LGV - The AGW "Simple tune" doesn't work for me

[Vernal]

I really like my LGV, bought second hand, which I resolved to keep to original spec. But my usual philosophy kicked in -its working perfectly, so what can I do to improve it - so when I read Jim Tyler's article in last months AGW (Jim Tyler's articles being probably the only reason I keep reading AGW to be honest) I couldn't keep my hands off it. New TX Mk III original spring from Chambers (brilliant service, ordered lunch time, arrived next morning) and half an hour later (including a degrease and sparing re-lube) the spring was in with 36mm preload (quite a lot of washers) which Mr Tyler said gave him 11.3 ft lbs. My chrono check said 6.4 fpe, so I added washers to give 40 mm preload, which Mr Tyler said gave him "far too close to the legal limit", and the gun wouldn't cock!
It took my almost octogenarian brain a few days to work out that this was because all the extra washers meant that the top hat was contacting the guide and limiting the travel of the latch rod so, next I took 5mm off the rear guide (easy job in a woodworking lathe, using woodworking turning tools) and with 40 mm preload the gun cocked, but energy only went up to 7.8 ft lbs. Walther spring back in and 22mm preload gives 10.4 fpe.
Has anyone else tried this, and if so with what result please? Or, can any one of the hundreds of people who know much more about the spring gun than I do please suggest why this "simple tune" might work for Mr Tyler, but not for me?

[Hsing-ee]

I find when dealing with a vexatious LGV it is best to sell it and buy a HW99S or an HW30S, which will reward thoughtful tinkering with superb performance.

Walts are supposed to be perfect out of the box so why fiddle with them? 40mm of pre-load sounds like a total armful of old washers, I'm surprised you could pick it up.

Seriously though, perhaps the TX spring is overspringing it with all that preload, try it without. Too much spring can result in lower fpe as well as higher fpe.

[Rapidnick]

I must agree with my friend above. However much you enjoy tinkering surely the LGV should be left alone and shot?? It is not a faultless gun but in my experience it is a very good gun available at silly low prices in the used market. I own a few high end springers and have shot probably all of the others I don't own and honestly the LGV is up there with any of them.

[BTDT]

Sounds like a tight piston seal. The AA spring has plenty of energy for the job, but places much less force on the piston at the start of the stroke, which is what gives the gentle recoil, but a tight seal can really drag the muzzle velocity down.

My LGV was one of the first in the country, and the seal has seen a lot of use and is an easy fit. HW30 piston seals work well without sizing.

[Vernal]

I find when dealing with a vexatious LGV it is best to sell it and buy a HW99S or an HW30S, which will reward thoughtful tinkering with superb performance.

Walts are supposed to be perfect out of the box so why fiddle with them? 40mm of pre-load sounds like a total armful of old washers, I'm surprised you could pick it up.

Seriously though, perhaps the TX spring is overspringing it with all that preload, try it without. Too much spring can result in lower fpe as well as higher fpe.

It is just the curse of the incurable tinkerer, I can't leave things alone, and the only two guns I have un-interfered with are a Lincoln Jefferies and an FWB300, cos I really can't think of any way of improving either of them.

[Hsing-ee]

It is just the curse of the incurable tinkerer, I can't leave things alone, and the only two guns I have un-interfered with are a Lincoln Jefferies and an FWB300, cos I really can't think of any way of improving either of them.

FWB300 you can relube with dry moly dust, and spend ages buggering about with different springs! It's not a quick strip so it takes a lot of patience. Best left alone ...

I think a nice old HW35 provides the perfect tinkerer's soup base. From sealing the 'voids' to fine-tuning the transfer port size, you could be tweaking that particular assemblage of parts for years... the over-squareness and inherent slight inefficiency means it would always be a work in progress.

[Vernal]

Sounds like a tight piston seal. The AA spring has plenty of energy for the job, but places much less force on the piston at the start of the stroke, which is what gives the gentle recoil, but a tight seal can really drag the muzzle velocity down.

My LGV was one of the first in the country, and the seal has seen a lot of use and is an easy fit. HW30 piston seals work well without sizing.

I am privileged to have your reply Sir, and you have probably hit the nail smack on the head. The piston seal was very tight, so I tried one that came out of my LGU (now fitted with a Nick G skirtless piston). I tried to size the LGV seal, which is blue unlike the green LGU, but I may not have been vigorous enough with the wet and dry, as it was still quite tight when I re-fitted it. I thought the seal couldn't be the problem as it works well with the Walther spring. I should have realised that, nothing being simple in airgun tuning, changing the spring might affect the response of the seal. Tomorrow I shall have another go at the seal and aim for an easy slide rather than the current very firm shove.

[Vernal]

FWB300 you can relube with dry moly dust, and spend ages buggering about with different springs! It's not a quick strip so it takes a lot of patience. Best left alone ...

I think a nice old HW35 provides the perfect tinkerer's soup base. From sealing the 'voids' to fine-tuning the transfer port size, you could be tweaking that particular assemblage of parts for years... the over-squareness and inherent slight inefficiency means it would always be a work in progress.

Oh dear, does that mean I have to buy another gun just to satisfy the tinkering urge? But I have to get an FWB Sport 124 first, so it will have to wait until that is secure.

[Hsing-ee]

Oh dear, does that mean I have to buy another gun just to satisfy the tinkering urge? But I have to get an FWB Sport 124 first, so it will have to wait until that is secure.

The FWB Sport has the least tinkering potential of any springer. It's so well engineered that it doesn't even need buttoning on its piston. The only thing it needs is the Jon Budd trigger mod, using a Maccari machined blade, and you are done. No fun at all!

[T 20]

The piston seal was very tight, so I tried one that came out of my LGU (now fitted with a Nick G skirtless piston). I tried to size the LGV seal, which is blue unlike the green LGU, but I may not have been vigorous enough with the wet and dry, as it was still quite tight when I re-fitted it. I thought the seal couldn't be the problem as it works well with the Walther spring. I should have realised that, nothing being simple in airgun tuning, changing the spring might affect the response of the seal. Tomorrow I shall have another go at the seal and aim for an easy slide rather than the current very firm shove.

Hi Mike.

Something you may have missed is that the LGV and LGU seals are different on the front face.

The LGV seal has a central tit with a circular void around it which coincides with the offset transfer port.

The LGU seal has a central void to coincide with the central transfer port.

As Jim says, the 25mm Weihrauch seal fits straight onto either the LGV or LGU piston.



All the best Mick

[Shed tuner]

your blue seal is probably a VAC 25 (vortek), as the Walther seals I've seen are all green..

[Vernal]

Hi Mike.

Something you may have missed is that the LGV and LGU seals are different on the front face.

The LGV seal has a central tit with a circular void around it which coincides with the offset transfer port.

The LGU seal has a central void to coincide with the central transfer port.

As Jim says, the 25mm Weihrauch seal fits straight onto either the LGV or LGU piston.



All the best Mick

Thanks Mick, I had noticed the difference in the centre of the seals, but had not appreciated its significance. The only Weihrauch seal I have is 26mm, so I will order a new 25mm one now, which will let me tackle resizing the Walther one (my next job) with a bit more vigour and no worries about going too far. I assume trial and error is the only way to go?

All the best, and look forward to seeing you again in September

[Vernal]

Hi Mike.


The LGV seal has a central tit with a circular void around it which coincides with the offset transfer port.

The LGU seal has a central void to coincide with the central transfer port.


All the best Mick

Just a thought - the Weihrauch seal has no void at all, does this matter?

[T 20]

Just a thought - the Weihrauch seal has no void at all, does this matter?

My TX made more power with the Weihrauch seal fitted than with an LGU seal, Mike.

[Vernal]

Thanks Mick, that's all I need to know