seating depth makes that much difference??

[jtoews80]

OK, I loaded up some 308 win starting @ 42.0 on up to 44.0 grains of IMR 4064 with Nosler B-tips. good load @ 44.0 groups were ok(1" @ 100 yds.), but great for hunting. I loaded another 20 rnds for hunting with, all using a weight sorted(175.5-176.0grn/case) lot of Fedral GM brass. I had some difficulty getting the seating depths perfect because 42.0 is a compressed load and 44.0 is a seriously compressed load. I ended up with 5 out of 20 rnds that the seating depth was out badly, the rest were perfect. Season is over and I took the 308 to the range for fun, except I haven't loaded much lately and all I had was my hunting ammo. 2-3shot groups, same powder, range, bullet etc. One group was 3.5" and one was 1.41" at 300m or 333yds. wierd. The depths were off by alot, but what the heck?

CC

 

[Ol` Joe]

In my experiance seating depth will make a difference. How much depends on the rifle.
I always work up my loads with the bullet "kissing" the lands and after I find my max I alter the seating in 0.005" increments until I find the COL my rifle prefers. The cartridge base to tip won`t however be a good measurement for doing this, you`ll need a comparator tool to measure from cartridge base to ogive.

 

[6ppcar]

Setting depth makes a lot of difference, sometimes moving the bullet only 3 thousand can really tighten a group.

 

[steve4102]

As Joe stated, measuring from the tip is not going to be very accurate. You need a comparitor that measures off of the ogive.

 

[old #7]

I am putting the finishing touches on a load for my rem 70 in 280 and tthe last thing I had to do was play with the COL.
I found the lands and set the first five loads .005 back. Then loaded five more at .010 and so on in .005 increments.
These are the results.

It's amazing what .005 will do
The last group should have been smaller but I jerked the trigger on the first shot. But 5 shots inside 1 inch @ 100yds isn't bad for a factory gun. :grin: :grin: :grin:
Are you crimping your compressed loads?

 

[jtoews80]

I haven't ever tried crimping. I rarely use bullets with a cannelure to set the crimp on. These were 180grn Nosler B-tips. I'll probably be doing the Northern reloaders version of saterday at the range until spring. Sizing and trimming all the brass I have on hand...... That is about 800 rnds of 308, 200 243, 160 30-378, 200 264, 100 30-06, 100 300 win 200 7mm Rem, 120 rnds 270. I feel a little cheap to say it, but at our local range we don't do anything with our brass. It gets tossed into collection pails and thrown into a garbage barrel. So I grab whatever I see as useable. In one day just before hunting season I recovered 6 boxes of 7mm, 6 boxes 270, 1 box 270 wsm, 1 325 wsm nickle 2 of 30-06. all in all 331 rnds of brass. I don't sell dies as a rule and have dies for 22 Hornet, 223, 22-250, 243, 264, 270, 280, 7mm rem, 308, 30-06, 300 win, 300 wby, 30-378 wby. Unfortunately, my brothers and dad seem to benefit more than I from the fact that I have kept buying trading and selling rifles for awhile. I've only got a 264, 308, 300, & 30-378 that I own now, and the 300 will be a 30-378 as well before spring.

 

[big rifle man]

Running the ogive of the bullet closer to the rifling does not gaurantee accuracy all the time. I have a Weatherby Mark v Ultralight that I tried that with. I got 180 grainers out of the case pretty far and was only able to shoot 2 inch groups. I backed the bullet into the case and found the further away from the rifling I got the better accuracy I got. I ended up with 1 inch groups with the bullet seated quite deep in the case. Understandably the Weatherby has a lot of freebore and this may have something to do with better accuracy when the bullet is seated deeper. Also, if you have a magazine rifle you can only place the bullet out as far as the length of the magazine will allow, (unless you desire a single shot)

 

[matts318]

42 grains of 4064 is a compressed load? I load up 44gr of that stuff and its not compressed, maybe just a little but the powder is just short of the neck of the case. I didnt realize that those federal GM cases had that much less capacity.