I have been attempting to shoot the Aguila Super Colibri CB ammo in my 1960ish 39A. It seemed erratic so I took it to the range so that I could fire Remington high speed .22 LR to ensure the scope/gun was ok. The high speed ammo grouped at an inch at 50 yards. The CB ammo grouped about 7 inches at 50 yards which is unacceptable. The dispersion was mostly horizontal.

Does anyone have any suggestions about what could be the problem? The CB ammo was hand placed in the chamber to avoid any deformation that might be caused by cycling the action.

I've never tried Aguila ammo, but I've always heard it doesn't shoot well at all.

OK, thanks guys. I'll purchase some CCI subs which is what I used to shoot and, indeed, it shot well. I decided to try the Aguila because velocity is lower, projo weighed less, and it is quieter.

You are comparing two very different rounds. The Super Colibri has no gunpowder in it and is designed for extremely close range use. With only 500 FPS with a 20-gr bullet, I see no reason to fault it for 7" groups at 50 yards.

CCI Subsonics (1050 FPS with a 40-gr bullet) are excellent rounds of course, in a completely different type of .22 ammo. They are very good for target shooting at 50 yards, as are Aguila Subsonic .22s (1025 FPS), which means CowboyGunNut can't say "always heard it doesn't shoot well" anymore.

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I have much better luck with CCI CB Longs than I do with Colibris in my rifles as well. They are perfect for back yard squirrel duty. I just could not seem to hit what I was aiming at with the Colibris. I also had one get stuck in the bore of my CZ Lux, but no such issue with CCI, and they are just as quiet IMO.

My 1958 Benjamin pellet gun is about as accurate with only an 8 grain projectile. I should have added that I was going back to the CCI CB ammo rather than the CCI subs. Didn't realize CCI made subsonic .22 ammo other than the CB.

I chronographed my 2000ish 39A what I found out was that it's longer barrel shot slowere with all ammo than my Browning Pump 22 did.

I'm guessing that that long of a barrel is causing the 22 Colibri to really slow down and tumble.

50 yards is a real stretch for Super Colibris. That would be like shooting at 300 yards with a .38 Special or 1000 yards with a .45/70. I have found the Super Colibri's group o.k. at 10 or 15 yards, around 3/4" or slightly less, better groups than I've gotten with CCI CB's. All rifles are different, some might like the CCI CB's better.Neither round will do near as well as a good L.R. subsonic, at any range. Also don't know if I'd shoot them in a 24' barrel like the M39A, some people have had them stick in the bore. They are meant for handgun length barrels, I believe there is a warning on the box to that effect. I usually shoot them with a CZ 452 Scout with a 16" barrel, and have had no problems.

I agree that 50 yards is very long range for CB caps of any brand.
One caution when using cb caps in a rifle: my Dad used Super Colibi's in his 50's era 39A (24 inch barrel). One round never exited the muzzle. Fortunately he noticed no hole in the target and checked. The bullet was lodged in the bore and was easily pushed out with a cleaning rod- no damage.
24 inches of barrel may be too much friction for a bullet powered only with priming compound.