I enjoy modest power (below 50 fpe) airguns and pellets for most of my shooting but a strong curiosity about slugs has had me investing in a couple of PCPs specifically for them.
I'm trying to figure out what makes finding the right slug and getting consistent groups so elusive when the powder burner guys can buy any off the shelf ammunition (let's just call them "bullets") and expect reasonably good results.
In looking at the problem I strongly suspect that slugs face alignment challenges that bullets don't.
A bullet, mounted in its cartridge is accurately aligned to the case and seated to a standard depth so that when it's chambered it is in the optimal position (relative to the rifling) and orientation to be fired down the (unchoked) barrel. Bullets are typically quite long relative to their diameter which benefits them both in the bore and in flight. The huge amount of energy/pressure available has no problem forcing a tight fitting, well sealed bullet down the bore.
An airgun slug has no "support system" and must rely on the probe and the magazine to chamber it straight and position it relative to the rifling.
Considering that each brand and weight of slug has a different length, the type of the base (flat, dished or boat-tailed) and the design of the probe will affect how the slug seats in the breech relative to the rifling and transfer port. I think an adjustable probe might be useful to have.
The shape of the slug and it's length (short and pointy versus a long cylinder) would influence how easily it could be misaligned while being chambered.
Airgun bore size and consistency and finding the exact correct diameter of slug to achieve a good seal without excessive friction is an other variable to consider.
Then there's choked or unchoked barrels and rifling twist rate considerations... or some sort of compromise for PCPs that are pellet/slug dual purpose airguns.
After all the mechanical considerations there's the tuning for optimum velocity and harmonics.
Are we having fun yet?
So if we look at worst case and take a short pointed slug, abuse it in the magazine; mis-feed it so it engages the rifling cockeyed and compromises the sealing; fire it down the bore to be extruded through the choke and launch it into the world in a blast of over-powered turbulent air, are we really surprised that it takes the slug many yards of erratic flight to sort itself out?
But man, is it ever beautiful when we get everything right and stable flight and sub-MOA groups happen!
Anyway, just food for thought. Please feel free to ignore me or to add you own theories.
Here is a link to a video about magazines mis-feeding pellets that probably applies to slugs as well.
Cheers!
I'm trying to figure out what makes finding the right slug and getting consistent groups so elusive when the powder burner guys can buy any off the shelf ammunition (let's just call them "bullets") and expect reasonably good results.
In looking at the problem I strongly suspect that slugs face alignment challenges that bullets don't.
A bullet, mounted in its cartridge is accurately aligned to the case and seated to a standard depth so that when it's chambered it is in the optimal position (relative to the rifling) and orientation to be fired down the (unchoked) barrel. Bullets are typically quite long relative to their diameter which benefits them both in the bore and in flight. The huge amount of energy/pressure available has no problem forcing a tight fitting, well sealed bullet down the bore.
An airgun slug has no "support system" and must rely on the probe and the magazine to chamber it straight and position it relative to the rifling.
Considering that each brand and weight of slug has a different length, the type of the base (flat, dished or boat-tailed) and the design of the probe will affect how the slug seats in the breech relative to the rifling and transfer port. I think an adjustable probe might be useful to have.
The shape of the slug and it's length (short and pointy versus a long cylinder) would influence how easily it could be misaligned while being chambered.
Airgun bore size and consistency and finding the exact correct diameter of slug to achieve a good seal without excessive friction is an other variable to consider.
Then there's choked or unchoked barrels and rifling twist rate considerations... or some sort of compromise for PCPs that are pellet/slug dual purpose airguns.
After all the mechanical considerations there's the tuning for optimum velocity and harmonics.
Are we having fun yet?
So if we look at worst case and take a short pointed slug, abuse it in the magazine; mis-feed it so it engages the rifling cockeyed and compromises the sealing; fire it down the bore to be extruded through the choke and launch it into the world in a blast of over-powered turbulent air, are we really surprised that it takes the slug many yards of erratic flight to sort itself out?
But man, is it ever beautiful when we get everything right and stable flight and sub-MOA groups happen!
Anyway, just food for thought. Please feel free to ignore me or to add you own theories.
Here is a link to a video about magazines mis-feeding pellets that probably applies to slugs as well.
Cheers!
at least if your hammer sucks to change or you hate re zeroing your scope after a barrel change.