I am working up a new load for the wife's 25-06. I have found a powder load that will work but would like to tighten the group up. Should I move the bullet in ( shorten the Base to Ogive ) or lengthen it? I may be nuts but I like hunting loads to be 1 inch or less group and this load is close to that already but thought maybe some tinkering would tighten it up. Whats your opinion? Little more information-- 120 gr Partition, 51 gr-RL22, CCI primer & Hornady brass. COAL-3.123, Base to Ogive with Sinclair Nut-3.651

Every rifle I own the load is bumped .002-.003" off the lands. Except my AR.

I take that back. I beat my head against the wall trying to figure out why I never could get my 130 SST handloads to shoot as good as factory 130SSTs in my 270. Finally loaded them to the COAL stated in the Hornady manual and 1/2" for 5 shots. Now I load a 140 GK in that gun and those are .002" off the lands so who knows.

My starting point for rifle is just off the lands but short enough to extract without risking pulling the bullet.
Some rifles I will set to mag length and just look for the optimal charge.

If you’re not too deeply invested in the 120s I would try the 115 partitions. Many rifles shoot the 115s better. Some 1:10 shoot the 120s fine, some do not.

Just how much difference is there in 5 grains?

I’m the wrong guy to answer that, buts it’s proven itself out enough that if I can’t get something to shoot I will drop to the next weight down.

Ok, Thanks Daniel

Do you know what the twist is?

No I don't. It is a Tikka T3 .

Seems to be a common thing with .25-06 for some reason.

This is how I start.

Daniel, if you want to tinker, you can seat deeper in .005" increments and see what happens.

I plan to work with it after our last day to deer hunt which is coming Saturday. Group I got this morning was close to being a go but would like to help it.

Ditto.

I'm still relatively new-ish to reloading and this topic annoyed me for several reasons. From my deep dive, this was the ultimate conclusion. The only fail-proof way is to make groups and test it.
That said, I didn't want to do that for every single load so mag length is always a good place to start. Honestly, I have some loads for rifles I don't shoot often that worked better than expected at mag length so never played with it further. The following are a couple videos that are the basis for my loads that I really want to develop/play with.

The general principles presented here is what I abide by. There is a portion about what to watch out for when shooting the different groups to tell which depth is the node u want to target was helpful to me.
https://www.youtube.com/watch?v=oRXlCG9YZbQ or https://www.youtube.com/watch?v=oRXlCG9YZbQ

the next video around the 11 min mark is closer to what I now do because I actually like my Hornady tool.
https://www.youtube.com/watch?v=obTvUY5LQ3A

My 223 and 308 bolt are learning platforms and are the only calibers I've tried this on for about 5-6 different bullets. So far i am much happier with the results. I'm just trying to offer a slightly different perspective. I have no clue what is "truly the best" way to do.
Btw, it didn't make a HUGE difference. To contrast, figuring out a good charge weight yielded much bigger gains.

I’m trying this method. . It makes sense to me.

I tried Nosler Partitions in two different 26-06’s that were both accurate rifles and got same results around an inch or so. Occasionally I would get a better group but overall that’s about what I have come to expect and for its purpose that is good enough to do the job.

Or you could try some 115s.

You know, because I’m pretending everything is in stock and cheap.

Sako website lists the 2506 T3x as 1:10.

I worked up some additional loads and the only change I made was the COAL. I looked at Nosler's loading data for the 120 Partition and increased the COAL to match what they suggested--3.200. I plan to give them a try tomorrow if weather permits. I also checked SPS to see if they still had 115's. Daniel