Long-range airgun benchrest observations

The BRUTAL conditions at our latest long-range benchrest competition made for some interesting retrospective observations about high-power air-rifle ballistics. However a bit of background information is required for perspective.

My local shooting club holds monthly Benchrest Silhouette competitions utilizing airgun-sized, 1/10 scale silhouettes shot at 60, 75, 90 and 100 yards (respectively) for the penny-sized chickens, mouse-sized pigs, quarter-sized turkeys (yes, at 90 yards), and rat sized rams. At my request, the Match Director agreed to include an airgun class in this RF competition. Shot from concrete bench rests in challenging outdoor wind conditions, the only shooting aids allowed are a simple sandbag under the fore-end (only). It's very challenging, especially for the airgunners (even with 100 foot-pound and .30 caliber limits).

The most successful airgun combination for this competition so far has been 34 grain, .25 caliber JSB Exact King pellets at about 900 FPS and 60 FP. The most successful RFs shoot 40 grain bullets about 1050 FPS/98 FP. Saturdays brutal winds provided interesting perspective on the exponential superiority of bullets over diabolo pellets.

Historically the (standard velocity) RFs shoot about 10-15% higher scores than the airguns in these matches; typical scores in 'normal' wind conditions being around 35 and 30 respectively (give or take about 2 points in each class). However, last Saturday we endured the most brutal windy (and cold) match conditions yet, shedding more perspective on the practical, exterior-ballistic differences between standard velocity RF bullets and high-power airguns using very high BC diabolo pellets.

The Airgun class high score in Saturdays brutal-winds competition was only 19/40, as opposed to the high RF score of 35/40. Both high scores were shot by the same experienced competitor giving his best efforts. The RF score must be considered very high for the conditions. But believe it or not (and trust me), so was the Airgun score very high given the brutal winds.

The 62% greater muzzle-energy of the .22 RF bullet is obviously quite an advantage over the (extremely-heavy) .25 pellet. However, the .035 ballistic coefficient of the pellet gives the .076 BC of the .22 bullet an almost laughable 217% advantage. Of course the BC advantage becomes ever more exponentially overwhelming the longer the range and windier the conditions.  

For poignant example, at the 100 yard ram distance the .22 bullet is still going 900 FPS and carrying over 70 foot-pounds of energy; but the extreme-power .25 caliber pellet is only clocking 640 FPS and 31 foot-pounds. Due to the shuttle-cockish ballistic coefficient of diabolo pellets, the kinetic-energy advantage of the RF bullet has grown from 62% at the muzzle to 225% at 100 yards! Kinda puts the challenge of long range airgunning into more stark perspective, huh?

"It ain't for ever'body"... but everybody is invited. I'll try to attach details, and hope the attachment doesn't overwhelm site space. 

Thank you for the well explained and articulated write-up, Ron. On the day, this event was brutal but still very fun. It opened my eyes to the fact that I am not amply versed at doping for wind. I would say in fact that I suck at it  ?. 

BTW folks, Ron won both of rimfire and airgun class events handedly in these difficult conditions. Congrats again, Ron. Awesome shooting bud!

Well written Ron. The AG community has spent a zillion dollars trying to make pcps shoot like the venerable .22 RF.

I'd like to point out the beauty of diabolo pellets is the fact they don't carry nearly as far as a RF, so can be used in more confined or settled areas. A huge part of the allure and practicality of pellet guns is their limited ranging ability.

From what I've seen on airgun forums, very powerful slug-shooting airguns can reach out to previously unheard of airgun distances, accurately BTW. So I consider them a different animal than pellet guns (as we generally know them).

I consider 100 yards to be extreme range for diabolo (pellet) guns, and have no worries about errant pellets reaching my neighbors 1/4 mile away (I don't shoot above the tree/brush-line). Even my powerful .25 Kalibrgun Cricket is a virtual non-issue beyond a couple-hundred yards. 

Nevertheless I do enjoy pushing diabolo pellet range limits... worry free.

BTW Will, that AR6 pistol you modded for me is GREAT. It averages 1.25" six-shot groups at 50 yards, and the best six-shot group at 50 yards with 18.1 JSBs measured .65” c-t-c.

Thanks for the nice feedback, DW.
    

Ron,

Reading your detailed post about this great challenge for air rifles, I am impressed again.  I have planned to drive up there from Houston after reading a previous one.

I would like to shoot a similar match in Houston.   Our guys are all shooting .177 rifles.  A handicap I suppose against your .25.

For a .177 rifle, what do you think would be a good challenge distance.    We are also shooting an el cheapo at spinners at 50 yards with the .177 Guantlet at less than $275.00 cost.   A one inch is offers a high percentage of hits.   On occasion we can hit a chicken at 60 yards.

I remember how well you did with an el cheapo rifle in silhouette at Centerville.

"Keep em' in the middle"

Bob Zimmerman

Hi Bob,

Operating on the premise a super-heavy .177 pellet with a high ballistic coefficient might do well to 100 yards, a couple times in the past I've explored that assumption with very powerful .177 PCPs capable of shooting a 16 grain .177 about 900 FPS/30 foot-pounds. Though that combination was very accurate at 50 yards, including posting THE best (single) five-shot group I've ever gotten at 50 yards (.17" center-to-center), unlike my .22 and .25 caliber results, 100 yard accuracy was not proportional to 50 yard results with the .177. In fact my 100 yard results were disappointing enough to abandon the project. As taken from my testing notes of a .177 Shin Sung Career shooting 16 grain pellets about 900 FPS/30 FP-

1/21/07- Fifteen consecutive five-shot groups at 50 yards averaged .62”. The best group measured .17” c-t-c (the smallest 50 yard group in all my airgun testing!).

Unfortunately 100 yard groups with that set-up averaged 1.5 - 2".

Besides the B.C. difference of about .030 for the .177 versus about .045 for a super-heavy (34 grain) .25, I think the muzzle energy difference of 30 foot-pounds versus 60 has a lot to do with 100 yards being "a bridge too far" for .177s. Though a .22 falls between the .177 and .25, .22 is enough closer to .25 to still do well at 100 yards.

Point is, in my opinion any range beyond the maximum field-target distance of 55 yards qualifies as extreme range for a .177; certainly with .177s maxing out about 20 foot-pounds. Of course shooting off a bench-rest would be less challenging than from FT positions, so would in itself call for longer ranges than field target. Nevertheless, I'd think maximum ranges should be no more than 75 yards with a 20 FP .177; probably 60-70 would be more realistic and still plenty challenging.

You won't really know until you get started, and should expect to evolve the distances as required. For instance, when the RF scores hit 38/40 and the airgun score 34/40 in our matches, the MD increased the pig, chicken and turkey distances from 50, 60 and 75 yards to 60, 75 and 90 yards to avoid perfect scores. It worked!

Good luck with your competition. Keep me/us posted.  

Thanks for the info.

Ask AZ about the 32ftlb .177 spitting Eun Jins from a customized Daystate. He can tell the story much better than I ever could

Hey all. I'm asking advice; but here to tell you if targets are your thing, there's no reason you can't reach out to 175-200 yards with JSB .22's & .25's. No, I'm NOT saying small game or anything else except dry dirt/sand berm, card stock printer paper (thick & cheap) cardboard or any HVAC type sheet metal. Heck yes there's a ton of drop and reading heat wave, leaves, wind on skin all adds up to experience. I've done this with 25.4 JSB .25's@44.69ftlbs down to 18.13JSB .22's @28ftlbs. Even 20ftlbs & JSB .22 15.90's reach to 125-150 accurately enough for you to gain experience of wind, follow through, trigger feel & timing in lauls in wind. If you have a safe long distance the Diabolo is perfect for this & makes more sense to use air guns then shoot a .22LR up into a tree at a Squirrel. Compare a 200yrd air gun shot with most Centerfires at 800-1000yrds. Now the question for the experts.

  At this time w/ heavy .22's & .25's variable twist rates, etc. What's top dog still for accuracy, Thomas?

  I plan on getting a Jager 17" .30 & a RAW .357, maybe a .257 if someone makes a 1000cc CF tank as Doug was hitting eggs @ 400yrds w/ 87 Brainerd from a 22lb BR stocked Air Force platform. I digress.

Plain question: what Diabolo has the highest BC in .22 & .25?

Far as I know, the 33.95 grain JSB's have the highest B.C.s in both .22 and .25 caliber, but there may be pellets out there I'm not familiar with. True confessions- I've become a JSB man almost exclusively.

When I heard they'd brought out .22s also weighing the same 33.95 grains as their phenomenal .25s, since the .22s have even higher BCs, I tried them in a couple powerful .22 Korean rifles but was very disappointed with the accuracy. After testing and testing and testing both those rifles with progressively lighter pellets, both found their groove with 18.13 JSBs; the Career at 905 FPS and the Sumatra at 985 FPS (surprisingly).

In STILL winds, both Korean .22s average 1.25 to 1.4" five-shot groups at 100 yards with the 18.13 JSBs; same as my .25 Kalibrgun Cricket bullpup shooting 33.95 JSBs at 915 FPS. But (of course) in any amount of wind condition, the .25 Cricket does much better.

I guess there are now redesigned 33.95 grain .22 JSBs, but I have yet to hear of any impressive accuracy results with them (original or redesigned).   

Thank you for your well written post. For a long while, I have been considering on shifting to slugs, or bullets, however they are called.

I do serious Benchrest activity with airguns. And the evidence of superiority of bullets over the diabolo as a projectile is very evident if we only care to cast a fair observation of results in this discipline.

In my group, I have enthusiastically suggested to place the smallest targets at the farthest distances. Since we still use standard Metal Silhouette Airgun events, I proposed that we put the Airgun MS Chicken at 100 meters/yards. This way, it might be easier to score with the bigger Rams placed at a convenient 50 yards/meters. 

My question is, what is the best affordable bullets/slugs that is consistent and proven for airgun use?