Rifle Case Trim

[NHshtr]

Hopefully, I can get your thoughts on the topic of rifle case trimming.
Reloading manuals don’t give any tolerances with their case trim dimensions. And we know you don’t cut the whole bunch on exactly the same dimension.
When it comes to trim length on rifle cases, I usually use +/- .003” as acceptable. I’m not sure how much case-to-bullet tension is affected in that range. What tolerances do you use? And do you see much of an effect with variations larger than +/- .003”?
Also, how low is too low on trim length? I’m aware of the headspace issues for an oversize case, but how low below trim length do you find acceptable, safe and useful?
Thanks.

[The Happy Kaboomer]

I trim my cases to the built in trimmer stop length. Chamfer and load. Neck tension holds all bullet well. Never ever had a problem.

[5shot]

Most of my manuals show a maximum case length and a trim to length. The .30/06 for example is 2.494" max with a trim to length of 2.484". Back in my precision shooting days I bought a L.E. Wilson case trimmer. It requires a different case holder for each "family of cartridges" such as .243 Win, 260 Rem, 7/08 Rem and .308 Win can all use the same case holder. It will trim cases consistently within .001". I doubt if that sort of precise trimming is necessary in a factory production rifle and doubt if .003" variation would be noticeable on paper.
Case trimming is my least favorite part of handloading but when cases reach maximum I grit my teeth and start cranking. Case trimmers have progressed a lot since this 45 year old Wilson but someone else will have to chime in on the latest developements.

Case trimmer.jpg (55.77 KiB) Viewed 2210 times

[NHshtr]

You're sure getting the most out of that Wilson!
I'm using a Lyman Universal with a drill to drive the cutter. I also have a Lyman Express which works pretty well.
Ever have cases that you found to be shorter than you would use? If so, how much shorter than Trim length were they?

[Mags]

Unless custom crimping each round, I would think that case length tolerance would affect aggressiveness of the crimp on the bullet.

[5shot]

You're sure getting the most out of that Wilson!
I'm using a Lyman Universal with a drill to drive the cutter. I also have a Lyman Express which works pretty well.
Ever have cases that you found to be shorter than you would use? If so, how much shorter than Trim length were they?

I haven't encountered that much with rifle brass. I did have a fairly recent experience with a bag of Winchester .44 magnum brass that had several cases that were way short. As Mags pointed out, when using a heavy roll crimp that would make a big difference, especially so if you were using a slow burner like H110. A consistent crimp would be critical for accuracy. In a rifle where you are just using case neck tension and there is no crimp cannelure my guess is a few thousandths of case length would not make as much difference.

For the last decade or so I've become a fan of Starline brass. Starline has convinced me they are more consistent. I had a batch of .44 Spl brass from Winchester a few years ago where the case mouths were cut off uneven by over .010". So when a roll crimp was applied you'd get a heavy crimp on one side and barely any crimp at all on the other. To their credit they did send me a couple bags of new brass that were just fine.

[NHshtr]

I had a couple of experiences like that with commercial rounds with "short" cases. One was Hornady 44 mag loaded with 240 XTPs. The cases, unfired, were 1.265". So, .010" shorter than "trim length" and the bullet was seated at 1.590" about .010" shorter than most manuals. So the crimp looked good and they shot well. But when I want to use those cases again, I need to watch the OAL to assure a good crimp.
The other issue was some Winchester ammo in .308 Win. that I bought to compare with my load. Those cases, unfired, were 1.990 to 2.000" or .005" to .015" shorter than Trim spec. The bullets had no cannelure, so not crimped. They didn't shoot so well from my rifle. Not as good as my load. I still have those cases, but they're socked away until I figure out whether it's worth dealing with them.
Certainly don't want to mix those in with cases at 2.005" trim. I think there'd be a worsening of groups.

[Pitchman1968]

Although I ream the primer pocket, trim, and chamfour each case I reload, I am particularly careful in trimming cases for my M1 Garand .30-06, and .30-40 Krag. My experience is that with semi-auto, lever action, or Krag rifles, case trim lengths should not be longer than +.002" over the manual's stated C/L. Too long of a C/L can affect those rifles' ability to properly cycle a round into the chamber.

[NHshtr]

Although I ream the primer pocket, trim, and chamfour each case I reload, I am particularly careful in trimming cases for my M1 Garand .30-06, and .30-40 Krag. My experience is that with semi-auto, lever action, or Krag rifles, case trim lengths should not be longer than +.002" over the manual's stated C/L. Too long of a C/L can affect those rifles' ability to properly cycle a round into the chamber.

I hear ya. That could also cause crushing the case around the bullet if it does ram in. How much case trim length tolerance do you tolerate? Is it only Case trim length plus.002"? Nothing below that?

[Pitchman1968]

NHshtr,

I can't remember having any short cases with new brass. With each piece of new brass, I lube, f/l size, trim, and chamfour the case prior to measuring it. Said another way, i am not concerned about factory new rifle brass being too short.

[Hatchdog]

I can’t respond to your question about trim tolerances but I will chime in on new brass. Recently I purchased a 250 pack of Starling 300 BO brass and checked the length on all pieces. 100% of them were .001 - .002 under “trim to” length. This surprised me as I would have expected Starling to produce the brass to trim to length. Not a big deal but interesting just the same.

[NHshtr]

Starline makes good brass. Whenever production machinery is used to cut an item, not all pieces will be cut to the exact same length. Hence, we work with tolerances. .001" to .002" variation is very good for brass. As I've indicated, I've found commercial brass with much wider variation in length in loaded ammo.
I don't know what the widest variation is that can exist before it begins to negatively affect the performance of the ammo.
Hence I stick with +/- .003". I find that keeps my loaded ammo performance consistent. I was looking to see if other reloaders used a wider or more narrow tolerance when they trim and why.
If after cleaning and full length resizing, I find, say a .308 Win case with a case trim length spec of 2.005" to be 2.009", I'll trim it. If I find one to be 2.007" I won't. Would you do the same?