now.
Here they talk about the differences. From page 27-2
XXVII. HIMAG/HSVT-L
“The Marine Corps, however, with different threat priorities, continued interest
through 1986 in the potential of the lightweight 75mm gun for use on its LAV high
amiored vehicle. 9”
Which brings us to the document that designated the MCAAAC as XM274…
I can sleep now lol
The reload is correct either way, as the numerous primary documents used for fixing the reload specifically mention the gun as installed on the HSTV-L, the name of the gun really doesn’t matter.
It does though i am certain all those documents that were listed for the reload made mention of thw XM274 I would have to double check but if so then 1.5 is the ADMAG.
The HSTVL and RDFLT uses the MCAAAC (XM274), it’s 1 second. The ADMAG was only used on test platforms and the HIMAG.
I’m confident the 274 was designed for the HSTV-L/RDF-LT or atleast production variants but if they ever went around to putting it on the testbed itself idk.
27-7 Makes it pretty clear that the XM274, or at least the final product of that program, was mounted on the HSTV-L, although that continuing arrow is a pretty interesting (…).
Without definitive this gun that gun it’s going to be up to Gaijin’s determination. Looking at photos of the HSTV/L it does look like it is possibly the ADMAG mounted on it. Still without a better look it is all speculative. Which is why I would like Nicholas Moran to do an inside the hatch on it.