I'm loading 300 Win Mag Norma and Nosler brand brass. The brass generally comes brand new 2.6000"-2.6100" plus. SAAMI is 2.62".
Yes I know it was probably a stupid question but I learned a long time ago that the only stupid question is the one you don't ask. I just want to be as knowledgeable about what I'm doing as I can.
So my next question is this:
If after firing....the brass is measuring in the 2.6165" neighborhood should I trim it back a tad to even them all up, assuming my goal is maximum consistency and accuracy? Or should I wait until they exceed 2.62"????
Is that a resized measurement? I would not trim if it is. check length after you resize it and make sure they will chamber easily. After resizing they will be a bit longer. I generally trim every other reload. Some brass will stretch more and has to be trimmed every reload.
Some folks trim to same length every time to keep everything consistent.
2.620" to 2.600" is OK. When brass reaches maximum of 2.620" then trim back the standard .010" or less. Its possible to maintain a 2.620" trim length. This requires fl sizing & trimming every loading. Each brass must be checked for length & chamfer and deburr also.
There is a "safety zone" built into most chambers of around .010" If a longer then maximum trim length shell is chambered, the case mouth will not get crimped into the chamber. There are tools & ways to measure chamber length.
Just a FYI... When I couldn't find 300 RUM brass I was resizing 7mmRUM brass to 300 and they all ways came up short like .020 or .030 short. It took 2 firing and 2 resizing to get them full length. But they still shoot good even on the shortest stuff.
The 300WM SAAMI chamber has .040” clearance BEYOND 2.620”.
I actually measure this amount in each barrel/rifle and keep my brass trimmed .010” form that measurement in my hunting rifles. In my comp guns it is kept within .005” to reduce carbon rings.
I have 3 hunting rifles in SAAMI 300WM chambers and a comp F-class Open rifle with 3 barrels, all 3 are chambered with the A191 chamber which is shorter in the head to shoulder length, but the clearance at the end off the chamber is only .025” longer than 2.620”.
All rifle chambers have clearance at the end.
For the 300WM, the new cases are held at the TRIM TO length of 2.610”, not the MAX LENGTH of 2.620”
Rule of thumb is to trim to 2.610”, or in other words, .010” LESS than MAX length, this is for ALL cases.
Thanks....that is very interesting. That is the kind of information for which I was looking. And....based on that information I am in good shape because that is exactly how I have been trimming my cases.