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Modifications to a pistol to allow blank firing? Answered

 What  modifications are needed to allow a semi-automatic pistol to fire blank ammo?
The reason I ask is that on various film prop sites I have come across a photo of a gun, ( for an example see accompanying image), and the phrase, 

"Note how the gun has clearly been blank converted."

I can guess at the reasons but does anyone know?

(Don't even bother trying to google this.. .you will get thousands of pages on how to convert a blank gun to fire real ammo.)

This is from the film, Heat.

Thank you.



Best Answer 8 years ago

Brandon Lee's death filming "The Crow" has changed the industry forever. It used to be that 100% real, unmodified firearms were commonplace, and 'standard issue' crimped-brass case blanks were used when guns needed to be fired. Not anymore-- studio films with legitimate armorers only use modified weapons-- weapons that cannot accept regular (lethal) ammunition at ANYTIME. It is believed that Brandon Lee's death was caused by the initial loading of a real, but primer-only cartridge that pushed a real bullet into the barrel of a revolver. A subsequent squib-load (one that produces muzzle-flash and report, then actually shot the bullet at near full-velocity into Brandon Lee.

"Note how the gun has clearly been blank converted." refers to the non-standard barrel as installed on the firearm used by Al Pacino's character-- a stock barrel would be stainless steel in color and have a rough texture-- something that 1911 owners/shooters/gunsmiths would know to expect, as a consequence of the locking-lugs dragging across the top of the barrel hood/chamber. The armorer who built this particular gun used a non-standard (probably non-stainless) barrel that does not engage the locking lugs (as tightly.) The replacement barrel was undoubtedly short-chambered to prevent the inclusion of real ammunition, and/or restricted, to dramatically increase the blow-by gasses for action cycling with squib ammunition.

The 'political problems' aside, I believe 'Heat' was the best gun-film of all time. IMHO, it had the most [consistently] accurate representation of firearms used in tactical situations by either side. 'Political problems' is the fact that the LAPD would not have allowed the use of ALL those different types of firearms in the film, Al's character included.

Short summary-- real Colt Officer's ACP, but apparent barrel replacement.

I know this is an old thread but to answer all of the above.........
1. semi-auto pistols have a barrel restrictor to create the pressure needed to to cycle the firearm, the locking lugs or block are removed to create a blowback operation and to allow the barrel to lower into battery (that is to allow a cartridge to be fed). This is becouse with a live round the barrel is pushed to the rear upon firing as the bullet passes through it but with a blank, the barrel is pushed forwards with the pressure against the inside of the restrictor.
2. Auto and semi-auto rifles require little modification apart from the restrictor with the exception of some like H&K firearms that have locking rollers in the breech block.
3. some countries (only a few) require the short chambering of a firearm, most are original calibers.
4. Blank firing replicas are not often used in professional movies as they are not always reliable and are weakly constructed. In addition most replicas have a discharge from the top of the barrel not the front.
5. I have been a professional film armourer since 1994 and have never 'replaced' a barrel, anything that can chamber and fire a cartridge is clasified as a barrel and therefore requires a licence to possess and also to manufacture!
6.The visual differences are minimal, Glocks and SIGs which have a large barrel block at the breech are the easiest to spot as this has to be ramped and often stays silver as it wears against the slide. Other givaways are camera angles which look directly into the barrel where the thread for the restrictor can be seen.
7. It is worth noting that all firearms require a slightly different modification and it should not be attempted without good prior knowledge in gunsmithing unless you want to destroy your firearms and possibly your hand and eyesight as well. Blanks come in varying strengths and vary between batches making in neccessary to re-calibrate the size of the hole in the restrictor to prevent over/under pressure.

I was also the manager of the company that provided the military instructors for Heat, among many others. http://www.imdb.com/name/nm1747133/

Dear Milspec,

Thank you for your comprehensive answer.

I found it unbelievably interesting, causing me to read around the subject, eventually settling on Newton's third law.

I have an interest in guns but only a shallow depth of knowledge, so forgive me if I go point by point at a ridiculously basic level in order to understand you.  . .  But please do not feel obligated to answer my lengthy, pointless queries:

1: From your answer and a bit of reading I picture this . .  The barrel would normally be pushed back and down by recoil, thus releasing the slide . . . But because of the restrictor,  the gasses leaving the cartridge are resisted and this puts a forward pressure on the barrel which arrests its normal operation. Before the the bullet has left the barrel, the slide is pushed back by blowback from the expanding gasses because it is not held in by the lugs.

Is that all correct ? I hope so, my head hurts.

2: Even though the barrel has not been changed, as you stated, then does Trento's anwer still stand true; the fact that because there are no signs of lug- induced scratches then it is clearly a blank firer.

If not, then are there any visual clues that can be taken from that photograph alone that this gun is a converted to fire blanks ? ( my original question).

3; From your answer is it correct to say that to convert  a recoil-operated pistol to fire blanks, let's say a Colt 1911,  would just need to have it's lugs filed off and a restrictor fitted.

4; Finally, By what means does the restrictor fit into a barrel; I mean  does it have to be threaded ?; I tried to find images of 1911 barrel restrictors but could not.

I do not want to do this to a gun, I just became curious about the process.

Kind regards,



I'd be surprised if you're still
tracking this thread, but to take your questions in order:


When firing a live round in a 1911
pattern pistol, the burning gases generated in the brass casing push
the bullet down the barrel and simultaneously push the casing against
the slide face, forcing the slide rearward. Lugs inside the top of
the slide are mated with corresponding lugs on the top of the barrel,
drawing the barrel rearward and keeping the slide and barrel locked
together long enough for pressures in the barrel to drop to a safe
level. At a certain point, a link located below the barrel cams the
barrel downward, unlocking the barrel from the slide. The barrel
stops it's rearward travel while the slide continues moving to the
rear. The base of the brass strikes the ejector (located on the side
opposite the slide opening) as it protrudes from the breech face,
throwing the spent round clear of the slide. The slide hits it's
rearward limit and is forced forward by mainspring pressure. As it
moves forward, the slide strips a fresh cartridge from the magazine,
pushing it into the chamber of the barrel and pushing the barrel
forward. The barrel's link cams the barrel upward mating it's lugs
with those of the slide, locking the pistol into battery allowing it
to be fired again, provided the trigger group has reset. I know I've
seen slow motion animations of the process. YouTube?


The restrictor in the barrel is there
to allow the generation of pressure equal to that created by firing a
live round, forcing the blank casing against the breech face, pushing
the slide to the rear.


The barrel hood of the pistol in the
photograph shows a gap between it's forward edge and the forward
opening of the slide. This would not be acceptable in a pistol firing
live rounds.


I don't think so. The barrel need to
lock to the slide allowing the slide to draw it rearward allowing the
link to drop it out of battery. The barrel must move to the rear and
downward to allow the next round in the magazine to feed properly.
I'd also worry about sufficient clearance for the barrel hood inside
the slide without modification of the slide. I'd want someone with
specific experience to make the modification.


Good question. I want to say that a caliber specific plug is fitted and tightened against the inside of the barrel, but I can't say where this came from or how it works specifically.



From what little i know, with pistols like a Glock or Sig, the top of the reciever has to be milled at an angle to allow for the slide to cycle easier, since the lack of an actual projectile means that blank rounds have no where near the amount of gas needed to actually cycle the slide without modification. I also know that back in the day, .45ACP blank rounds were hard to find, and Star Model B or other 9mm chambered 1911's were used. Butttt thats all i know about it, i was actually looking for more information myself.

I looked over the pictures as well and I couldnt find anything out of place  aside from the barrel not being stainless but I have seen park'd barrels before. It just looks like a commander sized 1911 to me ( a nice one at that).

It is my understanding that prop guns, 45 ACP caliber prop guns specifically are often fitted with a 9mm barrel. This has something to do with the gun reliably cycling with blanks in that caliber, maybe thats what has been "clearly" modified on this firearm.

There are a number of systems to convert a gas operated semi auto to fire blanks. They all seem to involve a type of barrel restrictor which allows the pressure to build to a level high enough to operate the reloading mechanisms, but not high enough to damage the firearm.
When these are used by the military etc. for training purposes, there is usually a red "plug" showing at the muzzle. This makes it "clearly blank converted" for safety purposes.
I have never seen this on a movie prop (or in your attached pic), so maybe  they are refering to something else. Not all semi auto firearms use gas pressure to reload (I think), so maybe there is a different conversion kit, but I still think it would be internal.
I have seen blank ammo in movies though. It looks like the bullet has been removed from the case and replaced with a lump of red wax. (Red again for clear blank identification).

As a note-- shoulder-fired rifles (using rifle ammunition, not carbines using pistol ammunition) are usually gas operated, due to the design limitations of having a light-weight weapon that fires a high-pressure cartridge; i.e.: (the chamber must remain locked until the bullet has exited the barrel and pressures have dropped.) Since military training blanks have no bullet, there is nothing to raise the system's pressure high-enough to cycle the gas piston, as in an M-16/M-1/M-14/SAW a blank-firing-adapter (BFA) is needed to (somewhat) block the barrel. The BFA is also there to literally cause the shooter more harm, should he 'accidentally' load real ammo during a training exercise.

At one point I owned more than 130 handguns, and only one (type) was gas operated-- the Heckler Koch P7. The main bad-guy in Die Hard had a nickel plated P7 M13 in 9mm. Although produced through about 2003, this firearm is not common-- they are expensive, and being all-steel they are heavy and have a weak finish (delicate bluing.) Only one other handgun that I know of, produced by Wilson Combat uses a gas system... and it didn't sell all that well. Reliability is often compromised by poor maintenance.

You are correct, in that-- in prop guns, recoil operation is REPLACED with blow-back operation based on gas expanding in a chamber (physically restricted barrel.) However, since it is not acting on a secondary piston, it technically would not be considered a 'gas system.' A gas system would require a 'vent' in the barrel, which actuates a secondary piston assembly (or on an AR-15/M-16 the bolt riding in the bolt-carrier IS the piston.)

From the photo you include there is no indication that the gun is firing blanks or real ammo.

For an actual live ammo firing hand gun of the semi-automatic variety to fire blanks as a semi-automatic it must be converted to allow the blank cartridge to move the slide back and eject the spent round, cock the hammer and feed an new round.

For this to happen in a gas operated gun it is simply a matter of partially blocking the muzzle or the gas ports.  A gas operated gun operates by venting a portion of the hot high pressure gases from the gun powder to a piston that slams the slide back.  I've used an M1 rifle in this manner in war games in the Army.  There is a plug that is clamped over the end of the muzzle and you can fire blanks just like real ammo.

In a gun that operates the slide by the action of the recoil it is much harder and the gun must be modified to operate by gas operation some how.  I've not had any experience with these types so I don't know how they work.

What I expect is happening is that most if not all of the guns used in the movie bidness are manufactured as blank firing look alikes that are undetectable from the real thing without closer inspection.  And I expect that the photo above is of a replica gun instead of a real hand gun.

Thank you both for replying.

I'm still a bit puzzled though.... 

This is the gun actual used in Heat ; A Colt M1991A1 Series 80. which I believe is recoil operated, on the site it said about the original picture above,

" Note how the gun has clearly been blank converted."

A lot of real guns are converted to fire blanks because there is not a commercially available replica for all models.  
I guessed that the converted gun would maybe have a weaker spring because there is less recoil , ( I don't know if this is actually the case ?), but from the comment ( very respected site; imfdb.org ) there appears to be an external clue.

Is it possible that crimped blanks need a larger ejection port? ,(this seems a bit unlikely but I'd thought I'd ask and get it out of my head.)

Best Wishes.


I don't see anything unusual in this photo, except there sees to be something under the trigger.  It may be a shadow but enlarging the photo doesn't help.

The ejection port is not visable in this photo.

Why don't you post the question on that website and bring the answer back here.

 Hey, thanks for taking the time to answer.
I meant the original photo, above, (that was in the film too),  you can see the ejection port in that one.
I didn't ask on the site because it involves having to register but if my brain doesn't shut up I may just have to.
You could be right ; it could simply be an error.

Anyhoo, if I find out, I'll repot back here pronto.

I looked at the site that you got the Heat photos from. Googling colt m1991 a1 compact series 80 revealed a heap of sites for people selling pistols, which contained alot of photos from every angle. I can't see anything different from the Heat version. Now I can't sleep at night.
Let us know if you find anything.

That's a nice website.  But not everything posted on the internet is actually correct.  You must allow for some errors.