223 Ackley Improved: A better 223?
Whether it’s simple curiosity or a desire to increase performance, exploring different cartridges is part of being a shooter. One way to accomplish this is to purchase a new firearm. Another, more economical option, is to convert a rifle you already own to another cartridge. Imagine making your beloved 223 Remington shoot the same bullets you’ve been using faster? All you would need it a modified chamber and a new set of dies- that’s the 223 Ackley Improved.
An overview of improved cartridges:
Parker Otto (P.O.) Ackley was a well known author and gunsmith who improved standard metallic cartridges by decreasing the body taper and increasing the shoulder angle. These changes provided increased case capacity and increased ballistic performance. Ackley Improved cartridges could be chambered in a rifle in a preexisting caliber. The brass for the improved version of the cartridge could be fire-formed from a parent cartridge or formed with a fast burning powder and an inert case filler (the Cream of Wheat method). Cartridges improved by Ackley are known as Ackley Improved (sometimes designated by only the word Ackley or Improved). For instance an improved version of the 280 Remington would be known as a 280 Remington Ackley Improved or 280 AI. Shooters might refer to it as a 280 Ackley or a 280 Improved.
Originally, the no-go gauge for the parent cartridge would be used as the go gauge for the improved version. The field gauge of the parent cartridge would be used as the no go for the improved cartridge. This would provide a safe chamber dimension for the fire forming the parent cartridge brass in the improved chamber, while requiring minimum work to improve a rifle barrel. The downside to this method was that firing the parent cartridges in the improved chamber would often provide inaccurate results and the parent case would stretch to the longer length when the case expands against the chamber wall.
Some smiths turned back the barrel tenon one thread, reset the shoulder, and chambered the barrel with a head space dimension .004″ short of minimum so that the parent cartridge would be supported at the neck shoulder junction and provide improved accuracy and less case stretching when fire forming. Resetting the barrel one full turn also allowed the existing markings on the rifle’s barrel to remain in the same spot when assembled. The only real downside to this method is that it requires a lathe, while the original method of improving a chamber can be accomplished by hand.
To properly headspace barrels so the parent cases is supported on the shoulder neck junction, Dave Manson, of Manson Reamers makes specialized Ackley Improved go gauges. When using one of his improved go gauges, the bolt should close on the Improved go gauge. The parent cartridge go gauge becomes the no-go for the Improved cartridge and the bolt should not close on it. Keep in mind, depending on the head space gauges used, the head space can be .008″ shorter for barrels chambered with the set back shoulder method. This provided less case stretching and greater accuracy when firing cartridges loaded in the parent calibers brass.
223 Ackley Improved (223 AI, 223 ACK IMP, or 223 Improved 40):
The 223 Remington Ackley Improved is one of Ackley’s most popular creations. Parent brass is readily available and reported velocity gains average 100-140 FPS depending on bullet weight. 6mmBR.com has an excellent page with information on the 223 Remington Ackley Improved here.
As popular as the 223 AI is, load data for heavier projectiles is still less available than you would think. In this post we are going to take a look at the 223 ACK IMP with four different bullets, the 69 grain Sierra MatchKing (SMK), 69 grain Tipped MatchKing (TMK), 77 grain TMK and 80 grain SMK.
Our test rifle has been around the pages of Rifleshooter.com for a number of years. Originally a 28″ 223 Remington, it’s been cut and modified a few times until it has ended up in its final configuration, a 24″ 223 AI.
The rifle is built with the following parts from Brownells:
- Stiller action
- Bartlein Heavy Varmint 1:8″ twist barrel
- Accuracy International AICS chassis
- Jewel HVR trigger
- Harris bipod
To see how the rifle was originally built, check out Building a Custom Bolt Action .223 Rifle. To see how I converted it into a 223 AI see, Chambering a rifle for an Ackley Improved Cartridge.
Before I could load 223 AI brass, I needed to fire form it. I used new Lapua brass with both 77 SMK and 77 TMK bullets. Note the standard 223 Remington case (above, left- loaded to AR mag length) next to a loaded improved case (above, right). Both of these cartridges are loaded with the 77 TMK.
During the load development process I used two different scopes on the same rifle. For the 77 grain TMK loads I used a TRACT Optics TORIC 3-15-50mm scope. TRACT Optics is a new company founded by a couple of guys who left the Nikon sport optics program. TRACT’s business model is new to the industry, they sell direct to the customer, no middle man, this means the end user ends up with more optic for the money. Right now they make hunting style scopes like the TORIC shown above and they are a solid value. If you are looking for an optic for a hunting rifle, check them out!
For the remaining 69 and 80 grain loads I used a Nightforce 15-55x52mm Competition scope in a Spuhr mount. This scope was designed for F-Class competition and offers a wide range of magnification. I typically run it in the 15-30X range, most often at 20X. The fine reticle and 1/8 MOA adjustments are great for precise target work.
Time to load some ammo!
I spent a few weeks tracking down data from various sources. Load data for the 223 AI, especially with the heavies, seems to be sketchy at best, but I found a couple loads that I wanted to work towards. In retrospect, starting at the top end of 223 Rem and working up slowly might be a more prudent choice. As always, the information presented here is for informational purposes only and all loads should only be considered safe in the test gun.
Before we move on, let’s take a look at the disclaimer:
WARNING: The loads shown are for informational purposes only. They are only safe in the rifle shown and may not be safe in yours. Consult appropriate load manuals prior to developing your own handloads. Rifleshooter.com and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.
That’s a 5 shot group (above), fire forming brass! .384″- not to shabby! This is why it pays to head space an Ackley Improved rifle the right way. Supporting the parent case on the neck body junction of the case works!
All loads were developed on fire formed (1 time fired) Lapua brass with a CCI 450 primer. Charges were dispensed with an RCBS ChargeMaster and bullets were seated with a Foster press with a Redding die.
All rounds were fired prone, from a bipod with rear bag. Ballistic information was recorded with a MagnetoSpeed V3 barrel mounted ballistic chornograph. Target distance was 100 yards. Air temperature on the day the data was recorded is displayed in the table below.
A look at the four test bullets (left to right): 69 gr. SMK, 69 gr. TMK, 77 gr. TMK and 80 gr. SMK.
Loaded cartridges (above, left to right) 77 TMK loaded to AR-15/M16 M$ mag length in 223 Remington, 69 SMK, 77 TMK and 80 SMK loaded in 223 Ackley Improved.
During the load development process I started with the 77 TMK, moved to the 80 SMK, 69 SMK and finished with the 69 TMK. For purposes of this post, I’ll post the load data in ascending weight of the bullets, beginning with the 69 grain loads and working up.
69 grain SMK and TMK
The 69 grain SMK #1380 is a staple of High Power rifle competitors. With a G1 ballistic coefficient of .301 above 2,800 feet/second and .305 between 2,800 and 2,200 feet/second this bullet is well known for it performance on the 200 and 300 yard lines.
The 69 SMK was 2.308″ to the lands in the test rifle, I loaded it to 2.300″ for a .008″ jump.
The 69 grain TMK #7169 is a newer offering. With a G1 BC of .375 above 2,700 feet/second, this new bullet offers a step up in ballistic performance over the SMK.
The 69 TMK was 2.355″ to the lands in the test rifle, I loaded it to 2.345″ for a .010″ jump.
For both of these bullets, I selected B-LC(2) powder. An established military ball powder, it seemed to have a good reputation with these bullets in the 223 AI from one source I found. I’m not a fan of ball powder, however, I decided to give it a shot.
For the 69 SMK muzzle velocities ranged from 3,076 to 3,256 feet/second with an average of 3,172 feet/second. Standard deviation ranged from 2.6 to 40.8 feet/second with an average of 21.9 feet/second. Group sized ranged from .411″ (.393 MOA) to 1.272″ (1.215 MOA) with an average of .898″ (.857 MOA).
For the 69 TMK muzzle velocities ranges from 3,104 to 3,269 feet/second with an average of 3,191 feet/second. Standard deviation ranged from 7.4 to 20.4 feet/second with an average of 14.9 feet/second. Group size ranged from .516″ (.493 MOA) to 1.239″ (1.183 MOA) with an average of .891″ (.851 MOA).
All 69 SMK and 69 TMK load cycled well from the AICS magazine.
77 grain Tipped MatchKing
The 77 TMK #7177 is another new offering from Sierra. With a G1 BC of .420 at velocities above 2,400 feet/second- the same as the 80 grain SMK! IMR 8208 XBR has an excellent reputation in 223 Remington with the heavies, so I it was an obvious choice.
The 77 TMK was 2.360″ to the lands in the test rifle, I loaded it to 3.355″ for a .005″ jump.
For the 77 TMK velocities ranged from 2,869 to 3,064 feet/second with an average velocity of 2980 feet/second. Standard deviation ranged from 31. to 26.2 feet/second with an average of 14.8 feet/second. Group sized ranged from .335″(.320 MOA) t0 .724″ (.691 MOA) with an average of .563″ (.538 MOA).
All 77 TMK loads cycled well from the AICS magazine.
Note: I shot these 77 TMK groups in poor wind conditions. Pretty steady 25 mile/hour winds with gusts to 33 mile/hour. I had dry leaves pressed up against the side of the chassis, held in place by the wind!
80 grain Sierra MatchKing
The 80 SMK #9390 is proven at the 600 yard line for high power rifle shooters. Offering a G1 BC of .420 at velocities above 2,200 feet/second, this round is capable of impressive performance for a 223, especially when pushed fast. I selected IMR 8208 XBR and Varget for the 80 SMK.
The 80 SMK was 2.430″ to the lands in the test rifle, I loaded it to 2.420″ for a .010″ jump.
For the 80 SMK muzzle velocity ranged from 2,832 to 3,048 feet/second with an average of 2,931 feet/second. Standard deviation ranged from 4.6 to 21.5 feet/second with an average of 12.7 feet/second. Group size ranged from .299″ (.286 MOA) to .948″ (.905 MOA) with an average of .615″ (.588 MOA).
The 80 SMK did not feed particularly well from the AICS magazine. I believe this was to the relatively long OAL, I believe shortening the load would allow it to feed well.
External ballistics of the 223 AI
Let’s take a look at how the 223 AI loads stack up. Since an improved cartridge is about greater powder capacity and speed, I decided to model the fastest load for each of the bullets tested. The results are displayed in the table below. I ran the 80 SMK twice, in addition to the fastest load which used IMR 8208 XBR, I added the fastest Varget load as well (2,976 feet/second). For comparison purposes I listed my 308 load with a 175 SMK at 2,670 feet/second (70 feet/second faster than Federal Gold Medal 308/175 advertised velocity). All values assume the shooter is at sea level and temperature is 59 F. The lowest value of drop and drift for each 200 yard increment is highlighted in bold text.
A few surprises here. While I was certain I would be able to out perform (on paper) the 308/175 with the 80 SMK, I didn’t think the fast 69 SMK and 69 TMK loads would be so competitive out to 600 yards (or stay as flat as they did out to 800 yards). It is worth noting that all of the loads besides the 69 SMK will stay supersonic past 1,000 yards (the 69 SMK gassing out just shy of 1,000 yards). At 1,000 yards all loads, except the 69 SMK, offer drop and drift advantages over the 308/175!
The data I gathered gave me a few options for loads to use in the future. While some of the 69 SMK and TMK loads shot fairly well and are flat and fast out to 600 yards. The wide swings in SD with the B-LC(2) reminded me why I dislike ball powder. The 77 TMK and 80 SMK both shot well for heavier bullets, as loaded the 77 TMK fed reliably from a magazine and the 80 SMK with it’s long OAL did not. I plan on doing more 80 SMK work with a shorter OAL that will feed better.
What are the upsides to 223 AI? Low recoil, increased velocity, readily available brass (to fire form) and a wide range of bullets make it an excellent choice.
Downsides to the 223 AI? You have to fire form brass. While the gun shoots the 223 Rem brass well, the fire forming does require another trip to the range. Alternatively, some AI shooters will form brass with the so called “cream of wheat method” using pistol powder and inert filler or a hydraulic forming die.
How useful is the 223 AI? The 223 AI has a well deserved following among varmint and predator hunters. If you shoot F-Class Target Rifle (F-TR) it isn’t allowed (223 REM/308 WIN only). Using a 223 AI would have you shooting in F-Class Open (F-O) against superior 6/6.5/7 mm cartridges, so I wouldn’t recommend it (NRA rule book here). For tactical and precision rifle matches, the small bullet will be difficult to spot hits on steel at longer ranges and again, the 6/6.5mm options are better. If you want a .224 diameter center fire rifle, with a decent velocity, easily available brass, minimal recoil, a long presumed barrel life and don’t mind fire forming brass the 223 Ackley Improved may be the better 223 for you. I’ll keep mine!