Newbie here Shot string, spread and standard deviation.

Jump to latest Follow Reply
B

BrocStar

Member
Sep 4, 2021
94
2
California, United States
Hello all, 

So I received my gun from Utah air on Wednesday. I paid extra for them to tune my gun before shipping it out to tune the 34 grain JSB. Well my shots were all over the place so I purchased a chrony. Got it out today for the first time and was really disappointed what I found. Let me say what it arrived like, the tune that is. First reg 145, second 105, Macro 16, Micro 5 and valve was open to 4 lines showing. Shot a 25 string. Low was 891 high was 931 and average 910. Spread of 39 and standard deviation of 7.2. Did it again without touching anything this time 35 shots. Low 798, high 905 spread of 107 and STD Dev 39.5. I then proceeded to close that valve as I was using like 5 bar per shot. I closed it down to where only three lines are visible. My group was very tight , hole in hole mostly. New shot string of 16 shots, Low 858 high 888 and average of 878. Spread 30 and Std Dev. 8.

the reason I right this is I need help with my set up. Are my regs set up proper? as I lowered the valve my shot count increased. Like I said I am a newbie with this and tuning. Should I increase the second reg a little then lower the power wheels? I also want to know if this tune Utah sent me is complete crap as I did pay extra for it. I plan on calling them tomorrow and seeing why they would send the gun out like that. 

Thanks for the help 
 
/\ /\ /\ Agree with Jason,

Just give your new M3 a chance to settle in. I would not make any wild "tune adjustments" nor start "adjusting reg pressures" until you have a few tins of pellets through her. Doing so will just frustrate you. Keep a log of your shot strings at your current reg pressures along with any macro/micro adjustments you make. You will see a pattern form along with a consistency as the gun settles in. From there you can decide what adjustments will need to be made to shoot the way you prefer. Be patient and you will be rewarded.

Patrick
 
Upvote 0
IMHO, there's no way those numbers are 'break in' related. I've got a MK2 and MK3 and get annoyed if the spread goes over 12fps. Those tune settings seem out of whack to me.

I think your instincts are correct. Low second reg and too much hammer. I'd reset the hammer to midrange (macro 8, micro 3), bump up second reg to 120bar, and reopen the valve to 1.5 turns past the fourth line and start from there. Then crank the macro to 16 and see what you've got.

A little too fast, close the valve a bit. A lot too fast step down on the macro. Too slow add 5 or 10 bar to the reg. Winding the micro wheel up to 5 really shouldn't be necessary. The micro is intended for fine plus/minus speed adjustments.
 
Upvote 0
The difference in altitude and dealing with new regs could have an effect, but not this great. IMO, they blew any tuning job attempted. I'll never own anything with 2 regs, so I can't help you there. But generally, you have to play with hammer tension and reg set point to find the proper balance. In tuning a rifle with one reg, that point of balance is usually around 95-97% of the maximum velocity at a given reg set point. The rifle will be quieter and use less air when compared to a less efficient tune. Keep playing with it and you'll get it right. And yes, give them a call to express your disappointment, but I'd not be inclined to give it back for further work. As the old saying goes, “fool me once, shame on you, fool me twice, shame on me.” 
 
Upvote 0
Thanks you. I have about 4-5 tins through it. I did clean the barrel last night and it was filthy. I guess they dont do that when they send the gun from Utah after they tune it. I will continue to monitor it. I only lowered the valve to three bars to conserve air since my Air Venturi 4500 compressor took a crap and I shipped it off yesterday. After I closed the valve I was shooting the 34 grain at average 878 and accuracy was way better at 50 yrds. Going to try and go out again today.Will not touch regs until I have 1000 pellets through it. Can I ask what is a normal spread in FPS? 
 
Upvote 0
Hard to say what is "normal" in terms of ES with a properly regulated gun. In theory of course, it should be 0. Most of my rifles will shoot 10 shot strings of under 10 ES, but it varies. In practice, and for most uses, I've found that anything under 20 generally performs just fine. I recently shot a string in which the first 8 shots were the same, never had that happen before. 
 
Upvote 0
I'm pretty sure a reg differential of 20-25bar is enough. If you need to go above 125 on the second reg then bumping the first one to 150-160 should be fine.

1.5 turns past the fourth line on the valve is what FX says is wide open. After you have the speeds you're looking for you can close the valve 1/8-1/4 turn at a time to take off the top 10-20fps and improve eficiency. So try for a little faster than you actually want with the valve wide open.

Don't obsess about cleaning the barrel. A lot of guys say they never clean the barrel. With soft lead pellets, the theory is, each shot cleans the previous one and disturbing the layer of lead oxide (that black stuff) that forms in the barrel can actually hurt accuracy.
 
Upvote 0
Thank you. I have noticed my first reg keeps jumping between 145 to little past one 150 as the gun sits. Is this normal. Right now my gun is reading 150 on first, 105 on second. I think bumping the second to 120 is a good idea. Counter clockwise small adjustments. I will try that and try and shoot again today. Thank. you Not sure what speed I am looking for with the 34 grain. When I lowered the valve yesterday at the current reg settings I was shooting about 888 but my spread was still about 30. I would like to get that down to about 7-10.


 
Upvote 0
Well, 7 is optimistic, 10 is doable, and anything under 15-20 probably won't be noticeable without a chrony. Contrary to what I usually read here, my first reg creeps down to 145bar when the gun sits for a day or so. After the first shot it's back up to 155 and stays there till I let it sit for a day again. Maybe it's just the gauge. Take pressure recomendations with a grain of salt. Even the newer Wika gauges can vary 5-10bar or more, so performance should be your guide, not blind faith in the gauge reading.
 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu