A Walther LGV question for the tuners out there

[neil180]

NickG - I have just tagged you in a picture of my LGV stripped on the Walther LGV/LGU facebook group. It shows the standard piston design.

[NickG]

In fact thinking about it - one of your alloy pistons would probably do the job if you can get the thing to cock the gun without destroying the shape of the piston where the cocking arm pushes against the rear piston ring housing. I would want parachute seal rather than O ring though which is the anti christ for you isn't it NicK??

I do like o rings. I tried an lgu seal in one of my experiments and didn't like it, thinking of either an ally piston with a steel ring threaded into the skirt, or a radically lightened standard piston, I have an lgu service kit here will have a look, is the piston the same ?

[neil180]

I'm really not sure without measuring things or taking my gun apart. If I wasn't going out tonight I would be tempted to pull it to bits to have a good old measuring session on it.

So - radically lightened LGV piston - you fancying the job?

[Shed tuner]

but as you know, *just* lightening the piston won't make the gun shoot better. We need to modify it so it doesn't *need* the weight first... maybe chop 10mm off the stroke, for example ? I'd try an ally piston (with built in extension) and a rear steel bearing flange for the cocking, just to avoid it digging into the ally...

[NickG]

I had a look at neils pictures, and measured my own piston, I don't think there is enough material in the skirt to machine enough off to achieve the required weight loss, if the cocking link runs on the outside of the action and not the piston, there is no reason why a series of slots cant be machined into the skirt to lighten it, will do a few sums and see if it will lighten it enough.

Yes I can lighten the lgv piston by the required amount

[NickG]

but as you know, *just* lightening the piston won't make the gun shoot better. We need to modify it so it doesn't *need* the weight first... maybe chop 10mm off the stroke, for example ? I'd try an ally piston (with built in extension) and a rear steel bearing flange for the cocking, just to avoid it digging into the ally...

I agree the weight loss coupled with the piston head I use on the lgu to shorten the stroke would work, depends on the transfer port volume.

[Snooper601]

I agree the weight loss coupled with the piston head I use on the lgu to shorten the stroke would work, depends on the transfer port volume.

Iirc it's 26mm long by 2.6mm diameter, a bit on the large size, volume wise, compared to the LGU.

Cheers

John

[NickG]

Iirc it's 26mm long by 2.6mm diameter, a bit on the large size, volume wise, compared to the LGU.

Cheers

John

Thanks snoop, I will do some sums

[neil180]

So whats your plan then Nick??

[NickG]

So whats your plan then Nick??

just need to compare the port volume to the opened up lgu ( it looks to be about double) though the volume doesn't give the whole story cross sectional area plays a part also, so it may be that it needs trying out. the plan would be three slots in the piston skirt a la your hw80 piston, with the standard spring and seal , or stroked using a poly head with o ring, and a no 9 spring.

[Snooper601]

just need to compare the port volume to the opened up lgu ( it looks to be about double) though the volume doesn't give the whole story cross sectional area plays a part also, so it may be that it needs trying out. the plan would be three slots in the piston skirt a la your hw80 piston, with the standard spring and seal , or stroked using a poly head with o ring, and a no 9 spring.

That'll be 4 times the standard LGU port then plus the extra lost volume due to the shape of the front face of the standard LGV seal, the central pip causes this extra volume.



Cheers

John

[joffy]

just need to compare the port volume to the opened up lgu ( it looks to be about double) though the volume doesn't give the whole story cross sectional area plays a part also, so it may be that it needs trying out. the plan would be three slots in the piston skirt a la your hw80 piston, with the standard spring and seal , or stroked using a poly head with o ring, and a no 9 spring.

sounds good

[NickG]

That'll be 4 times the standard LGU port then plus the extra lost volume due to the shape of the front face of the standard LGV seal, the central pip causes this extra volume.



Cheers

John

I don't like the lgu seal due to the lost volume, haven't used the lgv so cant comment, an o ring head would address this problem, if a stroke nearer to standard was required I can make a poly head the same dimensions as the original seal.

[Snooper601]

I don't like the lgu seal due to the lost volume, haven't used the lgv so cant comment, an o ring head would address this problem, if a stroke nearer to standard was required I can make a poly head the same dimensions as the original seal.

Hi Nick, the seals are basically the same design but with an 'outie' on the LGV and an 'innie' on the LGU.

RE:- your o-rings, we tried the 'Gloop' in Clez's 23mm (?) 77 2 bashes ago, the one that he said detonated within 3 shots with every lube be had tried. Well, last bash he said that it didn't detonate with mine... even though he said that the lube was migrating forward of the o-ring seal which he's now trying to sort out.

PM me if you want to experiment...

Cheers

John

[neil180]

just need to compare the port volume to the opened up lgu ( it looks to be about double) though the volume doesn't give the whole story cross sectional area plays a part also, so it may be that it needs trying out. the plan would be three slots in the piston skirt a la your hw80 piston, with the standard spring and seal , or stroked using a poly head with o ring, and a no 9 spring.

So 3 slots would remover the required weight?? And I could use one of your poly heads so I could easily remove it and replace it with the standard seal? Sounfs very interesting. How much weight do you reckon three slots would remove??