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Discussion Starter · #1 ·
Hello to the forum, I have been trying new loads & differant bullets and have a question. Comparing the factory LF ss195 ammo to my reloads POA without the use of a cronagraph. First, I am using a 45 grain Speer SP bullet with 6.2 grains of AA#5 with an overall cartridge length of 1.556. I have shot a few of these test loads and found no pierced primers or ejected primers, also comparing a fired factory case to a reload, there was no noticiable differance between the the expansion of the shoulder even though it felt like there was a bit more recoil (most likely because of the heavier bullet). Anyway the point of aim changes to about 3" lower at 30 feet with my FiveseveN handgun than factory ammo, so is this an indication of a slower or faster velocity? Thanks for any help, LM.
 

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Slower velocity.

In this case, you went from a 28 grain projectile (SS195) to a 45 grain projectile. Even with the 6.2 grains of faster burning AA#5 vs the slower Ramshot True Blue (it's actualy a european powder very similar to True Blue), the faster powder was not enough to overcome the increased weight of the projectile.

You also have to consider that the increased weight will react different in a gravitational field. Think of it as throwing a lead ball (the 45 grain projectile) vs a feather (the 28 grain projectile) - which will fall to the ground faster? (Remember we are not even close to approaching terminal velocity in this discussion).

Sometimes a faster burning powder can overcome the drop in velocity that results in the projectile POI drop, but at an INCREASED pressure which can make your firearm go KB. Remember that the COL will also affect the pressure gradient on the cartridge. The less the COL is, the more pressure that you will have to deal with. It varies with powder but with the data that I have on True Blue, even a .001 in change in COL will increase pressure by about 30 psi. Doesn't seem like much but at .1 in, the pressure can increase by over 300 PSI. The pressure will also increase a significant amount because of the barrel length. The longer the barrel (PS90) the more time the powder has to expend its energy resulting in a higher pressure which results in a higher velocity. That is why the same SS195LF cartridge fired from the FiveseveN will reach about 1930 fps vs 2400 fps out of the PS90 but at a pressure increase of over 4000 PSI.

There are reloaders both here and on the 'other forum' that use AA powder that may be able to assist you further. I am strictly a True Blue powder person for my 5.7 cartridges.
 

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HK SD9 Tactical said:
You also have to consider that the increased weight will react different in a gravitational field. Think of it as throwing a lead ball (the 45 grain projectile) vs a feather (the 28 grain projectile) - which will fall to the ground faster? (Remember we are not even close to approaching terminal velocity in this discussion).
can you explain this more? I thought that two things the same size and shape would fall at the same rate- regardless of their weight.
 

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Promoted Pawn said:
HK SD9 Tactical said:
You also have to consider that the increased weight will react different in a gravitational field. Think of it as throwing a lead ball (the 45 grain projectile) vs a feather (the 28 grain projectile) - which will fall to the ground faster? (Remember we are not even close to approaching terminal velocity in this discussion).
can you explain this more? I thought that two things the same size and shape would fall at the same rate- regardless of their weight.
While his analogy isn't completely accurate, his logic is.

Basically, things fall the same rate in a vacuum. But, in atmosphere every object will have a different terminal velocity based on a few factors;

1; It's profile (resistance)
2; weight / overall size (density)


Which is to say that an expanded Parachute is what keeps a skydiver from hitting the ground at such high speeds - the fact that it so much increases the profile of the skydiver.

Versus a hot air balloon, which so much decreases the density (hot air weighs less than cold air), and makes the density so much lower.
 

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POA?

Seems that the Pawn and I have the same questions, this needs more info than you supplied. I usually believe the old adage that its light bullet low, heavy bullet high, but at 30 ft, this is a very short distance for this amount of drop. I think you might mean POI intead of POA, or are you holding off to get the same POI? type of weapon is helpful also. If you are actually holding low 3" with the 45gr load to hit the same group then the adage applies . The exterior ballistcs argument is a whole nuther ball game. Its more a matter of time of flight at a given velocity for a specific bullet weight. Gets real mathmatical the further you get into it.
 

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Re: POA?

SOFMatchstaff said:
Seems that the Pawn and I have the same questions, this needs more info than you supplied. I usually believe the old adage that its light bullet low, heavy bullet high, but at 30 ft, this is a very short distance for this amount of drop. I think you might mean POI intead of POA, or are you holding off to get the same POI? type of weapon is helpful also. If you are actually holding low 3" with the 45gr load to hit the same group then the adage applies . The exterior ballistcs argument is a whole nuther ball game. Its more a matter of time of flight at a given velocity for a specific bullet weight. Gets real mathmatical the further you get into it.
I also took it to mean POI instead of POA. But at 30 feet, thats a large differential between POA and POI for a 45g vs 28g projectile.

Lightningman did specify the use of the FiveseveN.

Either way, both you and Pawn are correct in that more information is needed.

Pawn: Marc is correct. In a vacume, both objects would fall at the same rate however, with the atmospheric variable involved, the fall rates are different - not substantially in this case, but there is a difference. Thanks to both of you for clarifying this further.
 

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Discussion Starter · #7 ·
Hello again, I had to add that I was holding the pistol sights at the same point on the paper target (which was the center bullseye) with both types of ammo. (factory & reloads) The factory rounds hit sightly above the bullseye in the second black ring and the reloads hit low at just below the outer black ring or in the first white ring of an offical 50' slow fire pistol target. I would also like to add that I tried a couple rounds of earlier loads of 6.4 grains of AA#5 and felt they were a bit too warm & nearing the unsafe zone. Thats when I backed down the charge to 6.2 and I think this is better. LM
 

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HK SD9 Tactical said:
You also have to consider that the increased weight will react different in a gravitational field. Think of it as throwing a lead ball (the 45 grain projectile) vs a feather (the 28 grain projectile) - which will fall to the ground faster? (Remember we are not even close to approaching terminal velocity in this discussion).

This is incorrect.

All objects of different masses will "react" exactly the same to a given gravitational field, and by "react" we are referring to gravitational acceleration (Newton's law of universal gravitation). The analogy of a lead ball vs a feather is false in that air resistance acts in opposition to gravity on the feather, so that would slow the fall of the feather. In the case of his two bullets they are (for all practical measurements) identical in terms of aerodynamics and will accelerate (drop) towards the earth at the standard value of 9.81 m/s².
 

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YA, what he said! :lol: :?
 

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POI

Sorry, the fiveseveN sentence registered in my head as a cartridge instead of a weapon.

The load you spec'd should give about 1800fps+- from the pistol vs 1930fps for the factory ammo, this is subject to seating depth variations as referenced by HK, and a bunch of other factors.

Farmer Ted is correct as far as he went, the time of flight(velocity) plugged into the equation will show that the lighter/faster projo is acted on by gravity for a shorter period than the heavier/slower projo. This time factor causes the difference in drop and impact if all the physical firing parameters are equal,as in parallel to the ground, I believe they will both hit the ground at the same time, just at different points. Its been awhile.

The recoil factor is similar in that the weight of the projo dictates the amount of recoil, and muzzle rise. If the heavy projo leaves the muzzle with weapon further into recoil, the POI will be higher than if a light projo is ejected when the muzzle is just begining to rise in recoil. Again the firing parameters have to be the same. Heavy bullet high, light bullet low. SO, your question was, is this an indication of a faster or slower Velocity, its an indication of a faster vel, but not proof of same. The chrono is the only way to a definitive measurement.

Some loads just shoot a different POI with the same POA . I've experienced this alot over the years, and chock it up to different component characteristics. That the fun of all this isn't it?
 

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Dude, this sucks. I had a nice response to Farmer Ted's post that took a substantial amount of time to weigh through and the damn post was lost.

Crimminy - Suffice it to say that I do not agree entirely with Farmer Ted's post. While I agree with it if we are talking MASS, I disagree with it as we are talking about WEIGHT. They are vastly different in reference to physics and the sciences.
 

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HK SD9 Tactical said:
Dude, this sucks. I had a nice response to Farmer Ted's post that took a substantial amount of time to weigh through and the damn post was lost.

Crimminy - Suffice it to say that I do not agree entirely with Farmer Ted's post. While I agree with it if we are talking MASS, I disagree with it as we are talking about WEIGHT. They are vastly different in reference to physics and the sciences.
Yes there is a difference between weight and mass but in this case it is largely irrelevant on point (I stated mass as well).

The distinction does not change your false premise that the lead ball/feather hit the ground at different times is due to their differing weights (air resistance is what is causing this), or that this premise is what is causing the differing POI’s (it’s their relative speed over the same distance causing different POI’s). Both bullets are falling at the same speed and will hit the ground at the same time, one is just covering more horizontal distance than the other simply because it is traveling faster.




 

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Farmer Ted said:
HK SD9 Tactical said:
Dude, this sucks. I had a nice response to Farmer Ted's post that took a substantial amount of time to weigh through and the damn post was lost.

Crimminy - Suffice it to say that I do not agree entirely with Farmer Ted's post. While I agree with it if we are talking MASS, I disagree with it as we are talking about WEIGHT. They are vastly different in reference to physics and the sciences.
Yes there is a difference between weight and mass but in this case it is largely irrelevant on point (I stated mass as well).

The distinction does not change your false premise that the lead ball/feather hit the ground at different times is due to their differing weights (air resistance is what is causing this), or that this premise is what is causing the differing POI’s (it’s their relative speed over the same distance causing different POI’s). Both bullets are falling at the same speed and will hit the ground at the same time, one is just covering more horizontal distance than the other simply because it is traveling faster.




Nice graphic.

My use of the feather/ball thing was overly simplistic and was used to identity the differences in projectile profiles and their resistance to travel along the path of flight (it is why I used the term throw and not drop) - sorry for the confusion it caused. I should not have brought gravity into this discussion at all.

All things being EQUAL, I agree with your analysis that the 'fall rate' is nearly identical and that velocity plays the major role in this example as to where the projectile will strike the target in reference to the aim point. There are other factors such as the equivalence principle and the equality of gravitational and inertial mass that affect falling objects. Other such principles are even perported to indicated that a more massive object will fall SLOWER. Go figure.

Lightningman: Thanks for the clarification of your POA and POI.
 

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HK SD9 Tactical said:
My use of the feather/ball thing was overly simplistic and was used to identity the differences in projectile profiles and their resistance to travel along the path of flight (it is why I used the term throw and not drop) - sorry for the confusion it caused. I should not have brought gravity into this discussion at all.

All things being EQUAL, I agree with your analysis that the 'fall rate' is nearly identical and that velocity plays the major role in this example as to where the projectile will strike the target in reference to the aim point. There are other factors such as the equivalence principle and the equality of gravitational and inertial mass that affect falling objects. Other such principles are even perported to indicated that a more massive object will fall SLOWER. Go figure.
Throw vs drop is not simplistic it is irrelevant as the external application of force (gravity) is still equal to both bodies, the extreme difference between feather vs ball "drop" is due only to the vastly dissimilar resistance of each body in air. Of the two bullets mentioned this point is irrelevant (in the vertical plane) as they are of such similar ballistic coefficient, the difference only affects the bullets lateral velocity which is arbitrary in that one would be measuring this velocity after resistance has effected both bodies.

Things are equal in that we are comparing two similar bodies each at their own independent velocity, this velocity (given a distance of x) is the only factor that affects point of impacts vs. point of aim.

All of the other factors mentioned such as the “equivalence principle” are utterly absurd to bring up in even a formal discussion let alone raise as “minor” factors in a discussion such as this. The best minds & equipment of the last century have only been able to measure these differences in orders of one part per trillion, for a simple frame of reference that would be like firing a shot from the earth at a quarter sitting on the moon and blaming the “equivalence principle” because you only nicked it.

And besides, for a shot like that I would use this →
:-x
 
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