As beerthief mentioned, shortning a barrel on a break barrel springer is an option. The owner of Pomona Airguns (Steve) can chop and choke a barrel. I just called to verify that he is still in business since he moved in 2021 from Calif to Nev (
https://www.pomona-airguns.com ). Steve did say he only has 3 setups to choke barrels so if you want it choked it will need to fit one of those setups.
Many years ago when PCP's were just becoming popular, there was discussion about how long a barrel needed to be. The thoughts on this matter was roughly that the compression area only had a given capacity to hold air and the barrel also had a given capacity to hold the air pushed into it before a pellet left the barrel. Of course other factors are also involved but the idea was that a barrel too long or too short would affect the performance. Add to that that most barrels are press fit into the breach which reduced the diameter somewhat. Push a pellet thru the barrel from the breach and it usually had less resistance once it passed the breach area. After the pellet was past the breach if it was a loose fit at the muzzle, accuracy may be hindered. A choke at the muzzle will reduce the diameter enough to feel as the pellet is pushed out.
My hands down favorite springer is an R9 with a chopped and choked barrel in 177 by Steve around 14" long. It seemed better balanced to me and I didn't see much change in velocity but accuracy did improve. Most of my use with that gun is hunting ground squirrels shooting offhand or sitting. One of the few times I've shot off a bench at 50yard on the BLM land with a slight breeze using JSB 8.4 gave me a 6 shot group of 1 3/8" but taking shot # 4 out resulted in 7/8" back in 2019.
I bought a 22cal R9 barrel chopped and choked to 8" second hand (can't say who did it but understand two parties were involved). It took all my strength to simply cock that thing and I ended up putting a shroud on it to make cocking possible. Velocity was around 80fps less than a standard carbine barrel but it's accurate.
I did get into PCP's after Benjamin introduced the Maurader and dove into the deep end for many years. I recently gave my stepsons all the PCP gear and guns I own due to health issues but kept the springers.
Good luck on your quest..
