seating depth vs powder charge

[Mark611]

A lot of you guys use the same methods I do, I'll use my 6.5 Creedmoor as an example, I have fired this rifle about 100x, in the past 5yrs mainly with hand loads, I have not found the sweet spot for this barrel yet, I do not have a lot of time to work on this rifle to tweak the loads, it's a 110 Savage Tactical 24'' HB, anyway, I have been running 41gn of RL16 with 147gn ELDM's these bullets run in the 2730fps range, velocities are good, seating depth isn't! I started at 10k off the touch and I'm now at -30k off the touch at this point, just now starting see the groups starting to tighten up, once I find the accuracy with the seating depth then I'll worry about the powder, but I may have to try a different bullet as well! if it won't shoot as good as I want it? I have a new Criterion pre fit to put on it!

 

[Steve Donlon]

I want to be able to open my bolt without pulling a bullet if it is necessary, such as a bad primer or some safety reason. I found @ .006" in, I can always do that. .006' won't stick a bullet into the lands with any rifle I have ever had to use in competition. I don't find it difficult to find nodes with my method. A tuner in the hands of an experienced user will keep one on the node, from what I have seen. I have never liked the idea of jumping bullets for some reason. I know it works the very best but I just have never been there.

Years ago, like 20, lets say, I used to test till all the cows came home. I found that EVERYTHING matters. .001" of seating depth matters as does .01gn of powder matters. Comes the question, particularly in todays world of cost of barrels, Smithing and components. How much is it worth to absolutely wring every possible iota out of a barrel? One can easily burn the "goody" out of a great barrel testing constantly. I find that a given load stays the same one barrel to the next with very minor differences. A simple ladder of powder charges in .02gn increments will nearly always yield a group in the small teens at my constant .006" in. The rest is in the windflags.

You are right. It's all about the chamber. When you find the bullet you like, make the chamber to fit that bullet and the guess work is over. I like the G.Salazar "06" chamber for 210 gr. SMK bullets.

 

[Cfshooter]

I’m a start with a bullet on the lands and run powder test first kinda guy. From there I’ll test seating depths.
That’s the way it was introduced to me by two world record holders, it may not be for everyone though.

I do about the same but start about .005 off (I have dumped powder on bench before lol).

 

[Bill Norris]

@Bill Norris sorry I didn’t see ya but I think it’s been covered a few times. Start with something known and reasonable for depth and then work up once the depth is found. I have never had someone come back and tell me they didn’t like this order better.

The only thing I’ve worked on in a long time that was “new” was the 6GT and I just started in the middle of book data for the depth test and it worked out great.

I guess if I had to have something off the books, I’d start at the longest point I’d load and shoot a one shot pressure test then do the depth first like normal.

Oh yea, not trying to argue at all. Just wanting to learn about this method.

 

[Clancy]

Oh yea, not trying to argue at all. Just wanting to learn about this method.

I didn’t take it that way, no worries.

Try depth first. I promise you’ll get a better load that’ll shoot in more conditions.

If you’re worried about “working up” to a warm charge to do the depth test, I generally use my 2 or 3 sight in shots and fouler for that.

Now, not for you or anyone in this thread necessarily but just because the internet is forever and someone brand new will read this …. What I mean is if 30 grains is a commonly used and book safe load in a 6mm-whatever, my first sight in shot might be at 27, second at 28, 3rd at 28.5, by then I’m going to clean it and shoot a fouler at 29 and start on my depth test with say 29.2. I’ll find the depth then load 29.2-30.6 in .2 jumps and if I hit pressure anywhere I just stop. Again, far beneath you Bill just want it on the record for someone reading this at 2 am 8 years from now.

 

[RabbitSlayer]

Wondering how you can do seating depth first without knowing where to start with the powder?

There is an eric cortina video on this but last time i looked i couldn't find it. He does a pressure test and backs off pressure far enough he won't run into pressure during the seating depth test. The depth changes case volume, so decreasing depth increases pressure. To me this makes sense, because a full case tends to make better ES\SD.

 

[Sixgun]

I heard that seating depth is more important to accuracy than the powder charge. Is there any truth to this ?

If you can use a tuner brake I highly recommend it. I just pick the velocity node on the upper end of my velocity range...pick a seating depth where the BT to bullet body is above the neck-shoulder junction and let the tuner do the rest. You'll probably even have multiple nodes before you run out of adjustment.

 

[GetReal]

In my experience, when I use Bartlein barrels and Beger bullets, I first find the powder charge that works for the harmonics of the barrel and then I adjust seating depth to get to about 0.375 c-t-c maybe as low as 0.25" . Ive done this with 6 different rifles.

That's good enough for me for an f.Class or a PRS style rifle

 

[Pete Wass]

You are right. It's all about the chamber. When you find the bullet you like, make the chamber to fit that bullet and the guess work is over. I like the G.Salazar "06" chamber for 210 gr. SMK bullets.

Chambers matter, for sure. A friend had a genuine Robinette 30 BR reamer made and it is a great one. 0 freebore so lends itself to short bullets. Don't need heavy bullets inside 300 yards. Why suffer? My opinions are strictly for 30 Cal stuff and more specifically the 30 BR.

I tried a 6 BR over the past three years and found it on again off again. I shot it with a tuner and without, not much difference. When it was on I felt it shot through the wind better than the 30 BR - when it was on. All the years I've been messing with tuners I really haven't learned to use them properly. Why is it a 30 BR generally stays in tune better than a 6 BR? What is it about the 6 MM bullet that causes so much trouble often?

 

[Steve Donlon]

Chambers matter, for sure. A friend had a genuine Robinette 30 BR reamer made and it is a great one. 0 freebore so lends itself to short bullets. Don't need heavy bullets inside 300 yards. Why suffer? My opinions are strictly for 30 Cal stuff and more specifically the 30 BR.

I tried a 6 BR over the past three years and found it on again off again. I shot it with a tuner and without, not much difference. When it was on I felt it shot through the wind better than the 30 BR - when it was on. All the years I've been messing with tuners I really haven't learned to use them properly. Why is it a 30 BR generally stays in tune better than a 6 BR? What is it about the 6 MM bullet that causes so much trouble often?

It seems the 30 cal bullet has a lot going for it. I know I really enjoy shooting my 300 BLK DDM4 Hunter with Sierra 125 gr MK bullets at 300 yards. What's not to like about one inch groups at 300 yards with a 300 BLK. It's no 30BR, but still a lot of fun. Easy to shoot, plenty of bullets to choose from and easy to reload with pistol powder. And the barrel will last a very long time!

 

[CharlieNC]

In Mr Boyer's book he details a matrix shooting 5 charge weights at 5 seating depths = 25 total combinations to find the optium for both factors from one trial. While this is effective, it is not efficient and is only necessary if the behavior is extremely complex; there are numerous test designs which are both effective and efficient.

I use a combination known as a central composite design which evaluates five levels for each in 9 combinations. The following was shot by a friend using three shots each (n=27 total shots) , and he elected to repeat this on two different days. The Vert and Hor POI are measured, their spreads, and group size. Yes the spreads and group size responses based on 3 shots are statistically significant, but I will not bore you with those details. The point is that it is more efficient and effective to optimize both charge weight and seating depth at the same time vs individually.

I have used several different test designs in this vein to find the optimum during a single trial. When something unusual is observed, a little fine tuning followup provides clarrificaton.

 

[chop house]

Following

 

[CharlieNC]

Just to be clear, does each red dot represent a round fired during load development ?

The dot is the average response of the three shots per trial.

 

[CharlieNC]

So each red dot represents 3 shots ?

Yes

 

[johnmyers]

I was fortunate to hear Ferris Pindell speak at local gun club meeting several years ago. He was in early stage of Alzheimer’s but still sharpest man in the room. He said seating depth was #1 in accuracy. That was good enough for me

 

[CharlieNC]

Not meaning to be critical but this seems an overly complicated method of load development with an excessive number of rounds to find a path forward especially if you repeat the test twice than add break in rounds.

If may seem complicated since I did not go into the details. But it is only 27 total shots, 9 different loads x shots each for which five parameters were measured for each of the nine groups.

 

[CharlieNC]

If may seem complicated since I did not go into the details. But it is only 27 total shots, 9 different loads x shots each for which five parameters were measured for each of the nine groups.

As a better answer, this is the 3-shot data. The chart plots all parameters vs all parameters to see the entire story.

 

[Clancy]

There is no need for charts, graphs, hundreds of rounds- none of it .

Shoot 5-8 depths and then 8-10 charges. Load the longest of the depth node, and the middle of the powder node. If your barrel speeds up, fine tune the powder a little.

It’s been a long time since I’ve had a rifle that wouldn’t shoot 1s and 2s consistently over a long period of time, and I spend all of about 50 rounds on load development including foulers.

Use good components, a good smith and practice good case prep. If you get those right, most everything falls into place.

 

[jackieschmidt]

Every Short Range Shooter, whether Group or Score, should watch Wayne’s interview with Eric at least 3 times.

 

[PhilC]

And if you really want to have fun, try making a cast bullet work in a rifle as well as the jacketed ones do! Lol, I fell down this rabbit hole 5 years ago! I’m also convinced all my guns shoot a lot better than I can and I’ll never win a bench rest competition because I’m way too inconsistent. I have some rifles that might do well but not with me pulling the trigger!

Whole different ball game but that's part of the fun in shooting cast.