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Old 11-15-2019, 01:32 PM   #31
ericthered
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Default Re: 25mm Payload Rifle [Ultratech]

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Originally Posted by Rupert View Post
Okay. Try the AGS-17, with a 30x29mm grenade. It has a maximum range of 1700m. The 20x28mm grenade from the OICW project having a maximum range is perfectly within reason looking at that, and therefore so is the UT 25mm grenade. If it were fired from a lightweight launcher a case could be made for it having higher recoil than Rcl 3, but it's an underslung weapon so the total weapon system's weight is going to be 3.5+ pounds, and Rcl 3 seems reasonable (that the rules say you can mount it on a heavy pistol possibly not so much).
Throwing a 25mm grenade 2,000 yards is ambitious but doable. The russian AGS-17 can do it, though it weighs over 60 lbs. The OICW program wanted to do it in a man-portable fashion, but never made it out the prototype phase, citing weight as one of the primary obstacles in continuing the project.

I think a man portable grenade launcher that can get 2,000 yards of range on a 25mm grenade is quite doable. I just think it should weigh 6 lbs or more.
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Old 11-15-2019, 01:34 PM   #32
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Default Re: 25mm Payload Rifle [Ultratech]

A loaded AGS-17 also weighs three times as much as the 25mm payload rifle, and almost thirty times that 3.5+ pound weapon system. Probably not a good comparison.
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Old 11-15-2019, 01:52 PM   #33
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Default Re: 25mm Payload Rifle [Ultratech]

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A loaded AGS-17 also weighs three times as much as the 25mm payload rifle, and almost thirty times that 3.5+ pound weapon system. Probably not a good comparison.
It's a belt-fed heavy automatic weapon, in a slightly larger caliber. It's probably quite fair to compare it to the payload rifle, which is semi-portable and semi-auto. Maybe not to the underbarrel launcher - underbarrel and stand-alone long-arm launchers usually have muzzle velocities that are much lower than heavy weapons like the AGS-17 (around 1/3 as fast).

It is notable, though, that the XM-25's muzzle velocity is actually a bit higher than the AGS-17's. And that might be more the model for the 25mm launcher in UT than the M203 is.
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Old 11-15-2019, 05:08 PM   #34
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Default Re: 25mm Payload Rifle [Ultratech]

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It's a belt-fed heavy automatic weapon, in a slightly larger caliber. It's probably quite fair to compare it to the payload rifle, which is semi-portable and semi-auto. Maybe not to the underbarrel launcher - underbarrel and stand-alone long-arm launchers usually have muzzle velocities that are much lower than heavy weapons like the AGS-17 (around 1/3 as fast).
A 25mm ET UBGL has twice the range of the AGS-17, so it's presumably a higher velocity round, though the round is also lighter (Somehow the whole 25mmPC is about half the weight of the AGS-17 projectile). So energy may well be higher, fired from a platform that is both much lighter and not secured by a tripod.

The ET payload rifle, meanwhile, has a heavier round than the AGS-17, though it's impossible to tell how the actual projectiles correspond to each other. We also know that the payload rifle throws its round 7.5 times the distance, so energy is probably much higher, in a weapon system that weighs a third as much (Sorry, a quarter as much; I was forgetting the weight of the AGS-17's tripod).

Neither of these sound like a fun time.

(Edit: as a note, the XM-25 has a max range of only 1100 yards, a mere third of the 25mm ET UBGL's 3300)
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Old 11-15-2019, 05:34 PM   #35
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Default Re: 25mm Payload Rifle [Ultratech]

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Originally Posted by Phoenix_Dragon View Post
A 25mm ET UBGL has twice the range of the AGS-17, so it's presumably a higher velocity round, though the round is also lighter (Somehow the whole 25mmPC is about half the weight of the AGS-17 projectile). So energy may well be higher, fired from a platform that is both much lighter and not secured by a tripod.

The ET payload rifle, meanwhile, has a heavier round than the AGS-17, though it's impossible to tell how the actual projectiles correspond to each other. We also know that the payload rifle throws its round 7.5 times the distance, so energy is probably much higher, in a weapon system that weighs a third as much (Sorry, a quarter as much; I was forgetting the weight of the AGS-17's tripod).

Neither of these sound like a fun time.
Remember, the AGS-17 is expected to fire 6+ rounds per second, while the recommended use for the UT 25mm weapons would usually be single aimed shots. That should make them a bit less brutal, though a medium-velocity 25mm shell fired from the shoulder does sound like a very bad time.
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(Edit: as a note, the XM-25 has a max range of only 1100 yards, a mere third of the 25mm ET UBGL's 3300)
I'm not sure whether the XM-25's range limit is from ballistics or from the fire control of the airburst shells.
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Old 11-15-2019, 06:25 PM   #36
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Default Re: 25mm Payload Rifle [Ultratech]

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I'm not sure whether the XM-25's range limit is from ballistics or from the fire control of the airburst shells.
It uses the same projectiles as the XM307 which has a rated max range of 3,600m, so it certainly won't lose that much velocity in 1,000 meters, and a muzzle velocity of 210m/s gives it a vacuum range of more than 4,000 meters, so I suspect that's just the range at which it's remotely useful.
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Old 11-15-2019, 11:09 PM   #37
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Default Re: 25mm Payload Rifle [Ultratech]

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Originally Posted by Ulzgoroth View Post
It is notable, though, that the XM-25's muzzle velocity is actually a bit higher than the AGS-17's. And that might be more the model for the 25mm launcher in UT than the M203 is.
I'm sure it is - the range is very similar.
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Old 11-16-2019, 01:01 AM   #38
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Default Re: 25mm Payload Rifle [Ultratech]

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Originally Posted by Ulzgoroth View Post
Remember, the AGS-17 is expected to fire 6+ rounds per second
The payload rifle fires up to 3 rounds per second and can rapid-fire 6 rounds per second, all at much higher velocities and presumably energies. Even if it were fired slower, we're still talking about much larger impulses for every shot, in a much lighter weapon that isn't braced by a tripod.
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It uses the same projectiles as the XM307 which has a rated max range of 3,600m
I know it's not quite related to what you were addressing, but the mention of the XM307 made me look it up for another point of comparison. The XM307 fires a more powerful high-velocity 25x59mm round, at only about 4 rounds per second, from a ~70 pound weapon system (loaded), firing from a tripod, while having a range barely above the 25mm ETC UBGL and only a third that of the ETC payload rifle.

I think the numbers in UT are just plain too high.
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Old 11-16-2019, 01:42 AM   #39
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Default Re: 25mm Payload Rifle [Ultratech]

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Originally Posted by Phoenix_Dragon View Post
while having a range barely above the 25mm ETC UBGL and only a third that of the ETC payload rifle.
One of the problems with ETC is that higher velocity shouldn't affect 1/2d range; unless it's dealing with speed regimes where it's drag coefficient changes dramatically, 1/2d should be purely a function of drag coefficient and sectional density. TBH, ETC shouildn't do anything meaningful to a GL, because the reason they aren't higher velocity isn't because of any limitations of propellant, they'd just be uncontrollable, and ETC doesn't help recoil.
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Old 11-16-2019, 02:19 AM   #40
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Default Re: 25mm Payload Rifle [Ultratech]

Grenade Launcher range it seems will depend on angle (like most artillery.. GLs have some overlap with smaller mortars and even some RPG/Recoilless rifles)

there's coverage for US UBGL here: https://www.inetres.com/gp/military/...nade/M203.html

and the M79 https://www.inetres.com/gp/military/...enade/M79.html

both cover the mechanics of firing (including pictures) - its a rather nifty reference site for a wide range of US military stuff. I think the 25mm GLs IRL like the XM25 follow similar rules (most IRL GL probably do, even the automatic GLs)
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