Page 1 of 2 12 LastLast
Results 1 to 20 of 23

Thread: change in point of impact

  1. #1
    Member GreenTea's Avatar
    Join Date
    Apr 2008
    Location
    Palmer, Alaska
    Posts
    92

    Default change in point of impact

    I've got a S&W 329PD .44, 4" barrel, weighs 25 ounces.
    I sighted in with Blazers, 44 Specials, 200 gr JHP, at 15 yards, but when I switched to HSM 44 magnum, 300 gr, hard cast lead, the point of impact moved 5 inches higher.
    Both loads are grouping very well (1.5"), but I can't understand why the point of impact would change so dramatically over such a short range.
    Any explanations?

  2. #2
    New member
    Join Date
    Oct 2005
    Posts
    5,417

    Default

    Heavier bullet + different velocity = different trajectory. Just screw your rear sight down.

  3. #3
    Member gunbugs's Avatar
    Join Date
    Jul 2007
    Location
    Fairbanks
    Posts
    1,382

    Default

    With a lightweight pistol like that, the velocity of recoil is going to be substantially different with different bullet weights. The muzzle will be at a different point in recoil accounting for the point of impact . Plus its probably shooting low and left, and you've got the sight adjusted up and to the right.
    "A strong body makes the mind strong. As to the species of exercises, I advise the gun. While this gives moderate exercise to the body, it gives boldness, enterprise, and independence to the mind."

  4. #4
    Member
    Join Date
    Apr 2006
    Location
    SwampView AK, Overlooking Mt. Mckinley and Points Beyond.
    Posts
    8,808

    Default

    gunbugs:

    Doesn't barrel length, effect the POI too, for the same reason?

    I never could pin down what to expect when changing bullet weight, barrel length, or just weight, but I understand it all has an effect, because of the way a handgun recoils.

    Thanks
    Smitty of the North
    Walk Slow, and Drink a Lotta Water.
    Has it ever occurred to you, that Nothing ever occurs to God? Adrien Rodgers.
    You can't out-give God.

  5. #5
    Member gunbugs's Avatar
    Join Date
    Jul 2007
    Location
    Fairbanks
    Posts
    1,382

    Default

    I don't know the math well enough to give a good answer, but my experience with large bore, short barrel revolvers has certainly led me to understand that the shorter the barrel, the more susceptable to bullet weight/velocity variations they are. And also more affected by variables in how tight/loose your grip is.
    "A strong body makes the mind strong. As to the species of exercises, I advise the gun. While this gives moderate exercise to the body, it gives boldness, enterprise, and independence to the mind."

  6. #6
    Member GreenTea's Avatar
    Join Date
    Apr 2008
    Location
    Palmer, Alaska
    Posts
    92

    Default

    I realize that the different bullet weights/velocities will affect trajectory, but I didn't think it would be so dramatic at such a short range. I wouldn't have expected to see a 5" difference at 15 yards.
    There was also a suspicion that the heavier recoil from the magnums was tilting the barrel slightly upwards, which would certainly account for the change in point of impact, but hasn't the bullet already cleared the barrel before recoil moves the sights off target?
    The gun was originally shooting high and right, but it's printing perfectly centered with the Specials now (at 15 yards), and the magnums show no horizontal deviation, just 5" high.

  7. #7

    Default

    I assume YOU bought the gun for you to carry as a backup or a fishing protection type firearm. AS SUCH the use of 44 Special ammo in this gun is pretty much a waste UNLESS you decide to let the wife carry it as well.
    While target style 44 magnums are capable of very good accuracy, with magnum ammo, people soon tire of the recoal and noise and they loose the bulk of the guns desired capabilities; a miss doesn't kill anything.
    As per your question, recoil begins the instant the bullet slides the first thousandth of an inch in the case towards the muzzle and continues builing until the force required to move the projectile AND burn the powder in the cylinder and barrel have left the gun. Once the powder has left the gun it may still burn but only contributes to muzzle flash and noise not recoil but may cause the shooter discomfort and reduce the shooters ability to maintain accuracy.
    " Americans will never need the 2nd Amendment, until the government tries to take it away."

    On the road of life..... Pot holes keep things interesting !

  8. #8
    Member
    Join Date
    Apr 2006
    Location
    SwampView AK, Overlooking Mt. Mckinley and Points Beyond.
    Posts
    8,808

    Default

    Thanks gunbugs:

    I'll keep that in mind.

    I've not had to worry about which load I'm using. My 44 with 6" barrel seems to shoot most everything pretty close to the same place.

    All over the place. (Just kiddin.)

    Really, both my BAR Loads, and various other loads land close together, leastways the way I shoot'em.

    Smitty of the North
    Walk Slow, and Drink a Lotta Water.
    Has it ever occurred to you, that Nothing ever occurs to God? Adrien Rodgers.
    You can't out-give God.

  9. #9
    Member Ryan J's Avatar
    Join Date
    Feb 2010
    Location
    Anchorage
    Posts
    218

    Default

    I was out shooting last week and had the same issue. I was shooting my Redhawk .44 mag with 5.5" barrel. I had gotten a couple of boxes of the HSM (same stuff you had it looks like) 300gr. because the price is right. When I switched to them my point of impact moved to the top of the 8" circle target, so about 4" high. This was at 25yrds, the groups were tight but I had to screw the rear sight down as far as it would go to hit center with that ammo. I didn't have any other brand left at that point to switch back to see if it was the ammo or some other issue that affected the trajectory.
    It's been a while since I've shot that revolver, but in the summer my 240gr Remington and my 340gr. Alaska Backpacker were not that different POI. It makes me wonder about the HSM ammo.
    Last edited by Ryan J; 01-11-2011 at 13:13. Reason: add info

  10. #10
    Member GreenTea's Avatar
    Join Date
    Apr 2008
    Location
    Palmer, Alaska
    Posts
    92

    Default

    Ryan, I think you may be right about the HSM ammo. It's been fairly easy to predict change in point of impact for rifle cartridges of differing weights/velocities, but this is the first time I've seen such a jump in a handgun cartridge.
    I tried to find ballistic info on the HSM cartridges, but their website doesn't offer any.

  11. #11
    Member
    Join Date
    Apr 2006
    Location
    SwampView AK, Overlooking Mt. Mckinley and Points Beyond.
    Posts
    8,808

    Default

    It matters how you hold the gun when you're shooting from a rest, to test loads.

    If the barrel is against the rest, that can cause you to shoot high.

    I'm not sure what is the best way to hold against a rest.

    Smitty of the North
    Walk Slow, and Drink a Lotta Water.
    Has it ever occurred to you, that Nothing ever occurs to God? Adrien Rodgers.
    You can't out-give God.

  12. #12
    Member Ryan J's Avatar
    Join Date
    Feb 2010
    Location
    Anchorage
    Posts
    218

    Default

    I was resting my non-firing hand wrist on my shooting sticks, the handgun was not in contact. Don't know if that makes a difference? Good point though.

  13. #13
    Member gunbugs's Avatar
    Join Date
    Jul 2007
    Location
    Fairbanks
    Posts
    1,382

    Default

    Loose grip, shoots high. Tight grip, shoots lower. Death grip, shoots low left.
    "A strong body makes the mind strong. As to the species of exercises, I advise the gun. While this gives moderate exercise to the body, it gives boldness, enterprise, and independence to the mind."

  14. #14
    Member GreenTea's Avatar
    Join Date
    Apr 2008
    Location
    Palmer, Alaska
    Posts
    92

    Default

    It definitely wasn't a matter of improper grip, in that case, and I wasn't using a rest either.

    A shooter with a great deal of experience and education believes it's due to "TIB" - time in bore. This is a function of a heavy bullet in a light gun taking longer to travel the length of the barrel, and the recoil lifting the muzzle, causing the heavier bullet to shoot high. The lighter bullet speeds through the barrel faster, leaving the bore before recoil moves the muzzle too far up.
    He points out that a lot of big bore revolvers have a relatively high front sight to compensate for this.

  15. #15
    New member
    Join Date
    Oct 2005
    Posts
    5,417

    Default

    Heavy boolits require higher front sights...usually... If you handload you can tweek your loads to have the same POI... depending....

    I shoot a 355gr at 1150 fps in my 4" 45 Colt Redhawk with factory sights. It shoots 5-6 inches high at 25yds with the rear sight screwed down all the way, it needs a taller front sight with this load, or more velocity, but then I'd be over max load/pressure. 255gr at the same velocity I have to raise the rear sight 12 clicks to be on the bullseye. I can sight it in where ever I want.

    But, the same 355gr boolit in the same Redhawk driven to a higher velocity is right on or only about an inch high at 25yds. I recently put a 454 Cylinder in the gun and loaded up some 454 rounds. The difference in the loads is the amount of powder and primer. 21.5 gr for the 45 Colt load, 24gr for the 454 load. I didn't chrony the load but the book says it's supposed to be 1447.

    Maybe Professor Murphy will visit us and explain the physics behind it all. TIB, trajectory, barrel length, recoil, etc.

  16. #16

    Default

    Quote Originally Posted by gunbugs View Post
    Loose grip, shoots high. Tight grip, shoots lower. Death grip, shoots low left.
    this would be me shooting my G29 (10mm sub-compact) w/DT 230g hardcast. Other lighter loads are much easier to control so I don`t clamp down like my life depends on it.


    Heavy Hitter Fishing
    https://www.facebook.com/pages/Heavy...54441957966186

    Kodiak Custom Fishing Tackle Pro-Staff


  17. #17

    Default

    It is physics. It will shoot different if you do ANYTHING DIFFERENT! If load it with different ammo, if you hold the gun different, but one thing is for certain, find a load you like and be consitent with every thing involved in your shooting style, and it will always hit in the same place. Any handgun is like shooting a bow, if you want to be efficient with it you must be consistant, that means your ammo too. Just like a bow, the heavier it is the more forgiving it is, meaning little things won't make big differences. so the shorter and lighter it is the less forgiving, meaning it will amplify your differences, and changes from shot to shot. This is why I love hunting and competeing with the revolver!!

  18. #18
    Member S.B.'s Avatar
    Join Date
    Oct 2008
    Location
    Central Illinois
    Posts
    680

    Default

    Velocity! Big difference in how fast the magnums are going compared to your specials.
    Steve

  19. #19
    Member
    Join Date
    Jan 2007
    Location
    welfare state of Alaska
    Posts
    5,153

    Default

    In a large caliber the gun starts to recoil as the bullet is being accelerated and the gun is in recoil with some muzzle elevation before the bullet leaves the barrel. With heavier loads the muzzle is elevated more both from the recoil and longer period to get the slower heavier bullet out of the barrel therefore a higher point of impact at closer ranges. At some point with a heavier loadyou are going to get the bullet out of barrel faster and should get a lower point of impact like a lighter faster bullet.

    Grip, weight of the gun and barrel length i.e. inertia all have some effects on the muzzle rise. Powder burnt rate and other things can affect the barrel rise also but more difficult to sort out.
    Living the urban lifestyle so I can pay my way and for my family's needs, and support my country. And you?
    ".. ask not what your country can do for you, ask what you can do for your country" JFK

  20. #20
    Member
    Join Date
    Apr 2006
    Location
    SwampView AK, Overlooking Mt. Mckinley and Points Beyond.
    Posts
    8,808

    Default

    Quote Originally Posted by gunbugs View Post
    Loose grip, shoots high. Tight grip, shoots lower. Death grip, shoots low left.
    Thank Yew, again Mister gunbugs:

    I'd be stealin all your stuff, if I had the time.
    Walk Slow, and Drink a Lotta Water.
    Has it ever occurred to you, that Nothing ever occurs to God? Adrien Rodgers.
    You can't out-give God.

Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •