Ammunition Temperature

And Your Sniper Rifle

Does the temperature of your Ammunition matter?

It is common knowledge that many factors affect the flight of your bullet. Many shooters spend a lot of time and energy taking barometric pressure readings, ambient temperature readings, worrying about Coriolis effect (Spin of the earth) and Spin drift (spin of bullet), all issues that affect the bullet path. But, these same guys do not consider their ammo sits out in the sun or is buried between their sandwiches in the backpack. The ATAC long range shooters are always looking for ANYTHING that has an effect on bullet flight.

One of the most important factors that affect the burn speed of the propellant in your cartridge, and in turn, the muzzle velocity of the bullet exiting your barrel is cartridge temperature. What was your ammo temp when you zeroed your rifle? I bet you probably documented everything else, including how many coffees you drank on the way to the range.

I was at the range the other day and a fellow shooting next to me was telling me that his rifle usually shoots low for about the first hour he arrives at the range. Then, after an hour or so the rifle shoots zero. I asked if he didn’t mind filling me in on exactly what was his procedure on getting ready to go to the range. He looked at me as if I was a little crazy. He told me that he loaded all his gear in the truck the night before. I asked including ammo? He said sure I don’t want to forget anything. So now he sits with all his ammo lined up like soldiers in a row sunbathing in the bright sunlight. In Northern Arizona, nighttime temperatures during the spring are usually in the 40’s. The cartridge temperature in the sun was 88 degrees after an hour in sunlight. Don’t think it makes any difference? You better test it for yourself and know first hand what/how these seemingly small things can affect those bullets headed down-range.

On your next outing to the range bring a iced cooler with 5 rounds in a waterproof container. Let another 5 rounds sit in the sun for ½ an hour or so. Then, shoot these rounds back to back, you may be very surprised. I often carry 5 rounds in my pocket for this reason. Try it for yourself, and you might find out that IT DOES MATTER!

Lenny Bolton

Venom Tactical

ATAC Staff

Cold Bore or Cold Shooter?

By Lenny Bolton – Venom Tactical

THE COLD BORE SHOT . . . FACT OR FICTION????

It is often thought that the first shot fired from a cold barrel will have a different point of impact than the second, third or any other shot that is fired. Is this really the case, or does a “cold shooter” have an effect on this. There are procedures that can be performed to a precision rifle that will definitely have an effect on stabilizing the performance of the rifle, but let’s try something interesting.

Go out to the range and set up at 100 yards. Place a sight-in target with 1” grid squares on your target stand. Your sniper/precision rifle should have been cleaned from your last outing, so run a dry patch down the bore of your rifle to eliminate any oil residue. Next, spend 10 minutes Dry Practicing with perfect form. Call your dry practice trigger presses the same way you should be calling every shot you fire. This means calling the exact position of your cross hair when the trigger breaks (click). Be honest, cause you are only cheating yourself.

When you are satisfied with your dry practice, fire 5 rounds down range using exactly the same point of aim, again calling each shot. Each round must be fired with perfect precision, so . . . take your time! Use a spotting scope so you can see where each bullet impacts after the shot, and compare with your “called” shot. Go down range and check your group.

Do this for your next 5 to 10 outings to the range. Compare your targets or keep one target, using it to shoot/date each group for this test. You may be surprised. Many shooters find that there is no difference between the first and the fifth round fired when adopting this procedure. Either way, you need to know.

Is it my rifle? Or could it be me????????

Lenny Bolton

ATAC STAFF

Venom Tactical

Scopes come in two main types fixed power and variable power. Fixed power scopes have less moving parts theoretically enhancing durability.

Variable power (adjustable magnification) have more moving parts but are tactically more efficient allowing more viewing options. By having the ability to power down you have the advantage of using lower power, enhancing the ability to scan a larger area, this also makes the scope more usable at closer ranges or when light conditions are less than favorable. This is called Field of View. This is the difference between viewing an object with the naked eye vs looking down a tube.

10 x 40 means the scope has ten times magnification and the objective lens is 40mm.

3.5×10x40 means the scope has the ability to magnify an object form 3.5 times to 10 times and the objective lens is 40mm

Optical Considerations and Terminology

Objective Lens:

The objective lens is just like a funnel collecting available light. Usually the higher the magnification the larger the objective lens. This is also dependent on the quality of the lens itself not all lenses are created equal. The disadvantage of large objective lens is that the scope has to be raised high above the bore centerline.

The sniper scope objective usually has a minimum of 40mm and a maximum of 56mm. There are scopes as large as 72mm for .50 cal shooting.

Tube and Tube diameter:

1 inch, 30mm and 34mm scope tube diameters are common.

Advantages of larger tubes are:

1. Transmitted light does not need to bend as much when traveling down the tube allowing for less distortion around the edges of the image.

2. Larger tube allows larger internal lenses allowing more light to be transmitted to the shooters eye.

Ocular Lens:

This is the lens you look through.

Eye Relief:

The distance you can place the scope away from your eye and still get a full field of view. This usually is around 2.5 - 3.0 inches.

Exit pupil:

The diameter of the light column that is transmitted to the eye. This column of light should be roughly equal to your eyes pupil diameter in low light typically between 4mm to 7mm. This can be calculated by dividing the size of the objective lens by the power for example: 40 divided by 10 = 4 or 40 divided by 3.5 = 11.4 as you can see the lower power will transmit more light.

Lens Coatings:

Coated lenses will enhance the passage of light and reduce reflection. Some manufacturers have multi coated lenses further enhancing the optical performance of the rifle scope. Scopes can have 8 or more internal lenses.

Adjustments Ocular:

Objective Focus:

Some scopes have an adjustable objective lens focus ring. This focuses the objective lens to the target. Most modern scopes do not have this feature anymore.

Parallax:

Many modern scopes have a Parallax adjustment knob on the side of the scope opposite the windage adjustment dial. With reticle you only have a sight in one position unlike iron sights. This is like looking at a bathroom scale. If you look straight down, the indicator needle reads one thing and if someone standing to the side view the scale they will get a different reading. Adjust your Parallax till the target looks perfect.

Magnification (Power) Ring:

This is used to adjust the magnification of the scope.

Ocular Focus Ring:

This adjustment is used to focus the eye to the Reticle ONLY. This should be setup when the scope is mounted and should not have to be re-adjusted.

Reticles: Used for Long range rifle applications:

Post, German Post, Plain and Duplex. Not that good for ranging. We prefer Mil-Dot and the Leupold TMR reticle, but there are to many reticles to mention. The Mil-Dot and TMR are very good reticles for target ranging. Some scopes have illuminated reticles these work well in low light and when a target has a black background.

The Mil-Dot reticle is graduated in Mils 1. Mil = 3.6 Minutes of angle we usually round this off to 3.5 Mils. Apart from ranging these reticles are useful in many other ways and are used by most branches of the military and law enforcement.

Adjustments Mechanical:

There are many different types of turrets. We are most familiar with the minute system. 1 minute of angle (MOA) = 1/60 of 1 degree. 1 MOA is 1.047 inches at 100 yards in most cases we round this off to 1inch. 1.047 x 1000 = 10.47 inches at 1000 yards. We round this off to 10 inches. Common scopes have ¼ min, ½ min and 1min resolution.

¼ Minute scopes are good for target, varmint hunting and Police sniper engagements. We prefer ½ minute and 1 minute graduations for tactical applications. Bullet drop compensator dials (BDC) are also available for various calibers. These turrets are graduated in distance in yards or meters for a specific caliber. Basically you set the elevation turret to 300 yards and take the shot. Most of the time these turrets are close but I would not bet your life or mine on the calculated graduations. Some manufacturers offer BDC turrets based off your dope.

There is no industry standard as to the quality of a rifle scope. The formula that is usually the most accurate is the amount of wallet damage on purchase.

Scope Rings and Bases

SCOPE BASE

The scope base is the rifles optic mounting platform.

There are 2 main types of Scope Bases:

• TWO-piece
  
• ONE-piece
  

The two-piece is where a front base and a rear base are mounted separately to the receiver.

The two-piece allows for some irregularity in the receiver manufacture and is usually lighter in overall weight. If there is any irregularity in the receiver fit, this will have to be corrected by lapping the rings when mounting the scope.

The one-piece base is just that, one piece of steel or aluminum. The one-piece is usually heavier but offers more rigidity with more fore and aft adjustment options for scope positioning. It is imperative that the fit of the one-piece base is perfect to the receiver. If not, the receiver may be distorted when the base is tightened down.

The best bases are machined from solid billet. Quite often, cheap bases warp during the heat treating process. Some cheap bases are stamped or cast out of soft steel. YOU GET WHAT YOU PAY FOR! Do not save money when selecting the mounting base. Buy the best you can afford.

There has always been much argument as to which type of base is better. One thing that can’t be argued over is the fact that you spent alot of money for an expensive rifle and scope. That makes buying cheap bases and rings just plain stupid. If the fit of the base to the receiver is not correct, STOP and find out why, or take the rifle to a qualified gunsmith. Bases that do not fit correctly will either distort the receiver when tightened or will work lose while shooting the firearm.

Some bases have built in recoil lugs. This is a good idea that allows greater rigidity of the base under the recoil of the rifle. Good quality bases also have high quality mounting screws.

Common American sniper scope bases are built to the Military Picatinny 1913 Standard.

Some bases have a 20 MOA or more angle built into the base so that the scope is mounted with a down angle relative to the bore of the rifle. This helps with the range of adjustment available in the elevation turret of the scope.

Some of the good quality bases we have used are manufactured by Leopold, and Badger Ordinance.

RINGS

The rings mount the scope to the base.

There are also many different types of rings available.

The quick detach style scope rings do not have a place on a sniper type rifle. Your rifles zero may save your life or the life of someone else. Are you prepared to gamble? I’m sure not.

We prefer the Leupold MK4 Tactical scope rings.

Quality 2 piece rings with at least 4 screws each are required. Some rings have 6 screws on each ring.

One thing to bear in mind is that the wider the ring the more the probability of tweaking the scope body when tightening the ring halves if the rings are not perfectly aligned.

Rings should always be selected to allow the scope to sit as low as possible on the action. You only need clearance for the objective lens of the scope. Mounting the scope higher than necessary will only cause problems with cheek weld and also make the scope more prone to damage.

Don’t skimp on rings and bases it will cause you nothing but frustration, lost time and wasted ammo.