New Pro-Sport .22 seems low-powered

[Blackbaronfish]

Chris knows his onions
Glad it’s all sorted

BBF

[tonyc]

I presume he just put a washer in; it was that quick. Including testing it, he was only gone ten minutes.

So probably at the low end of the normal setting leaving the factory. It's always interesting to know exactly what was done just to pick up on any common or recurring issues... and to hear if/how it changes with further use.
Happy shooting!

[Timmytree]

Try lighter pellets, you may find a rise in power but possibly not a gain in accuracy.
As soon as your warranty runs out get into the guts and learn all about it, change the grease for something black and slippery rather than Air Arms gorilla snot glue. They are the easiest rifles to strip and rebuild, I can replace a spring or seal on mine in less than ten minutes.

[Walnut92]

Revisiting an old thread as as having similar experience:

I bought a s/h but mint Prosport .177 a year ago (with a TbT tuning kit) and it shot (and still does shoot) beautifully. It chrono'd at 10.6 ft.lb, and with the smoothness was ideal for my uses at 25-45 yards.

Having got fully used to it, I can get 1/4" groups at 25 yards and I've only been shooting rifle for a year. Probably 2,000 shots through it.

It is however very hold sensitive. Minor changes in hold result in a similarly tight group (so the 'grip' is right but the hold position affects the gun differently) but a change in POI of say 1/2" max. I'll post separately on this.

Chrono'd it again (not because of above) and noted that it's down at 9.3 ft/lb. This is all with AA Field 8.4gr 4.51 (which measure with Pelletgage to 4.52 at least. Resized to 4.51 to test also - little difference although a tiny bit more consistent.

Stripped it and it is all pretty much spotless, just wiped with grease. Two preload delrin washers on top hat.

So, have ordered new spring. The spring doesn't 'roll' totally concentrically, but it's not what I would call 'bent',

However, seems a bit odd to have lost this much power?

Any other thoughts before it goes back together? thanks

[MartinC]

Watching this with interest as I've just picked up a pre owned pro sport and about to tune it

[Walnut92]

So this is where I ended up.

New spring showed that old one had acquired 10mm of permanent set.

Cleaned, reassembled with original TbT kit and with three delrin preload washers it was bang on 12fpe.

Risk of staying too hot, and that fpe unnecessary for me, so one out and settled at 11.3-ish.

The reason I put three in (2 were there originally) was simply that I had lost so much power and didn't credit that a new spring plus an extra 4mm of preload would be so significant in getting it back up.

May well end up taking one more out if it remains settled. So far it is sticking at around that avge fpe and with fps variation of no more than 10 across 20 shots.

Now, the question is still why so much set on a spring with only 2k pellets through it and immaculate in every way - no excessive lube and so on.

Many may choose to disagree with me, but in my opinion the delrin guide was far too tight on the spring. I appreciate that a spring expands on the guide when compressed in theory, but my own view is that the length of the spring precludes this happening cleanly. I can only surmise that this MAY have resulted in the spring being more stressed towards the 'centre' (i.e. between top hat and guide) where it was freer to be compressed.

Although also it is generally considered that once properly scragged a spring will almost forever take the same compression without length change, it is in fact true that a relatively open coil will NOT do this as the more open coils have more stress. We of course need relatively open coils as we want to apply quite a lot of length compression.

[tonyc]

Unless you know the full previous history it's possible that the old spring wasn't the original. If you checked the number of coils and ends were the same as the new spring it would rule out any chopping of the spring by the owner. If it is a chopped spring the annealing of the end will cause a weakness liable to compression - the amount depending on how the spring was heated and cooled and over what length. The tbt guides (if not with supplied spring) are supplied tight so may not have been resized sufficiently so your suspicions may be right.

It'll be interesting to hear how the new spring settles in.