BT 65 valve and poppet questions?

[ER00z]

I'm not of much help on mods with the BT65, but I did pick one up last year. This is all very interesting.

I did notice they have a heavy hammer and spring, combined with the high flow valve they don't lend themselves to high efficiency/shot count (lol). But do make big power. (Even in .177)

The valve my gun came with was brass and one in the extra cylinder was steel. Made adding a regulator fun, as it worked in the old cylinder, but not the new (or vice versa). Also, there were different valve stems available for various power restrictions. All this is probably old news for those who tuned Hatsan's in years past, but there are still new owners now and then.

Hopefully you get things sorted to your liking. These are big guns in all aspects, looking foreword to your end results.

Take care

[mann]

No it is a single spring it stands for spring stop guide and works better at lower power tunes but still effective on higher power tunes to just not as much you can make a spring guide and a spring capture end  drill and tap the longer end and you use a weaker spring and add spacers on the guide end to increase spring pressure with out increasing length or preload on the hammer leaving room for free flight and enough stifness to stop the hammer bounce just need to make 2 ends one with longer spring guide and one short one drill hole in the smaller end slide bolt threw and drill and tap the other end to capture the spring set it to correct length to give you 20 to 30 thousandths free flight and then you can increase spring pressure as needed with spacers on the guide end I made the guides out of peek and picked up about a 4 in small bolt to capture the spring take measurements and you set it back to same length with spacers in place to increase spring tension if needed you could probably order marauder springs think they are lighter 7 or 8 lbs

[mann]

How large is poppet head

[mann]

With 240 throat hole you could take poppet head down to .300 thousandths which would open easier yet and could use a lighter spring and possibly lighten the hammer too

[customcutter]

Thanks Zack, I've had this one 6-7 years.  Got started on a bullpup stock 5 years ago and got away from the sport.  Just getting back into it and want to make the gun a lot better than it was stock.

[mann]

Ssg

[customcutter]

With 240 throat hole you could take poppet head down to .300 thousandths which would open easier yet and could use a lighter spring and possibly lighten the hammer too

Thanks Mark.  I've got some stainless rod I think.  I may try making a new poppet, and keep this one so I can go back if needed. 
I found this video on SSG's.  You're right that would be pretty easy to fab. Not sure what I had it confused with but it was a spring within a spring.

[customcutter]

Thanks for the pic Mark.  Sometimes I'm a visual learner.  Between your description and the video it sounds good.

[customcutter]

I found this old post by Bob Sterne regarding hammer weights reading some old threads on tuning AT44's and BT65's. 

"Heavy hammers for high power, heavy pellets, and high pressures.... light hammers for less power, light pellets, and lower pressures (eg. regulated).... If you don't change the spring or preload, you get the same valve lift regardless of hammer weight, but heavier hammers give you longer dwell, releasing more air to drive heavier lead.... If you lighten the hammer, generally you have to increase the hammer spring preload a bit to shoot the same pellet at the same velocity....and when pushing the power limits this may make the gun hard to cock....

Bob"

[mann]

The dual spring was a tss they called it mostly used in mrod from what I remember it was also help with hammer bounce . I like the ssg it is easy to adapt it to other platforms

[customcutter]

AARGH!  Just broke the head off of the small diameter bolt I found this morning in my collection trying to turn it down to fit the hole I drilled through the hammer adjustment bolt.  I knew I should have used the 2x72 belt sander and turned it by hand.

Luckily I have 2 more slightly larger diameter bolts that I think I can use, if I drill the opening it a bit larger.  This time I'll turn the head down first before doing the other steps. 

Don't know if I have any Delrin, may have to use the peek.

[mann]

Peek  works too my last one I made was peek

[customcutter]

I got the second bolt to specs, made a piece from Al to thread it into, drilled out the hole a little larger in the hammer spring adjustment bolt.  As I was assembling the SSG I realized this won't work.  As it sits when the bolt is pulled back compressing the spring the 10-24 bolt will extend out the back of the rifle.  When the bolt is released the head of the SSG bolt will catch on the hammer spring adjustment bolt. 

I'm trying to figure a way to have the bolt head go through the hammer, but there is an arm that bolts onto the bottom of the tube.  There is an allen head bolt on the bottom of the bolt probe.  When you cock the rifle the allen head in the bolt probe catches the arm and the arm rotates as it pushes the hammer back.  The small round piece specifically.  The only purpose I can see for this arm is that it is spring loaded and would hold light pressure forward against the bolt probe maybe keeping it from rattling.  That arm results in a slot cut in the face of the hammer almost .25"X1.5".  That requires the large flat disk on the face of the poppet.  

If I drill through the hammer, that would create a rough spot for the rotating arm if I go back to the original configuration.  The hole where the brass piece attaches to the hammer extends all the way through the hammer and is threaded.  So an Allen head bolt could be inserted from the other side that the Allen head in the bolt probe could catch to cock the rifle.

Seems like the whole design is poor and other things were done in order to try to correct previous design flaws.  I'm pretty sure at this point it is an exercise in futility.

Here's a pic in case someone sees something I don't.

[sb327]

If I understand the ssg correctly, it essentially makes an otherwise stock spring into one that allows the hammer to be in free flight while still maintaining most all of the original energy for striking the valve. It also gives a less springy wall for the hammer to hit on the bounce, effectively debouncing it.

A non captive spring (one that allows hammer free flight) essentially does the same but not quite as well due to being more springy as the hammer bounces back into it. But it may be the best option in this situation where a guide gets in the way of other parts.

Dave

[customcutter]

Dave, I think you are correct.  I was looking for a way to help de-bounce the hammer and increase efficiency. 

Right now I'm going to assemble it without that swinging arm.  It looks like I need to make a small piece to bolt to the top of the hammer to push the hammer back about 1/4" more to allow it to cock properly.  Just to see what effect it has on cocking and the shot string.  If that works, I might be able to make the SSG work.

[mann]

Do you have room or is the hammer housing set way down in the stock you could do a external ssg  where the bolt comes out the back and is adjusted on the outside  I'm not familiar with this platform otherwise like stated a shorter stiff spring allowing some free flight might be the easiest solution unless you can figure out a way to cock it differently

[customcutter]

I might be able to partially compress the SSG about 1/2 way, and shorten the bolt.  That might keep the SSG bolt from extending past the back of the hammer spring adjustment bolt.

[mann]

Can you drill threw the hammer adjustment bolt and put the ssg bolt threw it and when you cock it the bolt would go threw the hammer adjuster bolt making it a external ssg which would stick out the back idk if that would work or not BT 65 supposedly uses there own hammer denounce device I don't know what it looks like but I read in the search are that it can be removed don't know if that will help or not

[customcutter]

Can you drill threw the hammer adjustment bolt and put the ssg bolt threw it and when you cock it the bolt would go threw the hammer adjuster bolt making it a external ssg which would stick out the back

That's the way it's set up right now.  But the head on the SSG bolt will hit the back of the hammer adjustment bolt when it tries to go back in.

[customcutter]

I put the receiver back on the hammer/trigger tube.  As suspected it liked about 1/4" of pushing the hammer back far enough to catch on the trigger mech.  I tried taking the receiver back off and the tapered head bolt under the pellet probe stripped out.  I tried finding and even making and oversize allen wrench to get it out.  Tried sharpening a chisel and tapping it out reverse direction.  After several hours of trying I decided to drill off the head thinking I would have about .020" above the lower tube to work with getting it out.  The head popped off about .010" below the surface.  I used a #29 drill .166" IIRC.   I know I don't have any Ease Outs that small or if they would even work, I've never had any luck with slightly larger ones.  At one time I had a set of the square shaped ease outs and they worked pretty well, but I can't seem to find them.  I don't think I can get it out by cutting a grove with a dremel wheel for a flat screwdriver.  Time to start a google search I guess.