Sweet shooting 77k ‘recipe‘?

[Shed tuner]

Thanks, the one that is in will be a No.1 as that’s the recommended one for the 77. I can always re-deploy it into another rifle.

if the softer spring doesn't do it, you must have a sealing issue... breach seal maybe if the piston seal looks good.

[lightning22]

if the softer spring doesn't do it, you must have a sealing issue... breach seal maybe if the piston seal looks good.

Thanks Jon,

Just out of interest, the link below should take you to the piston and chamber as they came out of the rifle. I’ve just had a suggestion via PM that it could be a modified LGV piston, not something I’ve any experience with?

https://drive.google.com/file/d/1Rnr...w?usp=drivesdk

[T 20]

Just out of interest, the link below should take you to the piston and chamber as they came out of the rifle. I’ve just had a suggestion via PM that it could be a modified LGV piston, not something I’ve any experience with?

https://drive.google.com/file/d/1Rnr...w?usp=drivesdk

From the image shown, is the rear bearing holder brazed onto the piston ?

It doesn't look like an LGV piston, but it does look very much like an early Venom altered one.

Another area where the compression tube can leak which hasn't been mentioned, is around the end plug which apparently is screwed into the tube.
From memory the test for this is to push the piston into the comp tube with the transfer port blocked while the whole lot is submerged under water --- then look for bubbles coming from the joint.


All the best Mick

[prosport.177]

From the image shown, is the rear bearing holder brazed onto the piston ?

It doesn't look like an LGV piston, but it does look very much like an early Venom altered one.

Another area where the compression tube can leak which hasn't been mentioned, is around the end plug which apparently is screwed into the tube.
From memory the test for this is to push the piston into the comp tube with the transfer port blocked while the whole lot is submerged under water --- then look for bubbles coming from the joint.


All the best Mick

Hi Mick, )

I wondered if it was a modified lgu piston with a hw rod set in place . But you have asked the right question, is the rear ring brazed on ? If so it is not a lgu piston ,)
From a conversation I had with Steve yrs ago I am sure he said the ring that was cut off the comp tube too shorten it was then used and brazed on the piston to act as the bearing for the 3 buttons that were machined into them. This was done on the early lazaglided system

[lightning22]

From the image shown, is the rear bearing holder brazed onto the piston ?

It doesn't look like an LGV piston, but it does look very much like an early Venom altered one.

Another area where the compression tube can leak which hasn't been mentioned, is around the end plug which apparently is screwed into the tube.
From memory the test for this is to push the piston into the comp tube with the transfer port blocked while the whole lot is submerged under water --- then look for bubbles coming from the joint.


All the best Mick

Hi Mick,

I’ll have a look at the piston skirt and update, it gives the impression of being all machined from the same bit of stock.

Rich

[T 20]

Hi Mick, )

I wondered if it was a modified lgu piston with a hw rod set in place . But you have asked the right question, is the rear ring brazed on ? If so it is not a lgu piston ,)
From a conversation I had with Steve yrs ago I am sure he said the ring that was cut off the comp tube too shorten it was then used and brazed on the piston to act as the bearing for the 3 buttons that were machined into them. This was done on the early lazaglided system

Yes Charlie, I've just been looking at images of the early Venom 77 piston with buttons. :-

image.jpg

The altered piston I was thinking of was Steve's Vmach piston. :-

image.jpeg

I'm not sure if Steve ever brazed the bearing housing on of whether he machined a whole new piston.
Obviously brazing the rear bearing housing on would be the cheapest way of modifying a customer's piston compared to machining up a completely new piston.



All the best Mick

[T 20]

Hi Mick,

I’ll have a look at the piston skirt and update, it gives the impression of being all machined from the same bit of stock.

Rich

I only asked as I thought I could see a hint of a bronze line in your picture, Rich.



All the best Mick

[BTDT]

I only asked as I thought I could see a hint of a bronze line in your picture, Rich.



All the best Mick

I thought the same, Mick.

It would be interesting to know the weight of the modified piston assembly.

[T 20]

Just to put the LGV idea to bed, I realised I have both a HW77 and LGV Pistons in my spares box.

So for comparison I took a picture. :-

image.jpg



All the best Mick

[T 20]

I thought the same, Mick.

It would be interesting to know the weight of the modified piston assembly.

It should be possible to calculate it pretty closely Jim, as we already know the HW77 piston weight and there are tables on the net giving the weight of bright steel bar per meter.

Saying that, even though I have calculated the final weight of Pistons I'm about to make I find it much easier just to make a piston and weigh it afterwards and then address any weight issues.



All the best Mick

[lightning22]

I only asked as I thought I could see a hint of a bronze line in your picture, Rich.



All the best Mick

Hi Mick,

If it is brazed it’s a tight job and it doesn’t go all the way through.

https://drive.google.com/file/d/1r63...w?usp=drivesdk

https://drive.google.com/file/d/1CCN...w?usp=drivesdk

https://drive.google.com/file/d/1E0D...w?usp=drivesdk

The weight hovers between 227g and 228g on the scales

https://drive.google.com/file/d/1LH7...w?usp=drivesdk

Sorry for all the links..

[BTDT]

It should be possible to calculate it pretty closely Jim, as we already know the HW77 piston weight and there are tables on the net giving the weight of bright steel bar per meter.

Saying that, even though I have calculated the final weight of Pistons I'm about to make I find it much easier just to make a piston and weigh it afterwards and then address any weight issues.



All the best Mick

Absolutely, Mick. Much easier to weigh than calculate.

I wonder whether the buttons on the cylinder locate in holes that reach the cylinder end thread? That could be a possible air leak.

[BTDT]

The weight hovers between 227g and 228g on the scales

.

Then the weight won't be an issue.

[T 20]

Hi Mick,

If it is brazed it’s a tight job and it doesn’t go all the way through.

https://drive.google.com/file/d/1r63...w?usp=drivesdk

https://drive.google.com/file/d/1CCN...w?usp=drivesdk

https://drive.google.com/file/d/1E0D...w?usp=drivesdk

The weight hovers between 227g and 228g on the scales

https://drive.google.com/file/d/1LH7...w?usp=drivesdk

Sorry for all the links..

Hi Rich

That does look to be machined from solid and not brazed so I'm tending to think it's a Vmach setup.

The only other firm I know of who produced such a setup in any quantity was Target Tune India but their seals and bearings were blue in colour.

Hopefully Mach1.5 should be able to identify if it's a Vmach or not.

I wonder whether the buttons on the cylinder locate in holes that reach the cylinder end thread? That could be a possible air leak.

Strangely Jim.

The thread where I remember a chap from Malta having an air leak from the end block also involved a buttoned cylinder, from memory he returned the cylinder to the maker for remedial work.




All the best Mick

[prosport.177]

Piston def looks like it is machined from solid or tube machined down.
To to be honest any capable machinist could make the piston. .)
Is the piston rod threaded into the piston nose?