Top to bottom: Remington firing pin assembly with ISS, Tubb SpeedLock alloy-composite system without ISS (current versions have dual, opposite-wound springs), and Remington short action firing pin assembly without ISS.
The U.S. Army Marksmanship Unit regularly publishes technical articles on the USAMU Facebook page. One informative USAMU article covered mechanical issues and related ignition irregularities that can cause vertical fliers even with good ammunition in an otherwise excellent rifle. We highly recommend you read this article, which offers some important tech tips.
Vertical Dispersion: Mechanical/Ignition Issues?
Poor or inconsistent ignition has long been known to be one of the “usual suspects” when one encounters vertical fliers that just shouldn’t be there. By having a sense of some of the basic principles involved, and a few basic areas to check, the shooter may avoid colsiderable frustration, not to mention time, expensive loading components and barrel wear.
Is your well-built rifle of high-quality components plagued with vertical fliers across more than 1-3 handload combinations? Consider the bedding, crown and scope/sight mounts. Are they correct? If so, then you might check for ignition issues before boldly undertaking an extensive, expensive, and quite possibly fruitless quest for the “magic handload”.
SEEING IS BELIEVING: While the author had been aware for many years that poor ignition should be considered and ruled out when dealing with vertical fliers in an otherwise-excellent rifle, actually seeing the problem and its almost instantaneous cure really drove the lesson home.
He was working with a “dot” rifle – a .22 LR match rifle that really stacked bullets into little piles at 50 yards and beyond. With one lot of ELEY Tenex, it produced consistent “bughole” groups at 50, but with another, selected lot of Tenex, similar groups were regularly ruined by single, vertical fliers that did not appear in other rifles. Rather than spending days burning up expensive, select ammunition looking for “magic lots”, he contacted a well-respected rimfire gunsmith and explained the situation.
Without so much as batting an eye, the highly-experienced ‘smith tore into the rifle’s action, and quickly found the cause(s) of the problem. He discovered a demonstrably weak firing pin spring, plus a chip out of the face of the firing pin where it contacted the cartridge rim.
After replacing and tuning the offending parts, the rifle immediately began shooting tiny, bughole groups with the previously “unacceptable” lot of Tenex. Centerfire rifles can also benefit from ensuring positive, consistent ignition. A wise riflesmith is literally worth his weight in gold!
So, what are some issues we as shooters can inspect in our rifles to help determine if ignition woes could be part of our problem? At the club level, ask yourself if that “experienced” Remington, Winchester 70, or even Springfield-based match bolt gun you’re using is still running its’ original 40-80 year-old factory striker spring? If so, a new replacement is cheap insurance against current or future problems. (And BTW, it might be best to stick to the normal, factory-spec spring weight. A super-powerful spring can cause vertical, just as a weak one one can.) Along with that, a routine check for proper firing-pin protrusion is a quick preventive measure that can rule out potential issues.
Other areas to consider are the centering and consistency of the firing pin’s operation in the bolt. Admittedly, with the increasing use of precision-machined custom actions, this is becoming less an issue every day. Below is the firing pin assembly from a custom BAT action:
However, particularly with factory actions, a very quick and easy check is to remove the bolt, let the firing pin go forward, and look at the firing pin tip through the firing pin hole. Is the tip off-center in the hole, and possibly striking it as it moves forward? Is the hole out-of-round or burred from being struck repeatedly? If so, a trip to the riflesmith is likely in order.
Similarly, machining issues in the bolt/firing pin system can lead to rough and erratic firing pin movement, in which the firing pin drags against an internal surface of the bolt. In high-quality rifles these issues are relatively rare, but not unheard-of, and it takes mere minutes to rule them out. It may be worthwhile to remove the cocking piece/firing pin/spring assembly and look for any unusual gouges, dings, peening, burrs or signs of abnormal wear.
This task is especially easy with Winchester 70s, Springfields, and the similar Mauser 98s, involving little more than the push of a button and unscrewing the cocking piece assembly. This is just one of the many reasons these tried-and-true actions have earned such a loyal following in the field, among hunters who must maintain their rifles away from a shop.
Particularly with older rifles, watch for and remove excess grease (or even Cosmoline!) from both the firing pin assembly and inside the bolt. This can help improve firing pin speed and consistency. Other bolt-action designs may need a take-down tool or other measures.
As part of this inspection, AFTER ENSURING THE RIFLE IS UNLOADED, slowly cock the rifle, dry-fire, and repeat several times. Listen carefully near the action for inconsistency in the sounds it generates. Does the striker falling make the same sound each time? Do you hear or feel grinding upon operation? If so, where?
Be sure to check the operation of the cocking piece (bolt shroud), firing pin within the bolt shroud, the cocking piece cam and the rear of the bolt body where the cocking piece cam operates. As with our examination for abnormal wear marks discussed above, look for marks indicating roughness or a possible need for light polishing. Then, clean and lightly grease the bearing surfaces while you’re at it.
Remington 700 bolt shroud and cocking cam
These are relatively easy checks that shooters can undertake to perform a preliminary inspection on their own. Other mechanical issues can also cause ignition issues, chiefly centered around the action of the trigger, sear and sear spring. If these are suspected, a trip to an experienced, qualified riflesmith for diagnosis is recommended. We hope you find this information helpful! Join us again next week, and in the meantime, enjoy the shooting sports safely!
While devotees of this site are hard-core accuracy addicts, who normally shoot tiny groups with sophisticated Benchrest and Varmint rifles, we should not overlook the pure fun of shooting a classic iron sights lever-action rifle at reactive targets. Lever guns are fun to shoot, easy to transport, AND they require a lot less maintenance than your modern black rifle.
Drilling a tight 1/4-MOA group is very satisfying. But for simple, basic shooting fun, it’s hard to beat a slicked-up, “race-ready”, Winchester-clone lever gun. In fact, this Editor’s favorite rifle for “fun shooting” is my 20″ Uberti Model 1866 “Yellowboy” Lever gun. Shooting low-recoil .38 Special rounds at steel targets from a standing position offers old-fashioned shooting satisfaction. When I invite a new shooter to the range, I usually bring the 1866 Yellowboy, and let the newbie shoot steel at 50 yards. New shooters (of all ages) love the look and feel of the rifle, and the low recoil. The typical response is: “Wow, that was fun!”.
My rifle features a slicked-up action and lightened trigger. After a “CodyMatic” action job by cowboy gunsmith Cody Conagher, my Yellowboy’s lever can be cycled with just one finger. Trigger pull is about a pound and a half. The high-gloss, blued octagonal barrel is very accurate and the mirror-finish bore cleans up easily.
Based on the Model 1866 Winchester, Uberti’s Yellowboy, and its Model 1873 “older brother”, feature a toggle-link action that is extremely smooth. The toggle action design also keeps the linkages separate from the chamber so the gun runs extremely clean. After firing 100 rounds or more, all you need to do is wipe off the bolt and breech-face with some solvent and run a bore-snake down the bore a few times. To be honest, the Yellowboy is more fun to shoot at steel than my AR Carbine. And maintenance-wise, for every five minutes I spend cleaning the 1866, I’ll spend an hour detail-stripping and cleaning the AR. The shooting-to-cleaning ratio favors the lever gun by orders of magnitude.
These Italian-made Winchester clones are very handsome, with nicely figured wood under a durable clearcoat. You can polish the brass receiver to keep it shiny, or leave it alone to develop an authentic, dulled patina. Uberti’s Model 1873 features a steel receiver with gorgeous color case-hardening.
After the fun factor, what’s the best thing about Uberti lever guns? Resale value. I can sell my 1866 for quite a bit more than I paid for it. Over the past decade, the price of Italian-made Uberti lever guns has been steadily rising. This means that older rifles fetch a premium on the used market.
Here’s a simple solution for lumpy front sandbags. Cut a small block the width of your fore-end and place that in the front bag between matches. You can tap it down firmly with a rubber mallet.
The block will keep the front bag nice and square, without bunching up in the center. That will help your rifle track straight and true. Rick Beginski uses wood (see photo), while our friend John Southwick uses a small block of metal. The metal block might work a little better, but the wood version is easier to make with simple tools. Shown above is a slick Delrin block with a built-in bubble level used with a quality J.J. Loh front rest. Using a good block on your front bag helps ensure that the actual top surface of your front bag is level, as distinct from the front rest assembly.
Lyman’s popular E-Zee Case Length Gauge II is now bigger and better. The latest version of Lyman’s Case Gauge is much larger than the original version. The Case Gauge II now measures more than 70 cartridge types — way more than before. This tool is a metal template with SAAMI-max-length slots for various cartridge types, including modern cartridges such as the Winchester Short Magnums. This tool allows you to quickly sort brass or check the dimensions. If you have a bucketful of mixed pistol brass this can save you hours of tedious work with calipers. You can also quickly check case lengths to see if it’s time to trim your fired brass.
If you load a wide variety of calibers, or do a lot of pistol shooting, we think you should pick up one of these Lyman Case Gauge templates. They are currently available for $24.99 at Brownells, $26.99 at MidwayUSA, and $34.68 on Amazon. The E-Zee Case Gauge has long been a popular item for hand-loaders.
NOTE: For years the E-Zee Case Gauge had a silver finish with black lettering, as shown above. Some of the most recent production of E-Zee gauges have a new “high contrast” look, with white lettering on a black frame. You may get either version when you order online — Brownells and MidwayUSA show silver, while Amazon shows black. We actually prefer the older silver version. Below is the black and white variant.
Lyman Case Gauge Should Last a Lifetime
Easily measure the case length of over 70 popular rifle and pistol cases with Lyman’s E-Zee Case Length Gauge II. This really is a “must-have” piece of kit for any gun owner who hand-loads numerous pistol and rifle calibers.
This precisely-made metal gauge makes sorting or identifying cases fast and accurate. The template is machined with SAAMI max recommended case lengths. Made from metal, with no moving parts, the E-Zee Case Gauge should last a lifetime. The Lyman E-Zee Gauges offered by Brownells are silver with black lettering, while other Case Gauge models are black with white lettering.
Here’s a cool way to save money — but you need to act quickly. Today — October 20, 2026 — Powder Valley Outdoors is offering FREE SHIPPING on orders over $99.00. So if you need powder, primers, bullets, brass, ammo or other products (including reloading gear), head over to PowderValley.com and take advantage of this special ONE-DAY Only deal on 10/20/2026!
NOTE: In addition to today’s FREE Shipping offer, Powder Valley is currently offering FREE Hazmat on qualifying orders of $599.00 or more. NOTE: This is a completely separate deal from the 10/20/26 one-day FREE Shipping offer. But it can save you $25 or more with a large order of powder and/or primers.
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 — Fall Clearance SALE and Major Discounts
⏺️ » Deals on optics, ammo, guns, tools plus 30% OFF with CODE FALL30
Brownells is running major discounts now with a fall clearance sale. There are good deals on optics, gun components, ammo, reloading gear and much more. Visit Brownells’ Sale and Clearance Page to access hundreds of deals. And you can then save an additional 30% with Code FALL30. On the Fall Clearance landing page you can navigate by product type, and be sure to use Code FALL30 to get 30% savings off the listed price.
MidwayUSA — Waterfowl Hunting Sale — Guns, Ammo, Carry Bags
⏺️ » Deals on shotguns, ammo, hunting gear, + Free Shipping $100+ Orders
If you’re getting ready to head out to the marshes, check out the waterfowl hunting sale at MidwayUSA. You’ll find great deals on shotguns, camo gear, and high-quality waterfowl hunting ammo. They have everything from shotguns to shells to gear to keep you warm and comfortable all at low prices to save you some money. In addition, MidwayUSA is now offering FREE Shipping for orders over $100.00.
As an Amazon affiliate, this site can earn revenues through sales commissions.
Federal Ammunition has released a new version of the Federal Ballistic AE App to assist shooters and hunters. The updated Advanced Edition (AE) App features a modern interface with enhanced navigation for a better user experience in the field. The HUD and DOPE charts are combined in a single workspace, with real-time trajectory information and manual data adjustments in wind direction, speed, and range.
Powered by the JBM Ballistics computer, Ballistic App is a respected ballistics calculator for iOS devices. This app calculates trajectory, windage, velocity, energy, lead, and bullet flight time for any valid range. Ballistic AE can compensate for atmospheric conditions such as temperature, barometric pressure, humidity, altitude and more. The App has a library of more than 800 projectiles and factory loads, with G1/G7 BC data, as well as advanced features including a mil-dot and MOA rangefinder, GPS and atmospheric reporting, full-size charts, and a precision target log.
The refreshed Ballistic AE App is designed to help long-range shooters and hunters hit more consistently with real-time aiming and scope adjustments available at their fingertips. Federal Marketing V.P. Jason Nash states: “This new and improved mobile app provides a better user experience [with improved accuracy].”
The Federal Ballistic AE iOS ballistics calculator is designed to provide accurate trajectory, windage and velocity for Federal, Remington, Fiocchi, and Speer projectiles. App users will find their favorite cartridge types including virtually all new modern cartridges and Federal’s new Peak Alloy products 7mm Backcountry and 6.5 Creedmoor +Peak. The App also employs GPS-aware precision tools to help provide more accurate trajectory predictions in the field.
Federal states: “This new version of the Ballistic AE App gives hunters and shooters the modern tools they need to perform at their peak in the field and on the range.” Full information on the new Ballistic AE App can be found at Federalpremium.com. Users can download the App for FREE from the Apple App Store.
Yes Hunters Should Protect Their Hearing
According to Dr. William W. Clark, the current Director of the Washington Univ. School of Medicine’s Audiology/Communication Sciences Program, a “serious threat to hearing comes from recreational hunting or target shooting”. This is in large part due to the fact that many people choose not to use traditional hearing protection devices like earplugs and earmuffs because they want to be able to hear their surroundings. Multiple studies have found that between 70 to 80% of hunters never wear earplugs or earmuffs, and nearly half of all target shooters don’t consistently wear traditional hearing protection. Thus, it should come as no surprise that for every five years of hunting, hunters become seven percent more likely to experience high frequency hearing loss.
We recommend that hunters carry quick-insert plugs on a cord around your neck. These can be quickly deployed when you are getting ready to shoot. Or, get a lightweight neck band with earbuds, such as Howard Leight Quiet Band QB1HYG, Sellstrom Band, or 3M Safety Band, all with good Noise Reduction Ratings of 25 dB or higher. You can keep these lightweight bands around your neck for quick deployment.
The Risk of Hearing Loss
Hearing loss can be progressive and irreversible. If you are a shooter, this is serious business. As the NRA Blog cautions: “You may not even realize you’re harming your hearing. Hearing loss occurs gradually, and can go effectively unnoticed until symptoms become severe. By then, the damage is done. Effective hearing protection is a must whenever you are shooting firearms or when you are in the vicinity of gun-shots.
For ultimate protection, we recommend a good set of tapered foam earplugs, topped by ear-muffs. However, there are situations when you may prefer lighter-weight hearing protection that can be quickly removed. For example, if you are standing well behind the firing line as an observer, or if you are working as a rangemaster or waddie some distance away from the shooters.” Good muffs or plugs will reduce sound by 23 to 33 dB.
Look and be amazed. What you are seeing is the smallest 5-Shot group ever shot in 1000-yard competition. And it is also perfectly centered for a 50-5X max score, yes ALL Xs. Brilliant! This amazing group was shot by Mike Wilson in July of 2018 with his 17-lb Light Gun, chambered for a 6mmBR wildcat he calls the 6 BRAW (BR Ackley Improved Wilson). This spectacular feat of accuracy demonstrates the potential of the 6BR family of cartridges even at 1000 yards. For his record group, Mike shot Vapor Trail 103-grain bullets in Lapua 6mmBR fire-formed brass. He loaded Hodgdon H4895 powder with CCI 450 primers. The action was a BAT, the barrel a Brux.
The Best 5-Shot 1000-Yard Group in History
Story based on report by Sam Hall
Look at that target by Mike Wilson. This is one of the most remarkable displays of accuracy (and precision) in the history of long range shooting. This past weekend, Mike (aka “GA. Dawg” in our Forum) drilled a truly spectacular 1.087-inch, 5-shot group at 1000 yards, all centered up in the X-Ring. Yes, you read that right, a group barely over an inch at 1000, shot in competition at an official IBS benchrest match on July 21, 2018. Note, the group was measured at the range at an even smaller 1.068″ (see target). However, as certified by the IBS as a IBS Light Gun World Record, the group is listed as 1.087″.
How small is that in angular measurement? Well 1 MOA at 1000 yards is 10.47 inches, so Mike’s 50-5X masterpiece is 0.1038 MOA! Yes that is an IBS group size AND score World Record. And it is also smaller than the current NBRSA 1000-yard 5-shot LG world record, 1.473″ by Bill Schrader in 2002. This best-ever 1K group* was shot at an IBS registered 1000-yard match at Hawks Ridge Gun Club in North Carolina. Other records have been shot at Hawks Ridge in the past, but this is the most jaw-dropping.
Sam Hall (left, green shirt) holds record target by Mike Wilson (right, white shirt).
Sam Hall, past IBS National Champion and IBS 600-Yard Shooter of the Year, was stunned by Wilson’s accomplishment: “This is a truely awesome marksmanship feat — one of the best in history. I think I would trade all 14 of my 600-yard records for that one!”. Mike’s amazing target will be submitted for approval as new Group Size and Score IBS World Records. Official approval is pretty much a certainty. The previous 5-shot, 1000-yard IBS record is 1.397″ (50 score) by Tom Sarver in 2007. (The NBRSA 1000-Yard 5-shot LG record is 1.473″ by Bill Schrader in 2002.)
Posting on our Shooters’ Forum, Mike wrote: “Thanks everyone for the kind words. As humbling as this game is, when it comes together makes it all worthwhile! A very special THANK YOU to my traveling buddy, my son, Blake, and my wife Debra for allowing me to enjoy this crazy game.” Mike also wanted to thank his smiths and component suppliers.
Mike Wilson IBS 1000-Yard Light Gun Specifications
Action: BAT ‘B’ 1.550 Melonited Action with Jewell Trigger
Barrel: Brux HV 28″ Finished Length, 1:8″ Twist Rate
Chambering: 6 BRAW (6mmBR Ackley Improved Wilson), Chambered by Darrell Jones
Chamber Specs: 0.272″ No-turn Neck with 0.135″ Freebore
Stock: Shehane ST 1000 Fiberglass Stock (with stock work by Larry “Bullet” Archer)
Optics: Nightforce 12-42x56mm Benchrest NP-2 DD
LOAD Specs: Lapua 6mmBR brass (formed to 40° Ackley Improved), Vapor Trail 103gr bullets, Hodgdon H4895 powder, CCI 450 primers.
Leonard Baity front rest with Protektor Bag. Italian Lenzi bag in rear.
World Record-Setting Cartridge and Load
Mike was shooting a 40-degree Improved version of the 6mmBR Norma cartridge. Long popular with Benchrest and 300M shooters, the 6mmBR was the original inspiration for this website. Yep, we started as www.6mmBR.com. The Improved version has extra capacity, allowing about 100 FPS more velocity when chambered with a long throat. For his record group, Mike shot Vapor Trail 103-grain bullets in Lapua brass. He loaded Hodgdon H4895 powder with CCI 450 (small rifle magnum) primers.
Praise from Fellow Competitors
Here are some reactions to Mike’s amazing group by our Forum members:
“Amazing target Mike Wilson! Your group might last forever as ‘the goal’ of 1000-yard Benchrest! Heck that’s a great target even at 600 yards.” — Mike J.
“Think about this for a second. That group was barely larger than the size of your index finger’s first digit and he printed it at 1000 Yards.” — Carlos
“Unbelievable!! Doing that under chosen prime conditions is an amazing feat but to do that in competition and to have everything to come together is just unbelievable. Amazing how far skill, precision, knowledge, and the products of this sport have come. Never thought we would see a group this small and well placed especially in the hills of North Carolina where the wind always blows. Congratulations. A true lifetime achievement.” — Yote Hunter
“I think that one will stand for a while. Hard work does pay off, but it don’t hurt to be one of the givers in the sport. Mike, you are ‘The Man’!” — Bill Shehane
“Awesome, awesome. Now the goal is to shoot UNDER an inch!” — Alex Wheeler
The 6mmBR Ackley Improved
Mike Wilson shot his spectacular group with a 40° Improved version of the 6mmBR cartridge with less body taper than a standard 6BR — the design is 0.463 at the body/shoulder junction (vs. 0.460 for standard 6BR). Mike calls his version of the 6BR Ackley a 6BRAW (“W” for Wilson). Sam Hall explained: “The 6BRAW is pretty much the same as a 6BRA or 6BR-AI (Ackley Improved). I sold the reamer to Mike last year. This has a 0.272 ‘No-Turn’ chamber with a 0.135 Freebore”.
This photo shows a 40° 6mmBR Ackley Improved (6BRA), as used by Tom Mousel in Deep Creek, Montana. Mike Wilson’s 6BRAW may be very slightly different. For Mousel’s 6BRA with 28″ Krieger barrel, the accuracy node is about 2980-2990 fps, so this gives up only 30-50 fps compared to typical Dasher velocities. Mike Wilson’s load runs about 2980 fps also.
In the past couple of years, the 6BR Ackley-type cartridges have been hugely successful in 600-yard and 1000-yard Benchrest. Sam Hall notes: “This year the little 6BR-AI has shot the smallest groups ever fired in 600-yard and 1000-yard competition. Back in April 2018, bullet-maker Bart Sauter, using a 6BRA, shot a 0.311″ 50-score 5-Shot group at 600 yards.” (Read Sauter Story). Bart’s stunning 0.05 MOA group is now the 600-yard IBS HG World Record.(Note: Bart’s target was originally measured at 0.282″ but was later IBS-certified at 0.311″.)
Mike used an Italian Lenzi rear bag. Mike says the super-slick nylon on the ears of this high quality rear bag make for better tracking. The ears provide support but don’t “grab” the stock, reports Mike.
More Comments by Fellow Shooters:
“Truly an amazing feat. The 5X was the icing on the cake! Many shooters would be very happy with that group size at 200 yards.” — Mr. Zero
“Words cannot adequately express how many of us feel about your magnificent accomplishment at 1000 yards. Congratulations — that is terrific!” — Gene Beggs
“Truly amazing … well done on a great achievement… RESPECT!” — Elardus
“Bravo Mike pour ce tir incroyable. Ton exploit est sur le forum de tir longue distance en France bonne continuation.” — Frederic Riso
* There are two North American sanctioning bodies for 1000-Yard Benchrest, the IBS and the NBRSA. The previous 5-shot, 1000-yard IBS record is 1.397″ (50 score) by Tom Sarver in 2007. The existing NBRSA 1000-Yard 5-shot Light Gun record is 1.473″, shot by Bill Schrader in 2002.
Here is a simple technique that can potentially help you load straighter ammo, with less run-out (as measured on the bullet). This procedure costs nothing and adds only a few seconds to the time needed to load a cartridge. Next time you’re loading ammo with a threaded (screw-in) seating die, try seating the bullet in two stages. Run the cartridge up in the seating die just enough to seat the bullet half way. Then lower the cartridge and rotate it 180° in the shell-holder. Now raise the cartridge up into the die again and finish seating the bullet.
Steve, aka “Short Range”, one of our Forum members, recently inquired about run-out apparently caused by his bullet-seating process. Steve’s 30BR cases were coming out of his neck-sizer with good concentricity, but the run-out nearly doubled after he seated the bullets. At the suggestion of other Forum members, Steve tried the process of rotating his cartridge while seating his bullet. Steve then measured run-out on his loaded rounds. To his surprise there was a noticeable reduction in run-out on the cases which had been rotated during seating. Steve explains: “For the rounds that I loaded yesterday, I seated the bullet half-way, and turned the round 180 degrees, and finished seating the bullet. That reduced the bullet runout by almost half on most rounds compared to the measurements from the first test.”
Steve recorded run-out measurements on his 30 BR brass using both the conventional (one-pass) seating procedure, as well as the two-stage (with 180° rotation) method. Steve’s measurements are collected in the two charts above. As you can see, the run-out was less for the rounds which were rotated during seating. Note, the change is pretty small (less than .001″ on average), but every little bit helps in the accuracy game. If you use a threaded (screw-in) seating die, you might try this two-stage bullet-seating method. Rotating your case in the middle of the seating process won’t cost you a penny, and it just might produce straighter ammo (nothing is guaranteed). If you do NOT see any improvement on the target, you can always go back to seating your bullets in one pass. READ Forum Thread.
Is your well-built rifle of high-quality components plagued with vertical fliers across more than 1-3 handload combinations? Consider the bedding, crown and scope/sight mounts. Are they correct? If so, then you might check for ignition issues before boldly undertaking an extensive, expensive, and quite possibly fruitless quest for the “magic handload”.
Here’s a simple solution for lumpy front sandbags. Cut a small block the width of your fore-end and place that in the front bag between matches. You can tap it down firmly with a rubber mallet.
Lyman’s popular 
