My guess would be the original AAI projectile is the one with the 2lb penetrator. That being the one with a Mass in Flight of 3.04lbs or 1.38kg. It’s also plausible that the 12.78 Caliber length could be used as a stand in for the Penetrator Length. However, I haven’t ran it through L-O spreadsheet yet to check penetrator mass.
i think its cuz light tank don’t get ammo box, only AA and tank destroyer get them. But I agree, 26 ammo is not a lot to work with and HSTV-L do need ammo box.
I think they disabled the “bounciness” of thin armor angled at an extreme angles for all tanks.
I’m not really sure the physics behind ricochets so correct me if I’m wrong, but if the armor is extremely thin, wouldn’t the armor give in to the amount of kinetic force from the round?
I believe there’s a threshold for the thickness (not effective thickness) of the armor in which ricochets are allowed but I’m not sure what that threshold is. for example shooting shooting the HSTVL’s frontal armor at 81 degrees will ricochet.
No this is same issue with leopard 2s and some other MBTs’ ufp not ricochet as well. Same applies to thicker armour like 80mm + 150mm (ERA) on VT4, so not distinctly a thin armour issue. IDK why but speculations is that it has to be one uniformed plate to be able to ricochet.
Well I’m not entirely the bug report that guy made is correct now.
“A shape of things to come? In the late 1970s/early 19808, AAI Corp. developed a number of light tanks from the experimental HSTV-L testbed in the hope of interesting the US Army and Marines in their procurement for the Rapid Deployment Force. This tank is armed with a revolutionary 75mm Ares XM274 automatic cannon. Tanks like this are being proposed for the Army’s Mobile Protected Gun programme, which aims to field a new light tank in the 1990s.”
Actually I read that statement wrong. The HSTVL and RDFLT both DO indeed use the xm274.
The XM884 coming after the hstv-l does make some sense. However the AAI projectile was already developed by early - mid 70s. And the longer AAAC-I and -II projectiles were already prototyped and being tested by 1978. From what I’ve found, the original HIMAG system mounted the 75mm ADMAG. And the HSTV-L was to be fitted with an improved version of the 75mm Ares “Stoner” Anti-armor auto cannon system.
Found a few more documents stating that both the RDFLT and HSTVL did indeed use the xm274. This bug report is wrong which got accepted with only one source
Doing some more reading, it seems there were multiple chassis’ one being HIMAG and the other being the HSTVL. There were 3 different versions of HE rounds, one with a mod fuse and the other two that used infrared prox fuses.
HSTVL did have an HE round as shown on the ammo selector
First one is SABT
Second INRT? Like a training round?
Third HE
Looks like it did have a Burst fire mode as well
@Conraire check out the date they were testing DELTA 6 as well
“Under the MOU, test versions of both the 30-40 ton HIMAG and a lighter 16-20 ton High Survivability Test Vehicle - Lightweight (HSTV-L) would be built; accelerated development of a 75mm automatic cannon and ammunition would be under-taken along with its integration into the HSTV-L; and parallel analysis would be done by the two services to determine experimental employment concepts of the several systems.”
“The concept of the new cannon has now taken form of a high rate of fire, burst or single shot, rotating breech gun, capable of using telescoped (cylindrical) ammunition.”
Proof that the ADMAG was not used on the HSTVL
The HIMAG used the ADMAG and was developed into the XM274 for the HSTVL and RDFLT
Yeah, this does make it confusing for me to follow because of the conflicting information but it’s good that you put it out there.
I’ll just copy and paste my understanding of the bug report from an older thread. If I misinterpret, take something out of concept, or do anything where it mischaracterize the bug report, please let me know.
The HSTV-L (along with the RDF/LT) never used the XM274 gun, but rather used the earlier 75mm ADMAG (Advanced Design Mobility and Agility) gun
Reasoning:
HSTV-L was delivered in 1979, while the XM274 only began testing in February 1983. Meaning that the HSTVL had to have used an earlier variant of the 75mm gun.
The XM274 was a later evolution of the ADMAG system, specifically designed for the MPGS program. This can be seen by longer chamber and redesigned house and barrel.
The reason why the two systems got mixed up was because they talked about these guns as if they were the same system. Rather, the XM274 was an entire new weapons systems and wasn’t a replacement/upgrade. This would’ve required a new turret due to the wider receiver and housing in order for the XM274 system to be used.
I think with the sources you gave as well as what other have given (ie spookston, and many more), it’s pretty much stated that the HSTVL used the XM274 at some point in it’s development.
So allegedly the timeline presented on the bug report is wrong. One question I have is if the HSTVL first used the ADMAG system, when was it replaced with the XM274?
Second/third Claim:
This may have some validity. the ADMAG and the XM274 dimensions are different.
So when the XM274 was mounted on the HSTVL how did the larger gun fit into the turret?
Though, with the amount of documentation there is regarding the HSTVL using the XM274, this might as well be a simple swap or of that sorts. I wish we had a reports of when that swap occurred.
The timeline is a bit off with that bug report. The initial HSTVL used a different weapons system that I can’t identify. Could have been an earlier ADMAG system but that looks nothing like it.
This is the original HSTVL that was a mockup back in 1979
The author of that bug report makes an invalid claim about the barrel end of the XM274 being different between the ADMAG and XM274 and that it is evident on the HSTVL. This is not true since the LAVMC uses the same mid barrel squarish plate.
Additionally, the HIMAG and HSTVL visibly seem to have different weapons system when next to eachother. The HSTVL has a longer barrel that seems to be thicker.
The testing done in this report, was done in the same year the photos the HSTVL was on the stabilization motion testing device. So it’s safe to assume that this chassis did the weapons testing of the XM274 mentioned in the report.
Could have been, even the first two prototype photos have different weapons systems. I wonder if there are more than one chassis out there with different guns.
