HST adjustment
Well, I did the delrin replacement for the brass piece a couple weeks ago. I also did the o-ring mod at the same time. Anyway, I counted the revolutions when I removed the HST adjuster. I thought I put it back right but it seems the head is deeper into the action than before – not sure. This is on a 22 caliber. Well, yesterday I had the opportunity to chrony the gun. When I got the gun, Tony sent chrony results that averaged about 930 with 18 gr jsb. We further adjusted the gun to get it back to 930. Now the head of the HST is pretty far into the action. Is there a possibility that it is screwed in too far but gives the same fps as a looser adjustment? Whereby I’m simply loosing too much air? How far in do others have theirs on a 22? Flush, 1/8 inch, 1/4 inch, 1/2 inch?
How should this initially be adjusted? Should it be simply screwed in until flush with the action, chronied to see where it is and then make say 1/2 turns until it is back up to 900 plus?
All Replies
I think something is indeed messed up here. I don’t recall you saying you adjusted the regulator. So, I’m assuming that is still stock and probably not particularly likely to have gone bad.
You did however do a delrin bushing mod. That and your hammer spring is where I suspect is the problem. If the hammer spring isn’t square on both ends, it can push the delrin bushing off axis and cause some interesting binding effects. The bushing can bind on the hammer or it can push the hammer slightly off center as the hammer moves into its barrel. That axial offset will bind the hammer and make for weird speed variations. I would do the following.
1. Examine your hammer spring. Stand it on end on a flat surface. Is it perpendicular on both ends? If not grind it flat. Is perpendicular
2. Polish the ends of the hammer spring so non of the wire ends are sharp. You want the wire ends (and spring ends for that matter) smooth so it won’t bind on the delrin bushing or HS adjuster. Wow, looked like craters on both ends – VERY rough. Polished both ends with emery cloth and then crocus cloth. Very smooth and shiny now.
3. Check that the delrin bushing moves freely on the hammer but isn’t too loose. It should slide without resistance but not wobble off axis. Its forward face should be perpendicular and strike the breach block without causing the hammer to deflect off axis. It should not travel into the hammer barrel with the hammer. Slides very well and seems to fit correctly.
4. Look at the surface of your hammer body. Are there witness marks showing areas of extra wear due to rubbing against the barrel. If so, then definitely suspect binding. No indication of binding.
5. Clean the hammer barrel, hammer, and spring thoroughly. Then use a very light coat of DRY lube to lube the barrel and hammer. Cleaned everything thoroughly. Even polished the hammer. Looks better than a new penny. The only DRY lube I had was powder graphite. I used a little, moved the hammer around and blew out any excess – if there was any. Just used about 4 pinheads of graphite total.
6. When you reinstall the hammer, bushing and rubber grommet, make certain the grommet does not bind on anything. (It may shift forward after a lot of shots)
Personally, I switched from the rubber grommet to a foam ear plug that has a hole punched in it. Appears to not be any binding. I don’t have any foam ear plugs. I do wonder about the compressed spring under the grommet and how fast and consistent it stretches back out when the gun is fired. I doubt that has any effect but who knows.
I think doing the above is likely to avoid the weird velocity changes you are experiencing. My bet is on erratic hammer function creating medium term velocity changes that swamp out regulator changes we are trying to detect.
Unless the weather cooperates tomorrow, it will be after Christmas before I can do any Chrony work.
Yes, I have not messed with the regulator. Don’t want to dig that far into the gun. Although if it is close to 160, I’d like to have it lowered.
I’ll check the hammer spring, etc and see what I find.
I’ll keep you updated.
EDIT: What DRY lube do you recommend?
Benji,
I think something is indeed messed up here. I don’t recall you saying you adjusted the regulator. So, I’m assuming that is still stock and probably not particularly likely to have gone bad.
You did however do a delrin bushing mod. That and your hammer spring is where I suspect is the problem. If the hammer spring isn’t square on both ends, it can push the delrin bushing off axis and cause some interesting binding effects. The bushing can bind on the hammer or it can push the hammer slightly off center as the hammer moves into its barrel. That axial offset will bind the hammer and make for weird speed variations. I would do the following.
1. Examine your hammer spring. Stand it on end on a flat surface. Is it perpendicular on both ends? If not grind it flat.
2. Polish the ends of the hammer spring so non of the wire ends are sharp. You want the wire ends (and spring ends for that matter) smooth so it won’t bind on the delrin bushing or HS adjuster.
3. Check that the delrin bushing moves freely on the hammer but isn’t too loose. It should slide without resistance but not wobble off axis. Its forward face should be perpendicular and strike the breach block without causing the hammer to deflect off axis. It should not travel into the hammer barrel with the hammer.
4. Look at the surface of your hammer body. Are there witness marks showing areas of extra wear due to rubbing against the barrel. If so, then definitely suspect binding.
5. Clean the hammer barrel, hammer, and spring thoroughly. Then use a very light coat of DRY lube to lube the barrel and hammer.
6. When you reinstall the hammer, bushing and rubber grommet, make certain the grommet does not bind on anything. (It may shift forward after a lot of shots)
Personally, I switched from the rubber grommet to a foam ear plug that has a hole punched in it.
I think doing the above is likely to avoid the weird velocity changes you are experiencing. My bet is on erratic hammer function creating medium term velocity changes that swamp out regulator changes we are trying to detect.
Yep, that is the bad news. It was at 200 bar after shot 33. According to gun gauge, it was filled to 260 bar for that string even though my Tiger tank gauge said 250.
It is supposed to storm tomorrow, so it may be after Christmas before I can do any further testing.
That latest one looks to me like you are “below the knee” with the climb off regulator starting about #30.
What mBar was that at?
That is some fairly erratic behavior. I suspect something else is awry with the shot strings.
There are two things that come to mind.
1. Did you change pellet tins during the shot string? No
2. What condition is the barrel o-ring. Has it be replaced or lubed? I assume OK as I do not have blowback that I’ve read about
3. Hammer binding? Is a rubber grommet shifted or catching on the cocking spring?\ I’ll have to check. I did do the mod
4. Hammer spring ends have any sharp areas that could be binding?Didn’t notice any when I did the mod but didn’t really know to look
5. Is the chrony reading consistently for another gun? Not that it necessarily makes a difference but the chrony is brand new – have had it a couple weeks. I’ll have to test with another gun but see below.
Any of these can cause erratic velocity changes and make the shot string quite confusing.
I would rule all those out and then retry getting a shot string and see if the data gets cleaner.
Here is a 33 shot string before quitting today after setting the HST for 915 fps.
Min 33 913
Max 33 922
Spread 9
SD 2.199
1 916
2 918
3 917
4 922
5 915
6 919
7 922
8 918
9 915
10 915
11 917
12 918
13 919
14 918
15 919
16 919
17 918
18 917
19 915
20 915
21 917
22 918
23 916
24 913
25 915
26 915
27 914
28 914
29 916
30 917
31 917
32 920
33 920
and the shots indicating it was beginning to climb
34 924
35 927
36 627
37 931
Looked at your second string data and your comments again.
That is some fairly erratic behavior. I suspect something else is awry with the shot strings.
There are two things that come to mind.
1. Did you change pellet tins during the shot string?
2. What condition is the barrel o-ring. Has it be replaced or lubed?
3. Hammer binding? Is a rubber grommet shifted or catching on the cocking spring?\
4. Hammer spring ends have any sharp areas that could be binding?
5. Is the chrony reading consistently for another gun?
Any of these can cause erratic velocity changes and make the shot string quite confusing.
I would rule all those out and then retry getting a shot string and see if the data gets cleaner.
I was typing while you guys were posting.
Well, I was more interested in determining the stability in fps and regulator drop off pressure than POI changes. So I was just shooting at a tree instead of an actual target.
But the first string when fps was set about 930 indicated the regulator was set about 160 and came off about 43 shots. When I turned the fps down to about 900, that changed to about 180 but the shift occurred at 42 shots. I thought I would get more shots at 900 by using less air and the regulator should still drop off at about 160 but that didn’t happen.
I did the tests again today and leaving the HST set to the 900, I have a graph that shows it came off the regulator at about 43 shots and about 150 bar, and another string of 55 shots and coming off at 160 bar. Wanting to try to get this to “On the Knee” and have a flat then drop-off without any rise or downward overall slope, I figured I’d try an HST setting of about 915. That gave me 33 shots and appears to have come off the regulator at 200 bar – at least that is when the graph takes an upward momentum.
I thought that regardless of the HST setting, the gun would come off the regulator at the same bar across multiple strings. In my case it doesn’t appear to be the case.
Do I have a bad regulator? Is it simply just set too high? Is there something else I should try?
Didn’t see much need to chime in seeing as you all seem to have it figured out.
HST is set “below the knee.” Adjust to slightly higher FPS to balance with the current regulator setting like Lurker said.
benj,
I’m new at this regulator stuff so don’t take my word for it but:
The first graph looks like a gradual slope that is not being regulated so I think that indicates the HST is somehow over powering or under powering the reg.
You turned the HST back out and got slower fps and fairly steady BUT I think ithe HST Is now to low and choking off the reg.
It appears well regulated until the tank pressure is low enough to allow the HST to open the valve adequately so the results is a jump up tin fps to where the reg is actually working.
IMO if you Increase the HST a little to get an average of 912-917 fps you will have the HST and REG balanced. The graph then should show less of a slope than your first graph with the sharpe drop off 5 or so shots after it goes off reg.
Where did guykuo go just when we need him ❓ He wouldn’t be busy with the Christmas holiday would he ❓
Smack with 2grs more power
is it shooting OK? just curious how much it shifts POI if at all at 160.
Finally got around to doing this. Looks like my reg is set around 160 bar.
Here is the shot string 1 from 250 bar and HST set at about 930. Appears to be “above the knee”.
# FPS BAR
1 933 250
3 930
4 937
5 934
6 928
7 932
8 933
9 931
10 932
11 933 220
12 929
13 932
14 933
15 929
16 928
17 927
18 931
19 933
20 931
21 928
22 930 200
23 933
24 930
25 931
26 930
27 931
28 926
29 931
30 931
31 927
32 928
33 930 180
34 929
35 932
36 928
37 929
38 927
39 926
40 925
41 927
42 927
43 924
44 920 160
45 918
46 915
47 913
48 910
49 907
50 910
51 901
52 897
53 895
54 888
55 880 140
56 877
57 867
58 862
59 862
60 855
I adjusted the HST down to 900 fps and shot another 570 pellets. I’m above 1500 through the gun. Probably closer to 1800. I don’t know what happened with my Bar readings from the gun but according to the chart from this data it appears the reg is set to about 180 based on the rise in fps (String 2). Now below the knee.
# FPS BAR
1 Error2 250
2 904
3 905
4 908
5 907
6 901
7 908
8 903
9 901
10 904
11 Error2 220
12 Error2
13 Error2
14 Error2
15 Error2
16 Error2
17 904
18 900
19 904
20 901
21 905
22 897 200
23 902
24 903
25 902
26 906
27 905
28 905
29 903
30 899
31 903
32 901
33 898 190
34 903
35 905
36 903
37 898
38 902
39 904
40 902
41 900
42 901
43 904
44 911 180
45 914
46 914
47 912
48 918
49 909
50 913
51 910
52 913
53 915
54 910
55 908 160
56 909
57 910
58 912
59 908
60 913
61 912
62 910
63 913
64 907
65 913
66 Error2 140
67 Error2
68 904
69 902
70 901
71 901
72 897
73 892
74 891
75 887
76 880
77 877 110
78 867
79 867
80 856 102
So where do I go from here?
Good explanation guykuo :thumb:
I was looking at my strings wrong. I was counting a couple higher than the trend as going off REG. Even those weren’t above the strings starting velocities.
Comparing the 3 tpyes of curves sheds new light on how a REG really works.
I had reset my REG so low that the HST worked in reverse :butkick:
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this is what the compromise is, you cant have best shotcount AND consistency. it is a tradeoff.
what you need to do is to decide what is the lowest speed acceptable for you to run at, then set the regulator and hammer for that.
if the reg is set too high, you have too much air unused just sitting in the cylinder (wasted). also if your reg is set too low, that is also not good for efficiency. to me it seems your hammer spring tension is OK because the gun can make 930 but only at certain low reg pressure. you need to lower the reg to even it out.
the shotcount is poor (per you) so to me it sounds like we don’t want to turn the hammer spring more in.
so this is telling me the reg is the issue so need to be adjusted. take it out, measure it so you can reverse if needed. turn the brass bit on it so the total length is shorter by by 0.25mm. then chrony play with the hammer again and see what you get.
edit: do not go by other peoples published regulator length. mine 90bar outputting one had the same length than others at 120 you see