Case Trimming

I know case trimming is not necessary for those shooting at close ranges and not for accuracy. However, I have been trimming my cases for a while now and I certainly do think it helps with my groups at longer ranges at the higher 12,000psi pressures I use. Most, if not all factory loads I tested remain at or below 9,500psi in my equipment.

I will try and add to this post as I load up and shoot the next few groups. I hope to try several groups and then see if trimming is needed after the third group. This could take some time and give plenty to talk about.

High Velocity loads and pressures generate nearly 18,000psi, those cases get stretched to nearly 1,314" only after a few uses. I won't be discussing those here.

Brass

Some new brass can be as short as 1.292" and as long as 1.300" from what I have seen. It is my understanding that a lot of folks try to maintain at least a .005" variation and others closer to .001" variation. But those guys are avid 500 yard groundhog shooters.

Although I have used several brands of brass, below is Winchester brass that has only been used a few times. Some measure as long as 1.302" and only one or two as short as 1.297". Regardless of length, all have been put in the trimmer and for those that got trimmed, I have been able to keep the variation down between 1.298" and 1.300", with the majority at 1.2985" for a .002" consistency.

Most handloading manuals call for 1.292" case length with their load data but I have been using 1.298" to 1.300" for some time now.

The CM trimmer and Wilson gauge seem to work well. A little slower to use but I like it better than the Lyman I was using. I do have the "U" clamp but with the thin mouth, holding it by hand is steady.

I can see that the chamber wall of my Uberti 73' might be slightly off on one side by the looks of this trimmed mouth. This pattern is fairly consistent on brass starting to stretch. Longer stretches trim more consistent.

After cleaning up the edges, I like to spin the mouth on a piece of scotch bright pad. The more I shoot, the more precise I try to get on my handloading components.

Winchester Brass fired only once or twice. All between 1.297" and 1.300" for an avg of .003".

Just some on-hand mods, making this Lyman trimmer into a case prep tool with removable tips.