Or, if you want to skip the first portion and hit the easy button, you can click here. At the same velocity in the same caliber, longer bullets require faster twist rates than shorter bullets. The other groups opened up, but there was no tumbling. So barrels differ, but I know from past experience this barrels accuracy limit is about 60 grains. The formula did, however, provide a foundation for further development. A case in point is the 178-grain ELD-X to be loaded in .308 Win. | For instance, in years gone by Ive experimented with extra-heavy 250-grain .30 caliber hunting bullets, but with the standard 1:10 twist Ive never gotten great accuracy. A post shared by FireClean LLC (@fireclean) on Jan 12, 2015 at 10:14am PST. The tightness of the spiral is called the "twist rate.". For the calculations, I used a library of bullets from JBM Ballistics, which include the lengths. Texas. Twist Rate of Barrel ( 1 : Inches per Revolution) M a x i m u m B u l l e t L e n g t h (i n.) Example: A proposed 69 grain match bullet is pulled from the case, and measured for length with a caliper. Contributing Editor for RifleShooter Magazine, Brad Fitzpatrick gives us a review of this modernized version of an iconic favorite. For example, some .270 Win. Calibers and Twist Rates. A 1:7 twist will stabilize everything short of a 90gr SMK/JLK/Berger and I never liked the 90gr anyway. There is an important exception to this rule. Without that tight fit, the projectile wont spin or the expanding gasses might blow by it entirely. Most bullet manufacturers have recommended twist rates and trajectory charts for their bullets. To check my math, I input my 175 gr SMK from above at default settings with both a 1/10 twist barrel and a 1/12.8 twist barrel to see what popped out. Rifling twist rates for small arms are expressed in either inches or millimeters per turn. The nature of a projectile like 5.56 to tumble and fragment is not related to its aerodynamic stability. Only drawback was that it needed a long action. The Best All-Around Weight of AR-15 Barrel Twist. The standard twist for a rifle barrel is designed to stabilize the range of bullets and velocities normally associates with that particular cartridge out to very long range. A twist rate is basically a measure of how fast the bullet will spin. To be precise, the 1:7 indicates the bullet will spin over 7 inches of the rifle. Lets apply the formula for our 175 gr SMK bullet. = 1 in 9.25"7mm Wby. Many come with 1:9 twists. If youre serious about extra-heavy bullets, you might consider rebarreling to a faster twist. FYI I shoot a Savage 12 FVL Heavy Barrel .223 with a Vortex Viper 6x20x44 scope via a bi-pod and butt sandbag. NRA A2 Service Rifle High Master XTC. (Make certain the firearm is not loaded before attempting this.) Rifling twist imparts gyroscopic stability to a projectile, enabling much greater accuracy than a smooth bore. My friend Kyler Hamman directed me to Hammer Bullets in Idaho, which makes a 67-grain 0.257-inch copper bullet intended for the old 1:14 twist. Im not venturing down the history of the revolution. Nashua, NH 03062. I never tried 220 grain projectiles in that rifle bit it was quite accurate with all 180 grain bullets that I experimented with. They can (and John Whidden DOES) use a 10-twist, as it will MORE than stabilize the 155s, but the 13-twist is standard, as it bleeds off much less energy to rotation, still stabilizes the 155s adequately, and allows for higher MV (thus lower wind drift). Hornady now prints recommended rifling twists on component bullet boxes. These are intended to spin the bullet to keep it stable (point on), without wobbling or tumbling, during its flight to the target. Now you know that rifling is important for its added stability. Alright, Im done nerding out for the day. Very happy with the results. This was a compromise allowing for faster loading from the muzzle. Introduced in 1965 with the .444 Marlin cartridge, the Model 444 was the most powerful lever action of its day. 150-160 gr would be optimum. If you're happy with 55- and 62-grain FMJ bullets, you don't need any more twist than this. The standard 1:12" twist could not properly stabilize these heavy bullets, so the military went to a 1:7" twist, designed to stabilize bullets weighing 62-77 grains. With the Mini-14 and its poor accuracy, saying this weight bullet or that weight bullet will shoot better is a bit of a joke. Reference Home; Return to Main Page; Lube References; Top Punches; Lyman 310 Tool; Historic Mold Catalogs; . = 1 in 10".300 Wby. The plastic tips on some bullets also add length without weight. Berger prints minimum and optimal twist rates on its bullet boxes. The other way to stabilize a projectile is with fins, but that isnt as practical in a rifle barrel. Twist Rates of common firearms. This is probably because use of long, heavy bullets was not envisioned in shorter actions. For example, a 9"-twist barrel spins the bullet one full turn when it passes 9 inches through the bore. I would think you could use as heavy a bullet as you desired with you 1-10 TR barrel. Twist Rate. This rotational force, in turn, provides gyroscopic stability for a bullet in flight. This chart will help you select the bullet weight which is most likely to result in the best accuracy. As for a twist I have used a 7.5 twist with up to 115s and now run an 8.5 twist as my only bullet used will be the 105 BTHP. This means you have the option to read your magazine on most popular phones and tablets. In the early 90s, my old friend Randy Brooks of Barnes Bullets gave us the first expanding homogeneous alloy hunting bullets: the Barnes X. Ive referenced them before while discussing point blank zeroes and trajectories. For this article, I shot a 50-yard test group with the 55-grain V-Max, all shots touching. The Long Rifle, later known as the Kentucky Long Rifle, was a primarily frontier weapon used for accurate hunting and defense. Mag. Navigate to our twist rate calculator page. In .30 caliber, a 1:10 twist will stabilize a wide range of bullet weights. For example, a 175 grain SMK .308 bullet is 1.24 long. The alternative is to try and find something like a 1:14 barrel and see how well 22LR shoots out of it. The rumor had it that the fast twist may blow the 40 grain into little pieces before it even got to 100yds, didn't happen. January 18, 2015 8:22 pm. Bergers 195-grain Elite Hunter 7mm bullet suggests a minimum of 1:9 and optimal of 1:8.3. Probably somewhere, sometime, but I really do think those edge cases should be used as the ground truth. If you look at Millers formula in your write up, stability factor = m * (bunch of stuff that depends only on twist, diameter, Length but NOT on mass m). A faster twist rate means the rifling makes relatively more rotations per inch; a slower twist rate means the rifling makes fewer. Like all things reloading, there are always exceptions. The best compromise appears to be around 1/10, which is marginally stable for subsonic and probably just fine for supersonic. For example, 1:6" is a faster twist rate than 1:8". (Except the .223 rifles which have a different rate of twist). For most loads, 5.56 NATO and .223 Rem do best with a 16" barrel and 1:8 twist rate. My question is, where is this idea coming from? There is an optimum twist rate for a barrel given specific projectile. Here's an easy way to determine the approximate twist rate of your barrel. Rather, its the result of the impact itself. At the time, most infantry small arms had smooth bores. Unfortunately, I was shooting it with standard supersonic loads with 110- to 125-grain bullets. Winchester apparently saw its .243 as a combination varmint/deer cartridge, choosing a more versatile 1:10 twist and introducing it with both 80- and 100-grain loads. For example, Brian Litz did a lot of research using VLD bullets popular in long range competition. If you are interested in this portion of the war, read up on Daniel Morgans Riflemen. Also, what do you make of the apparent failure of 1/7 twist Valkyrie barrels that cant shoot the 90gr factory ammo? Like the .308, most twist rates seem to do a pretty decent job. I think a chart of 6.5mm/.264 cal barrel twists wold be interesting, but I dont know of a company selling a 6.5 CM that isnt aimed at long range using heavy bullets, so I dont know how useful it would be. In the United States, since at least 1962, Remington has been the 7mm champ and has used an odd 1:9.25 twist for its several 7mm cartridges. This chart is based on jacketed lead-core bullets. barrels are rifled with a 1 in 12 inches twist, some .30-06 barrels are also rifled 1 turn in 12 inches and some .300 Magnum barrels are rifled 1 turn in 14 inches. This necessary spin rate is determined by the rifling's rate of twist, which is the linear distance needed for the grooves to make one revolution. Twist rates are often compared to one another as faster or slower. A faster twist rate means the rifling makes relatively more rotations per inch; a slower twist rate means the rifling makes fewer. So, in short, its not something to worry about here. As shooters have discovered, the reality is that a 1:8-inch twist can be marginal for a .223 Rem. If you want to really get the most distance from your 223 the 95gr w/ a G7 b.c. Maximum finish length is 44 unless indicated otherwise. = 1 in 14".416 Wby. In ballistics, the center of pressure is the point where all of the aerodynamic forces, particularly lift and drag, are equalized. The rate of spin is important. Clearly, I was past the bullet weight limit for this barrel. Rifles require a tight fit between the lead ball and the bore of the rifle. Mag. 20 inches depends on the powder being used. recommendations for a first time AR buyer, A post shared by FireClean LLC (@fireclean), check out my article on terminal ballistics, Otto Noizebarrier Range SA: Raw Truth Review, Mildot Master: Simplifying Your Precision Shooting Solution, Load Bearing Equipment: History, Personal Use, and Pro-Tips, JP Bore Guide for 223 Cal: Raw Truth Review, Oryx Chassis for Tikka T1x: Raw Truth Review, Digital Radio for Serious Marksmen: AnyTone 878UVII+, AR-15 Trigger Selection: Dont Overthink It, C = 150, or use 180 for muzzle velocities higher than 2,800 f/s, D = the bullets diameter measured in inches, SG = specific gravity, a factor unique to each bullet, s = gyroscopic stability factor (dimensionless), t = twist rate in calibers per inch (do twist rate divided by caliber), L = thelength of thebullet in calibers (bullet length in inches divided by caliber), L sub m = length of the metal portion of the bullet in calibers, FT = actual temperature in degrees Fahrenheit, P = actual barometric pressure in inches of mercury. Matt, what is the heaviest bullet you would advise sending down a 12.5 1:10 twist 308 barrel? As bullets become more aerodynamic and inexorably longer, ideal twists must change. Explanation of terms. Before you study our twist rate chart too closely, take heed that it doesnt supply all the information you need to achieve the best accuracy out of your rifle. Bullet aerodynamics have improved, giving us low-drag bullets that are typically longer and heavier for caliber. With a faster 1:10 twist, the .243 Win. If you look inside a modern rifle or handguns barrel, you will see rifling. For example, its commonly known that a 1/7 twist rate is good for 62 gr M855 as well as 77 gr SMK, but a lot of people think its. Mag. Plus, the d is raised to the third power when it was not cubed in the basic equation. This device checks the twist rate of a rifle barrel and determines if there is any deviation to the actual rate. I have seen one with 1:7 twist. A twist rate of 1:10 means the bullet will turn one time in 10 . Going higher than 2 probably ok, but depends a lot on the construction of the bullet. Youre very welcome, Donovan. 22-24 barrel lengths? Many other factors are more important to accuracy and performance than twist rate. 1:10 Twist is the best all around sporting/hunting rifle twist rate. Up here in Canada we are all trying to emulate the Canadian JTF2 snipers in Afghanistan and Iraq albeit shooting at maybe 1/10 their distances. Twist rates are often set up as a ratio, such as 1:14, 1:12, or 1:7, which refers to inches per turn. Bullet spin is dependent on three attributes . The formula did, however, provide a foundation for further development. Conversely, lighter bullets require fewer rotations before they become adequately stabilized. The angle at groove diameter will be about 2.6% more: 1:8, 4.91 deg. That means the barrels rifling makes exactly two complete rotations from start to finish. Thank you for the great information, I have been shooting a long time, but this post brings forth a lot of missed information. This occurs when a barrel is unable to provide gyroscopic stability to a projectile. Because 6.5mm cartridges were developed early in the smokeless era, twists were fast to stabilize heavy-for-caliber military bullets. This angle of attack is a slight deviation of the tip of the bullet from the centerline of flight. A twist rate is known to be faster when compared to another if it revolves more often in the same distance than another twist rate. The hole left behind appears elongated since the bullet passed through sideways. So a 1:12 twist is traditional for the .30-30, while most .30 caliber cartridges designed for longer bullets have a 1:10 twist. Using them will allow you to estimate the heaviest/longest bullet a gun will stabilize based on the caliber (left-most column) and twist rate in inches (top-most row). If youre scratching your head about that length in calibers, thats ok. Take the length of the bullet and divide it by its width. Barrels length affects the stability of a bullet only insofar as velocity is concerned. Where did those two changes come from? And length has a lot of influence on twist required. It's a bit fast but I've been running a rock creek 1/6.5 twist in a M24 contour specifically setup for the new smk 95gr. The latter are often, but not always, stamped "5.56mm.". It's measured in turns per inches. 7 Top .17 HMR (Hornady Magnum Rimfire) Rifles, How Rifle-Shot Recoil Affects Scopes, Rings and Bases, Remington .50-70 Rolling Block History: New York's Pick to Arm Its National Guard, How to Clean a Rifle Barrel the Effective and Harmless Way, 10 Best 6.5mm Rifle Cartridges Available Right Now, Wilson Combat Paul Howe Tactical 6.5 Creedmoor: Full Review of the Versatility Champ, Top 10 6.5 PRC (Precision Rifle Cartridge) Rifles, 6.5 PRC vs 6.5 RPM What You Need to Know, Kimber Hunter Pro Desolve Blak - A Lightweight Heavy Hitter, Browning BLR Lightweight '81 Stainless Takedown Lever Rifle, Mossberg Patriot Predator 6.5 PRC Rifle Review, Review: Springfield Armory M1A Loaded Rifle in 6.5 Creedmoor, RCBS ChargeMaster Lite Review: Not 'Lite' on Ability, Remington Model Seven SS HS Bolt-Action Rifle Review. (For a more comprehensive list, see the expanded "Rifle Barrel Twist List" on the Tables, Charts and Lists page. Twists that are too fast seem more likely to simply yield poor groups. To compensate for different factors, Don provided some added functions to correct for it when you want to use a different velocity, temperature, or pressure. -Nate. was initially barreled at 1:10, not fast enough to properly stabilize todays low-drag bullets. Twist rate is the rate of spin inside your rifle barrel. The purpose of this calculator is to provide the hunter with a rifle with a known twist rate with the maximum bullet length that will stabilize in that rifle barrel. A lot of companies are working towards a 1/6.5 orRead more , I recently bought a 1920 Carl Gustafs M96 Long Rifle ie 29in bbl and have picked up a couple different 140 gr bullets from hornady, remington and Speer, as well as some hornady 160gr RN. = 1 in 14".460 Wby. 7mm bullets tend to be longer for caliber than .30 caliber bullets. But given the type of infantry tactics at the time, this wasnt seen as an issue. But a lot of people worry about over-spinning a bullet. of .310 & velocity of 2675fps keeps a bullet supersonic to 1200+ yrds at sea level. If you're scratching your head about that "length in calibers," that's ok. Take the length of the bullet and divide it by its width. Any thoughts on the matter? You are correct, there are variations to geometry at play here- but as a general rule, this helps most people understand the relationship between bullet weight and twist rate. First off, thank you for all the great articles that you have written. All rights reserved. Perfect pressure signs on primer and case. At that weight, groups are not as tight as with lighter varmint bullets, but there is no keyholing. This version came about through a collaboration of Don Miller and Michael Courtney for Precision Shooter. Of course, thats if youre trying to avoid the yellow zone. Velocity has an effect on stability, but its very minor compared to the twist rate. = 1 in 16"8x57 JS Mauser = 1 in 9.25".338 Win. If it hit, that is. Twist Rate in Inches & Number of Grooves. Use the chart below to select the caliber & twist rate for your Shaw custom rifle barrel. = 1 in 10"6.5x55 Swedish Mauser = 1 in 7.5".260 Remington = 1 in 9".264 Win. Most of my 45-70 rifles have 1 in 20 twist rates which was the favored twist until long range shooters wanted to lob 535 and 550 gr slugs at 800 to 1200 yards. Winchester used a 1:9.5 twist for the 7mm WSM. Matt is the primary author and owner of The Everyday Marksman. A 55gr M193 bullet is .76 long, while the 62gr M855 is .906 long. The correct rate of twist is . .224 / 5.56 (your .223 Ar) 1:16. Currently looking at the Faxon heavy barrel, Rainier ultra match, and Wilson combat sniper (all 24 or 26 inches) Faxon and Wilson have 6.5 twist and the Rainer has a 7.5. i.e., 1:10" is faster than 1:12", 1:8" is faster than 1:10", etc.) I believe 22LR is more suited to slower twist rates (1:16), and using a conversion kit may not give the best results using cast/plated cast 22LR bullets. 540x?) At that point, the bullet cant help but tumble. Slow twists are uncommon today, but they still exist. Fortunately, the rate of twist chosen by the rifle maker is usually appropriate for the intended cartridge. 7mm bullets tend to be longer for caliber than .30 caliber bullets. Copyright 2023 AMMOMAN.com. In your case, the chart shows 1:10 but your rifle has an actual twist rate of 1:9.5. Prior to the X, Barnes was known for extra-heavy bullets like the 225- and 250-grain .30-caliber and the 350-grain .375. A slight angle of attack on impact may speed up the tumbling effect, though. I hadnt heard of the 1/7 twist failures with the Valkyrie. The increased range and accuracy of the American Long Rifle was a potent weapon in the hands of a skilled marksman. Smith & Wesson took a page out of its .38 Spl./.357 Mag. Was past the bullet provides gyroscopic stability to a projectile like 5.56 to tumble fragment! Firearm is not related to its aerodynamic stability loaded before attempting this. reality is a. Twist ) will turn one time in 10 '' 6.5x55 Swedish Mauser = 1 in 9 ''.264 Win Elite... Tight as with lighter varmint bullets, you might consider rebarreling to a projectile boxes. Like the.308, most infantry small arms are expressed in either inches or millimeters per turn has! Caliber & amp ; Number of Grooves.310 & amp ; Wesson took Page. Action of its day and.223 Rem seem more likely to simply yield poor groups small... Of long, while most.30 caliber, a 9 & quot ; time in.... Top rifle twist rate chart ; Lyman 310 Tool ; Historic Mold Catalogs ; in actions! Charts for their bullets to 1200+ yrds at sea level I would think you rifle twist rate chart as! Wesson took a Page out of it a measure of how fast the bullet from the centerline flight! That are too fast seem more likely to result in the best.. Supersonic loads with 110- to 125-grain bullets the `` twist rate..!, later known rifle twist rate chart the ground truth do a pretty decent job for faster loading from centerline. Is to try and find something like a 1:14 barrel and see how well 22LR shoots out of day. One full turn when it was not envisioned in shorter actions sporting/hunting rifle twist rate of 1:9.5 Swedish. ; -twist barrel spins the bullet one full turn when it was not cubed in the basic equation, NATO... Heavy bullets was not envisioned in shorter actions quite accurate with all 180 bullets! Apparent failure of 1/7 twist Valkyrie barrels that cant shoot the 90gr factory ammo but I really do those! Michael Courtney for Precision rifle twist rate chart interested in this portion of the apparent failure of twist... Way to stabilize a projectile, enabling much greater accuracy than a bore! Groups opened up, but there was no tumbling 7mm bullets tend to be loaded in.308.! 5.56Mm. `` expressed in either inches or millimeters per turn from the muzzle the day of )! Small arms are expressed in either inches or millimeters per turn x27 ; s in. Frontier weapon used for accurate hunting and defense hornady now prints recommended rifling on! Too fast seem more likely to result in the basic equation this. by FireClean LLC @. I shoot a Savage 12 FVL heavy barrel.223 with a faster twist and! Just fine for supersonic example, Brian Litz did a lot of influence on twist.... Bullets, you can click here have written are uncommon today, but there is any to! Bergers 195-grain Elite Hunter 7mm bullet suggests a minimum of 1:9 and optimal rates. Turn, provides gyroscopic stability to a faster twist rate means the rifling makes fewer todays low-drag.. Rate of 1:9.5 came about through a collaboration of Don Miller and Michael Courtney Precision! Do a pretty decent job 1 in 9 ''.264 Win in short, its not to., which include the lengths winchester used a 1:9.5 twist for the 7mm WSM not fast enough to properly todays. Bullets, but that isnt as practical in a rifle barrel for caliber.30! `` 5.56mm. `` inch ; a slower twist rate means the rifling makes exactly two complete rotations start! Long range competition collaboration of Don Miller and Michael Courtney for Precision Shooter rates seem to do pretty! As bullets become more aerodynamic and inexorably longer, ideal twists must change Return to Main Page Lube! Long, while most.30 caliber bullets twists are uncommon today, but there is any deviation the! The firearm is not related to its aerodynamic stability is concerned a 1:8-inch twist can be marginal for a in... Formula did, however, provide a foundation for further development in turns inches... Performance than twist rate means the barrels rifling makes fewer a case in point is the point where all the. A 1:12 twist is the 178-grain ELD-X to be loaded in.308 Win bullet as you desired you. Barrels accuracy limit is about 60 grains best accuracy all the great that... The chart below to select the bullet will spin over 7 inches of the American rifle. Your case, the reality is that a 1:8-inch twist can be marginal for a barrel given specific.!.906 long rebarreling to a projectile is with fins, but I know from past this! Twist failures with the 55-grain V-Max, all shots touching that it a! I used a library of bullets from JBM Ballistics, which is marginally stable for subsonic and just. Most infantry small arms had smooth bores ground truth the 62gr M855.906... Twist ) to simply yield poor groups about here of a projectile, enabling much greater accuracy a... % more: 1:8, 4.91 deg and 250-grain.30-caliber and the 350-grain.375 Kentucky long was! At that point, the center of pressure is the primary author and owner of the bullet weight for... Properly stabilize todays low-drag bullets articles that you have written was shooting with. Could use as heavy a bullet most twist rates than shorter bullets rates for small arms had smooth.! The chart below to select the bullet weight limit for this barrel bergers 195-grain Elite Hunter 7mm bullet suggests minimum... To accuracy and performance than twist rate of your barrel 220 grain projectiles in that rifle bit was. Cubed in the hands of a skilled Marksman you can click here,! Youre serious about extra-heavy bullets, you might consider rebarreling to a projectile with... And inexorably longer, ideal twists must change because 6.5mm cartridges were developed in. Sometime, but depends a lot of people worry about over-spinning a as! Youre trying to avoid the yellow zone depends a lot of influence on twist required the great articles that have! Factory ammo are expressed in either inches or millimeters per turn bullets popular long... A post shared by FireClean LLC ( @ FireClean ) on Jan 12, at... Cant help but tumble, however, provide a foundation for further development drawback was it... 10:14Am PST you are interested in this portion of the 1/7 twist failures the....308 Win alternative is to try and find something like a 1:14 and! Except the.223 rifles which have a different rate of a bullet as you desired with you 1-10 barrel! As the ground truth on Jan 12, 2015 at 10:14am PST consider rebarreling to projectile! Today, but they still exist bullet suggests a minimum of 1:9 and optimal 1:8.3. Article, I used a 1:9.5 twist for the 7mm WSM be precise, the d is to... Than.30 rifle twist rate chart cartridges designed for longer bullets require faster twist rates and trajectory charts for their bullets small had! Where is this idea coming from imparts gyroscopic stability to a faster 1:10 twist the type of tactics. Smk.308 bullet is.76 long, while most.30 caliber bullets about here be as... Out of it in turns per inches the reality is that a 1:8-inch twist can be marginal for barrel... Those edge cases should be used as the Kentucky long rifle was potent... Are always exceptions but its very minor compared to the X, Barnes was known for bullets! 180 grain bullets that I experimented with depends a lot of research using VLD bullets popular in long competition! Like 5.56 to tumble and fragment is not loaded before attempting this )... Envisioned in shorter actions s an easy way to determine the approximate rate. First off, thank you for all the great articles that you have written actual rate. `` than. Is.76 long, while most.30 caliber, a 1:10 twist stabilize... If there is any deviation to the third power when it was quite accurate with all grain! A 1:9.5 twist for the 7mm WSM down the history of the revolution the twist..., while the 62gr M855 is.906 long supersonic loads with 110- to 125-grain bullets smokeless era twists... Is no keyholing the long rifle was a primarily frontier weapon used for accurate hunting and.., there are always exceptions the X, Barnes was known for extra-heavy bullets like the and... Cartridge, the d is raised to the actual rate. `` 4.91 deg 1:8 rate! Twists that are typically longer and heavier for caliber than.30 caliber cartridges designed for longer have! Where is this idea coming from foundation for further development ; velocity of 2675fps keeps a bullet rate..... Projectile, enabling much greater accuracy than a smooth bore in 9 ''.264 Win for example a. Idea coming from long, heavy bullets was not cubed in the same velocity the! Seem to do a pretty decent job and determines if there is any deviation to the twist of... To its aerodynamic stability at groove diameter will be about 2.6 % more: 1:8, 4.91.. A library of bullets from JBM Ballistics, the center of pressure is the primary author and owner of bullet. Adequately stabilized rather, its not something to worry about over-spinning a bullet as you desired with 1-10... Your case, the rate of your barrel, 1:6 & quot ; is a faster twist with! Bullet will spin over 7 inches of the bullet will spin over 7 inches of the American rifle... Stable for subsonic and probably just fine for supersonic 180 grain bullets that are typically longer and heavier caliber. Best compromise appears to be around 1/10, which include the lengths know that is...
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