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PostPosted: Wed Jul 17, 2013 4:16 am 
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Joined: Wed Jul 17, 2013 1:58 am
Posts: 4
good day, I know there is a lot of information on this subject but to get it clear me, could someone point me in the right direction. I have purchased ataros regulator and would like to do some work on the gun. What I would like to achieve is 900fps with the regulator at 100bar. JSB 10.?grain pellets. We dont have the same restrictions on power in South Africa.

1.Remove airtube strip and clean.
2.Adjust regulator to 100 bar
3.Block bottom 5 holes on the valve***(Help. Is this inside the tube HP side or on the valve stem where the O ring is)[/b]4.Fit new transfer port restricted to ,***(Help)2.5mm ?
5.Drill remaining top hole on valve to,***(Help) I have found figures, but for .22
6.adjust hammer spring all the way in (CCM)
7.Test and keep adjusting hammer spring till I get the FPS I require.
Any assistance would be appreciated, thank you


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PostPosted: Wed Jul 17, 2013 10:48 am 
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Joined: Mon Sep 05, 2005 10:55 pm
Posts: 6269
Location: Alberta
Welcome!

To block the holes you need to remove the threaded bushing in the gun tube that the reservoir tube and valve thread to.

By assembling the bushing onto the valve body you will see if the hole needs to be aligned. You can then make a decision about the plugging of the other holes.
I have not bothered with the plugging yet but may in the future. For economy I prefer a sail installed on the valve stem to assist in closing the valve after the shot.

To achieve 900fps you may need a bit more pressure but once you tune around the 100 Bar you will have an idea of the available power.

Please keep us updated on your progress.

Walter....

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PostPosted: Wed Jul 17, 2013 11:11 am 
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Joined: Wed Jul 17, 2013 1:58 am
Posts: 4
Thank you for the reply sir

I will be filling the cylinder to 200 bar, at your suggestion I will regulate at 115 bar and see what adjustment I need on the hammer spring to achieve 900fps

Could you please enlighten me as as to what a sail is, and how it achieves this.

Are the figures for transfer port restriction and top hole adequate at 2.5 mm to deliver the required air.

Thank you


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PostPosted: Wed Jul 17, 2013 11:16 am 
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Joined: Mon Sep 05, 2005 10:55 pm
Posts: 6269
Location: Alberta
I would tune and shoot your rifle a bunch before bothering to plug holes.

The sail I use is a 0.495" o.d. washer of about 0.100" thickness with an i.d. to suit the valve stem.

It slips over the valve stem guide for the valve spring. Being 0.100" thick adds valve spring tension and the diameter creates a restriction in the valve body bore to the flow of air. This results in a force acting on the 'sail' in such a way to aid the closing of the valve.

Make it of steel or brass possibly aluminum but NOT plastic of any sort.

I'll see if there is a pic out there.

Walter...

edit: found a pic of my BT65 valve apart with sail.

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PostPosted: Wed Jul 17, 2013 12:02 pm 
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Thanks for that I shall take your advice and go foreword one step at a time. I had never even heard of a sail, it shall be tried. A picture would be very helpful. I have had a trigger sent to me from Sniper, what a helpful man, that will be going on as well. I will let you know how it goes.


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PostPosted: Wed Jul 17, 2013 2:31 pm 
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Joined: Wed Jan 05, 2011 12:35 pm
Posts: 2198
Location: P.G. B.C.
kram - I followed Walter's advice by putting a sail in my BT65 .177. It reduced the speed only slighlty, but also reduced the air used, and raised my shot count. I have since plugged the excess holes and am getting fairly good shot to shot consistency. I am actually waiting for a regulator at this time. The 44's have a plastic plug that must be pried out, whereas the BT65 has the threaded one shown in Walter's picture.
My BT65, with the best valve, is putting out 960fps with a 10.5gr. Crossman Ultra Magnum pellet and has been shooting bug hole groups at 25 yards form a rest. Once the stock is finished, I'll be trying it for 25 and 30 meter bench rest.

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Weihrauch HW97 Blackline .177
Weihrauch HW98 .22
Feinwerkbau Model 150 .177
Hatsan BT65 .177
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PostPosted: Wed Jul 17, 2013 2:59 pm 
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Joined: Wed Jul 17, 2013 1:58 am
Posts: 4
Thank you for the advice. I am new to working with air rifles so all advice is welcome.there are people with a wealth of experience and I appreciate them taking the time to help someone new to this sport.


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PostPosted: Wed Jul 17, 2013 6:20 pm 
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Joined: Fri Jul 16, 2010 4:09 pm
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Location: Southern canada
Voltar this "sail" devices, does the washer just put more pre load on the valve spring? I might have to try this out my self, this must reduce "dwell" to some extent.

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PostPosted: Wed Jul 17, 2013 6:25 pm 
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Joined: Mon Sep 05, 2005 10:55 pm
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Location: Alberta
Knappr wrote:
Voltar this "sail" devices, does the washer just put more pre load on the valve spring? I might have to try this out my self, this must reduce "dwell" to some extent.


yes, please see above.

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PostPosted: Fri Jul 19, 2013 10:30 am 
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Joined: Wed Jan 05, 2011 12:35 pm
Posts: 2198
Location: P.G. B.C.
Instead of the air pressure in the reservoir only pushing on the small diameter of the stem's rear surface, it is pushing on the much larger back surface of the sail which is pressing against the stem, thus it seems to close more quickly, wasting less air. That is how I understand the sail. When I installed the sail, I lost a small amount of speed, but gained shot count and more consistent velocity readings. I forget how many shots I gained now - it was a lot of pellets ago. Such an easy 'mod'.

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Daryl

Weihrauch HW97 Blackline .177
Weihrauch HW98 .22
Feinwerkbau Model 150 .177
Hatsan BT65 .177
Bam 51 .22
Bam28C .22


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