AR-15 Fliers, Part 2

Last month we said that two of the most common causes of fliers are gas tube misalignment and ammunition issues. We’ll begin by jumping into imperfections in cartridge concentricity which is a major cause of fliers in any rifle or pistol. Our goal is to send bullets straight into the back of the barrel. If cartridge concentricity is compromised, bullets are set at a slight angle in the neck. When fired, they will enter the back of the barrel at an angle and deform.

It is possible to measure the runout using a gauge like the Hornady Concentricity Gauge (Hornady #050076). Runout is present in both factory and handloaded cartridges. Rifles vary in their tolerance to runout. Generally, guns jumping bullets further, either because they were chambered with long freebores or have eroded throats due to high round counts, will exhibit the lowest tolerance to runout.

As a general rule, I don’t like to see competitors using ammo that has The Hornady gauge on the right can also straighten bullets that have been seated at an angle. anything over 0.003" of runout. The Hornady tool will also allow the user to actually straighten bullet alignment. Gauging ammunition, rounds with high runout that are straightened should be separated and tested to note any differences from those that started straight.

I am abbreviating this topic of concentricity by including some target scans that speak for themselves. A more thorough discussion is in my April 2016 and December 2018 articles. Pay attention to how the thickness of the brass in cartridge cases vary from side to side. This can cause bullets to seat at an angle in cartridge necks. It can also cause bullets to tip as they are leaving the cartridge and making their way into the back of the barrel.

Some remedies for this are offered in the articles and applying them can lessen fliers by a bunch. As you are gauging ammo for concentricity, take a few minutes to look at the rims of the cases for tears and deformations. The AR-15 as originally designed with a standard 20" barrel is not normally hard on case rims, although a rough chamber can exacerbate extraction. My September 2014 article on chambers described a simple and quick method to polish chambers.

Don’t forget to use a chamber brush in your daily cleaning. If you area handloader, be sure to tumble your brass to remove surface crud that can make extraction more difficult. Soft brass is another factor that can result in torn casing rims. I blamed soft Nosler brand brass for rim deformation in an article on the 22 Nosler published March 2019. I remembered guys bad mouthing Federal 223 Remington cases back in the day for poor primer retention and torn rims.

I have not used Federal brass in the 223 Remington in decades but I did find Federal and Starline brass to be too soft when testing the 224 Valkyrie. Dwell Time We saw a marked uptick in ripped casing rims when shorter barreled ARs started becoming increasingly more popular. The reason for this is the location of the gas port. For awhile, there was a tendency to move the gas port back toward the chamber in connection with shortening the overall length of carbine barrels.

Taking that approach influences the timing of extraction. The closer to the chamber we locate the gas port the sooner gas is going to reach the bolt and begin unlocking and extraction. The original timing of 20" barrels allowed chamber pressure to drop and cases to begin to "spring back" toward their original size, creating the clearance with the chamber enough to allow easy extraction.

With carbine gas ports located closer to the chamber there is a tendency to start extraction before casings have had time enough to begin to "spring back" to a smaller diameter that won’t grip the side walls of the chamber, making extraction more difficult and causing torn rims. Gunsmiths have gotten smarter about this gas

port business recently and we are seeing a lot of builds with the gas block well forward of where we saw them a couple of decades back. I discuss this with customers wanting a short barrel build. On all the barrels that I stock in 26" to 32" I move the gas port 2" forward than normal and get longer gas tubes to match from White Oak. That extra 2" delays extraction and rims remain pristine. We are trying to increase dwell time, which is the amount of time that the bolt remains locked up when around is fired.

In times past there used to be bolt carrier weights inserted in the back of the bolt carrier to delay opening. Unfortunately, I don’t know of a current supplier but you may still find them. My study of these indicate they likely influence barrel harmonics and, therefore, can open groups or tighten them. For proper semi-auto function a slight modification to the buffer is called for in the instructions. The weights can also move point of impact so continue using them in order to hold zeroes.

So why do deformed case rims cause fliers? We want to send bullets straight into the back of the barrel every time the gun goes off. In order to accomplish that we need to seat bullets in line with the center axis of its cartridge casing. Then we must center the entire cartridge in the chamber, requiring the case head to rest flat on the bolt face. Tears in case rims normally go to the rear, creating high spots that will contact the bolt face and cause the entire round to cock in the chamber.

These gas gun chambers are not nearly as tight as some folks envision. I often find 0.003-0.007" of slop between a loaded round and the side walls of chambers. That much clearance allows rounds to cock at a significant angle away from the bore of the barrel. Far The top group, with two nasty fliers, was fired with ammo that was selected at random. The group on the bottom was fired with ammo from the same box selected for less runout.

I prefer to buy quality brass, locate gas ports to lengthen dwell time, or use bolt carrier weights so I don’t have to deal with torn casing rims. That said, if you have some deformation to rims in spite of your efforts, handloading technique may help. Most folks loading for gas guns full length resize to enhance function. For hand-fed slow fire, this isn’t necessary and creates slop. When a cartridge is fired in a chamber it expands outward until the walls of the chamber stop the expansion.

Then the casing walls spring back about 0.001" to easily extract and can be reloaded without being fully resized. The neck will obviously need to be sized back to have enough tension to hold anew bullet and the shoulder will need to be bumped back by about 0.003". A neck sizing bump die accomplishes this. Key here is to only use brass fired in your chamber. Accidently using other cases will likely create a jam. Mark your cases and/or primers for easier identification.

My machine rest tests show that groups fired with neck sized brass will average 16% tighter than groups with fully resized brass. Obviously, magazinefed ammo needs full resizing.

Soft Seating Bullets Some shooters competing in slow fire events who use bolt action rifles soft seat bullets. Cases are neck sized to result in low neck tension and bullets are seated a little longer than chamber length. The bolt is used to slowly push each round into the chamber. There will be no resistance to this forward movement until the long-seated bullet comes into contact with the back of the throat of the chamber. The shooter continues to push forward with the bolt.

While doing so the neck of the casing is riding up over the back of the bullet and the front of the bullet is simultaneously jamming tighter into the throat. Eventually a point will be reached where the bolt can be cammed down into its locked position. So far, so good, right? Perhaps, but if circumstances change the shooter may find himself in trouble. Let’s say a cease fire is called.

Removing the chambered round extracts the case with the bullet remaining stuck in the throat, dumping propellant in the action and/or magazine. These same issues will take place if the firearm is a gas gun but a soft seat is more difficult as the AR bolt is held to the rear against heavy spring pressure by the bolt catch. When the shooter normally lays the cartridge on top of the magazine follower and trips the bolt catch, the released carrier slams the round into the chamber.

I call this hard seating and it ends up resulting in fat groups with a lot of bad fliers. See accompanying target scans. Seating Sweet Spot Every centerfire rifle I have ever tested had a specific bullet seating sweet spot where groups are tighter and fliers fewer. This is gun specific and has to be worked out on a test range by shooting groups. Before heading to the range, establish the "Length To Lands" for the specific chamber.

This requires a tool such as a Hornady Overall Length Gauge These groups were fired in the same gun. or Dead Center Sports Length To Lands Gauge. They both need a caliber-specific dummy case that screws onto the front, a caliper, and a comparator made which fits to one leg of the caliper. A caliberspecific Bullet Insert fits in the top of the comparator. My June 2016 article "Bullet Seating Sweet Spot" details how to use these tools to arrive at the length-to-lands setting for your chamber.

Dead Center Sports has an online video (You Tu. be/BA3Sv0TB_1M) detailing how to use their gauge. Side note, if you experience a lot of variance in your length to lands measurements this may be a clue that cleaning rod flex has damaged the starting points of the lands just in front of the chamber. I discuss this next month along with what you will see in the bore scope.

With boat tail bullets your bullet seating sweet spot will end up being just short (0.000-0.010") of your length-to-lands with your ammo shorter than your chamber and bullets jumping a few thousandths before touching the lands. The bullet seating depth that you arrive at initially will remain sweet for the life of the gun and it doesn’t require updating as the throat erodes forward. Very Low Drag (VLD) bullets normally want to be jammed a little into the throat, up to 0.010".

This means that you load the ammo just a little longer than your chamber. The challenge with VLD bullets is that as the throat erodes forward the shooter must take more lengthto-lands readings and lengthen the ammo so the bullets jam into the throat by the same amount or suffer expanding groups. Most of us developing a bullet seating sweet spot end up with a bullet seating die setting where the sweet spot occurs. However, not all ammo seated at that die setting will measure the same in length.

Some folks question how this can happen if the die is not moved. The short answer is that variables other than

A. L (Over-All Length) Gauge on the bottom. the seating die can conspire to vary the final lengths. The thickness of the brass at the neck can vary by quite a bit. Necks that are thicker will resist bullet seating more, resulting in longer ammo. Outside neck turning may help this some and also may result in bullets seating straighter in line with the casing. This concentricity results in tighter groups and less fliers. Gunpowder is another culprit that can cause variations in final cartridge lengths.

Most shooters developing ammo for use in long range events use stick powder which normally fills the case more than ball powders. If the powder comes up close to the case neck it can resist bullet seating, resulting in longer ammo.

As stick powder is poured initially through a normal powder funnel into the case, there are variations between rounds in the way the powder packs, resulting in differences in the levels of powder making the seating resistance from Far Always use a match bullet seating die (right) to improve concentricity. one round to the next vary. In the case of powders coming up close to the neck, seated bullets cause such charges to be compressed. A longer drop funnel is recommended to pack powder uniformly.

Packing powder can also influence the straightness with which bullets seat in the necks. If the top of the powder on one side of the case is taller, the bullet will meet more resistance to seating on that side and may end up cocking in the neck and creating runout. Brass brand also affects how powder packs. Some brands average thicker case walls and those hold less powder, making powder levels higher. In general, Western Cartridge Company and Lapua brass are thicker than Lake City and Winchester.

Chambers also have a big vote in bullet seating. A chamber with more free bore will result in bullets seating out further so the bases of such bullets meet less resistance from the powder to seating. Unfortunately, this chambering occurs at the "birth" of the gun and is not normally a repair option. So, we as gunsmiths need to spend a few moments with our customers before we supply a barrel so we know what disciplines the gun is intended to be used and what bullets the owner intends to fire.

There are minor variations in the shape of even the best match bullets that can also contribute to differences in seating. You can observe this very easily using the caliper with the comparator and proper bullet insert. Run the front of the bullet into the insert, then close up the other leg of the caliper on the bottom of the bullet and take a reading. Repeat this process with several bullets out of the same box and you will notice some variance. This all points to slight variances in the ogive.

Quality match bullet seating dies do not come in contact with the actual tip of the bullet. There is a hollow stem inside the die that makes contact with the bullet ogive. So, variances in ogive dimensions result in variances in seating depth. I have known of some very serious handloaders ac-

tually sorting their bullets by base to ogive dimension attempting to achieve greater uniformity and higher precision. Ammunition, handloads and factory, all varies in length. I employ all of the tips described with the exception of sorting bullets and outside neck turning. Out of a 10-shot group I will have typically have one or two rounds going 0.002" long and a couple going 0.002" short with the rest measuring closer. Occasionally, I’ll measure one round in ten varying measuring up to 0.003" off.

How much this matters is gun and bullet specific. Most AR- 15s will allow errors of +/- 0.001" from the actual bullet seating sweet spot. Other ARs may tolerate or be only minimally degraded by rounds 0.002" off. Many guns will show differences with ammo 0.003" or greater off sweet spot length. How do gun owners know if their gun/ammo combination is shooting fliers caused by ammo being seated I prefers using a Bob Sled single round loading device instead of a magazine when shooting single fed rounds.

AR-15 (second from left), AR-10, and 22 Long Rifle exert no pressures. longer or shorter than optimum? The answer involves leaving the confines of a nice air conditioned building and venturing to a hot, dusty range. Shudder to think! The range testing needs to be conducted on a wind free day so we can isolate variables. Begin by using the caliper with the comparator and bullet insert in place on one leg.

Place the bullet of each cartridge into the bullet insert and bring the other leg of the caliper into firm contact with the casing rim and take the reading to within a half thousandth of an inch (0.0005"). Compare your cartridge base to bullet ogive readings Then close the bolt and fire the round normally. to the sweet spot length that you established when you determined your bullet seating sweet spot during previous range sessions. Mark or segregate rounds that are off by 0.003" or greater.

Using whatever procedure you normally employ for ammo testing (likely a bench rest with sand bags) shoot a five round group with ammo measuring within 0.002" or better and include one round at 0.003". When selecting that +/- 0.003 round make sure you are also measuring the concentricity of the cartridges you are considering. Select a 0.003" excess-length round with low bullet runout (0.002" or less) to avoid an additional confounder. For the test to be valid extraneous variables must be kept to a minimum!

Note the impact of each of the five shots using a quality spotting scope and note where the 0.003" round falls in relation to the other four. If any doubts exist, shoot a second group for clarification. If the rounds that where off by 0.003" from your sweet spot cause no fliers, that is good news! On the other hand, if the 0.003"+ rounds caused fliers, that calls for another round of tests. Shoot 4 shots that are either spot on or +/- 0.001" and then the fifth shot at +/- from the

sweet spot to see if there’s a noticeable change. If your range tests indicate that your gun/ammo combination is sensitive to rounds either +/- 0.002- 0.003" outside your optimal sweet spot length there are ways of dealing with this. One of the simplest solutions is to measure all your rounds as previously described and cull out ammo that measures too long or short. Why would you deliberately shoot around that you know before hand is going to cause a flier?

The obvious question then becomes what are you going to do with the culls? The second method takes a little more time but results in some stellar quality ammo with zero culls. Turn the micrometer dial on your match bullet seating die up 3 notches from your normal sweet spot setting. If you are using boat tail bullets that do not require chasing the throat, you can seat a box of ammo for the next day or seat a whole case for the season.

If you are using VLD (Very Low Drag) bullets that mandate chasing the throat, you can only seat enough ammo for use the very next day because your seating length for the following day gets longer due to the amount of throat erosion created each day you fire the gun. The following instructions pertain only to boat tail bullets. After your initial seating with the +3 tick mark die setting (each tick mark should move the bullet about 0.001") measure all the rounds you seated.

Any rounds that measure either +0.0005" longer than your C.) when they are permitted to lie in a hot chamber before being fired. previously-established seating sweet spot or rounds measuring exactly dead on your sweet spot get a pass and are boxed for future use. Now you will come down one tick mark on the die to +2 and seat a second time all of the rounds that failed the first measurement. Remeasure all cartridges and accept, as before, all that now are either +0.0005" or spot on and box for later use.

Come down another tick mark to +1 and reseat all rounds that failed previously, remeasure and cull as before. Continue these same steps until all ammo has passed and been boxed for future use. This may sound like a very time consuming process but it only takes me a couple of hours to seat and measure an entire case of perfectly-seated ammo. Some bullets are more demanding regarding the sweet spot length than others.

Heavy boat tail .224 caliber bullets commonly used by shooters from 600-1,000 yards such as the 80 and 90 grain Sierra Match Kings and the Berger 80.5 and 90 grain boat tails are usually more forgiving. VLD bullets, on the other hand, are normally much more demanding and will not tolerate ammo loaded either much short or long. The most demanding bullet I have found is the new 95 grain Sierra HPBT Match- King. If you miss your gun’s sweet spot by even 0.002" you will likely see degraded performance.

If you fire around with these bullets that misses the sweet spot by either +/- 0.003" you can expect a nasty flier. Once you have established the sweet spot of your particular rifle for the 95 grainer I strongly recommend you follow the above seating plan or you will suffer many fliers and quite a few of them will be severe! The high ballistic coefficient (.600) of this bullet is attractive but it doesn’t come cheap in terms of labor.

Regardless of how you seat your bullets when feeding cartridges into your AR in slow fire events I strongly recommend using a Bob Sled single load device which has no spring or follower, just a trough at the top to allow the shooter to lay in around. Once you have done that, don’t release the bolt catch to slam the cartridge along distance into the chamber. Instead, insert your finger into the ejection port and push the round fully forward, then release the bolt.

This promotes more uniform positioning of the round in the chamber and my studies indicate it will shrink slow fire groups by a very substantial 13.8%. Bullet Tips The quality/precision of bullets varies by the factory in which they are produced. Berger and Sierra win most of the matches at Perry and they are also the choices of most military shooting teams whose pockets are deeper than most of ours.

I have found that bullets from other makers normally shoot bigger groups and more fliers when tested in my machine rest. The tip of the bullet seems to also be important to group size and fliers. Bullets with an open meplat (hollow point) seem to shoot tighter groups with less fliers than bullets with plastic or some sort of polymer tips on their front ends. The tipped bullets advertise a higher ballistic coefficient but in my mind that is a poor trade off when they also produce fatter groups and fliers.

A topic related to the above is "pointing" of bullets either by individuals or at the actual bullet factory. Bringing the front of the bullet to a nice, even, well-defined point does increase its ballistic coefficient by a significant amount.

My understanding is this process began as a hand operation, with the bullet to be pointed inserted into a die-like pointer tool, which pretty much closed up the hollow point. When these pointers came on the market one of our Team shooters bought one. The bullets looked very nice, so we loaded some for testing by shooters and via machine rest. Testing showed the pointed bullets produced fatter groups with more fliers, along with higher pressure and some blown primers.

Shooters reporting from the field made the same observations. I measured the diameters of unmodified bullets and compared them to the average diameters of pointed bullets. The pointed bullets averaged 0.0003" wider! So, something in the pointing process was putting some stress on the rest of the bullet. When one of my shooters wrote growling about blown primers from the ammo with the pointed bullets I asked him to measure the diameters of 10 pointed bullets and compare their average to that of regular bullets.

With no prompt or hint from me, he reported back with the same 0.0003" difference. Talking to experienced bullet pointers since that incident has helped to educate me. Those folks said that our team member simply needed to back off a little on his aggressive pointing and accept just a little less point. In fairness to him this was his first attempt at pointing.

If you are inspecting a customer’s ammo and the bullets are pointed you might ask the customer if he bought the bullets as pointed at the factory or if he pointed them himself. If the pointing was a "do it yourself" project I would test against non-pointed bullets. Some bullet factories are doing limited pointing in house as the bullets are made. The Sierra 90 grain Match King boat tail is factory pointed and they are getting it right. No fliers and a very high B. C.!

Heat and Powder Many of us who shoot High Power, F Class, or Palma have experienced this. These disciplines all have long distance slow fire precision events normally shot from the prone position. A string of fire is often 20 rounds fired for record, usually with about one minute allowed per shot. Most shooters load their ammo fairly stout for these events. As you can well envision, barrels and their chambers all get quite hot during these strings.

Most shooters develop a sort of rhythm when shooting, although a host of distractions can commonly occur to interrupt, typically voluntarily waiting out a sudden change in range conditions. Quite frequently, if a shooter holds around in the chamber while waiting for issues to resolve, that round will go outside the group and the shooter’s call. This can often result in a substantial flier.

I conducted a study on this and wrote up the results in an article in my June 2017 article which included a target scan demonstrating this. Heated ammunition changes muzzle velocity meaning "cooked" ammunition typically causes fliers. Best advice is to avoid keeping around in the chamber long enough to heat up. If something causes a hold up in shooting, pull that round out and place it last in your firing queue, then rechamber a cool round and fire it normally when ready.

During long strings of fire keep your ammo shaded as direct sunlight will also heat up the cartridges. Changes in bullet brand or powder can cause issues. Most AR owners charge their magazines with one type of ammo. On the other hand, High Power competitors frequently shoot short line (200 and 300 yard stages) with magazinelength ammo and switch to longer ammo with heavier bullets for 600- 1,000 yard slow fire shooting.

The 200 and 300 yard ammo frequently consists of either a Sierra 77 grain Match King or a Berger 77 with some sort of ball powder as the propellant; long line ammo typically uses a Sierra or Berger 80 or 90 grain boat tail because these fight wind drift better. Some sort of stick powder is normal for this ammo. When making these ammunition changes some High Masters noticed that a flier or two was common immediately after the switch.

I had heard about these component-induced fliers and started watching for them when operating my machine rest. The machine rest allows me to make more accurate assessments of the problem than anyone could hope to do when shooting off the shoulder or from a bench. I do see the tendency for this and the severity varies between guns as one might expect. The severity also varies according to whether one variable is changed or two.

Let’s say you shoot a Sierra MK 77 grain bullet with some sort of ball powder at the short lines, then switch to Sierra 90s with a stick powder for 600. You have changed only one component which is the ball powder versus stick powder. Another shooter may also use 77 grain Sierra bullets with ball powder at the short lines but uses a Berger 90 B. T. with a stick powder. He has changed both bullet brand and powder type.

Likely any fliers that he may see immediately following the ammo switch will be more severe than the first case when only the powder was different. Concluding this topic, I think that, for the most part, this variance is often being overstated. Even when making a double component switch (both the bullet brand and gunpowder differences) I seldom see the first round impacting more than one minute of angle outside the remaining nine shots of a group.

Feel free to email me at NCC1701@ penn.com to discuss this or any of the articles I’ve written. AG