Tuning Need a .30 Maverick Expert! +/- 30FPS swings with for no apparent reason! TONS of data inside!

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AirShootist

AirShootist

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May 12, 2021
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IL, United States
I am in need of a .30 cal Maverick Expert!

Goal: Shoot 44.5 hybrid slugs or 47.2 NSA slugs at 100fpe for coyote hunting

Equipment: .30 Maverick VP (600mm barrel) w/Huma V2 Transfer Port, Pin Probe, Huma 14.5g hammer weight, Huma extra power hammer spring.

PROBLEM: Gun can easily be made to shoot over 100fpe. I tune it at 150 bar for 100fpe and it will shoot several consistent 100fpe shots right at about 975 fps, then suddenly drop like 30fps. It does this with a variety of different hammer weights, stock/Huma springs, different spring settings, and different pressure settings that I’ve tried. It does this with both the hybrid slugs and the NSA slugs, so we can eliminate the ammo as being the cause.

Below is some data (taken w/47.2 NSA slugs) to show my testing. I always start with my hammer tensioning screw at fully out (6mm) from the hammer spring retainer, which is the max setting, and then I measure in turns IN. This way I always know how many turns I am at so if I back it out I won’t exceed the max (6mm out) setting. I will abbreviate my turns in on the hammer tensioning screw as “-1T” if I turned it in 1 turn, “+1T” if I backed it out 1 turn.

DATA:
145 bar, 13.05g Huma Hammer, Stock spring, hammer tensioner adjustment maxed out, PW7

Velocities: 707, 747….yikes, -.5T > 691, 691, -1T 668 (obviously too light of a hammer, adjusted HS back to 6mm)

150 bar, 13.25 FX hammer, Huma extra power spring, PW7

Velocities: 984, 970, 986, 985… -.5T > 981, 984, 958, 953… -.5T > 956, 956, 951, 986….

160 bar, same hammer & spring: 993, 990, 995, 967, 970… +.5T > 993, 995, 997, 958, 960 +.5T > 990, 972, 974….

-1T, 155 Bar > 986, 990, 967, 988, 958….

150 Bar > 981, 974, 984, 963, 958, 960… -1T 946, 951, 951, 960, 949… +.5T >981, 949, 946, 979, 981, 949…. +.5T > 981, 986, 963, 956…. +.5T > 953, 960… -.25T > 956, 988, 958, 984, 949… -.25T > 956….tried PW6 setting > 977, 979, 956, 977…. -2T (so -4T total now) > 930, 935, 932, 963, 965, 921… +.5T > 949, 944, 937, 944… +.25T > 974, 951, 977, 946…. +.25T > 951, 951, 970, 944… +.5T > 981…956… gave up

14.5g Huma Hammer, Huma spring, 150 bar, -4 turns, PW7

Velocities: 935, 916, 916, +.5T > 970, 946, 949, 979… +.5T > 956, 953, 981, 956… +.25T > 979, 953, 960… +.25T > 979, 981, 956, 974, 967, 949… +.25T > 958, 949, 951, -.25T > 977, 951, 942… +1T > 979, 956, 984, 967… +.5T > 984, 965, 960… -.75T > 977, 949… +1/8T > 970, 930

It was at this point I just gave up, frustrated as can be. 30+/- FPS swings are NOT OK for a rifle this expensive. My .22 Maverick works great and is constantly +/- like 5 FPS. While shooting the .30 I kept looking at the rear Wika gauge and it would reset to where I had it set after every shot…

What is going on with this .30 VP? Why can I absolutely not tune it to be at all consistent? Sometimes the shot string starts looking good and then just drops 30 FPS! I am looking for any and all suggestions to correct this. I’ve been told to remove my rear reg and clean/inspect it, but before doing that I wanted to get other opinions since it WAS returning to the set point after every shot.


PLEASE HAAAAAAALP!!!!
 
Why the constant adjustment? Unless I am reading this wrong sometimes you shoot just 2 shots others its 3, 5 or 6. If thats the case I would slow down and shoot more shots and let it settle at the new settings each time. Hard to narrow down something if its constantly getting tweaked. Are you shooting for accuracy at the same time? If so whats the off shot doing? Was that pellet damaged in some way that causes air to push past. Do you feel air blowing out of the bolt probe area during the shot indicating a bad oring? That could cause fps drops.
 
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AirShootist said:
I am in need of a .30 cal Maverick Expert!

Goal: Shoot 44.5 hybrid slugs or 47.2 NSA slugs at 100fpe for coyote hunting

Equipment: .30 Maverick VP (600mm barrel) w/Huma V2 Transfer Port, Pin Probe, Huma 14.5g hammer weight, Huma extra power hammer spring.

PROBLEM: Gun can easily be made to shoot over 100fpe. I tune it at 150 bar for 100fpe and it will shoot several consistent 100fpe shots right at about 975 fps, then suddenly drop like 30fps. It does this with a variety of different hammer weights, stock/Huma springs, different spring settings, and different pressure settings that I’ve tried. It does this with both the hybrid slugs and the NSA slugs, so we can eliminate the ammo as being the cause.

Below is some data (taken w/47.2 NSA slugs) to show my testing. I always start with my hammer tensioning screw at fully out (6mm) from the hammer spring retainer, which is the max setting, and then I measure in turns IN. This way I always know how many turns I am at so if I back it out I won’t exceed the max (6mm out) setting. I will abbreviate my turns in on the hammer tensioning screw as “-1T” if I turned it in 1 turn, “+1T” if I backed it out 1 turn.

DATA:
145 bar, 13.05g Huma Hammer, Stock spring, hammer tensioner adjustment maxed out, PW7

Velocities: 707, 747….yikes, -.5T > 691, 691, -1T 668 (obviously too light of a hammer, adjusted HS back to 6mm)

150 bar, 13.25 FX hammer, Huma extra power spring, PW7

Velocities: 984, 970, 986, 985… -.5T > 981, 984, 958, 953… -.5T > 956, 956, 951, 986….

160 bar, same hammer & spring: 993, 990, 995, 967, 970… +.5T > 993, 995, 997, 958, 960 +.5T > 990, 972, 974….

-1T, 155 Bar > 986, 990, 967, 988, 958….

150 Bar > 981, 974, 984, 963, 958, 960… -1T 946, 951, 951, 960, 949… +.5T >981, 949, 946, 979, 981, 949…. +.5T > 981, 986, 963, 956…. +.5T > 953, 960… -.25T > 956, 988, 958, 984, 949… -.25T > 956….tried PW6 setting > 977, 979, 956, 977…. -2T (so -4T total now) > 930, 935, 932, 963, 965, 921… +.5T > 949, 944, 937, 944… +.25T > 974, 951, 977, 946…. +.25T > 951, 951, 970, 944… +.5T > 981…956… gave up

14.5g Huma Hammer, Huma spring, 150 bar, -4 turns, PW7

Velocities: 935, 916, 916, +.5T > 970, 946, 949, 979… +.5T > 956, 953, 981, 956… +.25T > 979, 953, 960… +.25T > 979, 981, 956, 974, 967, 949… +.25T > 958, 949, 951, -.25T > 977, 951, 942… +1T > 979, 956, 984, 967… +.5T > 984, 965, 960… -.75T > 977, 949… +1/8T > 970, 930

It was at this point I just gave up, frustrated as can be. 30+/- FPS swings are NOT OK for a rifle this expensive. My .22 Maverick works great and is constantly +/- like 5 FPS. While shooting the .30 I kept looking at the rear Wika gauge and it would reset to where I had it set after every shot…

What is going on with this .30 VP? Why can I absolutely not tune it to be at all consistent? Sometimes the shot string starts looking good and then just drops 30 FPS! I am looking for any and all suggestions to correct this. I’ve been told to remove my rear reg and clean/inspect it, but before doing that I wanted to get other opinions since it WAS returning to the set point after every shot.


PLEASE HAAAAAAALP!!!!
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I had massive problems with my M3 being inconsistent while my wildcat mk3 was a breeze. What I found out was that it was the fx chronograph placement with the m3. The placement of the chronograph didn’t matter on the wildcat but unless I had it tied to the m3 barrel it would read wildly inaccurate and caused me tuning issues for a long time.
 
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LDP said:
Why the constant adjustment? Unless I am reading this wrong sometimes you shoot just 2 shots others its 3, 5 or 6. If thats the case I would slow down and shoot more shots and let it settle at the new settings each time. Hard to narrow down something if its constantly getting tweaked. Are you shooting for accuracy at the same time? If so whats the off shot doing? Was that pellet damaged in some way that causes air to push past. Do you feel air blowing out of the bolt probe area during the shot indicating a bad oring? That could cause fps drops.
Click to expand...
Thanks for your reply. Constant adjustment because when I see the same problem (30fps swing) I want to try something else. Shooting slower/more shots would be a good idea to let the regs settle, I suppose, but that is only when doing reg adjustments, which I am avoiding to try and keep it at 150. I am not shooting for accuracy, I was basically mag dumping into trash while getting velocity readings. I know the gun will 1 hole at 50 yards. Need the velocity to be consistent first. I am shooting 47.2gr NSA slugs not pellets. I do not feel air blowing out of the bolt at all.

Today I took apart both my regs, cleaned them, changed 1 oring (that I think I torched during disassembly), lubed everything with silicone grease, and I will retest. Going to set regs again at 180/150 unless someone wiser gives me a better idea. Actually I might start with the rear reg at 140 and work up from there.

Still looking for more feedback on this weird ass problem.

Cranky1 said:
Take the power wheel off( don’t lose the little ball bearing) and look for wear. My maverick was a very early model and it used a grub screw instead of the newer cap head screw. It ate into the power wheel causing velocities to bounce around.
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Power wheel is 100% fine.

Also, chrony is fine. My other 22 Maverick reads 995, 995, 996, 995, 994, 997, etc
 
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Update: Of course my compressor at the apartment went down yesterday (I'm so full of good luck....) so I can't test until Saturday at the other property.... BUT.... I am hoping what I just found might be the solution. The breach plug screw, with its coarse threads, did not allow the anaerobic sealant I had used to actually seal. I dry fired it a few times and could see the still liquid (after many months) sealant getting disturbed with each shot. So I teflon taped that sucka! Dry fired with a piece of plastic bag over the breech and didn't get any movement on it after that. My fingers are crossed that this little oversight is what was causing the 30fps swings. If you think about it, at about 1000fps, 30 fps is only like 3%. My thoughts are that this is plausible as the cause. Maybe this slugger will be fixed now that I lubed/cleaned my regs and teflon taped that screw up?!? (Fingers crossed)

1658444792684.png


I will see if I can get out and test thing thing this weekend. I will use what appeared to be the best tune so far (13.25g FX steel hammer weight, Huma heavy spring, 150/180 reg settings) and provide an update afterwards.

What are my chances that the blow-by from that little plug could have been causing erratic velocities? I'm definitely still open to other thoughts and ideas on this whole situation, but hopefully this solves it....
 
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AirShootist said:
Update: Of course my compressor at the apartment went down yesterday (I'm so full of good luck....) so I can't test until Saturday at the other property.... BUT.... I am hoping what I just found might be the solution. The breach plug screw, with its coarse threads, did not allow the anaerobic sealant I had used to actually seal. I dry fired it a few times and could see the still liquid (after many months) sealant getting disturbed with each shot. So I teflon taped that sucka! Dry fired with a piece of plastic bag over the breech and didn't get any movement on it after that. My fingers are crossed that this little oversight is what was causing the 30fps swings. If you think about it, at about 1000fps, 30 fps is only like 3%. My thoughts are that this is plausible as the cause. Maybe this slugger will be fixed now that I lubed/cleaned my regs and teflon taped that screw up?!? (Fingers crossed)

View attachment 277478

I will see if I can get out and test thing thing this weekend. I will use what appeared to be the best tune so far (13.25g FX steel hammer weight, Huma heavy spring, 150/180 reg settings) and provide an update afterwards.

What are my chances that the blow-by from that little plug could have been causing erratic velocities? I'm definitely still open to other thoughts and ideas on this whole situation, but hopefully this solves it....
Click to expand...
If air thats suppose to go to the projectile bleeds out around that screw I would think it could impact consistency the same as a bad breech oring would.
 
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Suppose to be getting my 25 back from FX. I was getting a similar set of symptoms before it broke! Hammer locked up solid. Tech called and said hammer had developed a " burr" on sear connection. My gun is 1 1/2 yr old. 1000's of shots. I mean 1000's !
The difference in hammer speed ( according to tech) would cause this. Rational person would agree.
Just a thought.
 
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douger said:
higher presures gotta take time to replenish that big power plenum between shots here a 30 cal im doing for a friends 30 cal 500mm with 44.75 jsb power 6 power 7 is 885 ish full mag dump at 50 yards laser beam
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I am waiting like 10 seconds between shots to be certain my plenum is full, and most the time I'm looking at the rear gauge to make sure I have the expected pressure.
 
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Keyman62421 said:
Suppose to be getting my 25 back from FX. I was getting a similar set of symptoms before it broke! Hammer locked up solid. Tech called and said hammer had developed a " burr" on sear connection. My gun is 1 1/2 yr old. 1000's of shots. I mean 1000's !
The difference in hammer speed ( according to tech) would cause this. Rational person would agree.
Just a thought.
Click to expand...
Yes thats another thing that I first thought of. If the hammer drags or catches during the shot cycle it could cause the same type of fps drop. I had a bsa that had some hammer drag due to slight wear.
 
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If your transfer port is the type with dual holes for pellet or slug get rid of that and replace it with a single transfer port style. No air will then slip thru the top, unused port and seep out that barrel lock retaining screw.

Your cocking block on the rod may slowly be slipping out of factory setting, which will misalign the transfer ports
 
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Bigragu said:
If your transfer port is the type with dual holes for pellet or slug get rid of that and replace it with a single transfer port style. No air will then slip thru the top, unused port and seep out that barrel lock retaining screw.

Your cocking block on the rod may slowly be slipping out of factory setting, which will misalign the transfer ports
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YES wildcat -maverick will do that and start to block off the tp- load a pellet pull the barrel see if the pellet is far enough into the barrel not blocking the tranfer prt also- easy check
 
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Bigragu said:
If your TP is a huma single port, and you have air seeping out that screw, one or both of your TP o rings are either compromised or the wrong thickness and it’s not sealing on the TP tunnel inside the block.
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Thanks for that. However I simply re-used my original FX transfer port orings on the Huma TP, including making sure the smaller diameter one (needed only in .30) was at the front. They should be fine but I'll check. I've also thoroughly checked the operation of the probe and that seems fine. I'll report back tomorrow after I do a little testing. I'm really hoping the sealing of that plug screw and the cleaning/lubing/rebuilding of my regs will have this sorted out.
 
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