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Bullet Seating Depth


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Excellent video from Sam Millard at Panhandle Precision on bullet seating depth.  There's alot of information out there on it, but the way Sam goes through information is almost like Army training - make it easy to digest, and understandable to all involved in the training...

I've only recently been interested in this, from a "measuring and fine tuning" perspective.  I did some experimentation for the Mk12 Mod 0, changing seating depths in 0.005" increments, and I hit a sweet spot that the specific barrel liked.  I stuck with it.  Ironically, that same seating depth for my 75gr Hornady HPBT load works excellently in all my other precision-based 5.56 guns.  So I never went further into it after that.

The 6.5 Grendel and the .300 Win Mag have me wondering, now. The Mk 12 didn't - that thing is boringly accurate at 600 yards, and will do 800 yards all day long.  The 6.5g and 300 Win Mag will go a hell of alot farther than that...  I've got my 6.5G load figured out now, and it works great in two radically different 6.5G guns. I haven't put alot of load development into the Win Mag yet. I'll pick up some special tools for checking/setting/adjusting seating depth for the Grendel, and see where it goes. It'll make a difference for the Win Mag, too.

Here's Sam's vid on checking max seating depth, and where to start and where to go on this stuff:



Edited by 98Z5V
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Its very interesting on how different rifles using the same bullet will have such different seating depths for accuracy. My friend and I just finished the Berger Bullet testing procedure which is for VLD bullets but could be used for anything I believe. We were using the 7mm 162 ELD match bullet My friends rifle was a 280 Rem and mine was a 7-08 on a LR platform.  Berger Bullets instructs to seat 6 rounds at .010, .050, .090, .120 off the lands those who don't mind jamming bullets into the lands start at .010 jammed, then .040, .080, .110 shot three shot groups of each seating depth and you will find your rifle will have a noticeable tight group over the other seating depths. Repeat the teat with the remaining 3 shots of each seating depth to confirm results. One then can fine tune the seating depth at .006 increments up and down for another 24 rounds. 

My friend found that his 280 liked the 162 ELD at .102 off the lands while my 7mm-08 was spot on at .050

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