Tuned AT44 Long (.177) Shot String

[SpiralGroove]

Hey Guys,
I need to do more tweaking to improve the following shot strings, but here is what I have so far:
Both strings using 10.5 CPUM and using between 200 bar to 100 bar in air.  Also 20 cc plenum and all valve holes plugged, except 1 drilled to 9/64".  Barrel port is 9/64" (stock) and transfer port is slightly larger than the OEM 11/64" (made larger to ensure alignment with valve hole).  All springs are stock.

Shots - String 1:  (Pre-Load 1 turn out)
   1-10  906, 907, ER2, 917, 916, 910, 918, 914, 925, 909
 11-20  918, 917, ER2, 924, 911, ER2, 909, 923, ER2, 903
 21-30  920, 929, 928, 926, 919, 924, 917, 918, 928, 931
 31-40  928, 927, 927, ER2, ER2, 924, 920, 924, 932, 927 
 41-50  923, 932, 925, 931, 934, ER2, ER2, 926, ER2, 926
 51-60  928, 926, 923, 929, 913, 930, 924, 918, 912, 911
 61-70  909, 904, 907, 898, ER2, 892, 888, 882, 880, 875
If we take the first 63 shots ES=28 or 3%, E=1.09%
___________________________________________________________

Shots - String 2: (Pre-Load 3/4 turns out)
   1-10  890, ER2, 909, 897, 897, 901, 908, 899, 909, 910
 11-20  895, 904, 894, 905, 905, 910, 906, 913, 911, 912
 21-30  895, 909, 910, 910, 887, 902, 892, 900, 890, 899
 31-40  906, 900, 905, 906, 898, 907, 909, 892, 898, 900 
 41-50  902, 904, 912, 898, 909, 916, 909, 901, 909, 907
 51-60  902, 906, 894, 903, 903, 909, 902, ER2, 882, 893
 61-70  900, 882, 877, 867, 865, 870, 869, 855, 859, 847
If we take the first 62 shots ES=34 or 3.37%, E=1.04%

Still working on, but getting frustrated, I know this can be better

Also, since I put the regulator in backwards and pumped to 200 bar, I likely damaged the regulator and that is why my ES is so high   I would not expect this from a new one.........Kirk

[rsterne]

I know what you've been through, and that looks about as good as it's going to get.... I prefer the first string.... You could try using that setup and a slightly smaller transfer port to bring the velocity down to 900.... It might just tighten up the ES and increase your efficiency and shot count.... Worth trying, IMO.... I'd try 1/8" (no sense in 9/64", your other ports are already that size.... and you can always use number drills to sneak it larger again if necessary....

Bob

[stretch]

Very interesting.  I hope I'm not diverting the thread too much but I have a question, how much of an "extreme spread" in chrony numbers is -good- versus -not good enough-?  I ask because my goal is 50 yard target shooting and would like to achieve accuracy as good (or better) as .22lr.  Taking CCI Standard Velocity ammo, for example, which is 40 grain, has a muzzle velocity of 1070 and one set of chrony numbers showed it had an extreme spread of 51 fps.  CCI SV is considered pretty decent ammo, but it's ES is almost double the numbers you're seeing.  Would that mean that your rifle could shoot tighter groups at 50 yards than the PB using CCI SV?  If so, this is exactly the direction I hope to go. 

[Ribbonstone]

Haven't found anything wrong with finding the area of your airguns tightest velocity spread and staying inside that area when trying for your very best groups. Are those that say its not much help, but every little bit you get on your side is a help.

Do keep in mind that that 40gr bullet has a BC about 4X (400%) better than a good pellet, so the effects of a little velocity variation at short (50yard) range isn't going to be too drastic.

[rsterne]

For a "minimum acceptable" ES I use 4% for 50 yards, 3% for 75 yards and 2% for 100 yards, with a PCP shooting round nosed pellets (ie with a decent BC) at velocities around 800-950 fps.... If the velocity is lower, or the BC poorer (eg. a wadcutter) you will need a tighter ES.... If you are plinking at 25 yards, a 10% ES will likely do you just fine....

Bob

[SpiralGroove]

Hey Stretch,
If your thinking about regulating, the standard ES threshold is 2% or less.  So my two strings at 3% & 3.37% are poor.
My BAM B50 gets 70 shots at 1.9%, so I think this regulator is having problems due to my abuse.  I'm researching if there is a fix besides a new one.

[stretch]

Interesting and encouraging.

[PIPERMAN]

Kirk you did a fine job
I think the reg is working fine,let there be 4-5 seconds between shots.
Regs hate moisture in air tube

[Rdsail]

Good strings if they were for a unregulated rifle. I would definitely check your regulator. From my experience, I the regulator should give you 5 to 15fps spread.

good luck!

[PIPERMAN]

Good strings if they were for a unregulated rifle. I would definitely check your regulator. From my experience, I the regulator should give you 5 to 15fps spread.

good luck!

At44 is not MPR 

Parts of shot strings,mpr .177 no modofications



AT44 short,audrius regulator in



both with 8.44 grain

AT44 -10 .22 short,audrius regulator in,18.1 grain

 

i made these videos 2 years ago,44's are much better now

[stretch]

i made these videos 2 years ago,44's are much better now

What's different about the "new" 44's?  I believe the AT44-W10 short I bought last week is an "old" model (it has 2 barrel bands).

Where can I buy an "andrius regulator"?

[PIPERMAN]

I meant my 44's are much better now 
Send a mail to pcpregulator@gmail.com and ask him,price here is 69€ shipped

[Bwalton]

The reg should give you a much lower es, I can get a 15 shot string without reg of a 11-13 es with the reg it was like es of 9, but I only need 15shots as I am only hunting. with the reg I lost about 50fps, so I went back to unreg for the power and a 11-13 es.

[Bwalton]

I hope this helps a bit, here is a tread that myself and Bob discussed when I was thinking about going to a Reg, and by the way our very own GTA member Milo74 makes the best regs for the Hatsan and is local! they work very very well. hope some of this info helps

http://www.gatewaytoairguns.org/GTA/index.php?topic=69885.0

[stretch]

Thanks for the info, I'm off to do some homework... 

[SpiralGroove]

Hey Stretch,
I'm using a regulator by Milo74 ($80) for this post.
I also have the same AT44-10 Short - Wood that you have.  If I regulate it, hoping to get 50 to 55 shots using JSB 10.34 or CPUM at 915/925 fps should be doable > w/ES less than 2%.

Kirk

[stretch]

Hey Stretch,
I'm using a regulator by Milo74 ($80) for this post.
I also have the same AT44-10 Short - Wood that you have.  Getting 50 to 55 regulated shots using JSB 10.34 or CPUM at 915/925 fps should be doable > w/ES less than 2%.

Kirk

Looking forward to reading about your progress on this.  Good luck! 

[Motorhead]

Agree on choking the transfer tube size a bit, should reduce ES #'s and only bumb power back a tad

[SpiralGroove]

Finally got what I believe is gonna be my best tune I can get, unless a lighter hammer is made.
First things first -->> Big Thanks to Bob & Scott for support & patience
The Tune:
1) Plug all valve holes except 1, increased remaining hole to 9/64" (OEM was 3/32")
2) Covered all holes w/JB weld
3) No Sail Used - was found to hurt performance; removing depinger was found to significantly hurt performance.
4) Decreased (new) transfer port to 9/64" (stock was 11/64")
5) Barrel port left OEM
6) Regulator setpoint 1450 (100 bar)
7) Preload 1 turn out

String: CPUM 10.5; 200 bar to 100 bar
   1-10   903, 919, 917, 918, 918, 914, 910, 924, 921, 912
 11-20   917, 900, 914, 912, 914, 917, 910, 915, 907, 917
 21-30   907, 920, 916, 912, 914, 918, 912, 915, 913, 919
 31-40   915, 923, 914, 916, 901, 921, 913, 920, 918, 921
 41-50   920, 924, 906, 923, 920, 911, 924, 920, 924, 918
 51-60   920, 915, ER2, 908, 914, 918, 914, 905, 909, 915
 61-70   909, 917, 911, 903, 898, 898, 892, 890, 888, 885
 70 Shots at 915 fps (ave) w/ 185 cc of air -> efficiency =1.21%; ES -> 39 or 4.22%
First 64 shots ES = 2.6% 

Boy, did I shoot a lot of pellets - getting better w/crony .............Kirk   

[Motorhead]

Kirk,
Seeing velocity dive as you come off regulation ... Reg set point could be up a tad higher 
This would have you also slightly increasing Hammer spring tension ... end result it would come off reg a tad higher in pressure and the slightly harder hammer hit will give more dwell and get rifle to come off the reg closer to the bell curve peak and NOT on the downward slope as it is now.

Your closer