Air Gun Home :: View topic - Barrel Re-Crowning

Alstone · Moderator & Site Supporter

Went I got my B4 and after giving it a clean and lube it was shooting 10mm groups at 10m, using Hobbys, my other favorite pellet is Bisley Practice wouldn't group at all.
Anyway a few days later while investigating a drop in power, which was a lose screw holding the piston seal in place, I decided to re-crown the barrel this I did in the lathe.
After re-asembling the gun and testing, it was all over the place using Hobbys, but when I tried Bisleys it was back to grouping at 10mm at 10m range.
Any sugestions as to what caused it to favour a diffrent pellet after a re-crown ?

Al

AirGunEric · Site Admin

Well, the re-crown changed the layout somewhat- so what was good before obviously changed too. Sometimes makes me wonder though what some pellets are doing in a particular airgun- I had thought that it really came down to how the pellet is fitting the rifling in a particular barrel- but obviously you didn't change the whole barrel and the Hobby's changed their performance drastically for the worse, while the Bisley's improved significantly.

Perhaps- different crown angles/cuts can affect different pellets in different ways- i.e. another one of these "figure out which crown cut/angle works with each pellet". Perhaps this is why pellet experimentation on an airgun is as it is- but I know I was attributing this issue more on a barrel's size/tolerances and rifling than on the crown itself.

If I had the equipment to make precise angled cuts and a pile of barrels for a specific airgun, I would experiment to get an idea if I'm barking up the right tree here- but no matter.

Alstone · Moderator & Site Supporter

Hi Eric
The only thing I can Think of is that Hobbys are a tighter fitt in the barrel, and I cut the recrown at 45 Deg, so I reckon that a tight fitting pellet can overcome a bad crown to a certain extent.

Al