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January 31st, 2023

What Level of Accuracy is “Good Enough” for Your Discipline?

Jim See Elite Accuracy
This impressive 15-round group was shot by Jim See of Elite Accuracy.

Different Shooting Disciplines Demand Different Levels of Precision/Accuracy
In the rapid-fire 3-Gun game, you could probably “clean” most stages with a 2-MOA rifle. By contrast, in the short-range group benchrest game, to compete with the best, you’ll need a rifle that shoots in the “ones” (i.e. 0.1-0.19 MOA) in perfect conditions. In 1000-yard F-Class competition, the top shooters want a rifle that will hold one-third-MOA of vertical at that distance.

What is your standard of accuracy? How good is “good enough”. Jim See, a skilled gunsmith and successful PRS competitor, recently answered that question for his tactical discipline. For the kind of matches Jim shoots, he likes to have a rifle that will hold half-MOA for five (5) shots, 3/4-MOA for 15 shots, and 1 MOA for twenty shots. Remarkably, Jim’s rifle can do that with factory ammo. Above is an impressive 15-shot group shot with .260 Remington Federal Premium Ammo.

Jim See Elite Accuracy

“I say it all the time, my loads need to print 5 under 1/2″, 10 under 3/4″, and 20 under 1″. It’s simple, if a hot barrel will keep 20 rounds fired in succession under my standard it will be a good barrel and load for Precision Match Shooting. Federal Premium Gold Metal Match .260 with Sierra bullets made the cut for me today. 15 consecutive shots under 3/4 MOA.” –Jim See

It’s said that you “can never have too much accuracy”, but there are acceptable standards for each discipline, and they’re not the same. A 100/200 yard Benchrest shooter will be sorely disappointed with a rifle/ammo set-up that can only deliver half-MOA. On the other hand, a PRS competitor like Jim See can achieve great success with a lesser degree of precision. This means you can save time and money. You can run your barrels longer between cleanings, and you don’t have to go “full OCD” when loading your ammo. The PRS shooter does not need to weigh-sort primers, or load powder to single-kernel standards. Proof is the performance. Jim See recently took third place at the Spearpoint Shootout, and he has been a podium finisher at other events. Learn more about Jim’s gunsmithing and training operations at EliteAccuracy.com.

Download This Load Development Target

Jim’s target seemed a bit familiar. AccurateShooter.com created this Diamond and Dot Target a few years back. On each aiming point, there are high-contrast black horizontal and vertical lines for aligning your cross-hairs. The gray circle lets you see the bullet impacts above, without obliterating the red diamond, which is quite useful for precise aiming (we put fine cross-hairs on the points of the diamond). This target sheet includes data entry tables below each of the three aim points. There are many other free targets out there, but this format is very popular. We’re pleased to see Jim using it. You can download this and dozens of other FREE Targets from the AccurateShooter.com Target Page.

AccurateShooter precision load development free target

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January 31st, 2023

Shooting on a Spinning Planet — Explaining the Coriolis Effect

Whittington Coriolis Effect
Photo by Dustin Ellermann at Whittington Center Range.

The Coriolis Effect comes into play with extreme long-range shots like this (2100 yards at Raton, New Mexico). The rotation of the earth actually moves the target a small distance (in space) during the long duration of the bullet’s flight.

Coriolis Effect Bryan Litz Applied BallisticsWhen you’re out at the range, the Earth seems very stable. But it is actually a big sphere zooming through space while spinning around its axis, one complete turn every 24 hours. The rotation of the earth can create problems for extreme long-range shooters. During extended bullet flight times, the rotation of the planet causes an apparent deflection of the bullet path over very long distances. This is the ballistics manifestation of the Coriolis Effect.

Bryan Litz of Applied Ballistics discusses explains the Coriolis Effect in his Ballistics Books and Seminars. Bryan notes that Coriolis is “a very subtle effect. People like to make more of it than it is because it seems mysterious.” In most common shooting situations inside 1K, Coriolis is not important. At 1000 yards, the Effect represents less than one click (for most cartridge types). Even well past 1000 yards, in windy conditions, the Coriolis Effect may well be “lost in the noise”. But in very calm conditions, when shooting at extreme ranges, Bryan says you can benefit from adjusting your ballistics solution for Coriolis.

Bryan explains: “The Coriolis Effect… has to do with the spin of the earth. You are basically shooting from one point to another on a rotating sphere, in an inertial reference frame. The consequence of that is that, if the flight time of the bullet gets significantly long, the bullet can have an apparent drift from its intended target. The amount [of apparent drift] is very small — it depends on your latitude and azimuth of fire on the planet.”

Coriolis Effect Bryan Litz Applied Ballistics

Coriolis is a very subtle effect. With typical bullet BCs and velocities, you must get to at least 1000 yards before Coriolis amounts to even one click. Accordingly, Bryan advises: “Coriolis Effect is NOT something to think about on moving targets, it is NOT something to think about in high, uncertain wind environments because there are variables that are dominating your uncertainty picture, and the Coriolis will distract you more than the correction is worth.”

“Where you could think about Coriolis, and have it be a major impact on your hit percentage, is if you are shooting at extended range, at relatively small targets, in low-wind conditions. Where you know your muzzle velocity and BC very well, [and there are] pristine conditions, that’s where you’re going to see Coriolis creep in. You’ll receive more refinement and accuracy in your ballistics solutions if you account for Coriolis on those types of shots. But in most practical long-range shooting situations, Coriolis is NOT important. What IS important is to understand is when you should think about it and when you shouldn’t, i.e. when applying it will matter and when it won’t.”

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January 31st, 2023

Throat Erosion Revealed in Sliced Barrel — 2mm of Lands Wear

So what does a “worn-out” barrel really look like? Tom Myers answered that question when he removed a 6.5-284 barrel and cut it down the middle to reveal throat wear. As you can see, there is a gap of about 5mm before the lands begin and you can see how the lands have thinned at the ends. (Note: even in a new barrel, there would be a section of freebore, so not all the 5mm gap represents wear.) There is actually just about 2mm of lands worn away. Tom notes: “Since I started out, I’ve chased the lands, moving out the seating depth .086″ (2.18 mm). I always seat to touch. My final touch dimension was 2.440″ with a Stoney Point .26 cal collet.”

Except for the 2mm of wear, the rifling otherwise looks decent, suggesting that setting back and rechambering this barrel could extend its useful life. Tom reports: “This was something I just thought I’d share if anyone was interested. I recently had to re-barrel my favorite prone rifle after its scores at 1,000 started to slip. I only ever shot Sierra 142gr MatchKings with VV N165 out of this barrel. It is a Hart and of course is button-rifled. I documented every round through the gun and got 2,300 over four years. Since I have the facilities, I used wire EDM (Electro Discharge Machining) to section the shot-out barrel in half. It was in amazingly good shape upon close inspection.”

Tom could have had this barrel set back, but he observed, “Lately I have had to increase powder charge to maintain 2,950 fps muzzle velocity. So to set it back would have only increased that problem. [And] I had a brand new 30″ Krieger all ready to screw on. I figured it was unlikely I’d get another full season on the old barrel, so I took it off.”

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