Impact .22 barrel and JSB Monsters 25.4gr
Hi guys
Need advice.
I’ve shoot the JSB Monsters out of the Impact and maximum possible fps is 815. I want to get the speed up to 920-950 as general consensus is that this pellet shoots very accurate above 900fps.
Transfer port on the .22 barrel is 4.3 – 4.4mm
Transfer port on the .25 barrel is 4.8 – 4.9mm
O-ring groove to start of TP gap: 1.14mm on .25, 1.28mm on .22
.22 barrel length is 18″
.25 barrel length is 23″ iirc
I’m wondering if it’s worthwhile to open up the TP on the .22 and the probe and if yes, does it have to be a round hole or can it be oval shaped? If round, I’ll have to take more material off the probe. Not sure what difference round and oval would make, if any.
I can get some pictures up if required.
Thanka
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Viewing 14 replies - 1 through 14 (of 14 total)
Hi Rowdy
Thanks for your input. It is interesting that after maxing out at 870fps I was discussing the airflow and the pellet probe design with a friend and here’s your post suggesting an angled port. Going to have a revised look at all this, after your pointer.
Yesterday I pulled out the .22 barrel after a few months to test the new 18.1gr so gave the Monsters another go.
Was comparing the skirt size of the new batch of 18.1gr (with thicker skirts, new die by JSB) and these 25.4g and found the monsters to be at least 0.05mm wider. Quick search on another forum and came across resizing by ajshoots of these pellets so decided to a crude resizing of the skirts from avg 5.7mm down to 5.57mm and 5.53mm (pushing pellet through the pelletgage twice and then y-roll test on glass). Head size is consistent for the batch I have, between 5.52mm and 5.53mm (dropping through 5.53mm hole on pelletgage).
12x resized to 5.57mm and 12x resized to 5.53mm
Weight 25.4g for all
Distance 30m
Average 830fps/52.7J/38.9fpe (JSB states that these are for 50J+ rifles)
FX Impact 18″ ST barrel, Power 5, 145bar regulator, Valve between 2nd & 3rd line
5.57mm skirt pellet group was as before, not good.
10 shots 1inch+ group with 2 flyers way off (not part of 1″ group).
All between 828fps and 838fps, except one at 793fps
These pellets were not making a clean round hole either, as earlier tests, thus confirming an unstable/wobbly flight.
5.53mm skirt pellets group was a real surprise …
10 shots group of 0.6inch!
All between 827fps and 838fps.
Shots 2,3,4 & 5 were literally one hole stacks before hole opened up …
This may have been a smaller group had the rifle been on the shooting bag instead of the bipod and I was taking rushed shots as well.
Clean round holes which must mean a stable flight.
Also, these pellets at 830fps were hitting just about 0.3inch below the zero of 18.1gr at 880fps (Power C).
Then shot 6 direct from the tin, no resizing etc. 780fps, 824fps, 774fps, 835fps, 777fps, 757fps … and a shotgun/spray pattern as usual.
Going to slug the barrel, measure and then order NOE size dies. This pellet does seem to have potential out of this barrel/rifle, it seems, only if it is resized. Once the resizing dies are in hand, then I will crank up the regulator and valve to get to 870fps. Let’s see if a repeat of a similar group can be achieved at 830fps.
I was following this thread also with great interest. I did notice that his .30 barrel view of the port cut, was slightly into the O-ring groove!!!
That has always been a bad thing for my doings 🙂 and I don’t do that 🙂
I have always liked everything about the Impact and still may get me one before its all over. I will be just like Verve here and would want to be able to shoot those JSB Monsters @ 920-950 in the .22 caliber.
I would also be doing this from a 24″ barrel and not a smooth twist either, I would rather just get me a CZ barrel blank and profile it to the Impact and I would add an extra O-ring groove if the receiver allowed that.
No friggn’ way the port would be cutting into that O-ring groove either. I have had some really nice and tight setups that didn’t touch each other as the .30 barrel here does; and shoot a few rounds all smiles and then it suck the O-ring partially into the barrel…
After inspection to see where the power went too 🙂
So for my 2 cents worth here, new and longer 24″ barrel and add an extra O-ring and make sure to use the Viton O-rings with good lube, then see where his fps is? The added length is a big plus and will help with better shot count also…
Very interesting thread going on here, hope to read the process continue toward what his goal was with the
.22 JSB Monsters…
One other tip I do is when I drill that port in the barrel, I land it where it should go, to match up with the receiver; I just angle mill it toward the muzzle end of the barrel.
This does three things different and you get a beenie out of this effort. First off the port is still round, but the angled cut makes a longer surface profile, so its in a sense bigger surface area at the barrel to receiver match up.
Then second, the angled cut port allows less resistance in the discharge, getting the shot heading out and down the barrel quicker. This is a huge plus, least has for me… Then depending on your receiver port size you can cone shape in a sense by honing the two sides out to open up more to match up better to your receiver… Depends on the port size in the receiver.
Third, this angled port also allows the pellets into the chamber without shaving them as they are being pushed by the probe, past the port, works really smooth, even when making a hurried follow up shot.
Just need to measure exactly where your pellet probe pushes the pellet and not exceed the skirt of the pellet with where the port ends up on the inside of the barrel.
Port must all be behind pellet skirt.
That, and or increase the depth of how far in the pellet probe pushes the projectile of choice, into the chamber… Its well worth the exact lay out of this mod for the angled cut port guys… Even if you have to mod the probe to stuff the pellet deeper in the barrel, if there is no fudge factor with it to begin with.
I have seen 25 fps increase from a perpendicular straight in port cut, going in angled. My doing this has been huge, and has no lose in shot count or any other negative effect on the barrels I did this on…
Its like the next best thing for bang for your bucks to a rear mounted tank and discharge straight down the bore, as with the Talon and Condors… Its that big a beenie…
Any body found any more out about this thread?
Sweet, i think Ernest Rowe made some of those brass end bits out of aluminium or something. Not sure if he sells them though
Yes I’ve got the reg pressure back down to 130bar, and shot half a mag of 18gr. At power 5 these were flying out at around 980. Got the power down to level 1 and 920fps which stacked last 4 shots in a hole tad bigger than a single pellet hole.
Going to shoot a few mags of these later today to confirm I’ve not botched it all up. fingers crossed :confusedn:
Interesting, did you try normal pellets just to verify you didn’t fux it up?
Opened the TP and pellet probe to 4.9mm. reg pressure 150bar.
Maximum fps is 872 and and ES is 7fps in 36 shots which was quite surprising. But groups are staggered 1″ at 25meters. Below 850fps there’s no group per se.
Perhaps the 18″ barrel is just not enough … it did shoot a pellet upon pellet for 3 shots but that was that hahaha
Maybe a 24″ LW barrel is the calling .. really intrigued by this pellet.
At 150bar reg pressure, it goes up to 855fps max :sadn:
Time to get the dremmel and open the TP in very small increments. Thinking of making the TP hole kinda cone shaped so that it’s wider on the outside and inside remain the same and leave probe untouched. That should allow more airflow … theoretically.
Thanks Wingman.
I’ve set the regulator at 130bar, and can get the .25 JSB Kings 25.4gr up to 920+ easily. I’ll increase the pressure gradually to 150bar and check for the maximum possible speed of .22 Monsters without making any changes to the TP.
Been holding buying a 4mm dia acetal rod to push test the pellet but I think it’s time to get that and also to polish the barrel.
Will report back how I got on with the reg pressure increase. It’s something I wanted to avoid as reg takes a good while to settle after any adjustments but I guess it should be done first.
Personally I wouldnt go any larger than 4.5mm on a .22 transfer port as the pellets tend to drop their heads into the TP and shave lead causing inaccuracies.
You can lift the velocity of those heavy pellets by raising the reg pressure to 150ish bar.
Left .30, middle .25 and right .22
I could get the .22 TP machined to match .25, then matching the valve exhaust port shouldn’t be an issue as you can see the .30 port is substantially bigger.
I think I should be okay as long as I widen the hole in the pellet probe to match the increased TP.
I’ll ping Ernest if he can chime in on this.
My Cricket tp is oval, but lengthwise and not sideways if you know what I mean
Before Peter at TGAG went off track he was working on a .25 magnum and a .30 caliber Cricket. He tried the oval TP with little success. There needed to be a match between the valve exhaust port and the TP on the barrel. He tried the oval for the same reason you are thinking of. I must admit I am not familiar with the impact so take what I am saying with a grain of salt. I know Ernest has performed this modification on other guns, honestly he’s the best resource for this topic.
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WOW!!!
You have had some very interesting stuff going on there. I must admit I love doing stuff like that, I just don’t want to if a hurry is involved 🙂 Its not something to do an being in a hurry.
I have never got to mess with the st barrels. I want to see if they may be exactly what a person needs for shooting solid round balls. Biggy thing for me would be to get a barrel that could shoot solid round balls hard, around 1000 fps or faster; just would insist them being extremely accurite…
I come across a barrel that could do that, I will build a gun around that barrel. Shooting solid rounds well, you need a very slow twist rate; or none at all… Just seems to me this newer way of rifling and choking these barrels, it begs the question of ” just really how well would the solid round ball shoot from these barrels?”
Your in the project of something that is very interesting and that something so small, can have really big results. It really puts a grin on one’s face too, when you make this happen right in front of you.
You keep me posted too, please. I like to learn as well also. You ever want to try solid rounds in your .22 barrel, please just pm me and I can fix you right up with some of them. Nice really snug rounds too… Their just a bit over 14grains, forget at the minute just how much, but its like .3 or .4 gr.
For me though, shooting solid round balls and hard, they have their on way through the point of impact. Way out at the farther reach, them losing the rifling; there is no tumbling really. They just roll on!!! 🙂
Hey good luck with all this too…