Introduction: The D3 Lego Semi-Automatic Handgun

Picture of The D3 Lego Semi-Automatic Handgun
This is the second semi-automatic gun I have built, and because this gun is larger than a pistol, but smaller than a rifle, I have called it a 'handgun'. The gun has a 30+ foot (depending on rbs used), and has good power and accuracy. It has a 6-round magazine, but the capacity for rubberbands in the gun is more than that. The full reload time (putting rbs on trigger, adding on the top, putting on and locking the magazine, putting rounds in the mag, and putting the mag rod and rbs in the magazine) takes about 1 minute and 40 seconds (my record), which, for semi-automatics is very quick (some can take as long as 5-7 minutes). The D3 has many new features which were not included in the D2, such as:

-It fires a (2x3)F round, which is larger than the (2x2)F round fired in the D2 (meaning it has more stopping power)
-It is a smaller gun than the D2, in height and length
-More comfortable handle
-More durable gun design (meaning more rubberbands than 6 can be added in the gun)
-It features a leaf firing sight (like the M16's sight), as well as a tactical rails
-The magazine is easier to put into the gun and remove
-The magazine can lock inside the gun, using a lever
-The gun looks better than the D2 (I think it kind off looks like the Thompson Submachine Gun, but thats just me)
-Improved reliability when firing (no jamming-where the round gets stuck in the gun- and greatly reduced chance of double-fire- when 2 rounds or fired off at almost the same time)
-Simpler design, meaning it is easier to build
-Shorter reload time than the D2
-The firing system has also been simplified, with only 2 gears on the side, opposed to 4 (in the D2)



Soon I will start work on the D3.1 . In this mod, I will fix some issues with the top of the gun, the area around the magazine, the magazine lock will be improved, some kind of safety will be added to prevent you from accidentally pulling the trigger, and a larger round capacity will be added to the gun (maybe 7 or 8 round capacity)

Step 1: Handle

Picture of Handle

This is the hand hold on the back of the gun.

Step 2: Rubberband Holder+ Magazine Lock Mechanism

Picture of Rubberband Holder+ Magazine Lock Mechanism

For magazine lock mechanism, you will need a very small piece of tape (as in the smallest that you can possibly tear off- maybe like 5mm in length, and whatever the width of your tape is)

Step 3: Magazine

Picture of Magazine

This magazine holds 6 (2x3) bricks (each of which have a flat piece on top).

Step 4: Adding Onto the Handle

Picture of Adding Onto the Handle

This step begins to add a top onto the handle.

Step 5: Trigger + Part of Firing Mechanism

Picture of Trigger + Part of Firing Mechanism

Fairly easy step.

Step 6: Building Up the Back

Picture of Building Up the Back

This just creates a base for the gears to go.

Step 7: Some More of the Firing Mechanism

Picture of Some More of the Firing Mechanism

This creates the firing gears and creates part which stops the 'L' shaped piece from going too far back.

Step 8: The Rest of the Firing Mechanism

Picture of The Rest of the Firing Mechanism

This finishes the firing mechanism.

Step 9: Building Up the Back Some More

Picture of Building Up the Back Some More

Short, easy step.

Step 10: Bottom Magazine Holder Part 1

Picture of Bottom Magazine Holder Part 1

This is the area will hold the magazine in place inside the gun.

Step 11: Bottom Magazine Holder Part 2 + Assembly of the Bottom

Picture of Bottom Magazine Holder Part 2 + Assembly of the Bottom

This finishes the bottom magazine, attaches the piece made from step 10+11 to the main body, and attaches the piece made from step 2 to the main body.

Step 12: Firing Runway + Building Up the Sides

Picture of Firing Runway + Building Up the Sides

This fills in the middle of the gun, finishes the firing runway, and builds up the sides of the gun.

Step 13: Top of Gun + Sight

Picture of Top of Gun + Sight

The top of the gun only goes up to where the magazine is, and after that there is space so that the round can easily leave the gun. The sight up of: the tactical rails, the flip up 'bunny ears' rear sight, and the forward sight. (This sight is supposed to work like the M16 sight.)

Step 14: Counterweight Rubberbands

Picture of Counterweight Rubberbands

The rubberbands attached to the trigger to keep it from firing.

Step 15: Magazine Placement + Building the Ammo + Magazine Rod

Picture of Magazine Placement + Building the Ammo + Magazine Rod

Put the magazine in so that the notches are on the sides. The ammo is 6 (2x3) pieces, each with pieces on the top.

Step 16: Loading Part 1 (Firing Rubberbands)

Picture of Loading Part 1 (Firing Rubberbands)

The D3 needs 6 firing rubberbands. NOTE: Before loading the rubberbands or ammo, you need to put a lubricant (vaseline) on the firing runway, the sides of the magazine (on the inside of it) , each ammo piece all around it, and on the magazine rod (on the part which will make contact with the ammo and inside of the magazine)

Step 17: Loading Part 2 (Loading the Magazine)

Picture of Loading Part 2 (Loading the Magazine)

Very simple. Put the 6 rounds into the magazine (in the hole in it), then, put the magazine rod on top of all of those, and attach the rubberbands on the magazine to it.


YouNeverKnowItUntil (author)2014-04-25

it's a bullpup short barreled rifle

TheYukomaru (author)2012-06-30

Could you tell how many of each piece so I can get all the pieces I need?

meaner6788 (author)2011-12-26

if you don't have the ball things do you need them?'

meaner6788 (author)2011-12-26

hey bitterberry do you take apart each gun to make the other or are you a lego hoarder

ttaladay (author)2011-08-11

the only piece i don't have is that tiny gear. does any one know where i can get one?

meaner6788 (author)ttaladay2011-12-26

go to and try to find "pick a piece" under catorgories, i think. real cheap like under $1

jaw656 (author)2011-05-30

Awesome!!! This is an awesome gun! It looks cool and has a sweet mag! This gun can definitely rival K'nex guns and it is semi-auto which is great. I built my own sight that kind of looks like a reflex sight and added the mods which are great. I gave this Instructable 5 stars!

jaw656 (author)2011-05-30

What kind of "studs" are you talking about? Like the ones that you collect in Lego games or like a 1x1 piece?

The Nomlack (author)2011-01-06

im looking for a lego gun that has NO GEARS. please help
by the way nice gun 4.5. 4.5 because you used gears.

The Nomlack (author)The Nomlack2011-01-06

thats semi-automatic

roockie44 (author)2010-07-17

i found out that if you put all 6 rubber bands on you need 5 on the trigger as a counter weight so it doesnt go off accidently

stuntdude47 (author)2010-06-07

What Size rubberbands do you use and where do yo get them

narutokid201 (author)2010-05-18

um if this pictures right, it should be a one x nine

zixx65 (author)2010-05-11

hey dude..... i like that idea u gave to us right now but im going to make one of my own

Alikz182 (author)2010-03-13

 This. Is. Amazing. This is possibly the best build on Instructables, and its even semi-automatic. I am a big fan of yours, bitterberry, and i hope to see more lego guns coming soon!

cantbesaved (author)2010-01-29

can you please pm me a full, accurate parts list? im ordering the parts from bricklink so i can make it

Trisc5 (author)2009-09-22

where do the rubber bands go at the end?

Bitterberry9 (author)Trisc52009-09-22

you need to pull the rubberbands from the front of the gun, to where the firing gears are, and put it on a gear tooth towards the back of the gear

imatthew32 (author)2009-08-27

very nice ! but im planning to make it but the handleis just a full slant can i change it?

Bitterberry9 (author)imatthew322009-08-27

ya sure

Jesus. (author)2009-08-23

hey bitterberry when i put more then 3 rubber bands on it it fires all of the bands at once, any help??

Bitterberry9 (author)Jesus.2009-08-23

you need to put on more counterweight rubberbands (step 14) (the ones attached to the trigger itself). you must be using really strong firing rubberbands....

Jesus. (author)Bitterberry92009-08-25

yup i was, now i have you semi auto crossbow and with 2 #64s it could shoot 75 feet!!!!!!, but it could only shoot 3 shots, i could'nt turn it back for the forth shot!!

Bitterberry9 (author)Jesus.2009-08-25

WOW. 75 feet?!?!? nice. In terms of the only 3 shots theres not much I can do about that unfortunately, I used different rbs. I find it amazing that you can get 3 sets of 2 #64 on there at all though. WOW.

jonathanrockshard (author)2009-08-22

this gun is awesome unfortunately mine jams occasionally

you need to lubricate all the pieces to keep it from jamming. Another thing I've found (which I havent included in the instuctable unfortunately) is that if you raise the top piece (the one with the sight) a third of a brick up on top of the gun, so that when the ammo loads it also goes a third of the way up more then it usually would, and that completely eliminates jamming (I used this method in my C4 'ible)

darthpotato1 (author)2009-08-11

why woulld you need tape

because of just how the technic pieces work, otherwise it sometimes moves out of place

101man (author)2009-08-09

this is really good what would u say is the best lego gun with instructions online

Bitterberry9 (author)101man2009-08-09

idk, it really depends. instructables has very few lego guns, but sites like are good, and on youtube channels like Caspalll's he posts instructions videos for some of his guns. there are also tons of instructions videos for lego guns online.

101man (author)Bitterberry92009-08-10

i know i have seen lkmachines ok i will look at caspalll

brownfamily52 (author)2009-08-08

I like the gun, but when i pull the trigger it fires all 6 rubber bands at once, but i know that they're spaced far enough apart on the gear before I put the top back on.

o, thats really easy to fix. Its because the rubberband that you're using as acounterweight rubberbands (the ones you put on the trigger) are too weak, so you need to add a couple more. If it still doesnt work after that, it means that the rubberbands that you're using as firing rbs are too powerful.

brownfamily52 (author)2009-08-06

how many studs long is the axle in the first picture?

its 8 long, sorry for the lack of detail in this one, ill be dealing with that soon

jj3502 (author)2009-08-02

I just finished it but its getting jammed?

Bitterberry9 (author)jj35022009-08-02

it could also mean that the RBs you have on the magazine rod are too strong. (and BTW, don't use very much vaseline, just a very small layer to lubricate it)

Bitterberry9 (author)jj35022009-08-02

right, you need to do a few things to fix that: first of all get some sort of vaseline product and lubricate 1) the firing runway, 2) the ammo (all around), 3)the sides of the magazine 4) the brick part of the magazine rod which will make contact with the ammo and the sides, 5) the inside of the top piece, where the ammo will make contact witb the top. Another thing you may need to do is adjust the rubberbands you are using. You may need stronger firing RBs, which will be able to overcome the pressure on the ammo from the top being on. Lastly, if all of that still doesnt work, then loosen the top SLIGHTLY, as in just slide a fingernail between it and the gun, so that the ammo will move up slightly and should fired properly.

Oblivitus (author)2009-07-27

This is really nice for lego, keep it up!

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