Which First: Powder Charer or Seating Depth?

[JASmith]

Which First: Powder and Weight or Seating Depth?

There is a discussion on the 65 Creedmoor forum about this (https://www.65creedmoor.com/index.php?topic=11714.0).

The jump-friendly nature of the 0.5 degree part of the SAAMI Grendel throat makes me wonder if the answer for us might be along these lines:

1. Choose a bullet
2. Choose the first powder
3. Establish near-max safe load
4. Ladder or other approach to get most accurate seat depth for this powder and bullet
5. Explore other powders with this depth to find most accurate
6. Tweak seating depth for that powder and charge weight

What is the Horde's experience along these lines?

A follow-up question is: Could the optimum depth established in the last step above then be used as the powder exploration depth for other bullets? If so, the first three steps.could be skipped and one goes directly to powder optimization, followed by a final seat depth tweak.

At the risk of going further down a possible yellow brick road, after establishing the generic bullet-independent starting seat depth, could one do the first powder pass for a new bulleet with the objective getting a safe near-max load, then select the most accurate powder,, use it for the charge weight tweak, and then single seating depth exercise using the chosen powder, bullet and charge weight combination?

[Klem]

JA,

Having read the thread on the other forum it seems most of them are Satterly fans. I think the word 'Satterly' is specious; at first glance it sounds impressive but it hides a load of rubbish.

Your steps are sound in my book. It's how I now approach Optimum Charge Weight.

I have a load development I am about to perform on the Nosler 100BT.
1. Choose bullet
2. Use QL to find the most efficient powder (max velocity at SAAMI).
3. Start 10% low and 1% apart so 10 increments. Slowest 5 increments; 2rds each (10rds). Fastest five increments; 8rds each (40rds).

• 50rds - This is a shooting session.
• Interested in finding best group closest to SAAMI (I am interested in the velocity curve but Satterly won't drive the work-up; results on a target will).
• LabRadar all rounds
• Over 10 increments for safety and to get the load/velocity curve
• Fastest 5 increments are fired at targets; 2*4rd groups each increment.
• Not interested in finding a load in the slowest 5 increments so minimum rds only to establish velocity.
• Mag length for auto loader, 0.02" jump for bolt gun. I only play with seating depth in a bolt gun and only for competition or shank grip.

If interested in another powder then that is another 50rd work-up to a different QL SAAMI limit. I don't think you can substitute powders into another powder's optimum charge.

I will post the data so we can see and discuss. With 8rds per increment at the top end that will be more than enough to check Satterly (velocity 'nodes') again.

I don't think playing with seating depth in an auto loader is worth it. The platform is not precise enough to realise any meaningful benefits, and let's face it, playing with seating depths doesn't do much unless you are shooting Bench Rest competition with heavy bolt guns. Plus, in an auto loader you can only push the bullet into the case, not stretch it out. That robs case space and space is velocity. It would have to be a quantum improvement in group size to justify robbing yourself of velocity in such a slow calibre. Quantum improvements don't happen when tinkering with OAL unless you are close to, or against the lands, so that pretty much nails that coffin. My concern with auto-loader OAL is more about whether it fits in a mag and whether it holds it firm enough to not get bashed about on loading.

[JASmith]

[Sinclair]

Wow, just when I thought that I had all this stuff figured out, you two come along and open another can of worms. Great stuff by the way.

I am beginning to long for the days when I was blissfully ignorant of OBT, OCW, and Satterly. I would start low, work up to what seemed to be max, back off a half to a full grain, and call it good enough. At this rate I will never find the time to find my rifle's "favorite load".

[Lemonaid]

Not advocating this but read/test and make up your own mind. https://precisionrifleblog.com/2020/...elopment-tips/
I will try their challenge in the future and see if it pans out.

[centerfire]

Scott discussed doing seating depth ladders before charge weights with Caylen Wojcik on Modern Day Sniper. I find many of Scott's processes backward. In this case, I often have to adjust charge weight during seating depth ladders because changing seating depth changes pressure to some degree. In other words, I end up doing both simultaneously after I've found the approximate charge weight I plan on using.

As far as 6.5 Grendel in an AR15 goes; there wasn't any room for a seating depth test so tested different combinations until I found one that was both accurate and had low ES/SD. I don't think you'll have much choice in most mag fed auto loaders.

[A5BLASTER]

I'm going to find the powder charge first, then seating depth second to tighten up the group as much as possible.

I do it this way in both my bolt grendel and ar grendel, starting my seating depth/ coal as long as it isn't in the lands and is mag feedable.

Even in my ar grendels playing my seating depth shorter once I have found my powder load has resulted in sub moa groups.

1000 ways to skin this cat.

[kmon]

Inline with A5

Pick bullet then powder for that bullet. Seating depth, start with the longest that will feed reliably in that rifle then check that that seating depth is not into the lands, seat deeper if it is.

I shot for groups and still will but I prefer to start off with a ladder and like to shoot it 3 times unless I can see it on the first timee, second and third verify if I think are needed. Watching the location and velocity of each load.

Find a load from the ladder and load there on either side and shoot for groups.

Really at that point I may or may not alter seating depth, depending on if I am happy with the result already or not.

On the Ladder shots color the bullet different colors and shoot white or light colored paper to see the differnt loads better in comparison.

Like I said I might work with seating deph or I might not, I have worked up several half or better MOA loads and never changed seating depth, others I have gotten MOA loads down to about half MOA with seating depth adjustments without changing the seating depth. If you change more than one variable at a time it makes it more difficult to know which was the right move charge or depth.

One thing is for sure I do not want a load that is too long to feed from a repeating firearm that has to be loaded single shot.

I am primarily a hunter then target shooter although I do fire a lot more bullets on targets than I do while hunting.

[grayfox]

In my experience and using my spreadsheet bullet-timing approach (an attempt to be purely mechanical in looking at bullet/barrel performances), I've been finding charge first for a given powder, then adjust seating depth. Agreed for an AR there's not much to work with but this approach is also working for my bolt guns, which do have more Coal room. Once I find the charge a seating depth change of 0.010-0.020 can make a big difference in group size.
In my spreadsheet that compares bullet travel time in-barrel, to exit MV and barrel length, a 0.1 gr adjustment in powder makes more of a change/impact on bullet timing than 0.010" coal adjustment. Now this is all theory but it does seem to play out in shooting, at least for me. The Coal adjust of 0.010" seems to be on the order of 1:10 compared to a charge delta of 0.1 grs.

I attribute the smaller change in timing from Coal adjust to -- theory, now -- it changes the timing of the bullet's exit while not appreciably changing the exit MV; this from the observation that for a given powder load, there is a certain fairly fixed amount of ke transfer to the bullet available, and the barrel's (friction, etc) characteristics being constant as well, then starting the bullet's travel at a slightly longer or shorter barrel length is only a slight amount of micro-sec difference in arrival at the muzzle......... so the longitudinal pressure-wave from powder burn, which travels at 18,900 ft/sec, shifts slightly towards or away from the muzzle tip in those few micro-sec.

I do think there are limits to my adaptation but for the barrels and chambers I'm shooting it does seem to work well.

Since a different powder might well have a different pressure curve, one coal for all powders wouldn't seem to be in the cards, to me.

[Popeye212]

Ditto what A5 said.

[FLshooter]

[Briano23]

Klem , please explain .
2. Use QL to find the most efficient powder (max velocity at SAAMI).
I am not familiar with QL.
Thanks
Briano

[Klem]

Brian,

QL is Quickload, an internal ballistics program used by hand loaders. There are several external ballistics programs available which calculate bullet drop after the bullet leaves the barrel however for those of us who reload we want to know what's happening inside the gun from ignition to bullet exit. This is called internal ballistics.

Quickload is a popular program which lets you enter pretty much all the parameters that we like to test; calibre, bullet, powder type, powder weight, case volume (different brass manufacturers), seating depth and barrel length. There are a couple of other parameters you can tinker with to make it more accurate.

Here's a screenshot of the dashboard. In this case this is the max weight of 8208 in a Lapua case, with a 100Nosler BT, at 2.283" COAL before the prediction reaches the maxmimum SAAMI recommended for Grendel. Note the red line on the graph, this is the pressure in the barrel as the bullet travels to exit. There is a peak at 2" and this is what we are concerned about, called "Peak Pressure". For auto loaders at the length of barrel where the gas port is is another predictive pressure which will tell you how reliable your cycling is going to be. Velocity is also predicted and this is the blue line in the graph. You enter your barrel length and it will predict a muzzle velocity. There is more to the program and I have never used all of its features.



Like all simulators it is not 100% accurate and contingent on the quality of input. The programmers are safety conscious so the predictions are conservative. This is good for AR15's as it's a relatively fragile rifle. I use this in conjunction with manufacturer tables and loads on this forum.

[Lemonaid]

Quickload is cool, but is it $152.95 worth of cool? I think I will try the weird free German language sim first. A good reason to learn a new language!

https://www.neconos.com/category/Software-2

[Bfglowkee]

Treat the expense like any other piece of reloading equipment you buy. When you do that, you will see its very cost effective and can save you money when it comes to trying powders that you might not be sure of in a cartridge. As Klem said, its conservative but useful on those days where you want to reload without making a mess