Powder pressure curve. information...

[Longshot4]

In the past I had seen some kind of powder pressure curves. You know what I'm talking about? Spike over time with x load. I am wondering if a gentle up and down is more accurate. Accuracy is my goal. Can any one give me some references per case bullet load...?

[Unclenick]

There are lots of examples on this site selling an instrument for measuring chamber pressure. There are examples in this 1965 study of pressures that have more discussion.

The faster a powder burns, the faster the initial spike's rise for a given cartridge and bullet weight. If the average pressure during the bullet's whole trip down the barrel is the same for two different powders, then the projectile's kinetic energy and, therefore, the final velocity will be the same for both. In that instance, the faster powder produces a higher, faster spike, but does it with less total gas (the bullet is not as far down the barrel), so the muzzle pressure is lower. In comparison, the slower powder will use a higher total energy charge to produce more gas with a lower, slightly slower rising peak but also produces higher muzzle pressure to wind up at the same average.

Both examples could be a more accurate load. It depends on several factors. One is the barrel time. Even though the velocities in that example match, the faster powder will produce a shorter barrel time because it reaches its peak sooner, which is where bullet acceleration is at its maximum, so the bullet starts out faster down the barrel, shortening the time it takes to reach the muzzle. If the gun's barrel vibration sweet spot is better synchronized with a longer barrel time, it will like slower powder better and vice versa. Slower powder with its more gradual pressure slope and higher muzzle pressure and greater charge weight will produce more recoil because it ejects a larger quantity of gas at higher pressure. That's called the rocket effect and it can be responsible for over half the total recoil in some overbore cartridges (it is what a muzzle brake mitigates by venting gas sideways). The higher muzzle pressure means the muscle blast venting against the bullet base as it exits will contribute more to the bullet's initial yaw. This causes it to take a longer time for the bullet to "go to sleep" and has been measured to increase flight time by reducing the effective ballistic coefficient during the settling period.

Lots of tradeoffs and no simple answer, alas.

[Radny97]

In handguns, loads using faster powders are known to generally be more accurate than loads using slower powders. Not sure if that is the fault of the powder itself or some other factor.


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[74A95]

Originally Posted by Radny97

In handguns, loads using faster powders are known to generally be more accurate than loads using slower powders. Not sure if that is the fault of the powder itself or some other factor.


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Evidence?

[Radny97]

Just look up what all the bullseye shooters use. You know, the guys that need a 1911 to shoot a 1 inch group at 50 yards. They know a thing or two about handgun accuracy. And they are using 231, bullseye, WST, Clays, N310, and other fast powders. None of them use A9, or 2400, or HS-6, or 3N37 or other slow powders. There may be a number of reasons why this is, but the fact is that fast powders are preferred for accuracy loads in handguns.


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[74A95]

Originally Posted by Radny97

Just look up what all the bullseye shooters use. You know, the guys that need a 1911 to shoot a 1 inch group at 50 yards. They know a thing or two about handgun accuracy. And they are using 231, bullseye, WST, Clays, N310, and other fast powders. None of them use A9, or 2400, or HS-6, or 3N37 or other slow powders. There may be a number of reasons why this is, but the fact is that fast powders are preferred for accuracy loads in handguns.

The 45 ACP bullseye shooters use fast burning powders and light bullets at moderate speeds to keep recoil low.

From: https://www.shootingtimes.com/editor...-shooter/99418

"In keeping with the goal of low recoil, relatively fast-burning powders best achieve this goal. Fast-burning powders require less weight to reach a given velocity than slow-burning powders. Powder weight matters because a powder that requires less weight to push a given bullet to a given velocity produces less recoil than a powder that requires more weight. This is because the weight of the powder is part of the mass that is ejected out of the barrel along with the bullet. Through the principle of conservation of mass, the powder's weight is part of the formula to calculate recoil force, and less powder weight contributes less to the mass exiting the barrel."

9mm/38 Super bullseye shooters use medium speed powders, and in the 9mm lots of them like/use Power Pistol because of its accuracy. It usually has to be run pretty fast for the best accuracy, and some don't like the recoil but it's a small price to pay for top accuracy.

[Radny97]

Originally Posted by 74A95

The 45 ACP bullseye shooters use fast burning powders and light bullets at moderate speeds to keep recoil low.

From: https://www.shootingtimes.com/editor...-shooter/99418

"In keeping with the goal of low recoil, relatively fast-burning powders best achieve this goal. Fast-burning powders require less weight to reach a given velocity than slow-burning powders. Powder weight matters because a powder that requires less weight to push a given bullet to a given velocity produces less recoil than a powder that requires more weight. This is because the weight of the powder is part of the mass that is ejected out of the barrel along with the bullet. Through the principle of conservation of mass, the powder's weight is part of the formula to calculate recoil force, and less powder weight contributes less to the mass exiting the barrel."

9mm/38 Super bullseye shooters use medium speed powders, and in the 9mm lots of them like/use Power Pistol because of its accuracy. It usually has to be run pretty fast for the best accuracy, and some don't like the recoil but it's a small price to pay for top accuracy.

Recoil control is important for speed games like USPSA and IPSC. Bullseye has slow fire. Ten minutes to fire 10 shots. Even the rapid fire stages are only 5 shots in 10 seconds at closer targets. So recoil control is only a small part of the equation. Accuracy is far and away the most important, and those shooters are typically choosing fast powders to maximize accuracy. Sure there will be outliers like the power pistol powder in 9mm. Some combos of slower powder will work. But it’s not disputed that fast pistol powders are the most common choice, and this is among shooters where accuracy is king.


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[74A95]

Originally Posted by Radny97

Recoil control is important for speed games like USPSA and IPSC. Bullseye has slow fire. Ten minutes to fire 10 shots. Even the rapid fire stages are only 5 shots in 10 seconds at closer targets. So recoil control is only a small part of the equation. Accuracy is far and away the most important, and those shooters are typically choosing fast powders to maximize accuracy. Sure there will be outliers like the power pistol powder in 9mm. Some combos of slower powder will work. But it’s not disputed that fast pistol powders are the most common choice, and this is among shooters where accuracy is king.

In Bullseye, it's not about recoil control, it's about recoil force and the nervous system's annoying habit to anticipate recoil and flinch. More recoil means one is more likely to develop a flinch, and a flinch will cost points. From the link I posted earlier,

"The lightweight 185-grain bullets help reduce recoil. Recoil matters because low recoil means lesser incidence of flinching, and flinching is your enemy when trying to put bullets on the target. We can adapt to low-recoil loads, but it becomes more difficult to adapt as recoil increases."

Let's look at an article where a range of powder speeds (fast, medium, slow) was used to assess accuracy. Accuracy was the only goal. https://www.shootingtimes.com/editor...r-loads/326242 In that article on 38 Super accuracy, the author fired about 6,000 rounds from a Ransom Rest.

He writes, "Several powders stand out for producing excellent accuracy with many different bullets, including Bullseye, Unique, Silhouette, Power Pistol, W572, N340, N105, 3N38, and Longshot. Of these powders, N105 was the most consistently accurate with many bullets and a wide range of charge weights. This is a slow-burning powder that also goes by the name “Super Magnum” as it is considered a magnum pistol powder."

I do accuracy, too, from a Ransom Rest. I don't see fast powders as being more accurate than slow powders. What I see is that some powder/bullet combinations work well, and others don't. And it's not the same for every gun/barrel.

[Radny97]

Alright well we each have our opinion. Im not denying that certain combinations can result in great accuracy, regardless of the powder burn rate. Probably should leave the topic there as we’ve both said our piece and drifted a bit for the OP’s topic. Hopefully others chime in on his question.


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[Longshot4]

I have seen with my 45 ACP how bullseye a very fast powder will shoot paper targets with relatively tight groups. I figure the powder burns 100% before bullet leaves barrel. So energy of powder is used in the lenth of barrel. Where as a slower powder might not burn powder as completely causing energy waste out of barrel = less accuracy.

So that's what I'm looking for in relation to my 6mm creedmoor. So since 4166 is very accurate with a 95gr. bullet. I can only assume that with a 108gr. bullet might like a powder close to but not much faster and not slower than the 4166.

Since the equipment to run pressure tests on my load development is out of the question. I will have to run ladder tests... Read pressure signs and invest in some radar for best choice for the 6mm Creedmoor with 108gr. Well that is how I found 4166 and my new powder purchasing seams to be growing. If any one has found a pet load using a 108gr. bullet with a 1in8 twist I would be interested in hearing your input. Also I'm open for other comments.

Thanks to all for your input.

[74A95]

Originally Posted by Longshot4

I have seen with my 45 ACP how bullseye a very fast powder will shoot paper targets with relatively tight groups. I figure the powder burns 100% before bullet leaves barrel. So energy of powder is used in the lenth of barrel. Where as a slower powder might not burn powder as completely causing energy waste out of barrel = less accuracy.

Thanks to all for your input.

How many powders have you tested in your 45? Did you do accuracy tests with all these powders in a Ransom Rest?

I ran some numbers on Quickload in 45 ACP with Bullseye with 185, 200 and 230 grain bullets with Hornady load data. None of the loads produced 100% powder burn in a 5" barrel. None, and that included using powder weights past Hornady's maximum loads for Bullseye (more powder produces a greater % of powder burned).

I have Ransom Rest data in a 45 (1911 with a Kart barrel) with Bullseye and other powders. My results show that Bullseye has the same average 15-shot group size (1.78") as does Accurate #7 (1.72") using the same bullets. Bullseye runs about 90%+ powder burned in a 5" barrel. Accurate #7 shows a 50-65% powder burned in a 5" barrel. So, tell me again how you can predict accuracy based on burn rate or % of powder burned.

People, you really shouldn't just make stuff up out of thin air.

[Radny97]

74A95–Sigh ... The horse is already dead. Maybe address the OPs question?

I’ll contribute what i can to the OPs question. Speaking strictly regarding rifles:
If you flip through a few load manuals that show what was the most accurate load (like Lyman) it will frequently show that heavier for caliber bullets paired with slower powders get good accuracy and lighter for caliber bullets paired with faster powders get good accuracy. Take 270 Winchester. H4831 does well with 150 grain bullets. Whereas, Varget does well with 90 grain bullets. So that should tell you something about the relationship between the pressure curve and accuracy.
I’m guessing that there’s a sweet spot between acceptable velocity for the caliber and bullet and the pressure curve of the load. But having identified that there is an important relationship there, i have no idea how to go about calculating the optimal curve for a particular caliber and bullet weight.


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[74A95]

Originally Posted by Radny97

74A95–Sigh ... The horse is already dead. Maybe address the OPs question?

See the part I quoted. It was from the OP.

I asked how many powders the OP used for his accuracy comparison, or if the OP used a Ransom Rest for the accuracy tests. They seem like legit questions if one is making claims about a powder and doing accuracy comparisons. No reply from the OP yet.

The OP said Bullseye burns 100% in his 45. It does not in a 5" barrel, according to Quickload. That seems like legit technical information the OP might find of interest.

The OP tried to relate the % powder burned to accuracy. I provided Ransom Rest data that it does not. It seems that the OP and other readers might find this of interest if they had questions about how powder burn efficiency in a handgun might affect accuracy. I don't have data on rifle ammo, maybe someone else here does.

[Longshot4]

I was testing loads for 45 ACP a few years back. Tight Group, Red Dot and Bulls Eye and what I found record of quickly. Maby 231 also. When I found how bulls eye was working I tuned it in to a keeper. I believe Firing Line was helpful in my choice. That's why I like the sight. all range firing was at about 15Yds. off hand. I was practicing form.

[Longshot4]

74A95 So you come up with 90% burn. Good For you. So how did YOU do your figuring. It is simply estimation. That's all. So you use a rest. So what Opie. Assume nothing.

[Unclenick]

I think the idea quick powders are more accurate comes from target shooting, as Radny 97 suggested, and that's because of the .32 and .38 hollow base wadcutter ammo commonly used. With both, the soft, swaged commercial bullets can have their hollow bases partly blown open just after clearing the muzzle by the higher muzzle pressures associated with slow powders or even by an excessive charge of fast powder. That reshaping is seldom perfectly symmetrical and causes them to lose precision rather badly.

In general, higher muzzle pressure will exaggerate the adverse effect of an asymmetrical muzzle crown or a defect on a bullet's base. It also tends to blow more lead off the edges of the base of a cast bullet that has no gas check. But if a gun's muzzle is in good shape and the bullet bases are square and the influences are even all around the clock on the bullet, I've seen a lot of examples of both slow and fast powders shooting exceptionally well.

Back in 1909 (and therefore public domain, now) F. W. Mann's book, The Bullet's Flight… has photos of his experiments that raised muzzle pressure by cutting the barrel back until it was very short. This exaggerates the effect, but any unbalancing can cause accuracy issues, even if it is too small for a camera to pick up easily.

[74A95]

The idea that fast powders are more accurate might have an old correlation with lead hollow base bullets. Be that as it may, it would be limited to those bullets and at low speed as a special case.

But for other bullets it stands as an empirical question. Are fast powders more accurate in a handgun? Radny97 points to the powders that Bullseye shooter use. However, the article linked to points out that recoil force and flinching are good reasons to select fast powders - they produce the least recoil and less recoil is desirable to reduce flinching. That's sufficient reason to choose fast powders. One cannot, by extension, assume that only fast powders are accurate since slower powders are left out of the comparison. To say that slow powders are less accurate one must have tested slow powders and showed they were less accurate.

So, what about powder burn rate and accuracy? Ransom Rest results suggest there is no difference in accuracy based on burn rate. The accuracy comparison of the 38 Super ammo in the second link posted demonstrates that. My Ransom Rest data also shows no preference for fast burning powders with respect to accuracy. Accuracy appears to be a powder/bullet/gun combination, but some powders tend to do well overall and likely some powders do poorly overall.

The biggest factor in accuracy is probably the bullet. Powders, primers, OAL are probably secondary factors.

[Unclenick]

That was sort of my point. I think the wadcutter experience was extrapolated to include other loads without careful testing to confirm it. Flinching could certainly cause the perception slow powders cause a problem, particularly in bull's-eye shooting where you are required to shoot one-handed. That increases muzzle rise for any given amount of recoil, encouraging one to try to muscle the gun down. And, as I suggested, higher muzzle pressure will exacerbate problems caused by bullet base defects or crown defects, as well. Any opportunity for a gas stream to cause mischief at the muzzle will be made worse if the gas stream is stronger, and higher muzzle pressure makes that so.

But if you are shooting modern jacketed bullets with square bases too hard for significant gas cutting and don’t have a crown problem, and you aren’t at some very marginal gyroscopic stability factor, then there's little reason to expect a mechanical accuracy issue. I've shot sub-2 moa 25-yard groups off bags with a tuned 1911 shooting jacketed target bullets pushed by Bullseye powder, but I’ve also shot sub-2 moa 50-yard groups off bags with my Ruger Redhawk using jacketed HPs and 296, and you don't get much slower than that in a pistol powder.

[Radny97]

Originally Posted by 74A95

The biggest factor in accuracy is probably the bullet. Powders, primers, OAL are probably secondary factors.

Yes i agree.
You’re starting to convince me. I have to admit I’ve seen stellar accuracy from some very hot loads of H110 in handguns.


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[74A95]

Originally Posted by Radny97

Yes i agree.
You’re starting to convince me. I have to admit I’ve seen stellar accuracy from some very hot loads of H110 in handguns.

Yes, in my Ransom Rest results fast powders and slow powders are equally accurate. That said, some powders have produced better results than others. In the 45, BA10, a very fast powder, has given me very poor results with some of the most accurate 185 JHP bullets (Zero), so there's no clear advantage of burn rate there. My barrel (Kart) does not like that powder with those bullets. At the same time, A#7 has been constantly accurate with those same bullets, and rivals the best accuracy with fast powders. I've even tried Vit N105 in the 45 Auto. If I recall, it didn't burn efficiently (very wide extreme velocity spreads), but it sure produced nice groups.

Like the 38 Super article I put up the link for, I'm also a fan of the 38 Super, and I agree with the Author that Vit N105 is magical in the 38 Super. Low charges, high charges, whatever, it is amazingly accurate with all kinds of bullets. Not all bullets, but many that we consider quality bullets shoot really small groups. I love that powder in the 38 Super. Vit 3N38, another slow powder (just slightly faster than N105) also shoots really well in the 38 Super. For example, using a RMR 115 grain FMJ FP Match Winner bullet, 10.4 grains of 3N38 produced 1494 fps and put 25 shots into 1.28" as 25 Yards. The RMR FP match winner bullets have proven to be very accurate in my 9mm and 38 Super Kart barrels. Combined with the right powder, they can be extremely accurate and earn their name (in my barrels).

[stagpanther]

Since the equipment to run pressure tests on my load development is out of the question. I will have to run ladder tests... Read pressure signs and invest in some radar for best choice for the 6mm Creedmoor with 108gr. Well that is how I found 4166 and my new powder purchasing seams to be growing. If any one has found a pet load using a 108gr. bullet with a 1in8 twist I would be interested in hearing your input. Also I'm open for other comments.

I have 4166 but don't have the specific 108 gr Berger bullet you ask about. I have built 2 AR's based on the 6mm creedmoor; one an Odin (8) barrel and the other a McGowen (7). Both shoot very well. In addition, I've used both large and small primered cases, but don't have enough experience to conclusively draw an opinion on which may be better--other than relative case strength at the head. I do like the 105 to 108 gr eld-x bullets; with them I found some really good loads using PP 4000 MR, my 108 loads showed an excellent "sweet spot node" between 42.7 and 42.9 grs of 4000 MR. Obviously YRMV, what works for me may not for you.

I do have 105 hunting vlds and got very good results with 41.9 grs of IMR 4350. My faster McGowen barrel I've tried 110 MK's and even Nosler's 115 RDF's; ramshot magnum gave me good results with these bigger bullets.

Get a labradar--you won't be disappointed. Invest in quick load as well, especially if you like those peak pressure vs timing charts.

[5whiskey]

The biggest factor in accuracy is probably the bullet. Powders, primers, OAL are probably secondary factors.

Amen. Learning to cast has taught me this lesson. Base uniformity, base shape, symmetrical bearing surface, and (to a much lower degree) symmetrical bullet nose are far more important than powder type or charge... assuming that you are using an appropriate powder and charge weight for caliber and projectile weight.

[Longshot4]

As I look back to the Firing Line Sept.26 1916 loading of my 45 acp loading. I found that Rainer 200 gr. copper plated bullets were another part of the formula to good loads. The base was slightly concaved and with a round nose. So there we go with testing.

[Unclenick]

Was Ranier established before WWI?

[Longshot4]

Uclenick I finally found some understandable information on your references. I like the example of 6PPC. witch in my mind back in the day was the loading to bump 222 Rem. of the bench. The example of sweet spot pressure curve being determined by bullet seating.

It took me some time but I found some help from you again.