Went shooting this morning at the local range. We can only shoot at 25 yds. or 100 yds. at this range, so that's all I can do there. I've been playing with 150 gr. Hornady RN bullets (#3035s) and Hornady 170 gr. FNs, the #3060s. I'm working up different loadings of Winchester 748 and Hodgdon H335 (because "it was there"; I happened to already have some on hand) to try to find something that groups the best. All groups were shot with my cataract afflicted eyes looking through my receiver mounted peep with a Patridge post up front. Group in the top photo was shot last, after I adjusted the peep some.
For funsies, I shot some factory rounds and reloads of 150 grainers at 100 yds., mostly to fireform some brass. Not really groups to be proud of, but again, with iron sights and my eyes at a hunnert, I'm okay with 'em.......

From some groups of rounds, I was having the primers "back out" somewhat. Probably as much as 015" or so? No mushrooming of the primer, or craters around the firing pin divots. These rounds all fed, fired, and flung out reliably. Some were different factory rounds, some were my "starting point" reloads. With the reloads, as soon as I upped the powder charge, the backing out was pretty much not happening. I've read that this occurs in lot of .30-30 rifles, and for the most part, isn't really anything to worry about. It seems to be the nature of a beast for a cartridge that's sized to fit ANY chamber of ANY .30-30 rifle, is designed to headspace on the rim, and sometimes loaded to "safe" levels for older guns out there in service. Again, not really anything to worry about given no other signs of excessive pressure I mentioned above.
Even with my old eyes and iron sights, I noticed a kind of "trend" with some of my reloads. The rounds that I've shot before then resized tended to group a bit better than with the cases I was given that were shot from another rifle, or some factory rounds. These were the rounds that I set my FL sizing die up a bit from the manufacturer's recommendation ("Raise up the press' ram, screw the die down until it touches the shellholder, back the ram down, then screw in the die another half-turn"). I (and many others) don't do it that way. The catch is you do need a way to measure your fired and resized cases to do this right.
I have a Hornady Case Comparator I use with my digital calipers. I can fire a round, then measure the case's length at the shoulder to a repeatable datum point with this tool. I can then set my FL sizing die to "bump" the shoulder down by, say, whatever amount I choose. I'd like to bump it back a consistent .002"-.004", but my press/die combo doesn't seem to hold things quite that tight. I try to resize where the shoulder datum is around .003" shorter than it was after firing, but seem to get a span of .001" to .005" bump back. So far, it's worked out well.
I can measure factory rounds, or reloads set by the book, and it seems that they seem to run as much as .03"-.035" shorter than what my chamber needs. That's a lot of brass movement to fill up a chamber when a round is fired! Now, I realize our lever guns in .30-30 (and other bottleneck rimmed cases) are supposed to headspace off the rim. But they don't necessarily have to. And with a stackup of cartridge rim tolerances, chamber dimensions, and other factors, may not be the absolute best way to full length resize a 30-30 case meant for just one certain rifle.
Some advantages are that you work the brass much less when you move it back to size this way. This helps extend the case life versus moving the case around the amount I got by following the die maker's instructions. It fits the chamber in your rifle way better, and makes the firing sequence more consistent. For my rifle, it seemed to help tighten the groups a tad. Feeding, firing, and extraction have not been issues.
Some disadvantages are that your ammo sized this way might not fit in another of your rifles. For that kinda deal where you reload for multiple 30-30s, you probably do need to follow those die maker's instructions so your rounds will chamber. It requires a bit of slowing down to make careful measurements and adjustments, It adds more steps. A very dirty and/or rough chamber could be a problem. I'm pretty good about cleaning my gun, so that seems to be a non issue for my rifle.
I've done this for years with my bolt action .30-06. I actually took it a bit further, and seat my bullets for that gun within .015" of the rifling. The magazine allows room for that sorta thing, and it helps tighten up groups on that particular gun. I have an RCBS Precision Mic setup for that, along with a Redding bench rest micrometer adjustable bullet seating die. I wish we could do that with our .30-30s, but needing to crimp at the cannelure kinda sets our bullet OAL, and how close to (or how far from) the rifling our slugs can sit.
Anyway, something to think about and discuss. I'm the sort of Anal OCD person that wants as much accuracy as I can have with a rifle. Whether or not it might influence the outcome of a hunt at most ranges game is shot can be debated forever, I suppose. I just feel a bit more "confident" knowing the bullet should go where it's supposed to, if I do my part. And that's the biggest variable in this whole deal, most likely.