FACTORS IN ACCURACY, Part One: Rifles and Shooting

Factors In Accuracy, Part One: Rifles and Shooting

by John Barsness

AFTER READING one of today’s shooting magazines, many hunters might reasonably conclude that if their rifle isn’t pillar-bedded, custom-barreled, action-blueprinted, target-crowned, chambered for the latest short magnum, and fitted with a trick-reticle, astronomy-grade riflescope, they’ll be absolutely helpless when confronted with a white-tailed deer.

This isn’t so. I own several modern custom rifles and they do kill game, but they are no more necessary to successful deer hunting than a dualed-out, chrome-magged, winch-equipped 4×4 pickup. In fact, over the past decade or so of fooling around with custom rifles, I’ve concluded that the tiny details of their fine construction rank way down the list of factors affecting intrinsic accuracy.

I’m not talking about whether super-fine accuracy makes any difference in the field. It almost never does — but rifle loonies still like to shoot little-bitty groups. (This isn’t a bad thing, because the more we try to shoot little-bitty groups, the more we shoot, and any trigger-pulling helps us shoot better.) Instead I’m talking about the basics that let a hunting rifle shoot not just tiny but consistent groups. And that’s a good thing, whether we’re humping the hills with a classic Savage 99 or the latest stainless-synthetic Midget Mag.

Over the past several decades I’ve also fooled around with a lot of factory rifles, on average about 15 a year — but not usually the rifles almost any manufacturer would happily lend me. Why not? Because rifle makers frown on modification of consignment rifles, and I’ve generally found that changes must be made to allow any rifle to shoot up to its potential. So, in the interests of science, I buy rifles (usually but not always used), fool with them, and then quite often send them on their way after I’ve had my fun. This may seem callous, but otherwise my house would be leaking rifles.

Over the past couple of years I bought 3 used Remington 700’s. At first I was going to have them “blue-printed” and rebarreled, as I’ve had several other 700’s over the past few years, but then decided to shoot them first and see what happened. The trio consisted of a somewhat worn 6mm Remington ADL from the 1960’s, complete with bolt-locking safety and impressed checkering, a mid-1980’s .30-06 ADL in very good shape, and a recent, like-new 7mm Remington Magnum ADL with a synthetic stock.

The 7mm Magnum arrived first. My initial “test” on any bolt-action rifle involves pulling the bolt and looking very carefully at the back of the locking lugs. Both were partially shiny, indicating they seated in their action recesses. Over the decades I’ve occasionally drawn a 700 where one lug didn’t seat, and these always shot relatively poorly. But if both lugs show some seating wear, it’s not a problem. Custom gunsmiths like to have “100% contact” when lapping lugs, but my experience indicates that partial contact works just as well — as we shall see.

I’ve had, uh, mixed results with the cheap “Tupperware” injection-molded stocks most large manufacturers put on their big game rifles. They aren’t stiff enough through the forend, and a stiff forend is essential for repeatable accuracy in any bolt rifle. So I substituted an Acra-Bond laminated stock from Mel Smart (after the unfortunate passing of Mr. Smart, Acra-Bond was purchased and renamed Serengeti Stockworks, www.serengetistockworks.com, (406) 756-2399 ) that had arrived a month earlier.

Over the years I’ve had the best luck getting 700’s to shoot by free-floating the barrel. Luckily, this is easy, even impermanently. Two thicknesses of matchbook-cover cardboard inserted between the front receiver ring and stock normally float a 700’s barrel quite nicely. On factory stocks, you often have to rasp down the hump at the front of the barrel channel that supposedly applies “tip-pressure,” but on Mel’s stock this wasn’t necessary. While the rifle was apart I also adjusted the trigger to a clean 3-pound pull (easy if you know how, but easy to screw up if you don’t, so without prior knowledge, take it to a gunsmith).

After a float-job you should NOT be able to grab the tip of the forend and barrel and force them together. This basic concept escapes even many “accuracy” gunsmiths. If the forend’s limp enough to touch the barrel with hand pressure, the barrel can tap it during the harsh forces of firing. This screws up the consistency of barrel vibrations, causing fliers. (Mel would probably have shot me for floating any barrel in his stock. He firmly believed in full-length bedding, saying that all sorts of crud could get into the channel under a floated barrel, causing weird vibrations. I’ve also had good luck with fully-bedded barrels, but floated this rifle to save time during my experiments.)

After screwing the rifle back together I mounted a brand-new 2.5-10x Leupold LPS scope. Leupold’s original LPS’s had their optical problems, but these new scopes are as perfect as any I’ve seen. The view is so flat and bright it’s like looking out a newly-scrubbed picture window.

After mounting the scope I tested a couple of factors that can also affect accuracy, especially tiny groups at 100 yards. The first was parallax. I sincerely believe this is one of the most common reasons many shooters are dissatisfied with factory-rifle accuracy.

Parallax, in case you don’t know, is the apparent shift of the reticle across the target when the rifle’s held still and you move your aiming eye back and forth behind the scope. It’s caused by the reticle not being exactly in the focal plane inside the scope.

All scopes show parallax at some range. Big game scopes of 10x or under are normally factory adjusted to eliminate parallax at 200 yards. At shorter and longer ranges there’ll be some parallax, just how much depending on the scope. (In my experience this is the usual reason some rifles shoot as well or better at 200 yards than 100, a phenomenon usually attributed to the spinning bullet “going to sleep.” Maybe so but, most of the time, fitting a scope without parallax at 100 yards makes the rifle shoot better at 100 than 200.) Many scopes show noticeable parallax at 100 yards. I once tested a 2-8x variable from a major manufacturer that when set on 6x had 3-4 inches of parallax at 100 yards, though it was perfect at 2x and 8x.

Scopes of more than 10x normally include parallax adjustment, either a focusing objective lens or a knob on the side of the windage/elevation turret. But the range markings on many focusing objectives often don’t match up with reality. Unless you check you won’t know.

You check either type of scope by aiming your rifle at something 100 yards away, holding it very steady, and move your aiming eye back and forth. I normally do this by clamping the rifle in a vise in my workshop, then aiming the scope at the shingle pattern on a neighbor’s roof, but you can also do it while the rifle’s resting on sandbags at the range. If there’s any noticeable shift of the reticle across the target, you’ve got parallax problems, which definitely affect your rifle’s grouping ability.

What to do? Scopes under 10x can sometimes be helped by refocusing the eyepiece. According to many “experts,” this doesn’t affect parallax, but I’ve proven to myself that it does. Remember, parallax is caused by the reticle being slightly out of the focal plane. This is why bigger scopes have a focusing objective; when it’s screwed in and out, the focal plane changes slightly inside the scope.

The same thing happens to a lesser extent when focusing the eyepiece. This is easily noticeable when turning a “European,” quick-adjustable eyepiece, but also occurs with a typical “American” eyepiece that turns very slowly on fine threads.

With a scope featuring a focusing objective or turret-mounted parallax adjustment, just turn the thing until apparent parallax disappears. Pay no attention to the markings on the adjustments except for preliminary setting.

Quite often you’ll run into scopes that simply can’t be adjusted to eliminate parallax at 100 yards. I have a 3-12x Swarovski with their TDS reticle that’s perfect for long-range prairie dogs, but it’s parallax-free only at 200 yards and beyond. This doesn’t matter when shooting PD’s, but does matter when testing ammo at 100. I substitute another scope for handload workup and ammo testing, then use the Swarovski in the field.

But some scopes are simply defective at any range, and should be returned to the manufacturer. Some will claim the scope’s within their specs, in which case you should switch brands.

In the case of the 7mm Remington Magnum, the LPS scope checked out perfectly at 100 yards, so I put one of Leupold’s new (and inexpensive) ScopeSmith magnetic boresighters on the muzzle and tried the scope’s adjustments. This is far easier (and cheaper) to do with a collimator than actually shooting the rifle after clicking windage. If the adjustments waver across a collimator screen, then I know there’ll probably be accuracy problems too. In this case the LPS’s adjustments worked perfectly.

Next, I loaded up a dozen rounds of ammo using 150-grain Nosler Ballistic Tips, brass that had been previously fired once in another rifle, Federal 215 Match primers, and IMR4350. This took over an hour, because I used every accuracy trick available. (There isn’t space or sense to describe them here, but I’ll do that in Part 2 of this piece, in the next issue of Handloader.) The most recent Nosler manual indicated that IMR4831 was the most accurate powder with this bullet, but I didn’t have any, so tried IMR4350, essentially a slightly faster version of the same powder.

Then I waited for a calm morning to go to the range. While you can sight-in adequately on a pretty windy day, you simply cannot test a rifle/ammo combo for accuracy in an erratic breeze unless you have several wind flags set up on the range and know how to use them. I usually use at least 2 on my 100-yard range, but even then prefer a calm day, because the bench sits out in the open while the target’s up a little draw. Wind tends to whirl around in the draw, and the flags whirl in all sorts of directions. Early mornings are often dead calm, so by 8:00 one sunny September day I was at the range with several rifles.

The bench is a massive beast made of redwood, the legs 6-inch posts set on concrete blocks. This is also necessary for small groups; while I’ve shot small clusters from pickup tailgates, a heavy bench works much better. The front rest was a sandbag tied tightly to a heavy bench tripod, the rear one of Melvin Forbes’ Bench Wizards, a winged sandbag that clamps around the butt. It’s very broad, which along with its weight helps take the sting out of hard kickers, and holds the butt quite precisely.

First I shot at 25 yards to zero the collimated scope. This preliminary shooting of a newly stocked and scoped rifle also helps settle any slight play in stock or scope. In fact, I’ve found most new scopes need a little “break-in” before the bearing surfaces of the adjustments settle in.

After 25-yard zeroing, I fiddled around with both front and rear rests until the reticle quadrisected the 100-yard bull without my help, thus eliminating any strain in the rifle. By this time the barrel had cooled down again and I started shooting for group, trying to hold the rifle with the same tension from shot to shot. The first bullet hole appeared just above the bull, slightly widening after the second shot. The third shot landed just far enough away to show white paper between it and the first elongated hole.

That was the starting load, using 61 grains of IMR4350. I shot a couple of other rifles, then hiked over and marked the target. The 7mm’s first group looked to be .5 inch or less. Not bad for a start! I went back and shot 3 rounds loaded with 62 grains. These spread a little more, but were still obviously under .75 inch. The third group, with 63 grains, was the smallest. At home I measured them with a dial caliper: .48, .68 and .37 inch. Obviously this was one accurate rifle.

The next day, just to see what would happen, I loaded up 9 rounds with the 63-grain load. While one group isn’t enough to base a handload on, my Chrony recorded that the 63-grain load had by far the smallest velocity spread, only 14 fps, a good secondary indication of a reliable load.

Then I went to the range and shot 3 more groups — but during this session an erratic breeze kicked up. The first group, shot in the mildest breeze with very careful attention to the wind flags, measured .27, but the next two each spread 1.03 inch. In both, two shots nearly touched, and in almost exactly the same relationship to the bull as the .27 group. But the third shot was an inch out, once high and once to the left.

Again, shot-to-shot velocity variation was low; combined with the .27 group I was pretty well satisfied that this 7mm Magnum shot like most .223’s. The second and third groups only re-proved what I knew before: it’s hard to shoot tiny groups in an erratic wind.

When the 6mm Remington and .30-06 came home I went through the same basic procedure. In each case bolt-lug wear indicated satisfactory seating, and the triggers needed adjusting.

The 6mm’s factory stock was very stiff through the forend, so I just free-floated the barrel, mounted a 2.5-10x Bausch & Lomb (now Bushnell) Model 4200 Elite that had proven itself on several rifles, and started loading ammo using new Winchester brass and CCI 200 primers. Again, I only tried a single powder, Alliant Reloder 19, since the Nosler manual indicated it worked best in the cartridge, and 2 bullets, the 87-grain Hornady V-Max and 95-grain Nosler Partition. Aside from a single 1.75 inch group with the V-Max’s, shot after reassembling the rifle after glass-bedding the receiver, all groups went under an inch:

87 V-Max, 48 and 49 grains of R19: .56, ,67, .61 (all 3 shots, avg. .61)
95 Partition, 45 grains of R19: .72, .35 (all 3 shots, avg. .535)
95 Partition, 46 grains R19: .90 (5 shots)

The .30-06’s factory stock had a much longer forend than the old 6mm’s, which could not be free-floated satisfactorily. So I glass-bedded this barreled action in the Acra-Bond laminate. I also tried Reloder 19 in this rifle, with 180-grain Nosler Partitions, Norma cases and Federal 210 primers.

After 3 fouling and sighting shots with 58 grains of powder, the 59-grain load resulted in a nice triangular group of just over an inch, with velocity spreading only 8 fps. Three shots with 60 grains measured 1.43 inches, with a velocity spread of 25 fps. Muzzle velocity with the 59-grain load was about 2750, about what Alliant’s data indicated I should expect from a 22″ barrel. Two more groups resulted in a 3-group average of .87 inch.

I use Remington 700’s as an example because they have a reputation as one of the most accurate factory rifles. Some attribute the average 700’s accuracy to fast lock-time, or the stiff cylindrical action. These undoubtedly contribute, but the basic 700 also has a pretty stout barrel. Those I’ve measured have averaged about .660 inch at the muzzle, equivalent to what barrel makers call a #4 contour.

Over the years, my notes with many bolt actions indicate that barrels with .150 inch of steel outside the bore at the muzzle sometimes shoot well and sometimes don’t. But if there’s substantially more steel around the hole, at least .18 inch, then most barrels shoot very well.

In 6mm this means a .600 inch muzzle, in .270 or 7mm a .640 inch muzzle, and in .30 caliber a .670 muzzle (which may be partly why the .30-06 didn’t shoot quite so well as the 6mm and 7mm. So the standard Model 700 barrel provides lots of steel around the bore in the calibers most of us shoot. The lighter-barreled Model 700 Mountain Rifle can also shoot quite well, but tends to be more persnickety about ammo.

I’ve owned a bunch of 700’s over the years, along with several custom rifles based on the 700 action. My conclusion is that unless you want some special variation not supplied by Remington — such as a non-standard chamber or an extremely light rifle — the average “tuned” 700 will shoot nearly as well as most custom rifles. You may have to scrub the jacket fouling out of the 700’s hammer-forged barrel more often than you do from a Hart or Lilja — but then again you may not, especially after polishing a Remington barrel a few times with JB Compound.

The same basic principles apply to any bolt-action rifle, with a few minor variations. If you prefer (as I sometimes do) to completely the bed the forend, it’s easy to do with Brownell’s Acra-Glas Gel. You can even glass some up-pressure into the forend tip. After full-length bedding the barrel and letting the glass cure, place a couple of strips of duct tape across the barrel channel, 2 inches back from the forend tip. Glass-bed the tip again, making sure to scrunch the action screws down tight. Presto! Forend pressure! I’ve only had to do this on a few rifles with very thin barrels, most notably a Ruger 77 rebarreled to .358 Winchester with a Hart that measures .600 across the muzzle, leaving only about .120 inch of steel outside the bore. With lots of upward pressure, it also shoots under an inch for 3 shots at 100 yards.

Two-piece stocks work a little differently. Here you must be careful that the buttstock’s tight against the rear of the action, and the forend isn’t tight against the front of the action. Once that’s arranged, many single-shot and even lever guns will shoot right alongside bolt rifles.

A recent accidental triumph is a Savage 99 made about 1950, a standard EG in .300 Savage with a fairly stout 24″ barrel. I bought it for $250 to get the classic Redfield peep sight it wore, intending to sell the rifle again for $250 after I got the sight off. Hunting season had started, however, and I was too busy to push the rifle, and then an unemployed friend needed a rifle to kill some meat for his family, and of course didn’t have money to buy one. I mounted a 1-3x Weaver on the 99, grabbed some Federal 180 factorys, and went to the range. The first 3 shots at 50 yards punched one tight cloverleaf, and even with the low-power scope, the next 3 at 100 went a little over an inch. Hmm.

After the rifle was returned I fixed the 5-pound trigger (again, easy to do if you know how) and mounted a 3-9x Zeiss Conquest, with a focus ring that could be adjusted to totally eliminate parallax at 100 yards. Then I loaded up my favorite .300 deer load, 42 grains of IMR4895 and the 150 Hornady, in some once-fired Winchester cases with CCI 200’s.

The first 3-shot group went .91 inch, the second .59. After letting the rifle cool, I shot twice more at the .91 group, the 2 bullets landing inside the first 3 holes. Zowie! I do believe this rifle will do for about any deer hunting.

Many 99’s shoot like that and, again, the reasons are simple. The action is very stiff, essentially a long block of steel, and the threaded portion of a 99’s barrel is longer (nearly an inch) than almost any other modern rifle. Firmly screw a stiff barrel to a stiff action, then attach a forend without any strain, and the rifle should shoot.

Real accuracy gunsmiths can list a dozen highly technical features for making rifles shoot better, from aluminum pillars to 11-degree “target crowns.” But my experience has been that almost any big game rifle can shoot 100 yard, 3-shot groups under an inch with the right scope, a decent trigger, the correct bedding — and the right ammo. We’ll look more closely at ammo next month in Handloader.



Reprinted from RIFLE magazine with permission from Wolfe Publishing Company, 2625 Stearman Drive, Prescott, AZ 86301, 1-800-899-7810, www.riflemag.com.