Sunday Project; HW99S Shortie

[deejayuu]

I think the big question with that rifle is

Do I built it up and cross fingers & hope that it does not have the porous breech problem...

For what it's worth we check for void issue with TP plugged and cylinder vertical. A pool of water around joint area then warm jaws and watch for bubbles on water surface.
If it's faulty we repeat the process with adhesive which gets drawn into the void on cooling.

[Hsing-ee]

For what it's worth we check for void issue with TP plugged and cylinder vertical. A pool of water around joint area then warm jaws and watch for bubbles on water surface.
If it's faulty we repeat the process with adhesive which gets drawn into the void on cooling.

That’s a great idea! but maybe there’s some kind of oil or something to use instead of water not keen on getting it in my voids …

[TonyL]

Re-barrelled in .177 and fitted with the new glided piston & lube job. Three and a half hours including looking for the bits.

Main delay was the cocking lever pivot which simply would not punch out, and my attempts to make a press from a G clamp failed miserably. Ended up drilling it out with a Proxxon in its tiny drill-press, kind of a European Dremel.

Other delay was putting the cocking lever shoe on backwards.

Pluses are found a nice stainless steel QD cocking lever pin in the parts box, and an appreciation of the 'tile and lug' system of keeping the back block on. While the screw-on type is aesthetically better engineering, the 'tile and lug' system is just easier to deal with.

12" barrel seems VERY short and will be interesting to see how it gets on in terms of accuracy, the brass muzzle weight will have to be done another day as I need some PTFE sheet to protect the barrel before fitting it.

Just need to scope it and it will be ready for testing.

Nice one, Al.

Nice find re the QD cocking lever pin.

Putting the cocking lever shoe on backwards? On a 99? What's that all about, then?

Hope testing goes well and results please.

[TonyL]

I think the big question with that rifle is

Do I built it up and cross fingers & hope that it does not have the porous breech problem...

OR

Spend an extra day doing the porous breech fix?

The cylinder has nice blueing and seems good but thats all I know about it.

I used the JB Weld thread lock on mine (Perma Lock or similarly named?). Nice and easy and did the job. Maybe better to do it anyway whilst the gun's in bits for extra reassurance?

[Hsing-ee]

Putting the cocking lever shoe on backwards? On a 99? What's that all about, then?

Hope testing goes well and results please.

I don't know what it is called, you're right the 99 doesn't have a cocking shoe, it is the flat spring that bears on the cocking lever in the manner of a cam-chain adjuster shoe.

Got it scoped with a vintage Tasco 3-7x32, just sorting out a pellet selection for testing. Taking the Mercury as well, cleaned the barrel and fitted with a similar scope of known performance. Can imagine which one is going to do better ... even taking some original vintage Eley Wasp .177s to see how the BSA does with its intended diet ...

[Hsing-ee]

I used the JB Weld thread lock on mine (Perma Lock or similarly named?). Nice and easy and did the job. Maybe better to do it anyway whilst the gun's in bits for extra reassurance?

Probably right .. Did you just drizzle it in under gravity then sand it off or did you do all that arsing around with blocking the TP and generating a vacuum for 24 hours etc?

[Born Again]

I've never fixed a porous part, but when I was casting detailed urethane parts in silicone moulds I learned something that might help someone. I have both a vacuum chamber and a pressure pot, the vacuum is used for degassing resins as well as creating a vacuum to draw resin in, it's a good solution but not everyone has access to a high vacuum pump or suitable container. A pressure pot is much easier to find and compressors are common. You'd think that the pressure pot would be inferior because there will always be a bubble of air trapped in the part. Not always so, when you get to 50 or so PSI the bubble of air will actually dissolve into some resins, leaving no bubble behind. It definitely works with urethane resins that I use, producing flawless castings.

So, it's possible you can completely seal a porous part without a vacuum system.

[TonyL]

I've never fixed a porous part, but when I was casting detailed urethane parts in silicone moulds I learned something that might help someone. I have both a vacuum chamber and a pressure pot, the vacuum is used for degassing resins as well as creating a vacuum to draw resin in, it's a good solution but not everyone has access to a high vacuum pump or suitable container. A pressure pot is much easier to find and compressors are common. You'd think that the pressure pot would be inferior because there will always be a bubble of air trapped in the part. Not always so, when you get to 50 or so PSI the bubble of air will actually dissolve into some resins, leaving no bubble behind. It definitely works with urethane resins that I use, producing flawless castings.

So, it's possible you can completely seal a porous part without a vacuum system.

Interesting; thank you. Tie-ing in with:-

[TonyL]

Probably right .. Did you just drizzle it in under gravity then sand it off or did you do all that arsing around with blocking the TP and generating a vacuum for 24 hours etc?

Hi Al. A bit of both.......I blocked the TP. Ran some thread lock in. Then squeezed it in, using the piston with its old seal. I then found a suitable small piece of wood which, when fitted behind the piston, was long enough to sustain some pressure with the end block screwed in. Left for a few hours. Removed piston. Left the cylinder for a day then cleaned the end with wide dowel with some wet and dry on the end.

[TonyL]

I don't know what it is called, you're right the 99 doesn't have a cocking shoe, it is the flat spring that bears on the cocking lever in the manner of a cam-chain adjuster shoe.

Got it scoped with a vintage Tasco 3-7x32, just sorting out a pellet selection for testing. Taking the Mercury as well, cleaned the barrel and fitted with a similar scope of known performance. Can imagine which one is going to do better ... even taking some original vintage Eley Wasp .177s to see how the BSA does with its intended diet ...

Gotcha. Maybe a cocking link tensioning spring, then?

I'd guess the 99 will also like those old Wasps. But I bet it'll love the Hobby and FTT.

[Hsing-ee]

Gotcha. Maybe a cocking link tensioning spring, then?

I'd guess the 99 will also like those old Wasps. But I bet it'll love the Hobby and FTT.

Ah yes cocking link tensioner. Like a cam-chain tensioner but smaller than the one on a 400/4. The Mercury did actually like the Wasps.

After the somewhat frustrating session with the Mercury I returned from the dentists to try the 99K.

Oh dear, not good even at 10 yards. So I thought, maybe it is the scope? Swapped it with the one on the Mercury. Same deal. Tried it at greater range in case I was just not making an effort.

At 30 yards the groups were 3" even though I could see the crosshairs were not moving perceptibly. Is it this short barrel, not having a choke might do that? But Paul would have said if it was super fussy about pellets when he sold it to me, he's a true BBS gentleman.

I noticed the gap between the thud of the rifle and the 'snaK!' of the impact had a pistol-like length to it. Looking at the target the pellets were only slightly squished.

Hm. Power issue. Spring is nice and strong, cocking with the short barrel emphasised that.

I performed the 'digital compression test'. Absolutely no vacuum and no pressure build through that TP. Gun must have been making 4 fpe with whatever air couldn't escape fast enough past the piston washer.

At the rebuild yesterday when I swapped the pistons I did notice there was a nick in the old piston washer, but I couldn't find any sharp edges. Maybe I missed one. It was quite a small nick so I am not sure whether that would cause the catestrophic loss of compression. I also used very dry molygrease, like I blended some moly powder with some grease to make a paste, could this have resulted in a lack of sealing? Not sure.

What I suspect is that the supplier of the glided piston has put a 25mm piston head on the piston instead of the 26mm, but I did not notice because the Air Arms style bearings give a bit of cushioning when sliding the piston in.

It's too late to strip it down tonight but I think that is the problem. I've got a 26 mm seal somewhere from an HW85 so hopefully that will solve this mystery.

Springers eh? Nuffink is simple ....

[Hsing-ee]

Hi Al. A bit of both.......I blocked the TP. Ran some thread lock in. Then squeezed it in, using the piston with its old seal. I then found a suitable small piece of wood which, when fitted behind the piston, was long enough to sustain some pressure with the end block screwed in. Left for a few hours. Removed piston. Left the cylinder for a day then cleaned the end with wide dowel with some wet and dry on the end.

That would be the pressure system rather than the vacuum system right? Anyway the way you describe it doesn't sound too tricky. I ought to do it just to rule the problem out. Thanks.

[deejayuu]

That’s a great idea! but maybe there’s some kind of oil or something to use instead of water not keen on getting it in my voids …

Used turps too. Handy 'cos it leans and evaporates.

[TonyL]

Ah yes cocking link tensioner. Like a cam-chain tensioner but smaller than the one on a 400/4. The Mercury did actually like the Wasps.

After the somewhat frustrating session with the Mercury I returned from the dentists to try the 99K.

Oh dear, not good even at 10 yards. So I thought, maybe it is the scope? Swapped it with the one on the Mercury. Same deal. Tried it at greater range in case I was just not making an effort.

At 30 yards the groups were 3" even though I could see the crosshairs were not moving perceptibly. Is it this short barrel, not having a choke might do that? But Paul would have said if it was super fussy about pellets when he sold it to me, he's a true BBS gentleman.

I noticed the gap between the thud of the rifle and the 'snaK!' of the impact had a pistol-like length to it. Looking at the target the pellets were only slightly squished.

Hm. Power issue. Spring is nice and strong, cocking with the short barrel emphasised that.

I performed the 'digital compression test'. Absolutely no vacuum and no pressure build through that TP. Gun must have been making 4 fpe with whatever air couldn't escape fast enough past the piston washer.

At the rebuild yesterday when I swapped the pistons I did notice there was a nick in the old piston washer, but I couldn't find any sharp edges. Maybe I missed one. It was quite a small nick so I am not sure whether that would cause the catestrophic loss of compression. I also used very dry molygrease, like I blended some moly powder with some grease to make a paste, could this have resulted in a lack of sealing? Not sure.

What I suspect is that the supplier of the glided piston has put a 25mm piston head on the piston instead of the 26mm, but I did not notice because the Air Arms style bearings give a bit of cushioning when sliding the piston in.

It's too late to strip it down tonight but I think that is the problem. I've got a 26 mm seal somewhere from an HW85 so hopefully that will solve this mystery.

Springers eh? Nuffink is simple ....

Hopefully fitting a new / known to be good 26mm seal will sort it. If not, re-fit the old piston with the new / known to be good seal.

And don't forget the breech seal.

[maximus]

The 25mm seals are a different design to the 26's so should be able to tell by looking at them. Regards Max