This is my first time loading rifle rounds. I just used a crimped case and seated bullet method to find where my lands are. I came out with a measurement of 3.376 plus or minus .001 inches. I understand you should seat around .03 inches off the lands. If I used this approach I get rounds with an overall length of .346 or about 6 thousandths over the SAAMI standard for .270 win. Is it okay to be slightly over this standard with COAL?
Chamber OAL vs SAAMI OAL
- Thread starter MattE93
- Start date
The "standard" is so factory ammo will fit in factory rifles from a multitude of different manufacturers. 30-06 ammo made in Europe will fit in your Japanese rifle because the manufacturers of both use SAAMI specs for chambers and cartridges.
However, you don't need to be concerned about any rifle except your own. As long as they chamber and cycle in your rifle then you are good.
However, you don't need to be concerned about any rifle except your own. As long as they chamber and cycle in your rifle then you are good.
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So where did you get the idea that you should seat .030" from the lands? Some bullets may shoot better at .010", and some may shoot better at .070" off of the lands. With monometal bullets, I start at .050" off of the lands.
.030" isnt a bad starting point for a jacketed bullet.
Longbow338
New member
- Location
- Barrie Ontario
I've run some rounds up to a full .150 longer than SAAMI OAL with no issues whatsoever. I wouldn't get any closer than 0.010 from the lands though. For a hunting rifle I would recommend starting at SAAMI OAL and move forward from there in .010 increments to find the sweet spot. The accuracy of certain bullets is much more affected by the distance they have to jump to the lands than others. For measuring the distance to the lands, Hornady makes a nifty little tool, I believe it's a worthwhile investment for anyone who reloads.
It's a safety measure to allow the bullet to start moving and pick up momentum before it hits the rifling in order to prevent dangerously high pressure build up. It's a standard starting point stated in most manuals and then you can decrease the distance while observing the fired case for signs of high pressure. Different calibers and cartridges behave differently and yes, some like to touch the lands for best accuracy but others will develop excessively high pressure. Remember, you're about to have 40-50,000 psi in the chamber on the average, sometimes less but sometimes more and half of your head is directly behind that bolt that holds all of that pressure together.
