Accuracy of the Long Straight-in Shot

[cigardave]

The only interesting rifle is an accurate rifle, eh cigar?

True dat, brother. :thumbup:

Back to OP's question... she didn't ask which is more difficult to do... but rather she asked whether the two are equivalent from an accuracy standpoint... and I believe that is aiming accuracy, not stroking consistency, which some of you are assuming.

Here's some distances for those who want to start the geometry calcualtions:

distance from close edge of CB to close edge of OB... 46.5"

distance from close edge of OB to CL of LH OB in throat of corner pocket... 55"

and same measurement for RH OB in throat of pocket... 54.25"

and lastly, the spacing between CL-s of the two OBs in the throat of the pocket... 2.25" (recall that I have pro cut pockets on my 9-foot Diamond, which are 4.5")... and half of that is exactly what I measured.

With that info, the angle of aiming error can be calculated using simple geometry... and just convert the answer in degrees to inches of MOA and you have the answer as to which of the two requires the lesser degree of accuracy when aiming (to be successful). :thumbup:

(Recall that a MOA is 1/60 of a degree.)

 

[ShootingArts]

a lot like pool . . .

I shot a couple of 'fun' matches off the benches with two .22 rimfires I had, but it was a good friend who did the centerfire stuff. It was amazing to watch thru a spotting scope, very scientific and all, but it was one of the most boring sports in the world, otherwise. You mostly just stood around watching shooters reload their ammo. And some people think One Pocket is tedious. :smile:

Benchrest is a lot like pool, fun for the competitors, not much of a spectator sport. I had six or seven windflags out at 200 yards and seven minutes to shoot five shots for record. Sounds simple enough doesn't it? One of my windflags rotated over 720 degrees without stopping, that's right over two full circles! I have also had flags never stop veering back and forth for the entire seven minutes so I finally ripped five shots downrange with the single shot rifle with only a few seconds to go. My group on the moving backer was almost the same size as the group on the target! Benchrest shooters only impress me moderately in mild conditions. When I shoot with the same guys in pouring rain or 30-40mph winds and their group sizes are basically the same that's something to see if you are a shooter.

These guys ain't sissies either. Nobody bothered to officially cancel a shoot when a named storm came through. 50-60mph winds and eight or ten shooters showed up. They held the match! Seven inches of rain during another two day match, the only time we stopped shooting was when they had to take time to rehang targets that got soaked and blew away. One relay Saturday I was finally going to get to shoot in less than an out and out downpour. A wet target blew away and by the time it was replaced it was raining hard enough to make it tough to even see a target at 100 yards. The winner's group sizes were a few hundredths of an inch bigger than they would have been on a mild summer day!

Getting back to the original question, there is more of a chance of me missing a shot with the cue ball on the foot spot and the object ball halfway between it and a nearby corner pocket than there is of me missing a dime at 100 yards.

The big difference, benchrest is 95% or more equipment, tuning, mental, and applied knowledge. A nerve can misfire shooting pool or a muscle contract a little fast or slow and you can miss no matter how perfectly you set up a shot. A friend that competed with me in pistol competition was watching me shoot my benchrest rifle one evening. I sat him down behind the rifle and coached him to a five shot group that was under 0.125" center to center, his first group ever fired from a bench. That is one slightly out of round hole on the target and the same size group I was shooting myself that evening. You measure outside edges and subtract one bullet diameter. This is roughly the equal of a century run in snooker or 3-5 consecutive nine or ten ball break and runs on a tough nine footer. Ain't gonna happen the first time somebody touches a cue no matter who coaches them.

Hu

 

[cigardave]

So here's the answer to the question based on my interpretation of it:

The margin for aiming error to pocket the OB in the corner pocket on my 9-foot Diamond with pro cut pockets (as shown in the OP's table diagram) is almost 5X times greater than that required to hit a dime-sized object with a bullet at 100 yds.

I know that answer flies in the face of what most of us think when thinking about the difficulty of performing these shots... but that is what the geometry says. The difficulty aspect is a different discussion.

First off... for simplicity, I assumed that all formed triangles were right triangles... and that is a valid assumption because the included angles are so small. The induced error of my assumption is very, very minor.

Here's some of the details:

1. The calculated difference in the contact points of the OB to go into the LH side vs. the RH side of the corner pocket on my table is only 3/64" (0.04602")... not much room for error there. The included angle is only 2.34457 degrees.

2. When projecting the 3/64" margin for error of the contact point of the OB back to the CB, the calculated angle of aiming error is only 0.0567 degrees, which isn't much... but it turns out to be 3.4 MOA (because 1 MOA = 0.01667 degrees).

3. And 3.4 MOA (for the pool shot) divided by .705 MOA (for the rifle shot), the quotient is 4.8X... or almost 5X the margin of aiming error.

Questions/comments?... fire away.

Having shot both, the pool shot is more difficuilt to accomplish... even though the margin for aiming error is almost 5X greater.

Cheers everybody! :thumbup:

 

[Tramp Steamer]

I can dig it. My buddy let me look through the scope on his unlimited gun at a 200 yard target. It was hot and breezy that day. He asked if I could see the target and I said sure, no problem. He said something like, well it isn't exactly where you think it is because of the 'mirage' or thermal effect caused by the heat. You have to 'dope' those things out. I didn't know if he was talking about lighting up a doobie, or what, but I know the best shooters are those who can figure out the atmospheric conditions.
Pool players are like that to. The ability to figure out what the table has to offer and then shoot accordingly. (See how nicely I dovetailed that into a pool related response.)

This reply is actually to Hu, but Cigar you are indeed correct.

 

[jojopiff]

Me too

I scoff when people suggest these are the hardest shots in pool. I build up to this shot when warming up and eventually I'm drawing back to the end rail from here.

Course I have an eight foot table.

This is a drill I do sometimes and I start with the object ball at the first diamond and progress down the table. I don't find it to be all that difficult but I also have and 8' with fairly wide pockets. Next time I go to the pool hall I'll try in on the 9' Diamond with tighter pockets and see how I fare.

 

[Bob Jewett]

... where's Bob when you need him?

Right where I've always been.

Remember, no matter where you go, there you are. -- Buckaroo Banzai in The Adventures of Buckaroo Banzai Across the 8th Dimension (but see below for an earlier reference)
​

If you measure the distance from the cue ball to the object ball in diamonds and the distance from object ball to the pocket in diamonds and multiply those two numbers together, you get the basic "difficulty" of the shot. This tells you directly how much your alignment can be off when you hit the cue ball. Just divide one centimeter by the difficulty, and that's your allowed error to left or right. The multiplication for the shot above gives 20, so your front hand (for example) must be in the correct position within 1/2 mm to either side or within a 1mm window. That's the thickness of a penny, more or less.

So there's this snooker player where I play who was practicing on one of the 6x12 tables, and he allowed as to how he would bet he could pot the blue and draw the cue ball back to the scratch -- more or less the same position given by the OP. I bet that he couldn't. He did it on the eighth try. With an open bridge.

"So, the cross is always ready and waits for you everywhere. You cannot escape it no matter where you run, for wherever you go you are burdened with yourself. Wherever you go, there you are."
—Thomas a Kempis, Imitation of Christ, ca. A.D. 1440​

 

[jay helfert]

I can remember seeing good players match up shooting that shot, but with the cue ball in the jaws of the corner pocket. They would take turns shooting until one of them missed. Sometimes it only took one turn and sometimes they would make three or four in a row. Harold Worst did this in Johnston City and made something like nine in a row, before everyone else pulled up. Worst was kind of like Shane today. He would play good in the tournament (usually winning) and then head for the practice room and try to match up with someone. Harold didn't draw the line anywhere. If someone (anyone) wanted to play, he was ready. And had his own money to bet too! Like Alex that way.

Now the shot that will make you sit up and take notice is this. Same set up with the cue ball in the jaws. Now you have to make the long straight in and draw the cue ball back into the same corner pocket. HELLO! Try this sometime when you have all day. Marvin Henderson was the best I ever saw shooting this shot. He hit it with that smooth stroke of his and the cue ball just glided straight back on the same line. I suspect today that Larry Nevel would be the best shooting this shot. I'd put my dough on him.

 

[ShootingArts]

the real secret behind the difficulty of a straight in shot

Very very few players hit the cue ball exactly where they think they do and very few have the cue stick moving in a perfectly straight line with the direction of cue ball travel. This applies to players right up through the pro's.

Nothing to do with math or percentages, a simple mechanical issue. A long straight in shot is the toughest shot on the table if you can't set up directly in line with the shot and stroke directly in line with the shot. Grab any ten random players at any event and I'll bet that most can't hit a ball exactly where they intend to without any angle to their stroke. Once they find out the goal of the exercise they can but most players don't set up straight and stroke straight.

Hu

 

[JohnnyP]

Wow, pure center ball hit.

 

[CreeDo]

That's cool that guys would match up on this shot Jay. Is there anything these guys won't turn into a bet?!

I've shot it before and my issue is with generating enough speed to make sure there's no rolloff. If I have fast cloth I know is dead smooth and level, you can cinch it and just do a really rigid, straight mechanical stroke. Sounds kind of weak but it works for me. But on a more typical table you have to just trust that your natural stroke and setup are perfect and let'er rip. I'm looking forward to trying to draw it back

For those of you who have tried looking at both the CB last and OB last (I recently switched to CB last on a lot of shots)... which would you look at here? I would probably go with CB, you can't afford any unintended spin.

Some might also suggest staring at the pocket as if shooting the CB directly into the heart of it. Makes sense to me.

 

[Robert Raiford]

BTW, the caliber of the rifle bullet does not come into play here... just sayin'. Rifle accuracy is based on the distances between the centers of impact

Measuring between the centers without considering caliber isn't useful for this comparison. What you're interested in is whether the bullet touches the dime, and that certainly depends on the caliber! That's why Hu said this in a previous post:

To hit a dime at 100 yards you have to add together the diameter of the dime plus the diameter of the bullet. Anything inside that area scores a hit.

I compared the angular arc for both shots, and a rifle shot of equivalent accuracy requires a bullet with a diameter of around 0.75". That means the bullet would have to be a bit larger than the dime to increase the margin of error enough to match the pool shot.

The rifle shot is harder, but you can't say how much harder unless you include the caliber of the bullet in your assumptions (along with pocket size, table size, etc.)

Robert

 

[Robert Raiford]

My feeling is that you have the same margin of error whether it is straight in or you have an angle to it. No matter where the cb is, you have to hit the correct spot on the ob.

That's a common misconception, but increasing the cut angle for a shot actually decreases its margin of error. Thinner cuts are geometrically more difficult (psychology is another matter!)

Margin of error is based on hitting to the right or left of your target by a certain distance. Yes, the ghost ball is the same for any cut angle, but hitting to the right or left of the ghost ball from the shooters perspective changes the cut angle different amounts according to a SINE function - it's not linear.

So if your error is +- 1/16th ball to either side of your target, then your error on a straight in shot (full ball hit) is about +-3.5 degrees. However, your error on a 61 degree cut (1/8th ball hit) would be about +9 degrees (thin side) and - 7 degrees (thick side).

Friction/throw complicates things a little more than this, but the basic result is the same: thinner cut angles require more accuracy.

Robert

 

[MitchAlsup]

A good read on the realizable limits of (unlimited) benchrest shooting:

http://www.angelfire.com/ma3/max357/houston.html

A good unlimited benchrest gun, in perfect conditions will shoot 5-shot gourps in the zeros! That is the size of the group is 0.099" or smaller at 100 yards (and no, that was not a typo. 0.099).

In imperfect (i.e. outdoor) conditions; ones win (0.1xx, typicall 0.13 and smaller) and twos (0.2xx) walk home (at 100 yards).

 

[searcyD]

i cut that ball

 

[CreeDo]

That's a common misconception, but increasing the cut angle for a shot actually decreases its margin of error.

I didn't follow everything you posted, but tell me if this is on the same lines or if it makes sense at least:

If you imagine the acceptible range of contact points as a tiny thin line running along the equator.. on a thin cut, half of the line is somewhere in back of the ball and you can't see or access them from your current angle.

You can sort of use it to your advantage though. It's tough to overcut the ball because some of that "overcut" contact area isn't available to you either. You can only screw up in one direction... whereas with a straighter (or straight in) shot, you can screw up in both directions.

Often when I judge a cut to be something like 80 degrees, I basically just say "cut until you can't cut anymore and will miss the ball"... and in a way that's maybe easier for me to visualize than a 70 degree cut.

 

[alstl]

That is hyperbole but it is a good shot for checking your stroke. Van Boening said when he wants to check his stoke he sets up a long straight in shot with the cue ball near the rail.

 

[Neil]

...............

 

[Robert Raiford]

Thanks, but you basically proved my point. A straight in shot is easier because you have a bigger margin of error to hit and still make it.:thumbup:

I must've misunderstood your intent then. Here's the confusing part:

My feeling is that you have the same margin of error whether it is straight in or you have an angle to it.

You're using the words "margin of error" in a different sense there, since the shot margin of error - i.e. the angular distance to the left or right of the target center that still makes the shot from the shooting direction - does change with cut angle (it shrinks). Now that I read it again, it seems you used "margin of error" to mean "range of contact points" (not strictly true because of throw, but close enough).

The common error is mistaking the range of contact points as the actual margin of error for the shot. That's what I was trying to clarify, but I see now that you weren't making that mistake.

So we're describing the same effect after all, just with different words

Robert

 

[Robert Raiford]

If you imagine the acceptible range of contact points as a tiny thin line running along the equator.. on a thin cut, half of the line is somewhere in back of the ball and you can't see or access them from your current angle.

Imaging a line on the equator is a good way to visualize the range of contact points and how it changes with cut angle. If you draw a line on the ball, it'll appear longest for a straight shot and appear to shorten as you increase the cut angle by moving around the side. You're unlikely to move parts of the line to an inaccessible part of the ball, though, unless you're making an extremely thin cut relatively close to a pocket.

You can sort of use it to your advantage though. It's tough to overcut the ball because some of that "overcut" contact area isn't available to you either. You can only screw up in one direction... whereas with a straighter (or straight in) shot, you can screw up in both directions.

I don't think it's ever an advantage to shoot a thin cut. The nature of shot margin of error is that you can always screw up in both directions. Screwing up on the thin side, however, means missing the ball sometimes. If you aren't occasionally missing the ball, then you've shifted the center of your target to thicker hits and are undercutting a lot just to avoid fouling. If you could control only screwing up on one side while keeping your target centered, why would you ever choose to screw up on the other side?

Often when I judge a cut to be something like 80 degrees, I basically just say "cut until you can't cut anymore and will miss the ball"... and in a way that's maybe easier for me to visualize than a 70 degree cut.

I sometimes say things like that to students too, even though I know it's not strictly true in terms of margin of error. It's more a psychological trick that leverages peoples fear of missing the ball completely. Sometimes, though, you have to risk missing the ball to maximize pocketing percentage. That's when it helps to have a rail nearby to bounce back and still make a good hit if you miss going in

The bottom line is that margin of error gets really small for thin hits, and cuts above 65-70 degrees should be avoided unless absolutely necessary. To put it in perspective, consider that a 70 degree cut is a very thin 1/16th ball hit. That's 20 degrees of cut (3 diamonds over a table length) in just a tiny 1/16th of a ball. On the other hand, an almost full 15/16th ball hit (1/16th ball off of dead center) only cuts the ball 3.5 degrees. That means thin shots can be up to 5x more sensitive than full shots.

Robert

 

[poolgirla1]

true

If you think of how small the contact point is when 2 perfectly round balls collide then you will realize that this statement is probaly true. All shots must be hit perfect in order to make the shot. place 2 balls together and you will see how small the contact point is. No matter how you place them together the contact point size is the same whether you are straight in or cutting the ball at an angle. I had this discussion with a very very good pool player once in Charlotte, NC at Paradise billiards. I wish I could remember his name???? He taught me alot about the realistic side of aiming and contact..