By most reports (and I do NOT want to debate this), most 1:7 barrels are fine with 55gr pills, BUT NOT ALL of them. So why take the chance?
You'll be fine doing what you're doing with a 1:8" (or at least as fine as 55 ball can be, which isn't), but you've been mislead by half-truths.
After installing LITERALLY hundreds of barrels into AR's in my life, and using 55 ball and 50 V-max's as my proving and function testing ammunition, I'm very confident to say the only 1:7" barrels which have trouble with 55grn bullets:
1) Barrels which are too long and push bullets too fast, increasing RPM's past the integrity limit of the bullet - this is usually >24" in my experience
2) Barrels owned by someone who only ever tried ONE 50/55grn factory load which didn't shoot well (which was often fired offhand with irons by inexperienced hands) who later chose to vilify the bullet weight as the exclusive reason the rifle didn't shoot well
3) Barrels owned by someone who compared 55 ball surplus ammo to some premium heavier bullet and then ran around the internet screaming about how their rifle likes the 69/77SMK's but can't shoot well with any 55 grain bullet they've tried
4) Barrels which simply don't shoot worth a piss with any bullet of any weight
5) Barrels which only exist in the imagination of the internet liar trying to validate whatever twist rate vs. bullet weight table they found online
sionicsweaponsystems.com
