Can we find accuracy and a use for a .25 to .177 high power conversion ?

Just went out and did a bit of informal trials with the 2 heavy pellets ... Shooting against a dirt bank at @ 80 yards aiming at random walnut size stones the JSB Monsters were not real happy and scattered in an estimated 3-4 inch random pattern. The H&N Sniper Magnums were tight and was able to shoot marble size stones one after another !

This thing is crazy how flat it shoots & also very odd the JSB and H&N when shot sounded completely different ? The JSB's were a crisp SNAP and the H&N a more subdued POP

Perhaps the speed being 30fps or so closer to supersonic ? or there softer lead and less bore drag ... don't know but it was obvious enough to mention.



That works ( Sniper Mags ) being I've got 2 full tins and a partial to tide me over until slugs become viable.

Just went out and did a bit of informal trials with the 2 heavy pellets ... Shooting against a dirt bank at @ 80 yards aiming at random walnut size stones the JSB Monsters were not real happy and scattered in an estimated 3-4 inch random pattern. The H&N Sniper Magnums were tight and was able to shoot marble size stones one after another !

This thing is crazy how flat it shoots & also very odd the JSB and H&N when shot sounded completely different ? The JSB's were a crisp SNAP and the H&N a more subdued POP

Perhaps the speed being 30fps or so closer to supersonic ? or there softer lead and less bore drag ... don't know but it was obvious enough to mention.



That works ( Sniper Mags ) being I've got 2 full tins and a partial to tide me over until slugs become viable.

Click to expand...

Probably the micro supersonic sound waves being displaced. How does it sound dry fired?

Click to expand...

Short dwell POP, tho obviously much louder w/o a pellet and the back pressure closing the balanced valve quicker. With a Pellet / Slug being shot the muzzle report changes quite a bit.

Follow up on the transfer port getting smaller W/O hurting power and Helping efficiency .....
Made another tapered port today exiting at .157" ( #22 drill ) Same power & lower muzzle report.
Port choking even here in .177 cal works like it does on larger calibers !! Could likely go even smaller based off previous testing ... going to leave it for now, these tapered ports take @ 20 min to lathe manufacture.
Previous thread on port choking with balanced valves here: https://www.airgunnation.com/topic/advanced-tuning-for-the-jsar-raptors-as-well-ss-2-balanced-valves/

For clarity, is this the output port on the valve housing that connects into the block? I still haven't taken mine apart (I know for sure that I do not have some of the o-rings that still haven't been fully disclosed for some reason).

Click to expand...

Yes .. the transfer port sits on top of the valve body over the valve bodies discharge / transfer hole has o-rings on both ends. Transfer tube goes up into the receiver and stops just shy of contacting barrel at its transfer hole. The taper is internal being widest at the valve body and narrowest at exit next to barrels port.

Thank you for the description. Does the port in the barrel/thimble need to match the transfer port?

Click to expand...

When you say "match" just understand the calibration size of the system will always be the smallest diameter. So if barrel port is smaller than transfer tube the barrel port controls the flow. If barrel ports larger than transfer port tubes outlet then the transfer port tube controls the flow. * in nearly every case I've used tapered transfer port tubes in balanced valves the tapered transfer tubes outlet has ended up smaller than the *barrel transfer port hole size. * This based on 80% area Transfer holes in barrel.

At Valve end of transfer path any steps of ledges you can eliminate will enhance flow by reducing turbulence. The tapered tube creates Sonic Choking by increasing the speed of the air exiting the transfer tube similar too how a fire hose nozzle works. While increasing back pressure within the throat and causing valve to close quicker. ( balanced valves here ) and not conventional knock open poppet types.

Another week of being locked down at home .. More fiddling around with this .177 slugger conversion.
The original valve used was a JSAR Gen 2 SS body with custom balanced guts. Throat a huge .280", poppet head @ .350" having an exiting transfer port of .250", hammer a fairly heavy 40ish grams.

I was having good results and rifles been shooting well enough, but listening to the muzzle report I knew dwell and general state of tune was not being optimized for the little .177 caliber application.
Took the gun apart pulling the complete valve, hammer too and set aside the SSG set.
In its place went back to an original WAR valve body that has the replaceable seat, where I selected the smallest one i had ... .250" throat with an @ .210" transfer exit. * This seat/ poppet set is an aluminum core peek shell design that is lapped onto the thin seats sealing rim. Poppet O.D. dropped to just .290" being A LOT easier to open ! Balance chamber specs remained the same. My poppet to chamber ratio lower yet. EASY to open !!

Reassembled and started testing ... WHOA !! too much hammer with gun going FULL AUTO for 2-3 seconds making 1000+ psi air dumps. Pulled the hammer, made a new one from 100% mds nylon weighting just 14 grams. Tested again having no problem making the same power ( This H&N Sniper magnum 15 grans ) to 1050 fps at @ 2300 psi. Still tho I could hear the dwell was too long and air use was still not in check.
Hammer out a few more times with the final configuration having a DESTROKE nose on the hammer REDUCING stroke by a full .550" !! .... Active stroke now looks to be @ .350" +/- SHORT STROKE !!
Doing so had to cut the 6# m-rod factory spring @ 3/8" and reset the SSG overall length which also added a bit more spring preload. Assembled with @ 1/16" of free flight the gun now fires with a sharp SNAP and still produces the 1050 fps at the same pressure.
Cocking the gun is ODD being breech opens up with no effort what so ever except for the last @ 3/8" or so. Single finger easy too !

When crunching the new size specs threw the system it is far better suited now for high power .177 use & likely would do well in .22
Throat area minus poppet stem is an equivalent .200" ..... Exit from throat goes into a Tapered transfer tube at .210"/.165" specs. Barrel port an elongated slot offers full bore specs.

Doing some informal accuracy testing certainly lost nothing and feel it gained some from having far less hammer weight with less stroke. Shot cycle is snappier and rifle moves less when fired.


I'm really liking this small caliber flat shooting monster

Scott S