Spring Gun tuning - Top Hat advice

[Mr.Fixit-Norm]

You really need a longer rear guide! Short guides are one of the main reasons springs get kinked and worn.

Yes, especially on such a long thin spring! I’ve got two different diameters of delrin rod on they’re way from the bay which should arrive next week

If it works out right the one I make will be just over twice the length of the existing one.

Norm

[TonyL]

If you whip the piston out, Norm, and just make that rear guide to a length so that the guide and top hat don't clash once any spacers / washers etc fitted. Re top hat bearing, maybe a nice, polished steel one that's not a tight fit in the piston, allowing easy removal if required.

[TonyL]

P.S. Norm, most people would go for a guide that is a nice, firmish, sliding fit to reduce twang. Not so tight that you have to hammer it in, though. The diameter you mention may be a little loose? But, if you don't mind going "old school", moly grease will help dampen the twang. Plus that extra length will help.

I'm guessing you may have to go for the original type of guide fitting, ie into the end block, as a guide with a flange at the rear may not allow the piston to come backwards by the required mount to allow cocking? You'll need to have a little play to see if this may be the case. If a design with a flange would work, you'd need a wider diameter delrin bar to start with, larger diameter to suit the cylinder ID and the smaller diameter to suit the spring ID. Does the piston have a latch rod or does the trigger sear engage with a cut-out in the piston body?

[Mr.Fixit-Norm]

P.S. Norm, most people would go for a guide that is a nice, firmish, sliding fit to reduce twang. Not so tight that you have to hammer it in, though. The diameter you mention may be a little loose? But, if you don't mind going "old school", moly grease will help dampen the twang. Plus that extra length will help.

I'm guessing you may have to go for the original type of guide fitting, ie into the end block, as a guide with a flange at the rear may not allow the piston to come backwards by the required mount to allow cocking? You'll need to have a little play to see if this may be the case. If a design with a flange would work, you'd need a wider diameter delrin bar to start with, larger diameter to suit the cylinder ID and the smaller diameter to suit the spring ID. Does the piston have a latch rod or does the trigger sear engage with a cut-out in the piston body?

Hi Tony,
Yes I was going to try both sizes I’ve ordered ( 10mm & 12mm ) and see which works best in terms of slideability

When I said a flange, I got that slightly wrong, I meant I was going to cut the old guide off flush with the end of the plug then if say the 12mm rod is suitable I’ll drill an 10mm hole in the plug and machine the end of the rod to slightly bigger than that so it’s a tight push fit in the plug

I’m assuming it’s best to still use moly grease on the spring to make it slide over the guide even easier.

The trigger sear engages with the piston body directly.

Just got to wait for the rod to arrive, should be here anytime after Friday this week.

Norm

[TonyL]

With the spring ID being 12.1mm, Norm, use the 12mm rod; the 10mm one will give too much clearance.

And, yes, use the moly grease. A little on the guide and a little smeared over all surfaces of the spring - ends, ID nod OD.

[evert]

You want the guide to be able to rotate.
Machine the end plug to look something like this:
http://www.airgunspares.com/store/pr...-Part-No.-V15/

Then you can make a rear guide with an end flange, and a hole that fits over the stub you left on the end plug.
Add a thin steel washer between the delring guide and the end plug to facilitate rotation.
Make the guide about 0.05mm larger than the spring ID for a really tight push fit. This may reduce power a bit, but will kill most vibration without adding lagre amounts of grease.

[evert]

This is a good example of how a guide will look if you leave a rear centering stub:
http://www.airgunspares.com/store/pr...er-%26-Osprey/

[evert]

Sound like success!
I dont think you want to push those guns very much faster, but as Tony says, lighter pellets will probably give you a bit more energy and velocity.

[Mr.Fixit-Norm]

Sounding good and suitably de-twanged, Norm.

If you can, get hold of some RWS Hobby and JSB RS. These tend to give higher outputs in lower tuned springers. If the power isn't uncomfortably close to the limit (doubting it will be), it sounds like you'll have plenty of scope to raise power by increasing the preload, if required. Maybe a 5mm increase to start with and then going in 2mm increments?

Sound like success!
I dont think you want to push those guns very much faster, but as Tony says, lighter pellets will probably give you a bit more energy and velocity.

Cheers Guys,

I think given that this gun is just a bit of fun ( remember that stock ), I’ll keep the power where it is, my main aim now is to find the best pellet for accuracy. Despite the heavy trigger it feels quite nice to shoot

I’ll see if I can try and get some of the pellets you recommend Tony. I’ve had a look on the Intershoot site and they don’t quote a size for the JSB RS which is a shame. I wonder if there’s any way to find out ?

Norm