what fps does your jsb's like?

My .22 Marauder pushes the 18.1s at 740 fps and groups very well at that speed. My .25 Marauder is pushing the 25.4s at 785 fps and groups well also. Neither is a smooth twist barrel like the FX though. My Marauders are tuned for low fill pressure so they don't shoot as fast as stock tune.
John

Don't forget you need to break the gun in let the reg settle in, what type of groups are you getting? Have you cleaned the barrel? 

I spoke with a few knowledgeable airgun tuners and competitors about the max fps they thought pellets shot at accurately. A good gun and barrel 860 - 880 fps should give tight groups was the answer. All of my PCP's shot JSB's 890 - 915 fps accurately.

What tells me its not the pellet speed is both your 22 and 25 aren't grouping at sub 880 fps. First are the barrels clean? If so the check to see if the pellet is going into the barrel undamaged. The pellet should be entering the barrel without any resistance. Being its an Impact load a pellet then remove the barrel. Push the pellet gently out with a cleaning rod put a cleaning patch on the end of the rod. Do this with both barrels.

Note: Be careful. I would take the air cylinder off before loading and checking for pellet damage.

At the risk of stating the obvious and perhaps insulting your intelligence, don't make the mistake this newbie made by partially supporting the barrel/ shroud on a bench rest. I was not getting any physical clipping but the positional changes, however slight, were such that my groups were inconsistent every time I moved or placed the gun back in the rest. Groups tightened right up when this was pointed out to me. Just saying. 

The 25 grain JSB shoot well for me at 922-925 fps. The 33 grain heavies shoot superbly well at the 822-828 range. I have shot both of these at ranges from 50 to 160 yards at s steel target measuring 5 inches. The 25 grains hit 6 out of 9 times in winds at about 20 miles. The 33 grains hit 8 out of 9 times.

I have seen JSB 18 going close to 980 in a cricket and they grouped just as well as an FX400 shooting 880. Each gun is different t have you tried other pellets beside JSB?
You also have not stated what the groups sizes and distance are. Also have you checked all the known issues like magazine, bolt probe moderator etc. 

Best pellets and fps for a given barrel can be optimized, but it is difficult.

Shoot bench-rested indoors to negate wind effects, over 20yd if you can. Make sure to clean the barrel consistently (say between groups), and repeat it the same way every time. Also use very consistent resting/shooting. Then shoot and measure several groups (or score USARB targets, etc) for each FPS setting. Once you are confident in this, you can vary FPS and measure group results as a function of velocity.

It is good to run chrony tests too, to see if there are problems with extreme spread. The regulator normally has been optimized for a certain velocity/power range. If you adjust too far away from this ES will jump and you'll get vertical stringing.

You can also dig deeper by trying different lots of pellets, as these vary too.

Did you try shooting it without the ldc, airstripper, endcap etc?. Did you slow motion film any groups? My wildcat wasn't grouping good and until I got a casio high speed camera and filmed some groups I would have never known that the pellets were wobbling and spiraling. I adjusted the pellet probe because it was seating the pellets too far and crushing one side of the skirt. Even having fixed that the pellets were slightly clipping the airstripper and endcap. I drilled them out a little bigger and now its very accurate. The velocities your shooting at are fine. It must be another issue like the one I had.Good luck.

Oh yeah. I also polished my bore with jb and lube my pellets

My Cricket shoots 18 gr JSB's at around 900 fps and groups very well.

Sounds like you got good advise so far.
Every barrel/rifle/pellet combo can be different, there may well be ( just making it up here ) one smooth twist rig in the world that shoots $3.00 tin Chinese domes well at all speeds ( kidding but you get the idea).
Also just for your enjoyment an airgun, may, at any point in life desided a totally different pellet is best. That one is fun tracking down.


Can a barrel/pellet shoot a large span, 800-900fps?
Yes , only testing will tell though.
I have a 25" HW .22 barrel that will shoot 15.9g JSB ( and NO other pellet) sub moa from 730fps all the way to 1040fps. That is a VERY odd barrel but I'll keep it.

Generally, shooting slower than "best" group speed ( thinking most folks want 900+) will be just fine. I've seen many many .177 rigs that shot well at 880fps down to 600fps.
Had a career 707 II .25 that grouped well from 900 down to 400fps but naturally 400 was for indoor, the groups were there though.

"Any downside to polishing?"
Yes, IF you over do it you could ruin any barrel potentially!
If you've done it before or maybe just read the tutorial posted here somewhere and you go slow and carefull, polishing wont hurt and many people do it to all barrels at least very lightly.

One thing I like to do when I have accuracy questions about a rig is take it to a match ( cal. doesn't matter ) then hand it to a couple of different darn good shooters and see what they do. If you can adjust the power easily/fast find some other local shooters and have fun! I personally love doing things like that with other airgun folks.


John

I'll say it again. Some .22s just don't shoot well no matter what pellet or what speed you shoot. Seems to be the nature of the beast.

I can send JSB 18's at 935 into a rough hold at 50 yards (Airwolf MCT w/LW match barrel). At that power level the 16's are around 1010 fps and don't group well and the 13s at 1100+ fps are worse. I need to drop the energy down to around 30 ft/lbs to get the 16's back down to 920 fps to tighten the group back to single rough hole.

Seeing as you are having trouble with both barrels it may just be that you need to spend more time shooting it to learn the proper technique for that gun. Maybe the way you hold it or support it on the bench needs some adjusting. I was having problems with my RAW HM1000x.25 at first. Was only getting 3/4 to 1" groups at 50 yds. Turn out that I was resting the bottle in the bench rest saddle and the gun did not like that. As soon as I moved the rest back onto the stock behind the bottle suddenly started shooting 5/16" to 1/2" at 50. Made all the difference. Unfortunately it took me a couple weeks of trying different pellets etc. ect. before I figured that out.

This thread died with no resolve posted.



i was watching a video from an interview at the FX Factory in Sweden, and they say that every gun is tested to shoot MOA or better at 50 yards.

The OP never said whether or not he cleaned the barrel. I find these accuracy issues very surprising if the OP is doing his part.

I know this is an old thread. But I recently started studying FX Airguns, and they seem to really be determined to put out a premium product. So something really sounds strange to me about this thread.