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I purchased this BAR. 308 new in 2012. I bought it for pig eradication but wasn't having luck getting groups so it moved to the back of the safe. I pulled it back out 3-4 months ago, started looking at seating depth variations (w/in max magazine length) and noticed what looked like burr marks on bullet jackets before the lands were engaged. So I bought a Teslong borescope and started surveying the various short and long arm barrels, found the burrs (red in photo) copper that I hadn't removed and an alligator pattern on the lands.

Weeks of intermittent reading later I think I know that these barrels are hammered forged by FN and that hammer forged barrels are supposed to have a very smooth bore. I lightly spun oiled 1200 grit paper on a dowel at the barrel/barrel extension junction, resolved the burr issue and bore bright/Kroil'd the bore. The copper appears to be (mostly) gone but the pattern remains.

Do finally my first new member questions: are these marks from hammer forging? Are they "normal"? Should a hammer forged barrel appear to have so much relief in this pattern? Do I have a POS and that's why I wasn't getting groups with factory loads?

I've collected remains from several boxes of different 30 cal bullets (TTBC, Interlock, Nos AB, SMK, Hor RN) all 150 gr. and am working on max COL vs max magazine length. Then on to a uniform load of H4895 and sometime next year out to the range.

Before I start actually loading I'm interested to hear feedback on this narrative and particularly regarding the specific questions. I love a good challenge but if <2 1/2" groups are unachievable I'll just finally cut my losses and move on to another project.

Many thanks in advance and for all the info I've gleaned from this site as an observer in the past.

cf
 

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I'm not a huge Browning fan, but I have a couple. One thing I've noticed is Brownings usually mean quality outta the box, and come in several rifling twist rates. Having said that, I have read that most BAR's in .308 are in the 1in 12 range? If yours is in that range, you might try a heavier projectile to improve your groups. 1 in 12 is usually for 180+ grain projectiles and perhaps not fast enough to stabilize the lighter 150gn projectiles you've been using.
I've seen and personally dealt with this human error on several platforms, especially in the 6.5 Creedmoor arena. They are notorious for super MOA groups when projectile weight isn't matched up to twist rate. This may not be the cause of your problems, but it is indicative of super MOA groupings and has resolved this issue for me in the past.
 
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