Which is more accurate?  

I want to see that 55gr 1/12 twist when it hits ballistics jell vs the 1/7.

I was surprised a little by the 62gr in the 1:12''. I didn't see that in my testing of the Brownells 1:12'' barrel until I got over 69gr.

I saw a video with two rifles like yours, one with a 1/12 & other 1/7 twist. When shot into ballistic gel, the 1/12 would take a violent, almost 90° turn and yaw out of the gel while the same ammo out of the 1/7 kept a almost straight shot path into the gel. I just wanted to share what I had seen with the two different twist rates. Great video Mac, love those "old" AR platforms.

Thank You, H&R for bringing back into production these M16's. We enjoy them. Thanks MAC for the video. Blessings.

Great video! I was getting ready to swap my 1:12, 20" Barrel to a 1:7, 20" so it could fire more varieties of ammo and you uploaded this at a perfect time!

Back in the '80s, I read an article in SOF magazine, where this test was performed, with the same results. So, there are no surprises here, but it is nice to see you validate it.

would like to see comparison alongside 1/8 .223 wylde barrels

I know this pertains to the clones that said, it's been my experience with standard rifles today the 1/7 is best for 62 grain and heavier but the 1/9 is optimal for 52, 53 and 55 grain bullets...using a 16" barrel.

I agree with needing a larger sample size for velocity. 36 fps difference? As Paul Harrell would say: that's within the variation of one round to the next; not enough difference to make a difference. Is the tighter twist converting more energy into angular velocity? Most likely, and I'm sure there's math that will support that. Does that make a difference? Probably not in a vast majority of use cases. There might be one extreme example where it might, like shooting at a very long distance, but I doubt it within the standard use case of the round (within 300 yds).

EXCELLENT job as always. Interesting, and relevant content. Thanks MAC !!

Thanks for finally comparing the velocity between the two twist rates with the chronograph! I've been curious about the twist rate effect on bullet speed for a long time now. Really wish 1/9" twist barrels were still common like they used to be. Seems like the best compromise for a 16" pipe.

Exactly the video I wanted to see , thank you !

Rather interesting sidenote, while doing research to make my own rifle, I came across an aged formula for determining optimum twist rate for a given barrel length and projectile weight/diameter ratio. It is crazy accurate from the tests I've run on various projectiles and explains a wealth of information on why twist rates are what they are for particular projectiles.

Certainly interesting results... wonder if it would be similar with other manufacturers, and different barrel lengths. I imagine the 1:7 would be better for a shorter barrel, as they both kind of compensate for each other in this regard. There are just so many things that can affect accuracy though, it is impossible to test them all. Thanks for sharing, and maybe next time use a magnified optic, might help you compensate for the older eyes. I'm nearing my 40's and am noticing my sight is getting worse, so a big scope really helps!

Now THIS is actually something I have wondered.

Awesome video! Very useful information. Thanks guys.

Your videos are always very informative

Perhaps in the future you could test the 16" barrel vs the 20" barrel using the 55 gr and the 62 gr rounds. Most AR15's I see sold are the 16" variety. Thanks for your outstanding videos!!

Excellent video this is something I wanted to know

Back in the 1980s just prior to when NATO adopted the SS109/M855 62-grain "green-tip" enhanced penetration round for the 5.56x45mm cartridge as its standard, army testing of twist rates found that 1:9 was optimum for stabilizing both the old 55-grain M193 round and the new M855. However, trouble hit when the 62-grain tracer was tested; it was not stable out of a 1:9 barrel, due to its greater length than the standard M855. The army switched to a 1:7 which solved the problem, albeit at some cost in accuracy with M193. If you plan to use exclusively 55-grain (or lighter) ammunition, then the 1:12 with a 20-inch barrel is optimum; it is close to the original configuration designed by Eugene Stoner et al.(which was 1:14). However, if heavier and/or longer fare are to be employed, a faster twist is needed. Every barrel is unique, but most 1:9 tubes will stabilize adequately up to 69-70 grains or so, some a bit heavier. If 70+ grains are to be used frequently, then a 1:8 or 1:7 are best. Service rifle competitors who single-load shots of 80+ grains for the 600 yard stage sometimes use a slightly faster twist than 1:7 to achieve optimum results.

thanks for making this video! answered some of my questions,curiosity

I prefer 1:8 twist as a good over all with the vast majority of 556 ammo I can find on the market. Works best with any thing 62 to 77 gr bullets. But still works just fine with M193 and anything 50 to 60gr and also 80 to 87gr bullets. 1:7 twist is perfect if you like to use heavy hard hitting or long raing bullets 69gr and all the way up to 90gr or I think 112gr is the heaviest bullet offering in .223. But will still do ok with 55gr to 68gr that most of your ball ammo is going to fail into. 1 : 12 twist. Your sweet spot for accuracy is probably going to be with in. 40 to 64gr. Probably best with 45gr al the way up the 62gr that's not M855/ss109. Assuming you are not planning to shoot past 300 meters. Or gofers at 100m

Very informative. Thanks

Great video , always wanted to see a wring out of the two twist rates. Would love to see more about other twist rates and higher bullet weights

Good video. The 1 in 12 twist is perfect for the 55 gr bullets. When I was in the Army, (69-72) we used the Colt scope for testing some M16A1 rifles. All would shoot into an inch at 100 meters with the military M193 ammo. I worked in a depot weapons shop. Concerning your vision, try an adjustable aperture.

Real early M16’s had a 1-14 twist rate.

Interesting vid, just for general thought I bought a colt A1 AR sporter in 1978. Like new con 1in14.shot great made in 1973, in mid 80s retired to the back of the safe. Thanks for all your work.

I bought two A1 clones opting for 12-twist. Love them!

Imagine what the 1/8, 223 wylde, 20 barrel would do... supposed to be some of the most optimal for everything from 55-77 grain.

FWIW. Desert Shield/Storm. My USAF TACP with the 2nd BDE/101, was issued M-16A1s. The Army had A2s with their 62 grain bullets. With the Army issued ammo, our USAF A1s were key-holing the rounds at 25 yards. The 101st was awesome, and issued us all new A2s.

Another fun vid, Thanks Tim.

@military arms channel: No key holing with 1/12” barrel and 62 grain bullets? When we took our GAU-5s to the range with 62 grain ammo we got frequent key holing at 100 yards and beyond.

Huh🤔!!! Interesting results. Awesome review brother. SF!

I work in EOL care. Getting old is a blessing, sir. Rock those eyes with pride and happiness.

Thank you for reminding me that we could measure rifling twist by revolutions per minute on the projectile. I had trouble enough with my command while on active duty during the change-over from M16A1 rifle with M193 ball to M16A2 rifle and M855 ball. "Is that green tip going to start fires?" You also demonstrated a slight difference in velocities with a small sample size, reminding me that I have to take greater care defining what my own test results tell me. Off the cuff it makes sense that a 1:7" twist would produce more barrel friction than a 1:12" twist and produce lower velocities. You pointed out the need for more shots fired to validate results--and you used H&R barrels in testing--good call. I don't know if other brands of barrels would change the results. My test results will vary due to test equipment, test conditions, barrel brand, ammunition maker, and bullet design--but the figures should be close. The M193 and M855 projectiles are boat tail bullets with spire points. Some .223 Remington bullets have flat bases, different nose profiles (ogives--can shift center of air resistance), may have hollow points (shifts the bullet's center of gravity) and may be shorter or longer projectiles. The 1:7" twist was to stabilize the M856 tracer in sub-zero temperatures. The M196 needed 1:12" rifling for stability under Arctic conditions--the original 1:14" twist rate failed to stabilize tracer rounds. What this means for the shooter is that using bullets heavier than 55 grain in 1:12" can possibly work okay and that bullets heavier than 62 or 64 grains can be stabilized in 1:7" barrels. The way to find out is shooting benchrest groups at 200 yards under anticipated shooting conditions--yes, I know, firing at 100 yards may be the limit due to available shooting range facilities. Bullet length makes a difference. This difference is more important to handloaders using custom bullets and demanding maximum performance. Firing those heavy and long 64-grain M855 factory loads through an old Colt SP-1 (1:12" rifling) to a maximum range of 50 yards from off-hand positions on eight-inch bullseye targets or M9 silhouettes probably won't yield significant differences in precision. Using the same rig on jackrabbits at 300 yards will--if the shooter can see the target and aim from a steady position. About three inches at 100 yards won't cut the mustard when the target is 300 yards away and smaller than three inches.

Awesome stuff! 😊

Interesting results. Thank you

Great Show

Really enjoyed, good info, thanks

That's awesome content right there.

I bought a model 1 sales 12" twist bull barrel for next to nothing once and built a rig for my friend to use on vermin and with 40grain vmax it was a laser beam. 1/4 moa with hardly any reciol, he LOVES that rifle. It's all about the right system.

around '84, we started hearing rumors about a new round being developed for the M-16. it was supposedly designed to penetrate a WWII style metal helmet at 800 m. it was going to be a "flechette" round where the copper jacket peeled away halfway to the target increasing the range. gotta love rumors but this was most likely the testing of the heavier grain rounds for the rifle at the time. (too many people complaining about the lack of stopping power of the smaller caliber). i never fired the 'new' round as i got out of the service in mid '86 but watching this video, i can bet there were a BUNCH of US Air Force Security Specialist pissed off to beat hell trying to get their re-certs done on the same rifle they've used for years, which suddenly started pushing out 7 MOA groups. lol. not sorry i missed that sh*t sh*w. i loved that rifle. after 30+ years, i decided to build my retro M-15/AR-16, complete with the slick side carry handle upper and 20" 1:12 twist pencil barrel. only thing different is the Brownell's retro 1x4 scope because... uh...er... you know.... the eyes t'aint what they used to be. another rumor i've heard about the 55g FMJ is it's "sweet spot" is at the 3,200 fps range. something i've noticed from all manu's is 3,000 fps is the most you'll get, as replicated here in this video. it would be interesting to see if there's an accuracy improvement using Lake City brass while pushing that 'optimal' speed range. regardless, 55 grain FMJ at 300 yards is devastating to a 5 gallon jug of water there's a video on RU-vid about it ; ) Thanks, MAC.

Great information Thnx

Very good video. If you spin something faster, it takes energy.... basic thermodynamics state that nothing is free. The marginal velocity reduction of a faster twist rate was something that I have often wondered about. Clearly, by moving to faster twist rates, the trade off of stabilizing a wider range of bullet weights was a good call. I learned something today and thank you.

Great video

Very interesting results indeed.

I feel you pain with the eye sight, had to go to a crossbow with a scope because if I focused on the pins I couldn't see the deer clearly if I focused on the deer I couldn't see the pins. That all happened at the age of about 62, love the content keep it coming!

Very interesting. Kind of what I expected.

Thats weird, my test results were different. My 1-12 twist was key holing at 50 yards with anything over 55gr. Pretty crazy to see key holes already at 50yds!

Dang, love that chronograph!

I've always leaned towards the 1:7 twist rate for its versatility with a wider range of bullet weights

I own a 1:7 Wyndham weaponry retro M16 and love it.

Gun Kenobi with an interesting vid. Cheers Mac.

As others have stated it would be interesting to see a comparison using ballistic gel...but I would use a scope to get more refined shots...

Thank you

With the slower twist rates adding velocity in mind I would recommend the 1 in 8 twist not the 1 in 7 twist. The 1 in 8 twist stabalizes 77 grain perfectly fine with the added bonus of a bit more velocity.

You live in Indiana if I remember correctly. I'm in Southern Indiana so can confirm, yes humidity can be horrible here, can be 100% at any point.

Highschool would have been so much better if Mr. Teacher whipped out a dagger for his pointer ~ nice touch on the data breakdown.

Test a 1:14 with a 43 grain spitzer!

I had a rifle with a 1/9 twist that couldn't stabilize a box of M856 Tracer (64 or 65 grain I believe) rounds that I had. Couldn't accurately hit a steel gong at even fifty yards with it. Switched to a 1/7 twist on my upper, works fine now.

This is awesome

I'm 76 years old and I see the front sight just fine. I have 20/20 left eye and 20/15 right (shooting) eye. No glasses.

I take it Mac is proud of Standing on the square.

As far as your “old” eyes go, both my parents had the eye surgery to improve vision/remove cataracts. They were in their sixties and loved the results. I am now approaching the same age, however I could never deal with the massive amounts of eye drops you have to do for a couple of weeks after the procedure.

In very simple terms, the heavier the projectile (it is actually a function of bullet length and sectional density, but we are simplifying things here), the faster (lower number) twist rate you are likely to want to utilise. It is bullet length that determines twist rate not weight.

Wasn’t expecting my guy to pull out a dagger 🗡️

The earlier TM's from the military specifically discussed the differences in M193 and M855 in the A1 and A2 rifles, detailing terminal performance on target as well as POI shift and how much a soldier can expect accuracy to degrade in putting M855 in the A1 rifles.

I really struggle with iron sights too given my aging eyes. One thing that might help you in this scenario is to pull that rifle back a few inches to get that front sight out of the sunlight.

Another wonderful video. If you ever redo this, add in your notes to add 40 grain. I bet 1/12 will be very accurate and in same area as 55 but 1/7 will have a noticeable impact shift. Again, great video, love you channel, and I'm suprised I'm note subscribed. I'll fix that.

Interesting results. I like to think if optics was possible if the results would have been the same. I just recently did a comparison between two builts. Same bolt assembly, upper and lower, but different barrel twist and length. One rifle has a Green Mountain 1:6 19-inch barrel: 77 grain @ 100 yrds .34, .41, and .63. Other rifles have a Citerion barrel 1:12 20-inch barrel 55 grain @ 100 yrds just as good. .40, .46, and .57. When time permits, revisit this, but this time, switch the bullets weighs and see what happens. Thank you for sharing.

Got a military standard (civ) AR A1 2nd hand in the late 70's. Measured the twist myself and came up with a 1 in 14. Yes you heard correct 1 in 14 twist. 55 gr @ 100 was about 4-6". @ 200 it opened to about 6-8". The 62 gr out of the 20" barrel got a little squirrelly @ 100. One 5 rd group would be 6-9". The next grouping would be 9-12". I was using a 3' sq backing for my target @200. This is where the grouping got really squirrely. At 200 yards, out of a 10 rd string, I generally could find 3 or 4 bullet holes in the 3' backer.

I was first issued and trained with the M16A1 in the army with a 1:12 twist. At a Canadian Bull zero target I could put two rounds in the same hole at 25 meters with government ball ammunition. I could do the same with the M16A2 with the 1:7 twist. . We used a different zero target for it. I prefer the Canadian Bull. The difference ammo made a difference. The manual said that the A2 could use the NATO 5.56 as well as the M193 ball round of the A1. Although not as accurate. However, the M16A1 couldn’t shoot the 5.56 NATO round well it went off target. I carried the A2 during Desert Storm. The A2 was better in some ways. But because it was Zeroed slightly differently from longer range you had different hold offs for it. I preferred the A1 because it was zeroed out to 250 meters but you could still hit the 300 meter target with iron sights without a significant hold off.

I have a IWI Zion with 1:8 twist that won’t shoot 69gr under 4 moa. I also have a Barrett with a 1:7 twist that shoots the same load sub moa.

1 - I'd buy one of those for the 20" barrel, and 'cause they're being made by one of the M1 Garand manufacturers 🙂And would go with the "variety of ammo" twist rate 😛 2 - That's a beautiful dagger. Sometimes seemed to have a second bevel, but depended on the angle. Is it Lockwood? Loved the fittings and leather color choice 🙂 Thanks for the vid Tim! Was super helpful indeed! 😀

Light bullets, slow twist. Heavy bullets fast twist. Back in my gun repairing days I had a Sako heavy barrel in .222 sent my way because is was lacking accuracy. I happened to remember that model had a 16 twist so I loaded up some 45 grain bullets. It turned into a tack driver with that load.

1-in-14 twist for the win. 😁

The reason they changed twist rate was that the 1 in 12 wouldn’t stabilize the 62 gr bullet. The 1 in 7 with a 55 gr bullet will cause a 30% decrease in accuracy according to NSW Crane Navy admin message and may actually cause damage to a military barrel. So you just confirmed that. Nice video

I love and hate that you brought up the 8k bcm rifle! I've been so waiting for you to be able to finish getting it to 10k!

How about a 1:9 twist barrel? That seems to be the compromise that a lot of manufacturers are/were going to. Not exceptional for any one bullet weight but decent groups across most of the commonly used rounds.

The most accurate AR I ever had was assembled with a surplus 1:14 original non chrome lined barrel that I got from SARCO in 1985. Only mods were a free float tube and a special hand grip screw that took the slack out of the trigger. Factory FMJ 55gr 1 to 1 1/2 inch. Hand loads 55gr SP 1/2 to 1 inch. And my all time best 53gr flat based match that would do under 1/2 all day. Those were 5 shot groups. Never shot or owned any other AR that could do that even with expensive match barrels.

This video made me feel nostalgic so i look at how long i have been watching this channel and realized i started watching when i was 28 and now im 41😂

Would have liked to seen these test done with M193 and SS109. Still good information.

Thanks for the video! Would like to see what 77 grain will do.

The variety of ARs gives you the paradox of choice. I've done so much research trying to find the "best specs".

I’d like to see a 1:14 barrel thrown in for once… Including a 1:9 would be useful as well…. Using bullets from 40gr up to 77gr… Maybe a summer project for me…

Would love to see what a 1/9 twist would do. As for not seeing the front sight as clear, as my doctor told me when I was complaining about all my aches and pains "it's much better than the alternative. Also gel tests would be interesting.

It is a mechanical certainty that the faster twist will yield lower velocity. Or is also a certainty the difference would be less than 3%, so those numbers seem correct

I use a 20inch Wilson Combat barrel heavy bull,1:8 twist. It gives me quarter size groups at 200 yds with 68 Hornady Frontier bthp match ammo😊

In the beginning Eugene Stoner brought about the SP1, 20” barrel, 1in 12 twist 55 grain bullet and the gun world was happy which to this day is still the very best set for an AR type guns effectiveness. My very first AR / SP1 updated with an AR15/M-16 A2E2 upper for the way better rear site with a forward assist. I was a member of the West End gun club in the early 1980’s and we had a thousand yard range, so I can tell you for certain that a 1 in 12 twist with a 55 grain bullet gos sideways/ key holes at 900 yards. A 25 grain to 40 grain will stay accurate out to 1000 yards and beyond. Groups are measured in feet at those kinds of distances. 62 grain and heavier goes sideways from 100 to 300 yards out of a 1 and 12 in my experience. A 1 in 9 twist rate is what I have found to be the best rate for all around bullet weights from 40 grain to 77 grain fairly well. But if you want the most effective rate for what the AR was originally designed for you want a 20” 1 in 12 barrel with 55 grain projectiles, but if you’re going to need to be able to use 62 or 77 grain projectiles you need a 1 in 9 twist rate. Be safe out there and always remember that projectiles can travel up to 28 miles so always use or have something behind your targets, never place a target on a hill top, because every single round that goes through the target or misses the target can fly for miles. The 28 miles thing is from WWI both the Germans and the US were involved in volley type fire and a 1903 Springfield or 1917 Enfield rifle could fire Ball M1 - 180 grain full metal jacket spiral tipped bout tail projectiles out to 28 miles.

Would love to see how a 1in8 twist would do. Many guns were coming out in that twist rate a few years ago

I'd like to see Tim do a video on the different chambers(.223, .223 Wylde, and 5.56), and see how it effects the velocity, and the accuracy of 5.56 and .223 rounds, preferably the same loading from the same manufacturer. I remember when I used to be more interested in ammo, and getting the right HD round, and I would look up a loading in .223(for example Winchester Ranger/LE line), and compare it to the same load, but in 5.56, and the 5.56 loads were always(well, usually) 1-200fps faster than the .223 loadings. I always wondered if they were using the same rifle/barrel to test the velocities, and if it was chambered in .223 or 5.56. Also, as someone who grew up in a red dot/optic world, and who still isn't great with iron sights on a rifle, especially when shooting "dynamically", moving, rapid fire, etc., I can't even imagine how hard(and scary) it must have been for those kids in Vietnam(and other conflicts with other rifles) who may have never even shot a rifle before, all of a sudden getting thrown into firefights in the jungle against men who've been fighting wars for the past decade or two.

Good test, Tim! Still, I think I would like to see the same test with a couple of scoped rifles (not something attached to the carry handle, however! I have had zero luck with such scopes in the past and do just as well with iron sights!). I'm old enough that I have either red dots or scopes on everything! I've never once hunted any big game without a scope due to relatively poor vision. I'd also like to see some mil spec ammo included, M193, M855 & maybe even SS109, which are all relatively (for the moment) available. I believe a decent scope evens out the difference between a shooters ability and the ability of a rifle to group. Of course, the bottom line is going to depend on individual rifles as well. Not all rifles are created equal, even if they have consecutive serial numbers from the same manufacturer. It's just a fact of life and it's pretty unlikely that any two rifles will shoot exactly the same groups with any given ammo, even with everything else being as equal as possible. It could happen... but I wouldn't bet a nickel on it! Basically, rifle accuracy is a crap shoot, involving not only the rifle and accessories (scope, mount, rests, etc), weather, how the shooter feels that day and what phase the moon is in! Plus a bunch of other stuff I won't even try to mention. If you were to shoot 50 groups, on different days, with each type of ammo, you might get some meaningful statistics... but only with those lots of ammo! There's always a little bit of voodoo mixed in with testing of any kind, it just can't be helped, short of spending all your time and money, not to mention barrel life, on testing! Even if you did, it would only apply to those two rifles! The only solution is to do the testing on your own rifle. And to do enough to prove to yourself, that X brand (or, in my case, X load) is the best for your needs. It's like zeroing your rifle... yeah, you can follow the general rule (whichever one you like, 25 yards, 50 yards, 36 yards, etc., etc!) but without a chronograph and accuracy testing, it's nothing more than a SSWAG - a Semi Scientific Wild Assed Guess! Which means you're going to get SSWAG accuracy out of your rifle. But hey, if that's good enough for you, great! Personally, I want to know where my rifles shoot... preferably exactly where they shoot! Cheers, jc

According to Chris of Small Arms Solutions… the penetrator core in the 62 grain is not properly centered and causing fliers and lower accuracy. And because of the 62 grain being more intended for the machine guns like the FN Minimi.

I would like to see an armor penetration test between the two twist rates and grain weights.

I have a Rem. 700 with an 18-inch 1in 12 twist 223 barrel. 50 grain is .5 moa but 77 grain in any brand key holes and is all over the place

I remember the old video where Tim shot 1/7 16 and 20 inch ARs and a 1/12 AR at watermelons. The 1/12 AR was devastating, but the 20 inch 1/7 did ok too. I bought a 1/9 20 inch Colt MT6700 a d it was pretty accurate.

I'd like to see this same test on a Lead Sled with scopes swapped and sighted in on each rifle. That's damn good shooting for open sights but once you stretch out to 100 yards the scope would eliminate some errors. Great video though!

Interesting 👍🏻

I had a varmint bolt action .223 with a 1/12 twist 26" barrel, it would stack 5 rounds of 45 gr jhp on a dime but anything over 55gr was unusable. Twist rate matters a lot.

I recently built a Commando GAU-5A clone (ATF registered SBR) using Brownells 11.5" 1 in 12 barrel and shot it along side a 1 in 7 11.5" Ballistics Advantage (another SBR - love my SBR's). This was with 55 grain pills and the 1 in 7 did much better. This was the first time shooting the Commando clone so we'll see after it's broken in. Also, I was using irons with the Commando (of course) and a an EOTech holographic dot/circle with the other SBR, that might be a factor. In terms of coolness, the Commando gets an 11 out of 10 :) Pick your favorite retro and build one.