Case length trimming consistency

[Koda]

How much does variations in case length affect accuracy? Do you only have to trim it when it approaches max, or should they always be trimmed to all be the same length?

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[RVTECH]

I trim (rifle only) after every firing. Some 'grew' some didn't. Depending on the caliber I reload all regardless of the length as I find those that didn't grow during shooting to be so close to maximum it has never been a problem however the times I have wanted 'maximum' accuracy potential I have always used cases that required trimming to MAX OAL and of the same brand. I like the look of all of them beveled and chamfered, bright and shiny!

I know some that only trim when approaching max - but it's either trim or measure so I just go ahead and trim them.

 

[TTSX]

I can tell you I took about .1" off my average group size when I started trimming vs just rolling with it. It's not a lot but it's more than nothing

 

[Koda]

I can tell you I took about .1" off my average group size when I started trimming vs just rolling with it. It's not a lot but it's more than nothing

Somewhere I thought I read that case length consistency was key. I'm just trying to determine what I should trim to since new cases don't start out at max length.

 

[bionic knees]

unless you are going for maximum accuracy you are overthinking again. for most of us if we can keep it on a 5 or 6 inch plate at 300 yds we are good to go

 

[TTSX]

Somewhere I thought I read that case length consistency was key. I'm just trying to determine what I should trim to since new cases don't start out at max length.

To be blunt, I use Lee hand trimming tools and have less than no idea what length I'm trimming to, just that all my cases of a given batch are done identically

 

[Koda]

unless you are going for maximum accuracy you are overthinking again. for most of us if we can keep it on a 5 or 6 inch plate at 300 yds we are good to go

will case length variations of up to say .010" either way put all bullets on a 6inch plate at 300 yards?

 

[TTSX]

will case length variations of up to say .010" either way put all bullets on a 6inch plate at 300 yards?

That particular factor,I believe, is going to be the least important detail to achieving a 2 moa group

 

[Koda]

To be blunt, I use Lee hand trimming tools and have less than no idea what length I'm trimming to, just that all my cases of a given batch are done identically

What Ive been doing is only trimming if the case exceeds maximum, but otherwise not paying attention to case length. My last ladder test gave a group of about 1.1" so I was just curious if I could improve.

 

[Koda]

That particular factor,I believe, is going to be the least important detail to achieving a 2 moa group

What if I wanted to achieve a 1moa goal?

 

[RVTECH]

I'm just trying to determine what I should trim to since new cases don't start out at max length.

If they are new, and less than maximum length just bevel & chamfer and load.

If some exceed maximum length then just trim to max OAL and load two sets of ammo - one set with the MAX OAL cases and those that are short, and see what your results are. You might be surprised to see they are very close in accuracy.

 

[TTSX]

What Ive been doing is only trimming if the case exceeds maximum, but otherwise not paying attention to case length. My last ladder test gave a group of about 1.1" so I was just curious if I could improve.

What if I wanted to achieve a 1moa goal?

My opinion is your powder charge and seating depth will play a more significant role than trimmed case length. Then there's the question of improving the Indian or improving the arrow. Perhaps you already have a .75moa load and just don't know it

 

[RVTECH]

My opinion is your powder charge and seating depth will play a more significant role than trimmed case length.

Ditto this - and I'll add consistent seating of the bullet with as little distortion as possible.

 

[Koda]

You might be surprised to see they are very close in accuracy.

My opinion is your powder charge and seating depth will play a more significant role than trimmed case length. Then there's the question of improving the Indian or improving the arrow. Perhaps you already have a .75moa load and just don't know it

then im probably just overthinking things as usual and will just worry about it when they go over max length.

 

[bionic knees]

measure, trim as needed after a few firings, inspect closely, put them back in the mix. this has worked well for me for decades.

 

[DizzyJ]

I personally don't trim every time I load a rifle case. If it grows to a point that's more than max OAL, it gets trimmed back to nominal or just below.

Powder, bullet, case and seating depth as well as runout will probably have a bigger effect on group size IMHO.

 

[Caveman Jim]

Measure, trim, load and shoot. The best accuracy comes from a great shooter.

 

[Koda]

Im just glad to read there is one less thing to worry about as I learn reloading trying to improve my accuracy and lower my standard deviation. Appreciate the tips from everyone.

 

[oremike]

I full length size then trim to the mid-range in case my cutter varies a little bit, then make a good ball park load to fire form the cases to my single gun chamber and to get the scope dialed in close. Once I've got a pile of fire formed brass I neck size only and check for case length and trim only those out of spec. This works for me but I'm only loading one load for one bolt gun at a time. I have a .223 for Varmints and a 300 Win Mag for every thing else.

 

[Mikej]

Measure, trim, load and shoot. The best accuracy comes from a great shooter.

This ^^ is why I'll never have great accuracy!

The Speer 14 was my first book. It gives "Trim To" and "Max Length". That's a .010" spread. I just decided to pick an arbitrary number under the max length and trim everything there. For instance, .30-06 trim-to is 2.484"- max length 2.494". I picked 2.487" because some of the cases need very little taken off. I'm using the ancient RCBS trimer too though. It might be different if I was using one of those fancy case trimmers.