Trimming to chamber length

[Richard Jones]

Hi mate. Appreciate the concern. Again my procedure to get the chamber length was:

1) Get 3 once fired cartridges from my current rifle

2) Deprime, resize to -0.002" headspace

3) Trim down the necks to significantly under SAAMI minimums

4) Insert the Sinclair chamber length gauge (

) and seat the gauge at a rather high level

5) Insert the brass w/gauge into my chamber and close the bolt

6) Carefully remove and measure

7) Repeat with multiple measurements and different brass (removing and reseating the gauge each time)

Let me know what else I could do to be sure of my chamber length.

That's the way I do it, altho' I remove the ejector.

 

[223Randy]

That looks like it should work ok. Just wanted to make sure you were not going to crimp a neck when closing the bolt with a bad measurement. pressure can go up that way

 

[scyzer]

That looks like it should work ok. Just wanted to make sure you were not going to crimp a neck when closing the bolt with a bad measurement. pressure can go up that way

No worries - I appreciate you looking out for me!

 

[Jackmonkey]

I just posted a question about this on another forum. Mine concerns my Rem 700 in .243 Win. I also measured the chamber with the Sinclair gauge and came up with 2.080-2.081. The maximum case length for a .243 Win is 2.045 with a recommended trim length of 2.030-2.035. That seems like a lot of free space in front of the case to me. I know that the .243 is notorious for case stretching but it may never grow that much.

It appears that the consensus is to let the cases grow to within 0.010 of the actual chamber length, correct?

 

[SheepDog]

You can use short brass or brass that is within .002" of the chamber length. Cartridge length, by itself, will make little difference as long as the bullet is seated to the same distance from the lands. The longer neck can add to bullet support but it can also add differences in tension. I trim my brass to the chamber because I only size part of the neck and leave the rest of it to help center the case in the chamber. I do this more for case life but it seems to help with the accuracy in SOME of my rifles. I have never found it to hurt the accuracy in any of my rifles.
That being said, your rifle may respond differently so the only way to find out is to experiment. Work with what works in your rifle.

 

[Brians356]

I just posted a question about this on another forum. Mine concerns my Rem 700 in .243 Win. I also measured the chamber with the Sinclair gauge and came up with 2.080-2.081. The maximum case length for a .243 Win is 2.045 with a recommended trim length of 2.030-2.035. That seems like a lot of free space in front of the case to me. I know that the .243 is notorious for case stretching but it may never grow that much.

It appears that the consensus is to let the cases grow to within 0.010 of the actual chamber length, correct?

Most new cases arrive fairly close to the SAAMI trim-to length (for 243 Win that's 2.035"). If your cases are currently at least .045" shorter than your chamber, would you mind letting us know how many times you have to fire and resize them to grow an additional .035" in length?
-