Flat Top Pistons - What are the advantages?

Flat Top Pistons - What are the advantages?

Joined: November 5th, 2003, 8:29 pm

March 3rd, 2011, 5:23 pm #1

Please enlighten me as to the advantages/strengths/weaknesses of the Flat Top Piston on a 1377 with factory length barrel?

The goal of my next project gun is maximizing velocity in the 1 - 5 pump level with most importance in the 1 - 3 pump level for short distance target/plinking use.

Naturally I'd like the gun to be accurate, reliable and easy to service and the idea of using O-rings is intriguing.

Regards,

Tony
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Joined: September 6th, 2006, 3:27 am

March 3rd, 2011, 6:11 pm #2

The downside is that the O-rings wear out pretty fast compared to the cup piston.

This obviously means you have to replace the O-ring often. The best thing for that is to use a pivot pin with E-clips or some fastener to facilitate rapid removal.
The stock Crosman roll pin should be ditched, a solid pin in it's place.


Charles Mellon offers a great piece for this purpose.

Or you can make your own, like on this one :






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Joined: December 14th, 2003, 4:36 am

March 3rd, 2011, 6:26 pm #3

Please enlighten me as to the advantages/strengths/weaknesses of the Flat Top Piston on a 1377 with factory length barrel?

The goal of my next project gun is maximizing velocity in the 1 - 5 pump level with most importance in the 1 - 3 pump level for short distance target/plinking use.

Naturally I'd like the gun to be accurate, reliable and easy to service and the idea of using O-rings is intriguing.

Regards,

Tony
I think the flat top piston takes out the flex in the stock piston and the seal deforms less under pressure. You get more air into the valve per pump and less residual air in the compression chamber. I have the mellon delrin piston. I did dremel some notches along the circumference so I can adjust the headspacing with a screwdriver without tearing it down.
Last edited by autoduel on March 3rd, 2011, 6:27 pm, edited 1 time in total.
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Joined: May 25th, 2008, 4:38 am

March 3rd, 2011, 6:52 pm #4

Please enlighten me as to the advantages/strengths/weaknesses of the Flat Top Piston on a 1377 with factory length barrel?

The goal of my next project gun is maximizing velocity in the 1 - 5 pump level with most importance in the 1 - 3 pump level for short distance target/plinking use.

Naturally I'd like the gun to be accurate, reliable and easy to service and the idea of using O-rings is intriguing.

Regards,

Tony
durable...I'd focus on valve mod...or get a FT valve from Mellon,...plus,you can squeeze out a few more FPS by some tricks involving the transfer port...


Hey...you going to the Airgun Expo..??
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Joined: November 5th, 2003, 8:29 pm

March 3rd, 2011, 7:05 pm #5

The downside is that the O-rings wear out pretty fast compared to the cup piston.

This obviously means you have to replace the O-ring often. The best thing for that is to use a pivot pin with E-clips or some fastener to facilitate rapid removal.
The stock Crosman roll pin should be ditched, a solid pin in it's place.


Charles Mellon offers a great piece for this purpose.

Or you can make your own, like on this one :






So Charles is the one to contact for Flat Top Pistons?

REgards,

Tony
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Joined: November 5th, 2003, 8:29 pm

March 3rd, 2011, 7:07 pm #6

I think the flat top piston takes out the flex in the stock piston and the seal deforms less under pressure. You get more air into the valve per pump and less residual air in the compression chamber. I have the mellon delrin piston. I did dremel some notches along the circumference so I can adjust the headspacing with a screwdriver without tearing it down.
I can buy into that as far as the pump cup flexing under pressure. So Charles uses a Delrin piston, I seen metal ones on AC's website.

Good idea on the notches!

Regards,

Tony
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Joined: November 5th, 2003, 8:29 pm

March 3rd, 2011, 7:09 pm #7

durable...I'd focus on valve mod...or get a FT valve from Mellon,...plus,you can squeeze out a few more FPS by some tricks involving the transfer port...


Hey...you going to the Airgun Expo..??
due to daughter signing up for Basketball and announcement of first game on Saturday at 12:45pm...will try to drive up afterwards and meet up with y'all before the joint closes at 5pm...otherwise I'll see you guys Sunday morning!

So what's the 411 on da valve mods?!?!

Regards,

Tony
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Joined: May 25th, 2008, 4:38 am

March 3rd, 2011, 8:30 pm #8

and talk to him about the FT valves,...here is his site:

http://mellonair.com/index.php?p=1_11_FT-Piston-Valves
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Joined: February 25th, 2009, 1:05 pm

March 3rd, 2011, 9:15 pm #9

Mellon and AC offer valve power mods. I got parts from both, delrin fT, LDC from AC, Solid pin, power adjuster, stainless long probe from Mellon. It sure did a made of difference on my 1377. I plink with 4 pumps for 502fps, get rid of nutter up to 30 yrds with 707 fps with 10 pumps.
Last edited by Oragon2 on March 3rd, 2011, 10:24 pm, edited 1 time in total.
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Joined: November 19th, 2004, 4:39 am

March 3rd, 2011, 9:45 pm #10

Please enlighten me as to the advantages/strengths/weaknesses of the Flat Top Piston on a 1377 with factory length barrel?

The goal of my next project gun is maximizing velocity in the 1 - 5 pump level with most importance in the 1 - 3 pump level for short distance target/plinking use.

Naturally I'd like the gun to be accurate, reliable and easy to service and the idea of using O-rings is intriguing.

Regards,

Tony
http://www.airgunsmith.com/cros1377/cros1322-77.htm
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Last edited by ratite on March 3rd, 2011, 9:46 pm, edited 1 time in total.
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