reubenski
reubenski
2 posts
Joined March 2018

Flat based bullets in MBR

I did some research before buying a MBR for the 650. Found a lot of folks that had problems keeping a flat based bullet on a case while rotating the shellplate. Most folks said the fix was a Lyman X die. Basically an expander mandrel to open the neck. So I bought one. It expands the neck .003" but still doesn't hold a FB bullet. I started off just lightly balling the mouth and ended up filling expanding the neck. No dice. Still doesn't hold a Hornady 55gr SP.

Any ideas?
dillon
Administrator
dillon
3,074 posts
Joined July 2007

RE: Flat based bullets in MBR

The Lyman M die should open the neck enough that the flat base of the bullet drops well below the level of the case mouth. It isn't flaring as much as expanding the neck so the base of the bullet is a slip-fit.
reubenski
reubenski
2 posts
Joined March 2018

RE: Flat based bullets in MBR

I solved it by screwing the mandrel all the way down so that the case mouth was belling slightly from the stepped diameter near the base of the mandrel where it meets the stem. The main diameter of the mandrel only expands the neck of a sized (by the trim die) .003". That's only .001" over bullet diameter. The bullet dropper doesn't provide enough resistance to slip fit the bullet with .001" clearance.
dillon
Administrator
dillon
3,074 posts
Joined July 2007

RE: Flat based bullets in MBR

It sounds like you are using the die correctly. The Dillon 30M1 Carbine expander funnel is of a similar design, in that it has a square step to open the case mouth enough that the base of the bullet drops below the case mouth.