HW99S woes!

[BTDT]

Sorry Jim.

When I fitted the Wonky Donky spring and guides to my 99, I didn't take any measurements.

I'm sure Bigtoe or Wonky may be able to help out, though.

Hope you're okay and still loving the Technical Airgun articles. Keep them coming!

Unfortunately, I haven't managed to put many shots through my recently acquired .177. Just a few last week to establish an approximate zero. It's doing 10.5 with 'Domes and is so very sweet straight out of the box that, unless anything were to start feeling untoward, will be left untouched, certainly in the short term. Very mild mannered, with minimal sight picture disturbance and no twang at all. Was thinking of dropping some moly paste in on the cocking link, but all seems fine.

Rule 1 of productive springer tinkering is measure everything, Tony.

I think BT is very possibly right about the piston seal (it's easy to shave a lump off if the cylinder cut-outs are not deburred), but the OP's rifle is currently oversprung: I'm trying to calculate by how much, and by how much were coils flattened.

The September edition (mine arrived yesterday) just happens to have a three page article about selecting the best aftermarket spring.

[TonyL]

Rule 1 of productive springer tinkering is measure everything, Tony.

I think BT is very possibly right about the piston seal (it's easy to shave a lump off if the cylinder cut-outs are not deburred), but the OP's rifle is currently oversprung: I'm trying to calculate by how much, and by how much were coils flattened.

The September edition (mine arrived yesterday) just happens to have a three page article about selecting the best aftermarket spring.

Sorry JT, I'm a numpty!
As any spare time is such a valuable and rare commodity for me, I just cleaned, de-burred and fitted the new spring, guide and top hat. Other than the replacement spring being a little shorter, that was it. So not sure on length, number of coils, wire diameter etc.

As you and Tone say, most likely the piston seal. And oversprung.

Can't wait to see mainspring article. As per some of my previous ramblings, this component is obviously at the heart and so very crucial to how a springer operates (surprise, surprise! ), yet so few understand about the workings and relevance some of the key items making up the spring's specification.
Will the article include anything like how to select a spring based on certain parameters, like stored energy, preload etc?

[Eligus]

Which airgun magazine has the article?

Zebedee - I have the original spring and have tried it with an assortment of pre load washers, at one point it managed 10.2 ftlbs.

I was planning on reducing the pre-load/initial compression somewhat as it appears the springs potential energy is compromised by not utilising the expansion available - deciding on the optimum amount I have to compress it when fitting the rear block is a bit of guesswork for me.

The compression tube has been polished and de-burred and the piston seal appears to be in good order though I will order a new one and see if it makes any difference.

[TonyL]

Airgun World is the magazine you want.

Jim Tyler's Technical Airgun articles are excellent. Full of relevant, useful information and make for addictive reading!

[Snooper601]

Airgun World is the magazine you want.

Jim Tyler's Technical Airgun articles are excellent. Full of relevant, useful information and make for addictive reading!

And for those new to the bbs and spring gun tuning Jim Tyler is BTDT

Cheers

John

[brian747]

And for those new to the bbs and spring gun tuning Jim Tyler is BTDT

Cheers

John

And only God knows more about springers Than Jim!!!!!
atb brian

[Patrick 2]

If the piston seal is not damaged what sought of fit is it in the bore if it's too tight a fit that will cause loss of power.I believe the piston with seal should just about slide down the cylinder under its own weight when the cylinder is held vertically.

[TonyL]

If the piston seal is not damaged what sought of fit is it in the bore if it's too tight a fit that will cause loss of power.I believe the piston with seal should just about slide down the cylinder under its own weight when the cylinder is held vertically.

.....And stop its descent once the transfer port is blocked.

Some have refined the thinking to this method by also incorporating the weight of the mainspring, and not just the piston.

Must admit, unless they're excessively tight, and after reading some of Jim's recent works, I prefer to let them run themselves in. So, slightly lower power to begin with, but with prolonged seal life.

[Hsing-ee]

its near identical make up to ultimox, does not burn, can also be used on O rings...and is cheaper...plus i use it on the bikes

done 2 springers with it now...ones my lgu...working great,

Hand up at back of class... but but but... SIR! look in the product spec... its made of hippy butter!

'Finish Line’s Teflon Grease features an Inherently Biodegradable formulation which means that between 20% and 60% of the product’s base oils will degrade within 28 days of being exposed to the outside environment.'

That seems a bit rubbish. My ye olde molygrease seems to last for decades. Maybe FL is only suitable for shooters who strip their rifles once a week?

[bigtoe01]

Hand up at back of class... but but but... SIR! look in the product spec... its made of hippy butter!

'Finish Line’s Teflon Grease features an Inherently Biodegradable formulation which means that between 20% and 60% of the product’s base oils will degrade within 28 days of being exposed to the outside environment.'

That seems a bit rubbish. My ye olde molygrease seems to last for decades. Maybe FL is only suitable for shooters who strip their rifles once a week?

ptfe stays...and stays for a long time, the petroleum based carrier degrades in moly and the moly stays...difference is the grease i use (finish line) does not burn...where the carrier in old moly grease does.

Use what you may...modern lubes specifically engineered to work with polyurethane and rubber etc are going to work better than " what we used before because thats all we had"

[bigtoe01]

The OP's gun here is over sprung, i know because its easy to do with the 99s..I did it to mine, plus HW do not deburr the actions correctly and its seriously easy to damage the seal when you pull the piston out and push it back in.

Its really that simple

[TonyL]

The September edition (mine arrived yesterday) just happens to have a three page article about selecting the best aftermarket spring.

......Got mine today, Jim.

Superb, thank you and exactly what is required.

[slinger69]

Numpty here too guys. Stripped my month-old 99 for a polish, lube, and pop bottle piston skirt fitment. (Waiting to source some sheet delrin.) The only measurements I made were for the skirt: 4..5" x 68mm. (It was convenient to use both units). The burring around all the holes in the compression tube end was very noticeable, though luckily no damage done to my seal. They've now been de-burred.

I will start a pocket notebook and measure everything though BTDT when I put the delrin skirt in. I've also taken the 'iron' sights off, which feels a bit like throwing away pen nibs and relying solely on ball point.

As well as the usual seal & metal lubes, I've tried some tungsten disulphide (WS2) spray-on for the delrin cocking insert and trigger. I was dubious, but after applying it to my S200 this action has become noticeably smoother.

[Eligus]

slinger - what sort of power is your 99 putting out?

[slinger69]

Hi eligus,
11.4 ft lbs out of the box, may be slightly higher now, due to washer retaining skirt.