ptm121X
Gunny Sergeant
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How to shoot through a loophole
07/21/2016 Last edited 07/21/2016 by ptm121
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There are a lot of tricks and tips out there for making these shots, but most are really overly confusing. This is really quite simple if you have time to set it up beforehand, so let me show you how to do it with your ballistic calculator.
There are two types of loophole shots: those where you are a fixed distance from the loophole, and those where you can choose your distance. If the distance is fixed, you want to know where the bullet it going relative to line-of-sight (LOS) as it passes through the hole, so you can cheat it towards the center. If you can move your firing position, your goal is to perfectly match LOS with the bullet path at the hole - that is, your near zero is the distance to the loophole.
For those who forget, you normally have a Near Zero and a Far Zero, since the bullet has to travel upward from the muzzle, through the LOS (near Zero), and then come back down to intersect the LOS at the target (Far Zero). This is how you can have an AR-15 simultaneously zeroed at 25m and 300m. Most rifles will have the Near Zero equal the Far Zero somewhere around 100yd - the bullet rises to it's apex, just kisses the LOS, and then drops from there. This is one reason that 100 yard zeroes are used a lot - if you're off and it's actually 95 yd or 105yd, the zero won't change much.
Here's a diagram explaining this. The top is showing the trajectory when you are sighted in for a distant target. The bottom left is a close-up of the loophole, and where the bullet is in relation to LOS, based on the position of the barrier relative to the Near Zero.
The bottom-right shows scope picture for each scenario. Note that while you can use the reticle and your ballistic calculator to know exactly where the bullet will go relative to the center crosshairs, it's not that important in most cases - if the bullet is clearly going to be below your LOS, just pin the target at the top of the hole. If it's going to be above, pin the target at the bottom of the hole. If it's very close to center, then just aim in the middle. The real trick is knowing your Near Zero, and if the barrier is closer (in which case the bullet will be lower than the crosshairs) or further (in which case it will be higher). To calculate that, follow the steps below.
The first steps are the same, no matter which case we are setting up for. Let's assume the target is 529 yards away.
Look at your dope chart and pick your dial. In this case I'm going to dial 2.9mRad (just interpolating between 500 and 550 in my head, like you would in a match):
Then, go to your "Zero Range" (this is Ballistic AE, but you will have a similar field in your app), and input the target range. Note that while normally having your Sight Height over bore axis within 0.1" isn't needed for good calculations, it's very important for these shots! So, if you want to be able to shoot a tiny loophole, you'd better have measured that very carefully.
Now go back and check that your 100-yard zero has a click value equal to what you're dialing for the shot, in this case 2.9 mRad. You could tweak it to be exactly 2.9 by changing the zero distance, but if it's within 1/2 click you're good to go. Here I'm happy with 2.86. You should also see ~0 clicks needed to hit your target, which we have.
Now go back and change your chart to display 0-50yd, in 1-yd increments. This will let us see exactly what is happening at close range.
And, spit out the data:
Now we can pick the data for the type of shot we are making.
1) You are a fixed distance from the loophole. Let's say it's 10yd in this match. We can see that the bullet is about 0.46" low at 10yd, which is 1.27 mRad. So, when you aim, you want to aim at the target with your crosshairs (since you are dialed 2.9 mRad), but be sure that the spot on your reticle ~1.3 mRad below the crosshairs is clear of the hole. Ideally, center up the -1.3mRad spot on your reticle with the center of the hole, assuming you can still see the target under the crosshairs at that alignment.
2) You can select your distance. In this case, look for the Near Zero - it's about 13 yd. If you can put your gun between 13 and 14yd from the loophole, you can just line the crosshairs up on the target through the center of the hole, and fire through a VERY tiny hole without hitting the barrier.
