1/12 and 62gr. bullets for .223

I saw a unit try to zero M16A1s with 62 grain ammo once in the early 90s after somebody ordered the wrong DODIC. Not a pretty event -- my recollection is that everyone was getting big, sloppy patterns at 25 meters and some weapons were keyholing at that range.

There is a reason why 62 grain in M16A1s is considered wartime emergency use only, and even then if I remember right, it was not to be used for targets past 100 meters.

I have a 1-in-12 bolt gun. I've only shot 2 bullets through it in that general weight range, a 60 gr V-Max and a 68 gr BTHP (also Hornady).

The 60 gr V-Max shoots ok - about 1" groups at 100 yrds. (The rifle will shoot dime size groups at 100 with the 53 gr V-Max.)

The 68 gr BTHP keyholes impressively at 50 yrds - so I've obviously never tried group size at 100...

I have a 1/12 twist barrel bolt gun as well. It shoots 55 gr. fmj's very well, but it keyholes 62 gr fmj's badly at 50 yards. I've heard that the military 62 grain bullets are too long to stabilize because of the steel penetrating insert.

I had a Ruger bolt rifle in .223, IIRC it had a 1:12 twist. It wouldn't shoot 62 gr worth a hoot, 55gr was better but not great. Cheap WWB 40gr HP however, shot extremely accurate in that barrel.

Every barrel is different; sometimes a bullet shoots well even if it shouldn't. Shape of the bullet base and speed can also make a difference. All one can do is try some in a specific barrel and see how well it works.

Yup, tried putting M855 through an A1 just for fun and had keyholes at 25m. 193 through an A2 works alright but not the other way around.

Sierra I believe makes a semi-point bullet in that weight range that is a flat base with a very blunt ogive intended for use in the 1:12 twist rifles. The full spitzers and boat tailed bullets are very likely going to be too long to be stable. The M855 bullet is definitely going to be too long.

Never tried the green tips through it, but did try some 69 grainers through my T/C Contender Super 16, they keyholed very nicely from 50 feet on out..what a lesson.

Yup. That's the way it goes.
I think twist rate is overstudied these days, if you stick to a standard twist and standard bullets, you will do OK.
But that does not mean you can ignore it, especially if you are fooling with the .223 which the army messed up some time ago.

My 1/12 bolt gun will stabalise 60 grain partitions but they are on the edge. There is a marked difference between them and the 55 grain SGK.
The 40 grain V-Max will drill a single hole if you can hold it there but the heavier bullets just cant compare.

Remember, it's not the weight of the bullet that causes instability problems, it's the length.
All else being equal, heavier bullets tend to be longer than lighter bullets, but bullet composition, long ogives and boattails can also affect stability.

I've seen an old 1/12" twist AR-15 that would shoot inch and a half groups with the old Speer 70 grain semi spitzer flat base. The same rifle usually shot two and a half inch groups with 55 grain M-193 ball. With 62 grain M-855 ball the bullets wouldn't even stay on a paper plate at 50 yards. When we fired them at an old railroad tie from 40 yards, the bullets were hitting sideways.

About the time the A2s came out Dr. Martin Fackler got a hold of a batch of green tip. He found it shot poorly from a 1-14 twist bolt gun he had, though rounds were barely keyholing at 100 yards that is the holes were oblong rather than round and the groups were four inches from a MOA rifle with 40 grain bullets

Lacking a 1-12 AR15 we used a 1-12 AR-180 to fire the Green tip and got groups of about 3 inches with no evidence of key holing at 100 yards on the next lane , the same day as the 1-14 test. This AR-180 did get tighter groups with 55 grain M193 ball, but no keyholing or severe scattering was noted.

Interestingly a Colt Canadian type M-16A2 with Full auto rather than the American Burst at this time was found to shoot 55 grain M193 into larger groups than the green tips. Oddly a COlt HBAR A2 was found to shoot 55 grain BETTER than green tip with supposedly the same twist, but a heavier barrel.

I think temperature, air pressure and humidity all play a significant part in the variations of performance here and perhaps barrel harmonics.

I note that if you go to the 10/22 folks and talk about the Mexican 60 grain SSS ammo that most will tell horror stories of its use in standard Ruger barrels, but a few will show decent groups shot with the same sort of rifle an ammo. The differences being temoerature, pressure and humidity and perhaps....barrel harmonics.

The answer is try it and see if it works for you.

-kBob

The difference is that no matter the specs, every rifle is different and will "like" different bullets and different loads.

kBob
What was the barrel length on the AR-180?
The barrel on the AR that I refered to in my previous post was a 16 inch Colt "pencil barrel", a longer barrel is going to increase velocity, which increases RPM's and thus aids in stabilizing longer bullets.

For instance, if we figure a 150 fps difference in velocity between 16" and 20" inch barrels when shooting M855 (please don't flame me for those numbers, I just got 'em from a quick web search), the bullet from the 20" barrel at 3100 fps will be spinning at 186,000 rpm but a bullet leaving the muzzle of a 16" barrel at 2950 fps would only be spinning at 177,000 rpm. 9000 rpm isn't a huge difference, but with a bullet already on the outer edge of its stability envelope, it's probably enough to make a significant difference.

Problems caused by imperfections in the barrel, such as excessive wear or a nicked crown will greatly increase the chances of what would normally be a marginally stable bullet becoming instead a completely hopeless flyer.

Swampman said:

Remember, it's not the weight of the bullet that causes instability problems, it's the length.
All else being equal, heavier bullets tend to be longer than lighter bullets, but bullet composition, long ogives and boattails can also affect stability.

I've seen an old 1/12" twist AR-15 that would shoot inch and a half groups with the old Speer 70 grain semi spitzer flat base. The same rifle usually shot two and a half inch groups with 55 grain M-193 ball. With 62 grain M-855 ball the bullets wouldn't even stay on a paper plate at 50 yards. When we fired them at an old railroad tie from 40 yards, the bullets were hitting sideways.

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Finally someone said it! It's not WEIGHT, it's LENGTH. There's a huge difference in say a Barnes .224" 62 gr. TSX and a Sierra .224" 63 gr. SMP. The TSX has no lead core, so it will be a much longer bullet, and thus require a faster twist, than the Sierra SMP.

When I was a kid, long before .223's with 1 in 9" twists, my Dad had a .222 Magnum built for deer hunting and specified a 1 in 12 twist so he could shoot 60 gr. Hornady SP's. It still shoots them well.

35W

Originally Posted by 35 Whelen
Dad had a .22 Magnum built for deer hunting and specified a 1 in 12 twist so he could shoot 60 gr. Hornady SP's

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Isn't the .22 magnum a rimfire? How'd he pull the bullets to reload the 60 grain Hornady's and how did he crimp the bullets in place once he did? To my knowledge nobody makes a shellholder small enough to fit the rim so it's very difficult to use a collet type puller and an impact puller used with rimfire would probably be WAY too noisy. I've pulled a few .22 rimfire bullets for use in .223 subsonic loads, but it involved a collet puller and inserting the whole .22 shell through the depriming hole in a .308 shellholder, it was WAY too much of a pain to ever make a habit of it.

Sorry to ask so many questions, but you started me thinking, a .22 magnum barrel in a 1/7" twist would be awesome for suppressed shooting if loaded with 90 to 100 grain bullets. Even the .22 Hornet really has too much case capacity for good ballistic uniformity at subsonic velocities but that .22 mag case would be perfect!

I noticed that you, like me, are from Texas, I'm pretty sure that a little bird once told me that its been illegal to hunt deer in Texas with a rimfire for over 60 years.

If you think it proper, feel free to reply via PM, I don't want to totally hijack the OP's thread.

Swampman said:

Isn't the .22 magnum a rimfire? How'd he pull the bullets to reload the 60 grain Hornady's and how did he crimp the bullets in place once he did? To my knowledge nobody makes a shellholder small enough to fit the rim so it's very difficult to use a collet type puller and an impact puller used with rimfire would probably be WAY too noisy. I've pulled a few .22 rimfire bullets for use in .223 subsonic loads, but it involved a collet puller and inserting the whole .22 shell through the depriming hole in a .308 shellholder, it was WAY too much of a pain to ever make a habit of it.

Sorry to ask so many questions, but you started me thinking, a .22 magnum barrel in a 1/7" twist would be awesome for suppressed shooting if loaded with 90 to 100 grain bullets. Even the .22 Hornet really has too much case capacity for good ballistic uniformity at subsonic velocities but that .22 mag case would be perfect!

I noticed that you, like me, are from Texas, I'm pretty sure that a little bird once told me that its been illegal to hunt deer in Texas with a rimfire for over 60 years.

If you think it proper, feel free to reply via PM, I don't want to totally hijack the OP's thread.

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Edited to insert missing "2".

35W

Edited to insert missing "2".

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Darn!
I guess it's back to the old 5.75 Velodog idea...

As others have stated it's the bullet length or the ogive (cylinder length) that matters. With that said it's usually safe to say that the lighter the bullet the shorter the ogive or cylinder of the bullet. My AR180 with a 1:12 twist shots 55 gr ammo just fine but won't shoot 62 very well. My Mini 14 with 1:10 twist prefers 55 gr.
I have said many times on this forum that I believe the best universal twist for all 5.56 ammo is the 1:8. It's better than the 1:9 for the heavy stuff and shoots the 62 as well. I believe the 1:7 is too tight for most of the ammo we normally use in the sportsmans world and it's popularity comes from the military use of it.
Most bench shooters use the 1:8 over the 1:7.

carbine85 said:

As others have stated it's the bullet length or the ogive (cylinder length) that matters.

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The ogive is not the cylindrical portion of the bullet. That is the shank. The ogive is the tapered or curved portion that transitions from the shank to the meplat.

I believe the 1:7 is too tight for most of the ammo we normally use in the sportsmans world and it's popularity comes from the military use of it.
Most bench shooters use the 1:8 over the 1:7.

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Define "bench shooter". 3-gunners mostly go with 1:8 because it's the common twist for high quality stainless barrels, not because it is better suited to anything in particular. I will allow for the shooting of the 75gn AMax and the 77gn SMK over the 1:9 but a 3-gunner doesn't need either of those bullets because they really offer nothing over the 69gn SMK out to 300yds. As far as benchrest shooters go, they use the slowest twist rate that they can get away with. Guys trying to stretch the .223s legs step up to at least a 1:7 if not a 1:6.5 to bring the 80 and 90gn SMK into the picture.

My 1/12 twist likes 40gr vmax and nothing heavier than 55gr.