Effect of Air Pistol Barrel Length on Intrinsic Accuracy?

[sparky]

First, this is *not* about sight radius, balance, comfort, or weight.
I repeat, this is *not* about sight radius, balance, comfort, or weight.

Has anyone determined the effect of barrel length on air pistol accuracy?
In particular, what is the minimum length of rifling needed to stabilize a pellet to achieve maximum accuracy at a range of 10m?

[SamEEE]

There are more factors at play than just length.

... that's also what she said.

Pressure curve differential pattern released by the regulator - wasted energy if long impulse. Tuned to barrel length. Fast powder vs. slow powder metaphor. Apparently airgun barrels are also choked.

[sparky]

There are more factors at play than just length.

... that's also what she said.

Pressure curve differential pattern released by the regulator - wasted energy if long impulse. Tuned to barrel length. Fast powder vs. slow powder metaphor. Apparently airgun barrels are also choked.

Hmm...hadn't thought of pressure curve of air release as a factor. Didn't know airgun barrels are choked...really? How much?

Here's my thinking: As pellets travel at a relatively slow velocity, any extra time in the barrel beyond the minimum needed to stabilize the pellet is time where the shooter's movements can affect the path of the pellet. Thus, it would be ideal to have the shortest barrel possible, with a bloop tube/compensator-like extension to mount the front sight.

[Rover]

I think I'll sit this one out.

[kevinweiho]

Here's my thinking: As pellets travel at a relatively slow velocity, any extra time in the barrel beyond the minimum needed to stabilize the pellet is time where the shooter's movements can affect the path of the pellet. Thus, it would be ideal to have the shortest barrel possible, with a bloop tube/compensator-like extension to mount the front sight.

Short barrels within a longer hollow tube are used in match air rifles with great success to reduce the “lock time”. I think it would be a good idea to use the same concept to offset the arc movement of short barreled air pistols.

[Gwhite]

I would think you would need to place a compensator/air-stripper at the end of the rifled section to avoid disturbing the flight down the bloop tube with turbulence.

The "short/compact" air pistols certainly have fairly short barrels, and still produce tight one hole groups on their test targets. The barrel on a compact LP-50 is only about 18cm (7 inches) long.

[Andre]

If you cut your barrel down, do it from the breach end to not destroy factory crown and choke (if any).

[j-team]

My experience in machine rest testing shows that Steyr Compact is not as accurate as the full length version. But, the difference is so small that unless you can shoot 600 you will not notice it. Both lengths comfortably shoot the X ring out!

My advice is choose the barrel length that suits your preferred balance and sight radius and don't worry about it's grouping capability. It's much like the often debated pellet choice thing, fun to talk about and interesting to test, but don't expect it to change how good a shooter you are.

[Rover]

"If you cut your barrel down, do it from the breach end to not destroy factory crown and choke (if any)."

That leaves you with the problem of opening the rear of the barrel so you can insert a pellet.

Don't believe me? Try to insert a pellet in the muzzle of your gun.

So much for the guys who think they can determine the proper pellet diameter by how tightly it fits in the breech.

[sparky]

Here's my thinking: As pellets travel at a relatively slow velocity, any extra time in the barrel beyond the minimum needed to stabilize the pellet is time where the shooter's movements can affect the path of the pellet. Thus, it would be ideal to have the shortest barrel possible, with a bloop tube/compensator-like extension to mount the front sight.

Short barrels within a longer hollow tube are used in match air rifles with great success to reduce the “lock time”. I think it would be a good idea to use the same concept to offset the arc movement of short barreled air pistols.

That's pretty much what I had in mind. I got the idea when I saw an air rifle bloop tube for sale. Might not do anything for a guy like me who shoots shotgun pattern-like groups, but for a top level guy, I think the concept has merit. Certainly as much as the silly canted sights on the new Steyr LP10 Evo.

[j-team]

Short barrels within a longer hollow tube are used in match air rifles with great success to reduce the “lock time”. I think it would be a good idea to use the same concept to offset the arc movement of short barreled air pistols.

To be honest, if you worry about "lock time" on a pistol, then you need to change your technique. Pistol shooting isn't about seeing the picture you want and quickly slapping the trigger, it's about holding an area and squeezing.

Have you ever seen a top class shooter shooting a muzzle loading pistol? Even with a lock time that can be timed with a sundial they can shoot the middle out of the target.

[kevinweiho]

Short barrels within a longer hollow tube are used in match air rifles with great success to reduce the “lock time”. I think it would be a good idea to use the same concept to offset the arc movement of short barreled air pistols.

To be honest, if you worry about "lock time" on a pistol, then you need to change your technique. Pistol shooting isn't about seeing the picture you want and quickly slapping the trigger, it's about holding an area and squeezing.

Have you ever seen a top class shooter shooting a muzzle loading pistol? Even with a lock time that can be timed with a sundial they can shoot the middle out of the target.

I don’t worry about lock time, but I do appreciate pistols that have a faster lock time. I already know that to be proficient in pistol shooting, you have to master the “follow through”. It’s not only about holding an area and slowly squeezing the trigger.

No, I’ve never seen in the flesh, a person shooting a muzzle loading pistol. I do know that muzzle loaders have a slower lock time than their centerfire/rimfire counterparts.

[william]

Following Rover's wise counsel, I was going to sit this one out as well. But enough is enough.

Attention, people: Lock time describes the delay between sear release and ignition (release of gas in an AP or AR). To my knowledge the only recent effort to address lock time in an air device is Cesare's innovation in the Matchguns MGH1, and it has nothing at all to do with barrel length. If you want to discuss barrel time, please say so.

As to the original question, I'll follow Rover's lead.

[Andre]

"If you cut your barrel down, do it from the breach end to not destroy factory crown and choke (if any)."

That leaves you with the problem of opening the rear of the barrel so you can insert a pellet.

Don't believe me? Try to insert a pellet in the muzzle of your gun.

So much for the guys who think they can determine the proper pellet diameter by how tightly it fits in the breech.

To cut a barrel down you have two choices,

From the muzzle: requiring a new crown to be cut and choke lapped (leaving the bore oversize a few ten-thousandths, maybe requiring a larger in diameter pellet)

From the breach: requiring a new lead in. This can be done many ways, on the lathe preferably but could even be done with a dremel tool with cotton buff and light lapping compound.

Of course you could always cut a section out in the middle and weld the two halves back together!

[Brian Girling]

Slightly off topic.

Back in the late 60s or early 70s I was fortunate enough to be on the same flight as Pat Whately who was a director of Webley & Scott Ltd. He told me that the THEORETICAL PERFECT BARREL for a .22lr pistol was 1 metre diameter and 1 metre long !!, whereas the PRACTICAL PERFECT BARREL was 9.5 inches long (I think) and tapered which coincidentally was the size of the Webley & Scott single shot target pistol many of which were modified in the UK for use as free pistols.

Pat went into the theory of pressure curves, shock waves, velocity, mechanical properties of the steel and a load of other factors the overriding one being the NUT ON THE BUTT.

[sparky]

Following Rover's wise counsel, I was going to sit this one out as well. But enough is enough.

Attention, people: Lock time describes the delay between sear release and ignition (release of gas in an AP or AR). To my knowledge the only recent effort to address lock time in an air device is Cesare's innovation in the Matchguns MGH1, and it has nothing at all to do with barrel length. If you want to discuss barrel time, please say so.

As to the original question, I'll follow Rover's lead.

I don't get the whole "sitting out thing"...has this been discussed before? I didn't see anything on it when I did a search.

[David M]

The answer is simple...
Buy a new Airpistol, mount it in a machine rest and test it.
Cut off 1" of barrel and retest.
Keep cutting and testing till you get to a barrel 1" left.
Publish your results.
Then buy a new barrel, fit it to your gun and just go shoot......

[william]

I don't get the whole "sitting out thing"...has this been discussed before? I didn't see anything on it when I did a search.

Speaking only for myself, the whole exercise is silly, angels dancing on the head of a pin - what Mr. Jackson, my 10th grade history teacher (55 years ago), used to call "mental masturbation."

I like David's approach:
"The answer is simple...
Buy a new Airpistol, mount it in a machine rest and test it.
Cut off 1" of barrel and retest.
Keep cutting and testing till you get to a barrel 1" left.
Publish your results.
Then buy a new barrel, fit it to your gun and just go shoot......"

I"d change the last step to:
Sell the remains of your pistol; take up the trombone. Then you can waste your time determining precisely how many Hertz sharp or flat result from every .001" movement of the slide.

[OTD]

It’s not about performance form the machine, it’s about human speed vs speed of an AP action, as far as I understand it, but still, it really is a „mental masturbation“.
The time it takes to accelerate the pellet form the chamber to the muzzle or to reach Vo can be calculated. It’s between 3/1000 and 4/1000 of a second. That’s 100 times faster than a natural blink of the eye. The pellet has left the barrel long before the trigger has reached the stop. If human reaction time would be as significant as some imagine, then a pellet shot from an LP10 would constantly collide with the compensator cone.

[Rover]

Well, OTD got it in one!

I'm glad I didn't bother with this one.