Trim Length (Peterson Brass)

[Drewdemon]

I just received a lot of Peterson brass, 6.5CM, and wanted some guidance on trimming. Up until now I’ve been using Hornady once fired (by me) brass. The case trim length is 1.910, and I’ve been trimming that back to 1.890 (Giraud). Should I stick with the same formula for the Peterson brass?

Thanks!

 

[spife7980]

For exacting answers having a reamer print would be helpful to know what exactly yours was cut with. A chamber cast is even better. You can also use the sinclair chamber gauge to measure how long your neck is.

That said, if it was a saami reamer then it should be close enough to this without worrying about the above.

The max is 1.920 with an acceptable range of .020 less than that. Trimming back to 1.890 is excessive. Trim to 1.910

 

[Drewdemon]

For exacting answers having a reamer print would be helpful to know what exactly yours was cut with. A chamber cast is even better. You can also use the sinclair chamber gauge to measure how long your neck is.

That said, if it was a saami reamer then it should be close enough to this without worrying about the above.

The max is 1.920 with an acceptable range of .020 less than that. Trimming back to 1.890 is excessive. Trim to 1.910


View attachment 7055552

Thanks...again

 

[Ranger188]

1.890 is short.
Most will trim to 1.915 and that will cover 90%+ of your brass.
Some will be a little longer and some will be shorter and might grow into it.
Ideally you measure them all, and see what the shortest is and trim all to that.
Throw out the couple that are really short. ( 1.910-1.915 is ideal)

 

[Drewdemon]

For exacting answers having a reamer print would be helpful to know what exactly yours was cut with. A chamber cast is even better. You can also use the sinclair chamber gauge to measure how long your neck is.

That said, if it was a saami reamer then it should be close enough to this without worrying about the above.

The max is 1.920 with an acceptable range of .020 less than that. Trimming back to 1.890 is excessive. Trim to 1.910


View attachment 7055552

What effect will excessive trimming have on the bullet? SD/Spread? Accuracy?

 

[spife7980]

What effect will excessive trimming have on the bullet? SD/Spread? Accuracy?

Its more of it will just make more space allowing for gunk to get in your chamber etc. It could have an effect on accuracy but I think it would be pretty minimal unless you have one hell of a rifle.