11 replies to this topic

[zanes]

Hi, This may be outside the scope of this forum, but here goes;

In films there are frequently sequences where weapons or firing fully automatic bursts with muzzle flashs. However, with blanks you must fit a bfa to the muzzle in order to reach the required pressure. This would remove the flashes however. With live ammo th flashes would be there, but there would be lead flying everywhere.
how do they do that? Do they use choked barrels or is there sumat I am missing here?

[lord_dranack]

I don't know about films, but I do know that in historical re-enactments with muzzle loading guns they load a charge of gunpowder then put in a square of tissue paper and ram it to provide the confinement. In gannon they use grass or toilet paper wads. I knowthis isn't what you are asking about, but it may be of interest.

[zanes]

hmmm yes, I've always been intrested in re-enactments with muzzle loaders- We have a local club that occasionally puts on re-enactments wit muzzle loaders- great fun

[lord_dranack]

A while ago I almost got involved in the sealed knot with an artillery regiment using blank firing 3 inch cannon! unfortunatly there was too muck traveling involved, and it would have been too big a commitment...

Edited by lord_dranack, 19 December 2003 - 04:59 PM.

[The_Djinn]

Zanes I expect Adamw will be able to give you some info re the auto weapon fire as I gather from his posts that he is in that line of bussiness.
I do know that we found an issue fireing live rounds with a silencer attached on a 9mm semi auto weapon that there was not enough blow back preasure to load the next round but as to how they achieve it with blanks on an automatic weapon I am at a loss.

[adamw]

They use something similar to a BFA, but it is a section with a hole in it welded or screwed into the threaded barrel. This can be used with normal blanks. This requires a proper armourer with a Section 5 firearms license since the weapon is in theory, capable of firing live rounds if the adaptor was to be removed.

Another way is to use a replica gun which is pre-made to use blanks only.

[zanes]

Thanks, I was just curious as we often go on exercise and we're always firing blanks- unfortunately we only have one LSW

Still- even straight pull rifles are very fun

[Stuart]

So, we dont even get to play with LSW's in the Air Training Corps

[zanes]

yeh, there again you get to fly planes!

[Arthur Brown]

Remember the baddies always have the half empty magazine of mis-shaped rounds, and Bond always has infinite reserves of target designated, guided rounds.

Some shots exist only post production, if you are sad enough you will see the same muzzle flash repeatedly. --- A former coleague of mine worked on early (pinewood) Bond films putting the shots onto the soundtrack

[Helmetfire]

OK, first the basics...Stick with it.
All automatic and semi-automatic weapons cycle their actions by one of two methods.
1) Recoil. Remember Newtons Third Law of Motion: For every action their is an equal and opposite reaction. In practice this means that if you are firing a 9mm Machine Pistol (Uzi, Mac10, HKMP5K etc) using standard NATO 9x19 rounds, and that round generates 341 ft lbs of muzzel energy, then the bullet has, in theory, the ability to move an object weighing 341lbs 1 foot. Remember Mr Newton. Well under this Law 341 ft lbs of energy are also pushed back in the other direction, that is, into the weapon and shooter (Felt Recoil). It is this rearward energy that causes the Bolt Group to retract and cycle the next round into the chamber.
2) Gas Blow Back. Putting it simply; half way down the barrel their are one or two very small holes. These holes "Port" some of the hot gas that is produced when the propellant in the cartridge case is ignited down to a Gas Regulator (valve), which in turn re-directs it to a Gas Piston. This piston then pushes the Bolt Group rearward in the same way as #1.
"OK" I hear you say, "what the hell has this got to do with blanks".
Well if you are not firing a projectile, then you do not have any recoil or high pressure gas to make the weapon go ratta tat tat... So here is what they do.
In the early days of film bad guys, the studios would use live fire weapons that had a steel plug inserted about 2/3rds of the way down the barrel. This plug had a number of holes drilled through it so that the back pressure could be regulated and also to give a good muzzel flash. Nowadays things are a little different, probably due to a few people getting shot on set. Weapons now can ONLY fire blanks (unless of course the are still using old kit). The barrels when made, are only bored out part way from both the muzzel and breech ends. This leaves a solid section about 2/3rds of the way down. This section also has holes drilled through it for the same reason as before. Also the Bolt Group is made of Ali instead of steel (less weight), and the Recoil Spring (which controls bolt movement) is a lot weaker. Result: You can now go Full Chatt while using blanks.
As a side note: A BFG (blank firing attachment), is just that. It is a piece of kit that you stick in/on the end of the barrel of a live fire weapon so that the action will cycle with blanks.
I hope I did not bore y'all to much with this and that it helps answer the question.

No, This is NOT a blank firer!

Edited by Helmetfire, 09 September 2004 - 02:53 PM.

[burrelly]

I run a military training company and we often have an armourour on site with a full auto bren gun.

http://www.hawkfx.com/images/faq.gif