N/A Tuning unregulated PCPs for a longer flatter shot string

[nobody1]

This post describes the main mod I am using to get longer flatter shot strings for unregulated PCPs.

I use a finely tuned, 3D printed (from TPU) buffer placed between the valve and hammer.
The buffer needs to be slightly larger than the inner diameter of the air tube so that it does not move.
The height of the buffer is essential, 0.1mm can change velocities by 30+ FPS.
The hammer spring is close to the max preload, this allows you to start at higher pressure.

I got to those tunes through trial and error, many of both.

I have tuned many unregulated PCPs using the same valve hammer buffer mod.

Since I target shoot I want at least 4 magazines worth in every shooting session at a low velocity spread (less than 5%).

I tuned both my Beeman Raider for 4+ maqazines worth of shots (48 in .177, 40 in .22) with a tight FPS spread.
These are their current tunes.

Beeman Raider .22
Pellet: CPHP 14.3 grains
Pressure: 4000PSI to 2600PSI
Velocity: 685-712 FPS
Shots: 40+ (4 mags + some extra)

Beeman Raider .177
Pellet: Norma domed 9.1 grains
Pressure: 3800/3900 PSI to 2500PSI
Velocity: 840-863 FPS
Shots: 50+ (4 mags + some extra)

I tuned my Hatsan AT44 too.

* Hatsan AT44 .22

Pellet: CPHP 14.3 grains
Pressure: 265 bar to 175 bar
Velocity: 800-833 FPS
Shots: 55 shots

These are some other tunes, but did not record details.:
-Diana Bandit .177, 4 magazines around 450 FPS with 7.5 grain pellets
The spread of this was around 35-40 FPS, so closer to 8%.
This one was the hardest one tune because of the very small air cylinder (40cc I think).
-Beeman 2027, 4+ magazines (48+ shots)
Velocity around 600 FPS, spread less than 5%.

 

[nervoustrig]

Nicely done! A hammer buffer is a great way to squeeze out more shots from an unregulated PCP. I was interested in calculating the efficiency but apparently the tube volume is an industry secret.

Please be careful overfilling.

 

[OldVet]

Nicely done! A hammer buffer is a great way to squeeze out more shots from an unregulated PCP. I was interested in calculating the efficiency but apparently the tube volume is an industry secret.

Please be careful overfilling.

I really like learning things , and this Nation is just awesome. I like a regulator , so I can be a part of what I'm doing but when I seen the unregulated aea .30 cal bullpup review the 24 " barrel for only 459 I believe. I was like just intrigued by it. I had no idea a unregulated PCP could be tuned. You said trial and error , so these buffers are not a set item you can buy ?

 

[nervoustrig]

these buffers are not a set item you can buy ?

Not really. I mean I can’t say there was never a hammer buffer kit sold but the trial-and-error nature of it isn’t well suited to it. The most common approach was stacking O-rings behind the valve. It was popularized by an airgun enthusiast by the name bstaley, and the online community adopted the term bstaley O-ring buffer for it. Searching the word bstaley will turn up scads of threads.

Been a while since I’ve done a bstaley writeup but here’s an introduction that might be helpful for starters

Tuning - How to maximize consistent power shot count on Benjamin Akela .22

I just bought a Benjamin Akela .22 to use for target shooting only in my 10 meter Olympic target range. I do not need high power but consistent velocity and maximum shot count per fill. I would prefer not to install a Lane regulator just now since I do not wish to void the 5 year warranty. I...

www.airgunnation.com

 

[nobody1]

Not really. I mean I can’t say there was never a hammer buffer kit sold but the trial-and-error nature of it isn’t well suited to it. The most common approach was stacking O-rings behind the valve. It was popularized by an airgun enthusiast by the name bstaley, and the online community adopted the term bstaley O-ring buffer for it. Searching the word bstaley will turn up scads of threads.

Been a while since I’ve done a bstaley writeup but here’s an introduction that might be helpful for starters

Tuning - How to maximize consistent power shot count on Benjamin Akela .22

I just bought a Benjamin Akela .22 to use for target shooting only in my 10 meter Olympic target range. I do not need high power but consistent velocity and maximum shot count per fill. I would prefer not to install a Lane regulator just now since I do not wish to void the 5 year warranty. I...

www.airgunnation.com

Here BStaley's original post (around 2011) for tuning the Marauder pistol:

Yellow Airgun Forum Archive-Poor man's M-Rod, P-rod, etc. "Regulator" explained (Long) - Original Bstaley Mod Topic

First of all, despite the title, this mod is not a Regulator at all. Truth is I don't really know what you would call it. Maybe one of you can com

www.tapatalk.com

I was definitely inspired by his post, which uses stacked o'rings as the buffer.
They work with the Marauder pistol/rifle because they have an adjustable hammer stroke.

99% of the airguns out there do not have an adjustale hammer stroke, the length of the valve stem is fixed.

This is why I 3D print the buffers to a very exact height.
A 0.1mm difference in buffer height can give you at least 20-30 more or less FPS.

The higher the buffer, the shorter the hammer stroke and the lower the velocity.

 

[Vetmx]

I skipped the whole packing orings in the hammer tube and just went with the patch from an inner tube on the face of the valve. It worked.

 

[markhooper]

I had a ars 6 PCP rifle years ago..it came with a 2 power settings.. you basically pulled the hammer back and it had a cone shaped faucet washer that was cut flat on the sides so you could put it over the valve stem in the screw hole and the two flats fit snuggly in the action and retained it..

if you are not familiar with that rifle I believe it is the same as the evinix ar6 but the evinix ar6 doesn't have the open sights.

also the Seneca eagle claw has a adjustable spacer on the power wheel that does a similar function.. basically the idea is to limit how far the valve opens.
Mark

 

[nobody1]

I skipped the whole packing orings in the hammer tube and just went with the patch from an inner tube on the face of the valve. It worked.

How do you use the inner tube?
Can you change the height of the buffer?

 

[OldVet]

I understand better now. It's controlling the valve lift. The more lift the more air.
To make a valve open more use a stronger spring , and the hammer will hit it harder thus opening the valve more for more air flow. The O ring buffer would decrease the valve opening by making the hammer a softer blow. Thanks guys I now know why all the talk of a heavier , or stronger hammer spring is doing .

 

[Vetmx]

How do you use the inner tube?
Can you change the height of the buffer?

You are really making me dig deep into my hard drive because it’s been so many years. I think I still have two guns with the patch installed. You buy an inner tube patch kit. You cut a patch the size of the face where the valve pin sticks out. Then you cut a little hole for the pin. Degrease, remove the adhesive skin then apply. One patch and some valve spring shimming always got the gun purring along for me. Some patches are thicker than others. I didn’t like the patches made by Slime. I can’t remember what brand I liked but they were thick.

It’s cool to see someone still extracting the most out of non slingshot hammered unregulated PCP”s. It was a great learning experience that so many will never get or ever understand.