Pistol Power

[Target Bunny]

Hi Stuart B
tailoriand has said "In my opinion", it's his opinion, he's entitled to it no matter what our opinion is. We have different opinions, so what?
Daystate owners completeley fail to understand anyone saying, "HOW MUCH?" and although I would love to be in a position to hear folk say that to me I can only dream about it.

Mea imperare! Sputum facere tu felix laetitiam? Processus! Sputum fabricati diem.

Jim

[Target Bunny]

Hi Guys
http://i280.photobucket.com/albums/k...-Messenger.jpg

Despite what I said previously I have now sent off for a chrono (don't tell "She Who Must Be Evaded") and I can now do some sensible tests on the Smith & Wesson.

I think that pistol tuning is pretty much frowned on by "authority" since if you get it wrong (right?) you end up with an automatic firearms offence as you have a handgun. So now that I can check out what is happening I can try out a few modifications to up the power. I said I could think of three ways without too much trouble and so I'll try them. There is a fourth simple way but since that involves changing to the 8" barrel I already have I can't count that, mind you if somebody wants to send me the 4 & 6 inch barrels I am willing to check them out.
OK so in the interests of staying legal I will do the work a stage at a time and check after each one to see the results.
First up I will pack the hammer. Have a look at the first picture and the light coloured area shows the rear of the gun and the back of the hammer and front of the striker plate.
http://i280.photobucket.com/albums/k...rade/001-1.jpg

On this gun the hammer does not hit the gas release valve. It hits the striker plate and that in turn hits the gas release valve. This plate is also the safetey since it has to be moved up when the gun is cocked to move it out of the retaining notch and whilst it is in the down position it prevents the hammer from hitting the gas release valve.
I keep saying the gas release valve (GRV) as if it is some kind of mantra. It is! If this bit of kit fails on any co2 gun it becomes a club. What it does is allows a carefully measured dose of co2 to enter the magazine behind the pellet and we are on the way to that perfect score.
The length of time the valve is open dictates the ammount of co2 it releases. More co2 more power, less co2 less power. The length of dwell (time open) is a combined function of three things. The strength of the internal spring in the GRV, the strength of the trigger spring, and the clearance between the hammer and the GRV, or in this case the striker plate. Adjust any of these and you adjust the dwell, adjust the dwell and you adjust the power. So by packing the hammer I can override the GRV internal spring for a fraction longer because the hammer is now contacting the striker plate sooner and so staying in contact longer releasing more gas. The picture below shows the GRV on the left and the striker plate to the right of it in the light coloured square and when I have the chrono I will put a small piece of metal between the hammer and the striker plate then measure the speed.

http://i280.photobucket.com/albums/k...rade/003-1.jpg

Untill I do the check I have no idea how thick the piece will need to be and yes I will use more co2 per shot.

For mods to the valve the picture below may help.
http://i280.photobucket.com/albums/k...gramValve2.jpg

I'll come back when I have results.

Target Bunny


Mea imperare! Sputum facere tu felix laetitiam? Processus! Sputum fabricati diem.

[Snapshot]

> More co2 more power, less co2 less power.

Within limits. If you have too much CO2 released it will not have time to turn from liquid to gas completely and you'll just get a spray out of the barrel. I suspect making more efficient use of the existing amount of CO2 by improving the sealing around the magazine may be more useful but I'll be surprised if this isn't on your 'do' list.

Jonathan

[Target Bunny]

Hi Jonathon
Without knowing the actual pressures involved I can not be certain of the state of the co2 in the capsule and each shot decreases the pressure by a finite ammount and... you get the idea. I also do not know, no one will confirm or deny, whether the GRV is simply a valve or a resevoir. In other words does it charge up from the capsule (in which case my hammer mod will fail) or does it simply release co2? I think it's the latter but I don't KNOW. In either case I believe that I will reach the legal limit before allowing liquid to be released and since there is no syphon tube inside the capsule and co2 has a propensity to resublimate rapidly liquid release will be a low risk.This risk will also be reduced because of the length of the barrel.

Actualy improving the seals was not on the list simply because it will rely on fitting a seal to the barrel on the barrel side of the mag and a non standard thicker seal on the stock side to replace the standard seal and I do not have machining capabilities (no lathe) to do either. Also this would probably mean that the seals would be in constant contact with the mag and subject to wear.
However since sitting down to type this I am now wondering if I can get a couple of teflon washers and pierce them to fit on the magazine. Hmmmmmm.

The other ideas in order of simplicity were to remove the hammer mod & increase the trigger spring tension then to see if I could decrease the valve spring tension. If get as far as the last one I will also polish and relieve the valve piston and internals but stop short of opening the valve delivery nozzle since I have no information on it and could easily destroy it.
The final stage will be to see if I can combine any of the mods to get a bit nearer the limits.
I am not happy about the hammer mod simply because I do not know the internal clearances on the GRV and it could damage the GRV itself. This could be the basis of the comments that tuning these guns destroys them.

Thanks
Jim

Mea imperare! Sputum facere tu felix laetitiam? Processus! Sputum fabricati diem.

[Target Bunny]

Chrono has arrived
Test firing at weekend for datum readings.
Procedure will be: Gun out of case and capsule loaded. Leave for half hour. Ten shots at target. (Cry at crap shooting). Ten spaced shots single action. Ten shots double action.
Can't do ten rapid since chrono resets every shot (couldnt afford recording version).
Will repeat proceedure on all tests.

Target Bunny