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rsterne · Moderator

OK, so now I understand what I'm looking at.... there is obviously a matching chamber in the gun where the air from that groove is collected and then proceeds to the barrel to fire the pellet....

You first have to find the source of the greatest restriction to the flow.... It may be the valve, the groove, the collecting chamber, or (most likely) the hole that the air passes through between there and the barrel (called the transfer port).... It could also be where the flow changes direction (often 90 degrees).... Ultimately, you have to cram all that air through the barrel port(s).... which could be a single hole (ala Crosman 22XX/Disco).... or another series of holes in a groove (ala RWS 850).... In a .22 cal airgun, a single barrel port is unlikely to be much bigger than 4mm (12.6 sq.mm).... otherwise the pellet will hang up on loading.... When they "flow mod" the barrel on an 850, they only work on the hole that lines up with the transfer port (drilling it to 4mm), ignoring the other three as the flow has to make too many turns to get to them.... Making that one hole bigger produces all the gain available.... That could well apply to your design.... I imagine they use multiple holes to eliminate alignment issues when the tank is screwed in....

As an example, let's say you have 6 holes of 2mm diameter in that valve.... That is a total area of 18.8 sq.mm..... If the transfer port between the valve and the barrel is, say, 5mm.... that would have a total area of 19.6 sq.mm.... almost the same.... If, however, the transfer port was only 4mm.... it would have an area of only 12.6 sq.mm.... and obviously that would be the biggest restriction to the flow.... It is also possible that the hole in the exhaust seat INSIDE the valve (which will have a valve stem in the way).... could easily have an area smaller than the 6 holes you show in that pic.... If it was 5mm but had a 3mm stem in the middle.... it would have an area of only 12.6 sq.mm....

Changing the diameter of those holes may give you a boost.... or it may not.... It all depends on where the flow is being restricted.... I won't address the safety issues because there are too many variables.... There, you are on your own....

Bob

cissp22 · Member

very nice points , thanks .

ok , i cant do any changes to inside valve and chamber which seems to be first airflow conrol , also its impossible to widen the 90 degree hole leading the pellet ...

the only 2choise is widening this 6 holes and more strike of hammer ...

and these 2 may not lead me to 50 FPE Neutral

..

cissp22 · Member

rsterne ,

as u see i m going to widen all channels leading air to the pellet ...

but what i need to know is where is the most important part to open more ? also is it so important to widen the channel backside the pellet??

thanks ,

rsterne · Moderator

I can't tell anything from your photos or description.... Is that the same valve you showed in the earlier photo?.... If so, what is the air path.... Which way is the valve stem facing?.... Where does the white plastic part go?.... What do you mean by "the channel backside the pellet"?....

Bob

cissp22 · Member

resterne ,

sorry , channel backside the pellet means = transfer port ,hole that the air passes through between there and the barrel .

this is another photo , what i want to do is making all holes wider from top to bottom .but dont know what is the most important part ...

http://www.airrifle.co.za/attachment.php?attachmentid=3565&stc=1&thumb=1&d=1249234679

thanks ,

huub74 · New Member

in the link you find a pic of a modifed valve of the hatsan. (.25)
and also the original compared to the modified one
These are a links to the dutch airgun forum, they performed a very nice review with also a nice triggertune.
If you have trouble translating some parts, you can pm me.

Also inside the hammer you find a bolt where you can adjust the preload of the hammerspring.

http://www.luchtbuks.net/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=49810
http://www.luchtbuks.net/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=58731

rsterne · Moderator

Without dimensions I have no answer for you.... Measure and calculate the area of each hole that the air has to go through (including obstructions like the valve stem).... and then work first on the one that has the smallest area....

This is not rocket science....

Bob