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Do we need to rethink our pellets to move airguns on?

PUBLISHED: 12:07 03 January 2019 | UPDATED: 12:07 03 January 2019

FX Airguns are developing special barrels to work with slugs which is very interesting

FX Airguns are developing special barrels to work with slugs which is very interesting

Archant

"I strive for a clean kill every time, and I wondered if the slugs might help me to knock these tough animals down humanely, even if my shot placement is imperfect."

I’ve been fascinated by airgun pellets ever since I began shooting, always hoping that I was about to find the next step forward in performance. In recent times, I think it’s fair to say that most experienced hunters have converged on the use of high-quality, round-head pellets as the ones that offer optimum performance. They’re usually most accurate, fly flattest and are least disturbed by the wind, so is that the end of the quest for the ultimate pellet? Maybe not.

I’ve seen some very interesting YouTube videos created by a South African airgun hunter, Matt Dubber, who is experimenting with what he calls ‘slugs’, but what I’d call ‘bullets’. They’re made in America by Nielsen Speciality Ammo (NSA) although Matt makes his own in South Africa because he has difficulties importing them. As you can see in the photos, they’re shaped like a short rifle bullet and feature a deep nose cavity to create expansion on contact with our quarry.

Because they’re made from pure lead, they should expand much better than diablo pellets, which use lead alloyed with antimony to make the metal stiffer. This helps them survive being transported in the tin from the factory to your gun shop. The pure lead also reduces friction in the barrel compared to harder alloys. It’s fair to say, they they’re really only suited to high-power rifles and that at 12 ft.lbs. the conventional pellet remains superior.

Parallel-sided

I managed to secure a small supply of 21grain NSA slugs in .217” diameter to test through my 29 ft.lbs. Daystate, which uses a Lothar Walther barrel that’s choked. I kept my testing to a minimum to reserve a small quantity to try on the squirrels later after the leaves come down. At 21 grains they’re considerably heavier than my usual 16 grain Air Arms Field Diablo, which means that instead of my chosen 900fps, the NSA slugs start at 730fps – a huge difference. It’s also a big drop in muzzle energy at just under 25 ft.lbs. It seems likely that the parallel-sided slug suffers more barrel friction than the thin contact areas of a pellet, which would explain the loss of power.

One of the most compelling reasons to use a high-power airgun is the flatter trajectory, so I needed to see what the difference would be. In the slug’s favour is a massively better ballistic coefficient (BC) 0.073, which should recover something of the velocity loss. After feeding this data into Chairgun, I saw that the PBR for the Air Arms pellet is 10.2 to 47.4 yards while the NSA slug offers 8.7 to 41.9yards. My PBR is the zone in the trajectory within which the pellet is no more than ½” above or below the sight line and the longer it is the better.

The high BC also promises better performance in the wind, so again I asked Chairgun for some answers. In a 5mph 90̊ cross wind, the Air Arms pellet would be deflected 3.76” at 50 yards whilst the NSA slug was just 1.6” despite travelling much slower at the muzzle. In fact, the flight time of the slug was just 0.027 seconds slower, despite the huge difference to begin. The NSA slug also hits with 2¾ ft.lbs. more energy, so we can see that there are plenty of factors to consider when comparing the two.

Of course, the slugs needed to be as accurate as the pellet to be worthy of consideration, and time at the range showed that at 35 yards they could indeed match the diablo, so I set that as my maximum hunting distance.

Expansion

I was champing at the bit to see if the slug would A, expand, and B, deliver reduced penetration, so I shot a pellet and a slug into a block of ballistic gel at 25 yards. The pellet penetrated some 8” whilst the slug stopped at 6”. This suggests that the slug will fly straight through my quarry just like pellets do, but the question is, will it do more damage in the passing? The pellet showed no measurable expansion, but the slug had indeed expanded to just over 0.234”and the tiny nose cavity had become as wide as the slug. All very promising, but it had achieved that expansion over 6”, whereas our quarry is probably less than 2” wide.

Over the winter I shoot a huge number of squirrels and, now and then, I find myself needing to use a second shot to finish the job, which is not what I want. I strive for a clean kill every time, and I wondered if the slugs might help me to knock these tough animals down humanely, even if my shot placement is imperfect. Of course, accurate shooting is the most important factor in this, but high striking energy and superior energy transfer could help. The only way I’ll know the truth is to keep enough slugs to re-zero the rifle precisely, and take some quarry to see if a difference can be seen in real-world conditions.

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