Steve Jackson Games - Site Navigation
Home General Info Follow Us Search Illuminator Store Forums What's New Other Games Ogre GURPS Munchkin Our Games: Home

Go Back   Steve Jackson Games Forums > Roleplaying > GURPS

Reply
 
Thread Tools Display Modes
Old 05-01-2016, 07:39 AM   #1
acrosome
 
acrosome's Avatar
 
Join Date: Aug 2010
Location: The Land of Enchantment
Default M855A1 ammo- AP?

Well, just as it says on the tin: Should M855A1 5.56mm ammunition be considered some sort of armor-piercing round in GURPS terms, i.e. AP or APHC?

It was clearly developed with increased penetration in mind, and seems to have succeeded in this goal. Further, the design- a copper jacket around a steel core- certainly sounds like APHC. But either of those (AP, APHC) in different ways reduces damage as well, whereas the M855A1 was designed to retains the 5.56mm round's tendency to fragment in a target and thus increase wounding.

Should it be it's own "special" thing? That seems like a poor solution.
acrosome is offline   Reply With Quote
Old 05-01-2016, 08:01 AM   #2
weby
 
weby's Avatar
 
Join Date: Oct 2008
Default Re: M855A1 ammo- AP?

Gurps AP rules leave a lot to desire as there is not enough variability at the lower end of the range. The first step of basic penetration to (2) is just too big.

In third edition there were optional rules in modern firepower where there was a (1.25) modifier semi armor piercing rounds. I think that M855 was listed as such in there.

Also note that M855A1 definitely does not perform as well in penetrating as a full AP round like the M995.
__________________
--
GURPS spaceship unofficial errata and thoughts: https://gsuc.roto.nu/
weby is offline   Reply With Quote
Old 05-01-2016, 08:14 AM   #3
acrosome
 
acrosome's Avatar
 
Join Date: Aug 2010
Location: The Land of Enchantment
Default Re: M855A1 ammo- AP?

Frankly, reducing damage by 0.7 and dropping the size modifier by one (pi++ becomes pi+, etc.) is excessive for a human target. Really, what's the significant difference if the projectile passing through your body is steel or jacketed lead? (Ignoring fragmentation.) Most modern small arm AP is really a sort of APHC, anyway (see the M993 frex) so you should probably only get less damage if the bullet has to penetrate significant DR- for instance, if the AP modifier makes the difference between a penetration or not, shaving the soft outer layer off the smaller penetrator.

Last edited by acrosome; 05-01-2016 at 08:23 AM.
acrosome is offline   Reply With Quote
Old 05-01-2016, 08:25 AM   #4
weby
 
weby's Avatar
 
Join Date: Oct 2008
Default Re: M855A1 ammo- AP?

By standard rules in fourth edition it is likely just ball. thus (1) penetration and *1 damage with no modifiers on base damage.

In third edition you could have used the semi armor piercing modifier (1.25) penetration and *1 damage with no modifiers on base damage optional rule if you wished and still be RAW.

Of course as GM you are free to do and use any rules you feel like.
__________________
--
GURPS spaceship unofficial errata and thoughts: https://gsuc.roto.nu/
weby is offline   Reply With Quote
Old 05-01-2016, 10:39 AM   #5
Fred Brackin
 
Join Date: Aug 2007
Default Re: M855A1 ammo- AP?

Quote:
Originally Posted by acrosome View Post
Frankly, reducing damage by 0.7 and dropping the size modifier by one (pi++ becomes pi+, etc.) is excessive for a human target.
It's excessive for no-living targets too. One you factor in IT:Unliving there's almost no level of DR for which AP is not inferior to regular ammo in dame to vehicles.

Gurps needs better rules about non-deforming bullets (among other things in the area).
__________________
Fred Brackin
Fred Brackin is offline   Reply With Quote
Old 05-01-2016, 11:13 AM   #6
Ulzgoroth
 
Join Date: Jul 2008
Default Re: M855A1 ammo- AP?

My impression is that the treatment of AP is what it is because they didn't want to use a fractional penetration factor. I can't see another reason for the base damage reduction, anyway...

So I'd suggest handling it as no reduction in damage but a (1.4) or (1.5) pen factor if you're willing to.
__________________
I don't know any 3e, so there is no chance that I am talking about 3e rules by accident.
Ulzgoroth is offline   Reply With Quote
Old 04-17-2019, 08:03 PM   #7
Icelander
 
Icelander's Avatar
 
Join Date: Mar 2006
Location: Iceland*
Default Re: M855A1 ammo- AP?

As far as I can determine from those ballistics tests I can find online, the M855A1 (and the CBC 5.56x45mm SAT Improved Performance, which is a Brazilian-made equivalent) penetrate as AP in GURPS. That is, they penetrate steel far better than M193 or M855 rounds, even better than M80 ball in 7.62x51mm, but not as well as APHC rounds like the M995.

Unless the terminal ballistic tests in gelatin are unrepresentative of actual performance, however, the M855A1 does not suffer reduced wounding for being AP. It should perform similarly to M855 from 20" barrels from the 14.5" barrel of the M4, even possibly somewhat better.

Personally, I don't see any harm in assuming that Mk318 SOST, M855A1 and a number of advanced rounds being adopted in the 2010s simply represent a TL advantage over typical TL6 and TL7 FMJ and AP rounds. CAD and CNC technology, ever improving propellants and the use of more expensive materials than simple jacketed lead ball allows optimizing rounds for their intended role and improving penetration doesn't automatically reduce wounding.

The published performance of M855A rounds seems to justify Dmg 2d+7(2) pi+ from 14.5" M4 barrels, though at longer ranges, the pi+ would be reduced to pi (as carbines in ordinary 5.56x45mm ball become pi-).
__________________
Za uspiekh nashevo beznadiozhnovo diela!
Icelander is offline   Reply With Quote
Reply

Tags
high-tech, modern firepower

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Fnords are Off
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 11:24 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.