Accurizing Your Firearm: Part 3 - Finding the Right Load
Based on the range work, free floating the barrel did tighten up the grouping of the production grade pre-2006 Winchester Model 70 to some degree, but not nearly as much as I had hoped it would. In going over the results with a few of the other shooters after the session, the common verdict was that, while the gun was probably capable of better performance, it just didn't like what I was feeding it.
No two guns are identical. Within models, they might look the same, but take half a dozen of the same caliber to a shooting range and fire some ammunition through them. You'll find that each will punch a different grouping even when the ammunition used is exactly the same. One out of them might shoot a group worth bragging about, another might throw a group that you can barely hide under a pie plate and the performance of the other four will lie somewhere between the two extremes.
That's not to say that only one rifle out of the six is accurate and the rest are clunkers. Rather, it means that only one of them was in harmony with the particular ammunition you happened to be using. Change the load slightly and the super accurate gun might start throwing the pie-plate groups and the one that performed poorly might punch groups the size of clover leaves.
Most rifles are inherently accurate but to get the best performance it's
necessary to find the right combination of bullet weight and powder charge.
It all has to do with how any particular barrel jumps and vibrates in the nanosecond after you pull the trigger. Though the movement is imperceptible to the shooter, every rifle barrel jumps slightly at the detonation that takes place within the chamber of the gun and then vibrates as the bullet itself is pushed down the length of the barrel. Minute variances in the composition of the barrel, the way it is held to the stock and the torque used to attach the gun to the stock are just a few of the factors that combine to determine the degree of jump and the frequency of the vibration.
There are a couple of ways to deal with that phenomenon. Perhaps the easiest would have been to scour the gun shows for a Model 70 with a ballistic optimizing shooting system. Marketed by Browning under the acronym BOSS, it is a device which is attached to the muzzle of the gun much like a recoil reducer-which in part it is-and then calibrated to the ammunition being used. Unfortunately, while the BOSS is still available on Browning rifles, it was offered on Winchesters for only about three years during the 1990s, although the ballistic optimizer/recoil reducer can be purchased separately from Browning and retrofitted to other guns. While the device means that you can match your gun to the ammunition you want to use (of the right caliber of course), some shooters would rather not disrupt the clean, slim profile of a sporter barrel.
Matching the Ammo
Count me in the latter group. So I opted against the device and went with the second approach-matching the ammunition to the gun by trial and error. The trick is to find the particular load which performs best in a particular gun; in other words, the powder charge and the bullet type match the gun's idiosyncratic behavior, resulting in consistent accuracy, both on the range and in the field. Shooters who do their own handloading or have access to handloaded ammunition are probably in the best position to develop a custom load for a particular gun, but experimenting with different brands and loads of off-the-shelf ammo can provide acceptable results.
The .270 is an excellent caliber for all medium size North American game
including black bear. It's just a matter of selecting the right projectile.
So where to start? Well, in trying to find the sweet load for the Winchester Model 70 in 270 caliber, I started with selecting the preferred bullet weight and configuration. Since I would be hunting medium size game-primarily deer and perhaps some caribou- 130 to 150 grains with a moderately thick skin to hold on for a good mushroom seemed the right way to go. I put my hopes on Nosler's 150 grain Partitions. A good friend of mine is an avid and meticulous handloader with a penchant for a project just like this, so I turned over the bullets, the brass, the powder and the primers to him. A week later we met at the range and Doug flipped open his shell case to expose neat rows of gleaming brass cases, polished and resized, loaded and lined up according to powder type and charge in five one-grain increments up to the recommended maximum. Three dozen rounds in all, including the few extras to make sure the gun was still on the paper. Just where on the paper didn't much matter at this point, what we wanted to find out was how the individual loads grouped.
As part of the initial range work, inspect each fired round for sign of stress
that might indicate serious problems with the load or the cartridge seating.
Late that afternoon, we sat back and spread the sheaf of paper targets on the table, shunting any with a spread of more than two inches to the discard pile. In the final cut, only four targets made the grade, all four with tight cloverleaves.
"Not bad, but I think we need to fine tune the load a bit," Doug announced, leaning back in his chair. "Leave it with me for a couple of weeks. I'll see what I can do with it."
Perfect. That would give me plenty of time to do research on commercially loaded ammunition. I come from a time when you had only two options if you wanted accurate rounds-you rolled your own or else you knew a handloading fanatic who would load for you. The off-the-shelf fodder was tolerable but not terrific. Then, about 25, 30 years ago, ammunition manufacturers realized that there were enough serious shooters out there who had neither the inclination nor the opportunity to reload but were willing to pay extra for the opportunity to load up with premium ammunition to make the venture worthwhile. They were right.
The premium loads on the market these days are the closest thing commercially feasible to a true handload. Consider this-in order to keep the ammunition prices at an acceptable level, the manufacturers need to cut corners. Not to the point of compromising safety or reasonable performance, but certainly to the point of sacrificing accuracy. The powder charge can vary substantially and projectile itself-often manufactured in-house-might have a tolerated weight range of as much as plus or minus five per cent; the depth to which the bullet is seated in the case neck can also be inconsistent. It's virtually impossible to shoot a respectable group with this degree of variance for three essential reasons:
1. The differences in the powder charge results in small though noticeable disparities in the velocity and therefore trajectory of the projectile.
2. The tolerance in the projectile weight results in further disparities in the velocity and trajectory of the bullet.
3. The allowable tolerances in the powder charge and the bullet weight make it completely impossible to properly match the load to the gun.
Premium ammunition, on the other hand, is loaded to much closer tolerances. Using top-of-the-line bullets made by independent manufacturers like Barnes, Hornady, Nosler, Sierra, Speer and Swift to load their high-end ammo and even these are subjected to additional quality control steps to ensure that every single load is reasonably identical. If your gun will match up to high-grade commercial loads, it's a marriage made in heaven.
Velocity Versus Performance
While the purpose of accurizing a hunting rifle is to obtain better accuracy in hunting conditions, you'll also need to give some thought to matching the projectile to the game. Some bullets build up and maintain superb velocities while others offer lack-luster ballistics in comparison. Set aside the velocity and trajectory tables for a moment and give some thought to what game you'll be hunting during the course of the next season. Deer and even caribou are surprisingly frail when compared to some of North America's heavier game and a light, flat shooting thin skinned bullet will do the job reasonably well. On the other hand, for game like elk and moose, you'll want a heavier, thick skinned projectile that holds together even if it might mean a small sacrifice in ballistics.
As in the case of handloads, I settled on a 150 grain Nosler Partition for the 270-caliber Winchester Model 70 test gun. The next step was finding a handful of shells from each of the ammunition manufacturers in order to find out which of them my off the shelf Winchester 70 would like the best. I managed to find a couple of sets at a local gun store which sold ammunition by the round for just that purpose. A few more sets came from other shooters at the gun club and at the local fish and game club who were willing to trade rounds in order to try different brands. When all was said and done, I had to purchase only one full box of premium 270-caliber ammunition, yet I had six different loadings of 150 grain Partitions to work through the gun. One of them would hopefully match up with my rifle.
How did the final range work on the handloads turn out? As promised, two weeks after our shooting session, Doug dropped by with a brand new set of targets and a 50-round ammo box filled with rows of freshly loaded .270 shells, each of them tipped with a perfect lead point.
"There you go," he announced, pointing at the tight clusters of overlapping holes punched in the paper. "All 150 grain Partitions, just like you asked and you couldn't get better groups with a custom built gun. You have no excuse for missing that buck this fall, but if you wanted to take the project to another level, I'd take a look at the trigger. It's not really as smooth as it could be."
Good counsel and we'll take a look at triggers in part four of this series on accurizing an off-the-shelf hunting rifle.
George Gruenefeld has been hunting big game for over four decades and his travels have taken him to several continents. Most of the time, though, he concentrates his efforts on the Prairies and mountains of Western Canada.