Tuning Help needed for FX Maverick and Extreme Spread

[dgwren]

FX Experts: I'm really enjoying my Maverick Sniper .22 after a couple of months of ownership. I'm experienced with PCPs in general, but this is my first FX. I'm generally getting excellent accuracy with JSB KO 25.4 .217 after some tweaking of the fine hammer spring tension. I'm running about 110 bar on the 2nd reg, 150 on 1st reg, and getting about 910 fps.

The problem that I'm running into is what I think is excessive ES, especially compared to shot strings that I've seen posted. My typical ES is 20-25 fps over 5 or 10 shots using the FX chrony attached to the barrel. It doesn't seem to matter if the bottle is at 250 bar or closer to 150 bar. I get occasional flyers that I can't explain, and I think the sudden 20 fps swings in velocity are contributing. I'm on the down slope of the velocity/pressure curve, but I've tried several different pressures with similar results.

Am I missing something, or is this a regulator issue?

I'm open to suggestions and guidance from those with more experience with FX airguns! 

 

[Mwerks]

I have the Maverick Sniper in .22 caliber and found a condition much like yours. FX originally said the plunger in the regulator need replaced, which I had done by the dealer, but I still had the same issue. I found the replenishment of the plenum was slow so I started timing my shots. At 12 seconds between shot the ES and SD went way down. If attempting to shoot relative to a good wind condition I shot faster and the ES and SD went up. At 30 yards the target didn't care much as the grouping was good but at 100 yards it did make a difference. Just try pacing your shots as a test to see if there is a change in your numbers.

 

[dgwren]

Thanks Mwerks! I have tried waiting longer between shots, and that did help. Like you, I see good accuracy at shorter ranges and more effect of velocity variation at 100+ yards. I'm wondering if my best groups (several in still conditions <=1 moa) were achieved with more time between shots. I will try to be more intentional about waiting a few extra seconds and see how consistent the velocity is. For target shooting, which is what I'm usually doing, it shouldn't be an issue.

 

[Rallyshark]

I switched to the Huma regs, and the refill time is pretty quick(2-3 seconds). Another thing to consider is how far below the plateau are you shooting? I noticed that with the FX regs, the gun didn't always replenish the plenum, if enough air wasn't used during the shot. I would take two shots, before the plenum would replenish sometimes. In other words, the factory regulators worked better when shooting near the max velocity of a given reg setting. The Humas seem to be a lot less picky about that.

The ammo you're using could be playing a part too. There's a chance that barrel would prefer something in the .218 variety? If you've tested .218 in that barrel already, then disregard this part... One more thing still, you could consider upping the speed a bit. 20 fps has less affect when you're shooting 970 fps than it does when you're shooting 900 fps. That's just some other stuff to consider at least.

 

[bunkeru2k]

I don't have much experience with FX or any of these PCP airguns, but I have a long history of dealing with balanced poppet valve paintball guns which these are all based off of. There are so many variables that can make that spread be higher. One easy one can be just the slightest variations in weight/size of the ammo. At 100 yards, a half grain off could make a big difference. The other part is that each gun has its own sweet spot. Even if they are all run with identical parts and run from the same batches, etc you can find that the sweet spot can vary a bit. Although I know my tune currently is not ideal by any means and it has room for improvement, I find certain numbers on the power wheel maintain a tighter spread than others. My ES on the pw4 setting right now is sitting at a pretty normal ES of 10 and average of 1005 fps. I do see more fluctuation when I am at pw7 and pw1. If you have a scale and a micrometer, I would sort a slew of those slugs and eliminate that as a variable and then check across the PW with those in various settings. If you see a couple spots on the PW that tighten up, then you know it is just a matter of finding that perfect tune.

 

[Khornet]

Not a Maverick owner, but with my .22 Impact tuned closer to the downslope end of the knee I found I got big ES when shooting fast and low ES (like as low as 4) when waiting 20 sec between shots. Because I wasn't happy with my accuracy (a problem which turned out to be unrelated to tuning) I wound up with 925 fps average with my reg at 95, which puts me at a little over 97% of my max velocity, with typical 10-shot ES of 7 which is below 1% of average velocity, with Sd 2.4. So I think Rallyshark is right: you may be too far down the knee, and a little more hammer could help. Or a little less regulator.

I'm shooting 23 gr H&N .218 slugs. I think even for 25 gr a reg of 110 might be more than you need to get 920-940 fps.

Also both my standard pellet liner and my Superior standard liner dislike .217 slugs, and both do well with .218. I can get good numbers with .217 but not good groups.

 

[dgwren]

Thanks for the continued suggestions! I think I’ll try more hammer. I don’t think I was getting good velocity numbers before, since I wasn’t waiting between shots in previous testing/shooting. 

 

[dan_house]

shoot a full tank over the chrony. 5 - 10 shot isnt enough data to be telling

If your spread doesnt get bigger over a full tank, then yer good (above suggestions might still be helpful)



IMO people dont collect enought data from the chrony to be as helpful as that data could be....

 

[dgwren]

Just I’d post an update. I’m still not excited by the ES I’m getting, but some of the comments reminded me that I have some 24.8 grain NSA slugs. Here is string where I shot the NSAs with at least 10 secs between shots:


Shot count: 10
Low: 895
Hi: 919
Avg: 907
Spread: 24
STD Dev: 7.7
909
916
907
907
898
919
902
905
914
895



BUT.....here’s a group at 100 yards with same settings:

 

[Rallyshark]

I think people get too bogged down in numbers sometimes. If it shoots good, that's all that really matters

 

[B]

shoot a full tank over the chrony. 5 - 10 shot isnt enough data to be telling

If your spread doesnt get bigger over a full tank, then yer good (above suggestions might still be helpful)



IMO people dont collect enought data from the chrony to be as helpful as that data could be....

What he said, but at the same time people go too crazy with the numbers, a gun with 20FPS ES spread can be very accurate.

B

 

[elh0102]

This may have no relevance, but I've done a lot of tuning work on my Royale 400 with Huma reg. I seem to get my most consistent velocities very near the maximum power for any given reg set point. Example, right now I'm shooting the JSB 18 at 898-902, and the ES of most strings is actually about that small. Velocity is max at around 910. I would have guessed my sweet spot would have been closer to 880, which was actually my goal. But at that speed, I see ES of 15, maybe more. My shooting is mostly under 50 yards, so frankly, either set up would be fine, I'm just tinkering. I'm too lazy to go through another series of disassembles to find the perfect reg/HST combination. And it shoots great. I haven't shot it down to see how it behaves as it falls off reg, maybe not great, but I don't need maximum shot count either.

 

[bigHUN]

I don't have the Maverick but the Impact MK2 PP.

I have a digital/Edmun gauge on the reg, left it there last time ( many months ago) I tuned for minimum spread.

You shall maybe try to mount a digital gauge on the second reg to see how it recovers after the shot. Maybe not your reg but your tune makes the ES.

 

[dgwren]

I should have mentioned that the NSA slugs are .218, and they seem to shoot more consistently in my Maverick than the JSB KOs. Of course, now NSA is out of the 24.8 gr slugs! I ordered a couple packs of the 27.5 grain .218 slugs to try.

I'm definitely going to work on getting closer to the velocity plateau. There seems to be a consensus that really close--like with 10 fps--of the plateau may be best for the AMP regs and consistent velocities. It is a little hard to get that close when the velocity varies. I guess people just crank out on their HS in tiny increments (which increases velocity on Mav) until they get the tightest spread and best harmonics (checked with groups)?

 

[Rallyshark]

I would honestly just let the targets tell you if the gun is right or not. I never stress over the ES much at all. I mean, sure I care if it's jumping all over the place, but 20 fps would rarely worry me. If the gun is grouping well and the POI is always consistent, then that ES don't mean much There isn't a full consensus on that plateau tuning. I run my Maverick with the power wheel on 6 a large majority of the time. As I mentioned before, that usually means 25-35 fps below the plateau with my settings. Actually, I will run it on 1 for house duty with lighter weight slugs, and it is still one ragged hole at 40 yards. What good is a power wheel, if we don't get to use it I'm going a little against the common grain here, but I have no interest whatsoever in seeing how low I can set my reg and get the speed I want. I prefer the gun shooting further below the plateau than close to it. It is quieter, and usually more efficient that way. It also gives a little headroom, when switching to heavier ammo. I usually tune my gun to where it is a solid 10-15 fps below the plateau at 7, but I try and tune it where the speed I want happens at 6. That's just my personal preference though.

Speaking of slugs, my Superior Heavy seems to prefer the .218 slugs as well. The bigger challenge is usually finding the speed they work best at in the gun.