Optimizing jump first vs. charge weight in load development.

[jlow]

Like most of you, I optimize my loads using the OCW method which involves optimizing the charge weight first, looking for a node where the average POI does not change significantly before adjusting seating depth to tighten the group.

Was reading the Berger manual today and read the following interesting comment “In general, the seating depth of a particular bullet in a particular rife tends to be more static than what powder charge will work best. In other words, it’s probably best to start with a low to medium powder charge and find the best seating depth. Then, using that established seating depth, starting working on changes in powder weight”

From a safety standpoint, I can see that the Berger method is slightly safer because if one ends up using the starting load in a jam, one could get into trouble but that still assumes that one does not start with a low enough charge. Does anyone use this “alternate” method and have any comment?

 

[seymour fish]

Start at 'hard jam', tune powder. Then find ideal depth without worrying about a pressure spike, until the bullet is Waaay down in the case. Then tune powder again. Just one way.

 

[ShootDots]

I use something similar. Most VLD's like to be seated into the lands about 10K. So if I am developing a load say, in my Dasher and I am planning on using a VLD, I START out at 12K in the lands for preliminary testing. Conversely, if I am going to be using a tangent ogive bullet, like a SMK, I will start out at 10K OFF the lands. Then I find something that appears to be doing well. Then I will fine tune the powder charge to get it as best as possible. Then I start a seating depth ladder test. I usually do that in 5K increments. Once I find out "pretty much" where it likes to be, I will continue the seating depth variations to 3K increments, one way or the other (in or out). Then if I am getting excellent groups but my E.S.'s are a bit high, I will start changing primers. Then I test again at 300 yards. If that works, I test "out yonder" either at 600 or 1000 yards. If I am getting vertical, I have found that a neck tension change might very well be in order. Generally speaking, I try and run about 1K to 1.5K of neck tension. This has worked for me for a good while now. There are a slew of various ways to tune your rifle, however, this is the method I use..

 

[Toolbreaker]

In my limited experience, I've found what they wrote to be a better method for me. I find that the seating depth of a bullet relative to the lands to have a more dramatic effect on a rifle's grouping abilities than charge weights alone. This observation may also be inherent to the VLD-style bullets design, also (guessing). What I won't say is that it saves me any time or components in the long run, as I still re-visit seating depths after a charge weight is found. I do usually find that the initial depth is very close to my final seating though, after settling on a depth in the middle of a window.

 

[skiutah02]

I'm close to ShootDots approach with the VLDs. I start with a modified version of Berger's suggestion when using their VLDs.

http://www.bergerbullets.com/vld-making-shoot/

I've modified it for me because I wish to have the boattail-bearing surface junction above the neck-shoulder junction for the vld I shoot (90vld). So only two seatings work for that criteria.

Thus I start with a moderate to mild load and shoot two groups of three each at 0.010 jam and 0.040 jump and see which seems better. Then powder charge ladder at the best seating depth as determined above, then back to seating depth in the middle of a node as determined by powder OCW. Then testing at 300 and 600 with neck tension and small increments of powder charge and seating. If not satisfied, I try primers, but most of the time since the charge/seating was optimized for a particular primer, I do not see gains from primers w/o starting mostly over. Almost forgot about the chronometer measurements (priceless). Not suggesting in any way that this is the best way, just how I have done it for the vlds of late.

If not a vld, I usually arbitrarily start at 0.020 off.

Important to always be willing to adapt...

 

[SS427]

When I first got into the accuracy game seven or so years ago, I always felt powder charge and seating depth had to be interdependent on each other. I just never had the time or patience to refine a load development strategy around the idea. So I tuned the powder charge then seating depth.

After reading Tony's book, it confirmed my original suspicion. I went back and developed loads for several of my rifles that I thought I had found the best load for. I end up with a different powder charge, different seating depth, and improved accuracy. I can't say with 100% confidence the new load development strategy is why the load was different...it could be I'm actually getting better at shooting. But I'm pretty darn sure it is the reason.

So I adjust both at the same time now as described in Tony's book. It works for short range anyway. And yes, I am a sheep...I don't have the time or money right now to reinvent the wheel.

 

[1shot]

When starting with a new cartridge, lot of bullets or a new barrel, I use the following procedure. I seat a bullet in an empty case and color it black with a sharpie. I remove the firing pin assembly so I'm only using the bolt body and close the bolt on the set-up round. I then measure the mark made on the bullet by the rifling viewing it through a large lighted dental magnifier. What I'm looking for is a perfectly square mark. As all barrels are different as well as the exact length of the free bore I use this dimension measured with a Sinclair hex nut at the ogive as my base line. If the mark isn't square I adjust as necessary until it is. I record that measurement as it gives me a reference if I change bullets and an indicator of throat wear throughout the life of the bbl.
I then start moving up in powder charges being mindful of pressure signs in .3gr. increments until I find myself in an accuracy node. Neck tension is usually the last thing I experiment with. Some cartridges like a lot, others can be soft seated so I try a keep an open mind in this area. On the subject of primers, I have found one cartridge that wouldn't perform well with Wolf/Tula primers and that was the 6.5x47L. I tried everything and it just wouldn't shoot. I switched to CCI 450's and it shot knots. I don't know why, but it taught me a lesson to always keep and open mind when starting from scratch. I've learned a lot from this thread, I hope this helped someone,
Lloyd

 

[jlow]

The thing I am actually looking for here is reason why one method might be better than the other.

I can see that for VLD, since they don’t like jumping, starting at jam is a good idea to get a good idea of what the pressure spike is with a light load.

ShootDots - For tangent ogive, my question is it seems like you start at 10k do seating depth, tune charge, and then seating depth again with ladder. That seems like one extra step compared to OCW?

Toolbreaker – yea, I will be working mostly with a tagent ogive bullet.

Domoran – I think both powder charge weight and seating depth affect barrel time, so in terms of potential problem of starting on a “scatter node”, it is likely that both methods will do so but it would appear that either adjustment might be able to allow you to center on an accuracy node?

One potential advantage of the OCW method is it appears that optimal seating depth for most bullets is known and so although the exact depth still needs to be define, it is relatively easy to start somewhere close to optimal? True or false?

Lots of good and new ideas! Thanks!

 

[ShootDots]

Jlow, I have been at this "precision" reloading game for A L-O-N-G time. I have shot pretty much everything out there to one degree or another. I do not know how the OCW or other systems work. I am sure they are very well thought out and tried and true systems. The reason I do what I do, more steps or not, is that it has worked for me for years.. Are there less tenuous methods, better methods out there>>> I have no doubt. All I did is tell you what works.. MOST, certainly not all, VLD (secant ogive) bullets like to be jammed, so I start there. It has been my experience that MOST, certainly not all, B/T (tangent ogive) bullets prefer to be seated somewhere off the lands, so I start there. It is merely some place to start. From there, the field is way open. You have to start somewhere, so I start there.

 

[artbosco]

I've always found that finding the best barrel, bullet, powder, primer, and brass combination first, and then fine tuning with neck tension and seating depth makes taking cloverleaf-groups to one-hole groups much easier.

 

[sparky123321]

Similar to above for me. Best barrel, bullet, powder(mid level charge), primer, and brass combination first. Lapua brass is my first choice if available. I always test 4 or more bullet and 3 or more powder combinations. Normally, there's a clear winner at this point. Then I fine tune powder charge, neck tension and OAL.

 

[jlow]

ShootDots – Sorry, did not mean to be critical, just asking questions to learn. Regardless, thanks for the useful info.

 

[ShootDots]

I never thought your response was critical at all... I just expounded so you would know where I was coming from.. No offense taken whatsoever.. I apologize if I sounded like I was offended.. T-Rust me, it takes a whale of a lot for me to even get my feathers ruffled so think nothing of it..

 

[Joe Salt]

jlow I have a question, what makes you think VLD's don't like to be jumped? If you look at the Burger website it will tell you to jump if you are not getting good results with jam. I've done it for years to get rid of vertical at 1000 yards, you may not see it at close range.

Joe Salt

 

[jlow]

Yes gstaylorg, I actually did read that. I guess what I meant is they were originally designed to be jammed and my guess is that is how most people use them? But you are right in terms of the fact that they appears to also jump well. I don't use them and frankly was more interested in the tangent ogive bullets...

 

[mikecr]

Charge weight testing is generally a much coarser tuning approach as opposed to seating depth, which is for fine tuning. If you're paying close attention to your velocity data during charge weight testing, rather than group size, seating depth shouldn't matter all that much.

I've consistently seen just opposite with smaller hunting capacity cartridges.
Worst seating is bigger than worst charge.
I agree with Berger.

 

[Catfur]

Berger 105 VLDs in my 6mm Rem (hunting rifle) take a .1 jump (not .01, but .100).

 

[jlow]

Perhaps there is something to this idea that seating depth adjustment is finer tune than charge weight? The reason I say this is because at least in OCW, the fine tuning is done with seating depth?

The other thing that I find interesting is the original Berger comment in my OP, the part that says “the seating depth of a particular bullet in a particular rife tends to be more static than what powder charge will work best” That would appear to mean that once you optimize charge weight and seating depth, changes in charge weigh say to compensate for temperature change will not require a seating depth change? Might be wishful thinking but it would be nice if it was true?

 

[mikecr]

I believe it's logical to get within best seating range(within ~10thou of best) before moving to powder. This, because seating testing is way more coarse to results than powder testing.
I believe determining best seating means actually testing for this(full blown), and Berger's testing works better than just pulling something from your butt..

It's logical to test at reduced loads(well lower than intended), not just for safety, but to get away from optimum charge so that you can more purely see best seating range.
While you can do full seating testing from an optimum powder node, big seating changes will collapse the powder node, which will mask seating adjustment results.
I do it during fireforming of new brass for a new chamber.

With best seating range determined & set you can then move to powder any way you do, and then with best powder and best seating range, tweak seating finely within 5thou either way to shape grouping.
Any more than this, at this point, and you're officially chasing your tail.
It does also make sense to tweak seating to compensate for some detriment in a powder node, but this is not 'seating testing' and it should not be taken to mean that seating testing is a fine adjustment. That is never the case.

Once I lock in & log best CBTO, I never have to mess with it again for that bullet, or for the life of that barrel. If that's what Berger meant by 'static', I agree there as well.

 

[AlanPF]

....Once I lock in & log best CBTO, I never have to mess with it again for that bullet, or for the life of that barrel...

Mike,

Are you saying you don't chase the lands?

Alan