BENCH TECHNIQUES FOR YOUR BEST GROUPS
By Jeff (AKA One Hole)
Last updated 1/5/99
I see many people out at the range, swearing at their rifle and wondering why it doesn't shoot as well as mine. When I watch them shoot I'm sometimes amazed that they can keep their shots on the paper! Shooters that are only interested in whether or not their rifle/ammo combo will hit a deer, might not care about small groups. However, varmint shooters who are trying to hit small targets at long ranges should care what their rifle, ammo, and especially they as a shooter are capable of.
I'm an avid home gunsmithing/reloading/varmint hunting hobbyist. I will tune and fiddle with a rifle until it reaches the maximum accuracy I think it can give. To do this, I have to be sure that the groups I'm getting are a result of the gun or the load, and not negatively influenced by my shooting abilities. I've spent quite a bit of time researching benchrest shooting techniques, and am now competing in Benchrest matches. A Benchrest competition is perhaps the best place to learn, and refine your skills, and also see how you stack up against some other good shooters.
Now, while I'm by no means an expert, I do have a number of rifles that I can consistently shoot 5 shot groups under 0.5 MOA at 100 yards, or under half an inch. Heard about covering your groups with a quarter? Well, I don't even start to relax until I can cover them with a dime. Some of my rifles I expect to cover 5 shots groups with something closer to an thumb tack (so I can call them a tackdriver). I shot one group in a registered competition that you could easily cover all 5 shots with an aspirin, and it wasn't even the best group of my relay!
A few years back, I used to read about the size of benchrest groups and wonder "HOW DO THEY DO THAT?". We're talking about 5 shots groups where the average of 5, of these 5 shot groups is usually under 0.25 inch. Contrary to what you may hear or read, that level of HONEST accuracy is harder to achieve than you might think. We're not talking about the occasional lucky group. We're talking about day in/day out performance! You are not going to get anywhere near that level, unless you learn and use a consistent bench shooting method to test and evaluate your guns and loads.
So, here are some of the things I've learned. This might not be complete enough to allow you to win a benchrest match, but it will sure help you shoot the best groups that you can with your varmint rifles. It's by no means a complete list but it's a start. You can take whichever ideas you choose to heart depending on your interest and, unfortunately, sometimes your budget. I use these tips seriously at the range, but in the varmint fields you can't practice this all the time. That's OK! That's the small concession I give to the ground squirrels! It's their edge! For the same reason, I won't take a shot under 200 yards with one of my serious varmint rifles (unless they're being chicken and only showing their head). I save those for the rimfires and Hornet. Besides, it would be too embarrassing if I missed!
I did not invent ANY of the following methods. They are covered in many good books, and I have spent some time talking with competitive shooters. So credit should go to them. I'm only trying to summarize the key points for those who might not want to buy the book!
BENCH AND BAG SETUP.... The goal is to get setup so that your rifle will practically stay aimed at the bull, without any guidance from your hands. This also will allow a consistent recoil path for the stock to move EXACTLY the same every shot. Sling swivel studs are a big problem here. They will catch on the bags during recoil and cause inconsistent stock movement. Unfortunately, they place these swivel studs right where your rifle needs to be resting on the bags. If you want to do some serious load and accuracy testing take off the studs. The other option is an attachment that Hart makes. This has a flat bottom and attaches to your swivel studs. The flat bottom "rides" the bags very well.
IF available, use a concrete bench. These are much more sturdy than a wooden one. At my range, when I'm on a wooden bench and sighted on the bull, if someone fires a shot a few benches down, it will move my crosshairs off the bull.
Get the sturdiest, heaviest front rest you can afford. Hart's is one of the best. Bald Eagle also makes a good one. Hopefully the front rest will have the forearm stop post in front that prevents your stock from moving forward. This assures that your rifle is in the same place on the rest for each shot. This is very important. Don't believe it? Shoot a few groups with the stock resting on the bag near the tip of the stock, then shoot a few groups with it a few inches back. I bet your POI (Point of Impact) will change. If you don't have the stop, place some tape on your stock that you can use as an index point to the front rest.
The rear bag, should have bunny ears, to rest the buttstock in. Even the sand you put in the bags makes a difference. There is a sand called Heavy Sand, or Zircon. When I heard about this, I thought it's one of those gadgets that doesn't buy you anything. Wrong! It definitely helps. Bags filled with heavy sand, which is a very, very fine grain sand, are extremely stable.
Place the front rest on the bench so that the rifle barrel will hang over the edge of the bench. Align the rear leg of the rest so that it is pointed directly at your target. Then place your rear bag so the V between the bunny ears is in a direct line with the target and the rear leg of the front rest. Position your rear bag about an inch from the end of the stock, or you will get fliers. You don't want the rifle to be binding in the bags, or to have to twist, or torque it to one side to get it pointed at the bull. Remember it should point, and stay on the bull while you're not even touching it.
Now set your rifle in the bags and adjust the front rest height so that it is pointed at the bull while the rear stock is on the rear bag. Test your setup by sliding your rifle rearward, like it would in recoil and then slide it forward to the stop it should still be pointed at the bull. You can't do this unless you have good bags and rests and good sand in both the front and rear. Benchrest shooters use baby powder, or Suave Antiperspirant spray on their bags to make them slippery to help the stock slide smoothly. If your stock is textured, or checkered, this might be a problem. There is a special Teflon tape made to stick on your stock, which smoothes out texture in the stock and helps it slide consistently.
One quick note. Many shooters feel you can make slight elevation adjustments by squeezing the rear bag. OK, sometimes you might have to do this, BUT they should be VERY slight adjustments! Ideally, you'd like to not have to do this. It would be better if your rifle was pointed at the bull and your only contact with it, or the rear bag, was at the trigger. That is where fancy front rest with elevation and windage adjustments really are useful.
SCOPE SETUP.... Most Varmint scopes have an adjustable objective. If you read the manufacturer's brochures, they tell you that parallax error will only amount to a small fraction of an inch at 100 yards. Well, first of all, it's small fractions of an inch we are worried about here. Secondly, what they don't always point out is that parallax error is a function of scope magnification. It might be a small fraction of an inch at 4 power or even 9 power but when you get to 24 power or 32 power, it becomes a much larger fraction of an inch. Most folks just set their front ring to the 100 yard mark. But these are not always (hardly ever) calibrated correctly and they will change due to temperature. On some scopes, you might have to have the ring set closer to the 200 yard mark before it is parallax free. So take some time to adjust out your parallax. Once you've got your rifle sitting on your bags, and aimed at the bull, move your eye back and forth sideways being careful not to move the stock with your face and watch and see if the crosshairs move on the target. If they do, you have a parallax error. Adjust the front ring until moving your head sideways doesn't move the crosshairs on the target. Then check it by moving your head up and down. Some scopes you will be able to adjust out the parallax for lateral movement but not vertical. You can't have it all! So pick one or try to get the least amount of movement between the two. If you don't adjust out the parallax, you will get POI changes by not lining up your eye with the scope exactly the same way each shot.
A quick note here. This tip was given to me by Randy Robinett, who was the Hunter Class 100 Yard National Champion last year and has made quite a study of the internal workings of a scope. The mechanical design of the adjustable objective has some, what we will call screw lag. In other words, if you are going back and forth on the ring while you are adjusting this you might leave the lens assembly in an unsupported position, in a state of limbo, where it's not supported on either side and it can wiggle slightly. Basically, the lens and consequently your aiming point will move under recoil and not be consistent. For this reason, it's best to always set your front ring by coming in from one direction. After finding that point where you have no parallax, mark it somehow (you can use tape with the correct yardage printed on it). Then turn your front ring one quarter turn one way and come back and stop right on your mark. Now we're getting nit-picky but hey, how you gonna shoot a quarter inch group?
TRIGGER CONTROL.... Ever wonder why benchrest shooters use triggers that have 2 ounce pulls, or less? Well, look at it this way. Let's assume the front of the rifle was fixed couldn't move. If while you were pulling the trigger, you just moved the rear of the rifle just 1/100th of an inch, you've just changed your POI about and 1.5 inches. JUST 1/00th OF AN INCH and you've just blown your group! So, it stands to reason, the more force you must exert on your trigger to release the sear, the more the rifle will move. I like to think of it this way. A two pound trigger requires half the force of a 4 pound trigger (32 oz Vs 64 oz). So, a 2 oz trigger requires 1/16th the force of a two pound trigger (2 oz vs. 32 oz)!
I can't tell you how many rifles have had amazing improvements in groups, just by changing to a competition trigger, or at least having it adjusted as low as you can get it. This is the first thing you should do to a rifle that you're expecting great things from. WARNING! Triggers are very touchy and sensitive mechanisms. If you are not sure what you are doing, have a gunsmith adjust your trigger and test it.
Now, test what your trigger pull is doing. You don't need ammo for this. I like to start with the gun cocked and the safety on just so you can see how much your crosshairs move when you pull on the trigger. Get set up like you're ready to shoot and aimed at the bull. Now squeeze the trigger, while keeping a very close eye on the bull and the crosshairs. Did the crosshairs move? Then expect it to move when you shoot for real. Now play around with different positions for your trigger hand and thumb. I'll bet you if you place your thumb on the side of the stock that you will get lateral movement when you pull the trigger. A better place to put your thumb is on top of the tang or not place it at all. Some benchrest shooters will place their thumb on the back of the trigger guard, and just squeeze thumb and trigger finger together to fire. Whatever method you use, you should be able to exert enough force on your trigger be it 2 ounces or 2 pounds without causing the crosshairs to move on the bull. Practice this.
RECOIL CONTROL.... With light kicking rifles, like most varmint rifles, you might get better results using the free recoil method. This means your shoulder is not pressing into the stock, but maybe just behind it by a fraction of an inch. Remember we're trying to get the rifle to act in exactly the same way for every shot. If you're pressing your shoulder into the butt, how can you control the amount of force you exert on it exactly the same way each shot? By letting the rifle free recoil for that fraction of an inch, you are giving the bullet time to get out of the barrel, before you screw it up! Try this method and see if it improves your groups. Heavier kicking, larger caliber rifles need to be held with some pressure against the shoulder.
GOTTA GET DIRTY FIRST!.... When you're ready to start shooting, don't just take your cold & clean barrel (CC) and start right off with your first shot of a group. Barrels need to be fouled and warmed up before they will settle down. If you only make 5 of a particular load, like I used to do, my groups were often the 4 and 1 type group. With the first shot being the flyer, and the others all in a cluster somewhere else.
There are two separate mechanisms at work here. The first is the warm up. Cold steel will have different harmonics than warm steel. There has been tests done that say it takes at least 30 minutes after a shot for a rifle to get back that "cold" status. So you usually don't have to worry about this after having to wait 10 minutes between cease fires at your range. I often use targets that I print myself and copy because I shoot a lot of them. These targets usually have 4 bulls on a standard 8 x 11 page. I always use the first bull to shoot that CC shot and a few warm ups. This way I know how each rifle shoots when it's CC. It's not uncommon for that first shot to be an inch out of the group.
The other factor is fouling. Both copper and powder. Most shooters are aware that a few fouling shots are required, but they usually only worry about copper fouling. What fouling is doing is filling in all the microscopic nooks and crannies in your bore with copper from your jackets. A certain amount of fouling is good, we want that. Of course, too much fouling will start to hurt accuracy. However, powder plays a part in the fouling also. And different powders will leave different amounts and types of residue in your bore. Here is why this is good to know. Like I said, I used to load up 5 rounds each, of many different loads. I thought this would be enough to give me a good statistical look at the chronograph data and also give me an idea of group potential. Sometimes, when I would switch to a load with a new powder the groups would be bad. I figured these were bad loads, but some of these turned out later to be excellent loads. What I didn't know then was that switching powder will also require a few shots to settle down your barrel and get it used to that new powder. I was surprised to learn this but it's true.
OK, SHOOT A GROUP!.... Now, you've just taken your first shot. The rifle has moved back in the bags. Gently slide it forward until it hits the stop or move it up to your tape. The crosshairs should be back on the bull and you're ready to put that next shot through the same hole! But wait!
Most heavy barrels do a good job of heat dissipation. Sporter weight barrels do not. As the barrel gets hotter, POI will change. Even heavy barrels will show some movement. So it's best to give a consistent wait period between each shot. For your best groups, wait one minute between each shot. And while you're waiting don't leave that next round in the chamber. It will get hot and if it's a near maximum load pressure could change just enough to blow out your groups. By the way, if your heavy barrel shows signs of changing POI's as it gets warmer and it's COMPLETELY free floated with plenty of clearance, having that barrel cryogenically stress relieved (frozen) might help correct this.
OK, now shoot the rest of your group. Do everything the SAME way for each shot. Trigger pull, slide it forward to the stop Voila! you have small groups. Or, you at least know it's not you and that your rifle or your load needs some fine tuning.
WIND AND MIRAGE.... Don't we all hate it when you've got that scoped cranked up all the way and all you see is a big blur? Well, mirage can be an aid in reading the conditions. Unfortunately, I'm not good enough yet to tell you how to do this. What I do know, is that mirage will "follow" the wind. If there is no wind the mirage rises straight up they call this a "boil".
What it does is fool you into aiming where the bull is really not! This can cause a half inch or more of error at 100 yards. So, if you shot your first few shots while your barrel was cool and there was no mirage then things get fuzzy and you aim at what you think is the bull, you might get some vertical fliers. Some of the mirage will be exacerbated by the heat from your barrel. However, some of it will come from the conditions. You can try to minimize this by using mirage tubes, which are usually long translucent tubes attached to your scope like a sun shade. Or, you can devise a shield to place over your barrel made from plastic or tin foil. A very light material should not affect your barrel harmonics. The best thing to do is practice in mirage conditions and see what affect they have on POI. In other words don't compensate for it when you see mirage and shoot where you see the bull. If you have a nice tight group going and all of a sudden your bullet hits half an inch high, you'll know that under that particular mirage you need to hold off half an inch low. Mirage will move laterally with the wind, so it can be used to give you an idea of how much the wind will affect your shot.
By the way, mirage DOES NOT go away by turning your scope to a lower power. You just are less aware of how much of it there is. You think it's not there but it is. Look at the equipment list of winning benchrest shooters. They don't have variable power scopes, they are almost universally 36 power fixed scopes! They want to know what the mirage is doing and how much to compensate for it!
And that brings us to wind. A good number of shooters just don't know, or believe what a 5 mph wind will do to a high velocity bullet at100 yards. A 5 mph crosswind, will move a 50 gr. 22 cal bullet traveling 3400 fps over half an inch at 100 yards. Double that for a 10 mph wind. BELIEVE IT! So, if you're not going to be like benchrest shooters and put out fancy windflags every 25 yards, at least be aware of the wind. Most ranges have at least one flag you can look at. When I don't want to set out wind flags I at least place a piece of long masking tape hanging down near my target and usually one on the chronograph bar right in front of my bench. Wind near the muzzle will have a much greater affect on wind deflection than a wind down near the target. Think about it. If a wind near the muzzle pushes your bullet slightly off course it has the whole 100 yards to keep going off course. Unfortunately, they don't straighten themselves out! It will keep going off on a tangent. Here's an idea! Don't try to shoot your best groups when it's real windy! Realistically, at least try to shoot each shot in an identical wind condition by looking at flags or other indicators (tree branches grass, cigarette smoke etc!)
WRITE IT DOWN.... Always keep your targets. Date them, fill in the load data and things like temperature and wind conditions. These can be very helpful when you're trying to remember if you've ever tried a particular load, or how it performed. For your pet loads, this is also a good way to track the performance of the load and your gun over time. When your pet load starts to open up, it could mean it's time to rebarrel, or something else is wrong with your gun.
WHAT IS GOOD?.... How do you know when you've reached the maximum potential of your rifle? This will vary by rifle type and caliber, but here are the guidelines I go by after having tuned and tweaked quite a number of varmint rifles over the years. The following guidelines are for a standard factory rifle. Rifles with premium barrels, custom actions, or trued factory actions should be able to do better depending on the caliber.
By the way, caliber plays a big part on what kind of accuracy you will be able to get. Factors like case design, powder capacity/bore ratio and especially bullet availability make some cartridges inherently more accurate than others. For example, and I got this from Shilen's web site, a 340 WBY has an accuracy potential of .75 MOA. Meaning no matter what you do to the gun, or your load, about the best you could expect would be to average .75 inch groups at 100 yards. On the other hand, the 6PPC has an accuracy potential of .1 MOA. Meaning that if you have a perfect barrel, perfectly mounted on a true action, you could potentially get tenth of an inch groups at 100 yards.
Ok, here's what I strive for. If it's a heavy barrel, bolt action in a good varmint caliber I shoot for 0.5 inch groups, but hope for better. If it's a standard weight sporter barrel, I shoot for 1 inch groups. Remember, this for an average of 5 consecutive 5 shot groups. There are not too many rifles that come out of the box shooting this well, but I've been able to get most of them tuned to this level, just by doing stuff that the average home gun hobbyist can do. This might include adjusting the trigger, rebedding, lapping scope rings, or firelapping the barrel. I used to jump right into load development when I got a new rifle, but they never performed like I wanted them to. So after doing all the above I'd have to do the load development all over again. Those components add up. Now when I get a new rifle, I rebed it, replace or adjust the trigger, and usually firelap the barrel before I ever even put a scope on it and take it to the range.
Finding the right load is the key remaining item. Geez, that topic could take up a whole book, but until you experiment and find that load, you won't get optimum accuracy from your rifle. The two quickest tips I can give you are pick a powder that other people report performing well in your caliber and concentrate on finding the perfect seat depth for a given bullet.
Good luck and may all your groups be ONE HOLE
Posted with permission of Varmint AL