Adapting firearms to function as air guns

[PerpetualStudent]

I've only recently watched "Bloke On The Range" on youtube. He had 2 videos that were fascinating and relevant to this forum's interest.

1. A springer airgun that replaces the bolt on a swiss rifle. Trigger fires as normal, but the pellet (roundball actually) fires through its own barrel inside the rifle.
https://youtu.be/nc0miOdd03Y

2. Cartridges that chamber and feed normally, but are actually pressurized vessels with a plastic (?) bullet that matches the bore. You charge each cartridge with a pump and the firing pin releases the pressure.
https://youtu.be/XTyv5Z-3JVk

I'd love to see 1 redone with C02 and appropriate sized lead roundballs. For a 22? You could even use 22 pellets. 2 intrigues me even more. Website is in french unfortunately and I'm sure shipping to the states would be not worth it. But I love the idea.

[rsterne]

The second idea is certainly not new, Brocock Air Cartridges were of that design, and more recently a company in the USA started making Big Bore airguns using a cartridge that is about the size of a Browning .50 cal MG round.... The problem with the design is that they dump all the air inside the cartridge with every shot (which is inefficient), and the small air capacity is not suited to a large caliber round, as the pressure drops too quickly into the large barrel volume....

Bob

[Multigunner]

There was a .22 round ball HPA conversion kit for AR15/M16 rifles marketed years ago. Haven't heard anything about it since but I got the impression it was intended for military training purposes and not available to the public.
It could be fed by a canister or a line and operated just as the rifle normally did including as selective fire.

There were brocock or palmer style conversions of standard .38/357 service revolvers, only a barrel liner necessary. Removing the liner returned the gun to normal function.
In the UK the Brocock pistols were made illegal after it was found that street gangs were converting them to use an 8mm theatrical blank inserted in a modified air cartridge to propel slugs with lethal force.

[koehlerrk]

rsterne, isn't that what happens with most springer and multi pump guns anyway? They have a fixed chamber filled with atmospheric air or pressurized air. When you squeeze the trigger, the multi pump dumps its whole air charge. The springer uses the spring to compress the air charge then dumps it.

HPA guns, at least my two, a Marauder and a Discovery, have a metering chamber that has a dump valve on one end and a small orifice connecting it to the main tank on the other. The idea is to dump the contents of the metering chamber with each shot, which gives more consistent shot to shot velocities.

I've handled one or those cartridge or rifles before. Honestly, I was impressed, it shot very well, and that one was a 357 bore. I think its an interesting idea,and I'd love to see it take off.

[rsterne]

What you are calling a "metering chamber" does not function as a "dump valve", only a small portion of the air inside it is discharged on each shot.... The valve closes when the pellet has only moves a small distance along the barrel, usually 20-33%, to conserve air.... You are correct that Multi-Pump Pneumatics dump all the air in the valve, but when you do that, you have a choice between low power (small volume) and high power (much air wasted).... This is because with the valve still open when the pellet exits the muzzle, all the air still in the valve is wasted, because it can no longer contribute to accelerating the pellet.... That is the exact same problem with the Air Cartridge system, you have a choice between relatively low power (for the caliber) or using a ridiculously large cartridge, and wasting a lot of air.... The MAC cartridge, in addition, has very small air passages inside it, which further limit the power.... Most .357s have about twice the FPE of the MAC rifles, despite them using a higher than usual 4500 psi fill....

It is an interesting and novel idea, but when you delve into the practicality of it.... and start comparing the actual performance to other PCPs of the same caliber.... it falls far short.... Springers, of course have a completely different operating system, using Adiabatic compression (which adds power by heating the air) using the stored energy of a wire or air spring...

Bob

[PerpetualStudent]

It is an interesting and novel idea, but when you delve into the practicality of it.... and start comparing the actual performance to other PCPs of the same caliber.... it falls far short....

I mean, I'm looking at it as a target practice tool. Like wax bullets only without primer fumes and with the ability to feed from a magazine. Not good for semi-autos but all the rest of them get some quality practice in your own home. For that, the wasted air doesn't bother me really. For a small game hunting application I'd rather a real airgun or a gallery load. For target practice I think it could fill a nice little niche.

[rsterne]

Agree 100%....

Bob

[Multigunner]

They recently marketed a conversion of the Crosman 397/392 multipump guns that when pumped to maximum only released part of the stored air which allowed one to either fire multiple shots before pumping up again or to top up between shots so each shot used less volume of air but still at the highest pressure improving efficiency.
This is apparently based on what amounted to a unexpectedly useful defect ( too light striker blow, or too stiff valve spring) of some older Crosman rifles.

[rsterne]

Yes, the system is called a "Retained Air Pumper" (RAP) or an "Air Conserving Pumper" (ACP).... and has been used by modders for many years.... I believe the "conversion" is not sold my Crosman, but in the aftermarket.... It works best if the valve volume is increased to hold more air.... I used the same system in my "Millennium Pumper", which was .25 cal, and delivered three shots at 40 FPE without requiring to be pumped again.... However, the large valve took 80 pumps to fill to 1800 psi to do that (or you could do the initial fill from a tank).... After one shot, you could refill with 11-12 pumps....

Bob

[koehlerrk]

rstern, agreed, those or cartridges are a neat way to solve the HPA problem, and having shot one, they are effective. The owner did say that, like a powder burner, you had to tune the air charge to the load. He said he got the best accuracy with a 3800 psi fill. I'm betting the cause is the surplus air you mentioned, rather like a regular firearm shooting best a below max loads.

Interesting, never ran across that multi shot mod... learn something new every day!

[35 shooter]

All of it is interesting to me. I'm amazed at all the different systems to propel a bullet, pellet, or roundball out of the bore with only air.

[melloairman]

rstern, agreed, those or cartridges are a neat way to solve the HPA problem, and having shot one, they are effective. The owner did say that, like a powder burner, you had to tune the air charge to the load. He said he got the best accuracy with a 3800 psi fill. I'm betting the cause is the surplus air you mentioned, rather like a regular firearm shooting best a below max loads.

Interesting, never ran across that multi shot mod... learn something new every day!

Steve from NC on the yellow form and Crosman form makes a kit for the 397 and 392 . He has had that kit out for many years . Marvin

[Multigunner]

I've always wanted to convert a traditional styled muzzle loading rifle to PCP, similar to the actual early air rifles. Addition of a fast thread screw breech or even a simple falling block connected to the trigger guard would make it even better.
I've seen photos of original 17-18th century air rifles of this sort in 7mm on up to .75 caliber.

[Multigunner]

Just remembered a member of a UK forum long ago posted of his CO2 BB conversion of an SMLE rifle. IIRC he used the innards of an American manufacture BB pistol. Don't remember which model. Everything except the barrel liner fit inside the LE detachable box magazine and a modified bolt body. I don't think his invention could be easily restored to firing live .303 rounds, it may have been a demilled DP rifle anyway, but from the sound of it a bit more design work could solve the problems.
A similar conversion has been used to Convert Mosin nagant rifles into air soft guns. There is a somewhat expensive but very finely made steel BB firing Mosin Nagant replica gun , possibly a limited run.

On the TV series "Voyage to the Bottom of the Sea" they often used a prop tranquilizer gun made from No. Jungle carbines.
Not sure if these even fired but the action looked realistic enough to suggest that such a conversion can be done.
I've checked with motion picture prop auctions many times but never found one of these prop trank guns for sale nor any information about them at all other than a few screen caps.

[mac1911]

one thingto keep in mind is these adapters and mods do not make a firearm no longer a firearm.
my neighbor bought the AR15 air rifle upper that attaches onto a Standard AR lower. When his neighbor called to complain the Police charged him with discharging a firearm with in X feet of a dwelling. They did not care about the upper only the serialized lower and its stated cal of .223 rem.