Air Arms Owners Club

Just recently fitted a short stroke piston head and guides etc from Nick Stanning.

Very happy with the initial results.Very straight forward to fit and shoots wonderfully.
It did require a 1/8'' trimming off the spring guide and took the 4 power shims supplied to get it shooting 7.9 aaf express at around 775-780 ish.Roughly 10.5 ftlb ish.

I'm pondering now, instead of using the power washers, might I be better using a slightly longer spring , maybe a spring off the older shorter stroke version-any thoughts or suggestions spring to mind, all comments gladly received.

ps I received the kit with in 2 working days of ordering it, and I let him know I received it and that it was working fine and dandy, I was surprised that he mailed me back showing an interest-I've only good things to say about him and his products, absolutely top man .

Yep top fella

BBF

Nick is one of the finest people i have ever had the pleasure to do business with, first class service.
Spring, Mk 2 spring is the same length, but if you chose to use it rather than mk3 spring, you will require new guides as the mk 2 is constructed of heavier gauge wire.

Thanks for that info Gary.
For the time being I'm going to enjoy it just as it is,it shoots wonderfully.

Maybe somewhere down the line I might ask Nick if he can supply me a mk2 spring with fitted guides.Or alternatively search out a titan spring of similar internal dimensions. It's more of a thought than a plan.

Titan will probabally needed to be reduced in length. i use a mk2 spring which i purchased from julian. i sent the spring to Nick who made me some custom guides. i dont use a piston nose extension though. you have already placed an extra 14mm of preload on the spring, something to note. the mk2 does have three closed coils, if it was over power, you could collapse another coil. to be honest, using the nose extension i think the mk2 would be too much spring. adding that much preload only makes it harder to cock. you will have noticed how much harder your rifle is to cock with the Mk3. that spring is much weaker than the mk2. if your aim is to up the power a little, you could try adding some weight to the piston, by using the original piston weight

Hi,
As the mk2 spring is made for a shorter stroke would that not be shorter.
I could not make power with the original spring and I had a 10mm nose.

Mk2 spring is 20.7mm od wire is 3.35 inner dimeter is 14mm 27 coils with 3 dead coils

OD ID Wire Coils Length COMPRESSED LENGTH LENGTH PER COIL

TX200 MK3 STANDARD 20.9 15.1 2.9 25 222 72.50 8.88

Gaz

The MarkII springs I've had were close, in performance, to the FAC MarkIII spring. They are very much stiffer and thicker in cross section than a standard MarkIII spring.

gaz wrote:Hi,
As the mk2 spring is made for a shorter stroke would that not be shorter.
I could not make power with the original spring and I had a 10mm nose.

Mk2 spring is 20.7mm od wire is 3.35 inner dimeter is 14mm 27 coils with 3 dead coils

OD ID Wire Coils Length COMPRESSED LENGTH LENGTH PER COIL

TX200 MK3 STANDARD 20.9 15.1 2.9 25 222 72.50 8.88

Gaz

the mk2 spring i have is same length as mk 3 spring.in response to your question would that not be shorter, no. it doesn't need to be shorter as the piston receeds less in the comp tube. it requires a stiffer rate as it has to move a smaller volume of air faster to produce the required output. hope this is of some help.
Gary.

Reading last night a lot of the posts in this section was quite a revelation to me, all the subtle nuances of swept volumes,transfer port sizes , piston mass etc etc , mind boggling and some of it to my mind somewhat counter intuitive until you start to think of it as an engine ,to be honest abit above my level of proper understanding.

Yesterday testing purposes only, I swapped out the delrin top hat and replaced it with original steel item.Yes,it actually does increase fps, with aaf express 7.9 it gained approximately 13 fps. I did that just to satisfy curiosity. I then re assembled with delrin top hat as curiousity was sated.I''m impressed with the clingy quality of tinbums assembley paste for piston seal, there were non migrated to where it's not welcome.
Last night before I packed up I put a few shots through the chroney, nothing to read too much in to as the rifles only shot maybe 350+ish pellets from rebuild but just as an initialindicator,all jsb pellets 7.4grn around 800fps-10.5ftlb,7.9grn 780 -10.7ftlb and venerable aa fields at 750 ish fps,10.5ftlb. All very consistent with 7.9 being the best by a long chalk. It feels at the shoulder to best with falcons 7.4.
I'm quite happy with the power of it,when I first got the gun around 7-8years ago it was around 10.9 with aaf 8.4, and since then its had 3 standard service kits in and shot with equal accuracy and predictability more or less either at 10. 5 ish up to 11.7, though admitedly the feel at the shoulder and crosshairs do jump around a little more.

Swapped out the spring for an titan no10, slightly lighter gauge wire ,1 extra coil,10mm longer, smaller inside diameter which is too tight for the tinbum delrin or last aa steel spring guide but fits perfectly snug on a much used aa spring guide out of the spares box.Also removed 2 power washers, gained a little velocity ,15fps on both aaf express and aaf, the falcons have gained 7 ish fps.

Will be shooting it later on this evening.