View Full Version : Sight-in with the same ammo you use hunting.

10-24-2001, 07:15 PM
Sight-in with the same ammo you use hunting.

Jim Matthews Column 10/24/01

With most Southern California deer seasons now in full swing and many hunters returning from or leaving for out-of-state big game hunts, the phone has been ringing in recent days with tales of woe -- the stories of missed game and trophies that got away. Too many times, the miss wasnít the result of poor shooting or shots simply taken at too long a distance. It was the result of a hunter assuming that all ammunition shoots to the same point of impact.

I see it all the time at the range. Guys start showing up the week or two prior to their hunts, and they shoot up all the ammo they have at the range in getting the gun sighted in, shooting a group or two, ringing a gong at 250 yards, and then they slip the gun back in the case. They have developed confidence in the gun and know itís sighted in. Then they made the big mistake by heading over to the sporting goods store to buy a box or two of ammo to take hunting. Often they get a brand and bullet weight that is different that what theyíve just shot at the range. Naively, they believe it canít shoot differently enough to matter.

Oh, but it does.

I recently spent the day at the range shooting a couple of rifles -- one a 7mm Remington Magnum and one in .338 Winchester Magnum. I had a variety of different ammunition for each gun and was seeing which factory ammo each of the new rifles shot the best. All of it was good big game hunting ammo, so if it was just a matter to see which one or ones would shoot best. Interestingly, because of recent calls about missed game, I was noticing more than normal about how differently the different loads grouped on the target. It was a graphic representation of how important it is to sight-in with the same ammunition you will be using in the field.

The 7mm mag was dramatic in the spread of its groups. The loads that I had used to sight-in the gun -- Federal Premiums with 140-grain Noslers -- were originally sighted in to be about two-inches high at 100 yards. That was where they continued to group. Without changing the scope, some Winchester 160-grain Fail Safe loads shot two inches low at 100 yards, and Winchester 150 grain Ballistic Silvertips were four inches high at the same range. While that spread might not seem so great at 100 yards -- all of the slugs in about six inches -- the difference really starts to magnify at longer ranges. With the Noslers, the gun should be pretty close to dead on at about 250 yards, but the Fail Safes would be well over a foot low at the that same distance with the same sight settings. More than enough to shoot under a buck or bull.

If I had resighted the gun in with the Fail Safes so they were two inches high at 100 yards, the Ballistic Silvertips would have been shooting six-inches high at 100 yards. A shot at 300 yards, where a hold on the top of the buckís back would have been deadly with the Fail Safes, would have been a clean miss well over the top of the buck with the Ballistic Silvertips. You might be lucky and have a gun that shoots most ammo to about the same point of impact. The .338 I was shooting groups Federal Premium Barnes XLC 225 grain slugs dead on at 100 yards (where I wanted them for hog hunting). But it also shot Winchester 230-grain Fail Safes to almost the same point of impact (maybe a 1/2-inch lower) and some Federal High Energy Trophy Bonded 225 grain loads about an inch high at 100 yards. Some older 220-grain Winchester Power Points were also right on at 100 yards. For some reason, bigger bores tend to shoot their slugs closer to the same point of impact, but you never want to bank on this without testing your gun.

And donít assume that all bullet weights will shoot to the same impact point. I have a 7mm-08 Remington that shoots three brands of 140-grain loads to three distinct grouping points at 100 yards, all the 1 1/4-inch groups strung out about eight inches on the vertical. I found this out before range testing that hard way -- I missed a pig at 100 yards assuming some new loads that arrived the day I was leaving on a hunt would shoot about the same as the oneís Iíd been using. They were -- afterall -- both 140-grain loads.

Each load fired in your rifle sets up a different vibration pattern in the barrel, causing the bullet to leave at a slightly different point, and each slug will have different flight characteristics. The difference between a round nose slug and a pointed bullet with a boattail is obvious. That obvious difference really comes into play at longer ranges. But even subtle difference make a difference. Reloaders know that simply changing the make of primer can often change the impact of the slug. So different brands of ammunition -- even those using the same bullet -- will often shoot to dramatically different impact points.

The moral of this story is to sight-in your gun with the ammunition you will take into the field. I donít want to hear your tales of missed game.