Looking down barrels

[mav72]

Ok, I've been doing some barrel cleaning of some of my my older airguns. My pellet only guns look great with nice deep rifling.

Though I don't shoot steel bbs through them, I see a lot of variation among my dual ammo barrels. I have a Crosman 66 and a 766 from the early 80s that have fairly prominent rifling that looks as good as the rifling in my new Legacy 1000. These shoot really well so no questions there.

I have another early 90s 66 in which the rifle twist looks minimal. The rifling looks like a streatched "S" down the barrel. Was this supposed to be better for bbs or something? It's pretty odd looking. Shoots pellets ok. Not great. Never tried bbs. Maybe, I shuld try it with lead bbs.

So next I have these two guns that are very accurate but looking down the barrel would tell me that they shouldn't be. One's a 90s Daisy 880 that I got new and has never seen bbs. The other is an early 80s Crosman 760. I can see the rifling but there isn't the sharp lands and grooves that I'm use to seeing. So, is there a way to tell if these dual ammo barrels are bad by just looking through them? Or do you just have to shoot and see how they perform?

[the fuse]

My two cents. You just have to shoot them to tell how they react. Obviously a quality German rifled barrel is going to be more accurate than a cheapo 760 rifled barrel. That doesn't mean a dual ammo rifled barrel can't be pretty accurate as well. Finding out is all part of the fun. 

[BrushPopper]

I’ve seen this referred to as the “Barrel Lottery”.
I’ve seen crummy rifling in barrels of all ages, and from all over the world. All tooling wears out, it’s poor machining practice to continue using dull/worn tooling.

As Fuse has observed, shooting for groups is the only true test. Seen crappy-looking barrels shoot excellent groups, though in my experience, this is an exception.

[johnnyfoos]

Looking down barrels?
Well, I like to use my "Endoscope camera"
for doing that.
But back then I got mine they didn't have any small enough for .177
I did find one that is 5.5mm
And it was kind of a pain to get to work with my android stuff but wasn't as hard for a cpu.

just my
$0.02

[BigBird]

I think rifling really depends on the contact with the pellet/bullet.  Barrels all look different with different lands/grooves.  The cool thing about air rifles is we are using lead which conforms to the grooves easier than copper jacketed firearm bullets.  Probably the variation that is most critical you may not see looking down the barrel might be the diameter of the bore at the lands.  That would be where the head of the pellet rides.  Then there are the muzzle crown and leade.

For WWII the US rebarrelled many of the reserve 1917 Enfields from WWI.  Some of the barrels were Johnson 2 groove barrels.  GIs looked down the barrels and thought the same thing, this thing couldnt possibly be accurate with this rifling but they proved to be just as accurate as the other 4 and 5 groove.


However, perception is reality.

[mav72]

Thanks for the info. I'll look into it.

Interesting... My 66 barrel kind of looks like the pic. It has five grooves but isn't a tight twist. It kind of confused me because it looks WAY different from my other airgun barrels.

On my 760 and 880, You can see the swirl of the rifling but it's not defined. They both shoot pretty well too. Thought they were just dirty at first.