Discussion in 'Weapons, Technology & Equipment' started by Chris C, Dec 10, 2018.
Hmm, I can probably dig it up again at lunch (in 1-2 hours). I don't think it was post-war.
Here we go. Fortunate that they have this report as an appendix.
I suppose it's possible that the range was 3000-3500 yards? I hadn't thought of using the map locations to check; it's odd that the report says 300x-3500x and I think one way or another there is a typo.
Coming back to this thread...
Aside from these benefits, I am under the impression that the full charge HE rounds would have posed a difficulty in firing indirect. Since the 17 pounder used single piece ammunition, it was not possible for the gunners to reduce the charge when firing indirect at closer targets. What I'm not clear on was whether full charge could actually be used in indirect shoots at longer ranges or not. Any thoughts?
Incidentally, a remark in the war diary of 20 A/Tk Reg't for a pepperpot barrage in support of Operation Plunder reads: "The max range of tgts is 7800 yds (a little beyond the range of 17-pr on fd mtg and a lot beyond that of 17-pr on SP mtg. Arrangements can be made to run the guns on a ramp, thus increasing the elevation)."
Would reducing charge present difficulties with sighting? I've never fully understood the issue with the 76mm Sherman HE performance but I think sights were involved. The high velocity 76 required thicker projectile walls which reduced the cavity volume. They could have lowered the velocity (reduced charge) and used thinner walled shells (the 75mm HE ones) but that would have required the gunner to change site setting between HE and high velocity AP to account for more drop.
I could be completely wrong on this.
Well, I think it would have. Typically when firing on a strong point like a bunker or building, the gunners would first fire some AP rounds to create some holes and then follow up with HE. For that purpose they would want to use full charge HE so that the ballistic characteristics of the rounds would be the same. That would all be with, effectively, direct fire.
Right, I think Americans were thinking the same thing with the 76mm, but that resulted in much less explosive in the thick walled projectile than in the slower 75mm.
I found some actual numerical values about the amount of wear on the gun from full charge versus reduced charge ammunition. In the 1952 RAC booklet for the Archer's ammunition the 17-pr gun was listed as having an accuracy life of 425 "EFC's" - "Effective Full Charges". The amount of wear from different ammunition types was given at:
Full charge AP/APC/APCBC: 0.5
Full charge APDS: 0.75
Full charge HE: 0.25
Reduced charge HE: 0.03
I'm actually kind of amazed that the reduced charge HE had that little effect, given that the muzzle velocity of the reduced charge HE (according to a diagram in Mark Hayward's Firefly book) was 1800 f/s, compared with 2900 f/s. However, in this manual the charge for the reduced charge HE is noted as "WM" which must be "Cordite WM", and the other ammunition is "NH" which must be something else. (Anyone know what NH stands for?) I'm perplexed that in one place full charge HE says it has WM propellant and another place NH.
NH was the UK propellant designation for a United States single-base flashless propellant, either US Hercules NH or US Dupont NH (later referred to as M6. The NH in fact stood for Non-Hygroscopic. They were imported from the US from 1940, later, when only the Dupont powder was produced this became known as Powder Propellant M6. The UK continued to use the designation Powder NH for both.
Hi op-ack, thank you for that information!
An HE round was developed for the Firefly but it was slightly different from that for the towed gun - I think the HE content was slightly lower - possibly the FFs did not use reduced charges and had to have a thicker walled shell
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