bullet jump increments??

I'm beginning to play with bullet jump in my .308. Shooting 175 SMK, I've dialed the powder charge down to the most accurate load at 42.5gr Varget. Only wanting to deal with one variable at a time, all loads were set at .008" off the lands.
I've just loaded some at -.005", and I'm not sure what to load next. -010'? -.020". How much of an increment do I want between the loads to see a difference? I'm currently low on these bullets and don't want to waste any, nor do I want to buy more if they won't shoot well. The current load of 42.5 Varget, 175 SMK, and -.008" off the lands, yields a .440" group @ 100yds.
The next question is how much of a pressure change will I get by setting the bullet back -.010 or -.020, etc? I'm not at max charge, no pressure signs. But I'm getting 2890fps, with is inexplicable (maybe my chrono is off)
My ultimate goal is to develop a 1000yd load. My 168's shoot very well at 500yds. (sub MOA), but I'm reading that they won't do well at 1000yds.
FWIW, the rifle is a DSG 11VT with Vortex Viper PST. Chamber measurement CBTO is 2.218 with this bullet. OAL comes to 2.275 @ -.008". (not that OAL is important)
Thanks for any advice.

Bergers site has a great way to effectively find optimum lengths while still doing a minimum of loading (wasting bullets & powder)

http://www.bergerbullets.com/getting...in-your-rifle/

Typically if you've not seen any pressure signs at a given OAL then seating deeper will for the most part not nearly be as critical for pressure spikes as it would be if you were starting at a given point and then begin to stuff bullets.

if i had a load that shot that well at 500 that would be my load.
7 gr of difference in bullet weight wont be a game changer.
just remember today might be great and tomorrow might not be.
thats just how it goes. no one who set a group record at 1000 yds
ever broke their own record or even duplicated it.
so its best to count your blessings on the good days at those distances.

Quote:

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Originally Posted by yobuck

if i had a load that shot that well at 500 that would be my load.
7 gr of difference in bullet weight wont be a game changer.

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That's what I thought at first. But reading articles from well know sources say that a 168 is fine at midrange, but won't retain enough energy to go 1000 and stay supersonic, becomes unstable. I haven't had the oppourtunity yet to test the 168's at 1000 as my 1000 yard facility is two hours away and I'm reliant on someone else to get access to it. Having the 168's perform well at 1000yds would just be too easy, and I'm not that lucky. So I'm developing the 175's to test at the same time.

I would suggest
-10 -40 -70 -100 -130 -160

Then narrow down from there. Yes I've had some rifles group well at -.160. But most will fall in at -.010 to -.020 from what I've seen.

I have a 30/06 that likes a .160" jump for 165grn NBT's. ;-)

175 SMK in my Savage 308 likes .010 jump the best, which is consistent with the various SMK bullets I have looked at so far. I typically evaluate in .005 increments from .005 up to .025 for SMK, so I haven't look at the longer jumps mentioned. Within this range I have not noticed pressure rise problems, and you are at a fairly low load with 42.5 Varget so I would not be concerned. Nice groups so far!

I usually start right on the lands, then a couple thou off the lands then go to .010, .020, .030, .040 and see what happens. I haven't had a gun that shot with any accuracy over .020 off of the lands so I never tried going any further.
Darrell