OAL??

[NorCalMikie]

I will try to word this question so everyone will know what I'am asking and thinking.
Got a 6BR barrel coming and the first thing I will do,even before it is installed) is get a measurement for bullet contact to the lands.,4 or 5 different bullet weights) Got about 200 rounds loaded long and am waiting to set the final OAL.
The question is:
What thoughts do you use to determine the OAL.,mag length not a problem)
I have seen some bullets "jammed" as much as .012 and more. Into or off the lands,how do you decide? What do you go by to make your decision? A jam will increse pressure?
Some bullets like a jump.
Any and all opinions will be appreciated. Thanks. Mike.

 

[Forum Boss]

I fire-form the cases with the bullets into the lands about .020" past first "touch" as measured with a Stoney Point comparator.

.010" or so into the lands is a common practice that works well fwith a lot of bullets for a lot of different shooters.

Yes, going into the lands will increase start pressure. However, with the short 6BR you may find that .005" or so into the lands shows LESS pressure than, say, jumping .025". That's a .030" difference and it reduces case capacity. I definitely saw this in my own gun with Varget and Lapua 105s.

I advise folks to start at .010-.015" into lands. If that doesn't work, try .005" in. If that doesn't work, I'd say go immediately to .015 jump. When you jump the bullets, and this is just my opinion, you want to be far enough out that the bullet releases cleanly and can center itself in the bore prior to hitting the rifling.

I can't prove that last point, and I do know some people having good luck "just touching." The problem there is that you'll see differences of up to .005" in base to ogive measurement with production bullets. That means some of your bullets may be touching while others may not.

Bottom line: Land contact for fire-forming with a safe load. Then try .010" in or .015" out. Chances are one or the other will give good results and then you can fine tune.

 

[NorCalMikie]

I've got the Stoney Point and needed inserts to set the OAL. I use the RCBS Compitition seater die so setting the OAL is not a problem. Sounds like there is no "set reason" to jam or jump the bullets.
Load them,try them,and see what works best for each bullet.
Sounds to me like a good reason to go to the range and burn a little ammo. As if I needed a reason!
Just saw that my CC was billed for the barrel I ordered so it won't be long before it shows up and I hit the loading bench and get to work on my 6BR ammo. Savage switch barrel in 6BR? Got to love it!
Anticipation got to me today and the old barrel has been removed. Spin that new barrel on, do a little bedding and it's play time. :thumb: