Nemesis Power Uplift?

[Target Bunny]

This is probably one ofthe most underated pistols of all time and I am chuffed to bits with mine. BUT, does anyone know of a tune up that will give just a bit more power?
I want to do some work on the trigger of my .177 so It would be a sensible time to look for ways to give it a bit more poke. The proble is that the only ways that I can see of doing it are fairly hefty engineering projects.

Anyone help?

Jim D

[magicniner]

Reducing the volume of the compression chamber should give you the lift you're looking for, It'll never get near HW45 output but a small improvement should be possible.
Other options would definitely involve more engineering,
Regards,
Nick

[Target Bunny]

Reduce the volume.
I thought of that, But How?
According to the exploded diagram the release valve does not allow for adjustment to the volume it is simply a release valve. The reservoir is a single piece (I think. There is an interesting slot on the front so perhaps not.) and I can see no obvious way of shimming it. Possibly a tube inserted into the inlet but I have no idea if that would foul anything. A largerd pump definately but that will be pushing things to the limit as the pump walls are pretty thin already amd there is no roo for a longer stroke.

Jim D

[jefL]

SSSSH Jim stop singing the praises of this pistol, at least until I've bought one, it has just come to the top of my wanted list and I am about to start actively seeking one. I'd rather peolple didn't rethink their opinion of the Nemesis, that way they may be more likely to sell, or sell cheaper, to ME!

Now to your problem. You need to add something to the front of the piston to use up volume in the compression chamber. Start with a lump of blu-tack so you don't do any damage to the valve innards. Sticking metal or plastic discs of varying thickness to the front should do it. If you can get hold of any you can use shellac as an adhesive (sometimes sold as button polish). You can then soak the piston in meths to release the disc and try a thicker one. Check that the meths doesn't attack the plastic if using plastic discs. Once you arrive at the right thickness you can use a more permanent adhesive such as araldite. The ultimate solution would be a domed or extended piston. I'll get right on it when I have a Nemesis to play with.
Anyone got one for sale?

Oh, and best not mention the meths bit to Nick, he'll only end up drinking it all.

[harvey_s]

Be very careful if you're adding anything to the front of the piston.
If the compression chamber has been designed correctly, there is no lost volume at the end of the compression stoke as all the air is compressed into the valve unit.
Anything you put in there will be difficult to 'feel' as the overlever loads up under compression and your'e on the the end of a big lever so it will be easy to damage the internals - I've seen a few nemisis' before and generally if I remember correctly they are already quite pokey for their 'genre' so any gains I would have thought outweigh the risk of buggering it up...

[magicniner]

Air chamber, ptfe sleeve,
Job done,

Nick

[Target Bunny]

Jef
If I reduce the size of the compression chamber I reduce the ammount of air being compressed and so the power output. Remember that this is a SSP pistol. If you mean the reservoir I am still trying to work out how to do that. Maybe Nick's idea will work I just want to avoid having to take it all down again.

Regards
Jim D

[Nemesis]

Can't say I fancy pulling any of mine apart but fitting a .25 barrel uplifted the power a touch on one of them. This was fine for Silhouette Pistol comps, where downrange energy came in handy. Didn't do much for the line of flight, though!

D.

[Adam77K]

Jim, what they're talking about is reducing the final compressed volume by removing some of the "dead space", thus increasing the compression ratio.

Yes this will slightly reduce the overall air volume pushed into the cylinder at atmospheric pressure, but the increased pressure at the end allows more energy to be stored in the remainder of the air. That's the theory anyway. Just guessing at figures here but if by doing this you reduce the overall air charge by say 5% but this doubles the compression ratio you will put more energy into the charge.

See here for practical example.

I started a thread on here last year about upping the power of my HW75. It was all theory and didn't go anywhere but we discussed some of the same issues.

Adam

[magicniner]

Jef
If I reduce the size of the compression chamber I reduce the ammount of air being compressed and so the power output. Remember that this is a SSP pistol. If you mean the reservoir I am still trying to work out how to do that. Maybe Nick's idea will work I just want to avoid having to take it all down again.

Regards
Jim D

Jim,
exactly the procedure Jef suggests works on other SSP pistols, including the Gamo Compact. The amount of material added to the piston makes no significant reduction to the amount of air compressed, it does however increase the compression ratio significantly. You'd need to determine how much space there is first, personally I'd use plastigauge to measure clearance but little blobs of PlayDoh stuck to the piston then lightly oiled to stop them sticking to the inside of the cylinder & pulling off could be used.
I do like my idea though, I'd turn & mill it but it is an easy DIY job possible with very limited tools too
Regards,
Nick

[Target Bunny]

HI guys
Snag is that I haven't taken the gun apart yet. So I am guesing at HOW the whole thing works. The ED shows the rear of the reservoir and nothing about the arrangemnt of the front part.
On reflection I have to assume that it is an open chamber with the front of the pump forming the seal. If this IS the case the method mentioned of shiming the piston will work but Nick's idea of sleeveing the chamber will also work and be a more elegant solution since you will not need to mess around with shims. In eiither case I will still have to open the pistol up to get a definate answer.

Regards
Jim D

[harvey_s]

It's also worth considering that any worthwhile increase in 'poke' will probably entail a significant increase in cocking effort and that over a number of shots might make the gun more taxing to shoot - this will invariably lead to a loss of accuracy - ain't physics a bitch

[Rich]

I've got two of them here, a 177 and a 22.

The issue really is making sure that you don't lose any of the potential power, and both of mine have showed signs of leakage at the breech seal. This wasn't due to the seal being damaged or worn, it was due to the barrel shifting marginally forward after repeated use, meaning that the closing pressure on the breech seal was slightly backed off.

Resetting the barrel and making sure the clamps were tight did the trick.

I teach some lads on Wednesdays and sometimes we do some pistol shooting using the 177 at 6 yards, paper target, thick polystyrene slab behind to catch the pellets as they hit the 9mm ply backstop. It didn't take many shots before the 9mm ply had a hole through it, behind the bull.

How much power do you want from a pistol?

Trigger adjustment is quite easy but overdo it and you'll lose the second stage, then you have no indication it's about to release and that's horrible to use.

[Rob M]

This would involve modifying the cylinder or making a new one, but I noticed that on my Nemesis, the piston clears the inlet port on the cylinder before it gets to the end of the stroke. If you could get a new cylinder made, or block the existing inlet port somehow, and have a new inlet port right on the end of the piston's travel so that the cylinder held more air at the beginning of the stroke, that would get you a little more power. Probably not very much but it would help. The only other way is to up the compression by modding the piston as described by the other chaps above. Upping the compression by either method could result in more load on the valve and result in shorter valve seal life though.

[gedfinn 2]

This is probably one ofthe most underated pistols of all time and I am chuffed to bits with mine. BUT, does anyone know of a tune up that will give just a bit more power?
I want to do some work on the trigger of my .177 so It would be a sensible time to look for ways to give it a bit more poke. The proble is that the only ways that I can see of doing it are fairly hefty engineering projects.

Anyone help?

Jim D

Yes ! It can be done, It would make a good TSP ?
IE, swept volume be changed , What can, ? Cheers,