Impact M3 Accuracy Question

The JSB 18.13 look very promising. I would try to fine tune the rifle with them at 840-920 fps. 

I would use the instructions in the following link as a guide:

https://www.airgunnation.com/topic/how-to-do-a-basic-regulated-pcp-tune-the-95-tune-plus-m3-tuning-simplified/#post-1242157

Pull the liner and clean it. Removing the liner and cleaning is also an opportunity to make sure nothing is lose in the barrel system. 600-700 rounds on a new barrel puts you in the zone where you may start to see degraded accuracy. You might get the cleaning done by just pulling patches through with CLP/Ballistol/etc., but JB bore paste will pull out any lead and lightly polish at the same time. I've never done the extreme 200 pass polishing you see on youtube. I do 10-15 passes with JB rubbed into a few patches. Pull patches forward OUT of the nuzzle, and do not pull patches INTO the muzzle. If you pull patches INTO the muzzle you will chamfer the crown and degrade accuracy. Initial cleaning/polishing with JB bore paste is probably the most helpful. I don't do it as much after the initial job.

People with really high round counts seem to say that barrels need less cleaning as time goes on.

Also, check the tune out like is recommended above. The factory tune may have been borderline, something may have settled or shifted during break-in, etc. You bought that chronograph right?

If you have any wind ,you can forget having good groups unless you have a lot of experience doping wind.

The slightest puff of wind will move a pellet off the group.

I use a couple of windflags at 50 yards and beyond,takes a lot to shoot well in the wind.

Thank you sir. I must have been typing when you were providing the answer. You mentioned the the ProChrono DLX previously right? Also would you go with JB Bore Bright or Bore cleaning compound?

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Yes to the ProChrono DLX. I've only used the regular JB bore cleaning compound on a very tight fitting patch. Its supposed to be around 1000 grit, and I am not sure going any higher is necessary (which would be Bore Bright). I like to keep it simple, and there is debate on the optimum level of polishing. The bore cleaning compound seems to be right in the middle.

the 14gr pellets will drift more in the wind also, plus those pellets are terrible dirty clean the barrel really good go shoot

Thanks. I am still pretty new to all of this and figured I would put off the chrono for a bit after the M3 and Hill Compressor in one week but guess Ill just bite the bullet. 

That being said, the Crosman 14.3 were what was shooting lights out until all of the sudden. It is a little windy out right now so maybe that is affecting more than I thought. Any chance the barrel needs a cleaning after that many rounds?

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Texas ; 21 pellets in 4 holes is pretty amazing, spending the money for the M3 and the Hill is quite an Impact on the wallet but buying a chronograph will be necessary to properly tune the gun, and in this case reveal if you changed the tune while adjusting the valve. I would be inclined to say the windy conditions is the major contributing factor to your perceived loss of accuracy . 

My manual references two possible valve adjuster bodies - one with 4 lines and one with 6. Both of mine have 4 lines. For the 4 line body, 'full out' is listed as 1.5 turns OUT from the 4th line. I recommend taking a silver sharpie and marking one of the grooves on valve adjuster knob so you can see that the knob hasn't moved. Same thing on the micro adjuster wheel, but I'd wait until you get a tune dialed in to do that. Both of these can get bumped, and both it is hard to tell where they are set. Micro adjuster has the marks, but there are about 10 clicks between each line so lot of un-referenced space there.



With regard to the 1st reg behavior, what is your 2nd reg set at? When I was experimenting with reg delta, somewhere around 25bar difference the first reg started acting weird. It definitely likes to be 50bar higher than the 2nd reg. You should be able to hear the plenum refilling after each shot with your ear next to it, and you should hear it for about 2 to 3 seconds if everything is working right. As long as the plenum is filling consistently, I really would try to avoid messing with or diagnosing the first reg until after you have the gun tuned and shooting well. One thing at a time. First reg can be a bit of a rabbit hole and really doesn't affect how the gun shoots, only how fast the plenum fills.



You are spot on about the tripod. Tripod is great for hunting and shooting over the chronograph, but not as stable as a bench. Even on a bench, I find my impacts moderately hold sensitive (higher power = worse), especially with regard to cheek pressure. It is a good idea to try and hold them exactly the same when shooting for groups.

That is quite the improvement, TDK is right on especially with the check contact I find I can get lateral dispersion if I have t to much pressure on the stock. 

I am only getting about 3/4 a turn past the fourth line. After sitting overnight 1st reg is 160 and 2nd reg is 95. I just shot it and 1st reg now reads 146 and second 90. I did hear the plenum fill but had to physically have my ear on the plenum to hear it.

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On my .22 the valve knob hits the shroud about 1 turn past 4th line (known 'issue' among 500mm and 600mm shouds). You are open as you can get it, and likely still above the threshold where preload would start having an effect. I wouldn't worry about it.

Regs sound fairly normal. The first reg is not a precise design - it creeps more and setpoint can also shift over time, usually higher. 5 bar of overnight creep on your second reg also sounds fairly normal. If you want to try and improve that down the road you can polish the piston face and opposite seat on the adjustment screw. My creep went to near zero after that. All that said, none of this should be stopping you from getting a good tune and shooting great groups.

Its possible what is happening with the first reg, is that your current tune is not using enough air to trigger a refresh of the 1st reg each shot. As long as the second reg is refilling, and the first reg does refill at some point before it gets to your second reg pressure, should not affect tune or accuracy. A 95% tune on my 600mm .22 (18.1gr at 890) ended up around 85bar so you are in the ballpark. Its important to note that even the Wika gauges are not super accurate. I had one that was 10bar off that FX replaced and the replacement is 3-5bar off as compared to digital Sekhmet. It doesn't really matter if you are only using it as a reference on your own gun, but you can see how you'd run into problems trying to copy someone else's tune directly.

Edit: re-read your statement and reconsidered the scenario. After sitting overnight, the first 1-4 shots on an Impact will be lower velocity. There is an oring or two sealing the valve system that takes a set and needs a few shots to loosen up. Along with this, I will notice the 2nd reg may not refill on the very first shot. Usually everything starts moving by shot 2 or 3. What you describe could very well just be this.