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Bullet weights?

Discussion in 'Handguns: General Discussion' started by Smokepole14, Dec 8, 2019.

  1. Walt Sherrill

    Walt Sherrill Member

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    That's true with a revolver or a fixed-barrel semi-auto (like most .22s, .25s, .32s, and .380s). With these guns recoil begins to be transferred to the frame as soon as the bullet starts to move down the barrel. As the bullet moves on down the barrel, the barrel and frame move to the rear, and the force of rearward movement is transferred to the shooter's hand and the frame rocks back. And because the bulk of the force being transferred is above the hand causes the gun above the hand to move rearward and the barrel to rise. The barrel tilts because the grip frame is held by the hand.

    What you describe is true of fixed barrel guns, but things work differently with most center-fire semi-autos, which generally use a variant of the Browning Short Recoil Locked Breech (SRLB) design.​

    With the SRLB design, the slide and barrel are locked together and move to the rear as soon as the bullet begins to move down the barrel. But the transfer of recoil force to the frame is briefly attenuated or delayed and as the slide moves horizontally to the rear. During the first part of that brief period of slide/barrel rearward movement, the bullet will exit the barrel before the barrel and slide has moved less than 1/10th of an inch to the rear.

    The only rearward movement that can cause barrel rise which would affect the bullet's point of impact through recoil force transfer occurs during that 1/10th of an inch of slide/barrel travel. There's not much force transferred to the frame (via the recoil spring assembly) during that slight bit of slide/barrel movement. It can affect the bullet's point of impact, but not ANYTHING like what you describe in your comment above.​

    Once the bullet is gone, the rest of the recoil force -- which is MOST OF IT -- causes the barrel and slide to continue their rearward movement, and recoil force is passed to the gun's frame through the base of the recoil assembly and the barrel and moved shifted to the rear by the slide moving to the rear add to the effects of recoil. But none of this substantial recoil force has any effect on the bullet -- as it's already long gone.

    Check out any number of the ultra-high-speed videos of SRLB semi-autos being fired on YouTube. You'll see that there is virtually no visible or measurable barrel rise prior to the bullet's exit from a SRLB gun's barrel. If the video continues, you'll see a lot of barrel rise and frame movement after the bullet is gone. You'll see something different with revolvers and fixed barrel semi-autos.
     
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  2. 94045

    94045 Member

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    185 grain Golden Sabers impact lower than 230 grain Golden Sabers in my .45 Shield. I'm not going to get into the action type and muzzle flip argument.
     
    Last edited: Dec 12, 2019
  3. QED

    QED Member

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    JHPs in 124 gr. and 147 gr. offered by major manufacturers have very similar bullet momentum in the two bullet weights, but the 124 gr. JHPs have more than 10% greater kinetic energy. So if choosing from these offerings on the basis of momentum, 147 gr. hardly has an advantage over 124 gr.
     
  4. pblanc

    pblanc Member

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    Really depends on the load. The following muzzle velocities are taken from the Luckygunner ballistic tests, all standard pressure loads.

    Federal HST 124 grain 9 mm: muzzle velocity 1135 fps, momentum 20.1 lb-ft/sec, KE 354 ft lbs.
    Federal HST 147grain 9 mm: muzzle velocity 973 fps, momentum 20.4 lb-ft/sec, KE 309 ft lbs

    So in this case the gain in momentum is very modest with a gain of only 1.5% for the 147 grain over the 124 grain against a loss in KE of 13%.

    Speer Gold Dot 124 grain 9 mm: muzzle velocity 1067 fps, momentum 18.9 lb-ft/sec, KE 314 ft lbs.
    Speer Gold Dot 147 grain 9 mm: muzzle velocity 953 fps, momentum 20.0 lb-ft/sec, KE 297 ft lbs.

    Here we have a gain in momentum of 6% for the 147 grain in comparison with the 124 grain against a loss of 5% in KE.

    Differences in momentum and KE are often greater with FMJ ammunition, however.

    Speer Lawman 124 grain TMJ 9 mm: muzzle velocity 1090 fps, momentum 19.3 lb-ft/sec, KE 327 ft lbs.
    Speer Lawman 147 grain TMJ 9 mm: muzzle velocity 985 fps, momentum 20.6 lb-ft/sec, KE 317 ft lbs.

    Here we have a gain in momentum of 7% for 147 grain against a loss in KE of only 3%.
     
  5. pblanc

    pblanc Member

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    The fact of the matter is that when shooting projectiles with significantly different muzzle velocities out of what is essentially the same handgun, the faster projectile often shoots to a lower POI than the slower one. This is observed with both revolvers and pistols. The degree in shift of POI does seem to vary considerably with the handgun, but it is a commonly observed phenomenon. I have seen it. Others have seen it. And as I pointed out, manufacturers often change their sights on the same pistol to accommodate for this shift in POI.

    As for the high speed videos, I have seen them. It takes almost no visible barrel rise to create a significant shift in POI. A shift in POI at 25 yards would require an angular muzzle rise of only .066 degrees or .066 degrees of additional muzzle rise. I have seen no high speed video shot in such a way as to be able to detect this degree of muzzle deviation.
     
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  6. QED

    QED Member

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    Since the interest expressed was in choosing bullets with higher momentum in order to minimize bullet deviation in "denser" media, it was assumed that self-defense suitable JHPs, not FMJs, are relevant; the data I based my comment was from manufacturers' published data (standard pressure, if available). In particular, if one looks at Winchester's and Speer's offerings in 9mm, they offer 124 grain JHPs with equal or greater momentum and significantly more energy than their offerings in 147 grain JHPs.
     
  7. QED

    QED Member

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    If the slide (with significant inertia) is free to slide with low friction on the frame that is held by the shooter, what is your theory on how the moment or torque created by the accelerated bullet traveling down the barrel is transferred to the frame of the pistol held by the shooter?
     
  8. pblanc

    pblanc Member

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    It is not fee to slide. It is resisted by the force of the recoil spring.
     
  9. QED

    QED Member

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    And the spring action on the slide would account for magnitude of torque to be transferred to the frame of a pistol similarly to magnitude of torque transferred to a revolver when both are fired with similar loads? Hint: use Hooke's law to get the answer.
    Another hint: think slide inertia and Hooke's law and the time it takes a typical bullet to exit the barrel.
     
    Last edited: Dec 12, 2019
  10. Walt Sherrill

    Walt Sherrill Member

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    At what distance are your sights zeroed to when comparing the points of impact?

    According to Remington's ballistic chart below, both rounds should have the same point of impact at 25 yards given the ballistic data, shown below.

    Remington's chart shows that the heavier 230 grain bullet drops more at 50 yards than does the 185 grain bullet.. That means the bullet path of the .230 grain bullet has a higher (more pronounced) arc than the 185 gr. round, and should be hitting higher than the .230 round at closer distances than 25 yards. But at a distance LESS than 25 yards, the differences in the bullet paths/arcs are going to result in different points of impact, with the 230 gr. round hitting a bit higher.​

    That, in turn, suggests a higher point of impact for the .45 round if the POI is less than 25 yards. That's because the faster 185 gr round has a less pronounced/flatter arc, due to an arc which has a slightly greater radius.) You've got two bullet paths (arcs) that coincide only at one point. It might be that the 280 round is already starting down at that point, while the 185 gr. round has just hit's its peak.

    Golden-Saber-Bonded-Ballistics-Data.jpg
     
  11. pblanc

    pblanc Member

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    In the case of my SIG P229 it is not an issue of how the pistol is sighted. I have two P229 slides that accept either a 357 SIG or a 40S&W barrel. One has #8 sights front and rear which is what SIG commonly installs on P229 and P226 pistols chambered in either 9 mm Luger or 357 SIG. The other slide has a #6 front and a #8 rear sight, which is what SIG usually installs on P226 and P229 pistols chambered in 40 S&W, the #6 front sight being taller than the #8 front sight.

    I can shoot both 40 S&W and 357 SIG out essentially the same pistol with either slide. The only difference is a tiny difference in barrel weight between the two. With either slide and sight set, at any given distance of 25 yards or less, using exactly the same sight picture and hold on target, the 40 S&W will group at a higher POI than the 357 SIG. This occurs consistently with either slide. Many other owners of SIG P229 and P226 pistols have observed this change in POI when they put a 357 SIG barrel in their pistol that was initially chambered in 40 S&W and some will change sights as a result.

    I seldom shoot handguns past 25 yards, but as one gets out beyond that range, the faster speed and lessor drop over distance of the 357 SIG starts to cancel out the initially higher POI of the 40 S&W.
     
  12. QED

    QED Member

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    Actually, while the bullet is accelerated in the barrel, the recoil spring exerts hardly a significant recoil force on the slide; thus there is no significant torque exerted on the frame or the shooter holding the frame that would cause barrel rise -- until after the bullet has cleared the barrel.
     
    Last edited: Dec 12, 2019
  13. pblanc

    pblanc Member

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    Last edited: Dec 12, 2019
  14. QED

    QED Member

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    Let's get one "mechanical" issue settled first; do you agree that in SRLB semi-automatics, unlike revolvers, there is no significant barrel rise that would result in heavier bullets impacting higher? If not, again, what is your theory on how, possibly, any significant torque could be transferred to the frame or shooter while the bullet is accelerated in the barrel? Incidentally, I am far more easily persuaded by physics than anecdotes -- something that's obviously not universally shared.
     
    Last edited: Dec 12, 2019
  15. QED

    QED Member

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    That's correct, and since the spring is only compressed a tiny fraction of an inch before the bullet exits the barrel, by Hooke's law, the force exerted by the barely compressed spring is very small, meaning no significant torque is created to cause barrel rise -- for any practical purposes. Of course, even if the barrel is constrained to prevent any rise, bullet impact (same type, velocity and weight) will differ somewhat, shot to shot. An entirely different situation exists with revolvers, of course, whereby a significant torque is generated on the revolver and shooter's hand immediately as the bullet accelerates from rest.
     
  16. film495

    film495 Member

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    to the OP. in 9mm both weights as ball ammo will just be through and throughs. The balance, they try to make is with hollow point ammo - a slightly lighter bullet weight, will get going faster - and be more likely to expand than one going slower. So, from my limited experience - you'll see hollow points slightly lower weight than ball practice ammo. They are actually trying to limit penetration with the hollow point and lighter bullet - to put maximum nrg into the target - and not have half the nrg just go out the back of the target. Then again, if you're law enforcement - and shooting at someone in a car or behind a door, that extra penetration might come in handy.
     
  17. film495

    film495 Member

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    duplicate
     
    Last edited: Dec 12, 2019
  18. film495

    film495 Member

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    duplicate
     
  19. Walt Sherrill

    Walt Sherrill Member

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    With the slide that comes with the .357 SIG version of the P226, the front sight is DIFFERENT than the sight on the .slide that comes with the .40 version of the gun. (I'll agree that the only difference is the rollmark on the slide and the front sights.) According to SIG, the 9mm and .357 SIG slides use the same sights (#8 front and #8 rear.) The .40 slide uses a #6 front and a #8 rear.

    One of the experts on the SIG forum provided this explanation: A #6 front sight sight is taller than a #8 front sight. You can do the calculation yourself.
    _______________________________________________
    Front sight number down is taller and lowers POI
    Front sight number down equals -1" POI at 25 yards

    Front sight number up is shorter and raises POI
    Front sight number up equals +1" POI at 25 yards
    _______________________________________________

    Rear sight number down is shorter and lowers POI
    Rear sight number up is taller and raises POI

    Rear sight number down equals -2" POI at 25 yards
    Rear sight number up equals +2" POI at 25 yards
    _______________________________________________

    Thhis chart would suggest that if you're shooting a .357 SIG round in a .40 slide (which has an #6 front and #8 rear,) the taller front sight should lower the point of impact for the .357 round by about 2" due to the TALLER.40 front sight. Likewise, shooting the the .40 round in the .357 slide (which has a #8 Front and and #8 rear) the .40 round should hit about 2" higher than the .357 round.

    You wrote:

    "With either slide and sight set, at any given distance of 25 yards or less, using exactly the same sight picture and hold on target, the 40 S&W will group at a higher POI than the 357 SIG." ​

    There's always going to be a difference between the .357 SIG and .40 S&W points of impact, using the same aiming point and sight picture, in the same slide.

    But, where the rounds from either slide (with different sights) actually group on the targets should be different when comparing the groups from one slide to the other. The sights are different!

    You might see the differences I'm talking about -- caused by the different sights -- if you shoot
    four or five rounds from the .357 SIG slide, and then shoot four or five rounds from the .40, using either the 40 barrel or the .357 SIG barrel. You should see a difference. (Two targets side by side might make it easier to see.) Since both rounds are suppose to match POA/POI at 25 yards, you may have to ame at something closer or farther away to really see much difference.

    And, unhappily, if you shoot like I do, my inconsistency from one shot to the next often offsets any of the possible differences either of us might otherwise see.. :)
     
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  20. pblanc

    pblanc Member

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    Walt, you are not listening to what I am saying. And I am fully familiar with SIG sight numbers, sight heights and what sights they usually install on 40 S&W and 357 SIG models of the P229 and P226.

    One more time, here is what I am saying. I can take either of my SIG P229 slides, either the one with the 6/8 sight set or the one with the 8/8 sight set and shoot both 40 S&W or 357 SIG through either depending on which barrel I put in. Everything else is the same, including recoil spring assembly.

    So lets say I have the 6/8 slide mounted on the frame and shoot a group of 40 S&W at a bullseye at say 15 yards using whatever sight picture you like, combat, six o'clock, or split the bull with the top of the front sight post, making no adjustment in sight picture between slow fire, aimed shots.

    Now I take the same pistol with the same slide and sights and put the 357 SIG barrel in and shoot a group at the same target at the same range using exactly the same sight picture. The 357 group center will be roughly an inch below the 40 S&W center. And the 357 group will center consistently below the 40 caliber group.

    Now I put the other slide with the 8/8 sights on the same pistol and repeat the above process using first the 40 S&W barrel then the 357 SIG barrel and again shoot two groups using the same sight picture as before for both. Of course, both of these groups will now center higher than the first two groups because of the shorter #8 front sight. But the 40 S&W group center will once again be higher then the 357 SIG group, consistently so.

    This phenomenon has been consistently observed by those who put 357 SIG barrels in SIG P22x pistols chambered in 40 S&W or vice verse. I don't have Glocks chambered in either 357 SIG or 40 S&W but I have heard Glock owners say the same thing after a 40 S&W/357 SIG barrel swap in the same pistol. And it has been reported on this forum, the Glock forum, both SIG forums, Brian Enos' forum, and others so the phenomenon is real, at least with some auto-loading pistols. And I previously mentioned the significant shift in POI I saw in a Kahr 9 mm auto-loader resulting only from changing from 124 grain to 115 grain FMJ.

    Many SIG P22x owners of 40 S&W pistols with 6/8 sight sets who decide to convert to 357 SIG with a barrel swap will go ahead and change the front sight to a shorter #8. I actually prefer the 8/8 sights for 40 S&W since it allows me to use a top of front post POA rather than the cover the bull with the front sight that is usually necessary for the 6/8 sights. The combat type sight picture is still required when shooting 357 SIG with 8/8 sights. In this old thread from Brian Enos forum, JonInWaA basically says the same in the third post:

    https://forums.brianenos.com/topic/92287-difference-between-6-and-8-front-sight/

    Do you have any explanation other than projectile velocity why 357 SIG should consistently shoot to a lower POI at short to intermediate ranges than 40 S&W when both are shot from what is essentially an identical pistol? And do you have any explanation, other than a shift in barrel orientation, why the faster projectile should consistently hit at a lower POI at these ranges?
     
    Last edited: Dec 13, 2019
  21. tipoc

    tipoc Member

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    Well, bullet weight. In regards to the above.
     
  22. pblanc

    pblanc Member

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    Yes, bullet weight but how? Bullet drop due to gravity over time is independent of bullet mass but the 357 SIG having significantly greater muzzle velocity than 40 S&W would be expected to drop less over any given distance. Both projectiles will travel 15 yards pretty quickly so the difference in drop between the two would be expected to be pretty small. But whatever that difference was, the POI of the faster projectile would be expected to be higher than the slower.

    In this case, at least insofar as the SIG P22x pistols are concerned, when 357 SIG and 40 S&W are shot from the same gun (except for the barrel) the opposite is true. The slower projectile has a higher POI, everything else being equal. Since the lock time and all mechanical aspects of the hammer, hammer spring, firing pin, etc. are identical, if any consistent shift in barrel orientation occurred during the pre-ignition phase after the sear released the hammer, it would be expected to be identical for both cartridges. So it seems to me that the shift in POI can only be explained by a difference in shift of bore axis during the interior ballistic phase. And if that is not recoil induced, I would like to hear a plausible alternative explanation.
     
  23. Walt Sherrill

    Walt Sherrill Member

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    pblanc:

    I understood what you said -- but I'm not sure you understood what I was saying.

    I can see how the bullets might group similarly (the .40 higher and the .357SIG lower) regardless of the slide used -- given the different arcs of the bullet paths and the distance to the target. Move the targets out a bit farther and I'd expect ot see the bullets despite their different weight and speed hitting at the same point, and if moved farther still, to see the .40 round hit lower than the .357 SIG.

    But I don't see how the two sets of groups for each barrel in either slide can end up on the target in the same relative positions given the same aiming point, given the different sights on the two slides.

    For whatever distance you've set your targets, I'd expect the DIFFERENCES between.40 and .357Sig points of impact to be the same for each slide, no matter which slide was used, but I can't understand why -- if two targets were lined up side by side, and one slide was used one target and the slide was used on the target, and you were aiming at the same point on the evenly mounted targets, why the two groups would hit on the same points on the targets. You're telling me that the sights don't make a difference in where the bullets hit the target.

    Everything else IS the same. (The bore axis for each barrel won't have changed when you change slides, so I don't see how that will affect impact. Where the bullets actually impact the target has to do with distance, given the different bullet paths.

    I hope someone can explain it.
     
    Last edited: Dec 16, 2019
  24. pblanc

    pblanc Member

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    No, I did not say that the two groups with either barrel/caliber will impact at the same POI given the same hold at the same range with either set of sights, although perhaps that is how it sounded. Yes, the vertical difference in group centers will be the same for both sight sets between the two calibers at any given range. The sight numbers will determine where the groups center on the target.

    And you are correct in that at longer ranges, the lesser drop over distance due to gravity of the faster 357 SIG cartridge will start to cancel out the initially higher POI of the 40 S&W round. I am not a good enough shot offhand to get good enough groups at 25 yards to demonstrate this, but if I shoot from a bench with support at 25 yards the difference in POI between the two is no greater than at 12-15 yards, and perhaps a little less.

    As I said before, this issue comes up all the time on sig forums and indeed here is a thread started just yesterday that discusses the higher POI of the slower 40 S&W cartridge when swapping barrels in the SIG P22x:

    https://sigtalk.com/sig-sauer-pistols/367314-elevation-difference-between-40-357-sig-my-p229.html

    You can see bumper's explanation for this phenomenon. I don't know if he is correct or not, but bumper is far and away one of then most experienced regulars on that forum.

    Assuming that one uses the same sight alignment and good trigger control and given that the lock mechanism and all aspects of the pistol apart from the barrel are identical, I think one can assume that the orientation of the barrel will be the same for both cartridges at ignition. So unless the bore on either the 40 S&W or 357 SIG barrels or both are bored off-axis in a very consistent fashion, then the shift in POI can only occur during the interior ballistic phase. To my mind, that can only result from a change in barrel orientation during the primary ballistic phase and there has to be a mechanism for that.
     
    Last edited: Dec 17, 2019
  25. Walt Sherrill

    Walt Sherrill Member

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    I don't think bore axis has anything to do with it... The mechanism you seek is the different sights on the two slides and the different bullet trajectories of the two loads being used (weight and velocity.). This is addressed again, below.

    As for bore axis:

    The term bore axis refers to the relationship between the barrel of the handgun and the shooter’s hand — a ‘high’ bore axis means that the barrel is positioned well above the top of the hand and ‘low’ bore axis means that it’s closer. (The definition just cited, and the following image, are from a site called The Truth About Guns )

    [​IMG]

    I don't see how bore axis can have anything to do with the different points of impact, as the bore axis is exactly the same for both barrels in either slide -- the center line of either bore will be the same distance from the shooter's hand.

    The only differences in those two slides, regardless of the barrel used, is sight height, which raises the front of the slide and barrel (which is the equivalent of bore axis for this discussion) or lowers it. There is a dramatic differencein the rounds fired (i.e., weight and velocity) and those rounds have quite different bullet paths.

    Depending on the barrel used and the distance to the target, the point of impact might be the same if both guns are using sights appropriate for the caliber at 25 yards. But if both barrels and loads are shot from the same slide, the points of impact will be different even though the bore axis is the same.

    With the Browning Short Recoil Locked Breech design, the bullet is gone from the gun before the slide and barrel have moved only a small fraction of an inch, This is true even though one load might be hotter than the other. Regardless of the load, only a small amount of recoil force will be transferred to the frame until AFTER the bullet is gone.​

    That means,in turn, that the bore axis (i.e., barrel) of a Browning SRLB gun can't be much affected by recoil-induced barrel rise until after the bullet is gone. The point of impact is only trivially affected by barrel rise. After the bullet is gone, the rest of the recoil force is passed to the frame and THEN the amount of gun movement due to recoil can be greatly different depending on the loads used.
     
    Last edited: Dec 17, 2019
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