New redesigned JSB monster pellets

When I got my buddies in it was only doing 400fps with 14.3gr pellets, the monsters are 25 whatever grain. I didn’t try the monsters until I turned the hammer spring up. I’m not sure if it would have stuck a monster how it was tuned but I bet it could have. If it’s tuned that low you’re probably operating in valve lock and getting very inconsistent velocities. That would explain it shooting some and sticking some.
 
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I’m not a Hatsan guy at all, I’ve literally played with one for a few hours, but I think I can get you there. You really need a chronograph if you don’t have one. You can get a cheapo off eBay or Amazon that actually works pretty good for $30-$40.

First: Remove the stock.

Second: Cock (pull the bolt back until it locks, COCKING the bolt) the bolt and remove the set screw below the bolt through the little hole, don’t lock the bolt down or you won’t have access to the screw. I think it takes a 2mm Allen wrench. You can leave it out until you’re done making adjustments then put it back in.

Third: Insert a 4mm Allen wrench through the hole in the back of the action. The hole is just a little bigger than your Allen wrench.

Fourth: Turn the adjuster counter clockwise to increase hammer tension. Make small 1/8 or 1/4 turn adjustments. My buddies gun responded a lot to small adjustments.

You really have no way of knowing when you’re at a good tune without a chronograph, but you can kind of make due. Make an adjustment and shoot a group at 20 yards. If you like that group shoot another at 40 yards and check you drop. If you can live with the trajectory and accuracy call it good until you get a chrony. If you had the strelock app or chairgun app you could get close to figuring your velocity out using data you got from your groups. The more groups you shoot at longer ranges, the closer you will get on your velocity.
 
Here’s the chronograph I use. I got the premium kit, but it’s double the price.


Here’s the cheapo, you can find it on eBay from American sellers also. Amazon can get it to you faster if you like Amazon. I’ve used this one alot and it’s worked great for the money.