Mk262-Sierra77gr HPBT, charged with 23.5gr varget. Case trim length suggestions.

[hawkeye9]

Hi,
Any suggestions on case trim length (.224 cal) for bolt action 26 inch barrel and 1:7 twist would be much appreciated.
Thanks.
Hawk.

 

[memo43]

I trim my brass to SAMI specs, after the chamber is cut to the same. If you know the reamer print in which it was cut then you will know what the max length will be.
Powder charge and seating depth are obviously barrel/rifle dependent, but since you are dealing with a bolt gun and not sure if you are running them from a mag. I am going to assume you are not based on your barrel length, work up loads there is TONS of different methods on the forum one which I have found extremely easy is the Eric Cortina method


Memo

 

[hawkeye9]

I trim my brass to SAMI specs, after the chamber is cut to the same. If you know the reamer print in which it was cut then you will know what the max length will be.
Powder charge and seating depth are obviously barrel/rifle dependent, but since you are dealing with a bolt gun and not sure if you are running them from a mag. I am going to assume you are not based on your barrel length, work up loads there is TONS of different methods on the forum one which I have found extremely easy is the Eric Cortina method


Memo

Thanks for the reply memo43.
The Hodgdon website suggests a trim of 1.750 for that load and bullet weight. I use the wilson case guage to keep it within SAMMI specs (1.760 -.020) but have never went below 1.755 as a trim length.
I will look into seeing if I can get info on the reamer print (this is new to me) as the rifle is a factory second hand bolt action rifle. I feed the rounds through the port as a single shot though is does have a mag capacity of four rounds which I rarely use.
Thanks again.
Hawk.

 

[amlevin]

I trim my brass to SAMI specs, after the chamber is cut to the same. If you know the reamer print in which it was cut then you will know what the max length will be.
Powder charge and seating depth are obviously barrel/rifle dependent, but since you are dealing with a bolt gun and not sure if you are running them from a mag. I am going to assume you are not based on your barrel length, work up loads there is TONS of different methods on the forum one which I have found extremely easy is the Eric Cortina method


Memo

Take a factory or hand loaded round, put some 'scratch hiding crayon" on the bullet right next to the end of the case. The marking should be around 1/8" max. Chamber the round and remove it. There will be a clear mark where the second shoulder of your chamber is. Measure from case base to this mark, subtract 10-15 thousandths from this and that is what your cases can be trimmed to. Just remember, the closer you run the case mouth to the second shoulder the more often you should trim to avoid problems.

Personally I just trim to 1.750" and let it go. Doesn't affect the sub .25 MOA I get from my .223 Bolt action with the same bullet as the OP's.

 

[waldo1979]

Ive heard from other shooters that the biggest problem with a nominal trim length is carbon ring build up in the chamber. I think the biggest thing is that brass is trimmed uniformly. The problem (as I've been told) is variances in trim length results in bits of carbon scrapping off and making its way into the bore. I have a giraud triway trimmer which references off the shoulder.

I use 1.755" for trim length for my CLE chamber, but you're probably safe up to 1.760". Check your chamber specs.

 

[hawkeye9]

I trim my brass to SAMI specs, after the chamber is cut to the same. If you know the reamer print in which it was cut then you will know what the max length will be.
Powder charge and seating depth are obviously barrel/rifle dependent, but since you are dealing with a bolt gun and not sure if you are running them from a mag. I am going to assume you are not based on your barrel length, work up loads there is TONS of different methods on the forum one which I have found extremely easy is the Eric Cortina method


Memo

Take a factory or hand loaded round, put some 'scratch hiding crayon" on the bullet right next to the end of the case. The marking should be around 1/8" max. Chamber the round and remove it. There will be a clear mark where the second shoulder of your chamber is. Measure from case base to this mark, subtract 10-15 thousandths from this and that is what your cases can be trimmed to. Just remember, the closer you run the case mouth to the second shoulder the more often you should trim to avoid problems.

Personally I just trim to 1.750" and let it go. Doesn't affect the sub .25 MOA I get from my .223 Bolt action with the same bullet as the OP's.

Thanks amlevin i will give this a try.

 

[hawkeye9]

Ive heard from other shooters that the biggest problem with a nominal trim length is carbon ring build up in the chamber. I think the biggest thing is that brass is trimmed uniformly. The problem (as I've been told) is variances in trim length results in bits of carbon scrapping off and making its way into the bore. I have a giraud triway trimmer which references off the shoulder.

I use 1.755" for trim length for my CLE chamber, but you're probably safe up to 1.760". Check your chamber specs.

Thanks waldo1979 for the feedback. I don't know that trimmer but will check it out.