When cutting down a barrel...

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I can get 820fps out of a 7.6" barrel with 16gr .22 in my 1322 pcp.

My Crown with 15" barrel likes to send them at 960fps

The same Crown still sent them at 800fps thru a 7" barrel.

Everyone says 10-15fps by rule of thumb but I feel this is on longer barrel lengths. But going real short (5-6" or less) can cause drops of as much as or more than 50fps per inch.... Generally speaking... for a pcp rifle, I would want a 14" barrel at minimum. Springers tend to lose less fps per inch. Single digits.
 
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I think the rule of thumb, was based on testing with a dump valve. ie a very inefficient shot that wasted allot of air. So, as the barrel got longer, it became more efficient, and it was more linear. I saw near linear when I was playing around with all sorts of 1377 configurations. On a Prod, I had tuned with O-ring buffer, I changed out the stock 12" barrel for a 20" Mrod barrel. I didn't change any of the settings, ported, etc. Just barrel. Power only went up slightly for the 8" of extra barrel, nothing close to "rule of thumb" that many were going by. 

So, if your currently have your gun tuned for high power and you shorten the barrel, you will see more power loss that if you have a reasonably efficient tune.




 
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I have had 3 barrels in 22 cal I had to cut down due to imperfections , Now I know for sure I cut 1 inch off each one , this being said , 2 barrels lost about 8 fps both of these were cut at breech end and then refitted /

Now the last one I had cut 1 inch off I know it sounds weird but it gained 11 fps , however it was cut off the choked end , So I am to assume I had removed choke due to some horrible gouging near end of barrel so it went up from less friction

SO I would take this into account which end you cutting as for what outcome will be also all guns were lower powered 30 fpe guns

LOU
 
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10-15 fps is what I have experienced, EXCEPT choke removal, the tight chokes can slow down a projectile and if that is the case, you lose little or no fps.



Regards,



Roachcreek
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Hi

What is better to remove the choke or the breech side?

Regards 

Enkey
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Depends on how good the barrel is. If there are no high or low spots, it should be fine to remove the choke... if unsure.... remove the breech end. 
 
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