Baffling baffle strikes

[1168]

I’ve got a friend with a SRD 556 QD can, and a Virtus 11.5” gun. The mount was installed properly, using a torque wrench. 3 of us looked down the bore, and believed it to be straight. Well, within the first mag, there was a major endcap strike. Upon inspection, it appeared that the projectile kissed a baffle, then went all nutso on the cap. Sounded great otherwise, lol. Probably best sounding can in our group.

So no big deal, shit happens. Gun and can took a trip to the manufacturer. They repaired the can, and said they test fired, good to go. Can came back with what appeared to be a larger bore. This time we got all paranoid and used an alignment rod. It was perfect. Looked down the bore; perfect, with lots of clearance.

10 rounds in, another endcap strike. This time, we don’t see any damaged baffles. WTF? So we look down the bore with the can mounted; still straight....lotsa clearance. We pull the can and check the mount. Still tight, still straight. Didn’t measure, but the brake looks like it could maybe pas an 8mm projectile. Lotsa clearance. Looking at the erosion on the brake’s baffles, there are a couple spots where the erosion is deeper, and is reflected on both baffles in those spots, as if a projectile is just barely hitting it. But how? Its so close to the muzzle and the apertures are huuuge.

I shot 60 rounds through it with various ammo at ranges from 5-30 meters at paper, unsuppressed, and found no evidence of anything unusual.

Obviously, the dude is going to work with the mfgr to resolve this, again. But my interest in how cans work drives me to wonder how this is happening? The thing mounts on a tapered mount, attached to a tapered barrel. Locks up solid. Appears good to go. There’s obviously some sort of voodoo wizardry in play here. Something something harmonic or something something turbulence, I dunno. In the meantime, we’re all launching hundreds of rounds of the same ammo through 6 other gun, can combos, with either 556 cans or 556 endcaps. No issues in many thousands.

Has anyone else had a similar issue with this can, or any other can? Any high-grade nerds know what is happening here?

[Clint]

Got a picture of the interesting marks on the brake?

[1168]

Got a picture of the interesting marks on the brake?

I do not. Resembles some sort of gouge into otherwise normal looking brake erosion pattern. BTW, 11.5” with brake is stupid AF without a can.

[JediGuy]

Curiosity here... Does a different can work fine on that barrel?

[1168]

Curiosity here... Does a different can work fine on that barrel?

Dunno. Its got a tapered barrel shoulder, so we would need to buy a shoulder adapter. Or a Q can. Or a Plan B/Cherry Bomb. Lots of options now that I think about it, I guess. Dude is pissed enough he bought a G upper and does not plan on effing with the Sig upper anymore.

[sandsunsurf]

One thing missing in this equation is ammo information. Could this be a case of a longer and/or slower bullet not being stabilized?

[1168]

One thing missing in this equation is ammo information. Could this be a case of a longer and/or slower bullet not being stabilized?

Hornady 62gr FMJ @2700 fps.

[markm]

Hornady 62gr FMJ @2700 fps.

Both of my cap strikes were with shit 55gr LC bullets. Hornady's 62 should be WAY better than LC ball. But that barrel may hate those bullets.

I'd try some 77s. I will no longer shoot anything but good OTMs in my can. (I used to thing the smaller/shorter bullets were safer)

[1168]

Both of my cap strikes were with shit 55gr LC bullets. Hornady's 62 should be WAY better than LC ball. But that barrel may hate those bullets.

I'd try some 77s. I will no longer shoot anything but good OTMs in my can. (I used to thing the smaller/shorter bullets were safer)

Thats not a bad idea. However, this barrel has launched a few thou of these with no issue, unsuppressed. They hit targets, and make round holes.

[markm]

Thats not a bad idea. However, this barrel has launched a few thou of these with no issue, unsuppressed. They hit targets, and make round holes.

There could still be some weird harmonic whip going on with the can mounted. I could be way off, but nothing else comes to mind if the can is on straight.

(I have a Saber Defense barrel that spins hornady 55 gr soft point apart. So... barrels can do odd things)