Load Density.

[Rtheurer]

I would like to get some input from some of the other top shooters in the nation about what you think is optimal, marginal and unacceptable for load density in your respective Match Rifle cartridges.
I got to thinking about this today that the two cartridges that I shoot in National and international compitions that hold the BEST elevation are the 308 and 6BR. Just so happens both are loaded to 98% and 102% load density. While I have and do shoot other cartridges at 1000 and 600 yards these two are by far holding better elevation for me than the others.

I used to think that 80% was the minimal ammount I would accept, 95 to 100% Optimal and anything below 80% I would just pass up.

Intrested in your experience with load Density and how it holds elevation at 1000 and 600 yards.
RussT

 

[Immike]

I have found the same to be true, that a full case has the advantage of not shifting the load around in the case. I read a article in PS MAGAZINE of a man that chronographed a pistol straight up, straight down and level with 3 different speeds. So there is definitely something there to look into.

 

[wapiti25]

I chronographed an M1 with military ball ammo in a test, barrel up then barrel down. It made a huge difference in velocity. The load was about 51 grs of the mil 4895 powder. I think keeping the powder close to the flash hole is the first requirement and a full case is a close second.

 

[BoydAllen]

A friend, who builds his own rifles, built a .204, that shot very well, but had ESs in the +50 FPS range, with the most accurate powder, TAC, and 32 grain bullets. The powder was down in the shoulder. He shortened the chamber so that he can make cases from .223 brass, and his ESs went to single digit. The Powder is now slightly compressed. While it was very accurate before, he says that a test group, with the new, shortened chamber was literally in one hole. I believe that he shortened the .204 chamber by .080. He still gets velocities over 4,000 FPS. The same barrel was used for both chambers. He just set it back a little.

 

[Rtheurer]

Thanks fellas that is what I was looking for. Donovan, Now that I have spent the better part of a weekend researching this, my older thought of 80% fill might be on the extreme bottom of what I might accept now. 95% might be the better option. At least for Long Range when all things are so important and attention to detail is the order of the day.
A Pdog rifle shooting 300 to 400 yards I could care less what the load density is, A Palma Match in South Africa or Australia however is another animal all together.

I too cringe at the compressed loads, most of the time my ammo runs .002 neck tension and will tolerate a compressed load of 105% fill real easy. Any thing over that and I feel I need to wait until the match day to final seat the bullet to its OAL. This is one reason I dont shoot 47gr of Varget in my Palma rifle like some of the other guys do. ( dont try this at home kids) If I happen to get a slow lot of Powder Ill trade it off or delegate it to another rifle rather than compress a powder charge that tight.

Something to be said for a Slower burn rate powder with a bulk density above 95%.

RussT

 

[357Mag]

RTH -

Howdy !

Yeh.... I'm with you.

My 6mm wildcat groups best with a case chuck-full of I2828 ( not compressed ), or RL-22 and case nearly full ( 6mm bullets of 88 -105gr ).

Have read that load densities in the 91 - 95% range work best, but that has not been my experience ( .224" cal and 6mm wildcats ).

On non-full cases like my .357AutoMag in a 22" barrel, even it grouped best after filling remainder of case air space above the powder
columne w/ " PUFFLON "


With regards,
357Mag

 

[Webster]

After the bullet leaves the barrel it doesn't know what the load density was. It's the characteristics of the bullet and muzzle velocity.

 

[Nomad47]

And what do you think affects velocity, Webster?

 

[Rtheurer]

MR Webster

Indeed that is called External Balistics while we are discussing Internal balistics. And it does matter. Im not sure about you, but I am trying to win a National Championship with my ammo. Not trying to be a jack wagon just stating that load desity may be part of consistant Velocity spread.. ie ES and SD which is very important for us 1000 yard shooters.

I was hoping Steve and Wayne would chime in with there thoughts.

RT

 

[Webster]

Copied from the original message:
I got to thinking about this today that the two cartridges that I shoot in National and international compitions that hold the BEST elevation are the 308 and 6BR. Just so happens both are loaded to 98% and 102% load density. While I have and do shoot other cartridges at 1000 and 600 yards these two are by far holding better elevation for me than the others.

Did you read the original message? He was talking about drop at 600 & 1000 yrds. related to fill density. Higher fill density does not necessarily mean higher velocity. Every powder has it's own characteristics. Getting a little bit more powder in the case does not mean another powder with less fill will give a lower velocity.

From Bergers Manual
308 Winchester 168 gr Match bullet

Ramshot TAC 83% 2707 fps
AA2230 90% 2627 fps
WIN 748 93% 2744 fps
RE15 100% 2738 fps
VIHT N550 104% 2698 fps

 

[Webster]

Sorry if I misunderstood something about fill density related to how much elevation you need on your scope.

 

[Rtheurer]

No worries.

 

[Webster]

I just entered the data from the Berger Manual for the 308 168 gr match bullet. 21 powders. I made four column's, powder, max charge, density & fps. Then I sorted the data by max weight, % fill & max fps. It took about 20 minutes to put the data together. I need to quite quoting Berger data, it's copyrighted. I will not enter my spreadsheet data for that reason. The data usually follows a pattern of density to fps and max wt. to fps but there are many exceptions. The most obvious are ball powders. I didn't enter burn rates.

 

[BoydAllen]

The way that I interpreted the question was not so much about velocity but vertical spread in long range groups, which directly relates to consistency of velocity within a group. I took holding elevation to mean consistency of elevation, and I think that the other posters read it that way as well.

 

[Rtheurer]

Boyd is correct. The question has nothing to do with the amount of elevationneeded to target. But group size or what us long range shooters call holding elevation, because wind is the Horizontal variable ( read DEVIL) that gets us all. So if I say for instance my rifle held 1/2 MOA elevation today at 1000yards that means it was a 5" tall group but may be wide in a switching wind.

Since Im shooting 20 to 30 rounds in a string of shots, if all of them hold good elevation then I know that I have a good load. Hence my question about having a powder that fills the case to 90+% keeping the velocity Extreme spread and Standard Deveation (ES SD) to the abslute min. Large Velocity spread = Large groups at long range.
Consistancy is the order of the day I believe.

Or maybe I have been wrong this whole time???
% fill ratio to FPS, I really dont care and it really isnt what I was asking about.

RussT

 

[wapiti25]

Yes, Boyd is correct. The spread that precision shooters (long range hunters and long range target shooters) are looking for is very small velocity changes. High velocity shoots high and low velocity shoots low, this can make the bullet go over the animal or above the 10 (X) ring or below just from the velocity change from the ammo as loaded. This extreme spread (ES) for velocity is something we can control or test for. This may not be the fastest velocity that the rifle can shoot just the most consistent.

 

[Steve Blair]

My best loads for ES are above 95%. In both my .284 Shehane and .300 WSM, the loads are compressed ~2-3%. I work on three factors for accuracy and low ES and they are mutually interactive. They are: ignition consistency which results in consistent barrel time, matching barrel time to OBT node and matching the load to barrel harmonics. It's not always easy to cause the three to coincide but that is where I find best performance. QuickLOAD and an accurate chronograph will get you close to the OBT node, the chrono will show the velocity spread and targets the grouping. Best results come from powders on the fast side for the cartridge, sometimes sacrificing a little velocity. Primers on the mild side for easily ignited powders like Russian or CCI. As I work up a load, I look for "flat spots" in the pressure series. That often occurs at or just below full pressure. The usual effect is that a range of .3-.5 grains will result in a small velocity increase and little change in grouping or ES. This is the same point that those using a ladder test are seeking. It's not the only way but this has worked for me.

 

[Webster]

Point well taken. He mentioned ES but the way I took it was if it had low fill density he had to give more clicks elevation.

 

[Laurie]

I'd look for that 95 to ~103% ratio, and that using a 5-6-inch long Forster powder funnel. I get nervous with too heavy compression, probably for no good reason as it's never produced any bad results that I've seen in examples such as loading .223 Rem with 69gn SMKs at magazine length over powders like N140 when you feel and hear the 'crunch' as powder kernels are crushed.

I have had the occasional good result over the years though with much lower densities, almost always using a powder that's faster burning than normal for the cartridge and bullet weight. I'd not categorise these as long-range loads though as they'd normally be down on velocity.

I think though there is much more to it than simply fill-ratio. I've seen strings where the ES went from desperate to amazingly good and back again as charges rose in fairly small steps. I always wonder in such cases if a re-run would repeat the results or not. Other times, a primer / powder / bullet / bullet-jump combination will give exceptionally small ES values in almost every charge weight maybe covering a full 2.0gn spread.

The other thing that makes me wonder about what drives this issue is 6.5-284 Norma, a cartridge with a slightly over-large capacity case when working on the 95% or more rule. Do a QuickLOAD propellant table run for the cartridge with the 142gn SMK at CIP COAL of 3.228-inch and you get a lot of commonly used powders that are in the 90-95% range, for instance:

Re19 - 94%
H4831sc - 95.4%
Re17 - 82.5%
IMR-4831 - 93.5%
H4350 - 91.7%
IMR-4350 - 90.0%
Lovex SO70 (what used to be AA-4350 pre-Western Powder) - 89.2%

(That's with the request set at max F/R = 105% and PMax = 59,000 psi.)

Viht N160, N560, N165; Alliant Re22/25; IMR-7828/7828ssc are all higher in the 95-100% range, but I find it interesting the popular and I presume effective 4350s are in the low 90s, this in a cartridge that gets a mention in dispatches on another ongoing topic in the forum about holding remarkably small elevations at 1K.

A friend decided that 6.5-284 was too large a capacity case for this single reason and that the optimum was 6.5X55AI, or in his case a wildcatted 6.5-284 that had the shoulders pushed well back to reduce the capacity. He did it - I presume ran a standard reamer in a bit short - and it simply didn't work, poorer results than the standard version. Another 'failed good idea' as he put it. Likewise, the several people I know who've tried 6.5X55AI have not found it a poor performer by any means, but nearly all say they couldn't see any benefit over 6.5-284.

 

[Rtheurer]

Funny you should mention the 6.5X284 as that is what I had on my mind when Iwrote the first thread. I have been shooting this round for quite some time. I think its been since 2003 or so. Using H4831SC every time in th elast three barrels as I know what to expect and can find a good shooting load right away... thats kinda important with this cartridge. When I load it i tap the case a lil on th eside of the gun to make sure the powder is at the bootom the case by the primer. Never put it bullet down in my carridge box either....
Does this voodoo really matter? I dont know, but it makes me feel better thinking im getting a more consistant repeatable ignition and burn each time. So the 308 and 6BR are holding better elevation for me than the 6.5 ever did but its "good enough to win with"
Like you, I have been playing with Quick Load and wanting to test some powders that fill the case a little better than H4831SC. One that keeps comming to mind is N160 and N165 do to its lower BTU/KJ rating and higher fill ratio. But alas i have been gone too much and not able to test said products or theory.

Im hoping the new Pressure Trace System will allow me to better evaluate and pick a powder that will perform as needed sooner, while collecting Data for later use. Should be intresting eihter way.

Attached is a picture of one of the 1000 yard shoot offs at the Nationals. Nothing wrong with the 308 holding inside the Xring. For that i really like the cartridge. It just flat holds Elevation.