Tuning :)

Jump to latest Follow Reply
Wow, two great questions! To answer the first one regarding the barrel liner o-rings...I always remove the o-rings because there is really no good way of securing them so they are in the same place each time. Accuracy can be defined by one word: Consistency. So either leave them off or support the liner a different way that will remain consistent. One way of supporting the liner inside the barrel tube is to wrap tape around the liner in several spots until it just fits snugly into the barrel tube. This way it is supported the same way each time you take it out and put it back in. You might want to test your own rifle by shooting some groups without anything on the liner, and then with supports of some kind on your liner to see if there is any difference in your rifle's accuracy.

As to the second question: When you over tighten the grub screw on the rear block that holds your barrel tube in place, it pinches the barrel liner inside and makes it hard or even impossible to rotate or remove the barrel liner. So when you are going to rotate the liner to each of the new positions to shoot test groups it is important to loosen that grub screw first. Then of course you must remember to tighten it after you rotate the barrel liner to each new position. It seems that most people tend to over tighten screws and especially that grub screw. I have had dozens of guys over the last few years contact me to ask why they can't remove or rotate their barrel liner to index it, and it is always because that grub screw has been over tightened with an Allen wrench. Maybe this is why the original Impacts had a thumbscrew rather than an Allen screw? 

One last thought to share...Once you get your liner indexed to the sweet spot that gives you the best accuracy, you can make a permanent registration mark so that you can remove it for cleaning and reinstall it to the exact same place each time. And each time you reinstall your liner it will shoot exactly the same way each time.
Click to expand...

That totally makes sense now. Thank you for explaining!
 
Upvote 0
...To answer the first one regarding the barrel liner o-rings......So either leave them off or support the liner a different way that will remain consistent.
Click to expand...

I replaced the liner original orings with harder NBR90 and secured with a Teflon tape.

But tinkering now taking out these hard orings and replace with very soft silicon sleeve bushings, to make the liner really "float".

Super soft silicon sheets, slice to let say 10mm width and wrap around the liner on tree places?
 
Upvote 0
Chuck, thanks for the great info on barrel indexing! I'm new to the "high end" world of air guns, just got an FX Impact Compact and love it.

I have been tuning it and think I am ready to do the indexing you describe. I have a question about the O rings on the barrel liner. I just added a Huma-air transfer port and pellet probe, when I was putting things back together the O rings on the barrel liner were impossible to position, I noticed you mentioned they could be left off, is this how you're setup or have you found another solution?

I will try to add a picture to this post showing what I did to finally get the O rings spaced, but I would rather leave them off if it doesn't make any difference. My barrel is just 500mm I used a piece of pipe hanger (holly iron, only made of plastic not metal) I cut a strip about 1/4 inch wide and 6 or 8 inches long then put a mark on it a few inches from the end. I could then use this between the barrel liner and the shroud to push the O ring into position using the mark I made as a reference to know how far in the O ring was. I could then know the O rings were both the same distance from each end of the barrel liner.

I have to assume that leaving the O rings off could lead to better accuracy same as a powder burner with a floated barrel. I'm very interested in your thoughts.
1598378156_12822846515f4550acde7d02.15311858.JPG



 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu