Airsporter Piston Mod? Options

[Ninja Handyman]

I've just stripped my brothers airsporter as he'd put a new spring in it and its firing cycle became really harsh. Chrono'd it and it is only doing 725fps in .177 (9.8ft lbs) not too drastic for an airsporter but not great. The spring is not standard and seems a tight fit in the piston so I'm going to junk it and get a standard one. I've never really been a fan of the O'ring set up on bsa's it seems a little tight and the piston head is slopping around. Does anyone know whether there is a mod that can be done to convert it to something like the weirauch piston seal set up?? I thought this might also increase the volume of the compression chamber and help to get it up to 11+ ft lbs, but could also be properly sized for fit to help the firing cycle. Any help or tips would be great. Cheers

[bruno527]

Its a while since i messed with an airsporter, if i rmember the seal plate detaches & the seal is attached with a rivet ?? or is that the relum !

we used to get a piece of old leather, simmer it in graphite greese, then using dads socket on a piece of wood to punch a seal out & drill & tapp the seal block & attach it with a countersunk 6mm & washer, then use a tapered reamer to open the port up a mm or so, leaving it tapered for flow, from the inside, use lapping paste to polish the barrel inside,with a rag on a steel rod in a drill , ox spring & assemble with graphite greese & boy oh boy..did the pellets fly out. (IMG:style_emoticons/default/biggrin.gif)

try Chambers or TR Rob

http://www.gunspares.co.uk/shopdisplayprod...SA+Airsporter+S

http://www.trobb.f9.co.uk/Specialist%20Parts%20Page.html

[Ninja Handyman]

Thanks for the reply bruno, I was thinking on the lines of getting rid of the head assembly completely if pos and maybe replacing it with a cup type washer but wondered if anyone else had already had a go at that type of mod on an Airsporter piston and how it went. Thanks again. Martin

[jamie]

I would not think it to difficult if you have a lathe to make the mod's but it might take a lot of messing around to get the power set right ,i doubt if this thread will survive long enough to get any answers from many people.
Good luck in your goals i would be interested in the results as i have an old one in the back of the cabinet.
Jamie.

[tigger]

I would not think it to difficult if you have a lathe to make the mod's but it might take a lot of messing around to get the power set right ,i doubt if this thread will survive long enough to get any answers from many people.
Good luck in your goals i would be interested in the results as i have an old one in the back of the cabinet.
Jamie.

The O ring system on older BSA guns is very efficient, changing it for a leather, PTFE or parachute set up would almost certainly loose you power, is the O ring you have to tight or to slack a fit? With these the piston assembly should require a steady but light pressure when it's put back in the cylinder, light moly grease works well with O rings.

O rings don't work well on out of true bores thats why BSA precision swaged the air cylinder, you won't find wonky or out of round cylinders on these.

[Ninja Handyman]

Thanks guys, I've now got the new spring, O ring and I also got a piston weight too just to have a play with. The first thing I've noticed is the spring I took out is too large in Dia. and quite a bit longer and the O ring also is larger Dia. so not sure where he got the parts from! Once it's back together I'll Chrono it and do a quick post in case anyone is interested. Cheers

[tigger]

Thanks guys, I've now got the new spring, O ring and I also got a piston weight too just to have a play with. The first thing I've noticed is the spring I took out is too large in Dia. and quite a bit longer and the O ring also is larger Dia. so not sure where he got the parts from! Once it's back together I'll Chrono it and do a quick post in case anyone is interested. Cheers

I can't remember any of the old Airsporters I had being tack drivers, but they do handle nicely and are very pleasant to shoot, if it's a .22 try 5.6mm graded pellets or if you can find any H&N FTT in 5.54mm flavour, power up to the limit as well once fully sorted, let us know what your one does!

Ignore the last bit I see you've got a .177! It's late and all that.

This post has been edited by tigger: Tue Feb 9 2010, 23:50

[Ninja Handyman]

Feels sweet when fired now but ran out of daylight so haven't power tested yet, hopefully tomorrow...

[Ninja Handyman]

Chrono'd it today and it's still producing 9.8 ft lbs albeit with a much shorter standard spring in it and it is nice to shoot again. Tried the piston weight and it made no real difference apart from slightly increasing felt recoil so took it out again. I have a feeling the Airsporter's air cyl. is on the small side which limits its power so think I'll pass it back to bro in standard form. Atb

[AirArmsDavid]

See also:

http://bsaog.co.uk/forum/index.php?topic=13051.0

and

http://www.gunspares.co.uk/shopdisplaycate...&cat=Tuning

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[Ninja Handyman]

Thanks for the links. Atb

[kitkat1963]

I have to say, my Airsporter Mk4 has never been apart, and using Eley Wasps in 5.56, I get 8.49ft/lb, and I don't think they ever got anywhere near the legal limit anyway, I reckon 10ft/lb is about as good as you could wish for, but I could stand corrected on that one.

[Ninja Handyman]

Yes I think you're right, it's .177 too so 9.8ft lbs is pretty respectable for this gun I would think. Going to do some pellets tests next.........

[AirArmsDavid]

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Both my V-Mach HW80 .22 and V-Mach .22 Pro Sport run at 10.5 ft lbs and are more accurate and nicer to shoot as a result of not aiming for 11.99 ft lbs!

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My 1974 Original 50 .177 does 7.5 ft lbs yet this makes hardly any difference to trajectory and it's superbly accurate out to 50yds with sufficient power to knock down an HFT target at that range.
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[baron]

Hi David

I do like that model 50

It looks very familiar to me

Chris has passed on your number to me so that I could stay in touch.
SPL have just re-blued/blacked a nice Mk2 Airsporter (.177) for me. Price is now really expensive at £15/gun (IMG:style_emoticons/default/smile.gif) but the finish is brilliant

I reblued the tap myself with a soft flame and engine oil which went well. Black hammerite brought the trigger block back to form but it will need t-cutting when fully hardened (in a month or two)

I will give you a call re bluing and etching
ATB
John

[Alpha]

A mod I used to do on BSA Mercury's and Airsporters was to remove the rubber washer under the alloy piston head, This gave a little extre cylinder capacity and on both models used to run 11 FPounds, you have to turn the piston head around and redrill for the roll pin to retain the piston head. (IMG:style_emoticons/default/smile.gif)