Is there a fixture out there (other than the Mk I, Mod 0 eyeball) that can also tell you if the FSB is mounted squarely? I've seen quite a few BMs that wouldn't zero without using up most of the windage adjustments due to FSBs that were mounted off-square.
That should be another issue addressed in your inspection/upgrade process.
That little carbine is ready to roll now!
Nice work C4.
My last two BM M4's needed the taller sight post. After calling BM to complain and order the sight post they sent it twice in two years with no charge. They seem willing to adress any issues their customers have. They offered to hand stake my BCG but instead of the shipping expense and downtime I did it myself. I'm certainly not going to make excuses for them but their rifles seem GTG after a few simple mods. I also strongly feel they should not need any mods for the price they are sold for. I haven't stake the castle nut yet as I plan to eventually add a different stock and mil spec tube, in the interim I check for any looseness everytime I use it. Instead of upgrading the bolt I plan to shoot it till failure then replace it with an upgraded MPI bolt. My wife now claims the BM M4 and had me put it back to it's original config. She likes the KISS principle of iron sights and standard M4 handgards. I transfered the KAC RAS, Aimpoint ML2/ARMS, Troy BUIS, GGG vert. grip to my new LMT with SOPMOD stock and am happy I also feel lucky to have two smooth running M4s for her and myself Next big decision will be ACR or SCAR
Looks like a pretty typical Bushmaster on arrival. The standard continues to be mediocrity.
A gun with that PM should be quite serviceable when live fire testing verifies function.
Grant- Did those come with a "CM" bolt?
2012 National Zumba Endurance Champion
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Grant,
I don't know what kind of machines you've got (if any), but I assume if you are pinning FSB's (as I've seen in the past), you've possibly got a mill?
If so, a number of jigs can be made to align and check the alignment of FSB's.
I know that Kotonics advertises that they "laser align" their FSB's before and during installation.
Might be something to look into.
Like you, I'm good at eyeballing them, and I can catch a FSB that's off by only a couple degrees with my naked eye.
Just a thought. I'm a total freak when it comes to the FSB being straight, after having a couple 6920's with crooked FSB's. (granted, I don't think Colt pinned them crooked, but rather, the torquing of the bbl nut caused the indexing pin to allow the bbl to rotate in the upper).
Anyhow, it's always nice to have a perfectly aligned FSB.
I know AR15Barrels.com (Randall I think is his name?) has a simple jig that he milled to check and re-align FSB's for customers.
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