Well, here's another piece of creative fiction!

[CINDERS]

Attachment 77828Was just thinking that Paul as there would surely be allot of unburnt powder going out the barrel but I can see where this is going as next week they will have a 100 rounds of this special ball ammo made for the SAS for use only in the cut down version of the SLR.
I may have a quick look through my 40th Anniversary of the SAS by Mick Malone who actually served in Vietnam with the Regiment and see if Mick mentions anything about weapon mods like this I have spoken to Mick on many occasions really nice chap sells military books now for a crust.

[browningautorifle]

would that even cycle properly in real life

All I can say is mine did. I don't recall opening up the gas port either. I may have closed the gas regulator a bit though...

[tankhunter]

And if you check the 'Bargain Basement' Section of this 'Seller's' website. There are also surplus K98k Bayonet frogs Ex German Border guards on 'offer'!!!

Mmm it is documented that post war Border Guards used Ex Wehrmacht Weapons & Equipment in their Early years. Because there was MOUNTAINS of the stuff about! So WHY would they have NEW 'unissued' UNMARKED bayonet frogs?............

I think he probably forget to mention that they were intended for the 'Border Guards' in one of the Factories in India, or china. Who make them for the
Re-enactment Market!!!....................Well, Hush My Mouth!!!..... This has raised a VERY important question: Would you buy ANYTHING from this Seller?...........

[Flying10uk]

Didn't/did the Australian SAS use the M16 rifle like it's British counterparts have had a long history of doing so?

[browningautorifle]

the Australian SAS

They were a bunch of pirates that had a whole assortment of things. Whatever they needed. They used SLRs, M60s and M16A1s.

The Aussie rifle section used two M16A1s, one M60 and the rest were SLR. That was from lessons learned in RVN and that was during 1977.

[CINDERS]

Our forces only long term borrowed stuff from the US forces in VN BAR you should know that, I should imagine our guys here taught Peter Laidler a thing or two about squirreling stuff away.........!
Pirates indeed Jim!

[browningautorifle]

long term borrowed

Pardon me, long term borrowed...pirates indeed!

[mrclark303]

Didn't/did the Australian SAS use the M16 rifle like it's British counterparts have had a long history of doing so?

If you google Vietnam SAS L1A1 F10, you will find some fascinating images of ANZAC SAS L1A1/Mods, some simply removing most of the FE and adding full auto capability.

Others involved considerable surgery, with relocated gas blocks short barrels, or grafted on grenade launchers.

All modified in country and available in a miriad of different individual versions.

Some used the L2A1 as the starting point. All in all, a very interesting inch pattern side story.

[Peter Laidler]

I feel sure that I/we have skated over this point sometime in the past. And before I go on further, I have to admit that my practical experience here is restricted to the identically principled, gas operated L4 Bren as opposed to the L1A1, subject to the thread in question. The reason of course is that in a lab. Range classroom, it’s simpler to illustrate ever shortening barrels using a quick-change barrel Bren than a rifle! Another point is that I have only ever used 7.62mm NATO ball ammo so this waffle might not apply to you hand loader nerds. Additionally, please forgive me if you find some of the science over simplified. It’s meant to be……

Right, let’s start……. But before we do I should remind you that this is going to get a bit technical so might I suggest that you pit the kids to bed, set the TV to a cookery programme for the wife and sit down with a large glass of fine Scotch.
Right……., Gun in a layer and a round is fired. As the bullet passes the gas port an explosive force of gas follows the projectile and a small portion of this gas is immediately diverted down to impact on the face of a piston. Whether it is diverted onto the piston face via an angled gas plug (Bren) or is directed directly onto the piston via an angled gas path (L1A1) is academic here. But impact on the piston, it does! But there’s more……, a LOT more. That huge blast of gas only remains a huge blast of gas while there is a projectile in the barrel – that’s obvious isn’t it? We’ll come back to that important point later.

While that blast of gas is doing its thing to the piston face it’s doing something else too……… It is imparting energy called INERTIA to the piston. And, once again, it can only build-up this influence on the piston while there’s a bullet in the barrel. When the gas is gone, diminished, vented, neutralised, resumed atmospheric or whatever else you want to call it - the gun is on its own. And anyone that tells you different is either spouting fuzzy logic or has just invented a form of perpetual motion. You don’t get anything for free in small arms mechanisms

This inertial energy that is being imparted to the piston and working parts is going to be doing an awful lot of work for the next 1/10th of a second. And it gets WORSE, because for the first 3/8th “ of its movement rearwards is redundant due to what we call mechanical safety. And if you thought that was bad, there’s worse to come because only after the bullet has left the barrel can the Bren/rifle breech COMMENCE to open. That isn’t OPEN, that’s COMMENCE to open – not quite the same thing!

Going on a bit now…… That gas has had to impart into the working parts sufficient energy to overcome the following things that are acting against it.
Compressing the strong poundage return spring
Friction of unlocking breech block and primary extraction
Overcome friction of top rounds from a loaded magazine acting on breech block
There’s probably a few other things that I have forgotten too……..

We have established that the huge blast of gas is only that while the projectile is in the barrel containing it . So what’s going to happen when you start to shorten the barrel that the scientist at FN, Enfield, Lithgow, Long Branch et-al have considered its optimum? I’ll tell you. After the first inch you will start to close down the gas plug and every half inch after that you’ll start to find that the gun regularly won’t cycle fully. You can cure this by closing the gas vent down (L1A1) or opening the gas plug (Bren). But get past a couple of inches and you have effectively run out of options…… It would not operate or function correctly no matter what we did. And guess why this was? That’s right…………

As the barrel is shortened, so is the time that the bullet is in the barrel to assist and therefore to impart the time/distance that the huge blast of gas available to impart inertia to the piston is diminishing on a logarithmic scale . And it’s this logarithmic scale that quickly eliminates all of the options such as closing the gas regulator or opening the gas plug.

So what do I think when I see these hybrid pieces of someones practical imagination? The irony is that we only see pictures. We never see technical reports or film of them operating. I wonder why?

[Vincent]

The gun in the first post looks to have the standard gas system with a shortened barrel. I agree with you, Peter. It's not going to function properly.

Cinders posted this picture in another thread. The gas system looks considerably shorter (top right pic).



DSA sells some short gas system FAL type rifles that have a good reputation. DS Arms - Rifles