Case trim length?

[CA_Shooter]

I load 6.5 creedmoor. Case trim length per the book is 1.910. Max per the book is 1.920

I loaded trimmed between 1.9110 and 1.9130

All other things equal, how much of an FPS change or deviation would be caused from the difference in trim length?

 

[Doug Beach]

An irrelevant amount, if any.

 

[MagnumManiac]

None, never seen a difference in neck length changing velocity.

 

[CA_Shooter]

So in other words I don’t need to be too concerned with the length? What about 1.910 to 1.9160? I spent about an hour today making sure all my brass was within the tolerance between 1.9110 and 1.9130, which seems as though it was wasted time.

Should I be concerned with 1.910 to 1.9160? My case trimmer hits this variation pretty much every time, whereas the 1.9110 to 1.9130 is made about 80% of the time

 

[JohnKielly]

The issue is that you might well get severe pressure issues if the neck of your case is so long that it enters the forcing cone for the bullet.

You might be able to find what that length is by making a chamber cast or using a proprietary case neck measuring tool. If not, you'd be smart to follow the recommendations.

 

[CA_Shooter]

The issue is that you might well get severe pressure issues if the neck of your case is so long that it enters the forcing cone for the bullet.

You might be able to find what that length is by making a chamber cast or using a proprietary case neck measuring tool. If not, you'd be smart to follow the recommendations.

I actually am within recommendations. I just want to know if I’m damaging accuracy.

 

[Bc'z]

A few thousandths in length isn't going to give you to noticable difference in bullet pull.
IMHO

 

[JFrank]

I load 6.5 creedmoor. Case trim length per the book is 1.910. Max per the book is 1.920

I loaded trimmed between 1.9110 and 1.9130

All other things equal, how much of an FPS change or deviation would be caused from the difference in trim length?

None

 

[jepp2]

You might be able to find what that length is by making a chamber cast or using a proprietary case neck measuring tool. If not, you'd be smart to follow the recommendations.

Brownells offers a chamber length gage by Sinclair that will allow you to determine the maximum length the brass can be for your chamber.
https://www.brownells.com/reloading...s/sinclair-chamber-length-gage-prod32925.aspx

The 0.006" trim length variation seems like quite a bit (for trim variation). Negligible affect on accuracy, but just surprised you get that much.

 

[AJC]

So in other words I don’t need to be too concerned with the length? What about 1.910 to 1.9160? I spent about an hour today making sure all my brass was within the tolerance between 1.9110 and 1.9130, which seems as though it was wasted time.

Should I be concerned with 1.910 to 1.9160? My case trimmer hits this variation pretty much every time, whereas the 1.9110 to 1.9130 is made about 80% of the time

 

[AJC]

So i don't have the spec in front of me but you said max length is 1.920, and you are beyond max at 1.930, Not everything we do is for accuracy, but safety is always a factor. Unless you measure and verify it is safe to run longer than max i would caution to trim as directed by the book.... DO NOT EXCEDE MAX UNTIL YOU VERIFY IT SAFE TO DO SO.

 

[topclass2017]

I trim any brass that is over 1.915", otherwise I leave it alone. Cuts my trim down considerably. Regardless of whether I trim or not I still deburr and chamfer all cases.

 

[DRNewcomb]

I like @jepp2's suggestion. The important thing is the neck length of your chamber.