Sierra’s New Match King

Sierra redesigned their 90 grain Match King boat tail bullet intended primarily for AR-15s used in Service, Match, and Palma rifle competition. This second generation corrects a decadeold design flaw. To understand how, let’s look at Stoner’s original design and how it evolved. Early AR-15s had a 1:14 twist designed for magazine-length 55 grain FMJs. Early reports from Viet Nam indicated the bullet turned sideways on impact, causing massive tissue damage.

Bear in mind that hot jungles were not the military’s only concern given a possible threat of Russian invasion. One scenario involved an attack through Alaska 224 90 grain Match Boat Tails (left) had the word "THICK" boldly printed on the boxes to assure shooters that they were blow-up proof. The early 2005 failed Sierra design, the newer improved pointed Sierra, and the Berger Thick Jacket on the right. and Canada.

Bullets fired in subzero temperatures launch at lower velocity and some studies revealed stability reduction, so the twist rate was changed to 1:12. A forward bolt assist was added to address function issues caused by inappropriate gunpowder used in early ammo manufacture. I carried an M14 during the first half of my Senior Trip to Viet Nam. We surrendered those old battle rifles and were issued M16s for the second half of my tour.

I had heard the reports of jams and felt uneasy about the substitution but kept my rifle reasonably clean and had no function issues. Knock on wood, or in the case of Viet Nam, bamboo! Later, the A2 was introduced. Designed to shoot a heavier and longer bullets, the twist rate was set at 1:7 with a NATO chamber which is sloppy and long to accommodate dirty battlefield conditions. Green tip ammo (NATO SS109/M855) is about the same overall length and fits standard magazines.

While lighter and shorter 55s will stabilize in either, the slower twists keyhole the heavier and longer bullets. Phase out of the older rifles was slow with reserve components with units holding onto A1s for years after active duty. Ammunition Supply Points had to inventory both bullets. As a Drill Sergeant, I was always relieved to draw the older M193 55s for qualifications. Even though 1:7 spun them twice as fast as necessary, the ammo proved more accurate than green tips.

Reserve components eventually switched and 55s slowly phased out. In addition to ammo, good shooting was also hampered by the A2’s trigger design. The A1 had semiand full-auto and in Viet Nam this was frequently overused, mostly leading to misses beyond the confines of room distances and needlessly reloading too often. Replacing this with a three-round burst in the A2 added a cam to the trigger that looks more like a gear in a clock.

The result of this over-engineering is a trigger that feels and actually gauges different for each shot, making it difficult for even seasoned marksmen to adapt to. The A2 rear sight was redesigned to be more friendly to marksmanship. Smart guys, such as Army Marksmanship Unit gunsmiths and John Holliger from White Oak, further improved this. As a military firearms trainer I was concerned with the reasons for poor qualification stats.

Some suggested this was a societal problem with the new generation not growing up around firearms. Add a firearm/ammo combination with

less-than-stellar accuracy in and the proficiency challenge increases. The military also shares the guilt and the Department of Defense places too much emphasis on testing and employing social theories instead of war fighting. I noticed this back when I was a Drill Sergeant and for the sake of our troops can only hope that things will change. The M16 replaced the M14 on the battlefield long before competitive shooters made the swap.

I remember vocal match shooters proclaiming the Mouse Gun would never outshoot the M14. Initially, I was one of them. Innovators at the Army Marksmanship Unit and civilians like Albert Turner and Frank White of Compass Lake Engineering found ways to improve the sights, take sling tension away from the barrel with float tubes, and install quality match barrels. Sierra and other makers did their part by offering more accurate bullets with higher ballistic coefficients to combat wind drift at longer distances.

The then-new 69 grain match bullets were normally seated to magazine length but could be seated longer to compensate for throat erosion in events allowing single feeding. Most folks wanted a match barrel with a decreased twist rate of 1:9 or 1:10 for shooting 69 grainers and similar match bullets of the era. While the 69 grain .224 bullets were an improvement, .30 caliber still held the wind advantage.

Once again, thank Sierra for coming up with their 77 grain Match King, Designed to be loaded to magazine length, it became the standard for 200 and 300 yard rapid fire. Some magazine-length .308s area little more wind efficient but come with higher recoil, which doesn’t serve well in time constraints. Sierra’s 80 grain Match King wasn’t designed to fit a magazine and needs to be seated longer but this isn’t an issue for slow fire.

Other manufacturers soon came up with bullets weighing between 73 and 82 grains attempting to duplicate Sierra’s performance. These improved bullets brought the AR-15 up to equal accuracy performance against the heavier recoiling and more expensive .308 rounds. The longer, heavier AR bullets required twists of 1:7.7-1:8. With the possible exception of 1,000 yard shooting, 1:7 is too fast. Over-spun bullets exacerbates any imperfection and results in bigger groups with no improvements in any other aspect.

Some believed 80 grainers were as far as the diminutive .223 Remington case could support but another smart guy proved that wrong. Jimmy L. Knox, who used a Very Low Drag design for several competition bullets, came up with a high ballistic coefficient 90 grain .224 bullet in his JLK line. All 90 grain bullets must be seated long and hand fed. Just as the AMU had been one of the innovators in developing the AR-15, they initially jumped on this new bullet around 2004.

It wasn’t long before one of their Mouse Gun shooters used this bullet to break a 1,000 yard Service Rifle record that I had set with an M14 and 180 grain handloads a decade prior. General shooter interest perked up by a bunch with that accomplishment! Berger added a VLD 90 to their inventory. VLD bullets require a high maintenance process called "chasing the throat" where constant throat measurement is needed to make adjustments to bullet seating depth.

Most shooters prefer to a boat tail bullet that can be seated to the same depth for an entire season rather than measure and likely make adjustments more often. As a military team armorer I found chasing the throat made VLDs a nightmare. Sierra came out with a 90 grain Match King in 2005 and many of us jumped on the green bandwagon. The bullet was hard to get initially and I finally had a supply and began load development in early 2006.

Using Sierra’s recommended muzzle velocity of 2,650 fps for 1,000 yard reliability, I began working up to that target speed with across section of the only barrels thenavailable in the recommended 1:6.5 twist. All of my barrels had Wylde chambers which allowed safely exceeding the scant loading data that was available for 90s at the time.

By the second range session I was safely approaching the 2,650 fps in virgin Lake City brass with factorycrimped primers, but I began losing bullets at about 200 yards down range due to jacket separations causing them to blow up in a little puff of smoke. I contacted Sierra and they still credit me as the first reliable source of blow ups with the original 90. Soon after almost everyone

Top Bottom trying the bullet suffered the same fate. Even worse, too many got the facts confused and wrongly thought all 90s were prone to blowing up. This misconception put the brakes on shooters wanting to try 90s and was compounded by Sierra leaving that original 2005 bullet design on the market for nearly a decade in its known-flawed condition. For the next couple of years after my initial failures, I experimented with every bore design I could.

I originally thought gain twist would cure this but couldn’t find a source for barrels at the time. I tried 5R, polygonal, evenand odd-numbered grooves, as well as cut and button rifling. No cure. Sierra told me later that most reported blow ups occurred with Krieger barrels. Having a taller 0.218" land, these likely constricted the bullet and raised pressure. Accuracy with other .22 caliber bullets is stellar with Krieger’s design.

Early on, I sat down with Krieger’s plant manager about these bullet blow ups but he was reluctant to change the land. Instead, he offered to deepen the groove from the industry standard of 0.2240 to 0.2245", assuring me this wouldn’t sacrifice accuracy or longevity while being easier on the fragile Sierras. The modification cut blow ups in half with no accuracy degradation but even one blow up is the kiss of death in a match. The AMU was also aware of the 90 grain problems.

The JLK line that had been so successful for them sold to Swampworks and there was a temporary lapse in production while the equipment was being moved and set back up. Instead of teaching their shooters to chase their throats, the AMU assigned their tech support to track of all the guns and keep up with the constantly-changing throat erosion. This had to be an enormous task and likely the reason they mostly confined 90s for 1,000 yards.

This high VLD maintenance proved burdensome and the AMU abandoned their 90 grain loads. This was around the time the general shooting public was being confused about which brands were really blowing up and why. Having the prestigious AMU drop 90s sent a message that was misinterpreted by many. Incidentally, I have never blown up a JLK or Berger 90 grain VLD. I approached Berger as they were already marketing a 90 grain VLD.

Like everyone, they had heard of Sierra’s problems and they figured the market for a quality match 90 grain bullet was there. They sent our Team a pallet of them to test. Berger and I had agreed a thick jacket would be key and the first boxes of their new 90 had "THICK" clearly displayed. The first thing I did was torture test the new bullet in all the rifling designs that the Sierra had failed in. The deeper groove also cut pressures but this still didn’t yield a Sierra-proof barrel.

Absolutely no blow ups and accuracy was great! The only issue I had with Berger’s new bullet was it pressured more than the Sierra. Krieger already demonstrated groove depth helped with a taller land and both Krieger and Bartlein offered this option, one I use to this day. By this time Bartlein was also offering gain twist barrels. After much research I settled on a starting twist of 1:13 in front of a Wylde chamber progressively ending with 1:6.5 at the muzzle.

All of these contributed to lowered chamber pressures and great accuracy. The new 90 grain thick jackets were offered but sales were rather tepid because of the confusion about blow ups. Shooters with fresh 1:8 barrels were reluctant to switch to a 1:6.5 twist that 90s require, especially when the new Berger 90 wasn’t yet vetted. The shooting community began to become reeducated to the benefits.

The Berger 90 boat tail with a ballistic coefficient 0.512 bucks wind with about 17% greater efficiency than the 80 grain SMK when loaded in a .223 Remington and arrives supersonic at 1,000 yards. Especially out of 20" Service Rifles, 80s are marginal there. Widespread 90 grain adoption was also hampered during the ammo buying frenzy a few years back, having Berger decide to furlough production of much of their line to focus only on back fill orders of their top sellers.

As a match-specific bullet, the 90s were temporarily halted. There was nothing wrong with these furloughed bullets and Berger still has the dies and equipment to tool back up for a run of their thick-jacket boat tails if sufficient demand warrants it. If you’re a fan, let Berger know! Because of this, shooters lacked a reliable 90 grain bullet. Around the

same time JLK was unable to obtain jackets for VLD and that bullet also went out of production. That left Berger’s VLD 90 grain as the only option, along with its high maintenance throat chasing. Today’s Situation I operate a Commercial Row store at Camp Perry during the CMP Service Rifle National Matches. During the 2016 event shooters mentioned they had heard Sierra finally fixed their 90 grain bullet, something I had urged them to do for years. I immediately reached out to Sierra, confirming the design change.

Having the new bullet in stock, I ordered a dealer drop shipment and was impressed. The bullet is factory pointed with a staggering 0.563 B. C., 24% more efficient than the 80, very high for a boat tail, and exceeding the Berger VLD. I’ve torture tested Sierra’s second generation 90 and haven’t yet had a single failure, including in the same barrels that routinely saw failures with the first generation design.

Accuracy is as good as the Berger 90 boat tail (I still have a supply.) Since then, I’ve performed load work ups with Berger and Sierra bullets for every gun I have built and provide a 20 round box of ammo with each bullet type when I ship completed uppers back to their owners. After performing their own tests, my customers are split on their preference. The Bartlein gain twist, Wylde chamber, 0.218×0.2245, 1:13-1:6.5 configuration that’s perfect for Berger 90s works equally well with the new Sierra.

I am achieving muzzle velocities around 2,600 with both in 20" Service Rifle barrels, 2,700 fps in 26" Match Rifles, and 2,800 fps in 30"+ Palmas. All three barrel lengths keep the 90s supersonic to 1,000 yards and are about equal to .308s of similar barrel length, all for much less recoil and cost.

The Canadians realized this earlier than us and have been using the two Berger 90s for Palma for some time, mostly in bolt guns with 30" barrels. "A Mouse On Steroids" by Robert Pitcairn ( Canadian Marksman Summer/Autumn 2012, goo.gl/RTg Tjm) and "Gain Twist Barrels For Palma" (American Gunsmith December 2016) discusses this but these were written before Sierra released their second generation design. Be careful when purchasing the new Sierra 90 at gun shows or from low volume dealers.

Both sources may have stocks of the older bullet. You can tell the difference in bullets by looking at the tips. The old bullet has a conventional open hollow point meplat and the new bullet is factory pointed. The only criticism that I can offer to Sierra regarding the new design is lack of active promotion, however, good word of mouth seems to be working in favor of the upgraded bullet and I am ordering more to meet demand.

Loading 90 SMKs There is nothing difficult about loading 90 boat tails, provided you can load 77s or 80s. You’ll need to know some specifics about your chamber. When only using one bullet seated magazine length, chamber selection is easy, as was the situation when 69 grainers were the only option. When shooters began using different bullets, things got more esoteric as chambers got longer.

A consequence of longer chambers is shorter barrel life as the freebore gets longer to accommodate seating heavier bullets out further. This forces a compromise between what works best for magazine-length ammo and longer cartridges. This makes freebores excessive at magazine length, jumping the bullet, degrading accuracy, and shortening barrel life. Some military shooting teams can afford rebarreling every couple thousand rounds but my team couldn’t and most civilian competitors can’t either.

Wylde chambers area good option for 77s and 90s. Most of my customers using Bartlein barrels are getting 3,000- 4,000 round lifespans when following proper cleaning practices. The only time I would use a longer chamber is in a dedicated long range gun only firing 90s. Knowing you have a Wylde chamber isn’t enough. Properly bro- VV N140 (right) is recommended in 20-26" barrels with Wylde chambers. Slower burning N150 (left) is preferred in 30-32" Palma barrels with Palma chambers.

ken in, this measures about 2.502" overall with a Berger 90 grain boat tail and about 2.461" with a Sierra 90 Match King. To know exactly, measure with an overall length gauge. The long body of the gauge can be used with many different calibers. A dummy cartridge insert attaches to the front and the bullet is inserted. The unit is run up into the chamber until the case shoulder is stopped.

Holding that position, the little knurled brass thumb screw at the back is loosened and the plunger is pushed forward, pressing the bullet into the throat. The thumb screw is tightened to lock in the reading. Carefully insert a cleaning rod down from the muzzle to push the gauge back out of the receiver. A caliper reading from the cartridge base to the ogive using a caliber-specific comparator gives the distance.

Repeat with nine different bullets of the same make for an average to four decimal places, subtract 0.005" and that’s the initial target seating length. This results in rounds coming out of the die 0.005" shorter than the chamber (just a little more than the thickness of a sheet of paper) before encountering the throat. Fire test groups at this setting, lengthening or shortening in 0.002" increments between test groups to find a sweet spot.

Each barrel will have its own specific sweet spot, normally with a bullet jump between 0.000-0.010". This can’t be predicted without test firing. I perform this service for every rifle I build or rebarrel and the customer receives a 20 round box of ammo set to this spot. Done properly, you should be able to cut your final groups by about 20% using this technique. 90 grain SMK bullets are available in 50 and 500 count boxes.

Experiments have found VV N140 for 20" Service Rifle and 26" Match Rifle barrels works best and longer 30-32" barrels with Palma chambers (a Wylde with just under 1/10" additional freebore and a tighter neck) prefer slower burning N150. These powders give me the best accuracy and consistent velocity. I prefer cases with a lot of volume to accommodate heavy powder charges and factory crimped primers, such as Lake City or Wolf.

Winchester also makes a good .223 Remington cases with straight and concentric necks, though they don’t offer crimped primers. With thicker brass like WCC or Lapua, cut powder charges by a half grain avoid excess pressure. Likewise, brass without the primer crimp require cutting powder. In Bartlein gain twist barrels with Wylde chambers and L. C. or Wolf brass with factory crimped primers, I am achieving my 2,600 fps in 20" barrels and 2,700 fps. in 26" barrels with 2 4 .1 grains of the N140.

Any deviation from this will raise pressures. In dedicated Palma barrels with longer Palma chambers this will probably top out around 2,800 fps with 24.5 grains of N150. Caution: Always start well below a suggested powder charge and work up gradually while watching for signs of pressure, group size, and chronograph readings. Again, start well below this and work up gradually just as with the shorter barrels. Insure your ammo is straight by using competition dies and measure runout with a gauge.

The stellar Hornady Cartridge Straightening Tool is a gauge and can fix runout if concentricity is off. No gun will shoot crooked ammo well, so manage it! 90 Grain Future I often wonder what would have happened had Sierra corrected their design failure back in 2006. There was genuine interest in a reliable 90 grain boat tail. They claimed sales didn’t justify improving it, but if they had it might have sparked demand. Further, customers shouldn’t have had to purchase the bullet in its original, weak design.

I still believe had they redesigned this then, 90s would be favored over 80s now. Given this second generation, I think they will eventually do so. Competition bullet design always favors performance. The 80 grain SMK is about 31% more wind resistant than the then-popular 69 grainer it replaced at 600 yards. Shooters eagerly made the swap when the 80 was introduced, even though it required

308 and .223 bullets blow in a full value two mph cross wind coming from left to right. The new 90 grain SMK would hit about 1/2" inboard (left) of the Berger. a faster twist rate. The new, second generation 90 grain SMK is about 24% more wind efficient than 80s, though it requires a faster twist. Is there any reason to think that shooters will forever ignore the obvious advantages? The 90 grain SMK is the next logical step in the evolution of Service Rifle shooting.

Reasonable Expectations While the 90 is about 24% more wind efficient than an 80 in an AR-15, it’s imperative to have reasonable expectations. Switching to a 90s is not license to ignore conditions and let the bullet "wind proof" you. There’s still the need to dope conditions and make proactive sight adjustments.

Talking with shooters trying these out, almost all of them recount instances where they studied current conditions during a string of fire, rolled into position with an appropriate sight adjustment, but had the wind change slightly as the shot was fired. Where shooters using 80s sometimes end up with a 9 in such cases, those with the 90s could still catch a 10. Best estimates is using a 90 buys you 2-3 points in twentyround 600 yard string.

I confess this is my subjective estimate and not a scientific study, and that such a point gain will vary at any given match depending on conditions, but the improvement in ballistic coefficient is there. Concerning accuracy potential, comparing hundreds of 1:8 barrels shooting 80s to my current Bartlein gain twists, the two current 90 boat tails shot 7.7% tighter ten-shot machine rest groups with about half as many fliers and those fliers were about half as severe as those with the 80s.

Is the 90 grain SMK the final chapter in bullet design for the Mouse Gun? I initially was one of those vocal M14 shooters thinking the AR would never equal the old brown gun. I was also one of those that thought we had topped out with the 80 grain SMK. Having to eat crow twice, I am reluctant to make many predictions. Back when I was working with Berger on developing a reliable 90 grainer with a thick jacket the first run came out at 93 grains.

This was just before Bartlein came out with gain twist barrels, so I declined the 93s and Berger thickened the jacket a little more. I think 600 and 1,000 yard events are well covered with 90s and I’d like to see manufacturers concentrate on a magazine-length bullet with a higher ballistic coefficient. There are at least two ways to approach this.

Factory pointing, such as what Sierra did successfully with their second generation This is different than using hand tools, such as the Reserve team tried as a failed experiment as the pointed bullets pressured up more, shot fatter groups, and didn’t show any downrange improvements. I admit the team member doing the pointing was brand new to the process but so is everyone first trying it. The second approach is a polymer tip.

A number of bullet manufacturers offer these but my tests have found they aren’t as accurate from machine rest as an hollow point meplat. Sierra introduced an acetal resin-tipped 77 grain Match- King. While I haven’t tested them, customers have told me they are not impressed with their accuracy. While shooter accounts to improved wind bucking, accuracy was lessened. Consider my two preferred 90 grain boat tails improved both ballistic coefficient and accuracy.

Also, these shooters admit their unstellar accuracy is possibly due to a load development issue as they simply used the same load up as with the open-tip 77s. Perhaps load adjustment will reveal a fix. If accuracy can be held, the tipped 77s have the same B. C. as the open tip 80 grain SMK, making it ideal for all rapid fire events. The CMP and NRA have since instituted rules allowing optics in Service Rifle and Match Rifle competition. Even before this ruling, competitors were using flat-top AR- 15s.

Given customers are modifying rifles to take advantage, upgrading barrels also makes sense. This would make switching to 90s ideal. I have been swamped with demand for flat tops and Bartlein gain twist barrels to shoot 90s. Bartlein reports on their website (Bartlein Barrels. com) a number of testimonials from top Service Rifle shooters using this combination to win at national and state level matches. Get your favorite gunsmith to build you one of these and add your picture to the list of winners!

There has never been a better time to make the switch. AG