Seating Depth Frustration

[dgeesaman]

I know guys who compete at 1000y using Sierra Matchkings. But they also sort and tip their bullets. Some of them use a Bob Green dual-ogive comparator in their sorting process.

For shooting .308 out of a hunting gun, I suspect a cursory sort for weight, oal, and bto would eliminate any flyers. But 308 is not gilt-edge sensitive so to begin I’d shoot from the box. If the results of the tuning process are satisfactory, I would not bother to do any sorting.

 

[Mark611]

My rifle is not a hunting gun and yes I do trim and tip them!

 

[dgeesaman]

My rifle is not a hunting gun and yes I do trim and tip them!

The OP is a hunter. The context remains as a hunting gun.

 

[USAFRet]

All that work on seating depth and the best group he had was the 175 grain SMK with the recommended COL of 2.8. Haha. He had one flier out of a 5 inch group. Other 4 were touching. AR-10. It was really cool as this is the first time I have been able to do a full test with my reloads. His rifle did not like the 168 grains at all.

38 grains Benchmark. Norma brass. CCI 200 primer.

He handed me several hundred pieces if Norma brass when we met up. So, going to get to work. He was happy and that made me happy.

Thanks all. I learned a ton.

 

[Ruger15151]

Base to ogive variance is NOT the issue. The seating stem only pushes against the Ogive so if there is a variance in bullet BTO, it just means the base is pushed in a little more or less into the case.

Variance in seating depth can be caused by several things.
-work hardened case necks with different number of firings on them
-too much neck tension
-inconsistent neck tension
-lack of dwell time at the bottom of the stroke
-carbon in the neck
-compacted load where powder is pushing against base of bullet
-and several more.

I use the following process and get +/-.0005 valiance in seating depth

-anneal with every firing
-remove expander ball and use expander mandrel to set consistent neck tension
-Use same caliber hard nylon brush (Iosso works best) to brush carbon.
chuck it in a drill and spin in neck until you feel the neck just getting warm.
load same day you brush the necks and the bullets will load like butter and more consistent

 

[jm22250]

So, I am setting up some loads for a 308. I am starting with recommended COL of 2.8 and seating .003 back for 4 different loads for accuracy resting. So, objective is
2.8
2.797
2.794
2.791

However, I will get one cartridge measured and the next will be anywhere from .002 to .003 off. I took this that there might be a little tip deformation. So, I broke out the comparator to double check and I am also getting some cartridges with up to .003 difference. With a difference of up to .003 and me trying to seat a .003 difference, makes me wonder if I just wasted a bunch of time.

Am I doing something wrong? Bullets are 168 and 175 Match King. Non-tipped.

Here's another thing to consider. What press are you using? I bought a RCBS summit and have had problems with seating depth. Sometimes up to ten thous. I'm using a rcbs gold metal micrometer die. If I take that die and put in my old Rock Chucker press I may get 1 Thou variance. This way I know it's a problem with the press and is not die related.

 

[USAFRet]

Here's another thing to consider. What press are you using? I bought a RCBS summit and have had problems with seating depth. Sometimes up to ten thous. I'm using a rcbs gold metal micrometer die. If I take that die and put in my old Rock Chucker press I may get 1 Thou variance. This way I know it's a problem with the press and is not die related.

Rock Chucker Supreme

 

[gunsandgunsmithing]

Rock Chucker Supreme

Great presses but are most consistent when they can cam over. A lot of seating dies aren't conducive to that and if some has been taken off the bottom of a sizer or top of the shell holder, that's a place to look for inconsistency there.

 

[Mark611]

There are a lot of variables to consider, most folks who don't load on a level of what some of here do and do not understand why we load the way we do or the reasons why, IMO, whether it's a hunting gun or a competition gun most of the same principals apply, understanding now that the op is running a gas gun? AR10, gas guns can be very sensitive to load development if you want to get decent accuracy from them, I agree with Ruger15151, on his method, I do the same on all the action types I run, I wet tumble clean, anneal every firing, I also only use a body die that does not touch the neck in sizing the case body, followed by a mandrel collet neck sizing die, Then trim all the cases to the exact same trim length, chamfer and deburr, gas gun method, bolt guns I also turn my necks uniform flash holes {ECT}, that's just brass prep!!!! I'm not even going to get into case volume primer seating depth, IMO this all matters for consistent load development, YMMV

 

[USAFRet]

I used to shoot archery years ago. I would measure velocity. Adjust weight on the string. Measure arrows, broadheads, weight distribution, etc. To eek every last little thing I could for speed and accuracy. Practiced all the time and spent every waking minute thinking on what I could do to get my setup prefect. I was a competition shooter and a hunter. I was in my early 30s then. Funny part is my buddy would come out with his older bow and the same arrows he bought at BPS when he got it and shoot the same scores as me, often better.

Now I am in my mid-50s. Looking back, I spent a ton of time, effort and money to get just a little improvement. I don't need to go down that road.

I am not looking for laser accuracy. To tell you the truth, I just want some decent hunting loads with acceptable accuracy and want to make sure I am going about it the right way. To tell you the truth, I am looking for efficient and effective. Effective to me is consistent MOA groups at 100 yards and enough energy to take an animal down at a certain distance. With my eyesight, age, and the ailments I have, 300 yards in a vital zone is all I am looking for. Not perfection.

I thank everyone for their inputs. I don't want to get to measuring every little component, annealing, and all of that. Good enough is good. Again, looking to get an efficient way of getting good enough accuracy and speed.

I got the answer I needed here. Some bullets a just have tighter tolerances than others. Will that make a difference in what I am doing, maybe? From what my buddy did with the loads I put together, I am completely satisfied that he was happy with the results. So, the tolerance found was not that big of a deal.

Lesson learned, on seating depth I should open my gap to probably .015 difference, because the ,003 is probably for folks looking for a bit more perfection than I am.

 

[Mark611]

Agreed, if your happy that's all that matters.

 

[MikeRu]

Make sure your seater has enough leverage otherwise you get more variation due to differences in neck tension. A Lee seater gives very consistent seating depths as measured by base to ogive.

 

[Newhouse]

Another thing to check is if the primer is seated the same depth on all the cases.