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Author Topic: Ballistics/Forensics Question  (Read 798 times)

Offline Andy in Germany

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Ballistics/Forensics Question
« on: March 01, 2024, 06:45:10 PM »
I have a habit of trying to make my Pulp games as realistic as possible. I appreciate "Pulp" and "realistic" aren't always in the same sentence, but bear with me. I'm working on a scenario involving a firearm, and one piece of information is two matching bullets, and being European I've never seen, let alone handled a genuine firearm, so I've got a few questions.

If you have two bullets from the same gun, can you tell the calibre? How?

How easy is this if the bullet hits a solid object like a wall at speed?
« Last Edit: March 01, 2024, 06:53:13 PM by Andy in Germany »

Offline Cory

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Re: Ballistics/Forensics Question
« Reply #1 on: March 01, 2024, 07:43:04 PM »
Most lead bullets will still be intact enough hitting any non stone/brick surface to tell with a glance, not all though. Modern steel ones seem to deform or shatter more. Rounds from a rifle are more likely to be too deformed for ID than a handgun. As a GM I'd say you need a 2+ on a d6 to id the caliber of a fired round, -1 if it hit a hard surface, -1 if it was from a rifle.

Source, I am a landlord and property owner in a place where rural stuff gets shot a lot.
.

Offline Elbows

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Re: Ballistics/Forensics Question
« Reply #2 on: March 01, 2024, 08:44:12 PM »
Yeah, depends entirely on what the rounds impacted.  If you're shooting target steel plates (which are basically hardened steel which shatters a bullet into fragments) it'd be difficult.  Almost any other material (including human flesh) you can generally tell quite easily the caliber/size of the round, if not finding a round nearly complete.

Now at a glance it may be tougher to differentiate between some rounds which are close in size/weight.

A bullet is generally defined by it's diameter (caliber if you're measuring in inches), length, and weight (often measured in 'grains' which is weird, but that's the way you measure ammo generally).

Generally the lighter the round (in grains) the higher the speed.  A normal service rifle chambered in 5.56x45 (x45 incicates the length of the brass casing which stores the powder/primer, so the larger the number, the bigger the casing) can fire rounds from 40-grain (varmint hunting rounds) up to 77-grain (longer distance rounds for marksmanship), etc.

Different kinds of rounds also appear differently in flesh/material.  A 'ball' round is intended to stay intact and simply punch a hole, while a hollow-point or defensive round is pre-cut to expand like a brass flower when it contacts material, creating a wider wound channel.  Frangible rounds are made of compressed powder/binders and are used for training or inside aircraft (as the round is unlikely to over-penetrate).

Some rifle rounds are made to expand or explode into shards on impact (like 5.56), while others tend to bend/fold/yaw, creating really nasty wound profiles (such as the Soviet 5.45x39).

In short...if the characters know anything about firearms (with their in-world knowledge), they'd be able to identify stuff relatively easily, though maybe not with great precision.
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Offline Andy in Germany

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Re: Ballistics/Forensics Question
« Reply #3 on: March 02, 2024, 08:50:47 AM »
Many thanks for the suggestions and information. Publishing isn't really on the cards; it's a method to survive the terminal boredom and excessive human interaction of working on the till for a couple of hours a day.


The story is set in December 1937, so the methods and weapons available will reflect this. There are two guns involved in the story, the Gewehr 98, with a cartridge (at least unless I find a more specialised German sniper rifle from this period) and the Japanese made Type 97 sniper rifle. The G88 used a 7.92×57mm cartridge and the Type 97 took a 6.5×50mm cartridge. Both of these are distinct from the .303/7.7mm cartridge used by the British Army at the time.


In the story the Type 97 is used to assassinate a policeman; the sniper hits on the second attempt, and the bullet that missed passes through the truck bulkhead to be found later in a damaged state when a colleague searches the truck. In a second assassination attempt on this colleague  the sniper misses and hits a pile of grain sacks, allowing the shell to be retrieved in better condition. As the intended target of the assassination is a policeman he'll automatically want to identify the bullet, and those differences are fairly easy to recognise using a caliper tool.


The Gewehr 98 is fired by a German sniper, as covering fire. It is deliberately aimed at a wall next to the assassin, in order to hinder or prevent later identification of the bullet. As the sniper is firing over a distance of about 50m and the effective range of the rifle is about a kilometre, I expect the bullet will hit the wall with sufficient force to crush it. As it's a pretty mucky dockside it would be hard to find the remains in the general clutter.

Offline CapnJim

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Re: Ballistics/Forensics Question
« Reply #4 on: March 04, 2024, 10:56:08 PM »
Here are my thoughts...

1.  The bullets likely in use by your snipers would be "ball" ammo - spitzer-pointed solid lead bullet with a copper jacket.  The 6.5 Jap would likely punch right through the side wall of the truck (i.e., it's door).  It might in good enough shape to put caliper on it if your characters can find it.  Depending on the angle of fire and what the round hits after the door, it might go all the way through the truck.

2.  Keep in mind that there was another 6.5 round knocking about at that time - the 6.5 Carcano - an Italian round.  But if they find an intact round (like the one in a grain sack), there was a very slight difference in bullet diameter.  If one (or more) of you characters are well-versed in ballistics, they could know that.  Also, the 6.5 Jap was a hotter round than the 6.5 Carcano, with a  muzzle velocity of about 2,700 fps.  The Carcano "only" left the muzzle at a leisurely pace of about 2,200 fps.

3.  The 7.95 ("8mm") round is in a class, size-wise, by itself.  The other predominant rifle rounds at the time were 6.5mm, 7.62mm or 7.7mm (or in that ball park).  If they can find the ass end of that round, they should be able to put calipers on it.  What kind of stone is that wall made of?   If a soft stone (limestone or stucco, they might find a measurable piece of the bullet, but keep in mind it could ricochet just about anywhere after hitting that wall.

Hope this helps...

 
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Offline Moriarty

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Re: Ballistics/Forensics Question
« Reply #5 on: March 05, 2024, 07:11:17 AM »
All due respect to the above answers (I’ve learned something), but how vital to the plot is identifying the bullets?
If it’s vital, I’d be inclined to allow a difference to be recognised, or the whole plot goes down the toilet. Your truck could have been carrying crates of brandy flasks, and the wall has mortared joints, behind which are stacked Bibles.

Offline Daeothar

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Re: Ballistics/Forensics Question
« Reply #6 on: March 05, 2024, 09:53:38 AM »
Sounds like your pulp campaign is sort of reminiscent of mine, more than a decade ago (Holy crap ::) ). I worked with loads of props at the time, so I provided X-Rays, autopsy reports etc (my victims were stabbed in the head) for the players to put together what was going on.

In the end though, the details went way over my players heads and I had to wield the clue-bat several times while I had provided all the required (physical) information to them.

So don't get stuck on too much detail. It's very unlikely that your players will be familiar with the minute difference between Japanese and Italian 6.5mm rounds (and therefore their characters won't be either).

My suggestion is to keep it purposefully vague and general. Because it's highly probable that you will be doing a LOT of research and preparation that will not be used or understood by your players. Ask me how I know this lol
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Offline carlos marighela

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Re: Ballistics/Forensics Question
« Reply #7 on: March 05, 2024, 10:16:32 AM »
Bullet forensics is a long established art. If you have the round you can usually work out the calibre, unless it's completely shattered.  Even partial or deformed rounds can be typed to calibre.  Find the case and there's no guess work required.  In your case there's a very noticeable size distance between 6.5mm and 7.92mm.

Matching a round to a specific weapon requires that you have the weapon in question, to match striation on the round.

There are more than one 6.5mm rounds out there. In addition to the Arisaka and Carcano, Mannlicher made one, as did Mauser. Of course you would be able to tell if was a Carcano round, especially if fired from a tall building. The magical properties of the Carcano are well known. It has the ability to pass through a human target, jink, pass back through the second target at a radically different angle, return, stop for coffee and donuts and end up somewhere on the floor of the vehicle. Then again, maybe that only happens in Texas.  ;)

Get Ernst Gennat on the case, he'll get to the bottom of it.
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Offline Moriarty

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Re: Ballistics/Forensics Question
« Reply #8 on: March 05, 2024, 11:05:34 AM »
Doest mine eyes detect a not of sarcasm, there? You’ll be wanting Andy to put in a grassy knoll, next.
:-)

Offline Doug E

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Re: Ballistics/Forensics Question
« Reply #9 on: March 07, 2024, 02:15:19 AM »
Then again, maybe that only happens in Texas.  ;)

It happens in Texas from time to time but not as often as you think.  Unlike Hollywood, we sometimes have to pause to reload.
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