Indians For Guns

When you make your airgun 'diesel', you will scorch the piston washer and it can also break your main-spring. So stop mucking around.

Velocity at the muzzle is determined by pellet weight and pellet fit, not pellet shape.

Mack The Knife

Mack The Knife Bana";p="11457 wrote: So stop mucking around.

Velocity at the muzzle is determined by pellet weight and pellet fit, not pellet shape.

Yes.That was a one time experiment Will changing the piston washer to a different one make any difference?

>not pellet shape.

Thought so.But then a post on this forum said 'They are light weight, provide maximum velocities' (about wadcutters)

here's the topic
http://indiansforguns.com/viewtopic.php ... es+pellets

Pran

Pran";p="11458 wrote:Will changing the piston washer to a different one make any difference?

Most definitely. Whilst you are at it, change the main-spring and breech washer, if needed, as well.

Remember to lube the parts as I told you.

Mack The Knife

Mack The Knife Bana";p="11460 wrote: Most definitely. Whilst you are at it, change the main-spring and breech washer, if needed, as well.

Any particular make/brand of spring and washer you recommend?(and where can I pick them?)

Would like you to have a look at the insides once the rifle is taken apart.

Pran

Any particular make/brand of spring and washer you recommend?(and where can I pick them?)

You can make a PTFE (more commonly known as Teflon) piston washer if your piston is the type on whose face the piston washer can be screwed on.

The main-spring is a problem though. I have had sample springs made in Bangalore for old Dianas and they were crap. As I see it, your options are (in no particular order):

1) Send your existing spring to either Venom or Macarri and have them replicate it - the newer one will always be a little longer.

2) Have one made locally, if you know someone who makes good springs.

3) Buy one from the manufacturer of the rifle.

4) Look for a suitable one in the local gunshops.

Mack The Knife

Make a washer?They are not readily available?

Will do some searching the for spring the next time I'm near city market area.

Remember being told by the gun shop fellow that he sells the spring for my rifle.But then how do I tell if a spring's not good or is at the end of it's usable lifetime?

Pran

Make a washer?They are not readily available?

No idea if they are available or not for your air-rifle.

But then how do I tell if a spring's not good or is at the end of it's usable lifetime?

Your chrono readings for one and the fact that you deliberately made the gun diesel heavily are enough for me to want to change the main-spring.

Also, if the main-spring looks 'bent', I would change it. Having said that, I have seen consistent performance from an air-rifle whose main-spring has broken in three parts. Think this was Akshay's (a member here) HW77K. However, more often than not, the spring will bind and you wont be able to cock the gun.

Mack The Knife

Yes, the main spring did appear to be bent the last time I opened it.

What's the lifetime of a good spring?

mine's done about 1600-1800 shots.

Pran

Assuming you don't fool around, I'd say 7,500 to 10,000 shots at least. In some cases mine have shown a slight increase in power past the 4,000 to 5,000 shot stage.

Besides the usual reasons like excessive dieseling, etc. using very heavy pellets (e.g. 18 grains and upwards in .22" calibre) will also reduce the main-spring life. However, this is something I have read about and not experienced myself as I use medium weight pellets.

Mack The Knife

okay.thanks for the information.

Pran

Mack The Knife,
My rifle has an improved power of 50fps(around 350) even after firing about 80-100 rounds(after dieselling).The results are consistent now.A friend opines that the dieselling could've sealed a leak in the washer.Is that true?

Pran

A friend opines that the dieselling could've sealed a leak in the washer.Is that true?

Utter rubbish!

What has happened is that the excess oil has been burnt off and the gun has now settled down to a consistent velocity. How long it lasts is anyone's guess.

Mack The Knife

Mack The Knife Bana";p="12248 wrote:

A friend opines that the dieselling could've sealed a leak in the washer.Is that true?

How long it lasts is anyone's guess.

Am getting the spring and washer on 16th then

Pran

"Also, if the main-spring looks 'bent', I would change it. Having said that, I have seen consistent performance from an air-rifle whose main-spring has broken in three parts. Think this was Akshay's (a member here) HW77K. However, more often than not, the spring will bind and you wont be able to cock the gun."
Yes, miracles do happen - reminds me of years ago when a friends father brought his Audi 100 round complaining that for the last 5,000 miles or so the engine had been knocking a little, especially on starting. It sounded decidedly peculiar but we couldn`t find anything obviously wrong with it and eventually decided to drop the sump. The problem was then plainly apparent - the crankshaft had snapped in two ! The fracture was at an angle which allowed to whole thing to rotate almost as per normal.
Mack The Knife, have you heard about the automatic dieseling device that was invented about.......maybe forty odd years ago ? ( in the 1950s probably. ) I remember seeing and reading about it in a book that I got from the public library. The rifle soon became useless without the device as the spring softened so much however it performed with consistent velocity using the device ( which was fundamentally an oil reservoir and dropper. ) I`m trying to remeber what the guys name was.......maybe something like Gerald Cardew ?

Grumpy,

Gerald Cardew was the boffin of airgun boffins and it could very well have been him as he did experiment with dieseling. However, I do not recall anything about an automatic dieseling device.

The book must have been - The Airgun From Trigger To Muzzle or the revised version The Airgun From Trigger To Target.

Incidentally, he was born in Nainital, India.

Mack The Knife