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10mm / 40 S&W pressure difference

Discussion in 'Caliber Corner' started by greenlion, Oct 1, 2010.

  1. greenlion

    greenlion

    944
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    Jul 25, 2009
    North Carolina
    A while back I made a comment on someone else's post stating that I thought the 10mm had less felt recoil than the .40 S&W, given the same bullet weight and velocity. Everyone seemed to chalk it up to the extra size and weight of the GLOCK 20sf. At the time, I stated that I thought the pressures would also be less in the downloaded 10mm because of the increased case capacity. Everyone seemed to disagree with that idea.

    However, I was just comparing the .40 and 10mm load data on the Hodgdon reloading website, and there is indeed as much as a 5,000 psi pressure difference between the .40 and 10mm given the same bullet at the same velocity.

    Example:
    .40 S&W 155gr Hornady XTP @ 1030 fps = 28,100 psi
    10mm 155gr Hornady XTP @ 1030 fps = 23,000 psi

    I don't see how this could not effect felt recoil.
     
  2. Chamber pressure doesn't relate to recoil.

    Bullet weight, bullet velocity, firearm weight and powder weight are all I need to determine recoil using RCBS software.

    Here's some recoil comparisons I've posted in the past with some powder manipulation;

    Colt 1911 Gov't;

    Now compare an upper end 10mm load from a G20;

    Now the numbers from a 6" M686 that approximates bullet weight and velocity;

    My Steyr M40-A1 has less muzzle flip than a G22 shooting the same ammo, probably because of its ergonomics.

    A high chamber pressure .40 S&W 165gr Gold Dot load ballparking the above 10mm chamber pressure;

    Steyr M40-A1, 4" with fully supported chamber, do not use this load in a Glock/unsupported barrel. This is a very stout load using Vihtavuori #4 manual data;

    Even though both the .40S&W and 10mm were loaded near their upper pressure limits, the 10mm recoils more due to its faster MV and increased powder weight.

    Now we can take this data one step further, while I don't know the powder weights/type used in Double Tap ammo; here's DT's ballistic gel data with 4-layers of denim that ballparks the above data used to determine recoil;

    Hopefully this will give you some added insight into the recoil/bullet performance relationships.

    Bob :cowboy:
     

    Last edited: Oct 2, 2010

  3. fredj338

    fredj338

    21,685
    912
    Dec 22, 2004
    so.cal.
    In your example, the recoil impulse would be indetical in identical guns. The issue, most 10mm are heavier than 40s. The only diff possible, what powder was used in each to get that vel.:dunno: I could easily build a load that KBs a 40 w/ less powder & less vel than the 10mm. Maybe a dbl. charge of TG & 180gr bullet, maybe 50Kpsi @ 1100fps? POW!
     
    Last edited: Oct 2, 2010
  4. greenlion

    greenlion

    944
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    Jul 25, 2009
    North Carolina
    Glolt20, I understand that there will be recoil differences between different bullet weights and velocities. That much is obvious. I was comparing apples to apples, with the only variable being pressure.

    I guess I do see what you guys are saying. While the higher pressure is more wearing on the gun, it does not factor into the physics of the recoil impulse. In the world of felt experience though, it seems like SUCH a different (snappy) impulse from a .40 than it does a in a downloaded 10mm, that it doesn't seem like it could just be the slight increase in gun size causing it.
     
  5. I understand, just trying to share raw data from loads I've personally chronographed and ran recoil software on.

    Here's some data from testing I did years ago and posted on GT, G20 (28oz) and a Steyr M40-A1 (27oz) heads up with 155gr Gold Dots. This is as close as I can get comparing 10mm and .40S&W pistol weights, the Steyr is very robust in its construction.

    G20, 12.0grs Blue Dot at 1242fps
    Recoil:
    11.21ft/lbs, 20.3fps (15.69fps bullet - 4.60fps powder)

    Steyr M40-A1, 7.8grs Unique at 1279fps
    Recoil:
    10.47ft/lbs, 19.98fps (16.81fps bullet - 3.18fps powder)

    Both of these loads operate at upper level SAAMI pressures according to Speer - 37,500psi 10mm (12.0gr Blue Dot) and 35,000psi .40S&W (8.0gr Unique)

    Both of these loads were chronographed on the same day and is as close as I can get heads up to your requirements.

    In this particular test, the .40 Gold Dot achieved faster velocity from a shorter barrel, with less recoil and assuming less chamber pressure.

    The Steyr can put up some very fast split times compared to the G20.

    Bob :cowboy:
     
    Last edited: Oct 2, 2010
  6. fredj338

    fredj338

    21,685
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    Dec 22, 2004
    so.cal.
    Every ounce of gun wt in a handgun significantly reduces recoil impulse. The same ammo in a 4oz heavier gun is just gonna shoot softer, there is no way around that. The converse is true. Stuff 155gr 40s in a G27 & then into a G20 w/ after market bbl. The recoil impulse diff is dramatic.
     
    Last edited: Oct 2, 2010
  7. cowboy1964

    cowboy1964

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    Doesn't lower pressure "spread out" the impulse, resulting in a perception of lower overall recoil/flip/torque? The 45 ACP is the prime example.
     
  8. fredj338

    fredj338

    21,685
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    Dec 22, 2004
    so.cal.
    Slightly, very slighty, most would never know it. Run a 185gr 45acp @ 1150fps, feels just like a 10mm w/ 180gr @ 1200fps w/ 10K less pressure.:dunno:
     
    Last edited: Oct 2, 2010
  9. If I was able to get the .40S&W/155gr GD velocity out of a 21oz G23; recoil jumps to ~13.5 ft/lbs, significantly higher than the G20 or Steyr.

    Bob :cowboy:
     
  10. English

    English

    4,585
    42
    Dec 24, 2005
    London
    You were quite correct that the 10mm will have a lower quoted pressure to achieve the same velocity as a .40S&W. You are also correct that the reason for this is the extra space in the 10mm case.

    The important thing you are missing is that the quoted pressure is the peak pressure. That occurs quite soon after the bullet leaves the chamber when the space behind the bullet is low. As the bullet gets further down the barrel the space in the cartridge becomes less important as it becomes a smaller proportion of the whole.

    The 10mm gets to the same velocity because the pressure down much of the rest of the barrel is higher, but this can happen only if the 10mm has more propellant. It can carry more propellant safely because of that extra space in the case but the cost is that the bullet does not get that initial high acceleration of the smaller case .40S&W with a lower charge. Rifle shooter talk of efficient cartridges that use less powder to get the same velocity but, as with the 10mm and 40S&W, they are talking of less than maximum loads in the less efficient cartridge.

    The knock on effect of this is that for such loads the 10mm will have more recoil because a greater mass of gas is jetting out of the muzzle at an average speed around 2,500 or 3,000 fps.

    Especially for an auto pistol, the pressures at different points along the bullets position in the barrel don't make any difference to the recoil. All you need conceren yourself with is the bullet mass and velocity and the powder mass. That gives you the total ejecta momentum and hence the total gun momentum.

    The reason you feel that the .40S&W kicks so much harder is because it is a lighter pistol and felt recoil is not a linear matter. That is, 10% more recoil velocity can feel like a lot more than 10% more recoil. In this case the G22 is 25.67oz with magazine and the G20 is 30.32oz or 18.1% more. So the recoil velocity of the G20 would be about 15.3% less for the same ejecta momentum. As we have seen, that is not equivalent to the bullet momentum so the real figure would be a little less - say about 13% instead of 15.3%. That 13% can take you over the edge from comfortable to uncomfortable.

    English
     
  11. greenlion

    greenlion

    944
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    Jul 25, 2009
    North Carolina
    This is what I'm talking about. That is what it feels like. A completely different impulse.

    I've shot .40 out of a 22, 23, and 27 and I know there is a bit of difference between those models due to weight and length of barrel, but this is different. All those still feel like you are shooting the snappy little .40 round. The downloaded 10mm feels like a different, more pleasant round to shoot.
     
  12. Let's run the numbers and see. I went back in my reload notes 5 years and came up with some upper end .45/185gr and 10mm/180gr pressure loads at the same MV.

    Keep in mind that the .45auto casing will hold about 3.0 grains more water than the 10mm case.

    I'm going to ballpark ~21,000-23,000psi for the .45auto and between 30,000-35,000psi for the 10mm. I used a faster burning powder in the 10mm in order to achieve a relatively low MV at high pressure.

    While MVs are nearly identical, the extreme spread of the .45auto is slightly more.

    Let's assume a 10mm barrel in a G21 to keep the weight also constant.

    Data:
    M1991 Colt Lew Horton combat/target, 5" barrel, 185gr Golden Saber, 8.2grs Unique, this is max powder weight from Speer;

    1126fps, ES 58fps, SD 20fps.

    Glock 20, 4.6", 180gr Sierra JHP, 6.3grs Universal Clays, 6.4grs is max powder weight from Sierra V;

    1122fps, ES 37fps, SD 11fps.

    Doesn't matter if the Glock weight is 28oz or 38oz, the low pressure .45auto will have slightly more recoil because it needs more powder to launch a bullet to the same MV.

    Clearly, chamber pressure is not relevant to recoil in this comparison.

    Arbitrarily picking 30oz pistol weight.

    .45/185 Recoil;
    10.29ft/lbs, 18.79fps (15.93fps bullet - 2.86fps powder)

    10mm/180gr recoil;
    8.94ft/lbs, 17.51fps (15.36fps bullet - 2.15fps powder)

    Bob :cowboy:
     
    Last edited: Oct 2, 2010
  13. English

    English

    4,585
    42
    Dec 24, 2005
    London
    The pressure variations in the barrel all happen before the barrel has unlocked from the slide and so the changes in momentum happen only against the resistance of the recoil spring during the very first part of its compression. As a result you cannot feel these variations and only feel the toatal recoil momentum as recoil spring compression and the impacts of the barrel on the locking block and the slide hitting the frame at the end of its travel. The perceived snappiness of the .40 is entirely a matter of the light weight of the pistol and the relatively light weight of the slide relative to the slides of the .45ACP, 10mm and .45GAP pistols.

    English
     
  14. cowboy1964

    cowboy1964

    19,696
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    U.S.A.
    A Glock 36 weighs almost exactly the same as a Glock 27. I bet most people would say the 27 has more "snap" though the 36 may have more overall recoil.