Hi, need help from the guru's (you guys) AT44-10

[Sim597]

Hi all, not new to PCPs, have had some AirForce Talons and Great TDR from Air Arms I wish I didn't sell. That said I just bought my first old world PCP, A Hatsan AT44-10W ($415). I then bought another Hill pump, spent $190 on a scope and rings, $65 on air-stripper/silencer from Wolf, and finally a regulator from eBay new for $69. I was getting 60+ shots easy before regulator. Now I am seeing crazy losses in air volume for each shot, like 5 bar per shot! 75psi per is crazy, it seems to be because the hammer was meant to hit hard due to pressure, now the regulator is set to lowest, it's hitting it way too hard and it takes like 3.0-3.2 pumps per shot, I see it's also set at lowest as I've taken whole thing down right now as I write this. I'm considering cutting maybe 3/16-1/4" off the internal hex to adjust, then reinstall it, it's the only way to lessen spring due to Hatsan leaving us NO back-off room in non Fac rifles? Anyone try this? Is my only option to plug holes in valve?
Thanks guys, I've put easy $900 because I had to buy all the trimmings with this PCP (scope and pump were almost $500 plus the add-ons, I know I could have went ten other ways, almost did, but $415 seems pretty fair for this rifle, Hatsan did send me a new "machine plate" that is the cover for the receiver, it wasn't lettered, and had some glue type crap on it, they took care of me, I also got 15% off most everything and a free cheapo $20 bipod. (I did also install sling screws/sling). and with all this effort and money, I am let down by NOT being able to adjust this one thing to make it more efficient, huge let down, and I've been having fun for first time in a while shooting right in back yard, I broke my back 3 times and have a couple failed surgeries so it was good for me to get around a bit, now just bummed.....
Thanks for any help guys, sorry for long post

 

[LDP]

The Hatsans have a very heavy hammer and after putting in a regulator and having a lower pressure the hammer and hammer spring have way to much force on the valve causing it to stay open longer than needed dumping air out the barrel. You need to trim the hammer weight down and you might also need to use a lighter hammer spring to get it balanced back out so you dont waste air. I believe there is a thread somewhere on a forum dealing with lowering the hammers weight and the spring. Do a search for at44 hammer mods. I know some have shortened the spacer on the spring but I dont think it would be enough in this case to do much.

It will be helpful if you also post the setup.
Whats the reg set at?
what pellets are you using?
what speed do you want the pellet to be at?

 

[Sim597]

Thanks LDP, that's seems right, I always ask, "what makes sense" and I'd basically come to the conclusion it was wasting way more then should, to the point of taking the reg. out. Ok so, you know the hex you can adjust, to make heavier spring because it's tightened all the way down already? Well, I decided to cut that, I figure if I went too far, I can always just back it out, I mean right? Lol I bet your right though and it won't be enough. 
I am just shooting between 20-40 yards, targets for fun only, it's a .177, the regulator I have to guess now, is at prolly 105 bar, and yeah the hammer hits too hard now, imagine it will even quiet down if I can get it to quit wasting so much air.
I hadn't even thought of all this lol, I don't have a problem doing the work as long as I can get it together, having a little trouble getting a pin to catch a tension wire in the trigger now, but I have an idea, just going to use a sacrificial pin then push the real one thru orifice, only thing I can think of, you guys are some smart dudes man. I look up how to lighted the hammer, not sure how you guys do that without messing em' up, I have a dremel, I can mess just about anything up with that! 
Thanks again sir.....cheers -Sim

 

[Sim597]

I'm sure having trouble finding anything on the AT44 but I'm going to try just basic searches on litening up the hammer and it spring. I took 1.6grams off hammer (thru cutting 1/4" off the adjustment screw) and made spring have that same 1/4" less compression. I can take another 1/8" or 3/16" as long as I leave enough to keep some tension between hammer and rear cylinder so spring stays centered.
Don't know how you guys get the trigger assembly back in the tube without losing the tension spring wire, I managed eventually but wow! 
Thanks again LDP, appreciated the help very much.
update: initial test with 11.57g Silver Arrows show marked improvement already, at 1.5 pumps per shot, this is not 100% just quick test. Provides confidence though that I may be able to get this all thru that adjustment nut, even though it's not how Hatsan intended.

 

[LDP]

If you think you need to lighten the hammer after some more tests I have heard of people drilling them to lighten. The hammer has two rings that guide it in the tube you could possible remove part of the rear ring in a mill so it resembles a cross instead of a circle if that makes sense. The last suggestion may or may not cause issues with its function so you would have to look at how the hammer rides and is engaged by the cocking mechanism to decide if it would still work if some of that material is removed. If you have access to a lathe you could make a new hammer and use lighter material for part of it to reduce the weight.

If you decide to alter the hammer make sure you record its original weight so you know how much has been removed while testing.