Does recoil begin before the bullet exits the muzzle?

[bigngreen]

I don't have an of hand zero, honestly I made a commitment to such a small aim point I really wouldn't even take a standing shot on game anymore.
I do shoot some fun stuff of hand and the zero isn't changed but it takes a LOT of work not to drop shots or over compensate and push it up.
If I can't get into a position hunting that I can't have the gun tracking I won't pull the trigger because the gun will move differently. If I have to shoot of hand it's likely a messed up situation and I'm close range trying to get something dead for someone in which case I'm probably shooting a 6 inch group so there really isn't a zero.

 

[codyadams]

I don't have an of hand zero, honestly I made a commitment to such a small aim point I really wouldn't even take a standing shot on game anymore.
I do shoot some fun stuff of hand and the zero isn't changed but it takes a LOT of work not to drop shots or over compensate and push it up.
If I can't get into a position hunting that I can't have the gun tracking I won't pull the trigger because the gun will move differently. If I have to shoot of hand it's likely a messed up situation and I'm close range trying to get something dead for someone in which case I'm probably shooting a 6 inch group so there really isn't a zero.

Off hand consistently is sub 200 yards, many times less, for pretty much anyone. When I was competing at a national level in 4 position small bore, I felt confident off hand out to 250-300 yards, but I was shooting well over 20,000 rounds a year practicing at that time, probably half of that off hand. Anymore, unsupported I wouldnt shoot over 150 unless like you said, it was a bad deal. So really....offhand zero doesn't matter much, and would be challenging to even determine.

 

[Deleted member 107796]

After overcoming inertia.

I agree, which would include case and primer expansion upon ignition, but well before barrel exit.

 

[Susquatch]

One issue that seems to be forgotten here. It is NOT the real or perceived movement of the muzzle crown.

The bore line is the axis. Upon any point there can be a " fulkrum". Keep the the crown position and move the breech either to the side or verticle. You now have changed the bores inclination..right. will that change your POI? Certainly!!
And what's or who's near the breach of the bore? Does that make sense now. Good address and form is a virtue in marksmanship.

This is essentially the 40 thou I referred to in my other post with your "fulcrum" chosen as the action simply because that's where the line of sight is anchored.

Yours is a very good way of looking at this issue.

I considered a much more complicated explanation but abandoned it in order to avoid boring most readers. However, since you have chosen to dive a little deeper, I think it's worth noting that the axis of the bore is not actually a line or axis while the bullet travels its length. It vibrates in several ways. Whipping at its forced natural frequency, longitudinally, torsionally, and internal sound waves (which make the barrel and bore fatter and skinnier). There are also multiple harmonic vibrations in each of these.

I would also point out that it isn't just the muzzle end that moves. The entire rifle and chamber end (including your fulcrum) also move during recoil (as well as other movements) all of which can amplify the resulting shift in POI.

To be frank, I think it's amazing that any rifle can ever hit anything with all that movement going on, let alone result in such a modest POI shift of just 6 MOA......

 

[Susquatch]

I have a 6 Dasher that is 17 lbs, trigger is 2 ounces and is the only thing touched and the rifle free recoils, rear bag is solid and the butt stock is pounded in, the rifle slides with one finger back and forth, there is .010 of drop in the entire stock of the gun. If during a course of fire I change how that gun moves my groups BLOW up, if my jacket touches the butt stock you'll see it in the group, the movement of the rifle under recoils is a huge, huge factor in bench rest to the point that it drive almost everything!! You can change the sand in your bag and it will measurably change your group, the only way for that to happen is that it changes the way the rifle moves in recoil with the bullet in the barrel. I'd say I've put more effort into how my gun moves during recoil to tighten up my Dasher groups than I put into the load. It's HUGE!!

I have wondered about the sand thing for some time now. My "theory" (nothing more than that) is that the sand type changes the damping factor for various rifle vibrations.

Since I do not compete, but do love to shoot tiny groups, I have not played with it extensively, nor have I done any analysis. I just use "heavy sand" and pack it in both bags as firmly as possible. That seems to work for me.

If you have any insights into this particular matter, I would LOVE to hear them! No matter how old I get, I always always enjoy learning something new.

 

[JC Lepley]

I'm experiencing POI shifts with a 338 RUM going from bench rest, to bi-pod, to shooting off my pack. I believe the main cause is recoil effecting POI before the bullet exits. My theory is that shooting off my pack allows the rifle to kick straight back, but on a bi-pod it "rocks" back allowing the butt to move down and the barrel to point up, and off the bench rest its causing muzzle rise as the gun has no where else to really go. All 3 positions are printing sub MOA groups, but each position is shifting the "zero'.

Bench POI is highest, followed by bi-pod, and shooting off my pack is the lowest POI. (All shots taken with front hand holding the forearm. POI change is about 6 MOA from Pack to bench.

Some people on here claim to have experienced similar issues, while others say that its impossible for recoil to occur before the bullet exits, so it must be parallax, flinch, body positioning or something else. The rifle did this with the factory synthetic stock and also with a wood stock that is piller bedded, glassed and floated.

I don't experience this with lesser recoiling rifles. I'm not an elite marksman and this rifle is a challenge to shoot (with over 50lb's of recoil). I did qualify expert marksman in basic training on my first attempt, my Grandfather was on the army shooting team and taught me well, but that was long ago and I'm just getting back into shooting a lot, so I won't rule out shooter error, but I think I've got the fundamentals down since this isn't happening with my little guns.


Anyone have any insight as to whether or not recoil occurs before the bullet exits?

Yes, exit velocity has an effect on sighting vertical plane.

 

[JC Lepley]

Yes, exit velocity has an effect on sighting vertical plane.

All simple physics. But not so simple so let the fun begin on the explaination.

 

[Mt rummy]

If you were to throw a baseball, trying to get the highest bounce and using the same amount of energy...which would give the highest bounce?
1. Cement
2. Grass lawn

Your forearm is analogues to the baseball. Do we want your forearm to bounce? No. Most like softer bags, rice hulls, cat liter etc. Teflon tape on forearm and bags to help slide with less friction is a help.

Here's a test to try; get a set of cross sticks. Rest rife in three sesperate positions.
1. Under floor plate
2. Under forearm sling screw
3. 1 inch from end of bbl.

Shoot three separate groups and see what you get.

The dynamics are two fold. First is ability to hold, second is influence to affect the rifles movement and vibration by placement of the sticks.

In proper cross stick shooting, you get rid of any beer belly. Seat and knees are parallel to target. Heels sucked up and touching your seat. Free hand elbow wraps front knee and hand between belly and knee with a two finger pinch. Head lays on stock with no neck tension. Bbl is held by the last half inch. All you will see is your heart beat. Will your poi be different? You bet but you will be consistent. Consistency is what we strive for. More importantly, how we effect change.

 

[bigngreen]

One thing I think that has been failed to get a mention is the swivel studs on most hunting rifles, they will wreak havoc, your rifle can not move consistently if it's dragging a swivel stud across a front or rear bag!!

 

[bigngreen]

In proper cross stick shooting, you get rid of any beer belly. Seat and knees are parallel to target. Heels sucked up and touching your seat. Free hand elbow wraps front knee and hand between belly and knee with a two finger pinch. Head lays on stock with no neck tension. Bbl is held by the last half inch. All you will see is your heart beat. Will your poi be different? You bet but you will be consistent. Consistency is what we strive for. More importantly, how we effect change.

Could you post a picture, I can't make sense of that and I've done a lot of positional shooting and teaching, just hard to visualize!

 

[Mt rummy]

I'm away but I will get one this weekend. Think of a pill bug. You and the rifle become one.

Here's a POI story to stick in your pipe.

1996 I went over to Caly to shoot their state shoot. ( Back when they still allowed guns) The relay was offhand 100 yd standard face. The day was to be a full lunar eclipse. It took place during the relay

My first shot was at six, ten ring. I called second shot in low nine ring. Spotter calls high ten ring. When your calling ability goes south, it's easy to fall apart like an old woman's watch. At this time the shooter next to me is singing cuss words. I look back at my spotter and point to next target and he calls high nine for me.

During the relay it is getting almost dark. The air was dead still. The atmosphere became freakish. Down the line it was apparent everyone was at wits end. Voices of frustration could be heard for the whole line. I scoped others targets who I knew were competent shooters. All targets were showing a rise and right drift. Some were as high as the 7 ring.
No one knew what was happening or had it figured out. I consecutively shot a half ring lower on each shot or somewhat close on the bet somthing was amiss and trusting in the other shooters targets. Like hitch hiking off the dust splash of the previous shooter.

My finish was acceptable and I took the relay, but did drift right and no call I made favored right.

It was 4 or five years later while boring holes at a club ,I told this story to a guy who was a "real rocket scientist".

He was not taken back and in fact explained the phenomenon to me. When the moon blocks the sun, it lessons the gravitational forces on all trajectory and objects on earth including the weight of your rifle. The right drift is caused by the rotation of the bullet as it's like a magnified spin drift, as even rotational drift is governed by gravity. Now all of this is far above this dirt spitting cowboy's pay grade, but it does make sense as there is no other explanation for this once in a life time experience.

So for those of us who think our shifts are only affected by us and our rifles, this may expand your thinking. Good shooting!