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Wildcat MKII compact POI change

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Martinman

Martinman

Member
Mar 24, 2018
72
0
TN
 

Purchased a new WK compact and have had 2 poi shifts within a week. First time I noticed yesterday morning when shooting at starlings in my orchard. They were only 37 yards away. By my range card that I made after the first zeroing (My 2nd zero is at 50yds) it should’ve been 1 mil hold under. My poi was actually 1-1 1/2 mil low consistently. So I put up a shoot and C at 50 to check my zero. And sure enough it was hitting low at 50 yds. I thought ok, maybe I accidentally turned the turret when resetting zero. So I re zeroed the gun. 1 jagged hole at 50 yds. I was shooting small rotten apples off the trees at 70 and 80yds. Everything was well. This was yesterday afternoon. Came out this morning to shoot the starlings in the trees and at 37yds again and missed twice. Not even touching the bird. At 37yds the whole center cross hair is on the bird (@10x). So one landed at 50 and I took a shot thinking maybe I’m not holding correctly. Completely missed. My spin target was still up from yesterday so I checked and I’m hitting 4.5 mil low at 50yds!!!! I have no idea what’s going on. I haven’t made any adjustments to the gun or tinkered with anything other than the first cleaning of the barrel. Checked my pressure and I am sitting at 200 bar this morning. 

My scope is an Optisan EVX 5-20X50i

Any help would be appreciated. Sorry if this has been addressed somewhere else. I searched and couldn’t find anything on this.
 
Do you have a chrony? If you do. Check the FPS. Many of our HS nuts would rotate with pretty much every shot, usually out (less HS tension). Try adjusting the HS tension to get FPS AND shot to shot consistency (over the chrony) that you are happy with then 'lock' the adjuster nut in place. 

With the stock off, I could actually see the adjuster nut move with each shot. Once I found the spot I wanted it, I measured the depth off the back of the action and got creative with a way to hold it in place. People (including me) have used vibratite, the milder locktight and others, I ended up with a physical tensioner against the nut. 
 
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steppenwulf just summed up the post I just lost. Just remove the stock, stick the right size allen wrench in the HS adjuster and wiggle it, it won't take any effort the nut is loose fitting. If it's not loose... don't break it loose. Yet. 

From there (without a chrony) you are back to testing adjustments by shooting it and readjusting as needed. Chrony is a hundred bucks. Best 'tuning' tool there is unless you are willing to send it off for work.




 
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Just an example of what I could do with the chrony data. I haven't retested this since (18 months if my date is right) as nothing seems to have changed on target. .22 WC MKII after I found a happy place for the HS. Never touched the reg on this one. It's my .22 WC MKII.

1564334604_8874921065d3dda0ca95d79.84180273_WC .22.png

 
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what is the expected FPS change per 1/4 turn?
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Well some may disagree, but I have found them to be a little touchy. Mine (I've had them all and still have a .177 MKI and the .22 MKII) had a rather small range within they worked best. That may be related to the regulated pressure the hammer needs to overcome to open the valve. So in my experience, there is no good answer. I wouldn't go more than a 1/4 turn at a time, maybe a 1/2 turn. 
 
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Ok, just shot 3 mags through it. And the dang thing was back to zero. Not close, but dead on. The only thing I done was move the hammer spring adjuster not hardly a quarter turn to the right to see how loose it was and then marked it. 

The mark didn’t move through the 3 mags. Here’s what I’m thinking: it’s hot here in the south. When I’ve taken my gun out first thing in the morning it’s cool from being in the house. So the hammer spring tensioner could be looser until the metal gets hotter and expands some. That would still be too loose for it to do that. So I’m going to keep an eye on the mark. JCD when you noticed yours actually moving, was it winter?
 
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I just checked the nut and it’s no super loose or jiggling. I can turn the nut with a little pressure so it’s not locked in place either. I made a mark and I’m goin to put a couple of mags through it to see if it moves.

what is the expected FPS change per 1/4 turn?
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I have not found it to be a very linear relationship, guess it depends on how the spring loads up. I would almost discourage anyone from buying a PCP air rifle unless they own a chronograph, it's really that essential. You mentioned cleaning the barrel. I assume you did not remove the barrel, but cleaned with a pull-through. If shroud or moderator were removed, I would expect your POI to change. That was my experience with a Crown, although I realize this is a different design. 
 
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So I’m going to keep an eye on the mark. JCD when you noticed yours actually moving, was it winter?
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Prob winter but still, I could watch my adjuster mover with each shot, and the gun would have been the same temp (or close) as outside temps. My 'room' is actually part of my garage. If things change again, check your mark on that nut. A 1/4 turn may have been enough to do what you have described. You might still want to do something to hold that nut in place. Doesn't take much to hold it from moving, it's only under pressure when cocked (usually).

Glad to here it's back to zero.
 
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Ok, just shot 3 mags through it. And the dang thing was back to zero. Not close, but dead on. The only thing I done was move the hammer spring adjuster not hardly a quarter turn to the right to see how loose it was and then marked it. 

The mark didn’t move through the 3 mags. Here’s what I’m thinking: it’s hot here in the south. When I’ve taken my gun out first thing in the morning it’s cool from being in the house. So the hammer spring tensioner could be looser until the metal gets hotter and expands some. That would still be too loose for it to do that. So I’m going to keep an eye on the mark. JCD when you noticed yours actually moving, was it winter?
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i'm in the south too (sc). so its been really hot here. all i can say is that i currently have 4 fx guns that do not change poi as they warm up. of course your nuts are all tight (?). scope ok? use adjustable mounts? if not how much elevation did you have to click in?
 
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I don't believe temperature variations will result in the kind of POI change you experienced. I am in NC, very hot lately, and I have not noticed it. The only FX rifle I currently own is a Royale 400, which is so different from the Wildcat any comparisons would be meaningless. It's old style, a relative tank, and nothing seems to affect its POI. I had a Crown which, compared to the Royale, has a lot of features, including the barrel liner system. It shot well, but if I made any change to any part of the barrel/liner assembly, POI would shift. This would even occur from removing and reattaching the moderator. So, if I removed the moderator to clean the barrel with a pull through, I had to check POI, and it was usually off. My lesson learned with that rifle, don't touch anything between shooting sessions without checking zero. 
 
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Well you have got great advice so I can't add to that but I had a similar problem and turned out to be my scope was loose I took it off and replaced it back in place and then same thing again so what happened was my mtc viper connect scope would not hold zero at all so I sent it back got it replaced and that fixed my problem so check your zero on your scope and the way it's put on as well whatever scope you use it don't matter they all can loose zero. 
 
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Thanks for all of the feedback guys. 

To address some of your questions, It is a SFP scope and all shots when zeroed and shots taken when I noticed the POI change and shots taken after it corrected was at 10x. One of the first things I done was check the mounts and the scope. Everything was still tight. I did not change anything on the scope for it to be corrected, Meaning I did not remove it and replace it nor did I loosen any of the mounts. I only verified that it was still tight. 

OK, now the temperature. Remember nothing was changed on this gun except a little less than a quarter turn to the right on the hammer spring tensioner to see if it was loose. It wasn't wobbly loose, but it wasn't locked tight either. Thats the only thing that changed on the gun before it was hitting dead zero again. I shot allot yesterday. Went through 3 or 4 charges and it never lost zero again and the hammer spring did not move. The temperature statement is in reference to a hammer spring tensioner that is on the VERGE of being too loose. Not one that is tight or locked in place correctly. The tolerances on some of these parts are very small. I wasn't suggesting that temperature would affect a poi change this way on any PCP in hotter temperatures. My Streamline performs well in the summer and in the woods in the winter.

I have to travel for work this week so I will not get the opportunity to test this further. When I return I'm going to replicate yesterday morning and see what, if anything happens. The hammer spring tensioner is marked so I will know if it moves. 
 
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Found it!!! After shooting numerous times with no problems, I took the gun out of the case a couple of days ago and seen the front elevation lock down screw for the FX no limits mount fall out. Makes total sense. It must’ve loosened up and allowed the front mount to drop. Which explains why it was shooting low. The mount was down all the way when I re zeroed and that’s where it has been ever since. Not sure how it loosened, maybe I forgot to lock it down after adjusting it during my first zeroing. I’m just glad I know what was going on.


 
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