Hello AGN members, You may shoot slugs out of your traditional pcp’s with good results but that’s just not right. Here's why.
This is a LW barrel blank found in majority of the PCP's - Airgun Blank CHOKED - Twist:17.7" | .22 air | OD:.39" | L:23.82" | precision rifle steel tube | Airgun barrels | Gun barrel blanks | Lothar Walther gun and rifle barrels online shop - USA (lothar-walther.com)
The bore measures 5.46 mm (0.215), while the groove is slightly larger at 5.62 mm (0.221).
So,
If you're using a 0.216 projectile for the subject matter, you should achieve satisfactory groupings at a distance of 50 yards. I corroborated this information on a random forum among Umarex Origin / Avenger owners, and they confirmed the same. The user group was for 25 cal, but outcome is related to any caliber under 0.357.
There is absolutely nothing wrong. In what they have experienced. As seen in the video made by STKO here
But,
For a trained eye, those aint flyers. For many it's too good, under half inch @100yd. But the truth is, groups could be much tighter, as the group marked in Red is actually the result of the barrel's nature.
I do not wish to discuss about velocities and power, It is a separate topic discussed. It is best described here (What's The Best Slug Weight For My PCP Air Rifle? - Hard Air Magazine). I wish to discuss about the barrel construction and specifications. Twist rate is also a different topic altogether and we do have good posts here ( Velocity vs. Barrel Twist Rates | Airgun Forum | Airgun Nation | Best Airgun Site | Airgun Message Board ).
So as the topic says, Not all barrels can shoot slugs,
Here is the rational explanation. In Q&A format.
Q. So whats wrong?
A. The barrel.
A JSB pellet boasts a head diameter of 5.52 +- 0.01 mm and a skirt diameter of 5.71 +- 0.01 mm. The head fits snugly between the bore and groove, encompassing around 45% of the depth, ensuring an optimal engagement. Moreover, the skirt covers approximately 101.017% of the total barrel diameter, fully enveloping the barrel profile's extremities, creating a perfect seal and ideal head engagement. ( That’s why pellet sizers do not work if you pass the entire pellet through it)
As you fire the shot, the skirt no longer needs to expand; instead, it bulges and harnesses the charge, accelerating towards the Choke. (You can find numerous images of fired and recovered pellets online illustrating this process.) The choke measures approximately 0.012 mm less than the bore diameter or 0.0005 inches. It serves as a constant tapering section, molding the slug by pressing against the grooved contact surface and effectively swaging it into a uniform diameter.
The skirt features a meticulously engineered conical section that readily collapses and deforms with minimal effort, contributing to a highly efficient discharge. As seen in the image below.
On the other hand, the 0.216 slug is relatively loose-fitting, akin to riding the bore, resulting in numerous air passageways.
Consequently, this creates the following scenario:
I would like you to imagine how Jason Statham would say these lines.
Jokes apart, Addressing the elephant in the room,
Q But I shoot slugs well, so does it even matter?
A. Yes It does, because you are loosing a ton of power and you loose a lot of BC. And tighter groups of course.
Q. Can I shoot heavy slugs like those Youtubers?
A. Not at all in the stock gun configuration, but you may shoot a 23-grain slug with much more efficiency as compared to 23 grain pellets, you can reach farther distances, Miss less targets and save ££££.
Q. So whats the solution?
A. A barrel with revised specifications…..
Q. What are those?
A. Lets brainstorm at the AGN forum. Here.
This is a LW barrel blank found in majority of the PCP's - Airgun Blank CHOKED - Twist:17.7" | .22 air | OD:.39" | L:23.82" | precision rifle steel tube | Airgun barrels | Gun barrel blanks | Lothar Walther gun and rifle barrels online shop - USA (lothar-walther.com)
The bore measures 5.46 mm (0.215), while the groove is slightly larger at 5.62 mm (0.221).
So,
If you're using a 0.216 projectile for the subject matter, you should achieve satisfactory groupings at a distance of 50 yards. I corroborated this information on a random forum among Umarex Origin / Avenger owners, and they confirmed the same. The user group was for 25 cal, but outcome is related to any caliber under 0.357.
There is absolutely nothing wrong. In what they have experienced. As seen in the video made by STKO here
But,
For a trained eye, those aint flyers. For many it's too good, under half inch @100yd. But the truth is, groups could be much tighter, as the group marked in Red is actually the result of the barrel's nature.
I do not wish to discuss about velocities and power, It is a separate topic discussed. It is best described here (What's The Best Slug Weight For My PCP Air Rifle? - Hard Air Magazine). I wish to discuss about the barrel construction and specifications. Twist rate is also a different topic altogether and we do have good posts here ( Velocity vs. Barrel Twist Rates | Airgun Forum | Airgun Nation | Best Airgun Site | Airgun Message Board ).
So as the topic says, Not all barrels can shoot slugs,
Here is the rational explanation. In Q&A format.
Q. So whats wrong?
A. The barrel.
A JSB pellet boasts a head diameter of 5.52 +- 0.01 mm and a skirt diameter of 5.71 +- 0.01 mm. The head fits snugly between the bore and groove, encompassing around 45% of the depth, ensuring an optimal engagement. Moreover, the skirt covers approximately 101.017% of the total barrel diameter, fully enveloping the barrel profile's extremities, creating a perfect seal and ideal head engagement. ( That’s why pellet sizers do not work if you pass the entire pellet through it)
As you fire the shot, the skirt no longer needs to expand; instead, it bulges and harnesses the charge, accelerating towards the Choke. (You can find numerous images of fired and recovered pellets online illustrating this process.) The choke measures approximately 0.012 mm less than the bore diameter or 0.0005 inches. It serves as a constant tapering section, molding the slug by pressing against the grooved contact surface and effectively swaging it into a uniform diameter.
The skirt features a meticulously engineered conical section that readily collapses and deforms with minimal effort, contributing to a highly efficient discharge. As seen in the image below.
On the other hand, the 0.216 slug is relatively loose-fitting, akin to riding the bore, resulting in numerous air passageways.
Consequently, this creates the following scenario:
I would like you to imagine how Jason Statham would say these lines.
- So, you've got quite a bit of space between the groove and slug diameter, allowing the City of London to run a tube service right through it! Your air charge exceeds and exits faster than the preceding slug. What you don't realize is the amount of energy you're losing.
- Now, as you approach the choke, guess what? You've got a solid chunk that's fatter than an éclair (for the choke, at least!). There's no tail section to deform. The result is that you end up losing velocity and a fair bit of the slug to the choke.
- And finally, the grooves cut into the slug, causing you to choke your barrel with lead deposition, making it a smoothbore much sooner. Wonder why you need regular bore cleaning?
Jokes apart, Addressing the elephant in the room,
Q But I shoot slugs well, so does it even matter?
A. Yes It does, because you are loosing a ton of power and you loose a lot of BC. And tighter groups of course.
Q. Can I shoot heavy slugs like those Youtubers?
A. Not at all in the stock gun configuration, but you may shoot a 23-grain slug with much more efficiency as compared to 23 grain pellets, you can reach farther distances, Miss less targets and save ££££.
Q. So whats the solution?
A. A barrel with revised specifications…..
Q. What are those?
A. Lets brainstorm at the AGN forum. Here.
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