bullet holes

Try a hot needle for small arms or small scale. Try a soddering iron with a fine point for 1/48 scale bombers and Flak damage... Add a light amount of flat black paint around the hole after painting, and there you go!

I think it really depends on the type of material you want to depict the holes in.
Some of the most convincing holes I've seen done in what is supposed to be sheet metal or similarly thin metals (like on aircraft, or exhaust covers and stowage bins on armored vehicles) were accomplished by thinning the plastic to a paper-thin thickness (about right for the scale) and then picking open holes with the tip of a #11 X-Acto blade or pushing holes in with a NON-heated pin. This thinning technique looks particularly good for creating flak damage.

The problem with heated pins and soldering irons is that you melt the plastic, resulting in rounded, soft edges to your holes, which in my opinion does not look realistic.
The only exeption to this would be AP (or HE, I can never remember!) hits to thick armor, which does melt the metal and give you that raised lip or ridge around the hole, which you'd get with a heated pin or soldering iron.

Bullet holes in wood are a whole different story...splintering, jagged holes, etc.

I'd recommend trying out some different techniques on some scrap plastic and see which ones work for you.

Thinning the plastic is a must - then slightly tearing a hole in the thinned plastic should realistically replicate a bullet hole.
Remember, a machine gun isn't a sewing machine and it doesn't drill nice, neat round holes. You don't get a perfectly straight, evenly spaced series of holes when a machine is struck with small arms fire. Hollywood does much to make us blind to reality.........
Consider the relative movement and probable violent gyrations of both the target and the aggressor in 3 dimensions, throw in gravity, wind deflection, the tumbling action of the projectile, and vibration of the guns themselves, and you end up with a quite random "splash" of projectile impacts on the target.
Also, the bullets will tend to strike the target on a tangent - that is, on a very high angle (like the angle of skipping a stone on a pond). Not many strikes would be at 90 degrees to the path of travel, so this high angle of strike would mean that the bullet would tear an oval in the target, creating a hole much larger than the bullet diameter.
Think about the amount of battle damage you want to portray - would the battle damage be bad enough to make the plane fall out of the sky, cause a forced (but relatively controlled) landing, or will the aircraft make it back to base? Remember, a huge amount of damage would probably cause (in real life) a structural failure or an in-flight fire, resulting in something impossible to model (like a smoking hole in the ground).
My first attempt at battle damage (25 years ago) looked more like swiss cheese than a Japanese "Tony". Live and learn.
Just something to think about................
Cheers,
LeeTree

Excellent advice, LeeTree!
I remember reading about the thinning 'n' tearing technique for the first time from Shep Paine in the old 1/48 Monogram B-17's diorama tips sheet.
Learned a lot from ol' Shep and Monogram!

Now that you've got the bullet, shell or explosion damage realize that now we can peer in there and take a look about... let me find my magnifing glasses and flash light. If you're going to put your model (aircraft, armor,ship, whatever) in a show the judges will do exactly that. Open the hatch on a tank? There better be something in there. Bullet holes won't show much (realize a 50cal. type weapon will go in one side of your airplane and out the other unless it hits something solid, the entrance is a hole, the exit is where the chunks blow through if anythings hit. Flak or explosions will expose wing ribs or spar's, wireing and anything else you can think of to our vision. Deeper, Deeper into modeling insanity we go.............
have fun
G.L.

but how would u be able to thin the holes? My guess is by sanding it?

With a Dremel, patience and a veeeeery steady hand.

-fish

-I should have pointed out- you dremel out the plastic from the back/inside of the model til it's paper thin. Then follow the above directions.

-fish (again)

Thanks for the help.

How about adding bullet holes to one of the windows with a spidering stemming from the point of impact?