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"Loads close to the max pressure are more accurate"

Discussion in 'Handloading and Reloading' started by willypete, Jun 15, 2012.

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  1. willypete

    willypete Member

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    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.
     
  2. Claude Clay

    Claude Clay Member

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    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.
     
  3. EchoM70

    EchoM70 Member

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    Generally in my experience loads that are 1 grain under max always seem to be the most accurate for me.
     
  4. willypete

    willypete Member

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    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?
     
  5. EchoM70

    EchoM70 Member

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    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.
     
    Last edited: Jun 15, 2012
  6. Deus Machina

    Deus Machina Member

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    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.
     
  7. T Bran

    T Bran Member

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    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
     
  8. 27hand

    27hand Member

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    max loads

    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.
     
  9. B!ngo

    B!ngo Member

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    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
     
  10. Kachok

    Kachok Member

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    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.
     
  11. blarby

    blarby Member

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    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.
     
  12. jmr40

    jmr40 Member

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    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.
     
  13. scythefwd

    scythefwd Member

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    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??
     
  14. beatledog7

    beatledog7 Member

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    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.
     
  15. ranger335v

    ranger335v Member

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    "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.
     
    Last edited: Jun 16, 2012
  16. USSR

    USSR Member

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    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
     
  17. Walkalong

    Walkalong Moderator

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    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.
     
  18. Ky Larry

    Ky Larry Member

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    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.
     
  19. ljnowell

    ljnowell Member

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    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.
     
  20. MCMXI

    MCMXI Member

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    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.
     
  21. Kachok

    Kachok Member

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    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.
     
  22. gunfighter48

    gunfighter48 Member

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    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.
     
  23. jcwit

    jcwit Member

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    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.
     
  24. kcshooter

    kcshooter Member

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    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.
     
  25. Trent

    Trent Resident Wiseguy

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    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.
     
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