airsporter s mark one rebuild advice please

[T 20]

Hi Mick
I will have a look through my old mags of AGW that date back to 1977 (I think) to see if I can find out more about JB's mods.
He really knew how to get the best out of an air rifle.

With regard to the leaking taps, my early (Airsporter Mk1's and 2's) with tapered taps seem pretty air tight, but later Airsporters certainly lose power due to air leaks at the parallel tap

I do have a .177 Airsporter S that is the exception and the tap on that gun holds presure very well. It is also nearly 1 ft lb more powerful than my .22 S, that does leak at the tap, so although everything happens very quickly during the firing cycle, leaky taps do mean less power

If you find a solution please let me know
ATB
John

Hi John


You have Email.

I have sent you a copy of the Bowkett file by PDF this gives a good idea of what design the Bowkett head was.

As for the loading tap?

I'm looking at opening out the hole in the tap to 7mm and counterboring the front at 10mm then fitting a top hat made of brass with a 5.5mm bore and using a 10mm OD X 1.5mm cross section O ring in the 10mm counterbore to keep the top hat bush tight when installed.
Any air leaking down the 7mm section of top hat on firing would reach the O ring and expand it slightly so tightening the tap even more.

Apart from that I haven't given it much thought.



All the best Mick

[Phil Russell]

Regarding buying 'standard' BSA springs at auction ... I did so and the springs were somewhat variable. They had a 'cut' end that was not finished properly and did vary in length by up to 2 coils. Now I am not saying that they were not as advertised as genuine BSA made Airsporter springs but be aware that they may need finishing.
Cheers, Phil

[edbear2]

Hi all, as a postscript, have just received a spring from the seller on flea bay......mine is top quality, wrapped in inhibitor paper......35 coils including (very well and flat ground) end coils......length 10 inches dead. If all are like the one I received, then are 100% a genuine item...looks every bit as well made/finished as a titan one

[greasemonkey]

me too,edbear,looks good to me,came next day too.just waiting for the rest of the parts from chambers now..cheers..greasemonkey

[greasemonkey]

hi lads,got my parts from chambers today,looks like i am going to have to modify my piston to get the piston head to fit properly.can any kind soul out there take pity on me and tell me what the overall lenght of my piston should be with the piston head fitted...many thanks greasemonkey

[greasemonkey]

anybody able to help?...greasemonkey

[pennineway.fswo]

Hi Greasemonkey

If you can wait until Tuesday I will strip my Airsporter S and check that dimension for you. I was going to strip and service it next week anyway

I will keep an eye on the thread and if no-one comes up with the size I will post it Tuesday.

Unfortunately I wont have a chance to do this until until then

Regards
John

[greasemonkey]

thanks john, that would be much appreciated..cheers..greasemonkey

[T 20]

hi lads,got my parts from chambers today,looks like i am going to have to modify my piston to get the piston head to fit properly.can any kind soul out there take pity on me and tell me what the overall lenght of my piston should be with the piston head fitted...many thanks greasemonkey

Hi greasemonkey

From the nylon Mercury (same dimensions as an Airsporter) piston head in my hand.

Overall length = 0.6125" (15.57mm)

Front face to pin centre = 0.421" (10.71mm)

I hope this helps a bit

I'll go and give Fred the Ferret his piston head back now ---- he likes to roll it around his pen.


All the best Mick

[greasemonkey]

hi mick,thanks for your info but the measurment i really need is the overall lenght of piston head and piston combined please..thanks greasemonkey

[T 20]

hi mick,thanks for your info but the measurment i really need is the overall lenght of piston head and piston combined please..thanks greasemonkey

If you measure from the tail of the piston to the centre of the piston head retaining pin hole and then add 0.421" (10.71mm), that would give you the overall length of the piston and head combined.


All the best Mick

[greasemonkey]

hi,the problem is i am not sure whether my piston has been modified or my chambers supplied piston head is wrong for my gun hence if i add the two measurments together i wiil not know if i have the correct lenght,however i have measured the new piston head against your measurements mick and it appears i have the wrong piston head,cheers for your help..greasemonkey

[T 20]

hi mick,thanks for your info but the measurment i really need is the overall lenght of piston head and piston combined please..thanks greasemonkey

Ok greasemonkey

After extensive research (I read December 1985 edition of SAR)

Piston body length (tail to flat face) = 4.9" (124.46mm)

Buffer washer = 0.2" (5.08mm)

piston head = 0.6125" (15.57mm)

Overall length from tail of piston to front of piston head = 5.7125" (145.0975mm)


All the best Mick

[greasemonkey]

hi mick ,a big thank you for that,you are a scholar and a gentleman.the chambers piston head is indeed wrong as my piston is of standard dimensions,if i shorten the spigot on the piston,the new piston head will fit but the overall lenght will be "5.475overall, approx ".225 short of standard.if i did this what affect would it have on the gun.this piston head is the only one chambers do.i could try mr knibbs or now i have the correct dimensions i could knock one up on the lathe...cheers..greasemonkey

[T 20]

hi mick ,a big thank you for that,you are a scholar and a gentleman.the chambers piston head is indeed wrong as my piston is of standard dimensions,if i shorten the spigot on the piston,the new piston head will fit but the overall lenght will be "5.475overall, approx ".225 short of standard.if i did this what affect would it have on the gun.this piston head is the only one chambers do.i could try mr knibbs or now i have the correct dimensions i could knock one up on the lathe...cheers..greasemonkey

Hi greasemonkey

You seem to be missing the nylon buffer washer that fits inbetween the piston and piston head.

I have sent you a diagram Via Email that should help you.

I often leave the buffer washer out as a way of increasing the stroke a little.
On most guns it works well but on some the cocking lever fouls on the piston when fired or the gun just feels really nasty when you fire it --- not realy a big problem as you can always revert to the standard setup.


All the best Mick