Hello Everybody, Could some please tell me what the milled notch is on the muzzle brake?
I have many references of the M103 but haven't found any with this feature. What's the best way to correct it? Thanks!
http://www.rbmodel.com/picture.php?dir=35B132

The notch is correct.



Per my references, the early M58 had a cylindrical muzzle brake/counterweight with two holes, which was found to be ineffective and/or succeptible to erosion and was cut back leaving the two notches.

Thanks, But that isn't the the milled portion I'm talking about, it is not at the end of the muzzle ( Not the two slot notches)but one on the the side before the fume extractor, it looks like it could be a mounting for a muzzle reference device like on a M1 or Leopards 120mm. You can see in the pictures from RB???
http://www.rbmodel.com/picture.php?dir=35B132

it's where the bolts that secure the counterweight go. I managed to find this by googling:



If you enlarge, you can make out "counterweight key", "counterweight lock", and "3/8(?)x 1/2 hex head bolt". The groove corresponds to a groove in the muzzle where the lock and bolts would go to secure the counterweight/muzzle brake from turning.

That's awesome and explains that groove! Thanks. But I still haven't seen that groove/counterweight lock on the cut back version of the M103A1/2. The shorten counterweight without brake cured the erosion problem so I'm taking that it would not have to be replaced and wouldn't shift or was permanently secured? Could RB's counterweight just be the earlier version cut back. Just want to know what I can do to make it correct.

it is correct. RB Model got it right. it would still have to be removable in order to remove the bore evacuator.

Fort Lewis, right?

Got to visit last year.

Cool Nice closeup! I was assuming it had to be on the top. Last time I saw one of these beasts in person was at Aberdeen at 5 mph 15 years ago! Thanks Brian!