.177 port size ?
- Thread starter cosmic
- Start date
I'll start off by saying that I'm no expert on this, but just this morning I did open up the transfer ports on my .22 Kral. I went with a 0.164 inch (4.166 mm) drill and can confirm that in my rifle I'm getting 37 FPE now with JSB 18s and before I was getting about 31 fpe.
I realize this does not directly help to answer your question, but I think the answer will depend on your "needs"... I think we'll need more info to help you:
- What gun are you using
- What do you do with your gun (hunt, target shoot)?
- What pellet weight do you want to shoot and at what speed?
I think folks will want to see some baseline of what have now and you want to achieve before making specific recommendations!
Oh, you should definitely measure each port opening as part of your evaluation. For reference this what I started with on my Kral . 22 (I listed the smallest and largest ports with inch measurements.)
Transfer ports sizes:
valve = 3.7 mm
power wheel = 3.46 mm (0.136 in)
block = 4.05 mm (0.159 in)
barrel = 3.8 mm
FWIW, if you take 80% of your .177 caliber you get about 0.142 in. I think I read that 80% should be about your max port opening size. There are also considerations regarding how pellets load if you go to big...
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Well thanks.. I have a Nova Vista Liberty in .177.. I think it is maxed out from the factory... All the ports are 9/64" or .140... Trying to get the 15.5 NSA slugs to the 900's ... I chambered one and the rifling goes all the way up the sides.. Since the sides of them are straight I am wondering if I should size them down..
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Yup, it sounds like you're maxed out there Never shot slugs so I'll be interested in seeing how you do with them. Just out of curiosity, what velocity are you getting with them now? What hammer spring adjustment is there in the Liberty? I assume you're maxed out there too?
Never shot slugs so I'll be interested in seeing how you do with them. Just out of curiosity, what velocity are you getting with them now? What hammer spring adjustment is there in the Liberty? I assume you're maxed out there too?Upvote 0
Yes you have to shim the hammer spring on these.. Right now I have a very very slight preload on it.. So a bit more to max the spring out.. About 800 fps with the 15.5 NSA slugs.. I would like a bit more but accuracy is what counts..
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You can use this calculator I recently provided to AirgunNation members to find out exactly what you need to do to obtain your goals..
View attachment 1548298222_3881451895c4927eeb1ef53.78618675_PCP_Performance.ods
Any porting over 80-85% should be oblong as to allow pellet to load properly, meaning keep the width @ 80-85% max, 75%-80% being more safer, 80-85% requiring precision and may damage certain types of pellets upon loading.
-Matt
Any porting over 80-85% should be oblong as to allow pellet to load properly, meaning keep the width @ 80-85% max, 75%-80% being more safer, 80-85% requiring precision and may damage certain types of pellets upon loading.
-Matt
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