FX Impact Inconsistent Velocities

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I respectfully disagree on chasing down the velocity fluctuation by sorting pellets. As you noted, you are not sorting pellets in your other airguns and getting much more consistent velocity strings. I don't ever sort pellets other than to not use the ones that are obviously damaged and don't ever see strings that look like that...with one or two high velocity fliers. 

Assuming nothing is wrong with the regulator gauge you are really talking about the hammer/valve assembly. A few high ones suggest the valve is staying open a little longer. Could be a valve issue or a hammer drag/return issue. I'd look there first.
 
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Mrhosted, I haven't spent a lot of time with the 22 set up, actually only had it a few weeks.

Airgun-hobbyist, I took your recommendation and did a little pellet sorting this morning. I had 94 pellets (JSB re-designed) left in a tin and sorted those. The lightest being 24.9 (3) and the heaviest was 25.7 (1) The top three groups with the most pellets each was the 25.2 to 25.4 groups, the regulator setting on about 149 and the HS adjust on #3. Velocity wise they shook out like this.

24.9's 951 949 949

25.0's 930 947 928 928 951

25.2's 946 925 925 921 923

25.3's 914 922 924 923 949

25.4's 925 923 941 928 925

25.5's 925 944 924 921 917

25.6's 927 922 926 924

25.7 944

So, overall from the lightest to the heaviest it is possible to see a 20-25fps difference which was is pretty believable out of tin of pellets.....but almost every group although sorted still had those inconsistent singles.

So out of curiosity I thought I'd slow the gun down with just the valve adjust and shoot a few 18.1's ..939 945 946 940 948 946 953 949 948 940, much better!! Well since that worked out for the good on 18.1's I thought I try slowing down the RD's AGAIN ( tried it previously and didn't see the same results) with just the valve setting from the third line and closed it 1/4 turn. 887 888 892 893 907 895 889 887 891 913 890. Now I can live with this but was wanting to shoot the RD's a little faster. Probably plenty fast for my use anyway.

It looks like all this time it was just a tuning issue especially after going through the gun and not finding anything mechanically.

I knew my barrel was probably also getting fouled so I cleaned it and at my new setting the string still looked good. 912 913 915 948 909 910 912 906 904 910 908, except for one shot.

Speaking of fouling barrel. It seems like this 22 slug liner fouls really fast and badly even after I polished it. Using a string pull through I can always feel some really rough spot through the barrel. After a couple of pull throughs it still felt terrible so I used my Patch Worm. It really grabbed some lead as shown in the photos. Sorry only one photo transferred.

1580066336_3161266275e2de6203b0aa4.45788770_IMG_5608.jpg


Guys, I appreciate all the help

jking






 
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Hi 

Just got my FX impact mk2 power plenum it's not shooting well with variations over chrono of 25-30 fbs. 870-895 was last sting range using JSB 18.1 in .22. Shooting with reg at 100 bar and 180 bar from main chamber. Reg seems to move 10 bar between fills. Gun was shooting 2 mil dots high and seemed ok re-loaded and could not see where pellet hit. Turns out now shooting 6" high! Seems to shot low and high. Put my 20 year old unregulated PSP over chrono and got an 11 fbs spread and a nice group. Have not cleaned barrel of new gun ready to send it back. Any suggestions appreciated.
 
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What are you set at now? Back everything off. Especially the hammer spring screw if you adjusted it way in to open the valve at the higher reg pressures. And start from scratch. Valve adjuster on the fourth line. What velocity are you shooting for with the 18's? 

Just as a reference, mine will shoot the 18's at 930 with only a 70 bar setting. I have it tuned for 910 with the valve adjuster on the third line. Your pushing it to hard and its not balanced. With the reg creep, your speeds will be all over unless you bring it down.
 
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Thanks to both of you. 

Rj it’s set at 100 bar, power setting is at Max, not sure about the valve will check Saturday. Fbs is 870 to 895. Will try your set up 70 bar on reg, third line on valve, what’s your power adjuster at?

Looks like Lock-down for us this weekend at some point so should have plenty of time to try out different settings! Just hope I can fix without sending back.

Might clean the barrel too.

Thanks again guys will let you know results.
 
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Ok so shooting at around 900 fbs, with a variance of 17 fbs which is much better than the 25-29 I was getting before watching the Video. Slight movement on scope so took off and now it’s solid. Zero’d again as shooting high about 4” was 1/2” up and down. 160 bar in main bottle. Then I reload and it starts shooting 6” high each shot keeps going higher. So was not the scope.

tomorrow refilling to 200bar zero, wait 4 mins and see if shooting high if not the reload and if shoots high which I expect it will what do you think it is?

P.S have ruled out clipping.


 
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