Question on AT44-10 parts gap

[Redrum4fun]

So I like many have been after the ability to shoot the JSB 18.13 through this rifle in a manner that doesnt resemble 12GA splatter so I tookl the rifle apart to remove the spacer between the Spring an Hammer to see if I get any nearer to 800FPS. Otherwise this rifle just loves the H&N Baracuda Match .22 Cal, 21.14 Grains, Round Nose, 5.53 mm. To bad they only come in 200ct amounts at about 5 cents a shot

In the process of putting her back together I notice there is a lot of slop in OD/ID of the pictured parts. My question is Does this matter in the slightest? Im pretty certain I could use Teflon tape to remove this gap without fear of it getting into my transfer port. Obviously I don't want to add anything that I don't have to so I posted up here.  Thanks for any input on the picture.

[colorider]

I would say that gap isn't important as long as you have a seal between the tank valve and that part.  Best way to increase or decrease the velocity is to adjust the hammer spring 

[Redrum4fun]

Thanks yes.. but the spring has limited adjustability on the AT44-10.  Other threads talk about this method and jbwelding valve ports.. which may be the next step.
Thanks

[Redrum4fun]

Well it's time to put her back together and see what if any FPS reduction I get without the spacer between the hammer and spring. Might as well see about trying to remove that gap. Cant hurt as long as I keep it clean and free of the port.

[Redrum4fun]

HOLY SMOKES !!! Removed the spacer between the spring and hammer on the rifle. Went to shoot through the chrony and ..lol.. 400FPS

Just came back inside to measure the spacer so I can go get some washers to stack. I find it hard to believe that nobody has mentioned this type of result that I have seen anywhere.
900 FPS down to 390-400 FPS... I dont know what to say.

[colorider]

That's a big change.  Good job.

[Redrum4fun]

Not what I had expected. So I went out to the homedepot and bought some stainless #6x32 nuts that measure .11 thick and filed the corners just enough to lay it flat in the ID of the hammer. The original spacer was .16 so I will see what happens here shortly.

[Redrum4fun]

OK So I shot 2 clips through the crony. Oddly enough the string climbed from 805 to 850 through 20 shots. I think Im on to something here but need to do a couple things to wrap my head around it.
First off I might go ahead and remove the bottle brush i crammed into the air cylinder and then I thin Im going to take the spacer down to like a .08 and see where I stand. My only goal is to be able to shoot the 18.13g JSB in a respectable group at 50-60 yards and decrease the group on the 21g H&N rounds. I think Im close to that happening here.

[Redrum4fun]

So I have now began using Aluminum rod used for arrows and a pipe cutter for a better way to dial in the thickness of the spacer. Going for a .075 this go round

[Redrum4fun]

So I have now began using Aluminum rod used for arrows and a pipe cutter for a better way to dial in the thickness of the spacer. Going for a .075 this go round

That is a winner. Shooting 810-795 over 20 shots. Will have to wait for Sunday to try and check a full string and how she is grouping but the 18.13g should do well at that speed all the way to 50 and 60 yards and the 21g even tighter

Maybe my wife wont notice me setting up a target in the back yard tomorrow while I'm supposed to be smoking the meat..

[Rallyshark]

I've had that result from removing the spacer before, but I didn't think anyone was interested in shooting 400fps,lol!  It makes perfect sense that it would do that, so don't worry.  When the spring is at minimum AND you remove the spacer you essentially make the hammer spring have zero preload.  It is right on the edge with the spacer in place, remove it, and you you will get a big decrease.  I remove the spacer on all my Hatsans and replace the hammer spring with a slightly longer one.  That gives me a lot more tuning flexibility

Now, about the space you were concerned about with the "cylinder carrier" as Hatsan calls it.  Don't worry about that at all.  As long as it is secure, the space there doesn't matter a bit

I don't know that getting your velocity lower is going to help your grouping with the JSBs.  Some guns just don't like them, and there's no way around it.  None of my Hatsans have ever liked the JSB 18 grainers, which is why I shoot mostly H&N Barracuda Match(5.51 seems to work best in my gun).  Back before Crosman changed their 14.3 grain domes, they were my go to plinking pellets and were very accurate(and cheap).  Sometime in the last year, they changed their process, and now they don't shoot worth a poo in my guns   I've measured 2 different tins lately, and the head sizes were all over the place.

[LDP]

I had to do some heavy polishing in my at-44 to get the jsb pellets to shoot good. My hatsan looked horrible at the lead and TP. Not sure what they cut the lead with but it must have been a coarse rock JSB are very soft pellets and they were getting shredded by the very rough lead and burrs at the TP. After the polish job it shot JSB the best.

[Redrum4fun]

So here it goes.. very strange results.. not what I had expected at all. Let me first say that m rifle must not have had a full charge when i ran it and got the 800ish FPS results on Friday. I expected a whole string off 800ish. As you can see from the following string I dont reach that FPS until nearly my 50th shot.

First shot on this string didnt register.
Created: 09-17-2017 11:42:29 AM
Description: .075 spacer 18.13jsb
Notes 1: 2900 to 600 PSI
Notes 2:
Distance to Chrono (FT): 3.00
Ballistic Coefficient: 0.031
Bullet Weight (gr): 18.130
Altitude (FT): 645.0
Temp: 61 °F
BP: 28.30 inHG
Shots
#     FPS        FT-LBS     PF
89    610        14.98      11.06     
88    637        16.34      11.55     
87    649        16.96      11.77     
86    654        17.22      11.86     
85    693        19.34      12.56     
84    681        18.67      12.35     
83    702        19.84      12.73     
82    715        20.58      12.96     
81    721        20.93      13.07     
80    730        21.46      13.23     
79    733        21.63      13.29     
78    742        22.17      13.45     
77    749        22.59      13.58     
76    752        22.77      13.63     
75    757        23.07      13.72     
74    766        23.62      13.89     
73    770        23.87      13.96     
72    777        24.31      14.09     
71    778        24.37      14.11     
70    789        25.06      14.30     
69    790        25.13      14.32     
68    795        25.45      14.41     
67    804        26.03      14.58     
66    801        25.83      14.52     
65    802        25.90      14.54     
64    806        26.16      14.61     
63    811        26.48      14.70     
62    826        27.47      14.98     
61    810        26.42      14.69     
60    816        26.81      14.79     
59    815        26.74      14.78     
58    813        26.61      14.74     
57    809        26.35      14.67     
56    809        26.35      14.67     
55    806        26.16      14.61     
54    810        26.42      14.69     
53    808        26.29      14.65     
52    805        26.09      14.59     
51    800        25.77      14.50     
50    795        25.45      14.41     
49    796        25.51      14.43     
48    786        24.87      14.25     
47    790        25.13      14.32     
46    786        24.87      14.25     
45    775        24.18      14.05     
44    774        24.12      14.03     
43    776        24.25      14.07     
42    778        24.37      14.11     
41    768        23.75      13.92     
40    766        23.62      13.89     
39    769        23.81      13.94     
38    764        23.50      13.85     
37    758        23.13      13.74     
36    755        22.95      13.69     
35    750        22.65      13.60     
34    751        22.71      13.62     
33    741        22.11      13.43     
32    738        21.93      13.38     
31    731        21.52      13.25     
30    719        20.81      13.04     
29    727        21.28      13.18     
28    713        20.47      12.93     
27    715        20.58      12.96     
26    713        20.47      12.93     
25    703        19.90      12.75     
24    710        20.30      12.87     
23    701        19.79      12.71     
22    703        19.90      12.75     
21    677        18.45      12.27     
20    690        19.17      12.51     
19    690        19.17      12.51     
18    689        19.11      12.49     
17    682        18.73      12.36     
16    676        18.40      12.26     
15    669        18.02      12.13     
14    673        18.24      12.20     
13    670        18.07      12.15     
12    671        18.13      12.17     
11    660        17.54      11.97     
10    665        17.81      12.06     
9     654        17.22      11.86     
8     650        17.01      11.78     
7     639        16.44      11.59     
6     653        17.17      11.84     
5     641        16.54      11.62     
4     639        16.44      11.59     
3     639        16.44      11.59     
2     632        16.08      11.46     
1     630        15.98      11.42     
Average: 734.62
StdDev: 59.36
Min: 610
Max: 826
Spread: 216
True MV: 742.73
Shots/sec: 0.07
Group Size (IN): 0.00

So I know this picture isnt pretty but 90 shots at 30 yarads did this and before any chnges I would have had a 12" diameter of shotgun splatter So I post this only to suggest there my be something to this

[Redrum4fun]

So i'm thinking that if I can find a way to shoot the PSI range of #30 to #80 and see what that looks like on paper I may have what Im looking for. I didnt have any of the H&N 21g rounds to test but did shoot some 19 grain H&N snipers in tight groups. I expect the 21g will still be my better round with the JSB 18.13 being a pretty good plinker out to 40 yards.

I may increase the spacer from .075 to maybe .09 and see what happens. I didnt expect such a long gradual string..

Am I wasting my time with the whole spacer thing? I can always go back to stock and plug some valve ports like suggested but am very excited with the amount of shots and may tinker with it longer.

Thank you guys for your comments, I always appreciate the input.

In the end this rifle is for my two sons to punch paper and rattle metal drop targets.. So my Priorities in order Group, Shots per fill, and way at the end iS FPE

[Rallyshark]

You can either do a lower fill, or increase the hammer.  It is that simple   It is obvious that you have too little hammer spring.

[Redrum4fun]

Thanks Rallyshark. I will first play with the fill and see what I get and then look to replace the spacer with one a little bigger. After that maybe plug some cylinder valve holes and see the effects. Maybe take a combo of 2 things to get a longer lower flatter FPS.

[Redrum4fun]

Thought I would share a quick pic of the new spacer.. I just cant wait to get this thing sorted.

[colorider]

Skip the spacer fiddling and start using the hammer spring adjustments.   Much easier. 

[Redrum4fun]

Skip the spacer fiddling and start using the hammer spring adjustments.   Much easier.

Last time you suggested that I had explained this particular rifle has very little adjustment in the hammer spring. Before any tampering I was able to barely get any reduction.. maybe to 860ish

[Redrum4fun]

Great so now I'm happy with the results. Not perfect but a great plinker for the kids.

30 Yards with 19 grain 2800 PSI to 1400 PSI

Shots
#     FPS        FT-LBS     PF
40    789        0.00       0.00     
39    802        0.00       0.00     
38    806        0.00       0.00     
37    810        0.00       0.00     
36    808        0.00       0.00     
35    822        0.00       0.00     
34    821        0.00       0.00     
33    838        0.00       0.00     
32    841        0.00       0.00     
31    830        0.00       0.00     
30    839        0.00       0.00     
29    852        0.00       0.00     
28    846        0.00       0.00     
27    851        0.00       0.00     
26    861        0.00       0.00     
25    855        0.00       0.00     
24    857        0.00       0.00     
23    844        0.00       0.00     
22    846        0.00       0.00     
21    846        0.00       0.00     
20    858        0.00       0.00     
19    857        0.00       0.00     
18    859        0.00       0.00     
17    854        0.00       0.00     
16    837        0.00       0.00     
15    840        0.00       0.00     
14    839        0.00       0.00     
13    841        0.00       0.00     
12    849        0.00       0.00     
11    829        0.00       0.00     
10    834        0.00       0.00     
9     839        0.00       0.00     
8     835        0.00       0.00     
7     828        0.00       0.00     
6     816        0.00       0.00     
5     808        0.00       0.00     
4     821        0.00       0.00     
3     800        0.00       0.00     
2     801        0.00       0.00     
1     808        0.00       0.00     
Average: 832.92
StdDev: 19.58
Min: 789
Max: 861