Over the years (decades actually), I have tested literally hundreds of barrels, most of which were .177, followed by .22, and maybe a dozen .25cal, and only a handful of larger ones. Nearly all testing was for reliable precision with the best commonly available diabolo style pellets (not much testing with slugs). A large percentage of my testing during the last 20 plus years consisted of benchtesting in my 51yd tunnel, followed by outdoor testing of good candidates from both bench and field target positions.
Prior to the introduction of the JSB pellets, The best pellets were a few offerings from H&N, and the brown folding boxed Crosman Premier pellets. Of all calibers when used in Korean 707 barrels, BSA airgun barrels, and Weihrauch barrel blanks as made for HW35 export rifles .
My fave for consistent accuracy for field target use was the HW .177 blank shooting lubed 10.5 Crosman Premiers at around 880fps until the entry of the fine 8.4gr JSB pellets (thankfully introduced about the time “Good lots” of Crosman premiers were nearly gone). I was never really happy with HW barrels for 12fpe shooting in my USFT guns, though they did well in HW breakbarreled rifles with 7.9 premiers for sure.
As I tested the JSB more thoroughly, it seemed they bucked wind better than (good) Crossmans, but were not more accurate at under 50yds in my guns, but either could deliver sub-moa results with consistency in my guns with no wind.
But back to barrels! I soon learned barrels must be prepped properly to give good results, and there was normally a broad range of performance from factory prepped barrels of the same brand and model, especially in precharged guns! I my experience MOST factory precharged guns deliver between 2 and 5 moa groupings from fifty yards. I also learned that I could improve grouping of all but the very best barrels with a bit of rework, but that even new never used barrel blanks from the same batch vary enough that careful, identical prepping still shows at least one in ten to be great and one in ten to be somewhat mediocre.
But for now, my goto combo is the .177 slow twist poly barrel (esp in stainless) used with 10.34 jsb Pellets. I much prefer the slow twist, esp at lower speeds, but I have also seen equally good results with a couple standard twist poly barrels as well, esp at above 18fpe.
I have never personally seen a 5mm barrel deliver better accuracy indoors or out in a precharged rifle.
The above said, really extreme precision isnt really a prerequisite for Field Target, although many judge use of certain rifle or barrel makers as proof of superiority. I still feel that any barrel/pellet combo that can deliver sub moa 10 shot groups as often as not at 50yds can win any FT match if used by a great shooter, and MOST events can be won with 1.5 moa level precision.
Sincerely,
L.D.
. And I got lucky and held solid for ten more shots and two gun swaps. 