450Bushmaster.net

Hoot wrote:Here's the diagram as measured on my rifle.

The 15 degree slant I refer to is the tilt that the bur / mill / stone, whatever, is tilted toward the top of the receiver while grinding. In other words, don't position the cutting tool perpendicular to the opening. As WC said, many folks who build uppers for this and other thumper calibers just use a Dremel with a carbide bur or rotary stone and I've seen some of their work. It looks fine. Obviously, don't balance the upper in your lap on a stool and do it. Affix it firmly to a work surface and set up a rest for your hand holding the dremel. Make many light cuts and it doesn't have to be aerospace precision. Just don't cut into the cover detent area.



Good Luck

Hoot

EDIT

Oops! In my haste to get the image made and annotated, while the wife was tapping her toe, waiting to go get groceries, I printed it upside down. The top rail is on the bottom in the picture. It doesn't effect what needs to be done. Also, in case you don't realize it, the widening is accomplished by only removing material from the top half of the port where the small step lip is located.

Hoot

Hoot wrote:So, you took it off of the bottom of the port as opposed to Bushmaster taking it off the top. I guess it doesn't matter which side gives way as long as one of them does. On an aside, I believe the 458S and 50B have a fatter case (~.545) versus the 450B (~.500). I'm guessing as I only have a .50AE spent case I found at the range to measure.

Thanks,

Hoot

Hoot wrote:Here's the diagram as measured on my rifle.

The 15 degree slant I refer to is the tilt that the bur / mill / stone, whatever, is tilted toward the top of the receiver while grinding. In other words, don't position the cutting tool perpendicular to the opening. As WC said, many folks who build uppers for this and other thumper calibers just use a Dremel with a carbide bur or rotary stone and I've seen some of their work. It looks fine. Obviously, don't balance the upper in your lap on a stool and do it. Affix it firmly to a work surface and set up a rest for your hand holding the dremel. Make many light cuts and it doesn't have to be aerospace precision. Just don't cut into the cover detent area.



Good Luck

Hoot

EDIT

Oops! In my haste to get the image made and annotated, while the wife was tapping her toe, waiting to go get groceries, I printed it upside down. The top rail is on the bottom in the picture. It doesn't effect what needs to be done. Also, in case you don't realize it, the widening is accomplished by only removing material from the top half of the port where the small step lip is located.

Hoot

Blasternank wrote:So Hoot or anyone that can answer this: Do you basically only have to take material off of the top rear section of the ejection port? From the upper left section to the detent spot? i want to try this but I'm not too good with tools like this and am afraid I'll screw it up.

Thanks.