Load Development

mthuntr

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Got it…. See this is something I was never taught or seemed to pick up while reading my reloading manuals (read 3 separate manuals now).

I have always wondered how to get close to that 100% case capacity, bullet seat depth and not over compressing the powder charge.

I would like to experiment with powders/ bullet/ primer combos in my 300 Win Mag and my 6.5 Creedmoor. And save the 760 powder for the couple of nostalgia rifles I have. But as you mentioned, with the scarcity of components, I guess I am tied to what I have. But I do plan on keeping my eye out for available powders.


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It's a bummer too about availability because I saw a Facebook post from Powder Valley stating they had more variety of powder at that moment than they had for the previous 2 years. Nearly everything was out of stock when I saw the post. If you're willing to take a dive into Discord there is a group that will alert you to in stock items (it can be oppressive and you have to be fast). There's a thread with instructions here on Rokslide.
 

madcalfe

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id probably go up the the 180-200gr bullets with 300wm
leave the 150's for the .308 crowd lol
180gr h4350 will work well 190-200gr H4831, h100V H1000 will work
my vote would be to find some 180gr nosler accubonds and start stock piling.
 

harvey_nw

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Short, fat cases with short barrels will be more efficient with a certain powder than the same case with a different barrel, or than the same power in a long skinny cased cartridge.
Yep. Commonly referred to as powder column.

I have always wondered how to get close to that 100% case capacity, bullet seat depth and not over compressing the powder charge.
Ideally you can look at published load data and find a combo that lists a compressed max charge and assume that you'll be loading longer than SAAMI spec, so you can usually tune that to where you're maximizing the potential and staying near full without being compressed.
 

EdP

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From one engineer to another, go with the ProChrono or other similar set-up, not something barrel mounted. You will want to correlate your group statistical data (extreme spread and standard deviation) with group size. You can't do that with a chronograph that has affected barrel harmonics, the correlation isn't valid.

Get the Hornady Bullet comparator tool, a shoulder bushing set, and a quality caliper that reads to 0.001. Use them to set your dies for optimum shoulder bump and bullet seating depth. I prefer to determine the seating depth that a particular bullet/rifle likes with a moderate load, then try to find an optimal powder charge by working up towards a max load in .5 grain increments. I typically start seating .005/.010/.015/.020 off the lands with bullets like an Accubond or Gameking (tangent ogive bullets, not secant), shooting groups of 5. Pick the best and work your powder load from there. Other bullets like secant ogive and monometal bullets often like more jump. Some other folks work the powder charge first, but moving a bullet out towards the lands decreases pressure and so velocity drops, changing the previous test result.
 

harvey_nw

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moving a bullet out towards the lands decreases pressure and so velocity drops, changing the previous test result.
Umm.. opposite. Decreasing the distance to the lands increases pressure, because you're lessening the alleviation space for pressure to escape. That's why a starting load is suggested when jamming the lands to fireform.
 

EdP

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Your post is almost word for word the same as one I made recently on another forum, only to be shown that it is not correct! Moving the bullet out towards the lands increases space in the cartridge decreasing pressure, UNTIL the lands are contacted. It is contact with the lands that then causes pressure to jump. Using a BC tool and starting .005 off the lands (as the longest OAL) should prevent land contact and the pressure jump. Here is the link to an article by Brian Litz, Berger's ballistics engineer, describing the relationship between bullet seating depth and pressure: Link

Regardless of whether you agree with the Litz article or believe the opposite to be true, either theory says pressure changes with a change in seating depth. If pressure changes then velocity changes and I believe that is reason enough to select a seating depth before working up an optimal powder charge.
 

harvey_nw

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Here is the link to an article by Brian Litz, Berger's ballistics engineer, describing the relationship between bullet seating depth and pressure: Link
I'm well aware of the article and the science behind it, but in my own personal experience if you're testing or tuning powder charges and seating depth within an identified velocity node it's not absolutely going to work like that. You can change the seating depth .050" and the velocity change can be negligible, if even noticeable. And I've also seen pressure signs show up at .020" off, that weren't there at .050" off. My point was in regards to safety, telling someone asking about load development that "moving the bullet out towards the lands decreases pressure" as a broad statement without specifying the potential affect, is bad info.
 

EdP

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My point was in regards to safety, telling someone asking about load development that "moving the bullet out towards the lands decreases pressure" as a broad statement without specifying the potential affect, is bad info.

I agree, but I don't feel like I did that, specifically because I pointed to using a comparator tool to locate the lands and starting at .005 off and moving outward (seating deeper in the case). If that advice is taken and loading is done so that the lands are not in contact when the cartridge is chambered, the result of seating deeper in the case would be increased pressure per the Litz article. I could have been more clear by noting the effect of loading with land contact.

Your statement
Decreasing the distance to the lands increases pressure, because you're lessening the alleviation space for pressure to escape. That's why a starting load is suggested when jamming the lands to fireform.
contradicts the Litz article on two fronts. First, the free volume increase in the case that results from seating the bullet closer to the lands Litz says decreases pressure up to the point at which the bullet contacts the lands. Second, Litz attributes the pressure spike from loading in contact with the lands to resistance due to the engraving force, not an "alleviation space" effect. Do you have a reference that provides an alternate explanation to those in the Litz article?
 

harvey_nw

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I don't feel like I did that, specifically because I pointed to using a comparator tool to locate the lands and starting at .005 off and moving outward (seating deeper in the case). If that advice is taken and loading is done so that the lands are not in contact when the cartridge is chambered, the result of seating deeper in the case would be increased pressure per the Litz article.
As engineers say, it works on paper. In the real world I have found what I'm explaining to be true. A powder charge that shows no signs of excessive pressure at .050" off the lands can have indications show up at .020" or .010" off.

First, the free volume increase in the case that results from seating the bullet closer to the lands Litz says decreases pressure up to the point at which the bullet contacts the lands.
Ok my question is are we talking case pressure, or chamber pressure? Because I could care less what kind of case pressure there is, the peak chamber pressure after ignition is what's important. I think people overthink this concept. Let me pose my favorite question, if lessening the volume of a case by seating depth increases pressure, why are there so many published compressed loads? Wouldn't that be EXTREMELY dangerous to be publishing info that could have a radical affect? No. Because even a compressed load at spec length with a ton of jump doesn't have the same peak pressure as a load with the same amount of powder that's jammed into the lands. Using that theory one could assume that grabbing a max charge or even higher and loading it way longer than SAAMI spec out to .020" off the lands is safe because it should have lower pressure.. Negative.

Second, Litz attributes the pressure spike from loading in contact with the lands to resistance due to the engraving force, not an "alleviation space" effect. Do you have a reference that provides an alternate explanation to those in the Litz article?
You answered yourself in the question, jump (alleviation) allows pressure to escape before the bullet makes contact with the lands and the engraving force is initiated. I don't have a reference off hand, but I have seen an article in the past and I will try to find it again.

If you have a link to data where they measured peak chamber pressure in relation to case density or seating depths with the same powder charge proving this concept I'd love to look at the numbers.
 

EdP

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Because even a compressed load at spec length with a ton of jump doesn't have the same peak pressure as a load with the same amount of powder that's jammed into the lands.
Of course not. As Litz explained, one effect dominates until the bullet is loaded out to where it contacts the lands, then another effect dominates. It's not apples and apples. Litz is pretty clear when he says "Seating a bullet against the lands causes pressures to be elevated noticeably higher than if the bullet were seated just a few thousandths of an inch off the lands."

You answered yourself in the question.
I don't think so. The only question I asked is "Do you have a reference that provides an alternate explanation to those in the Litz article?"


In the interest of real world comparison to the theoretical, I went back and reviewed some of my load development data for different rifles in various calibers. I found that, in some rifles, velocity (the direct result of chamber pressure) tracked exactly as Litz predicts, and velocity was higher for the more deeply seated bullets with the same powder charge. In other rifles there was no correlation and velocity was essentially unchanged over the same range of seating depths (.005" to .020" off).
 
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RockinRam96

RockinRam96

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This is good discussion on seating depths. Interesting the two points of view. I will have to read the article by Litz to better understand his point of view.

On another note, what is the “heaviest” bullet to look at for 300 Win Mag? The local Sportsman’s Warehouse has a ton of 220 grain Nosler Partition. Thinking about picking up a box or two.


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brn2hnt

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This is good discussion on seating depths. Interesting the two points of view. I will have to read the article by Litz to better understand his point of view.

On another note, what is the “heaviest” bullet to look at for 300 Win Mag? The local Sportsman’s Warehouse has a ton of 220 grain Nosler Partition. Thinking about picking up a box or two.


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I shoot 215 bergers out of a 26” barrel, didn’t see any pressure signs till a full .6gr more powder and am getting 3050.

Based on that I’d feel ok running 230’s in my gun before the energy gains are likely too small for the velocity tradeoff.

Big thing to keep in mind is your twist rate. Is it fast enough to run those longer bullets? Might be easier to start there and work backwards.


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RockinRam96

RockinRam96

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Big thing to keep in mind is your twist rate. Is it fast enough to run those longer bullets? Might be easier to start there and work backwards.
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I guess that should have been my question. I believe the twist rate for my rifles barrel is 1:10 (haven’t put hands on the rifle yet). How does one understand twist rate and bullet weight.

I understand the basics, heavier slender bullets need a faster twist rate. But where do you start to find issues?


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madcalfe

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I guess that should have been my question. I believe the twist rate for my rifles barrel is 1:10 (haven’t put hands on the rifle yet). How does one understand twist rate and bullet weight.

I understand the basics, heavier slender bullets need a faster twist rate. But where do you start to find issues?


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you can google barrel twist rate calculators. berger has one a well same with carbon6
 

brn2hnt

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I guess that should have been my question. I believe the twist rate for my rifles barrel is 1:10 (haven’t put hands on the rifle yet). How does one understand twist rate and bullet weight.

I understand the basics, heavier slender bullets need a faster twist rate. But where do you start to find issues?


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Bullet weight is a little misleading. It’s more bullet length, so a 220 partition might be ok while a 210 Vld might not.

The stability calculators will be your friend. Looking for a stability above whatever they say is good. Bullet length, bearing surface, elevation, temp, all play a role.

I don’t trust published twist rates. I have a tikka that should be a 9.5 but with the cleaning rod verification it’s a 10. Means a 162 eldx should have been fine but it’s actually not, but a 168 berger classic Hunter is ok.

Lots of variables to play with, but long story short, I would want a verified twist rate before sinking tons of capital into bullets on the edge of stability.


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RockinRam96

RockinRam96

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I don’t trust published twist rates. I have a tikka that should be a 9.5 but with the cleaning rod verification it’s a 10. Means a 162 eldx should have been fine but it’s actually not, but a 168 berger classic Hunter is ok.

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Even the twist rate stamped on the barrel can’t be followed?

Can you explain a way to measure with a cleaning rod?


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brn2hnt

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Even the twist rate stamped on the barrel can’t be followed?

Can you explain a way to measure with a cleaning rod?


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Maybe by certain Mfg, but the one stamped on my tikka is wrong. Not only did the cleaning rod test give a longer result, but the bullets that the calc said would be too long based on the cleaning rod measurement showed wildly erratic flight past 500 yds.

Take a cleaning rod with a free spinning handle. Attach whatever fitting you have that gives the tightest fit in the barrel. Shove it a little ways in the barrel. Make 2 marks on the rod indicating the depth of the rod and the 12:00 position. Run the rod in until it reaches 12:00 again, then mark the depth again. Remove and measure the distance between the marks, and you’ll have the inches per 1 full revolution. (12:00-12:00)


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RockinRam96

RockinRam96

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Maybe by certain Mfg, but the one stamped on my tikka is wrong. Not only did the cleaning rod test give a longer result, but the bullets that the calc said would be too long based on the cleaning rod measurement showed wildly erratic flight past 500 yds.

Take a cleaning rod with a free spinning handle. Attach whatever fitting you have that gives the tightest fit in the barrel. Shove it a little ways in the barrel. Make 2 marks on the rod indicating the depth of the rod and the 12:00 position. Run the rod in until it reaches 12:00 again, then mark the depth again. Remove and measure the distance between the marks, and you’ll have the inches per 1 full revolution. (12:00-12:00)


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Makes perfect sense. I’ll try it out. Thanks.


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Travis Bertrand

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A more accurate way of cleaning rod test is to insert rod without a tip on it. , make a mark at 12 or 6 location by verifying with light down bore. Run the rod back and make another mark. Then measure. You are looking down bore for where to mark. Does that make sense? Put the tip of the rod on the front of a groove at 6:00 closest to muzzle. Run rod back until it touches the same groove at 6:00. Mark.

Often times when someone does the previous method, it is incorrect because there’s slippage with the rod and the grooves because you are pushing or pulling something and it isn’t tight enough of a fit. If that makes sense. You will almost always come out long on your twist rate.


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RockinRam96

RockinRam96

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Started to run some loads tonight. Got a few cases prepped and primed. Started at the low end of the powder recommendation at 58.0 grains. There is still A LOT of case space left. Is this normal?

Loading 200 grain ELD-Xs.


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