The idea of “over stabilization” is a bit of a myth.
By spinning faster than “optimal” any imperfections of the bullet are magnified by a small amount. Remember those bullet imperfections are causing inaccuracy in a “perfect” twist, just a little bit less than a faster twist.
My 1/7 twist shoots the 36gr Varmint Grenade just fine and loves BH 52gr Match.
For a fighting carbine the ability to use better performing heavy bullets should be the deciding factor.
I have given this some thought recently as well.
Mainly, because when ammunition was harder to come by, I could get 45gr varmint loads.
I never bought any, but in a pinch, I think I would be best served by a 1/9 bbl.
I know individual bbl’s very, but can you shoot 77gr better in a 1/9, or 45gr better in a 1/7?
I’m thinking strictly in an emergency type situation, not a well supplied training or military situation.
Nevermind, I guess it was just answered.
I have shot the Winchester .45gr in a 1/7 without any problems. IIRC it was very accurate.
I’m a little surprised that Todd is shooting 36gr Varmint Grenades without them blowing up.
Most of my guns are 1/7, with a couple of 1/9 thrown into the mix.
I shoot everything from 40gr to 69gr just fine. It’s rare, that I shoot anything heavier
I don’t have a single round of ammo less than 55gr and don’t see buying any.
My ammo stockpile is Q3131A, Q3131 (pre-98), Fed M193, Norinco 55gr, AE 55gr, Win STHP 55gr, IMI/LC/Win M855, BHBB 75gr, Hornady TAP 75gr, Hornady 5.56 TAP 75gr, and MK262 77gr.
My 24 Varminter is 1/9, all of the other barrels are 1/7 or 1/8 twist.
The SBR barrels are all 1/7 twist.
My findings have been the same. I’ve never had a problem with “over-stabilization” and I’ve shot as light as 40’s through a 1/7.
I would rather be able to shoot the heavy shit if needed and go with a 1/7 or 1/8 than have a 1/9 and not be able to perform as well with heavier ammo.
I have seen more problems with 1/9’s and heavier bullets than 1/7 and lighter rounds but YMMV. For an all around shooter I prefer a 1/8 but have no issues with a 1/7. I don’t own a 1/9 anymore.
Over stabilizing is not the problem it was once thought to be. Modern bullet manufacturing techniques have improved to the point that bullets fly true even when “over stabilized.”
In fact, the military is switching to 18" barrels on their sniper rifles because they have found there is no loss of accuracy if the barrel twist is changed from the previous standard of 1 in 12 to 1 in 10, the new standard for .308. Shorter barrels are better for getting in and out of vehicles and aircraft, especially with a can attached.
Thanks everyone for the replies. This has been very informative, makes me more comfortable with what I own, and changes the advice for my friend. Thanks again.
You’re lying. We all know that shooting 36-grain bullets out of a 1:7 makes the bullet spin so fast that the barrel gets scorched and the bullets and barrel self-destruct! 
Kidding aside, 40-grain and 50-grain bullets shoot VERY accurately out of my 1:7 barrels.
I have been following this thread and am glad everyone has explained this to me. My department policy requires us to shoot 55 grain bullets in our rifles as “duty rounds”. As a street cop, I wont see any difference in accuracy from say 100 yards or less using my 1/7 twist barrel…, correct?
Shouldn’t be a problem at all. The primary issue with very light-weight bullets in a fast-twist barrel is bullet disintegration, but this only happens with very thin-jacketed bullets that are DESIGNED to be high-fragmentation such as the non-ballistic-tipped varmint bullets (i.e. Hornady SPSX).
55 FMJs are robust enough that they don’t shed jackets mid-flight.
whats the most accurate and best self defense round for 1:9 twist?
Swat- Please limit the foul language.
You now owe me a Shiner Bock. Oh yeah, drinking an Icehouse after a long day.
My dept currently issues the Federal TRU in 55gr for our duty round. I can keep the rounds pretty tight around the eyes and nose on a silhouette at 100 yards. That’s prone with a T1 out of an 11.5 BCM.
Sorry, I always seem to fuck something up. 
I’ll gladly buy you a Shiner if you promise to stop drinking Icehouse.
wow…my first ar was a pre-ban hbar and it would key-hole the 55 ball ammo every now and then??
I bet those 40gr and under pills in a 1/7 are like a little grenade when they hit a critter.
Especially when you can load them to 3400 fps out of a 16" barrel!
You cannot “over-stabilize” a bullet. It’s either stable or unstable. What stabilizes the bullets is the spin it has. If it’s spinning so fast it’s not stable, it isn’t “over-stabilized” it’s unstable.
Twist alone does not impart stability to a bullet. It’s the RPM. A bullet needs a minimum RPM to be stable in flight. To get that RPM you must have the right twist and the right velocity. A bullet may stabilize fine in a 1:12 barrel that’s 24 inches long, but not from a 14.5 inch barrel. That’s because the velocity of the bullet is less from the shorter barrel and the bullet will exit at a lower RPM.
The trouble with tighter twists is bullet construction. With a frangible bullets are by nature fragile. At high velocities with the high RPMs imparted by tight twist barrels frangible bullets will fly apart from centrifugal forces.
My father developed a load for his 22-250 that was firewalled with a Speer bullet designed to explode when hitting prairiedogs at 223 velocities. Though the twist was rather slow in his Remington 788 (1:14 if I recall right) the velocities he was driving those bullets at had them near the edge of self destructing from the RPMs they were spinning. We called his loads the “Blue Streak Express” because they’d leave a faint blue trail of smoke behind them. We discovered that smoke trail was lead dust leaking out of the jacket from the stresses. That bullet was so close to self destructing that hitting something as light as sage brush caused it to rip apart. It caused jackrabbits to explode on impact.
The point of this is that a 1:7 twist may be what you want in carbine length barrels. It will make up for the RPMs lost due to the lessened velocity from shorter barrels
Perhaps the most concisely accurate explanation I have seen on the subject. Well put!
There are a ton of videos of 1/7" twists spinning bullets apart, 35-40 grain seem to easily spin apart not far after leaving the barrel.