Help with seating depth

[WhelanLad]

Okayyy.. where to start.

So I loaded up some 120gr Sierra pro hunters in the 7mm08 (Kimber 84m)
first charge was 43gr Varget
second was say 43.5gr Varget

at first I had them COAL at 71mm , or so, an put one in the rifle an closed the bolt, noticed the bullet hit the rifling I guess before the bolt moved down, so I ejected and Wound in the seater Die about 1 turn or so, ended up around 70mm .

shot them.

first something happened or just disliked. 1st was 3 inchs high an right.. 2 and 3 were neat together on the Left side about 4 inches away from the 1st. same elevation. ???

second slightly warmer, they shot half a diamond shape 1.5 inch group, 1 inch spread windage but 1.5 inch elevation difference..

the first shot felt a bit more effort to lift the bolt, slight smidge on the cattridge base, next two didn't show this... (Neck sizing only may just be due for fls?)

what would you do from here with the load..

Try a 44gr charge, or back it down to a 42-42.5gr load, keeping in mind Min is 43.5 - max 45gr.

im not one to hot rod a round but not really happy with 1.5 inch , do I seat the 120gr deeper into the case? shortenin COAL? an re try lower charges? or it may simply be it wants that wee bit more to tighten up as is..

keepin in mind- my other load developments have all been in the low charge weight as it appears a tight chamber. showin pressure signs after 1-2 grs..
WL

 

[Barnard308]

Do you have a proven load for this rifle or did you just start with 43g and went from there? how many times has the brass been fired? have you annealed it? Also if you have a sporter barrel on the rifle give it plenty of time to cool between shots. On my sporter barrelled rifles i give it 3-5 min to cool between shots but stay consistent with this. I would seat the bullets 5-10 thou off the lands and try again with loads (5 of each) start at 43.5, 44, 44.5, 45 or if you want some more trigger time do them in .2 gr increases starting at 43.3, 43.5,43.7 and so on up to max. watch for pressure signs and have fun.

 

[GreenBob]

This, plus I would do some dry firing before you shoot. Or bring a .22 to "warm up" your trigger finger.

Do you have a proven load for this rifle or did you just start with 43g and went from there? how many times has the brass been fired? have you annealed it? Also if you have a sporter barrel on the rifle give it plenty of time to cool between shots. On my sporter barrelled rifles i give it 3-5 min to cool between shots but stay consistent with this. I would seat the bullets 5-10 thou off the lands and try again with loads (5 of each) start at 43.5, 44, 44.5, 45 or if you want some more trigger time do them in .2 gr increases starting at 43.3, 43.5,43.7 and so on up to max. watch for pressure signs and have fun.

 

[Ron AKA]

You are not overloading with those charges of Varget, and your COAL seems to be about right for the cartridge. I like to base a seating depth trial on three groups of three shots. My suggestion would be to pick a charge weight and about 3 different seating depths and load up 9 rounds for each. That should give you a pretty good idea what seating depth works for you. Once you settle on a seating depth, you could try three different charge weights and see which is best. And of course you could do the charge weight trial first and the seating depth second. I think the main thing is to only vary one thing at a time, and shoot 9 rounds minimum of each to see how well it does.

 

[bigedp51]

Below some "expert" advice by Erik Cortina of Team Lapua USA

Long range load development at 100 yards.
Erik Cortina
Team Lapua-Brux Captain
http://forum.accurateshooter.com/threads/long-range-load-development-at-100-yards.3814361/

Some of you have asked for more detailed instructions on how I do this. Here they are:
1. Find Jam by seating a bullet long on a dummy piece of brass (no primer nor powder) and apply die wax to the bullet ogive and record it's base to ogive length.
2. Chamber the round and close the bolt.
3. Snap the bolt open and measure the base to ogive measurement. If it is shorter than previous measurement, this is your jam. Do it a few times with different cases to make sure.
4. Load a known powder/primer/bullet combination. I load 4 of each powder charge in 0.5 gr. increments and seat bullets at jam - .020". I use one shot of each to get barrel fouled up and also keep an eye for max pressure at the same time. You can also use these rounds to break in a barrel if you are inclined to. If I encounter pressure on the hotter rounds, I will not shoot groups with the other loaded rounds and will pull bullets when I get back home. Do not shoot in round robin style because position and natural point of aim will be compromised.
5. Shoot 3 shot groups starting from lowest to highest. All groups are shot over a chronograph.
6. Examine target and find the place where consecutive groups line up vertically and ES is the lowest and speed increases the least from one group to the next.
7. Load to the middle of the powder node and do a seating depth test.
8. Load 3 shot groups starting from Jam - 0.005" all the way out to Jam - .040" in .003" increments.
9. When you find the seating depth test that shoots the best, load towards the longest side of the node to allow more room for throat erosion.
10. Final step is to load the new seating depth and load 5 shot groups in 0.1 gr. increments 0.5 gr. on each side of node (if pressure limits are not reached). This will cover an entire grain of powder and you will be able to pinpoint where the powder node starts and ends. In the summer, load towards the low end of the node, and do the opposite in the winter.

P.S. I have heard if you keep your Australian rifle wet and muddy they shoot better.

 

[RonR]

Below some "expert" advice by Erik Cortina of Team Lapua USA

Long range load development at 100 yards.
Erik Cortina
Team Lapua-Brux Captain
http://forum.accurateshooter.com/threads/long-range-load-development-at-100-yards.3814361/

Some of you have asked for more detailed instructions on how I do this. Here they are:
1. Find Jam by seating a bullet long on a dummy piece of brass (no primer nor powder) and apply die wax to the bullet ogive and record it's base to ogive length.
2. Chamber the round and close the bolt.
3. Snap the bolt open and measure the base to ogive measurement. If it is shorter than previous measurement, this is your jam. Do it a few times with different cases to make sure.
4. Load a known powder/primer/bullet combination. I load 4 of each powder charge in 0.5 gr. increments and seat bullets at jam - .020". I use one shot of each to get barrel fouled up and also keep an eye for max pressure at the same time. You can also use these rounds to break in a barrel if you are inclined to. If I encounter pressure on the hotter rounds, I will not shoot groups with the other loaded rounds and will pull bullets when I get back home. Do not shoot in round robin style because position and natural point of aim will be compromised.
5. Shoot 3 shot groups starting from lowest to highest. All groups are shot over a chronograph.
6. Examine target and find the place where consecutive groups line up vertically and ES is the lowest and speed increases the least from one group to the next.
7. Load to the middle of the powder node and do a seating depth test.
8. Load 3 shot groups starting from Jam - 0.005" all the way out to Jam - .040" in .003" increments.
9. When you find the seating depth test that shoots the best, load towards the longest side of the node to allow more room for throat erosion.
10. Final step is to load the new seating depth and load 5 shot groups in 0.1 gr. increments 0.5 gr. on each side of node (if pressure limits are not reached). This will cover an entire grain of powder and you will be able to pinpoint where the powder node starts and ends. In the summer, load towards the low end of the node, and do the opposite in the winter.

Thanks for that. I haven't played with seating depth yet.

Regards
Ron