MR1 reloading question ...

[Tikka223]

Folks,

I reload for the MR1 and have been using Winchester brass, 55gr VMAX, CCI BR-4s, and various loads of Varget. 26gr of Varget seems to be getting the best accuracy to date.

Once fired, I've been using a Redding full-length sizing die on the brass. The brass has been cleaned using an ultra-sonic cleaner.

My question:

Once fired, I find the brass comes out very dirty and "sooty". From what I understand, the MR1 is piston driven and thus there should be little gas blow-back into the chamber. Does this mean that I should only neck-size to get a better seal at the shoulder of the case?

Here is a pic of some fired cases:

 

[rnbra-shooter]

Not related to the question you ask, but how many times has the brass in the photo been fired? On several cases there are bright "rings" ahead of the extractor groove, which I would want to examine more closely and see if they are incipient case head separations, or not.

26 Varget in a .223 with 55 grain bullets is not a particularly hot load. Nothing wrong with that, especially if it shoots well for you, but you'll usually see sootier fired cases (especially in a semauto) with loadings with lower peak pressures (during firing, the brass doesn't expand as fully).

While a piston-driven semiauto is cleaner than a direct impingement design, there is still some residual pressure in the chamber and the barrel when the action starts to cycle - so there will be some gun gas that comes out of the chamber end (so you'll see sooting of your cases, of your bolt carrier, lugs, chamber area etc).