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Thread: What Causes Sideways Muzzle Jump During Recoil?

  1. #1
    Join Date
    Sep 2009
    Location
    Atlanta
    Posts
    836

    What Causes Sideways Muzzle Jump During Recoil?

    My shooting buddy has a Savage (with the target Accu-Trigger, which has a fairly-light pull) .223 with a 7-twist barrel and a three-inch wide flat forearm that he shoots free-recoil. When he shoots 80 gr bullets (off of a front rest that has “dog ears” on both sides of the forearm pad and weighs about 17 lbs.) the muzzle “jumps” WAY off the target to the right during recoil; however, when he shoots the same gun with a 9-twist barrel and a 53 grain bullet the muzzle doesn’t “jump” to the right near as much.

    He also has a Savage (with the target Accu-Trigger) 6BR with a 12-twist barrel and a three-inch wide flat forearm that he shoots free-recoil, and when he shoots 70 gr bullets (off of a front rest that has "dog ears" on both sides of the forearm pad and weighs over 30 lbs.) the muzzle also “jumps” to the right – but not as much as the aforementioned 7-twist .223.

    All three barrels are right twist and he makes an effort to be sure his rear bag is properly aligned with the front rest.

    He thinks the torque imparted by the bullet’s rotation is what causes the “jump” – and I think I’ve read several places that suggest he’s correct. However, I don’t understand that theory so I asked someone who I thought might understand the matter (and he confirmed that he did understand it); his answer was that the torque was not the cause of the “jump” – but he didn’t say what was the cause; nor do I recall that he give a reason for his statement.

    The reason I don’t understand the torque theory related to the muzzle moving sideways on recoil is because it seems to me that any torque imparted from a right spinning bullet (as viewed from the chamber and focusing on the 12:00 position on the bullet) would be offset by the fact that the bullet is also rotating LEFT (as viewed from the chamber and focusing on the 6:00 position on the bullet); thus, it seems to me that the two rotations would cancel out the effect of the other rotation.

    Can someone shed some understanding on:

    a. what causes the muzzle “jump” described above;
    b. if it is torque from the bullet’s rotation, please explain why the “left-rotation” (as mentioned in my fifth paragraph above) does not off-set the right-rotation; and
    c. would your answers be different if the gun was a custom gun?

  2. #2
    Join Date
    Jan 2017
    Location
    Australia
    Posts
    35
    I had something similar happen with my PPC, when i fired it i had to use the coarse adjustments on my rest to bring it back on target. I solved it by moving the rifle bump stop on the rest, rearwards. So there was not much of the stock over hanging the front bag. Try moving the bump stop forward or backward to see what works best for you.

  3. #3
    Join Date
    Feb 2012
    Location
    Indian River, MI
    Posts
    52

    Muzzel jump (recoil)

    About 15 years ago my late friend, Paul Brown, a college mathematics and physics professor, machinist and benchrest shooter, wrote an article in Varmint Hunter about "straight line recoil". His explanations and diagrams showed how it could be achieved. Most guns recoil upwards because more of the mass is below the bore. He showed a perfectly" balanced" rifle by running a strong fish line down the muzzle and through an empty cartridge case. Closing the bolt and hanging the gun showed the unbalanced gun until he started adding weight above the bore. When the gun hung perfectly vertical, it should recoil straight back. I will locate the magazine article and see if my memory and explanation agree.

  4. #4
    Join Date
    Aug 2013
    Posts
    28
    Centerline of bore out of alignment with stock, particularly the bottom rear of stock that rides the rear bag can cause tracking problems.

  5. #5
    Join Date
    Feb 2003
    Posts
    10
    Quote Originally Posted by zimmden View Post
    About 15 years ago my late friend, Paul Brown, a college mathematics and physics professor, machinist and benchrest shooter, wrote an article in Varmint Hunter about "straight line recoil". His explanations and diagrams showed how it could be achieved. Most guns recoil upwards because more of the mass is below the bore. He showed a perfectly" balanced" rifle by running a strong fish line down the muzzle and through an empty cartridge case. Closing the bolt and hanging the gun showed the unbalanced gun until he started adding weight above the bore. When the gun hung perfectly vertical, it should recoil straight back. I will locate the magazine article and see if my memory and explanation agree.
    PM inbound. I would really like more info regarding this.
    Pat

  6. #6
    Join Date
    Apr 2012
    Location
    Waynesville. NC
    Posts
    590
    When it’s out of tune it will recoil all sorts of different ways.
    Only when they are in tune do they come straight back nice and smooth
    My experience anyway which isn’t a whole lot

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