seating depth vs accuracy?

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uchi

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its my understanding that different bullet seating depths create different pressures which should result in different points of impact right? whats an acceptable tolerance for this? would 5 thou be enough to throw off accuracy?
 
It depends entirely on the load and the gun. Some combinations are quite sensitive to changes in the distance to the lands, and some are not.
 
gotcha, i find im getting about 2-3 thou in oal difference at most, once i find a load that works ill start separating them based on length, thanks
 
There are bullets that are very sensitive to seating depth (Berger vld) and others not so much. The pressure change between seating depths are quite minimal in my experience but defiantly affect accuracy for many bullets. The method I usually use and many may not agree but it works for me is this. Start with a bullet seated .005-.015 off the lands(assuming it will fit in mag) then come up with your load like usual. After you have your most accurate load adjust your seating depth in .010 increments to see if you can tighten your groups up. Then you can fine tune more if you feel it's necessary.
Ignore the difference in your oal it is simply because the bullet is seated by the ogive and the length of your bullets vary slightly but in reality they are seated the same
 
ripitup911 said:
Ignore the difference in your oal it is simply because the bullet is seated by the ogive and the length of your bullets vary slightly but in reality they are seated the same
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:agree: 100%. Your seater should not be touching the pointy end of the bullet. Measure the length on a bunch of bullets then seat them and measure OAL. Chasing the OAL will drive you crazy.
 
uchi said:
gotcha, i find im getting about 2-3 thou in oal difference at most, once i find a load that works ill start separating them based on length, thanks
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nope dont do that, bullet tips are NEVER the same bullet to bullet, you will want to messure off the ogive of the bullet. not to the tip. as ripitup911 said.

i start at .015thou off the lands and get my best load, then try .010 and 005 off, and refine from there. factory throats tend to be quite long, and some times its not possible to get as close to the land as you want.
 
My .22 K hornet won't shoot worth a c@#$ if the bullet is'nt actually touching the lands, then it shoots an inch at 100yds.
The last .223(cz) I had was'nt shooting the way I would have liked with bullets about 3 thou off the lands. My buddy (who had the same rifle) told me to come back to 7 thou off the lands, and that cut my groups almost in half.
I have messed around with my .308 and it does'nt seem to care(so long as the bullets are 165 gr, it shoots about 2" at 100yds nomatter what I do)
You just gotta keep trying stuff and see what works for each gun.
 
right on thanks for the help and great info guys. ive got some sierra bullets loaded up and ready for load development. put some down range today that had a bit of run out while out with some buddies and they seemed to shoot alright. gonna see what the actual loads i made for this task will shoot like and then once i find one that works ill start playing with some powder fine tuning and then length.
 
are you useing the SMK? they are probably one of the most tollerible bullets for jump/jam. im my expericay iv seen verry little to no accuracy differance from .025 off to touching the lands. and are my "go to" to set an accuracy baseline fr any rifle
 
Just loaded some .303, 174 grain bullets. I started one into an unprimed case a little, then chambered it to see how deep it would seat the bullet. Bullet never even hit the lands!
I just seated it about one calibre into the case(at least I have decent neck tension), and hoping for the best!
 
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