GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: rsterne on July 24, 2012, 01:43:06 AM
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Many thanks to sniper (Dan) for his speedy delivery of my new winter project.... What a BEAUTY!!!....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2541.jpg)
I got the Air Stripper and a full power valve stem as well.... plus a new Leapers 4-16 x 40 AO IR scope which I found I could mount in low rings and still clear just fine.... The gun measures almost 45" long and weighs 9.75 lbs. with the scope....
Hopefully I'll find the time to clean it up and put a few JSB Kings down the barrel before too long....
Bob
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Cool Looking AG! as a project gun, what do you intend to do with it?
Andrew
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Goal is 18 shots at 50-60 FPE if possible....
Bob
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Nice rifle. I look forward to reading about the tuning/modification process. :)
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bob how do you like that leapers scope ? im torn between the 4-16 swat and the 3-12 swat, im one of those stick with what works and scared to buy something different so figured the 3-12 swat would have the same glass as the 3-12 front ao i have
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The 3-12 x 44 SWAT is different glass than the 3-12 x 40 AO.... They have had several models of the SWAT over the years.... I had one of the early ones, and was very disappointed with it.... First of all, it was more like a 4.5-12, the field of view was limited on low power.... and secondly, it wasn't near as bright on low power as the 3-9 x 32 I had.... They may have improved it with later models, I've never bought another.... The sidewheel is a nice feature, the extra weight isn't.... and I'm gunshy of getting another after my first experience, especially with the higher price tag....
The 4-16 x 40 AO is pretty good.... At the highest powers, there seems to be a bit of glare.... I don't know if a sunshade would help that, the store where I bought the scope didn't have them anyway.... but it kind of looks like internal glare/reflections to me.... The IR has the glare from the LEDs typical of all the Leapers I have had with an IR.... although it does have dimmer settings than others I have had.... IMO, the IR is a gimmick, not worth the extra weight.... It does have 9 MilDots per side (10 if you count the post) which is good for long ranges on high power.... I'd like to see how your 3-12 x 40 AO IR compares alongside the 4-16.... I have a feeling the higher magnifications are not worth the extra weight, and the glare may be related to that as well....
Bob
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bob
i havent noticed any glare with my 3-12, and the IR at first i thought was useless but i use it on the lowest brightness for the green light and it doesnt glare at all. i was worried about the reports i had heard of the sight picture going blurry on the 4-16's as you reach the 16x so i opted for the 3-12 and i have a great sight picture thats sharp and clear even around the edges on 12x.
i think i took some pictures looking through the scope on 4x and 12x.. let me check if i did i will pm them to you, dont want to hijack your thread into a scope thread.
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looks like an awesome gun. i have the same scope and must have gotten lucky because its clearer and more precise than my dads 4-12 hawke airmax.
and im really looking forward to seeing just how much you can get from that gun.
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Gotta ask bob, why not the .25cal BT65. It does what you want right out of the box.
Dave
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The size and weight.... The BT65 weighs nearly the same without a scope as mine complete.... In Canada, both come as an under 500 fps rifle, but that's just a simple valve stem change....
Bob
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I cleaned the barrel with Goo Gone and then shot some different pellets to find out how it does in stock non-PAL form.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/Hatsan25Non-PAL.jpg)
From 200 bar down to 85 bar it delivered over 200 shots (23 9-shot clips) within less than a 6% range.... Dropping down to my standard 4% ES requires filling to 195 bar and refilling at 90 bar and gives 21 clips or 189 shots.... The lightest pellets (17.3 gr. Lasers) shot 450 fps (7.8 FPE), H&N Match 21.6 gr. shot 420, JSB King 25.4 gr. averaged 393 fps (8.7 FPE), Baracudas shot 365, and EunJin Domes went 345 fps.... The EunJin Points were too long to cycle reliably in the magazine, but loaded singly shot 320 fps (9.5 FPE).... The 189 shot string of JSBs used 105 bar of air from the 230 cc (14 CI) cylinder for an efficiency of 1.12 FPE/CI (14.6 barcc/FPE)....
All this gives is a baseline for comparison after I swap out the valve stem for the full power one.... It will be interesting to see the difference....
Bob
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The conversion to full power started today.... Here is a photo of the non-PAL (under 500 fps) and full power valve stems.... They seal on a plastic (Delrin?) seat inside the valve housing that is 0.171" diameter....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2549-1.jpg)
The plastic spring seat is pressed into the end of the valve against the large flat end in the photo.... Because it is shouldered and fits flush, it is difficult to remove.... I therefore filed a flat in each side big enough to get the blade of a small flat screwdriver into to pry it out.... as this won't be the last time I take the valve apart....
Here are the port measurements and areas....
Hole in plastic spring seat 0.196" (larger than the ID of the spring)
ID of the valve spring 0.171" (which limits the flow into the valve)
ID of the valve seat 0.171" (area 0.0230 sq.in.)
OD of the non-PAL stem 0.153" (area 0.0184 sq.in.)
Remaining throat area with non-PAL stem 0.0046 sq.in. (equivalent to 0.077" D)
OD of the full power stem 0.100" (area 0.0079 sq.in.)
Remaining throat area with the full power stem 0.0151 sq.in. (equivalent to 0.139" D)
Six exhaust ports measuring 0.105" D each (total area 0.052 sq.in. - over twice what is required)
The conclusion is that (at least in theory) more air can get into the valve through the spring than can get out through the valve throat, which is the limiting factor to airflow in the valve.... From previous experience, the wasted volume of the six exhaust ports and the groove connecting them affects the efficiency, but that is the subject for later experiments.... Later today, I hope to shoot some string with the gun in it's "stock" full power form....
Bob
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I'll be following this one with great interest. Thanks for posting.
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I wonder if BT65 valve bits can be applied to good effect... ;)
cheers,
Douglas
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Have made valve stems for both at44 and bt65....they are completely different and not interchangable.
Al
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Have made valve stems for both at44 and bt65....they are completely different and not interchangable.
Al
Thanks. I'm reading up, trying to decide exactly what rifle I want to buy. The AT44 and BT65 are both on the short list, along with the Marauder and the Sumatra. I'm particularly interested in the 22 or 25 calibers for use in long range shooting.
Since we're on the subject of the AT44 (and, since it's been brought into this thread) the BT65, how hard is it to obtain spare parts and such for these rifles? I know you can pretty much buy an entire Mrod piece by piece from Crosman. What about Hatsan? Are they reasonably customer (tinkerer) friendly?
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The fellow I bought my at44's from (same guy Bob got his from...Dan) stocks a few spare parts. Have tossed around getting a LW drop in barrel from him...those rifles so equipped shoot like a house on fire once lightly tuned. 8)
If I had it to do over again, I would have ordered both rifles with the LW barrels.
Not sure what's available in the US.
Al
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I was getting ready to ask why so low fps! Then I remembered where your from! I hate that in some countries guns are so limited in their potential due to crazy laws!
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I have my PAL.... so standby, that is about to change.... to over 40 FPE in stock "full power" form with just a valve stem change....
Bob
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I got a chance to try a few pellets today in the "full power" version of the gun.... The graph below shows the shot strings for all shots greater than 96% of the maximum velocity for each pellet.... The strings are shifted so that they align with the pressure range which worked for each pellet.... As is typical, the heavier the pellet, the lower the pressure at the peak velocity....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/Hatsan25PAL.jpg)
Summary of results (averages given):
Beeman Laser 17.3 gr. - 965 fps (35.7 FPE) - 22 shots @ 1.25 FPE/CI
H&N Match 21.6 gr. - 899 fps (38.8 FPE) - 23 shots @ 1.27 FPE/CI
JSB Exact King 25.4 gr. - 854 fps (41.1 FPE) - 25 shots @ 1.33 FPE/CI
Benjamin Domed 27.8 gr. - 815 fps (41.0 FPE) - 23 shots @ 1.40 FPE/CI
H&N Baracuda 30.9 gr. - 787 fps (42.5 FPE) - 24 shots @ 1.40 FPE/CI
EunJin Domed 35.3 gr. - 750 fps (44.1 FPE) - 26 shots @ 1.36 FPE/CI
EunJin Pointed 41.7 gr. - 707 fps (46.3 FPE) - only fired 3 shots (single load)
It is interesting to note that Hatsan advertise this rifle as 42 FPE, so they are certainly not exaggerating.... Since the primary purpose of this rifle will be varmint hunting at longer ranges, I will concentrate on the pellets best suited for this purpose.... ie the ones with a good Ballistics Coefficient and a decent muzzle velocity for the job.... The initial development work will be done with the JSB Kings, and if I can get upwards of 50 FPE, I will also try the Benjamin Domes, the new H&N 27.8 gr. Baracuda Hunter Extremes, and the H&N Baracudas.... The next step will be to modify the stock so that I can adjust the hammer spring preload without removing it.... Since the pellets I want to test are topping out at 160-170 bar, and the rifle is good to 200.... I will have to increase the preload to take advantage of what should be more power lurking in this design....
Bob
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The next mod is a relatively simple one that allows the hammer spring preload to be adjusted without removing the stock.... I didn't invent this, just repeating it here for convenience.... The hammer spring preload in the AT44 is adjusted by a screw residing inside the hammer.... It is accessed through a hole just below the safety, using a 4mm allen key about 7" long.... Grinding/filing a slot in the top of the stock allows the allen key to enter the hole.... The hammer is free to rotate, so you also need a way to prevent that.... There is a hole in the bottom of the main tube, 1/2" behind the main stock mounting bolt.... If you peer in through that hole, you will see the hammer, which has a matching hole in it.... The gun must be uncocked for the holes to line up.... Inserting a pin through both holes locks the hammer so you can adjust the preload screw.... Unscrewing the adjustment (ie CCW when viewed from the rear) INCREASES the tension.... Here are photos of the mods to the stock....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2558.jpg)
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2556.jpg)
Once the stock is back on the gun, you can insert a small allen key into the hole in the bottom of the stock until it engages in the hole in the hammer to prevent it from turning.... Grinding a taper on the end allows you to slide it in easier if the alignment of the hole in the hammer isn't perfect.... If it won't drop into the hole in the hammer, then rotate the hammer using the long 4mm allen key until it does.... Note that on the pump action, the hole in the tube is further back, and the hammer must be cocked for the locking holes to line up.... The hole in the stock must be drilled further back as well....
On my rifle, the preload screw moved easily, but I have seen them either loctited or squashed flat to make them tamper resistant.... If the screw rotates too easily, it may be necessary to put a drop of loctite on it once you find the best setting....
Bob
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bob if any one can reach those levels it would be you.. hey maybe add a double tube and go for all out power
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*LOL*.... This beast is heavy enough already....
Bob
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Here is the data for various hammer spring preloads using JSB King 25.4 gr. pellets in the "full power" version of the AT44S-10 Long.... NOTE: pressures on the graph are in bar, not psi....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/Hatsan25JSBKings.jpg)
As you can see, increasing the preload from 2 turns out to 4 increased not only the power, but also the shot count by a couple.... going another 2 turns was a bit too much to achieve maximum shot count, but set up that way the rifle delivered 16 shots averaging 46.6 FPE at 0.97 FPE/CI, so backing it down just slightly should produce 2 clips (18 shots) at about 45 FPE with a 200 bar (2900 psi) fill and bump the efficiency to just over 1.00 FPE/CI....
One small glitch has surfaced, something I knew I would have to watch for from previous experience with a .22 cal AT44.... The hammer spring preload tends to back itself off as you fire the gun, so it will need either some loctite or a locking device on the screw to prevent that.... I'm thinking a hole in the screw with a plastic plug inserted to create friction will probably work....
Bob
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I pulled the gun apart tonight and fixed the problem of the hammer preload screw moving.... I drilled a 1/8" hole about half way through and drove in a Delrin pin and then shaved it off flush with the top of the threads and screwed it in.... It was a bit too tight, but a little shaving with a razor blade and now it's nice and snug but you can adjust it when you want to.... Here is a photo of the hammer and the two allen keys to adjust and hold it.... There is a spacer between the screw and the spring, and it and the hammer spring are sitting on the long allen key I made....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2560.jpg)
I also pulled out the brass sleeve that the valve screws into and checked to see how it lined up with the holes in the valve.... It was just a fraction off lining up with one of the holes, so I machined 0.001" off the end so that when screwed in, one hole lines up perfectly with the transfer port.... The sleeve barely comes flush with the end of the main tube, so if you had to machine off more (0.010" would index the valve about 1 hole) you might also have to machine a small amount off the end of the main tube as well.... I added a punch mark to identify the top hole in the valve.... I also noted that the annular groove in the valve is narrower than the transfer port where the circle is on the photo....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2562.jpg)
Previous experimenting by others on the AT44 showed that plugging the lower three holes has little affect on velocity and reduces air use, thereby increasing efficiency.... I disassembled the valve, tapped the bottom three holes 6-32 (no drilling needed, they are the right size) and installed 3/16" long SHSSs flush with the outer (and inner) surface of the valve.... This not only blocks the holes, but helps reduce the volume of the groove.... If it proves to be the right thing to do, I will fill the remainder of the groove between the screws with JB weld to further reduce the volume....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2563.jpg)
I put a slight bevel on the edges of the groove to fair it into the transfer port.... I will likely be drilling out the top hole to the same size as the TP (0.172") once I have tested this stage.... I may also be plugging the remaining two side holes as well.... that proved to be the best, when used in conjuction with the larger top hole in the .22 cal I worked on....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2564.jpg)
The next step is to reassamble the rifle and test it with the lower 3 holes plugged to check the velocity and efficiency, and what hammer preload adjustment has to be made to compensate....
Bob
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I am having an issue...:) you are not creating new test results as fast as I can read...heh-heh-heh.
cheers,
Douglas
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great information. I'm looking to find this rifle in the states. Doesn't seem many vendors are selling it in .25 or any caliber for the most part.
I've only found the pump action one so far :(
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great information. I'm looking to find this rifle in the states. Doesn't seem many vendors are selling it in .25 or any caliber for the most part.
I've only found the pump action one so far :(
Are you set on the 25, or would a 22 do for you? I've got a link to a vendor with a few 22's on hand. It's the Hamerlli Pneuma version, IIRC. Same rifle except for branding, I am told.
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great information. I'm looking to find this rifle in the states. Doesn't seem many vendors are selling it in .25 or any caliber for the most part.
I've only found the pump action one so far :(
Are you set on the 25, or would a 22 do for you? I've got a link to a vendor with a few 22's on hand. It's the Hamerlli Pneuma version, IIRC. Same rifle except for branding, I am told.
Yes pretty solid on the .25, figure it will make a nice entry into pcp. I'm content with my NP .22 for now. I'm hoping some will be in the country by fall.
Or I find a used .32/.308 haley by than :)
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Lots in Canada, just pick one up along with a full-power valve stem and you're good to go....
Sorry for the delay in results, the Motel is too busy at the moment for me to get any time....
Bob
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I got some time to shoot some strings last night to test the plugging of the three lower holes.... I really like my "Chrony Connect" program and cables I got from the UK, it saves me having to stop and record every shot.... The velocities are stored in a file that I can copy into Excel.... I shot three strings with the hammer preload adjusted 6, 7, and 8 turns out from full in.... The new plastic locking plug in the adjusting screw works perfectly, NO sign of any creep in the adjustment any more.... Here are the results.... NOTE: pressures on the graph are in bar, not psi....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/Hatsan25with3Plugged.jpg)
The first thing I noticed was how much smoother the curves are.... They don't have the large shot-to-shot jumps I saw previously.... It requires two turns more preload on the spring to get the same average velocities as with all six holes open.... but the peak velocity occurs at a slightly higher pressure than before, making a more even bell-curve rather than one with a long front end and quick fall-off after the peak.... This is typical of what I expect to see on restricting the flow slightly.... I also achieved an increase in the efficiency, ie slightly less air was used to generate the same FPE.... 7 turns out gave me 23 shots with 4% averaging 898 fps (45.5 FPE) filling to 200 bar and shooting down to 140, with an efficiency of 1.20 FPE/CI.... That's already a pretty potent quarter-bore....
I'm happy with these results, as they are consistent with what I saw on the .22 cal I worked on.... The bigger caliber required two turns more preload to get back to the same power, whereas the .22 cal only needed one.... I think all we are seeing there is the need for more airflow in the larger caliber.... The next step is to plug the remaining two holes and drill out the top hole to match the transfer port size....
Bob
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keep up the good work Sir!!!!
cheers,
Douglas
--wish I could put a 707 ii on that sort of a plan.
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This morning I had the opportunity to plug the remaining two side holes and drill and chamfer the top hole.... Here is what the top of the valve looks like now....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2581.jpg)
I added some black ink around the hole to make it more visible.... I milled the top hole out to 5/32" and then moved the mill each way 0.006" to enlarge the hole to 0.170" (the same size as the transfer port).... I then plugged the two remaining side holes with 6-32 x 3/16" SHSSs, got out the Dremel with a 1/8" ball grinder tip and smoothed off the front corner of the hole, plus the two side screws where they protruded into the (now larger) top hole.... Once I was finished, I could see the white plastic valve seat, which was "around the corner" before.... The total area of the larger single hole is the same as the three smaller holes from the previous test.... If I gain any performance (or efficiency), it will be from improved flow of the single, streamlined corner and/or the lower drag of a single larger "pipe" compared to three smaller ones.... Assuming this mod works as intended, I will add some JB Weld between the 5 set screws in the groove to get rid of the last bit of wasted volume I can....
Bob
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SWEET!! Can't wait to see more!!
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Here are the shot strings with the 5 holes plugged and the top hole enlarged to 0.180" and streamlined.... It is obviously flowing a lot better, because at 6 turns out on the hammer spring preload, the velocity is back to what it was with all 6 holes open but the efficiency has increased....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/Hatsan25with5Plugged.jpg)
There are three strings above with 25.4 gr. JSB Kings at 5, 6, and 7 turns preload.... and then two additional strings shot at 7 turns out with 30.9 gr. H&N Baracudas and 35.3 gr. EunJin Domes.... The 7T Pressure line applies to all three pellets shot at 7 turns out....
A comparison between the shot string at 6T with the JSBs and the first one shot in the "full power" mode with all 6 holes open is very interesting.... The peak velocity (924 fps) and the average (909/911 fps) is nearly identical.... In the original setup, only 17 shots fell within 4% of the maximum, with the first part of the curve "missing".... Now, I'm getting 22 shots, with the curve shifted down about 13 bar at the peak.... The efficiency has increased from 1.03 FPE/CI to 1.21 FPE/CI, so not only am I getting 5 more shots, each shot is using less air.... In fact, I'm only using 6 bar more air for 22 shots than I was originally for 17 shots....
Here is a comparison for the three pellets at 7 turns preload:
25.4 gr. JSB King: 944 fps (50.3 FPE) max.
930 fps (48.8 FPE) average for 17 shots @ 1.19 FPE/CI
30.9 gr. H&N Baracuda: 882 fps (53.4 FPE) max.
870 fps (50.9 FPE) average for 20 shots @ 1.24 FPE/CI
35.3 gr. EunJin Domed: 837 fps (54.9 FPE) max.
825 fps (53.3 FPE) average for 20 shots @ 1.29 FPE/CI
In order to get two full clips with the JSBs I would need to back the preload down just a whisker and lose a few fps.... Although I have achieved a peak of over 50 FPE with the JSBs and nearly 55 FPE with the EunJins, I'm not quite done yet.... When I had the breech off, I noticed that the hole in the breech and the barrel are slightly smaller than the transfer port.... I think that needs correcting....
Bob
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----When I had the breech off, I noticed that the hole in the breech and the barrel are slightly smaller than the transfer port.... I think that needs correcting....
How far can that hole be opened up before the risk of damaging the pellet during loading gets too high? or...what fraction of 2Pi can you remove with the transfer port? Some care with edge chamfer would probably help, as well as the lead in; as in how tight the pellet fits at that point. Given the smooth twist results I bet you can make a fairly loose fit there w/o risk.
Any time spent checking accuracy yet?
cheers,
Douglas
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I regularly use 75% of the bore for a transfer port with no problems at all.... I've gone to 80%, but I would never go beyond that.... Instead, I would use 75% and lengthen the port to about 133% of the bore to get a port area equal to the bore area in an extreme case.... That would depend on having a valve and all the other porting that would flow that much air, of course.... Since 75% of a quarter-bore is 0.188" and the valve is 0.180" and I doubt I can drill the existing transfer port to 0.188" anyway.... it's not an issue here.... I'll likely just drill the barrel 3/16", round the front corner to prevent the pellet hanging up, and polish the leade a bit....
I've been doing all my shooting inside, and it just stacks the pellets into one ragged hole, no matter which pellet.... That in itself looks promising....
Bob
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Bob,
Have you tried the "extreme case" of having the valve and xfer port equal to 100% of the bore cross section? It seems that you would need a very fast acting/closing valve and/or a long barrel to avoid wasting too much air. I believe you have been a proponent of using the xfer port to more or less regulate the velocity/power output, especially with a valve that might be ported a little too large.
Have you ever gone over 100% with the xfer port/valve porting?
Thanks for your thoughts on this.
Lloyd-ss
Thanks,
Lloyd
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HI Lloyd....
I've never gone over 80% on the barrel port, although the valve throat area has been pushed up towards 100% of the bore, or close to it.... The new .223 benchrest rifles Sean and I are building will be running 100% porting straight through, maybe a bit over that for the throat.... You'll be interested in todays results in the next post....
Bob
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Well, today was kinda wierd.... I took the rifle all apart and matched up all the ports to smooth and maximize the flow.... I ended up with a 0.180" valve top port, 0.183" transfer port, 0.185" through the breech, and a 0.187" barrel port.... I polished the barrel with some bore paste and stuck everything back together and gained a whopping 6 fps (0.5 FPE) for my trouble.... but at least it didn't use any more air, so the efficiency was a solid 1.20 FPE/CI.... Basically all the ports downstream of the valve are as big and smooth as I can go.... By now I figure the choke point is the valve seat itself.... It looks like this....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2553.jpg)
There was a spare supplied with the parts that came with the gun, and it measures 0.171" ID, less the area of the 0.100" stem.... so the equivalvent area is the same as a hole measuring 0.139" (the same size as a stock Disco transfer port).... This is obviously a lot smaller than the rest of my ports.... I figured if I ruined the seat I had a backup, so I knocked it out of the valve and measured it.... and found that the hole in it was even smaller than the spare, it only measured 0.163" ID.... I mounted it in the lathe, and using my number drills, one at a time, slowly took it all the way to 0.187".... the same size as the ports (but still less area because of the stem).... The throat area is now the equivalent of a 0.158" hole, 50% larger area than the one I took out.... There is enough meat to drill the hole out to about 0.200", and I can thin the stem down to 0.090", and match the throat area to the area of the rest of my ports if I need to.... However, I know that if I make the valve too big, the hammer may not open it.... so I stopped at 3/16".... stuck the gun back together and shot some more strings....
WOW!.... What a shocker.... I still had the hammer preload at 7 turns out, hoping that it would have enough oomph to knock open the larger valve at 200 bar.... Well, the first shot over the Chrony was 990 fps, then 1010, and it peaked at 1023 fps before falling back to 983 at shot 15.... Drilling out that valve seat gained me 75 fps and 8 FPE.... and the hammer still worked !!! .... I dialed the preload down to 6 turns, and then down to 5, and the gun was still shooting way stronger than before.... I set the preload back to 7 turns out and shot a string with H&N Baracudas and EunJin Domes.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/Hatsan25BigValve.jpg)
The dotted black lines on the graph are from the first string today, JSB Kings at 7 turns out, before I drilled out the valve seat.... That was the most power up until today.... The red pressure line can be used for all the pellets at 7 turns preload.... Here is a summary of the results:
25.4 gr. JSB King: 1023 fps (59.0 FPE) max.
1009 fps (57.5 FPE) average for 15 shots @ 1.06 FPE/CI
30.9 gr. H&N Baracuda: 957 fps (62.9 FPE) max.
944 fps (61.1 FPE) average for 15 shots @ 1.13 FPE/CI
35.2 gr. EunJin Domed: 915 fps (65.5 FPE) max.
899 fps (63.2 FPE) average for 15 shots @ 1.17 FPE/CI
That's a 9-10 FPE gain over yesterday.... The shot count is a few short of the 18 (two full clips) that I want.... but my power goal of 50-60 FPE has certainly been achieved.... and by enough margin I am confident that I can get an 18 shot string in the 950 fps range with any pellet from 25-31 gr., and that includes all the ones with a decent BC....
It's been quite a day.... Using JB Weld on the groove in the valve will have to wait, the tubes I have are so old they are hard as a rock.... Tuesday (after the holidays) strangely seems a long way off.... but I'll enjoy the weekend knowing I've accomplished my goal with this rifle....
Bob
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Great, I'm in the market for one now. Just a little hard to come by in the States. I'm afraid to think of what the freight would be from Canada. Regards, Tom
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Bob, I have a question. Kinda off toppic to your post but would love your thoughts. For those of us who have the standard AT44's with shorter tube. What if one could make a regulator that would fit on the output end of tube and actually be a 4-5" extension on the air tube as well. Is this possible or even feasable?
Gene
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Since the valve is in the air tube, you would have to extend the tube with the regulator inside and then move the valve to the back of the assembly.... A better solution might be to build a regulator that threads into the existing tube INSTEAD of the valve and then has it's own plenum into which you screw the original valve.... The long tube is 3.3" longer than the standard one.... and has 50cc more volume.... If you can achieve ~30cc of plenum for a .22 cal and ~45cc for a .25 cal you will leave the potential FPE of the gun largely unaffected.... Perhaps just use the long tube and set the regulator inside, and forward about 3"?.... However, regulators are still best when used for lower to mid power levels because then you can extend the usuable pressure range to a lower setpoint....
BTW, Tom, postage to the USA is usually a bit less than within Canada.... go figure....
Bob
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Well, today was kinda wierd.... I took the rifle all apart and matched up all the ports to smooth and maximize the flow.... I ended up with a 0.180" valve top port, 0.183" transfer port, 0.185" through the breech, and a 0.187" barrel port.... I polished the barrel with some bore paste and stuck everything back together and gained a whopping 6 fps (0.5 FPE) for my trouble.... but at least it didn't use any more air, so the efficiency was a solid 1.20 FPE/CI.... Basically all the ports downstream of the valve are as big and smooth as I can go.... By now I figure the choke point is the valve seat itself.... It looks like this....
There was a spare supplied with the parts that came with the gun, and it measures 0.171" ID, less the area of the 0.100" stem.... so the equivalvent area is the same as a hole measuring 0.139" (the same size as a stock Disco transfer port).... This is obviously a lot smaller than the rest of my ports.... I figured if I ruined the seat I had a backup, so I knocked it out of the valve and measured it.... and found that the hole in it was even smaller than the spare, it only measured 0.163" ID.... I mounted it in the lathe, and using my number drills, one at a time, slowly took it all the way to 0.187".... the same size as the ports (but still less area because of the stem).... The throat area is now the equivalent of a 0.158" hole, 50% larger area than the one I took out.... There is enough meat to drill the hole out to about 0.200", and I can thin the stem down to 0.090", and match the throat area to the area of the rest of my ports if I need to.... However, I know that if I make the valve too big, the hammer may not open it.... so I stopped at 3/16".... stuck the gun back together and shot some more strings....
WOW!.... What a shocker.... I still had the hammer preload at 7 turns out, hoping that it would have enough oomph to knock open the larger valve at 200 bar.... Well, the first shot over the Chrony was 990 fps, then 1010, and it peaked at 1023 fps before falling back to 983 at shot 15.... Drilling out that valve seat gained me 75 fps and 8 FPE.... and the hammer still worked !!! .... I dialed the preload down to 6 turns, and then down to 5, and the gun was still shooting way stronger than before.... I set the preload back to 7 turns out and shot a string with H&N Baracudas and EunJin Domes.... Here are the results....
The dotted black lines on the graph are from the first string today, JSB Kings at 7 turns out, before I drilled out the valve seat.... That was the most power up until today.... The red pressure line can be used for all the pellets at 7 turns preload.... Here is a summary of the results:
25.4 gr. JSB King: 1023 fps (59.0 FPE) max.
1009 fps (57.5 FPE) average for 15 shots @ 1.06 FPE/CI
30.9 gr. H&N Baracuda: 957 fps (62.9 FPE) max.
944 fps (61.1 FPE) average for 15 shots @ 1.13 FPE/CI
35.2 gr. EunJin Domed: 915 fps (65.5 FPE) max.
899 fps (63.2 FPE) average for 15 shots @ 1.17 FPE/CI
That's a 9-10 FPE gain over yesterday.... The shot count is a few short of the 18 (two full clips) that I want.... but my power goal of 50-60 FPE has certainly been achieved.... and by enough margin I am confident that I can get an 18 shot string in the 950 fps range with any pellet from 25-31 gr., and that includes all the ones with a decent BC....
It's been quite a day.... Using JB Weld on the groove in the valve will have to wait, the tubes I have are so old they are hard as a rock.... Tuesday (after the holidays) strangely seems a long way off.... but I'll enjoy the weekend knowing I've accomplished my goal with this rifle....
Bob
Bob,
Excellent work incrementing the power up and analyzing the choke points. It really does show how these guns are "systems" with many variables that must work together. Your hard work is paying off for all of us!
Lloyd-ss
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I'm pretty sure that drilling out the valve seat and/or thinning the stem to get the same area as the porting would give even more power.... However, I'm pretty sure that I would then have to choke down the transfer port to get the shot count (18) and flatness of shot string that I want.... That may ultimately be the best solution, and if nothing else, it would prove the theory about matching up the port areas.... plus maybe put the gun up into the 70 FPE area with EunJins.... I'm pretty sure, now that I've seen I have plenty of hammer power with a 3/16" valve throat, that opening it up another 0.020" would still work OK.... Maybe after I use JB Weld in the groove in the valve....
Bob
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Just a photo of the valve with the groove filled with JB Weld.... The idea is to take up the extra volume in between the valve seat and the pellet to help keep the pressure up in the first part of the pulse....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2582.jpg)
Testing later tonight, time permitting....
Bob
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Got some time this evening to do the testing of the valve with the groove filled in with JB Weld.... As expected, there was a slight gain in performance, but the efficiency has pretty much leveled out.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/Hatsan25JBWeld.jpg)
The interesting thing about this version is that the performance at mid-preload settings continues to improve.... The best shot strings are now happening at less preload than before.... I got 19 shots within 4% with the JSB Kings, 971-1007-968, averaging 992 fps (55.5 FPE) at 1.13 FPE/CI, filling to 200 bar and shooting down to 133 bar at 6 turns of preload.... The best strings with the H&N Baracudas and the EunJin Domes were at 6.5 and 7 turns of preload respectively, and returned 16 shots....
I shot a few pellets at 8 turns of preload, and the velocities were peaked pretty much at 200 bar for the lighter pellets and 180 for the heaviest.... The maximums recorded were:
25.4 gr. JSB Kings - 1046 fps - 61.7 FPE
30.9 gr. H&N Baracudas - 982 fps - 66.2 FPE
35.2 gr. EunJin Domes - 939 fps - 69.1 FPE
41.7 gr. EunJin Pointed - 881 fps - 71.9 FPE
I think there is a bit more in the gun yet, I could enlarge the valve throat a bit more and slim the stem.... and then I might have to make the inlet side of the valve breathe a bit better as well.... If I do that, I will then have to restrict the transfer port to keep the velocity under 1000 fps with the JSB Kings.... so I don't know if it's worth it....
Bob
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I decided to finish the job.... I drilled out the valve seat to 0.203" and thinned the stem to 0.090".... That makes the throat of the valve the same area as the valve exhaust port.... In addition, I drilled four 7/64" holes at a 20 degree angle in the inner end of the valve to allow more air to enter the valve.... This has more than doubled the inlet area, so it is now a lot easier for air to enter the valve than leave it....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/IMG_2583.jpg)
The extra holes in the inlet side should not be necessary unless the valve seat is drilled out, as the original hole was the same size as the throat, and it didn't have a stem obstructing it.... Hopefully I will find time to test again tonight.... Sorry for the slightly blurry photo....
Bob
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Got to run some strings over the Chrony tonight.... can you see the smirk on my face?.... Drilling out the valve throat and slimming the stem, combined with opening up the inlet on the valve.... gave me the highest performance I have yet achieved.... The larger valve seat required an additional turn on the hammer spring preload to overcome the extra force holdind the valve shut.... but even without doing that the performance was up, although it was at a lower pressure.... Once I went from 6 turns preload to 7, the entire 17 shot string of 25.4 gr. JSBs was over 1000 fps, peaking at 1044 (61.5 FPE)....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/Hatsan25MaxedValve.jpg)
I didn't bother adding more hammer preload when I shot the Baracudas and EJ Domes, so the graphs above are a direct comparison of the three pellets at the same power setting.... The 'Cudas peaked at 65.4 FPE and the EunJins at 67.5 FPE, but they would be shooting over 70 FPE had I bothered to add enough preload to bring the start of the string up to 200 bar instead of 175.... I cranked up the preload for a few shots with the EunJin Pointed 41.7 gr. pellets, and at 11 turns of preload and 190 bar I got 78.4 FPE.... I'm thinking with 12 turns, right at 200 bar, I can hit 80 FPE (for one shot)....
This rifle has turned out to be a real beast.... I've likely got too much velocity even for the 'Cudas, but until I get the opportunity to put some lead a lot further downrange I won't know if I can get away with leaving the tune as is, or if I'll have to detune it for accuracy.... Nice problem to have, though !!!
EDIT: I forgot to add that the efficiency for the above strings was 1.11 FPE/CI for the Kings, 1.21 FPE/CI for the 'Cudas, and 1.28 FPE/CI for the Domes.... so not only is the performance up, so is the efficiency....
Bob
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One thing which has puzzled me about this gun is that when I dial the power back with the hammer spring preload, the shot count doesn't increase.... I decided today to fit the oversized 0.153" non-PAL valve stem into the now very much oversized ports and test it.... After doing that, I turned the stem down to 0.140" in the throat area, which is the size of the main part of the stem, and ran more tests.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/Hatsan25BigValveFatStems.jpg)
It appears that the best way to tune the Hatsan is to adjust the valve stem size to adjust the power, and then use the hammer spring preload to adjust the operating pressures.... certainly if you want to get the best efficiency.... Using the best strings from the above and previous graphs, and always starting from 200 bar (or as close as possible), here are the choices I have so far with JSB King 25.4 gr. pellets.... In all cases, only those shots within 4% of the maximum velocity in the string are counted, and the average FPE for the string is stated....
17 shots at 59.5 FPE (1027 fps) at 1.11 FPE/CI, refill at 130 bar
19 shots at 55.4 FPE (991 fps) at 1.13 FPE/CI, refill at 133 bar
22 shots at 51.6 FPE (957 fps) at 1.16 FPE/CI, refill at 130 bar
25 shots at 45.6 FPE (899 fps) at 1.22 FPE/CI, refill at 133 bar
31 shots at 43.4 FPE (877 fps) at 1.28 FPE/CI, refill at 122 bar
Other than with the mildest tune, I have a usuable pressure range of 1000 psi, from 2900 down to 1900, and with the 43 FPE tune, that range is extended down to about 1750 psi.... Other tunes in between should be possible with the right combination of valve stem diameter and hammer preload.... Small adjustments can be made with just the preload.... I'm very pleased with the shot count and the efficiency figures I have been able to achieve with this rifle.... and I'm looking forward to doing some accuracy and pellet testing....
Bob
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Bob, your work is simply amazing. Cannot wait to hear how she shoots. Boy do I wish you would tune one of these for me.
Dave
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Bob,
I am with Grumpy on this, your work is always top notch, and we all learn a lot.
The delrin pellet you used to keep the hammer adjustment from changing.... how is that holding up? Can you feel the resistance when you make an adjustment? You have been cranking that screw back and forth a bunch so you have really put it to the test.
Thanks,
Lloyd-ss
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It's holding up just fine.... still quite a bit of resistance, although not as tight as when I first installed it.... Like you say, I've really given it a workout, under normal circumstances it would still be tight.... There is no sign of it losing adjustment, that's for sure....
Bob
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It's holding up just fine.... still quite a bit of resistance, although not as tight as when I first installed it.... Like you say, I've really given it a workout, under normal circumstances it would still be tight.... There is no sign of it losing adjustment, that's for sure....
Bob
Bob,
A good trick to know. I will use that somewhere.
Lloyd
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Bob,
This has been most impressive to read through. How did your accuracy turn out after all of these changes?
Chris
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50 yards, JSB Kings....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/50ydHatsanJSB_zpse4bb129b.jpg) (http://s378.photobucket.com/user/rsterne/media/Hatsan%20AT44-10/50ydHatsanJSB_zpse4bb129b.jpg.html)
100 yards, same.... small squares on target are 1/2"....
(http://i378.photobucket.com/albums/oo221/rsterne/Hatsan%20AT44-10/100ydHatsanJSB_zps8242a781.jpg) (http://s378.photobucket.com/user/rsterne/media/Hatsan%20AT44-10/100ydHatsanJSB_zps8242a781.jpg.html)
Bob
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Bob, whats your initial impressions of the quality of the gun like fit and finish, trigger, lever cocking smoothness etc. I know its going to be loud though. Oh, what's a PAL?.
jimmy
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Pretty decent gun for the money, IMO.... and I love the side lever cocking instead of a bolt.... In Canada all airguns over 500 fps are firearms and you need a Possession and Acquistion License for them....
Bob
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Pretty decent gun for the money, IMO.... and I love the side lever cocking instead of a bolt.... In Canada all airguns over 500 fps are firearms and you need a Possession and Acquistion License for them....
Bob
Thanks Bob, lots of possibilities with those AT's.
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Hello, just recieved my Hatsan AT44 Tactical and have some idea to improve the gun when there is time (and will follow this approach).
Since I have never been involved into PCP air guns just some toy springers a number of years ago (try 35) this thread have been really educative in many ways. I am Civil engineer so I know my physics and through that knowledge I have been reading this thread a couple of times now and feel that I am both acquainted to the PCP system and understand the different changes and can follow the results, why they occure and how. A big thanks for this illustrative lesson, even if you did not know from the beginning that you were writing a crash course into PCP air guns.
I just need to get things a little clearer since I don't know all the shortenings yet. FPE should be FootPoundEnergy I presume? Then I wonder how efficiency is calculated FPE/CI, my guess is that CI is Cubic Inch but then I wonder if you are using the total CI of the tank as reference or is it recalculated via the actual pressure in the tube?
I also would like to know if Hatsan are producing their air guns according to the metric system or in inch. I know that you are fond of the inches but to us who don't use it in daily life it is rather confusing so if Hatsan are making them in the metric system I just want to confirm that your figures, when it come to diameters and areas are abbreviations into your system. I will double check anyway when I start dismantling my own air gun but I still have some weeks until I have the time to do it.
Yet another time, thank you for some really interesting educational material!!
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FPE is indeed Foot Pounds Energy, and CI is Cubic Inches of air used.... In this case, it is the volume of air at 1 bar pressure, calculated from the volume of the air reservoir times the pressure drop in bar for the shot string.... The total FPE is the FPE average per shot times the number of shots in the string....
Bob
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Just out of curiosity what type of machining tools were you using to do this project? Bench top lathe? Milling machine? Dremel tools and finger nail files? I am going to start my power up mods in the near future so I was just curious on whom to befriend.
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All of the mods except drilling the front of the valve to allow in more air were done with hand tools (portable drill, bits, taps, files, etc.) I used a mill to drill the angled holes in that step....
Bob
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This is one of the most informative posts that I have come across. Thank you for taking the time to document and support your information. I have accessed it several times for info on my own gun. Thank you for taking the time.
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Well it was bound to happen. I opened up my rifle today and started the power mods. Filing down the brass sleeve was time consuming since I had to take an extra amount off to get it indexed correctly. You were correct in your statement of having to also trim down the trigger tube body to allow clearance. On both accounts I wish I had a bench top lathe. It would have made my evening much easier. I was just starting to piece it back together then it happened. I couldnt remember what side of the hammer spring the spacer goes on. I thought it came out of the hammer its self but all the diagrams I am finding show it on the other side. Thoughts?
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If you are talking about the delrin( white plastic ) ring , it goes in first then the spring.
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I was actually talking about the hammer spring spacer I think it goes between the spring and the adjuster screw.
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Sorry, I was thinking of the valve for some reason.
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I went to start on mine the other day had all the 6-32 x 3/16 setscrews ready spent some time fishing around in the bottom of my shooting bag for the correct size allen wrench went to check fit the screws into the holes before I started venting and taking things apart and guess what, a BT-65 .25 caliber has much bigger holes the 6-32 set screws fell right through them so I am guessing I will be needing some 10-32 x 3/16.....
Bob, can you make me a new valve seat out of that peak material?
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One of the issues I have come across is the valve body and brass sleeve alignment. I took off the O-rings to keep from damaging them during my fit tests. This actually gave me a false fit. With the O-rings removed it allows the sleeve to screw completely down on the valve body. I machined the sleeve down enough so that I get an exact valve hole to transfer port alignment. When I put the O-ring back on I am no longer in alignment but actually back at the same spot before any work was done. At this point my options are to install a smaller O-ring or machine out enough of the brass sleeve to allow for the O-ring to seat at the exact depth that the two shoulders come into contact. I installed 4 of the set screws with some pipe thread sealant to help keep them from moving around until I get it to where my OCD will let me sleep at night.
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OleTomCat.... Sorry, I don't make any parts or guns or do machine work for others.... no time to even get my own stuff done....
Bob
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OleTomCat.... Sorry, I don't make any parts or guns or do machine work for others.... no time to even get my own stuff done....
Bob
Know anyone that could make it for me, I don't have the tools available anymore to make custom parts since I changed jobs and moved up to management....
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Of the 3 pellets tested for fpe , wihat one was most accurate?
Thanks Kenn
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The most accurate pellet in my AT-44S was the 25.4 gr. JSB King by a wide margin....
Bob
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great thread... lot's of info on this one ..... I think I will use this to help tune the new gladius Bob did a fantastic job with a ton of testing ...
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Found this thread while looking for mods to do on my BT65. I know it's an old thread, but just wanted to thank Bob for documenting and posting all the hard work he did while tuning his AT44S-10. It was like taking a "How to mod your PCP 101" class.
Bob, do you still think that drilling the 4 holes in the back of the valve gained anything? I will be modding my BT soon, but fail to see how this helps. I also haven't seen the back of the valve so maybe I'm missing something.
thanks again,
Ken
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I don't know if it helped or not.... I just wanted to make sure that way more air could get into the valve than could possibly get out through the throat and ports....
Bob
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You're not going to need to do any mods to the intake side of the valve to increase air flow. The BT valve has a metal spring seat retainer that has 7 holes to allow very good air flow.
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Nice to know.... never seen an BT65....
Bob
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Yep, same way on the Galatian too. I did take a larger drill bit, and take the "corners" off the 7 holes on one I did though. I doubt it made any difference, but it made me feel better :D Depending on caliber, you may not need to touch the valve seat either if its a .177 or .22.
You are correct about this post though. It has made life easier for countless Hatsan owners, myself included!
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Super wright up!!! Thank you, Joe
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Hi, Bob - What a write-up! Certainly a good reference for anyone with an AT44.
I have an AT44S-10 Long in .25 that has been back to HatsanUSA twice. With your rifle, you experimented with many fill pressures and hammer spring settings. Did you at any time experience significant POI shifts?
Thanks for all of the time spent sharing your efforts and results with us.
Jere
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Hi Bob
This is another great modding and testing of a AT44 for all of us to learn from and really makes the work for us much easier as well. I have the same gun in 22 and have yet to touch it since it shoots so good in stock form. I am getting a good 28 shots with JSB 18.13s starting at 975fps down to around 910 fps and get another 5 or so just under 900fps with no POI change at 50 yards from 3000 psi down to 1800 psi . After reading this thread I have a good idea of what I want to do to improve mine even more. It also does quite well at 100 yards with sub 2" groups with light winds.
Just a quick question about the monocoque gun you were waiting on bullet molds for, did you get the molds and finish the gun and shot it yet because if you did I must have missed it. If so can you point me to the link for it as I am interested in your results with it.
Thanks again for your hard work to benefit all of us.
Mike
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hi,
where can i get discharge valve for AT44-10 air cylinder ?
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hi,
where can i get discharge valve for AT44-10 air cylinder ?
The only place I know would be direct from Hatsan, but we'll see if the real mechanics check in with a better answer.
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As far as I know only Hatsan at this time.
Mike
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You could try contacting Dan at the CAF Store.... http://www.airgunforum.ca/store/index.php?cPath=25&osCsid=9r6p5op2hnssh7p8injs6cviu6 (http://www.airgunforum.ca/store/index.php?cPath=25&osCsid=9r6p5op2hnssh7p8injs6cviu6)
I have purchased a Hatsan valve from him in the past....
Bob
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I have ordered the entire valve assembly from Hatsan with no problems.
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Okay guys, I really need some help with my AT44 .25 cal. Last year I installed an Audrius reg and have been trying to tune it. I finally grew a pair and file grooved the cylinder threads so that the reg can vent properly, vs. the credit card gap method which i dont think works well. I'm meeting my goal which is 750 fps with 27.8 gr but that is only accomplished with alot of hammer preload and reg turned all the way up. The gun is a AIRHOG and is very loud. Too loud to comfortably shoot in back yard. The Audrius consistency is doing very well since file grooving. My question is this. Would doing Bob's mod help me? I would drill everything to 3/16" along with plugging 5 holes. Im thinking that it would allow me to SUBSTANTIALLY lower hammer preload and reg settings, therefore making much more quiet, powerful and effecient. Any comments or help would be greatly appreciated.
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I have never regulated a Hatsan, so I can't say for sure.... However, if the gun is loud and an air hog, you can be pretty sure you are running way too much hammer strike.... When you install a regulator, you almost always have to REDUCE the hammer strike, rather than increase it.... Dial back the preload until you see a drop in velocity and then another 3-5%.... That will put you on the knee of the curve.... If your velocity is too low, increase your regulator pressure and repeat the procedure....
Drilling the top port and all others to 3/16", and plugging the other 5 holes will increase the efficiency.... but it sounds like you have too much hammer strike to me....
Bob
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Yes Bob I agree that I do have way too much hammer strike but like a said in order to achieve 750 fps with 28.7 gr I had to turn reg way up in BAR and hammer really heavy. My thought was if gun was opened up with your mod then I could lighten hammer and reg and still get goal fps.
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Well Bob after a good night's sleep and some consideration..ive decided to instead only drill to 11/64". With some of the tight tolerances with oring seat placements I feel that this would be much safer choice. I can always go back and redrill if results aren't good enough. My fps goals aren't near what yours were on yours. I did however last night drill the delrin valve seat to 3/16" and replaced into valve. Out of fear of poppett not sealing and leaking I aired up tank and to my very pleasant surprise this morning im at full BAR. Thanks for your help, Trevor
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Well Bob after a good night's sleep and some consideration..ive decided to instead only drill to 11/64". With some of the tight tolerances with oring seat placements I feel that this would be much safer choice. I can always go back and redrill if results aren't good enough. My fps goals aren't near what yours were on yours. I did however last night drill the delrin valve seat to 3/16" and replaced into valve. Out of fear of poppett not sealing and leaking I aired up tank and to my very pleasant surprise this morning im at full BAR. Thanks for your help, Trevor
Doing all of Bob's mods will help to an extent. The better the gun can breathe, the easier it is to make power at lower pressures. You also have to remember that a regulated gun can only make power with the air available in the regulator plenum. It doesn't have the amount of air to work with that an unregulated gun has. You should be perfectly safe opening everything up to 3/16 on a .25. The tightest tolerance you will have will be with the transfer port. I usually open that up with rolled up sand paper, because it is really easy to mess that little brass sleeve up with a drill. Sometimes, people miss opening up everything they need to. You want to open up the valve seat, cylinder carrier hole(the hole in the brass part that the transfer port sits in), the transfer port, and the barrel port. You can take rolled up sand paper and clean up the hole on that valve seat(derlin piece) so that a 3/16 bit fits through it easily. That derlin gives a lot when drilling it, so that 3/16 bit will end up making a hole that is a little under 3/16. Bob's mod on the valve itself will help with efficiency, and can help with power if properly lined up.
You should be able to hit your 34-35fpe goal pretty easily in .25 with a reg setting around 130 bar give or take. Just don't cut any corners and take your time with things, and it should wake that gun up significantly. Obviously, you'll never get close to Bob's power numbers on a regulated gun, but 35fpe shouldn't be an issue. What Bob said about the HS is critical on a good regulated tune. I hope that helps.
Happy shooting :)
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Hey Rallyshark thanks for your valuable helpful advise. Would a small concave file be ok for transfer port? I'll try both it and your sandpaper tip. I'll go ahead while guns dismantled and open it up to 3/16". I've ordered some dremel pointed grinding stones to chamfur my valve. It lines up perfectly with transfer port but due to bit hanging seizing on raised ridge, chaumfer is necessary to allow bigger 3/16 bit to spin. As far as the delrin seat is concerned..that suckers drilled close to 3/16. I really drilled back and forth. Its back in valve and poppet doesnt leak..praise the Lord. I'm not removing it to redrill! Thanks again!!
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Hey Rallyshark thanks for your valuable helpful advise. Would a small concave file be ok for transfer port? I'll try both it and your sandpaper tip. I'll go ahead while guns dismantled and open it up to 3/16". I've ordered some dremel pointed grinding stones to chamfur my valve. It lines up perfectly with transfer port but due to bit hanging seizing on raised ridge, chaumfer is necessary to allow bigger 3/16 bit to spin. As far as the delrin seat is concerned..that suckers drilled close to 3/16. I really drilled back and forth. Its back in valve and poppet doesnt leak..praise the Lord. I'm not removing it to redrill! Thanks again!!
I use the tightly rolled up sand paper in 160 or 220 then 400 grit(to smooth it out a bit more, while rotating the transfer port in my fingers to keep the hole round. Using a file will require being very careful not to make the hole egg shaped. I would stick with the sand paper myself, but I'm sure you could do it with a file as long as you're careful. I usually use a small carbide cutter to open the hole up with a dremel, and then clean it up with a small diamond bit. If you're just going to use a drill, then just keep moving up in bit size, until you're able to drill it with the preferred size. A pointed bit to add a chamfur can work as well. The derlin isn't that bad about not sealing, but I certainly understand not wanting to risk it too. The sealing issue really happens when you make a new valve seat out of PEEK. That one can be a bear to get to seal,lol.
After you get it all back together, start with the HS setting at minimum. Then keep increasing, until the fps doesn't increase anymore, or very little. As the master(Bob) mentioned, back the hammer spring back down to about 5% lower velocity to get the best tune at that reg pressure. In other words, you want your reg set were your max velocity is around 790-800, then back the HS down until you reach the 750 you're looking for. You'll have that bad boy shooting good in no time :D
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Appreciate the great info!
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;DHey Rallyshark me again. I got all passages drilled to 3/16"..even took out that delrin seat and gave er a good extra reaming. After what u said I thought about going up a size bit on it..but I didn't. Got TP to 3/16 using both file and SP then drill bit. Even got small valve holes all tapped and screwed and JB welded it up. One allen screw was in path of poppet..so I had to back it out a bit. Test screwed it into my Hatsan brass degasser tool and is smooth..no cutting or rubbing. Also screwed valve into position on gun and it is spot on PERFECT alignment..which brings me to this question. How necessary is it to chamfeur valve hole. I read that it was done due to hole not aligning perfect..but mine is. I can always do it later but i think im gonna leave well enough alone. Can't wait til daylight to get it out and CHRONY!!
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;DHey Rallyshark me again. I got all passages drilled to 3/16"..even took out that delrin seat and gave er a good extra reaming. After what u said I thought about going up a size bit on it..but I didn't. Got TP to 3/16 using both file and SP then drill bit. Even got small valve holes all tapped and screwed and JB welded it up. One allen screw was in path of poppet..so I had to back it out a bit. Test screwed it into my Hatsan brass degasser tool and is smooth..no cutting or rubbing. Also screwed valve into position on gun and it is spot on PERFECT alignment..which brings me to this question. How necessary is it to chamfeur valve hole. I read that it was done due to hole not aligning perfect..but mine is. I can always do it later but i think im gonna leave well enough alone. Can't wait til daylight to get it out and CHRONY!!
If it is lined up, then no need to mess with it. Just leave it as is :) Can't wait to see how it goes!
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;DHey Rallyshark, i was finally able to get some chrony done on the Bob's mod results. Yesterday, i was a bit disappointed in my numbers. Did some reading on it last night at work. I came to the conclusion that it is my Audrius reg. I have had it set WAY TO HIGH. I'm talking like over 250 bar high. Basically when i first got it I woiuld set it then woiuldn't get FPS I wanted so i would increase, again and again until the nob actually came loose at one point...yea i know it's embarrassing. So this morning i removed the reg, cranked it CW as tight as i could go, MARKED the reg so i could better gauge my settings and started adjusting until i finally met goal of mid 750's with 27.8 gr. My technique was i would increase reg, then lower hammer and continue until i finally increased reg and FPS went down. I then knew i went too far. I think i ended up around 180 BAR. I do have to say that when tuning a gun with reg and hammer, it is so valuable to have a Yung Heng compressor. Makes the work so much easier and faster. Anyway, i ran a 9 shot string at the end and am very consistently at mid 750's, but im still louder hammer than i wouild like, which brings me to the question of do you think a Lane or Huma regulator would handle more BAR and allow me to decrease hammer more. I hate to make the investment but i did only pay like $60 for the Audrius. Otherwise, im pretty happy. WIll make a great hunting gun and plinker when my neighbors arent home. Thanks!
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One other thing..i read that the Audrius reg does great with .177 and .22 but just can't handle the high pressure demands of the .25. Is great in my .22 AT44.
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I think you still have stuff all out of whack there. There's no way that reg should need to be at 180 bar. It should be around 130-140 tops I would think. Something isn't right, if you have to set it at 180bar to get 35fpe out of a .25? I would mark the cylinder, so you know where the opened hole on the valve is, and make SURE it is pointing straight up when the cylinder is in the gun. Also, make sure you aren't getting any leaks at the probe or barrel o-rings. Better yet, take the reg out, and see what the max power of the gun is. If you can't get it in 50+fpe range without the reg, something isn't right(assuming all of the mods are correct and lined up). One more thing... Is this an AT44 short or long, and is it a QE/have an LDC? The loud report tells me it likely isn't tuned correctly(too much HS). For example: Bob's mods done to an AT44 long will do 35fpe in .22 with a reg setting of 130bar(Huma).
The good thing about the Huma regs is that they are marked, so you have a pretty good idea of where they are set. They also come with a different plenum for .25 vs .22/.177. I still say to put that big o-ring back on the valve and see what the gun is doing without the reg. That will take the reg out of the mix, and give you a good idea if the gun is working like it should otherwise.
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Hey Rallyshark..i just ran a 18 shot chrony on regulated gun. Average 748. SD 4.84. Spread 21. I prefer my SD in the 2s but it's still the best so far on that gun. Thought about taking reg out and running chrony but I think im just gonna leave it alone. 18 shots is ok from what I've read. Also..i did dry fire sound test indoors with a phone app and it's at 72 dec. My Flash is at 74 and i always considered it too be pretty quiet for a .25. I think I may just be spoiled to my AT44 .22 and Gauntlet .22s noise. Also when I chrony I'm shooting into a big oak tree at 10 feet so that may be causing perceived loudness. Anyway thanks for all ur great advise. I bought some more 6-32 allens and plan to do Bobs mod on my AT44 .22 next. Not that I need more power but for shot count. Planning on porting all to 11/64". Guns currently a paintball buster at 50 yds.
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P S. Actually on that 18th shot I think I may have fell off reg. It was 737. So my SD and Spread were much better. 125 bar left when done.
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P S. Actually on that 18th shot I think I may have fell off reg. It was 737. So my SD and Spread were much better. 125 bar left when done.
As long as you're happy, that's all the matters :) You never answered if it was a long or a short AT44? If it is a long, then I still say something definitely isn't right. You're running 10-12 shots shy of what you should be getting in a long fwiw. Either way, happy shooting, and feel free to PM me if you have questions.
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Short QE.
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Short QE.
In that case, I don't feel as bad about it,lol! The down side is, I would have told you to take the reg out from the start had I known it was a short .25. As a side note, you can get a very good 20 shot string without a reg in that gun at significantly higher power. You can easily get a great string over 40fpe. Now that you've opened everything up, it will be a beast without that reg. It will probably be quieter as well. I say relocate that reg to a .22 or .177 :D
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Yeah I thought about that as well..hatsan usa has had a great deal on a refurb AT44 .177 pump for $199. But like I really need a third gun this year. I may try that and see how she chronys.
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Yeah I thought about that as well..hatsan usa has had a great deal on a refurb AT44 .177 pump for $199. But like I really need a third gun this year. I may try that and see how she chronys.
It should be quite the thumper without that reg in it :)
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Hey Rallyshark, I should probably just message u direct instead of overextending this thread but here goes. I finally got a chance to try to sight in my AT44 .25 today at 27 and 40 yards. First off, it's shotgunning something aweful. All over the paper. Still louder than i like, but it does seem to hit pretty hard. Well, i noticed that when i shot it I felt air coming from the magazine. I then confirmed this by taping some TP over magazine and sure enough it's a blowing out the magazine. I think they call that the breach? Am i correct? Anyway, I wonder if one or both of the 2 barrel oring's surrounding barrel port are scalped. As a matter of remembrance, 2 years ago when i was pretty new to airgunning and just received this gun, I was trying to clean barrel and ended up getting cleaning cloths somehow jammed in barrel. I ended up pulling off barrel and didn't really know what i was doing at the time, I either scalped something or possibly left off or lost something. All i know is that after i put it back together, it started being loud and has been loud ever since. Last week when i removed barrel to do the 3/16" drilling i checked the orings but didn't see anything overly obvious. Anyway, your thoughts are very appreciated. Maybe i can end up getting this gun to shoot right eventually. If airs blowing out magazine something soiunds wonky!!
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You can replace the two o-rings on the outside of the barrel for good measure, but your problem is likely the one o-ring inside the barrel that seals the probe. If you got the gun new, there is probably one in the little kit of o-rings that came with it. Either one will lead to lower velocities, which means that gun should be making more power :D Yes, feel free to message me directly. Also, a little know fact is that the end of the barrel is a cap that screws off, making that o-ring much easier to replace(probe/breech o-ring). That cap is hard to get off on some guns, fyi.
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How do u get that cap off without scratching barrel?
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I dont think mine comes off.. just used electrical taped vise grips to attempt. Scratched it bad. Hope it dont leak worse now :(
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I dont think mine comes off.. just used electrical taped vise grips to attempt. Scratched it bad. Hope it dont leak worse now :(
Like I said, some are very hard to get off, and are glued on. Scratching that part won't hurt anything. Just use a spring hook or something to fish the o-ring out, if you can't get the cap off. I've even used a staple bent into a little hook to get the o-ring out before. A small paper clip can be made into a little hook too. Like you said, let's move this to PM, to avoid running off with Mr. Sterne's awesome post :)
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Ok, so this is my last post on this thread. I feel that i have abused it enough..sorry Bob. Last night i managed to resurrect a 2 year old sleeping AT44 .25. For the last 2 years, unbeknownst to me it had no breach oring. Air was just blowing out the magazine. After Bob's mod completion, it was still shooting terrible. and very loud. After managing to replace breech oring and other 2 barrel orings, it is a whole new gun. This morning i readjusted the hammer and regulator and managed a very satisfying 27 shot chrony string with 27.8 gr Benjamin's with 745 fps average, 2.51 SD!!, and spread of 10! That's not too shabby in my book. Gun is crazy quiet for a .25 especially since adding 10 stage baffles off Ebay. Also, since replacing breech oring, the magazine cycles so much easier. It was jamming something aweful before. Gotta give a shout out to Rallyshark who has been much help and encouragement through this long process. I'm now planning on doing Bob's mod on my .22 AT44.
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That is great! Bob deserves all the credit for most of us Hatsan tinkerers waking up our AT44s and other Hatsans. If not for his exhaustive testing AND documenting the process in this thread, many of us would still be a few shots and fpe behind the curve :)
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I apologize in advance for bumping such an old thread.
I want to give a shout out to rsterne for sharing his wisdom on these modification detailed out in this thread.
I performed these mods to my Bullboss in .25 cal and wanted to share my results.
After much testing I am right where I want to be in terms of fps and am surprised how consistent this has become. This is unregulated!
JSB 25.39
01. 928
02. 931
03. 930
04. 933
05. 932
06. 932
07. 938
08. 940
09. 936
10. 918
11. 935
12. 935
13. 933
14. 931
15. 932
16. 930
17. 931
18. 930
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I apologize in advance for bumping such an old thread.
I want to give a shout out to rsterne for sharing his wisdom on these modification detailed out in this thread.
I performed these mods to my Bullboss in .25 cal and wanted to share my results.
After much testing I am right where I want to be in terms of fps and am surprised how consistent this has become. This is unregulated!
JSB 25.39
01. 928
02. 931
03. 930
04. 933
05. 932
06. 932
07. 938
08. 940
09. 936
10. 918
11. 935
12. 935
13. 933
14. 931
15. 932
16. 930
17. 931
18. 930
That would be a really nice string if regulated. Unregulated, it is amazing! Good work. What does a 50 yd target look like?
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Accuracy tests will be another day. I want to try the Hades too.
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Accuracy tests will be another day. I want to try the Hades too.
I'll be looking forward to them! Good luck.
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Happy to report accuracy is spot on with JSB 25gr. Pretty darn close to hole in hole at 50 yards.
The JSB heavys both mk1 and mk2 open up at 50 yards which is unfortunate. Although I haven't adjusted the current tune geared for the 25gr. This same tune slings the heavys avg 802 fps for 18 shots. They stacked at 22 yards sight in though. Perhaps if i give more preload they might group better.
I have Hades on order as well as some various slugs to try out. I will likely re-tune for the slugs. 28gr and 30gr on the way.
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Have referred to this post many many times ....
Still following ...
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Hades on backorder.
Testing today with various slugs at 22 yards.
28gr and 30gr that appear to be replicas or similar to fx hybrid.
28gr with hollow base
30gr dish base
initially dialed strings over the chrony. I was trying to achieve 950+ fps but that wasnt happening. 910 was max but shot count was only 12 with 3% spread. To get 2 mags ave velocity is 875fps with 3% spread. At these speeds the only one grouping well is the 28gr hollow base slug. Whats interesting is I will get a few hole in hole and then a flier. I think this may be due to how the pellet in loaded in magazine and what the probe does while loading into breech. They are a tad too long for the magazine.
I will order these hollow base slugs in 25gr to have a better fit in magazine and to sling at higher fps.
to be continued...
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Some more testing today. Concluded that the magazine fitment is not the issue.
Today is 17mph sustained winds with over 25mph gusts. Accuracy testing at 22 yards off a bipod and cheap walmart table.
5 shot groups
30gr Dish Slugs (.250) Avg 829 fps 1.02"
28gr Hybrid Slugs (.249) Avg 863 fps .85"
30 gr Hybrid Slugs (.249) Avg 834 fps 1.09"
28 gr Deep Hollow Base (.250) Avg 873 1.57"
All not acceptable at 22 yards!
I just got in Varmint knockers 32.8gr Flat Base Slugs.
(.250) Avg 855 fps .39"
This is good news and will test further out on less windy day. Best slug out of the Bullboss so far.
Also on the way is the Hades pellets, AVS slugs, NSA slugs and lighter weight Deep hollow base slugs.
More to come...
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I created a new thread if interested to follow.
https://www.gatewaytoairguns.org/GTA/index.php?topic=167799.new#new (https://www.gatewaytoairguns.org/GTA/index.php?topic=167799.new#new)
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NT