Neck Length

[284stak]

Have a 270 Win factory chamber. Measured the neck length using a Sinclair chamber gauge and found that the neck length is 0.028 longer than spec. QUESTIONS: Other than knowing I can let the neck length grow than much more --- is there any value in knowing the above info? That is a lot for the necks to grow --- is there any problems trimming the necks to spec --- relating to accuracy, case life, throat erosion, etc?

 

[284stak]

Help!

 

[landcbeitner]

Your question is a little confusing. I have to assume you're saying that your rifle has a long throat, and you measured it to find that your OAL to touch the lands is .028" longer than the standard OAL for a loaded cartridge. Is this correct? Your cases should be trimmed to length for consistant neck tension and accuracy. Long factory throats may require you to seat the bullets further out than the OAL spec. Some bullets (like Berger VLD's) are sensitive to jump, and others are not. You must experiment with your OAL to see how the bullet likes to be seated. This is part of your load development. I hope I understand your question correctly, if not please explain again (I think that's why you haven't gotten a response).

 

[284stak]

Thanks for the reply:
The question is not related to throat length but to the chamber neck length.
A chamber length gauge measures the true distance from the bolt face to the end of the chambers neck. The throat length is from the end of the chamber neck to the lands.
Knowing the exact chamber length can tell you how much longer your chamber is compared to the published chamber length for case trimming purposes.
In my 270 Win - my chamber length is 0.028" longer than what the recommended trim length is.
My questions were: Other than knowing I can let my cases grow that much more - is there any other usefull info from knowing the true chamber length? Should I let the cases grow that much or just trim them to published case length?
Hope this clears up any questions as to what I am asking and appreciate any replys.

 

[ss7mm]

My questions were: Other than knowing I can let my cases grow that much more - is there any other usefull info from knowing the true chamber length? Should I let the cases grow that much or just trim them to published case length?

The useful information is the fact that you know your exact chamber length. .028" isn't bad. I've seen them a lot farther out than that in a factory chamber.

I wouldn't "let them grow" as you will have all different neck lengths. A good plan of attack would be to measure all of your cases and trim them to the length of the shortest one. That way they would all be the same length and you could use that as your trim to length.

What is the length of your shortest case length as compared to your actual chamber dimensions?

Published lengths etc. are related to SAAMI dimensions. If you want to get the most you can out of a factory chamber and round, then get a little anal and make sure they are all the same length. This will help with consistency when it comes to neck tension although, in the end, with a factory setup, you may not be able to shoot the difference but if you feel better then sometimes that's half the battle.