Load Development -- Seating Depth First?

[joelkdouglas]

I acquired a Berger reloading manual, despite never having shot any Berger bullets. Some interesting articles in there.

On page 147 in an article by Bryan Litz, chief ballistician at Berger, talks about seating depth during load development: "In general, the seating depth of a particular bullet in a particular rifle 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 estabilished seating depth, start working on changes in powder charge."

An interesting idea--just never occurred to me to start with seating depth changes before powder adjustment.

A small counterpoint from German Salazar here: "A good place to begin (and frankly to stay unless you're already at the Master level in NRA Highpower) is to jump 0.020" for conventional tangent ogive type bullets such as the Sierra MatchKing line or Berger's new designs and to jam 0.015" for VLD type bullets such as Berger VLD, Hornady AMAX, JLK VLD, and others of the secant ogive design."

Salazar reference below:
http://riflemansjournal.blogspot.com/20 ... depth.html

Just wonder what you guys thought about seating depth and load development. After all, it's February!

 

[Dr. Vette]

If you're thinking Bergers specifically then I'd reference you to this article:

http://www.longrangehunting.com/forums/ ... fle-40204/

Does Litz mention in the book his preferred method of looking for the best seating depth for conventional bullets?

 

[joelkdouglas]

Probably no Bergers for me. They are great bullets, no doubt, but I find Accubonds/Partitions my preference for hunting and either Custom Comps or Match Kings my preference for practice. The articles are still interesting, as is the load data.

That same article (from your link) appears on page 100 of their manual for the seating depth progression. Multiple authors wrote articles for the Berger manual, similar to the Nosler manual having multiple guest writers.

Litz does not mention a seating depth progression for tangent ogive bullets, though he does mention that tangent ogive bullets are less influenced by seating depth. I would guess a similar seating depth progression would work for tangent ogive bullets also (AccuBond, Partition, etc.).

Dr. Mike mentioned once he does a seating depth progression, but I think it was after the powder charge progression. Litz's method is intriguing as he indicates the seating depth preferred by a rifle shouldn't change. The load developer could then work with compare multiple powders as necessary.

 

[Dr. Vette]

That's interesting that he mentions that seating depth should not change. I tried everything I could to make Bergers and Nosler Accubonds work in my Dad's Weatherby but they would not, even at similar seating depths. With a 150 Barnes TTSX it shoots exceptionally well.

I would not have expected enough variation in the AB and the TTSX seating depth to make any difference, i.e. if his theory is true then the AB should have worked just fine too.

Of course, now I'm going to have to go and try it out. :grin:

 

[300WSM]

This really is a moot point.

Powder or O.A.L. Either one you can mess with and the other probably will still have to be messed with. Doing one over the other equates to nothing.

Think about this.

Drop a medium charge in...and start playing with the OAL until the accuracy is acceptable. Oh wait...maybe you aren't enjoying the velocity..so now you are going to play with the charge. The moment you do this the OAL may not react the same as it did with the lighter charge.

On the flip side...if you start working with the different charges until you hit the velocity mark you so desire...then you can play with the O.A.L. to tighten the group up.

There is no RIGHT answer here...but I've always worked on the velocity/pressure charge first, then the OAL. As a start I always seat the bullets .010 below SAMMI Maximum specs. Often times with the Nosler B/T's the accuracy is under one inch right from the start with this generalized O.A.L

I also do this because when I load ammo for many different people with many different calibers, rfles, etc...this O.A.L. is as safe as its gonna get. Most bullets don't mind a little jump into the BBL. Naturally there is always that one rifle that wants to be ignorant about stuff and things can't be simple. Those rifles are the exception..not the rule.

 

[SJB358]

I have always loaded for speed pressure first, while being slightly off the rifling or magazine depth. Then once I have found a most accurate charge with something I'm happy with I did little tweaks on seating. Now, I think I'll do the same, but make more drastic seating changes such as .010, .040, .070 and .100 off the rifling. Seems like its faster and minimizes seating depths to a node. Which will work better with a little bullet variance.

 

[RiverRider]

I think the idea is worth pursuing, if for no other reason than just to put the hearsay to bed. Nothing like first hand experience.

 

[Elkman]

That's interesting that he mentions that seating depth should not change. I tried everything I could to make Bergers and Nosler Accubonds work in my Dad's Weatherby but they would not, even at similar seating depths. With a 150 Barnes TTSX it shoots exceptionally well.

My STW likes the Barnes 160 TSX the best, by at least a 1/4 of an inch. The Nosler 175 PT is the next best and thats what I hunt with. It will be back with a new barrel soon, so I will get to do more load development.

I am working on load development right now for a new rifle. I do it this way, I take what I consider is a very accurate combination of bullet, powder and case. I then start a couple of grains below max and load 3 rounds, then up it 1/2 and 3 more, then usually one more time. I then seat my preferred bullet "as long as it will function in the magazine". Because after 50 years of reloading, the majority of the rifles I have tested prefer that. Some of course do like a longer jump but thats the way I do it. If that length does not work I step down 10 at a time. If my goals are not met (sub MOA) then I change powders and try again.

 

[onesonek]

I have always loaded for speed pressure first, while being slightly off the rifling or magazine depth. Then once I have found a most accurate charge with something I'm happy with I did little tweaks on seating. Now, I think I'll do the same, but make more drastic seating changes such as .010, .040, .070 and .100 off the rifling. Seems like its faster and minimizes seating depths to a node. Which will work better with a little bullet variance.

Same here, and would agree. See how it goes anyhow, when I start load work with the ABLR.

 

[Oldtrader3]

That's interesting that he mentions that seating depth should not change. I tried everything I could to make Bergers and Nosler Accubonds work in my Dad's Weatherby but they would not, even at similar seating depths. With a 150 Barnes TTSX it shoots exceptionally well.

I would not have expected enough variation in the AB and the TTSX seating depth to make any difference, i.e. if his theory is true then the AB should have worked just fine too.

Of course, now I'm going to have to go and try it out. :grin:

The AB will not shoot well in the .340 that you bought from me either. At least I could not get the same accuracy as I got with either 225 gr or 250 gr PT's. That was with the 250 AB's.

 

[FOTIS]

I load for acceptable velocity within acceptable pressure. Once I get that I go for accuracy.

Call me crazy but I will not use a 300 rum with a 180 gr bullet at 2900 fps even if it shoots in the .1's.

 

[barthowes]

I load for acceptable velocity within acceptable pressure. Once I get that I go for accuracy.

Call me crazy but I will not use a 300 rum with a 180 gr bullet at 2900 fps even if it shoots in the .1's.

+1 on this.. I always start by varying the charge to find what i like in speed and accuracy first. If the top couple charge weights don't give me the best accuracy, i will possibly use the better of the two as long as they are < 1 MOA. Then vary seating to dial it in

 

[Guy Miner]

A couple of years ago I took advantage of a handloading class (even though I started handloading about 50 years ago as a child) offered by Doug Arnold. Doug used to produce high quality, very accurate, rifles here in the Pacific Northwest, via his company Arnold Arms, and came up with several of his own cartridges.

I was a little surprised when in the class, he recommended determining the seating depth first, then messing with the powder charge. I guess it surprised me, because I'd almost always done it the other way around, unless I needed a specific overall cartridge length for proper feeding, such as with a lever action rifle.

It got me thinking a bit about which might be more important and has led me to at least do more work determining the proper seating depth.

FWIW, Guy

 

[Oldtrader3]

I am just thinking about what Doug Arnold's approach to reloading means? I can't say that it is right or wrong? I always have arroached loads with the standard COAL and the usual work up of powder loads to so maximum. Then I start looking at seating depth charges to optimise further. I can' say Guy, which is right or wrong. I guess that I need to think about this some more as I have been using my system for over 50 years and it works!

 

[Guy Miner]

OT3, I don't think there really is a right or wrong - and also most of my loading the past 20 years has been with the .308 Win for a short action Remington. For that rifle I simply load to mag length, 2.8" and call it good. The cartridges fit into the magazine and cycle flawlessly through the action, so I don't mess with the seating depth at all.

I do have the chambers of my barrels reamed to just accept factory loaded Federal .308 Win Gold Medal 168 gr ammo.

Long since discovered the charge of Varget that works well, so I don't mess with that either. Not a lot of experimenting going on for me with the .308 Win!
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With my .375 H&H Ruger Number One, there is no magazine to bother with, so I've been able to seat the bullets well out, to get them near the rifling. Long throat in that rifle. The cartridges look sort of silly with the bullet cannelure way out there, above the case mouth, but they shoot great.
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I did mess with the .300 WSM and .25-06 seating depths quite a bit, and was rewarded with good results in the .25-06, and at least with one .300 WSM load.

Don't think there's a right or wrong, but it was interesting that such a successful rifleman as Doug Arnold advocated paying a lot of attention to getting the seating depth correct, then worrying about the powder charge.

Interesting stuff!

Regards, Guy

 

[Oldtrader3]

Guy, I do work the lengths of a couple of cartridges because of action length. My .257 Roberts is in a full length Mauser FN action instead of a medium and I run seating long (3.93) an use the long thoat and chamber to gain powder space and expand my loads a little. It works, I get about 100 fps more than the the standard .257 because of creating more powder space and long COL 2.93, instead of 2.83.

Of course the .340 Weatherby is another cartridge that lends itself by design to the art of stretching length to see what you can get away with. The .340 is little more scary though because of the large powder charge belies the fact that when it does hit maximum, it does it fast!

 

[tjen]

Realy don't see the sence in the articles point.

If you start with as long of OCL as you can. And many things can limit that. Then as you work up charges to an acceptibly max pressure, you also can see what velocity is best for accuracy in that rifle. Choose any load (powder charge) that best fits your desire, accuracy, velocity, or a blend of both. Then you can safely shorten the OCL in steps of that load too see if you can ring out better accuracy.

Simiple and fast,

I load the 35rem for my leveraction 336 and the OCL is fixed due to the need to crimp on the cannelure. And that only allows change in powder charges to tune a load to the rifle.

 

[big rifle man]

Guy, On monday I took my .300WSM Kimber Montana to the range to try out some new loads I had been tinkering with. I had some newly annealed cases and wanted to try the Sierra 180 grain boattail. I normally use the prohunter bullet which has a flat base as opposed to the gameking. The first five rounds were loaded with 67.5 grains of IMR4831 with a Fed 215M and an OAL of 2.850. Cases were Norma. The first five rounds at 200 yards came in at a muzzle velocity of 3030 and a 2 3/4 inch group. I then tried the second batch of five which consisted of 64 grains of RE17 all other components the same. What a surprise. Muzzle velocity was just under 3100FPS and the group was 1 1/2 inches. The 64 grains is 2 grains under max and although I'm extremely happy with what turned up, so much so that it will be my Elk load for this fall I'm curious as to what 66 grains would bring in regards to velocity/accuracy. All in all a rather informative afternoon.

 

[atmoshpere]

I was curious how much seating depth affected velocity/pressure in my 284 and so I loaded up 4 different COLs (5 rounds each) with everything else the same and ran them all through the chrony. I'll have to go through my notes, but the avg. velocity difference between the longest and the shortest was not insignificant (thinking it was somewhere around 50fps).

That being said, I can see one advantage to setting seating depth first and then developing charge weight. If you are one of those guys that likes to flirt with the top end on most of your loads and you go out and find your max load and decide you want to shoot it and now are going to play with seating depth, YOU MAY HAVE TO CHANGE YOUR CHARGE AS WELL to avoid pressure spikes, depending on where your COL was to start with and where you want to go with it. So you're changing 2 variables now when you're trying to tighten up groups.

Also, with many powder/case/bullet combos you may run into case capacity limits before pressure limits. If you start your load development with a COL that is as long as possible, and then find that that bullet wants to be deeper in the case you may be crunchin' your chosen powder charge pretty heavily, which can lead to seating depth inconsistencies, and the need to change an additional variable again while you're trying to finalize load development.

Still not saying there's a right way or wrong way, but I can see advantages to both given certain situations.

 

[woods]

On page 147 in an article by Bryan Litz, chief ballistician at Berger, talks about seating depth during load development: "In general, the seating depth of a particular bullet in a particular rifle 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 estabilished seating depth, start working on changes in powder charge."

IMO he is not saying the seating depth will always be the same he is just saying that it will effect group size less than varying the powder charge.

For me I like to find a velocity I am expecting and am comfortable with no pressure signs and then do a seating depth test.

To find the velocity with the least work and components used you can't beat the Audette ladder which uses ONE load at each powder charge going up. Each of these loads I will shoot at .20" off the lands.

For instance recently I wanted to try a new bullet in my 6.5 rem mag (130 gr SSII) using RL17. With no data I wanted to start low at 48.3 gr and loaded one round at .3 gr increments up to 55 gr. That is 23 different powder weights but only one shot each. Then settled on the powder weight of 54.5 gr at a respectable velocity.

To do a seating depth test I load 4 or 5 shot groups at .015", .030", .045", .060", .075" & .090". The best group, best standard deviation and best extreme spread was at .060" off

Notice how velocity decreases with increased seating depth.

Perhaps it is a matter of fine tuning the exact millisecond of the bullet exit from the muzzle or the best combination of bullet jump/powder combustion/case expansion et al in the chamber who knows but IMO finding the lowest SD and ES will make that load more consistant through several loadings

But I suppose the question would be: If I did a seating depth test at 50.0 gr, would it have shown the best seating depth to be .060"? And if it had shown .045", wouldn't I have had to do another seating depth test to find the .060" seating depth at the 54.5 gr powder charge?

Nuff said, sorry to ramble