"Loads close to the max pressure are more accurate"


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willypete
June 15, 2012, 09:30 PM
I ain't buying it. Completely aside from empirical evidence derived from my own reloading experiences, think on this:

.44 Special and .44 Magnum are way, way far apart on the pressure spectrum. So are .38 Special and .357. .460 Rowland and .45 ACP and .45 GAP are also good examples. Then there's .45 Colt in SAAs and .45 Colt in Rugers. And yet some people would have you believe that a 35,000 psi load will magically be more accurate than a 30,000 psi load, whereas a 17,000 psi load will be more accurate than a 12,000 psi load in two cases that are nearly or exactly the same. This also applies to rifle cartridges. You're gonna tell me that a 50,000 CUP load and a 28,000 CUP load are magically going to be more accurate than a 40,000 CUP load and a 20,000 CUP load, respectively? Out of the same gun? Think .45-70. Ever more near and dear to a lot of people's hearts is the .223 Remington, or 5.56x45, whichever flavor your prefer. Some NATO chambers have higher pressure limits than some other chamber designs. Does that mean that you can toss out your old reloading data, and you better work up new stuff at the higher pressure limit? Hmmmmm...

I read about this all the time. So-and-so asks for reloading advice and sumdood says "reload close to 65,000 whooblydammits in .31 Aussie Mag, but use 47 kilobadgerfarts in your .37 Weems and Plath. Since you're loading to max pressure, you're loads will be more accurate!"

Yeah, not buying it. I think accuracy comes from a good shooter who uses consistent practices in both his shooting and reloading techniques and is firing a well-made gun. I might believe that loading to full case volume could help a bit, but pressure? Not so much.

Another thing to think on: some manufacturer loads are made to less-than-maximum pressure. They don't want to blow up your guns any more than you do. And yet some manufacturer loads are very accurate in certain guns. We've all heard "shoot what your gun likes" especially in rimfire guns. I'm willing to bet not every .22 rimfire case out there is loaded to 24,000 psi, yet some display startling accuracy while others group like thrown gravel.

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Claude Clay
June 15, 2012, 09:33 PM
i do not know who wrote what you are not buying but im with you.

lost of things that are written are not correct. its up to us to decide
what is true as we know it.

EchoM70
June 15, 2012, 09:42 PM
Generally in my experience loads that are 1 grain under max always seem to be the most accurate for me.

willypete
June 15, 2012, 10:04 PM
EchoM70, I've got a few loads in .30-06 (just an example) that are more accurate 1 grain above max and a few that are more accurate 2-5 grains below max. Also, some of those loads are more or less accurate in different rifles. It depends on which powder, bullet, case, and primer I'm using. Are you sticking to one type of powder, case, primer, bullet, gun, etc? Does your one grain under experience apply to rifle loads, handgun, shotgun?

EchoM70
June 15, 2012, 10:21 PM
I've only loaded for rifles so far. I always use Winchester brass, CCI primers (LR&M), and Hornady Accubond bullets. In my .270, 300 win mag & 300 wsm I use H4831SC and IMR 4064 for my brothers .308... The .270 with 130 grain, 300 wsm and .308 with 155 grain and 300 win mag with 180 grain. all exhibit the best accuracy with 1 grain below Max published data.

EDIT: My mistake, the 155 grains are A-MAX, not Accubonds. The others are though.

Deus Machina
June 15, 2012, 10:34 PM
I always figured that a gun is made for a cartridge at a given pressure, which is usually a certain range under the the maximum rated. Thus, a load around that pressure--which will be near maximum even if just at a technicality (90% is 'near maximum' after all)--will usually be more accurate.

Hardly universal, but given the speed and force, it's safe to assume that a load will be most accurate in a certain range toward the upper end of accepted pressure.

Not that they won't be just as accurate lower, but your mouse-fart loads are going to be more affected by other factors by the time they reach the range you'd be using near-max loads at.

T Bran
June 15, 2012, 10:48 PM
Many of my most accurate loads are closer to the start weight than the max. Some are better near max but also have a sweet spot lower in the range. What will really surprise most folks is the reduced loads with H4895 are sometimes more consistant than anything above the standard starting weights. I have one load in my 300 Win using 110 grain Speer SP's and a charge weight approximately 25% below max of H4895 that will shoot one ragged hole day in and day out.
So I'm with you max isnt the optimal load in most cases though it may be in some instances every gun and load is different.
I have had a good deal of luck using powders that fill the case as much as possible while staying below published data. Slightly compressed loads do seem to be among the best in my experience and often I choose a powder for a new load by looking for one that is over 100% of case volume at max since most likely I wont reach max anyway.
T

27hand
June 15, 2012, 10:52 PM
I got tighter groups by downloading my 150 gr Nosler Ballistic tips by 1 1/2 gr.(from 59 down to 57.5) using IMR 4350.

B!ngo
June 16, 2012, 12:36 AM
I don't know if it is true, but to me it makes sense if it proves to be true:
1. Increased pressure yields more more speed and likely a higher rate of stabilizing rotation;
2. The increased pressure and speed yield a shorter travel time to minimize the bullet being affected by wind and other forces;
3. Higher speed equals a flatter arc that means less complicating bullet drop estimation
But again, I don't have any proof.
B

Kachok
June 16, 2012, 02:17 AM
My 6.5x55 and 30-06 are both most accurate 1-2gr under max. I shot my Sweed today with 129s it shot 1 1/2" with max 47.5gr of RL19 but it shot one hole with 45.5gr.

blarby
June 16, 2012, 05:31 AM
Generally, yes.

As weapons being the fickle dames they are...generalizations do not always apply.

You must consider however, that some loads offered and used can be as low as 50-60% of maximum rated pressure...which can have quite the negative impact on "accuracy" if you are used to certain groupings in a certain place at a certain yardage.

Generally speaking Loads within the top 10% of the pressure range are more consistent, and perform more in line with a given weapons engineered operating parameters. The key here is the parameters.

To offer a horrible car analogy:

Do well maintained Ferrari's drive well at 4-10mph ? No, same with Porsche- the suspension is too stiff, and the suspension tuning isn't geared and torqued for this "no stress" movement. 4-10 mph? heck, even 50-70mph isn't what it is designed for, and the parts work better in the operational parameters they were designed for.
It is however, utterly fantastic at 160mph though.

Does a 93 Saturn Sc1 with 250k miles on it corner well at 115mph ? No...it most certainly does not. It didn't do it particularly well when it was new, for that matter. It was designed to operate at normal , low-end road speeds. Its age and mileage only make the matters worse. Operating it outside of its operating parameters produces poor results to the point where it can be dangerous to some operators.

Hope that helps, just a little.

jmr40
June 16, 2012, 07:46 AM
I've found that I get better accuracy pretty close to max loads. Somewhere around +/- 1 grain either over or under the max listed load. But you have to watch the chronograph numbers. With some powders, and chamberings I've hit overpressure loads well below the max listed charges.

I've found that a load that completely fills the case and is slightly compressed works best. This way the powder ignition is more consistent than a load where the powder is loose and can move around in the case.

scythefwd
June 16, 2012, 07:59 AM
The one rifle I found the sweet spot for so far is using 41.7 gr of H4895... max is 43.5. Still getting horizontal drift.. but that is a shooter problem. No real vertical drift... .5 outside to outside or so vertically... 2" horizontal.. I think I've got a flinch.

JMR.. 1 grain, or .1 grain??

beatledog7
June 16, 2012, 08:16 AM
There are simply too many variables involved (cartridge, powder selection, bullet depth, mouth tension, etc.) to be able to make any over-arching accuracy generalizations such as this.

That said, I believe the two variable most affecting 95% of accuracy situations are and always has been the consistency of the cartridges (no matter what they are, they are as close to identical as possible) and the shooter herself.

ranger335v
June 16, 2012, 09:21 AM
"Loads close to the max pressure are more accurate" ----- I ain't buying it.

You are correct if you're refering to the old addage to load down for best accuracy. However, if you mean it's helpful to have charges near the pressure range the powder was designed for then 'close to max pressure' is correct, any powder's burn rate is much more consistant at the right pressures but they tend to be a bit erratic above and below that pressure; inconsistant powder burn does not help accuracy.

A LOT of us will change powder if we can't obtain sufficent accuracy at the velocity we seek; I will NOT settle for .30-30 velocity out of my .30-06 nor for .222 velocity out of my .22-250 just to obtain best accuracy, and it's seldom necessary anyway.

I've never found accurate handguns to be very quirky about velocity. If the gun shoots, it shoots; if it won't shoot, tweaking the charge doesn't make a lot of difference in the handguns I've loaded for. I rarely load handgun ammo hot tho, that batters the gun while providing no tangible benefit.

USSR
June 16, 2012, 12:54 PM
Totally depends upon the individual firearm. There is no hard-and-fast rule about where you will find the most accuracy, that's why we do load development.

Don

Walkalong
June 16, 2012, 01:07 PM
Exactly.

Not to mention that with rifles there will be more than one "sweet spot" along the way if you start low enough. Provably handguns as well, but I haven't proved it. I know you can find a sweet spot on both ends of the power spectrum with pistols.

Ky Larry
June 16, 2012, 01:47 PM
If one load was the best performing load for all guns, why do the reloading manuals list a starting load and a maximum load? I've read about and tried so called "ice cream loads." They are pure bull. I have 2 .223 rifles; an old Ruger 77V twotone and a new CZ-527 Varmint. The Ruger likes 22.5gr of AA-2460 and a 50gr Hornady S.P. The CZ likes 25.0 gr of AA-2460 and a 50gr Hornady S.P. Same bullet, powder, case, primer, and C.O.L.
After 37 years of reloading, I've learned that there is no shortcut to load developement. Every rifle is a study in ballistics unto itself. YMMV, but I doubt it.

ljnowell
June 16, 2012, 02:02 PM
I think that whoever said that was making a broad generalization. It depends more specifically on the load however. What powder, what cartridge, what bullet weight. I will say though, that almost all of my 45acp loads with AA#2 are most accurate just under max. My 45 colt Blackhawk is most accurate in standard pressure loads toward the top and in ruger only loads its most accurate pushing hte top. I have 38 special loads that are way at the bottom that are crazy accurate though. So it really all just depends.

1858
June 16, 2012, 02:30 PM
EVs are generally reduced when loading to higher pressures for any given cartridge. Does a correlation exist between EV and accuracy/precision ... that's the real question. Personally, I always get the best results at max loads and preferably compressed loads.

Many rifles are built well enough to withstand considerably more than 65,000 psi, some greater than 100,000 psi, but the limitation is the brass case.

Kachok
June 16, 2012, 02:38 PM
While there are no set in stone keys to developing loads there are little hints that help, certain bullets like the TSX like to be kissing the lands of the rifling while other bullets like to be a few 1/1000ths off the lands like the Berger VLDs. Some cartrages just like certain powders regardless of the rifle in question. I have yet to meet the 25-06 loader that had bad luck with RL22 or a 30-06 loader that got nothing but bad groups out of H4350, they just fit the cartrage in so many ways.

gunfighter48
June 16, 2012, 02:41 PM
During the 10 years that I was reloading, I found that most of the time the most accurate loads were around 10% less than max load. It depends a lot on powder and bullet combos. I was reloading 5.56, 45ACP, and 45LC.

jcwit
June 16, 2012, 03:14 PM
Rimfire .22 precision target ammo to the best of my knowledge not high speed ammo.

Target precision air rifles and pistols also are set at a slower FPS velocity.

Should tell us something.

kcshooter
June 16, 2012, 08:01 PM
MORE of my rifles have more consistent and more precise accuracy with loads at or near max.

It's not a rule, it's a ratio.

Trent
June 17, 2012, 11:42 AM
Faster powder, lower velocity has been more accurate in my experience. The more consistently your powder burn is as the bullet travels down the barrel, the tighter your velocity will be, the tighter your groups will be. Velocity directly affects everything else after the bullet leaves the muzzle - drop, wind drift, spin drift, rate of deceleration due to drag, EVERYTHING.

Accuracy begins and ends with consistent velocity. Period.

Shoot the powder / bullet that gives you the most consistent exit velocity and you'll find you most consistent grouping, every time.

MachIVshooter
June 17, 2012, 11:48 AM
I always figured that a gun is made for a cartridge at a given pressure, which is usually a certain range under the the maximum rated. Thus, a load around that pressure--which will be near maximum even if just at a technicality (90% is 'near maximum' after all)--will usually be more accurate.

Pretty much this. Though every gun is different, most tend to perform better with the bullet and operating pressure/velocity they were designed around.

Simply put, it is a "window of efficiency", something that is not unique to firearms. Machines work best when operated within their design parameters, and performance often degrades when they're run below or pushed beyond those parameters. Think of under or over loading cartridges in the same way you would lugging or overrevving an engine.

willypete
June 17, 2012, 04:54 PM
Engines=/=firearms. Yes, they're both machines with moving parts that handle varying pressures, but so is a dishwasher. You gonna tell me that a Kenmore is the same as a Winchester?

The "load to near max pressure" statement is a farce. There are accurate loads achievable at much lower than max pressure (ever loaded a smokeless cartridge with blackpowder?) for many different cartridges. The existence of actions capable of handling pressures higher than those the cartridge was originally designed for is a perfect example of the irrationality of the idea of loading around max pressure. Weatherby actions, Ruger #1, Ruger revolvers, modern actions containing older cartridges (think .257 Roberts in an action that is also available in .270 winchester, it's a difference of roughly 7,000 psi!) all provide examples of such actions. And yet, there are also examples of accurate loads available across all sorts of pressure ranges!

Some powders do have pressures at which they like to operate, but that's not what my original post was about. For a given powder that has a pressure spec it likes to hang around (H110, IMR7828), I'm sure I can think of one or more that will operate at a wide range of pressures (BP substitutes, BP, W231, H335).

1858
June 17, 2012, 05:09 PM
The "load to near max pressure" statement is a farce.

Why do you think that the Savage F-T/R rifle has a 30" barrel? Why do PALMA shooters and many F-Class or Benchrest shooters use 30" or longer barrels? The answer is VELOCITY which requires PRESSURE. I've never met a PALMA or F-Class shooter, or Service Rifle shooter for that matter, who downloads to achieve better accuracy.

Clark
June 17, 2012, 05:15 PM
Deus Machina

I always figured that a gun is made for a cartridge at a given pressure, which is usually a certain range under the the maximum rated. Thus, a load around that pressure--which will be near maximum even if just at a technicality (90% is 'near maximum' after all)--will usually be more accurate.

I am 61 now, but my father was designing guns 60 hours a week when I was 5 years old. He took me with him on Saturday. He was chief engineer with a big office, but we would go out in the dirty shop and deal with guys in greasy overalls.

I figured that all that red stuff on the ground was blood, from shooting people with the guns.

Now that I am older, I suspect it was hydraulic fluid.

He also showed me how to calculate stress in a gun as a function of chamber pressure.

But when I try to blow up guns, they never blow up at the calculated pressure. Guns are much harder to blow up than the math suggests.

I am beginning to suspect that the stress strain curve for metals is measured in static conditions, and the millisecond or two that firing a gun stresses the metal is a dynamic condition for which I have no formal data.
I do have some seat of the pants feel for it. It is ~~20 % ~~ 40% more than I calculate.

USSR
June 17, 2012, 09:04 PM
Accuracy begins and ends with consistent velocity. Period.

Shoot the powder / bullet that gives you the most consistent exit velocity and you'll find you most consistent grouping, every time.

Nope. I used to believe that when I was young and inexperienced. But then, extensive load development work with a chronograph opened up my eyes. I was shocked when I saw that the loads with the lowest ES and SD numbers were not the most accurate loads. Now I simply use the chronograph to establish what the average velocity is for a particular load that is accurate out of my rifle.

Don

willypete
June 17, 2012, 09:32 PM
Why do you think that the Savage F-T/R rifle has a 30" barrel? Why do PALMA shooters and many F-Class or Benchrest shooters use 30" or longer barrels? The answer is VELOCITY which requires PRESSURE. I've never met a PALMA or F-Class shooter, or Service Rifle shooter for that matter, who downloads to achieve better accuracy.

You don't seem to understand my premise. The most accurate loads in a given chambering are not necessarily those loads which run at or around max pressure. Heavy, long barrels in competitions requiring open sights and off-hand or free standing shooting positions are typically chosen because they help the shooter attain a longer sight radius (which contributes to accuracy) and mitigates outside influences which could cause the shooter to come off target (also contributing to accuracy). The longer barrel also boosts velocity, which is very helpful given the ranges at which some of those matches are conducted. Heavier guns tend to be easier to shoot accurately when a human is involved in the equation. They also mitigate recoil when shooting from a bench. My original post had nothing to do with barrel length; it is about the idea that loads around the maximum pressure for each cartridge are arbitrarily more accurate than loads not around the maximum pressure for each cartridge.

Regarding match shooting, I have some loads for .30-06 that I shoot in service rifle that I download by approximately 35% (pressure by manufacturer data; the actual charge is about 12% below max weight) because they are more accurate than loads running at max pressure. Load development varies with gun/cartridge/component variations, but the max pressure is a safety guideline, not an accuracy guideline.

The fact that there are some very accurate loads which are nowhere near maximum pressure for a given cartridge runs contrary to the falsehood that cartridges must be loaded to their maximum pressure to achieve a semblance of accuracy.

Nope. I used to believe that when I was young and inexperienced. But then, extensive load development work with a chronograph opened up my eyes. I was shocked when I saw that the loads with the lowest ES and SD numbers were not the most accurate loads. Now I simply use the chronograph to establish what the average velocity is for a particular load that is accurate out of my rifle.

Don

I was very surprised when I learned this as well. While the internal ballistics may be very uniform, the external ballistics depend on other additional factors. Isn't shooting stuff fun? :D

1858
June 17, 2012, 10:43 PM
Nope. I used to believe that when I was young and inexperienced. But then, extensive load development work with a chronograph opened up my eyes. I was shocked when I saw that the loads with the lowest ES and SD numbers were not the most accurate loads.


Given the variables in components, particularly bullets, it's possible to shoot a smaller group with higher EVs and SDs but there's no question that given a large enough sample under controlled conditions, there's a correlation between EV and accuracy/precision.

MachIVshooter
June 18, 2012, 01:54 AM
Engines=/=firearms. Yes, they're both machines with moving parts that handle varying pressures, but so is a dishwasher. You gonna tell me that a Kenmore is the same as a Winchester?

Of course firearms aren't internal combustion engines. But analogies aren't about using the same nouns, are they? :neener:

The use of dissimilar things to draw parallells and make points is not inherently flawed. You just have to make the right comparisons and word it correctly.

There are accurate loads achievable at much lower than max pressure (ever loaded a smokeless cartridge with blackpowder?) for many different cartridges.

Of course there are, if the twist rate and velocity are still appropriate for the bullet.

I have found that best accuracy is acheived pretty close to factory loads in most rifles. Light-for caliber bullets at screaming velocities often have erratic performance, and heavy-for caliber bullets spinning too slowly don't shoot well. Try firing a 110 gr. spitzer out of a 300 RUM at max velocity or a 250 gr bullet from a .30-30 and tell me it doesn't matter what velocity you load to. Taken to less extreme examples, I find best accuracy in my .25-06 with 100-120 gr. bullets loaded pretty near the top.

joed
June 18, 2012, 12:10 PM
In 35 years of loading cartridges I've found that the best accuracy generally does show up near max loads. I've only seen this with rifle cartridges and I'm sure there are exceptions.

I had one cartridge give great accuracy just above the minimum load once. But as I kept increasing the charge I saw accuracy fall apart and get better again. That cartridge and gun ended up very near max with great accuracy.

ranger335v
June 18, 2012, 01:11 PM
"Shoot the powder / bullet that gives you the most consistent exit velocity and you'll find you most consistent grouping, every time. "

Nope, that's badly incorrect.

627PCFan
June 18, 2012, 01:15 PM
Unfortunately I had a barrel that would not shoot anything accurately unless it was loaded over max and then some. That barrel aside I find slower does it :)

Clark
June 18, 2012, 03:48 PM
The reason benchrest guys are pushing the brass to the limit, is overcome wind.

The extra recoil from hot loads is not doing them any good.

The 30BR guys have the most immunity to wind, and they are having to touch the butt of the rifle with their shoulder, because there is so much more recoil.

murf
June 18, 2012, 11:32 PM
i'm not buying it either.

murf

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