POF Rogue mystery (and danger?)

[Slug Thrower]

Hi All,

My first post. Found this site both while researching technical data, and now when looking if others have seen the issue that I am seeing on my POF Rogue .308 carbine. (16.5" 1:8 barrel). It's basically new and I had it on the range this weekend for its second trip. I had three types of ammo that I was going to use to sight it in and compare at up to 200 yds. I did get the rifle sighted in for 200 yds, and I have a small comment at end on appropriate ammo for the Rogue, but the money part of this post is this mystery:

I fired 66 rounds through the Rogue, with about 2/3 of that being the Sierra GMM. 3 times during this session I was surprised with a double fire at what should have been a single trigger press. I thought I was pretty solid on bench rest and bags. Always the next trigger press would yield a normal single fire.

Later I was glad I had picked up my brass because I found two of the weirdest spent cartridges I have ever seen. The two were very different from the rest, but similar to each other. I have attached a picture showing one of the two, with a normal spent casing for comparison. The outliers appear like this:
- Hard ridges formed in the case from the bottle opening to approximately 1/2 way down the body of the bottle.
- These are regularly spaced at 30degrees from one another (12 total around the case)
- Viewed at the mouth, rather than a round opening it is a 12-sided polygon (with a dent on one side from ejection).
- Soot runs between the ridges down the outside of the case, completely blackening the rim and the slot preceding it (normal brass is virtually clean except for the marks left at POF's proprietary "e2" chamber notches at the neck of the bottle)
- Both of the ones I found (a third if existing is unaccounted for) are the Sierra GMM 168gr. Very possible to have lost one in the rocks. Or not.

I hesitate to guess how this could happen other than aliens riding large white balloons abducting my brass and performing experiments on it, but my best guess otherwise is that these rounds fired when they were not completely seated in the chamber, where the chamber then had a couple of mils gap around the cartridge. The frontal portions of the case then expanded outward in such a way that an invisible striping in the brass stretched, was blown outward, and then formed into the ridges against the chamber. Thus the ridges stop where the case is thicker. The expanding gasses then run down the body of the case from the mouth and find a way out back at the firing pin and/or ejector components.

Has anyone seen anything like this, or have an explanation? Thanks for your time and thoughts.

And the anticlimax - how did the POF Rogue eat ammo:

After having purchased the Rogue, I did find concerns about the fast 1:8 twist, so in addition to the 147gr ammo that I had purchased for hole punching, I had purchased 2 types of heavier Federal Premium rounds to see if they would behave any differently. The plan was to sight it in for the 147, which was also the middle trajectory in the calcs that I had run ahead of time, and then compare to the higher priced and heavier rounds.

1) Sellier and Bellot 147gr FMJ 7.62x51
2) Federal Premium Sierra Gold Medal Match 168gr open tip .308
3) Federal Premium Trophy Copper 165gr .308

First, the 147gr's were all over the place compared to the 168's. I was shooting with a 2MOA red dot so not going to really make claims about any of these other than to say I might see sub-2" groups at 100yds for the 168's or more than twice that on the 147's. So yes, I am starting to wish I had the 1:10 barrel that they sell now versus the 1:8 that I got last fall.

 

[Trigger Monkey]

I hesitate to guess how this could happen other than aliens riding large white balloons abducting my brass and performing experiments on it, but my best guess otherwise is that these rounds fired when they were not completely seated in the chamber, where the chamber then had a couple of mils gap around the cartridge. The frontal portions of the case then expanded outward in such a way that an invisible striping in the brass stretched, was blown outward, and then formed into the ridges against the chamber. Thus the ridges stop where the case is thicker. The expanding gasses then run down the body of the case from the mouth and find a way out back at the firing pin and/or ejector components.

LOL No...that's not how any of that works. Part of what you're describing before it trails off into fantasy land about invisible striping is an out of battery detonation and almost never ends well for the cartridge, the gun, and the shooter. One of those looks like it was fired from a G3 and the other one from a POF.

Google "G3 spent brass"

 

[Slug Thrower]

So my brass really was abducted and had experiments performed on it by the alien race "G3". Makes sense now!

Thank you sir. I had tried every search I could think of, was flabbergasted that I didn't find anything, but I didn't know the secret "G3" incantation that unlocked the door. I started with a clean lane, the head marks matched mine, I had had the misfires, and the next thing I was providing comedy on snipershide.com. It is much easier to believe that someone else left a few cases in the concrete seam of an otherwise clean shooting lane and I picked them up.