On a previous post I noted I upgraded my hammer to 8.5g humma air hammer.
My reg was at 135 and and was achieving 950fps with zans 37gr. This worked fine for speed but accuracy was just ok.so I looked for a better tune. After some correspondence from zan they said I should be shooting them at 985-1010. So I upped my reg up get to these speeds.
However in both my tunes I found the tune ability with the macro was negligible. For example tonight when my reg was back to 135 I was getting 965fps with my macro on 16. I turned the macro gradually to 4 and there was only 3fps decrease.( I’m confused)
The only way I could get any noticeable drop or increase in speed was using my valve adjustment but that’s not the way to tune according to countless videos on YouTube that iv watched
I presume im doing something wrong if my macros isn’t having much of an effect.
Is my hammer too heavy ? Should I use 7.5g or revert back to 6.5g
Any advice ?
i have used both those hammers and have the 8,5 now with my reg at 155 bar 600mm .25
not sure if you have a 25 or 22 but the ZAN slugs for .25 are only good for paperweights way undersize .247 .248 no good .249 249.5
you want a real nice soft slug varmint knocker.
with the 8.5 hammer if you notice the shoulder is taller so it adds preload to the hammer spring
mine on 16 1030+ roll to setting 4 970s
proper way to tune these is 1st set your target speed and roll the valve out 4.5 lines out and leave it there.
roll the power wheel to 16 micro-3.5 i use caliper to measure this and the valve adjuster makes it accurate.
gradually raise reg pressure and adjusting the hammer until you hit the end of the rainbow. for every time you raise the reg and retune
you keep adjusting the micro up more hammer few clicks then shoot there will come a point where you adjust the Micro
that your speed does not increase any more it starts to drop.
this is the curve of the rainbow where you start to back off on the Micro until you hit max velocity again.
now roll the micro until it drops 3-4 fps and stop. this is your max speed for this reg pressure with this hammer adjustment with this grain slug
just before the peak of the rainbow is where you want to be.
if your set target speed is say 980 tune the gun 30-40 fps quicker than target speed so tune for 1020.
once you reach 1020 by raising reg pressure and adjusting hammer spring tension, now can start to click the power wheel back.
with the 8.5 you will need to roll it back to 5 or 4 before you see a decrease of let's say 5-12 fps with the huma 8. 5 takes some adjustment away
but power wheel is only a cam lobe the numbers is just the position of the lobe to me.
so, now it takes 2 clicks vs 1 with this hammer.
ok so now we are at 1000 -998 don't touch the micro or power wheel adjustment any more only the valve adjuster.
start turning it in 1/4 turns at a time it will pick up speed as you turn it in, they all do within a couple turns.
once you notice the speed is now slowing. now turn in 1/8 turns like a clock face 1 -12 o clock and yes that little bit can be as much as 10 fps
as you dial it in, as the speed starts to drop from closing the valve listen to the gun, you will notice it getting quiet and also gaining a ping
at this point you should start shooting 4 to 5 shot groups id shoot H&N before Zan's in .25 imo.
as you turn the valve adjuster you will notice your group sizes shrink to hole in a hole once this is done
take notes of reg hammer valve adjuster micro best to use caliper to measure the micro in mm you can always go back to let's say 18,53mm
vs 3 just about a quarter line, or 2-3/4 out on the valve adjuster vs 7.98mm 8mm
this is the best way i have learned to tune these for best accuracy and efficiency any air coming out of the barrel once the slug leaves
is turbulent air and will disrupt flight of the slug. we record at 1 1/10.000 of a sec slow motion you can watch the slug or pellet Tilt
from this burst behind it.
I've tried all different ways up to now, good luck
this is done at 30 then checked at 50 75 100 +
if you run your reg no higher than 135 run the huma. 7.5 i find the 8.5 is good for 140 up
good luck
!
(see the picture)
