I overheard a friendly disagreement today between 2 guys that both shoot a lot of long range competition. One stated that if you find a particular load that is accurate in a rifle or handgun and find a different powder that gives you the EXACT same velocity that the accuracy will be the same. The other's argument was that the burn rate affected the accuracy more than muzzle velocity. He went on to state that one powder may have reached max velocity before the bullet left the barrel while another powder may still be gaining velocity when it leaves the barrel and while both may have the same muzzle velocity they would not give the same accuracy. Sometimes I overthink things and after listening to the discussion, I've been mulling this over all day. I know someone here that is much smarter than me will have the correct answer.
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Powder/velocity/accuracy question
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Twoboxer
Member
IMO, the difference between the two opinions is a consideration of barrel harmonics.
If two identical bullets leave a barrel at the same MV, they will spend the same time in the air affected by both gravity and wind. But repeatable "accuracy" requires more than very similar "times in the air". The launch point of these bullets must also be very similar.
When a cartridge is fired the forces released cause the barrel to oscillate. In order for two bullets to leave the muzzle at the same point in that oscillation (ie have the same launch point) and spend the same time in the air they must have the "same" MV AND spend identical times travelling through the barrel.
Since MV (and barrel time) will vary a bit round to round no matter how precise the loader was, it is best if muzzle exit is timed to occur at a point where the muzzle is moving as little as possible. If done, small differences in MV/BT will not change the launch point or the MV very much. You have an accuracy node.
It is possible for two different powders to produce equal MVs and equal BTs. In this case matching the MVs MAY produce the same level of accuracy.
It is also possible that two different powders will produce the same MVs but not have identical BTs. Now bullets will leave the barrel at a different point in its oscillation, and it may well be a point of much faster muzzle movement. So the same, ever-present differences in BT may cause larger changes in the launch point. And therefor a difference in accuracy.
Having said all that . . . when trying a new powder from the one used in your previously proven load, matching the old MV is a good place to start. In most cases, when using powders of somewhat similar burn rates, only a small adjustment to charge weight (ie MV) is likely to be required to produce similar accuracy.
And then there are the cases where nothing you do with that second powder matches the accuracy of your old powder lol. Just for fun you might ask those two guys what causes that
If two identical bullets leave a barrel at the same MV, they will spend the same time in the air affected by both gravity and wind. But repeatable "accuracy" requires more than very similar "times in the air". The launch point of these bullets must also be very similar.
When a cartridge is fired the forces released cause the barrel to oscillate. In order for two bullets to leave the muzzle at the same point in that oscillation (ie have the same launch point) and spend the same time in the air they must have the "same" MV AND spend identical times travelling through the barrel.
Since MV (and barrel time) will vary a bit round to round no matter how precise the loader was, it is best if muzzle exit is timed to occur at a point where the muzzle is moving as little as possible. If done, small differences in MV/BT will not change the launch point or the MV very much. You have an accuracy node.
It is possible for two different powders to produce equal MVs and equal BTs. In this case matching the MVs MAY produce the same level of accuracy.
It is also possible that two different powders will produce the same MVs but not have identical BTs. Now bullets will leave the barrel at a different point in its oscillation, and it may well be a point of much faster muzzle movement. So the same, ever-present differences in BT may cause larger changes in the launch point. And therefor a difference in accuracy.
Having said all that . . . when trying a new powder from the one used in your previously proven load, matching the old MV is a good place to start. In most cases, when using powders of somewhat similar burn rates, only a small adjustment to charge weight (ie MV) is likely to be required to produce similar accuracy.
And then there are the cases where nothing you do with that second powder matches the accuracy of your old powder lol. Just for fun you might ask those two guys what causes that
What he said, with the addition that the powder also has mass and effects the barrel harmonics as well, so different powders with different charge weights producing the same muzzle velocity will have slightly different harmonics.
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Generally speaking, the powder used makes a big difference, and there's more to replicating an accurate load than just duplicating velocity.
____
The *real* challenge is developing a load that shoots well in a large number of rifles.
____
Generally speaking, the powder used makes a big difference, and there's more to replicating an accurate load than just duplicating velocity.
____
The *real* challenge is developing a load that shoots well in a large number of rifles.
Ivan the Butcher
Member
This doesn't answer you question! If you are looking for an accurate load to just about any rifle, I start in 3 places;
1) The Lyman 45th Edition loading manual. It has duplication for factory loads and most accurate load. (from the 46th on, they dropped the Accuracy load info!)
2) Sierra Loading manual. It has a recommended Hunting and an Accuracy load for each bullet.
3 accuratereloading.com , It has a table of several powders and bullet weights, and lists group size and velocity. I have never found their info to be mistaken in any of my rifles that I tried their loads in! Example: If the data says 3800 fps gives 5 shot .145" groups, That is what I get. Go up or down 2 to 4 tenths of a grain, and the group opens up, sometimes to over an inch!
Different rifle/bullet combinations shoot best with the Overall Length set to different distance off the lands (many people call this "Jump"). Many of my guns like the bullet touching the lands. I have a few that like .005 to .010" off the lands.
I have one that likes touching with the 50 grain Sierra Blitz King and .025" Jump with the 50 grain Hornady V-Max, otherwise same load with same group and same point of impact. (very unusual!) I have a different rifle that likes Hornady 75 grain A-Max and Berger 77 grain VLD on the same load. The point of impact at 1000 yard is the same elevation, but the Berger's are 6" right (a little over 1/2 MOA, That is barely noticeable at 100 yards!) Both of these loads are almost .250 longer than SAAMI Max., this rifle and the one above both have 5.56 Chamber but are marked 223 Remington! (Chamber casting is the only way to check! unless you happen to have chamber reams setting around) In AR-15's we are finding many rifles marked 5.56 NATO but are actually 223 Wyld chambers especially with 1:8 and 1:7 twist barrels. 5.56 NATO and 223 Rem. still work fine (meaning safe) but accuracy often suffers with the shorter (factory length) ammo.
Just a few more things to look at when trying to duplicate a different rifle's load.
Ivan
1) The Lyman 45th Edition loading manual. It has duplication for factory loads and most accurate load. (from the 46th on, they dropped the Accuracy load info!)
2) Sierra Loading manual. It has a recommended Hunting and an Accuracy load for each bullet.
3 accuratereloading.com , It has a table of several powders and bullet weights, and lists group size and velocity. I have never found their info to be mistaken in any of my rifles that I tried their loads in! Example: If the data says 3800 fps gives 5 shot .145" groups, That is what I get. Go up or down 2 to 4 tenths of a grain, and the group opens up, sometimes to over an inch!
Different rifle/bullet combinations shoot best with the Overall Length set to different distance off the lands (many people call this "Jump"). Many of my guns like the bullet touching the lands. I have a few that like .005 to .010" off the lands.
I have one that likes touching with the 50 grain Sierra Blitz King and .025" Jump with the 50 grain Hornady V-Max, otherwise same load with same group and same point of impact. (very unusual!) I have a different rifle that likes Hornady 75 grain A-Max and Berger 77 grain VLD on the same load. The point of impact at 1000 yard is the same elevation, but the Berger's are 6" right (a little over 1/2 MOA, That is barely noticeable at 100 yards!) Both of these loads are almost .250 longer than SAAMI Max., this rifle and the one above both have 5.56 Chamber but are marked 223 Remington! (Chamber casting is the only way to check! unless you happen to have chamber reams setting around) In AR-15's we are finding many rifles marked 5.56 NATO but are actually 223 Wyld chambers especially with 1:8 and 1:7 twist barrels. 5.56 NATO and 223 Rem. still work fine (meaning safe) but accuracy often suffers with the shorter (factory length) ammo.
Just a few more things to look at when trying to duplicate a different rifle's load.
Ivan
ArchAngelCD
Moderator, SWCA Member, Absent Comrade
In addition, case fill also effects accuracy. It seems with smokeless powders getting close to or at 100% case fill improves accuracy and consistency. Powder burn speed comes into play in case fill so it's not velocity alone like said above.
I understand the velocity argument but there is so much more, most of which I don't have an in depth understanding since I'm not a ballistics engineer.
I understand the velocity argument but there is so much more, most of which I don't have an in depth understanding since I'm not a ballistics engineer.
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There's a lot of stuff you're asking. I'll itemize.
(1) In rifles, it's considered fairly common to find "accurate" velocities. In other words, if Powder X is most accurate loaded to 2700 fps, then Powder Y will also be most accurate at 2700 fps, presuming there's no great mis-match in burn rates. HOWEVER, Powder Y may not be as accurate as Powder X. While I believe in accurate velocities within a given powder, I haven't had the chance to really delve into matching velocities between powders.
(2) Long range rifle loading is a different animal. Consistent velocity is more important than absolute accuracy. So it's quite common to test ascending charges to find flat spots in the velocity curve where a couple tenths of a grain of powder doesn't move the velocity much, and then test that small subset of charges for accuracy before moving on to seating depth.
(3) The reason the long range rifle shooter doesn't give a damn about maximizing accuracy is that
*the best-shooting load might be .5MOA, and the worst might be .7, in his very nice gun, with his excellent components
*he's shooting at 700-1200 yards, and .5MOA doesn't produce anywhere near as much dispersion as variations in velocity, both for wind drift and drop at extreme distances
(4) Ergo, you may or may not care about what the long range guys do.
(5) There's a whole different school of thought that revolves around optimum charge weight, and and another seeks to equalize bullet dwell time in the barrel and other voodoo I don't understand. I was going to study it, but honestly, the techniques I understand now already produce great results for me. My time would be better spent reloading and shooting more.
(6) Barrel harmonics is real. I can't locate it atm, but there's a series of 1-shot targets from an indoor range, showing how varying bullet dwell times caused POI shifts up and down, and slightly side-to-side. But frankly, so long as the bullet is leaving the barrel when it's at a consistent position, it doesn't matter. But it does explain why groups shrink and open in cycles.
(7) Sometimes, depending on the cartridge, the most accurate powder is simply well-known. In 6.5CM, for instance, it's Hodgdon 4350 (unless you want to be a damn hipster and use IMR 4350). Everyone pretty much starts there There's a reason so many .223 varminters lean on Varget.
Personally, I test velocity with ascending charges in .1-grain increments, hand-trickled. The .,1-grain increment (as opposed to more traditional 10-round, .2-grain increments) combats some of the variation while still letting me see accuracy nodes pretty easily. Especially because I can see obvious inconsistent velocities at the very bottom, and compare them to flat accuracy nodes at (usually) 90% max. It's not uncommon for me to find single-digit extreme spreads this way, both across spans, and then in five-round test groups later. Whether by accident or by design, this has resulted in excellent loads in less than a single box of "test" ammo--25 rounds to look for the node, and then another 25 to test 3-5 charges later.
(1) In rifles, it's considered fairly common to find "accurate" velocities. In other words, if Powder X is most accurate loaded to 2700 fps, then Powder Y will also be most accurate at 2700 fps, presuming there's no great mis-match in burn rates. HOWEVER, Powder Y may not be as accurate as Powder X. While I believe in accurate velocities within a given powder, I haven't had the chance to really delve into matching velocities between powders.
(2) Long range rifle loading is a different animal. Consistent velocity is more important than absolute accuracy. So it's quite common to test ascending charges to find flat spots in the velocity curve where a couple tenths of a grain of powder doesn't move the velocity much, and then test that small subset of charges for accuracy before moving on to seating depth.
(3) The reason the long range rifle shooter doesn't give a damn about maximizing accuracy is that
*the best-shooting load might be .5MOA, and the worst might be .7, in his very nice gun, with his excellent components
*he's shooting at 700-1200 yards, and .5MOA doesn't produce anywhere near as much dispersion as variations in velocity, both for wind drift and drop at extreme distances
(4) Ergo, you may or may not care about what the long range guys do.
(5) There's a whole different school of thought that revolves around optimum charge weight, and and another seeks to equalize bullet dwell time in the barrel and other voodoo I don't understand. I was going to study it, but honestly, the techniques I understand now already produce great results for me. My time would be better spent reloading and shooting more.
(6) Barrel harmonics is real. I can't locate it atm, but there's a series of 1-shot targets from an indoor range, showing how varying bullet dwell times caused POI shifts up and down, and slightly side-to-side. But frankly, so long as the bullet is leaving the barrel when it's at a consistent position, it doesn't matter. But it does explain why groups shrink and open in cycles.
(7) Sometimes, depending on the cartridge, the most accurate powder is simply well-known. In 6.5CM, for instance, it's Hodgdon 4350 (unless you want to be a damn hipster and use IMR 4350). Everyone pretty much starts there There's a reason so many .223 varminters lean on Varget.
Personally, I test velocity with ascending charges in .1-grain increments, hand-trickled. The .,1-grain increment (as opposed to more traditional 10-round, .2-grain increments) combats some of the variation while still letting me see accuracy nodes pretty easily. Especially because I can see obvious inconsistent velocities at the very bottom, and compare them to flat accuracy nodes at (usually) 90% max. It's not uncommon for me to find single-digit extreme spreads this way, both across spans, and then in five-round test groups later. Whether by accident or by design, this has resulted in excellent loads in less than a single box of "test" ammo--25 rounds to look for the node, and then another 25 to test 3-5 charges later.
My rifle loads from 22-250 to 30-40 Krag and 375 Winchester
all have been tried with at least eight types of powders, of all types
and burning speeds , from light target to MAXIMUM loads with
several weight and styles of bullets.
Out of lets say, eight powders, maybe three will be in the better powders
for a certain speed that has good accuracy at a needed range.
Of these three only ONE powder will have the BEST accuracy, generally.
I am leaving all the fine points out like OAL, primer, crimp etc.
to keep this simple.
I will add that I also believe in a rifle case with at least a 80% volume and 90% is even better.
The same goes for my revolvers and pistols, that I load for.
A certain weight bullet has its starting speeds and maximum....
which can be very different from the fast to the slower burning powders.
Generally the fast powders work well with the light target loads and
the slow powders work with the maximum loads to get higher fps.
I have learned over time that a "Full Load" has lots of energy but.....
very seldom does a 100% load turn out the TOP Accuracy in the weapon.
My 22-250 loves the Rem. 55 FMJ with SR4759 at 2750fps and IMR4064 at over 3,600fps.
My Win. 270 sierra 130 BT loves IMR4831 at 2700fps and 4350 at 2955fps
My 30-06 likes a 100 plinker with SR4759 at 1,600fps for 50 yard plinking
a Military case, 150 FMJ with 4895 at 2590fps a 165gr Sierra at 2960 to a factory 180 With H414 around 2600fps or down loaded
to the Krag's 2430fps that saves a LOT of deer meat !!
Accuracy and a "GOOD Load" are two different things but both are a good thing,
no matter how one achieves it.
One reason I enjoy "Rolling my own".
all have been tried with at least eight types of powders, of all types
and burning speeds , from light target to MAXIMUM loads with
several weight and styles of bullets.
Out of lets say, eight powders, maybe three will be in the better powders
for a certain speed that has good accuracy at a needed range.
Of these three only ONE powder will have the BEST accuracy, generally.
I am leaving all the fine points out like OAL, primer, crimp etc.
to keep this simple.
I will add that I also believe in a rifle case with at least a 80% volume and 90% is even better.
The same goes for my revolvers and pistols, that I load for.
A certain weight bullet has its starting speeds and maximum....
which can be very different from the fast to the slower burning powders.
Generally the fast powders work well with the light target loads and
the slow powders work with the maximum loads to get higher fps.
I have learned over time that a "Full Load" has lots of energy but.....
very seldom does a 100% load turn out the TOP Accuracy in the weapon.
My 22-250 loves the Rem. 55 FMJ with SR4759 at 2750fps and IMR4064 at over 3,600fps.
My Win. 270 sierra 130 BT loves IMR4831 at 2700fps and 4350 at 2955fps
My 30-06 likes a 100 plinker with SR4759 at 1,600fps for 50 yard plinking
a Military case, 150 FMJ with 4895 at 2590fps a 165gr Sierra at 2960 to a factory 180 With H414 around 2600fps or down loaded
to the Krag's 2430fps that saves a LOT of deer meat !!
Accuracy and a "GOOD Load" are two different things but both are a good thing,
no matter how one achieves it.
One reason I enjoy "Rolling my own".
old tanker
Member
Maybe I am approaching the problem wrong, but I seem to have better luck trying a bunch of bullets first to see if there is one the gun "likes" then fine tune, seating depth, powder etc. It's not always clear why but I have one rifle that slings 168 grain Sierra match kings all over the countryside, but clusters 165 grain Speer semi-spitzer softpoints into tidy clusters. The powder charge makes a little difference, but no powder will make the Sierra outperform almost any reasonable random charge under the Speer in that rifle, certainly. Maybe others, sometimes the more I study the notes, the less sure I get.
scooter123
Member
I am a firm believer that Powder can make a significant difference in Accuracy because I've seen it first hand and it was DRASTIC.
I have an AR-15 that I assembled using a Gibbz Arms Side Charging Upper with a 20 inch Shilen precision barrel in 223 Wylde.
With a load using Varget and a 60 grain Nosler Ballistic tip sub 3/8 inch groups at 100 yards are simply a matter of careful aim and trigger release. Muzzle velocity of this particular load clocks an average of 2706 fps.
One problem with Varget is that it meters poorly and when I'm loading for precision I want my charges within 0.05 grains, so I keep some fine tweezers next to the scale and adjust each charge granule by granule. That is sorta time consuming. So I was looking for a powder that I could trust the metering to hold within 0.10 grains and the powder I found was CFE 223.
Tested the CFE and it was a near match in accuracy of my most accurate load featuring Varget and a 68 grain Hornady BTHP bullet. The Varget load yields sub 0.30 inch groups while the "throw and go" CFE loads produced 0.34 inch groups. So next up was to test the CFE with my "Coyote" bullet, the 60 grain Nosler. That load didn't work out very well, groups grew to 3.4 inches at 100 yards. Did test the velocity and it was running 2672 fps average.
So, to sum it up, every item used was identical for each load. Same Lake City 5.56 cases sized on the same .223 die set and trimmed to the same overall length. Same Nosler 60 grain Ballistic tip, in fact they came out of the same box. Same CCI Small Rifle primer. Nearly identical produced muzzle velocity. The ONLY difference was the powder used. Groups with Varget ran 0.36-0.37 inch, groups with CFE223 grew to 3.4 inches. Yeah, hard to believe. Fact is that I thought the scope had shot loose but since I ha some of the Hornady loads with me I thought I would use them to check the scope and they shot dead center with a cloverleaf at 100 yards. So it wasn't a loose scope, it wasn't a barrel nut that shot loose, and it wasn't a fouled bore. The only cause for that drastic difference was the powder and to this day I have no clue as to why the accuracy fell off so severely because it plain doesn't make any sense at all to me.
I have an AR-15 that I assembled using a Gibbz Arms Side Charging Upper with a 20 inch Shilen precision barrel in 223 Wylde.
With a load using Varget and a 60 grain Nosler Ballistic tip sub 3/8 inch groups at 100 yards are simply a matter of careful aim and trigger release. Muzzle velocity of this particular load clocks an average of 2706 fps.
One problem with Varget is that it meters poorly and when I'm loading for precision I want my charges within 0.05 grains, so I keep some fine tweezers next to the scale and adjust each charge granule by granule. That is sorta time consuming. So I was looking for a powder that I could trust the metering to hold within 0.10 grains and the powder I found was CFE 223.
Tested the CFE and it was a near match in accuracy of my most accurate load featuring Varget and a 68 grain Hornady BTHP bullet. The Varget load yields sub 0.30 inch groups while the "throw and go" CFE loads produced 0.34 inch groups. So next up was to test the CFE with my "Coyote" bullet, the 60 grain Nosler. That load didn't work out very well, groups grew to 3.4 inches at 100 yards. Did test the velocity and it was running 2672 fps average.
So, to sum it up, every item used was identical for each load. Same Lake City 5.56 cases sized on the same .223 die set and trimmed to the same overall length. Same Nosler 60 grain Ballistic tip, in fact they came out of the same box. Same CCI Small Rifle primer. Nearly identical produced muzzle velocity. The ONLY difference was the powder used. Groups with Varget ran 0.36-0.37 inch, groups with CFE223 grew to 3.4 inches. Yeah, hard to believe. Fact is that I thought the scope had shot loose but since I ha some of the Hornady loads with me I thought I would use them to check the scope and they shot dead center with a cloverleaf at 100 yards. So it wasn't a loose scope, it wasn't a barrel nut that shot loose, and it wasn't a fouled bore. The only cause for that drastic difference was the powder and to this day I have no clue as to why the accuracy fell off so severely because it plain doesn't make any sense at all to me.
fredj338
Member
The first would be 100% false. It isnt just the vel but the pressure curve that affects the accuracy node. I have shot enough diff rifle calibers out at 300y to know switching pieders, even primers with the same powder can have a significant affect on accuracy.
Accuracy loars start with a well built, properly scoped rifle, good technique & the best bullets. No amount of tinkering will make a poor rifle shoot. I try one powder that gives me the vel range I want, work up with one bullet. With a good load I will then try diff primers & oal to fine tune. Some bullets wont shoot well in some rifles, just the way it is.
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Ivan the Butcher
Member
Look at similar bullets by different manufacturers. I load 221 Fireball, 218 Bee (Ruger No.1), 223 Rem in Cooper 21, 22-250, & 22BR all with a 50 grain poly tipped/boat tail bullet. There are basically 4 makers: Nosler, Hornady, Sierra, & Combined Technologies. I use whatever I have the most of to develop the powder charge and seating depth (Jump). After that is settled I load 5 rounds of each of the other three. Of those 4 bullets a rifle will prefer one over the others. Most to least common are: Combined Tech., Sierra & Nosler are equal and Hornady is last. (But Last place is still really good!) We are usually talking a difference of .1 MOA @ 200 yards (2/10"), but every little bit helps!
Ivan
Ivan
Biggfoot44
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AND still further , the initial pressure curve can have a big effect on bullet obduration . Not as much an issue with with jacketed bullets in rifle , it can be significant with either type in revolvers, and cast bullets in rifles .
A bullet shape can make or break a load for accuracy.
My 22-250 is famous for not liking bullet shapes and weights with its 1:14 barrel twist.
A 55gr V-Max is longer than the long heavy 70gr speer bullet !
The Remington 55gr FMJ has less bearing surface than the little
52gr flat base from Hornady.
Some times the amount of "Copper" that hits the lands in my rifle
can make a big difference in a groups size.
Plus, it is not always the pretty B/T or pointy Hollow Points that take
first place in my rifle.
For some odd reason the flat base, round nose Speer 55gr "Std bullet" with a max load of w748 beat out all other 55gr bullets.
I do however have five different bullets, weights and styles that
go from paper killers to almost disintegrating after leaving the barrel, that give me top accuracy from 100 to 400 yards.
Same goes for my 30-06, with slow to factory loads that make me happy
but I did go through a LOT of different weight and styles to be a happy camper.
My 22-250 is famous for not liking bullet shapes and weights with its 1:14 barrel twist.
A 55gr V-Max is longer than the long heavy 70gr speer bullet !
The Remington 55gr FMJ has less bearing surface than the little
52gr flat base from Hornady.
Some times the amount of "Copper" that hits the lands in my rifle
can make a big difference in a groups size.
Plus, it is not always the pretty B/T or pointy Hollow Points that take
first place in my rifle.
For some odd reason the flat base, round nose Speer 55gr "Std bullet" with a max load of w748 beat out all other 55gr bullets.
I do however have five different bullets, weights and styles that
go from paper killers to almost disintegrating after leaving the barrel, that give me top accuracy from 100 to 400 yards.
Same goes for my 30-06, with slow to factory loads that make me happy
but I did go through a LOT of different weight and styles to be a happy camper.
Been reloading for almost 60 years. Studied every thing I could read. What has been said here is correct and I can only add that the individuals assumption was incorrect. Good thread Guys.
Qc Pistolero
Member
Trying to sum it all up with the simple argumentation the two gentleman had in OP would be called an oversimplification of the whole spectrum...almost like saying that the whole universe is our planet and its satellite revolving around the sun.
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