Well, I had to send the ROS-05-S nipples back to Track of the Wolf. They are listed on the site as 1/4x28 but don't fit the GM bolsters. I could have sworn that was the correct size. Anyone know for sure?

GM's are 1/4 x 28...

I am going to hold off on ordering, Pete, did you try yours in the mk 85?

No I have not - it is not here yet.

I used to get some special nipples for some people that had jimmed the threads or had very worn or oversized threads and it was the base not the top that was oversized, I had to use a special oversized tap to cut the threads to the right size. I do not know if they are still available as I have been out of the business since 1991 but I can tell you that they would not screw in to a normal 1/4 X28.

Your name is Pete?

Cool name.

I fear that Semi is correct the .005 oversize if the threads not the post...

Although did you try inserting a cap on one of the nipples you got to see if they were tighter?

maybe you got one of the non repaired barrels that used the italian thread size? I remember GM doing this and then using heli coil to repair it to the correct thread size.

WELL, I have been called a lot of things but thats new,

No I ordered the correct ones (site has them as 1/4x28) but they came in and the labels on the bags said .255x28. So I believe it is like Lemoyne said - the threads were oversized not the top. In fact the Win #11 caps fit the nipple very slopply.