bent barrels on airguns

[breakfastchef]

Yes, I have had "bent" barrels but.. I have also checked the TIR (total inidcated runout) on many others and two of my Crosman guns dialed in at .001" or less across 10 and 12 inch lengths and crown to breech paralellism was just as good.

Brian: How do you measure TIR? I have several airguns in my stable that won't shoot straight, but are very accurate. Should these be checked?

[BDS]

Brian: How do you measure TIR? I have several airguns in my stable that won't shoot straight, but are very accurate. Should these be checked?

Chef: I'm lucky, I work at a Missiles & Space parts manufacturer and we have measurement devices for just about any mechanical feature, with readouts to .00000" places.

In this case, the OD of the barrel was set up on rollers (v-block type) and the dial indicator moves along the axis of the barrel at as many points or postions as you want to measure. A small motor drives the rollers at about 2-5 rpm and the barrel rotates against the indicator plunger which shows deviation in .0000". This really (only) indicates the true roundness of the OD of the barrel so , we use precision pins on the actual barrel (ID) to get TIR of ID to OD or comparison one to the other.

Sliding the indicator along the axis with the barrel stationary can also give indication of a bend or deformation.

[BDS]

Brian: How do you measure TIR? I have several airguns in my stable that won't shoot straight, but are very accurate. Should these be checked?

Realize I didn't address your main comment about your guns.

By "won't shoot straight" I assume they shoot consistently to an aimpoint but not where you want them to hit, i.e aim for 10 ring and hit 5 ring same place again and again ? If your guns are accurate and consistent, there is a greater chance of sight misalignment or dovetail misalignment to the true centerline of the barrel. Many of the Chinese and Turkish springers are notorious for this. Their grooves may be straight with the bore or barrel (i.e. parallel) but they are off centerline by .010" or more. With that condition, your scope or sights are now becoming a pivot device versus just wind & elev. compensators. The worst case are the grooves or sight mounts that are neither on centerline nor parallel, now that will make you crazy!

[breakfastchef]

Realize I didn't address your main comment about your guns.

By "won't shoot straight" I assume they shoot consistently to an aimpoint but not where you want them to hit, i.e aim for 10 ring and hit 5 ring same place again and again ?

Actually, no, they are all pretty accurate. I was just making a funny about them not shooting straight, but all capable of hitting the 10 ring consistantly.

That may be the whole point of this thread. The OP thinks all Crosman barrels are bent (I accept that) and must be straightened to shoot straight (that I cannot accept). The assumption, which goes to my attempt at humor, dictates that all my Crosman guns have bent barrels, do not shoot straight and are likely inaccurate. This is not my experience. I think most barrels probably do shoot straight, but not all are accurate either because of manufacturing defects or the way they are mounted on airguns.

[BDS]

Actually, no, they are all pretty accurate. I was just making a funny about them not shooting straight, but all capable of hitting the 10 ring consistantly.

That may be the whole point of this thread. The OP thinks all Crosman barrels are bent (I accept that) and must be straightened to shoot straight (that I cannot accept). The assumption, which goes to my attempt at humor, dictates that all my Crosman guns have bent barrels, do not shoot straight and are likely inaccurate. This is not my experience. I think most barrels probably do shoot straight, but not all are accurate either because of manufacturing defects or the way they are mounted on airguns.

Ah-hah, I was in my "serious" mode, GOT ME! 

Ya, my 2289G that I just recieved is shootin like an LW barrel and it's a Crosman thru and thru! Adjusted the leveation and (still) have not touched the windage! Luck? Maybe? and... doesn't mean that the barrel is not somehow bent either. Whatever it is, it's shootin one and two holes at 10 meters with Crosman red tin Premiers, so nothin special about the pellets either! or as they say on cable TV... "Myth Busted"