Sinclair Internationalhas released an interesting article about Case Concentricity* and bullet “run-out”. This instructional article by Bob Kohl explains the reasons brass can exhibit poor concentricity, and why high bullet run-out can be detrimental to accuracy.
Concentricity, Bullet Alignment, and Accuracyby Bob Kohl
The purpose of loading your own ammo is to minimize all the variables that can affect accuracy and can be controlled with proper and conscientious handloading. Concentricity and bullet run-out are important when you’re loading for accuracy. Ideally, it’s important to strive to make each round the same as the one before it and the one after it. It’s a simple issue of uniformity.
The reason shooters work with tools and gauges to measure and control concentricity is simple: to make sure the bullet starts down the bore consistently in line with the bore. If the case isn’t properly concentric and the bullet isn’t properly aligned down the center of the bore, the bullet will enter the rifling inconsistently. While the bore might force the bullet to align itself with the bore (but normally it doesn’t), the bullet may be damaged or overstressed in the process – if it even it corrects itself in transit. These are issues we strive to remedy by handloading, to maintain the best standard possible for accurate ammunition.
The term “concentricity” is derived from “concentric circle”. In simple terms it’s the issue of having the outside of the cartridge in a concentric circle around the center. That goes from case head and center of the flash hole, to the tip of the bullet.
Factors Affecting Concentricity
The point of using this term is to identify a series of issues that affect accurate ammunition. Ideally this would work best with a straight-walled case; but since most rifle cartridge cases are tapered, it equates to the smallest cross section that can be measured point by point to verify the concentric circle around the center. For the examples below, I’m working with .308 Winchester ammo.
Figure 1: The cartridge.
Figure 2: Centerline axis of the case, extending from flash hole to case mouth.
The case walls have to be in perfect alignment with the center, or axis, of that case, even if it’s measured at a thousandth of an inch per segment (in a tapered case).
Figure 3: Case body in alignment with its axis, or centerline, even in a tapered case.
The case neck must also be in alignment with its axis. By not doing so you can have erratic bullet entry into the bore. The case neck wall itself should be as uniform as possible in alignment and in thickness (see the M80 7.62x51mm NATO cartridge in Figure 5) and brass can change its alignment and shape. It’s why we expand the case neck or while some folks ream the inside of the neck and then turn the outside for consistent thickness, which affects the tension on the bullet when seated.
Figure 4: Neck in alignment with center of the case axis.
Figure 5: Variations in case neck wall thickness, especially on some military brass, can cause an offset of the bullet in its alignment. This is an M80 ball round. Note the distinct difference of the neck walls.
Having a ball micrometer on hand helps, especially with military brass like 7.62x51mm in a semi-auto rifle, where there are limits as to how thin you want the neck walls to be. In the case of 7.62 ball brass you want to keep the wall to .0145″.
Figure 6: A ball micrometer like this RCBS tool (#100-010-268) can measure case neck thickness.
Turning the outside of the neck wall is important with .308 military cases regardless of whether you expand or ream the neck walls. There are several outside neck turning tools from Forster, Hornady, Sinclair, and others. I’ve been using classic Forster case trimming (#100-203-301) and neck turning (#749-012-890) tools for 40 years.
Bullet Run-Out
The cartridge, after being loaded, still needs to be in alignment with the center of the case axis. Figure 7 shows a bad example of this, a round of M80 ball. A tilted bullet is measured for what’s known as bullet “run-out”.
Figure 7: An M80 round with the bullet tilted and not aligned with the axis. This will be a flyer!
Run-out can be affected by several things: (1) improperly indexing your case while sizing, which includes not using the proper shell holder, especially while using a normal expander ball on the sizing die (it also can stretch the brass). (2) The head of a turret press can flex; and (3) improper or sloppy bullet seating. This is also relevant when it comes to using a progressive press when trying to load accuracy ammo.
Mid Tompkins came up with a simple solution for better bullet seating years ago. Seat your bullet half way into the case, back off the seater die and rotate the case 180 degrees before you finish seating the bullet. It cuts down on run-out problems, especially with military brass. You also want to gently ream the inside of the neck mouth to keep from having any brass mar the surface of the bullet jacket and make proper seating easier. A tilted bullet often means a flyer.
Figure 8: Proper alignment from the center of the case head to the tip of the bullet.
(NOTE: This links to a Web Archive version of the original Sinclair Int’l article.)
*Actually some folks would say that if we are talking about things being off-center or out-of-round, we are actually talking about “eccentricity”. But the tools we use are called “Concentricity Gauges” and Concentricity is the term most commonly used when discussing this subject.
Here’s a tip for guys who shoot the 6 PPC, 6 Dasher, 6 BRA, .284 Shehane, or other wildcat cartridges that require fire-forming. Use your fouler shots to fire-form new cases. That way your fouler shots do “double-duty” and you get your brass fire-formed without putting extra rounds through your expensive barrel.
This procedure is recommended by Joel Kendrick, the 2004 IBS 600-yard Shooter of the Year. After he cleans his barrel, Joel knows it takes two or three shots to foul in the bore before accuracy returns. When shooting his PPC, Joel uses those fouler shots to fire-form his new brass. Joel explains: “I like to have relatively new brass always ready. By fire-forming a couple cases after each barrel-cleaning during a match, by the end of the weekend I’ve got a dozen or more freshly fire-formed cases to put into the rotation. If you do this with your fouler shots you get your fire-forming accomplished without using up any extra barrel life.”
This not only saves barrel wear, but it saves you trips to the range for the purpose of fire-forming. We thank Joel for this smart suggestion. For those who do not have a dedicated barrel for fire-forming, this should help keep your round-count down. Note: With this fouler fire-forming routine, you should ALWAYS do the fire-forming with the SAME POWDER you load for your match ammo. Joel currently works as the Supplier Quality Process Engineer for MMI-TruTec, a company that offers barrel surface coatings that can further extend your barrel life.
Looking for a very affordable first rifle for a young family member? Here’s one of the best low-cost options you can find among .22 LR rimfire rigs. The Rossi RS22 is a reliable, semi-auto rifle that comes equipped with barrel-mounted iron/fiber optic sights. There are also dovetails on the receiver for mounting scope rings. The RS22 also takes most Mossberg 702 magazines.
The Rossi RS22 features an 18″ free-floating barrel, adjustable fiber optic sights and a synthetic Monte Carlo stock. For added accuracy, 3/8″ dovetail mounts allow the mounting of a scope or other optic (and there is a model with a Picatinny rail).
There are multiple RS22 models. The basic RS22 with black stock and iron sights is $149.99 at Sportsman’s Warehouse. If you prefer a different stock color, Sportsman’s Warehouse also has the iron sights RS22 with Green stock for $149.99 or Brown Stock for $189.99. If you will always be using a scope, consider the RS22 model with Picatinny scope rail and threaded barrel (but no iron sights) — it is on sale now for just $127.47 at Sportsman’s Warehouse.
Rossi RS22 Specifications:
Model: RS22 Semi-Auto, .22 LR
Barrel: 18″ Free-floating
Stock: Black Monte Carlo Synthetic Stock
Overall Length: 36.25″
Weight: 4.1 lbs.
NOTE: The Rossi RS22 on sale has a matte black stock.
Two Video Reviews of Rossi RS22
The above video review of the Rossi RS22 confirms its reliability and build quality. The reviewer praised the fiber-optic iron sights and liked the magazines. After fitting a scope to the rifle’s built-in dove-tail, the tester got excellent accuracy with CCI ammo at 25 yards. Ten shots basically formed one half-inch hole. (See video 8:24 – 8:50 and target at right.) That’s good enough for an NRL22 match. Pretty impressive for a $150 rifle!
Gunblast.com also tested the Rossi RS22. This “dandy little rifle” performed great, with flawless semi-auto feeding and cycling for hundreds of rounds. Accuracy was quite good. The tester praised the fit and feel of the stock and noted it has sling swivel studs and well-protected sights. The RS22 can also use 25-round Mossberg magazines.
This week, Shooting USA TV spotlights the 2025 GAP Grind, America’s largest PRS Pro-Am Tactical match. The 14th Annual Bushnell Tactical GAP Grind Pro/Am shooting match was held from October 3 to October 5, 2025. The event took place at the K&M Precision Rifle Training Complex in Finger, Tennessee. The GAP Grind, the largest PRS match in the world, drew nearly 400 amateur and pro shooters. Recognized as the premier PRO-AM precision rifle match with both individual and team competition, the GAP Grind has introduced many new shooters to the sport. The next GAP Grind match will be held October 3–4, 2026 at the K&M Complex in Tennessee.
SHOW TIMES: This Shooting USA Episode airs Wednesday, July 8, 2026 at 9:00 PM Eastern and Pacific; 8:00 PM Central. If you miss the regular broadcast, you can stream on Vimeo for $0.99 per episode. You can also see hundreds of shooting videos for free on Shooting USA’s YouTube channel.
In this video Eagle Eye Shooting Shares Highlights from the 2022 GAP Grind
Big Prize Table at 10th Annual GAP Grind Event
The year’s largest PRS match drew hundreds of attendees, and more than 80,000 rounds were fired throughout the three-day event. Bushnell provided thousands of dollars worth of prizes to the top competitors. Trophies were awarded to the top 5 teams, top 5 professionals, and to the top 5 amateurs.
Lots of Action, with 20+ Stages
The GAP Grind is a challenging, “high tempo” match with minimal down-time between stages. Over the course of 20+ stages, competitors will fire 200+ shots at a variety of steel, paper, moving, and reactive targets out to 1,200 yards. Targets vary in size/difficulty based on the shooter’s position, distance, and time allotted. Most stages include “stressors” — i.e. time limits or required movement(s).
GAP Grind Pro-Am Format — Seasoned Shooters Help Newcomers
The GAP Grind typically attracts nearly 400 competitors — half experienced shooters and the other half newcomers to the sport. The key to growing the shooting sports is attracting new shooters. The best way to bring in “new blood” seems to be the Pro-Am type format. At the GAP Grind, experienced shooters share their knowledge and guide the new shooters through the competition.
GAP Grind Hardware
You’ll find the latest and greatest PRS/NRL hardware at the GAP Grind. Over the past few seasons, most top competitors have “stepped down” from the 6.5/6mm Creedmoor to the smaller, more efficient 6mm Dasher, 6BRA, 6 GT and other 6mm cartridges. These 6mm cartridges offer excellent accuracy with less recoil than the 6.5 Creedmoor.
The U.S. Army Marksmanship Unit published a series of reloading “how-to” articles on the USAMU Facebook page. A while back the USAMU’s reloading gurus looked at the subject of cartridge run-out and what can be done to produce straighter ammo. Tasked with producing thousands of rounds of ammo for team members, the USAMU’s reloading staff has developed smart methods for improving concentricity, even with budget-priced dies. For other hand-loading tips, visit the USAMU Facebook page.
Minimizing Runout with Standard Seating Dies
This USAMU article explains how to set up standard bullet seating dies dies to minimize Total Indicated Run-out (TIR). The loading process is described using a single-stage press since most handloaders have one. A high-quality run-out gauge is essential for obtaining consistent, accurate results.
Having sized, primed, and charged our brass, the next step is bullet seating. Many approaches are possible; one that works well follows. When setting up a standard seating die, insert a sized, trimmed case into the shellholder and fully raise the press ram. Next, back the seating stem out and screw the die down until the internal crimping shoulder touches the case mouth.
Back the die out ¼ turn from this setting to prevent cartridge crimping. Next, lower the press ram and remove the case. Place a piece of flat steel (or window glass, which is quite flat) on the shellholder and carefully raise the ram.
Place tension on the die bottom with the flat steel on the shellholder. This helps center the die in the press threads. Check this by gently moving the die until it is well-centered. Keeping light tension on the die via the press ram, secure the die lock ring. If one were using a match style, micrometer-type seating die, the next step would be simple: run a charged case with bullet on top into the die and screw the seating stem down to obtain correct cartridge OAL.
However, with standard dies, an additional step can be helpful. When the die has a loosely-threaded seating stem, set the correct seating depth but don’t tighten the stem’s lock nut. Leave a loaded cartridge fully raised into the die to center the seating stem in the die. Then, secure the stem’s lock nut. Next, load sample cartridges and check them to verify good concentricity.
One can also experiment with variations such as letting the seating stem float slightly in the die to self-center, while keeping correct OAL. The run-out gauge will show any effects of changes upon concentricity. However, this method has produced excellent, practical results as evidenced by the experiment cited previously. These results (TIR Study 2) will reproduced below for the reader’s convenience.
First, however, let’s examine run-out figures of some factory-loaded match ammunition. This should give readers who are new to TIR gauges some perspective about the TIR ranges one might encounter.
TIR Study 1: 50 rounds Lake City M852 Match 7.62mm
(168 gr. Sierra MatchKings)
0.000” – 0.001” = 2%
0.001” – 0.002” = 30%
0.002” – 0.003” = 16%
0.003” – 0.004” = 22%
0.004” – 0.005” = 14%
0.005” – 0.006” = 14%
0.006” – 0.007” = 0%
0.007” – 0.008” = 2%
TIR Study 2: 50 rounds of .308 match ammo loaded using carefully-adjusted standard dies, vs. 50 using expensive “Match” dies from the same maker.
Standard dies, TIR:
0.000” — 0.001” = 52%;
0.001”– 0.002” = 40%;
0.002”– 0.003” = 8%.
None greater than 0.003”.
Note: both samples were loaded using the O-Ring method, i.e. with a rubber O-Ring placed under the locking ring of the Full-length sizing die to allow that die to float.
These tips are intended to help shooters obtain the best results from inexpensive, standard loading dies. Especially when using cases previously fired in a concentric chamber, as was done above, top-quality match dies and brass can easily yield ammo with virtually *no* runout, given careful handloading.
The CMP 2026 National Matches at Camp Perry, Ohio start in six days. The 2026 CMP National Matches will take place at Camp Perry from July 12 through August 8, 2026, with the First Shot Ceremony on Monday, July 13, 2026.
The rifle segments of the CMP National Matches commence next week at Camp Perry. First there will be smallbore competition July 12-22, with centerfire rifle matches commencing on July 20, and running through August 8, concluding with the Mid-Range and Long Range Matches.
To help those who will be competing this year, we offer Ten Lessons from Gary Anderson, DCM Emeritus.
TEN WAYS to Win — Competition Advice from Gary Anderson
In the archives of On The Mark magazine, Gary Anderson, an Olympic Gold medal-winning shooter, offers sage advice for competitive shooters.
In his article Ten Lessons I Wished I Had Learned as a Young Shooter, Anderson provides ten important guidelines for everyone involved in competitive shooting. Here are the Ten Lessons, but you should read the full article. Anderson provides detailed explanations of each topic with examples from his shooting career.
LESSON 1 – NATURAL ABILITY WILL NOT MAKE YOU A SHOOTING CHAMPION.
(You also need hard work, training effort and perseverance.)
LESSON 2 – ANGER IS THE ENEMY OF GOOD SHOOTING.
(The key to recovering from a bad shot is to stay cool, no matter what happens.)
LESSON 3 – BAD SHOTS CAN TEACH YOU MORE THAN GOOD SHOTS.
(Today, error analysis is one of the most powerful tools for improving scores.)
LESSON 4 – NEVER GO WITHOUT A SHOT PLAN.
(A shot plan is a detailed breakdown of each of the steps involved in firing a shot.)
LESSON 5 – PRACTICE IN BAD CONDITIONS AS WELL AS GOOD CONDITIONS.
(Most competitions are fired in windy conditions or where there are plenty of distractions.)
LESSON 6 – CHAMPIONS ARE POSITIVE, OPTIMISTIC PEOPLE.
(Negative shooters expect bad results; positive shooters expect to train hard to change bad results.)
LESSON 7 – IT’S NOT ABOUT WHETHER YOU WIN OR LOSE.
(It’s about how hard you try to win.)
LESSON 8 – YOUR DOG WON’T BITE YOU AFTER SHOOTING A BAD SCORE.
(Hopefully your coach, parents and friends won’t bite you either.)
LESSON 9 – YOUR PRESS CLIPPINGS CAN HURT YOU OR HELP YOU.
(Winning can go to our heads. We start thinking we are so good we don’t have to work hard any more.)
LESSON 10 — YOU NEVER SHOT YOUR BEST SCORE.
(Great champions are always looking for ways to improve.)
About Gary Anderson Gary Anderson served as the Director of the Civilian Marksmanship Program (CMP) from 1999-2009, and is now DCM Emeritus. In 1959, he joined the elite U.S. Army Marksmanship Unit. Just two years later, he won his first national championship. Over his competitive career, Anderson won two Olympic Gold Medals, seven World Championships, and sixteen National Championships. He is unquestionably one of the greatest American marksmen ever.
At the 1962 World Shooting Championships in Egypt, Anderson won four individual titles and set three new world records. At the 1964 Tokyo Olympics, Gary won the 300m free-rifle Gold Medal, setting a new world record. At the 1966 World Shooting Championships in Germany, Anderson won three additional world titles. At the 1968 Olympics, Gary won a second gold medal in the 300m free-rifle event. After his “retirement” from international competition, Gary competed in the National High Power Championships, winning the President’s National Trophy in 1973, 1975 and 1976.
This USAMU article explores three different “Philosophies” of precision reloading. Some handloaders seek to produce ammo that yields the very tightest groups (without factoring in the wind). Other shooters load their ammo to deliver the highest safe velocity. That’s because a projectile launched at higher velocity will drift less in the wind. The theory is that even if fast ammo doesn’t produce the tightest groups in zero wind conditions, it will yield higher scores in a the real world (where the wind blows). Lastly, some handloaders favor ammo that is ultra-consistent across a wide temperature range. This last philosophy dictates selection of a powder that is temp-insensitive, even if it may not produce the very best raw accuracy (or speed).
What’s Your Handloading Philosophy?
Objectives of Reloading — Accuracy, Velocity, Temp Stability What do you, the reader, primarily value in your handloads?
Viewpoint ONE: Accuracy Trumps Everything
Some shooters prize consistent, excellent medium/long range accuracy enough that they’re willing to give up some extra velocity (and reduced wind deflection) to obtain that. Their underlying philosophy could be stated: “Superior accuracy is present for every shot, but the wind isn’t”. One’s ability to hold well, aim well and read the wind are all factors in making this type decision. The photo below shows stellar raw accuracy. This is an 0.67″, 10-shot group at 300-yards fired from a text fixture. The group measures just 0.67″. (This shows the USAMU’s 600-yard load with 75gr bullets).
Viewpoint TWO: Load to Highest Safe Velocity for Less Wind Drift
Some shooters value obtaining the highest safe velocity, even if one’s pure, consistent mechanical accuracy at medium/long range isn’t quite as brilliant. The theory here seems to be that a really good hold extracts as much mechanical accuracy from the rifle/ammo as possible, and faster bullets equal occasional “bonus” points snatched from the jaws of wind.
[For example] one of the USAMU’s many Service Rifle National Champions revealed his philosophy. It can be stated thus: a super-accurate, but [relatively] “slow” load “required him to have a Ph.D. in wind reading for every shot, while a faster, but less accurate load netted him more points.”
Note — this was not mere speculation; his score book data backed up his claims, due to less wind effects. Remember, however, this fellow has a consistent, National Championship-level hold, and other Champions on the same team would have opted differently.
Viewpoint THREE: Temperature Stability Is Key
Still another approach is to place heavy emphasis on fine accuracy with absolute stability in changing temperatures. When this writer was actively earning his Distinguished Rifleman badge, that was his goal. The reason? Sighting shots are not allowed in EIC (“Leg”) matches. The first shot out of the barrel was for score. It had to be 100% consistent, with very reliable, predictable elevation and wind deflection regardless of the ambient temperature — even if it wasn’t the lowest wind deflection possible.
Naturally, selecting a powder that is insensitive to temperature changes is a key element here. Elevation zeros and wind effects HAD to be consistent every time. Hunters and military snipers might be among those who fall into this camp, as well as those in pursuit of their Distinguished Rifleman badges.
Contrast that with a traditional High Power shooter who gets two sighter shots before each event (offhand, sitting rapid, prone rapid, prone slow fire.) If there is a zero change on any given day, he/she can correct during sighters. This writer well remembers talking with another very high-level Service Rifle competitor who was happy to have high temperatures boost the velocities of his ammunition above their usual level… As far as this SR competitor was concerned, 60-80 fps more velocity -– even if only due to high ambient temperatures -– meant less wind deflection, and he was mighty happy to have it.
Particularly in the summer, with hot daily conditions, you need to be concerned about temperature stability. Loads worked up in winter may be over-pressue in the summer time. FYI summer officially begins this year on June 21, 2026, Summer Solstice, just 10 days away.
This article has been confined to NRA High Power Rifle competition, which has relatively generous 10-ring dimensions in relation to the accuracy of well-built competition rifles. Hopefully, it will provide food for thought. For some, this might be an opportunity to ensure that one’s load development approach helps them attain their desired results.
Federal Ammunition has introduced a new type of firearm cover, the Federal Fit Coil Rifle Cover. The Federal Fit Coil Rifle Cover features a roll-up design that lets shooters adjust cover length to the firearm. A key feature is an internal retracting elastic band that allows easy insertion but also adapts the cover to the actual rifle length from muzzle to buttpad.
Federal’s new rifle cover is “suppressor-ready”, meaning the muzzle area inside the cover has heat-resistant lining. Sizes include medium for firearms of 34 to 44 inches in length, large for 39 to 49 inches, and XL for 44 to 54 inches. All sizes are equipped with a quick-grab handle.
“With a roll-up design that lets shooters adjust case length to the firearm, our Federal Fit Coil Rifle Cover is a suppressor-ready rifle case that is ready for anything,” explains Jake Jacobs, Federal’s Accessories Product Director. “It has a heat-resistant lining in the muzzle area and a quick-grab handle. With suppressors being so wildly popular these days, having the gear needed to protect them properly and conveniently is an absolute necessity.”
At the request of our readers, we provide select “Deals of the Week”. Every Sunday afternoon or Monday morning we offer our Best Bargain selections. Here are some of the best deals on firearms, hardware, reloading components, optics, and shooting accessories. Be aware that sale prices are subject to change, and once clearance inventory is sold, it’s gone for good. You snooze you lose.
NOTE: All listed products are for sale to persons 18 years of age or older. No products are intended for use by minors.
Brownells – Freedom Sale + 12% Savings with Code FREEDOM12
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Brownells is running a major Freedom to Boom Sale this week in preparation for July 4 and the nation’s 250th anniversary. A wide variety of products are on sale, including Howa barreled actions, Athlon chronographs, and AccuTac bipods. PLUS you can save 12% on most products with code FREEDOM12.
Sportsman’s Warehouse — Vortex Month 15% Off All Products
⏺️ » Save 15% in July on all Vortex products
All July, Sportsman’s Warehouse is running a big SALE on Vortex products, with a 15% discount applied on all Vortex products: Rifle scopes, Spotting scopes, Rangefinders, Binoculars, Red Dots, Rings/bases, Scope caps, Binoculars carry packs, and even some Vortex brand apparel. If you need a new optic, now is a great time to buy at Sportsman’s Warehouse. On a $900 scope you’d save $135.00 with this 15% Off sale.
As an Amazon affiliate, this site can earn revenues through sales commissions.
Coalinga Range in California. At dawn we could clearly see 7mm and .30 Cal bullet holes at 1000 yards.
While attending the CA Long Range Championship a few seasons back, we had the opportunity to test the performance of a high-magnification (63X) spotting scope in near-ideal conditions (maybe the best I’ve ever witnessed). On the event’s last day we arrived at 5:45 am, literally as the sun was cresting the horizon. I quickly deployed our Pentax PF-100ED spotting scope, fitted with a Pentax SMC-XW 10mm fixed-power eyepiece. When used with the 100mm Pentax scope, this 10mm eyepiece yields 63X magnification. Befitting its $319.00 price, this eyepiece is extremely clear and sharp.
At the crack of dawn, viewing conditions were ideal. No mist, no mirage, no wind. The first thing this Editor noticed was that I could see metal nail heads on the target boards. That was astonishing. As soon as the first practice targets went up, to my surprise, I could see 6.5mm, 7mm, and 30-caliber bullet holes in the white at 1000 yards. No lie…
That’s right, I could see bullet holes at 1000. I know many of you folks may not believe that, but there was no mistaking when I saw a 7mm bullet cut the white line separating the Nine Ring and Eight Ring on the target in view. (I was watching that target as the shot was fired and saw the shot-hole form). And when I looked at the 30-cal targets, the bullet holes in the white were quite visible. In these perfect conditions I could also make out 3/8″ bolt heads on the target frames.
The Human Factor — Good Vision Required
When viewing the bullet holes, I was using my left naked eye (no safety glasses or magnification). I also had a contact lens in my right eye (needed for distance vision). To my surprise, while I could see the bullet holes without much difficulty with my left eye, things were fuzzier and slightly more blurry with the right eye, even when I re-focused the scope. That contact lens was degrading the fine resolution.
Then I invited 3 or 4 shooters to look through the scope. One younger guy, with good eyes, said immediately: “Yeah, I can see the holes — right there at 4 o’clock and seven o’clock. Wow.” Some older guys, who were wearing glasses, could not see the holes at all, no matter what we did to the scope’s main focus and diopter adjustment.
The lesson here — if you have to wear glasses or corrective contact lenses, just that extra bit of optical interference may make a difference in what you can see through the scope. Basically anything that goes between the scope eyepiece and your eyeball can degrade the image somewhat. So… you may be better off removing your glasses if you can still obtain good focus sharpness using the diopter adjustment and focus ring. I did the left vs. right eye test a half dozen times, and I could definitely see small features at 1000 yards with my naked eye that I could not see with my right eye fitted with a contact lens. (I did have to re-focus the scope for each eye, since one had a corrective lens while the other did not.)
Mirage Degrades Image Sharpness and Resolution
The “magic light” prevailed for only an hour or so, and then we started to get some mirage. As soon as the mirage appeared I was no longer able to see raw bullet holes, though I could still easily see black pasters on the black bulls. When the mirage started, the sharpness of the visible image degraded a huge amount. Where I could see bullet holes at dawn, by mid-morning I could barely read the numbers on the scoring rings. Lesson: If you want to test the ultimate resolution of your optics, you need perfect conditions.
Chromatic Aberration Revealed
As the light got brighter and the mirage increased I started to see blue and red fringing at the edges of the spotting disk and the large numerals. This was quite noticeable. On one side of the bright, white spotting disc you could see a dark red edge, while on the other side there was a blue edge (harder to see but still present).
The photo below was taken through the Pentax spotter lens using a point and shoot camera held up to the eyepiece. The sharpness of the Pentax was actually much better than this photo shows, but the through-the-lens image does clearly reveal the red and blue fringing. This fringing is caused by chromatic aberration — the failure of a lens to focus all colors to the same point. Chromatic aberration, most visible at high magnification, causes different wavelengths of light to have differing focal lengths (see diagram). Chromatic aberration manifests itself as “fringes” of color along boundaries that separate dark and bright parts of the image, because each color in the optical spectrum cannot be focused at a single common point on the optical axis. Keep in mind that the Pentax does have “ED” or low-dispersion glass, so the effect would be even more dramatic with a cheaper spotting scope.
If you wonder why top-of-the-line spotting scopes (such as the $3558.00 Swarovski ATS-80 ) cost so much, the answer is that they will deliver even LESS chromatic aberration at long range and high magnification. With their exotic apochromatic (APO), ultra-low-dispersion glass, a few ultra-high-end spotting scopes can deliver an image without the color edging you see in the photo above.
The Pentax PF-100ED is a heck of a spotting scope. Any scope that can resolve bullet holes at 1000 yards is impressive. But if you want the ultimate in optical performance, with minimal chromatic aberration, you may need to step up to something like the 88mm Kowa Prominar TSN-88A with Flourite Crystal lenses ($3999.00 with eyepiece), or the 82mm Leica APO-Televid ($3649.95 with 25-50X eyepiece).
EDITOR’s NOTE: The purpose of this report is to show what is possible… in IDEAL conditions. With this Pentax 100mm, as well as a Swarovski 80mm, we can often resolve 6mm bullet holes at 600 yards. But again, that performance requires really good viewing conditions. By 10:00 am at my range, even with the 100mm Pentax at 75 power, seeing 6mm bullet holes is “iffy” at best. So don’t go out and mortgage the house to buy a $4000 optic with the hope that you’ll be able to spot your shots at 1000 yards. If conditions are anything less than perfect, you’ll be lucky to see bullet holes at 500 yards.
The real solution for very long-range spotting is to set up a remote target cam that broadcasts a video picture to a screen at your shooting station. Among the target cams on the market, we recommend the LongShot LR-3 2-mile UHD. This modern target cam system boasts excellent resolution and incredible range. The LongShot LR-3 target cam is used in major ELR competitions. The Longshot LR-3 currently sells for $999.00 on Amazon.
Sinclair International has released an interesting article about Case Concentricity* and bullet “run-out”. This instructional article by Bob Kohl explains the reasons brass can exhibit poor concentricity, and why high bullet run-out can be detrimental to accuracy.
Here’s a tip for guys who shoot the 6 PPC, 6 Dasher, 6 BRA, .284 Shehane, or other wildcat cartridges that require fire-forming. Use your fouler shots to fire-form new cases. That way your fouler shots do “double-duty” and you get your brass fire-formed without putting extra rounds through your expensive barrel.
In the archives of 
Gary Anderson served as the Director of the Civilian Marksmanship Program (CMP) from 1999-2009, and is now DCM Emeritus. In 1959, he joined the elite U.S. Army Marksmanship Unit. Just two years later, he won his first national championship. Over his competitive career, Anderson won two Olympic Gold Medals, seven World Championships, and sixteen National Championships. He is unquestionably one of the greatest American marksmen ever.
While attending the CA Long Range Championship a few seasons back, we had the opportunity to test the performance of a high-magnification (63X) spotting scope in near-ideal conditions (maybe the best I’ve ever witnessed). On the event’s last day we arrived at 5:45 am, literally as the sun was cresting the horizon. I quickly deployed our 
Then I invited 3 or 4 shooters to look through the scope. One younger guy, with good eyes, said immediately: “Yeah, I can see the holes — right there at 4 o’clock and seven o’clock. Wow.” Some older guys, who were wearing glasses, could not see the holes at all, no matter what we did to the scope’s main focus and diopter adjustment.
Chromatic Aberration Revealed
