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View Full Version : Seating depth vs powder charge for consistent accuracy



Tbkahuna
09-10-2008, 07:30 AM
I have been shooting my Savage 12 FTR in .308 with Federal Gold Medal Match ammo. I have started handloading and need some help so I don't spend more time loading than shooting. The FGGM ammo shoots very well in my gun and my circumstances. I want to continue with it, since I am having so much fun, until I decide which part of true BR I want to jump into and pour the rest of my money!

The FGMM with 168gr SMK shoots at an average velocity of 2886 fps in my gun with an ES of 28 and SD of 8.7. I have measured the OAL and base to ogive length using a caliper and .302" diameter bushing like in the Hornady or Stoney Point caliper seating depth measuring tool. I measured 20 loaded rounds and got measurements of 2.140" ave with actuals varying from 2.135 to 2.151" in that same setup. That is not the OAL. It was 2.807" on average as I recall.

I made a dummy round and got several measurements for my "at the lands" measurement (using my tool) at 2.141". So, my thoughts are that the Savage likes ATL seating because it seems to shoot well with that ammo. Maybe it is the velocity it likes.

My initial hand load with Lapua brass, CCI BR2 primers and 43 gr. of Varget (weighed) and the 168 gr. SMK (weight sorted) gives me 2760 fps for average velocity, ES of 24.6, and SD of 8.1. Those were from my first run and were seated to match the OAL of the FGMM. Now that I have my tool for not measuring to the tip of the bullet, I want to further develop a load with the right seating depth.

I plan to start with seating ATL and try loading 43, 43.5, 44, and 44.5 gr. of Varget and check velocities and accuracy. I was going to use 3 rounds at each charge with seating ATL, out .005", .010", and .015", as well as jammed .005". That looks like about 48 rounds to load.

I am looking for any suggestions and guidance to make this work as well as possible. Should I start with just the powder charge variations ATL first, and see where the accuracy is best? I was surprised the factory FGMM shoots at 2886. Should I start with less powder or is less than 2760fps probably not a likely sweet spot?

Am I leaving anything out? The gun has a heavy stainless 30" barrel with 400 rounds through it now. It groups very well for me shooting it off range bags and the 2.5 pound trigger. I have a better rest arriving so I should get it better and more consistent for figuring out my hand load. With FGMM it shoots .53 MOA at 300 yards as my average from my last couple of sessions with me yanking it around in the wind figuring out what to do with wind flags. It shoots about .3 MOA at 200 yards, and 100 I don't know for sure because I was only shooting that when I first started. I do have some really good 100 yard 3 shot groups.

Thanks for your input.

Rob in Houston

mike in co
09-10-2008, 09:15 AM
this is best asked on another forum, like 600/1000 yd forum, or factory/hibred forum. you have a good plan start with the powder, then tune the length.

mike in co

Donald
09-10-2008, 04:46 PM
Rob,
Remember to change only one thing at a time in working up your loads.

Donald

Rustystud
09-11-2008, 05:04 AM
You will find lots of help at www.LongRange.com, there are forum threads just for Palma and F-Class TR which both specifically shoot 308.
Rustystud

SCOTTinVT
09-11-2008, 12:05 PM
The web site is longrangeshooting.com not longrange.com For the Palma and F class threads.

Scott

SCOTTinVT
09-11-2008, 12:12 PM
The website is in the title

Sorry for wasting the space.

Scott