Changing seating depth, which way?

preacher · Oct 28, 2021

My Mod 77 7x57 is trying to shoot. My Lapua factory with 170sn does under an inch(rounded groups too) for the first three, then next 2 open up group. Skinny barrel. I measured its COAL ogive/oal with a Bullet comparator and got 3.730" (av) my handload with 150 NP seated .020 off the lands ogive/oal measures 3.68 and I get 2 in and one out (3 shots) maybe the 2nd or third, but 2 close and one apart, (wide 1 3/4", 2 closest 1/2"). Do I seat them deeper or further out? I have have plenty of magazine length. I can't get 3.730 with the 150 w/o jamming. Best I can get is 3.715 (again Bullet Comparator measure. I don't want to burn up more components than necessary, of course.
The good thing is "this is the first 7x57" I've owned that was accurate (under 2") with anything!!!
Started over 25yrs ago with a Mod 70FWT, later another Mod 70 FWT, then a Mod 700 classic, and an old M93 or 95 ( I for get) that shot factory S&B 173 but nothing else. This old tanger was a Safe Queen, even had an older Leupold 2.5x8 with friction dials (that actually give the correct dialing!)
Its trigger is crisp, no takeup, but 4# measured. All I did was take rifle apart, cleaned/oiled, put back together, used Loctite on the action screws gorilla tight front back with middle snug. Tightened scope bases/rings. That's it. Old School baby! I just forgot whether to seat out or deeper???? Arrgh. Help

preacher · Oct 29, 2021

Its best load was 50gr R17/150 PT. This according to QL, and still keeps me under 63K, which is where I prefer to shoot in a strong action. It seems I read somewhere that if your groups are kind of open, seat out further, if two or three are tight with one or two more opening up the group to seat deeper. However, the Bullet comparator on those Lapua factory rounds shows they must be riding into the lands a bit. they shoot very well, which is what had me compare the ogive on the 150PT. I think I will load up four deeper and four further out, .010" each and see what happens. I'm just so tickled to have a 7x57 that even "wants to shoot", lol.

jimbires · Oct 29, 2021

if you're are at the lands , I would try to avoid going deeper in the lands . I have one rifle that is in the lands , and it shoots very well like this , but it's a pain in the neck . if I eject a loaded round the bullet is stuck in the bbl , dumping powder down through the action and trigger . I won't chamber a round until I have a shot . if I don't take the shot after I chamber one , I shoot it off at the end of my day .

preacher · Oct 29, 2021

I too have had a round get stuck/pulled case off/dumped powder in the action, it was for a 223 I was playing with, and I hate that! I am way too OCD on reliability so stopped seating closer than .010 to lands anymore, ha. I start at .020 or, for monos .050. I'm using some Norma cases with this handload, BR2. Rifle was tightening up as velocity increased.

George Foster · Oct 29, 2021

I have followed the following advice I got years ago for 3 shot groups.

With two touching and one out seat deeper.

Triangular group seat out longer.

Also for my rifles I have found .050 off the lands seems to be the sweet spot.

preacher · Oct 29, 2021

Thanks Uncle George! I was just about to report I "remembered" (Senior Moment) that advice from 'somewhere". ha I will seat some deeper and see what happens. The Lapua rounds shoot into a nice, sub moa triangle, what I call "rounded" I am going to shoot at least four rounds/group next time since I'm this close. Would it be worth it to go in .010" increments or smaller, say, .003 to .005"?