|Gun Report:||July 1996|
A-Bolt II BOSS
I wasn't shopping around for a Browning A-Bolt. I wasn't even in the market for a bolt-action. My finances certainly weren't ready for a new firearm, either. But from the first day I saw it, until I brought it home a week later, it was as though the Siren's song was playing in my mind, calling to me.
All I wanted was some bore cleaner, that day in late June of 1995 when I innocently strolled in to Phoenix Sports. But there it was. The Greywolf is a special edition of the Browning A-Bolt II that was built in limited numbers in 1994. It isn't in the 1994, 1995, or 1996 Browning catalogs. This was the last one Phoenix Sports had, and the last one they were going to have. What's special about it, is that it features stainless steel metalwork in a semi gloss finished walnut stock. The stock shows some modest marble fudge swirl in the chocolate colored walnut. The matte-finish stainless steel sets off beautifully against the dark wood.
Standard catalog versions of the Browning A-Bolt include stainless in black synthetic and blued steel in walnut. Though all Browning had to do to come up with this version is mix and match a little, the Greywolf's stock is a little bit different than the standard walnut stocks for the cataloged guns.
You'll believe that gun-lust overcame ration and reason when I tell you that this special edition came at a $200 premium over the catalog guns. And because it was still on the shelf in mid-1995 further proves that gun-lust can be a very personal thing. Many shooters passed this one by, without lust overtaking reason, before I came upon it.
This particular sample was in .30-06 caliber. At the time, I was probably a little more inclined toward a .270 or a .280, but now that it's mine, it's perfect.
As I examined it at the counter, I noticed a number of features of the A-Bolt that particularly appealed to me. The A-Bolt features a two-position sliding tang safety, just like that on most over/under shotguns -- my absolute favorite place for a safety. The bolt is a three-lugged affair, and features a short bolt lift of only 60°. The A-Bolt also features a detachable box magazine which mounts on the hinge-open floor plate. The magazine can be loaded traditionally through the top of the receiver with the bolt slid back, or the floor plate can be opened, allowing the empty magazine to be pulled off and replaced with a fresh one. Still one more method is to open the floor plate, allowing floor plate with magazine attached to hang vertically from the bottom of the gun. Now the magazine can be topped off with the bolt still closed on a chambered round.
The A-Bolt originally caught my attention with all the hoopla in the gun press surrounding Browning's introduction of the BOSS accurizing device in 1994, and indeed, this rifle wears a BOSS. This was a particularly interesting feature for me. The barrel is of a thin, sporter weight profile, and is 22" long including the length of the BOSS. The rifle weighs right around 7 pounds, out of the box.
Well now I had to come up with a purpose for it, so I convinced myself, and then my wife, that since no rifle in my inventory was much good out past 150 yards, I needed a "long range" deer rifle. She recognized my intensity, having seen it in me before, and knew that nothing she could say would stop me, so she resignedly gave me the go ahead.
No, I couldn't afford it. But the stronger feeling was that I couldn't afford to let it slip away, either. I began wondering what kind of madness had overtaken me. It was as though I was acting under forces that I could not control, and did not understand.
Two other refinements to the A-Bolt
were introduced in 1994, besides the BOSS, that Browning felt were significant
enough to change the rifle's name from A-Bolt to A-Bolt II. First, they
chrome-plated the trigger sear for a crisper let-off, and second, the bolt was
modified with a non-rotating sleeve that rides the inner receiver rails for a
non-binding bolt-throw. But the big news, of course, was the BOSS.
A short refresher course on the BOSS is in order here. The BOSS (Ballistic
Optimizing Shooting System) is a three-piece muzzle-end attachment consisting
of a barrel weight, a muzzle brake section, and a micrometer scaled adjustment
collar that Browning calls the locknut. The patented device operates over an
adjustment span of about one inch for the purpose of modifying barrel harmonics
as a means of tuning accuracy. The theory goes that a barrel "whips" as a
bullet passes through it, and that by tuning the BOSS in or out, a "sweet spot"
can be found such that the barrel is either in a peak or valley of a vibration
cycle as the bullet leaves the barrel. At a peak or valley, the barrel is
momentarily motionless, and therefore, a series of shots will be at their most
consistent at this sweet spot.
A short refresher course on the BOSS is in order here. The BOSS (Ballistic Optimizing Shooting System) is a three-piece muzzle-end attachment consisting of a barrel weight, a muzzle brake section, and a micrometer scaled adjustment collar that Browning calls the locknut. The patented device operates over an adjustment span of about one inch for the purpose of modifying barrel harmonics as a means of tuning accuracy. The theory goes that a barrel "whips" as a bullet passes through it, and that by tuning the BOSS in or out, a "sweet spot" can be found such that the barrel is either in a peak or valley of a vibration cycle as the bullet leaves the barrel. At a peak or valley, the barrel is momentarily motionless, and therefore, a series of shots will be at their most consistent at this sweet spot.
Apparently, the largest variable affecting barrel harmonics, and therefore the tuning of the BOSS, is bullet weight. In the instruction manual, suggested sweet spots are given only for bullet weights, not for particular loads from particular manufacturers. But it could also simply be that factory ballistics are similar enough for any given bullet weight. Certain suggested settings are asterisked with the note that "Premium grade ammunition of the same load require a different sweet spot setting than standard grade ammunition," with no further guidance. This is the 1994 Browning BOSS manual. Maybe '95 or '96 manuals, or the Winchester manuals are more helpful.
The bedding is also part of the BOSS system. The barrel is free floated from the receiver forward, but the action itself is bedded upon two blocks of a hard rubber compound of a specific durometer (hardness/softness). This bedding system, Browning found, was the secret to getting the BOSS system to give repeatable results.
At the BOSS's introduction, Browning invited most of the big names in the gun press out to Thermopolis, Wyoming, to proudly demonstrate their new invention. The gun writers universally sung the praises of the device as they played around with different settings and watched their groups open and shrink.
While I was intrigued by the theory and the good press, there remained some unanswered questions in my engineer's mind, based on what appeared to be the rather haphazard testing methodology employed by the gun writers. In none of the articles did I see a report on a comprehensive shooting test of the kind I knew had to be done to independently validate Browning's claims. Such a test program would require a lot of time and a lot of lead sent down range, with carefully kept records, and a consistent approach to the shooting.
I've had people ask me, "Well, how is that BOSS working out for you?" Despite my enthusiasm for this particular rifle, I never could bring myself to tell the inquirer, "Oh it's the greatest thing since sliced bread!" or whatever other gushing praise you could think of. The reason was, because I really didn't know. I suspect that most BOSS owners never will take the time to perform an honest shooting appraisal and reach their own conclusions.
I think you can guess where this is leading by now. Now I don't have a rifle company or a gun magazine buying my ammo, so I can't say that the test program I have just completed is as comprehensive as might be desired, but for the first time in print (that I know of), you, the lucky readers of the SPORTSMAN, are going to be presented with hard data and statistics on whether or not the BOSS really works.
My first experiences shooting the new
rifle were satisfying enough, so I didn't bother with a lot of fiddling around
with the BOSS. I mounted a silver finish Simmons 3.5-10x40mm Whitetail
Classic scope on silver finish Leupold bases and rings.
For economy, since I was not yet a reloader, I standardized on Remington
Core-Lokt 150 grain factory loads. These were printing 3 shot groups of
between 1 and 1½ inches at 100 yards with the recommended sweet spot setting
of 2.5. Good enough for hunting purposes.
And the hunt gods were good enough to smile upon me and the Greywolf in
November as we knocked down one coyote and one mule deer. But as I have
mentioned previously in these pages, the Remington Core-Lokt broke up upon
hitting a rib on entrance and failed to exit. It's hard to argue with
success, however, as the deer was anchored where he stood. So while I want
an exit wound next time, I still want a bullet with the dynamic expansion of
My lovely wife got me a reloading setup for Christmas, so now I can pick and
choose the exact performance I want. First of all, I want a slightly heavier
bullet to increase the odds for exit. I settled on the 165 grain weight.
But if I choose a bullet that holds together too well, I worry that the deer
may not drop on the spot. Like most hunters, I hate hunting after the shot.
My BOSS manual does not list a suggested sweet spot for 165 grain projectiles,
so I knew I would have to find it myself. Someone suggested that I give
Browning customer service a call to see if they now have the data for a 165
grain sweet spot. But that wouldn't be nearly as much fun. Besides, as they
say, every rifle is a law unto itself, so I would still have to do some
experimenting anyway. So I decided to go whole hog and run the experiment
At about the time I was deciding to start this test program, I became aware
of the National BOSS Shootout, a contest being sponsored by Browning and
Winchester to show what BOSS-equipped rifles can do. (USRAC, the company
who makes Winchester brand rifles, is a corporate sister to Browning, and
started putting the BOSS on Winchester rifles in 1995.) The format for
entry is best 5-shot group. This decided the group size I would use in my
test. I figured that with the number of groups I needed to shoot in order
to draw a statistically valid conclusion, that the chances were pretty good
that at least one group could turn out pretty darn good.
The BOSS is calibrated in 1/10 turn increments from 0.0 to 10.0. I
certainly was not going to test each 1/10 turn setting! What I settled
on was testing each ½ turn setting from 1.0 to 9.0, leaving off the extreme
ends of the range. This is 17 settings.
For economy, since I was not yet a reloader, I standardized on Remington Core-Lokt 150 grain factory loads. These were printing 3 shot groups of between 1 and 1½ inches at 100 yards with the recommended sweet spot setting of 2.5. Good enough for hunting purposes.
And the hunt gods were good enough to smile upon me and the Greywolf in November as we knocked down one coyote and one mule deer. But as I have mentioned previously in these pages, the Remington Core-Lokt broke up upon hitting a rib on entrance and failed to exit. It's hard to argue with success, however, as the deer was anchored where he stood. So while I want an exit wound next time, I still want a bullet with the dynamic expansion of that Core-Lokt.
My lovely wife got me a reloading setup for Christmas, so now I can pick and choose the exact performance I want. First of all, I want a slightly heavier bullet to increase the odds for exit. I settled on the 165 grain weight. But if I choose a bullet that holds together too well, I worry that the deer may not drop on the spot. Like most hunters, I hate hunting after the shot.
My BOSS manual does not list a suggested sweet spot for 165 grain projectiles, so I knew I would have to find it myself. Someone suggested that I give Browning customer service a call to see if they now have the data for a 165 grain sweet spot. But that wouldn't be nearly as much fun. Besides, as they say, every rifle is a law unto itself, so I would still have to do some experimenting anyway. So I decided to go whole hog and run the experiment myself.
At about the time I was deciding to start this test program, I became aware of the National BOSS Shootout, a contest being sponsored by Browning and Winchester to show what BOSS-equipped rifles can do. (USRAC, the company who makes Winchester brand rifles, is a corporate sister to Browning, and started putting the BOSS on Winchester rifles in 1995.) The format for entry is best 5-shot group. This decided the group size I would use in my test. I figured that with the number of groups I needed to shoot in order to draw a statistically valid conclusion, that the chances were pretty good that at least one group could turn out pretty darn good.
The BOSS is calibrated in 1/10 turn increments from 0.0 to 10.0. I certainly was not going to test each 1/10 turn setting! What I settled on was testing each ½ turn setting from 1.0 to 9.0, leaving off the extreme ends of the range. This is 17 settings.
The A-Bolt's detachable magazine attaches
to the hinged floor plate
One group at each setting is statistically meaningless, and so, worthless for the purpose of drawing conclusions. It appears that what most of the gun writers in Thermopolis were doing at the BOSS rollout was exactly that. One group - twist - another group - better - must be working. What you really need to do is fire a number of groups at each setting and average them.
I decided to shoot 5, 5-shot groups at each setting. Yeah, more groups would have been better, but I'm buying my own ammo, and besides, I had a deadline. Entries to the BOSS contest were due by July 15. As usual, time and money are the limiting factors.
Have you been adding this up? I'm up to 425 shots already. Furthermore, my plan was to re-shoot the setting that looked like the sweet spot, plus ¼ turn increments on either side. That's 75 more shots for a total of 500 shots, 100 groups total. Whew!
This is something I never would have contemplated without handloading. It's true what they say, that when you start reloading, you won't actually save any money, because you'll find reasons to shoot more! I averaged 100 shots per week for five weeks. That's about all I could turn out on my single stage press in a week, working at it on weekday evenings. My load was 54.5 grains of IMR 4350, Remington brass, Federal #210 primers, and Hornady 165 gr. BTSP's.
Being a long grain rifle powder, IMR 4350 doesn't meter too consistently, so each charge was weighed individually. 54.5 grains is not a pedal-to-the-metal load for 165 grain bullets -- it's kinda medium velocity. I did not want to be playing with maximum or near maximum loads here in Phoenix in the hottest part of the year.
100 rounds of .30-06 off the bench in one morning . . . The gun writers say that they don't know anyone who considers the recoil of a .30-06 excessive. Well they live and breathe in a different world than I do. Most of the shooters I know are very respectful of the recoil of a .30-06. Here's another area where the BOSS shines.
When shooters ask me about the recoil of my Browning, my pat answer is, "It's a pussycat." And I'm certainly not saying that out of a sense of macho. Browning rates the recoil reduction of the BOSS on a .30-06 at 34%. Plus, the rifle also sports a very nice recoil pad on the butt. I've actually fired as many as 135 rounds in a day, in a tee-shirt, off the bench, and never came home with a sore shoulder. Think about it. That really says something.
As pleasant as the gun is to the shooter behind the butt pad, it's quite the bone rattler to people around the gun. I've stood by while buddies have tried a couple of shots, and the effect to bystanders is, shall we say, exhilarating? Inevitably, people will say things like, "Wow!, What caliber is that?", or "What sorta belted magnum are you shooting?", or "That's a nice cannon ya got there." To which I reply, "Aw shucks, it's only a .30-06." This is the kind of thing that appeals to the kid in me who used to run a straight-pipe on his 4-stroke mini-cycle, terrorizing the neighborhood.
There was one memorable morning, every time I took a shot, the alarm on the car parked 40 to 50 feet behind me would go off, reset in about 30 seconds, and go off again at the next shot.
Then there was the young family who started to unpack their pea shooter handguns at the bench next to me, at a moment when I was allowing the barrel to cool. I figured that the best way to warn them was with a demonstration. Without casting a glance in their direction, I casually and coolly single loaded one of my fouling loads into the breech, pointed at my sighting target and squeezed. VAVOOOM! Before I could lift my head from the stock, I heard Dad saying behind me, "Maybe we should move down a bench or two." They moved down about six benches. Great fun.
Despite the recoil reduction, it's still not as easy as you would think to maintain your concentration, shot after shot, for 100 shots, even though benchrested. I still have to fight the tendency to flinch. I caught myself more times than I like to admit, closing my eyes and yanking.
Even when I thought I did everything right, all too often, it would happen that I'd shoot my first three shots fairly tight, and the fourth one goes wide - or worse yet, the fifth one. Shooting a tight 5-shot group somehow seems a lot tougher than making a tight 3-shot cluster. Yeah, some of it could be barrel heating. In general, I was shooting between 7 and 10 shots between cease-fires at the Ben Avery public range.
I decided to count every shot on the target, even when I knew a flyer was the shooter's fault. I figured that flyers would average out anyway, and that it would be too much of a hassle to try and keep track of the my-fault flyers. Besides, I believe that every shot has some degree of shooter error in it. Since it is a matter of degree, not of did-I-or-didn't-I, how do you decide where to draw the line? Counting every shot made the job much simpler.
My first session out was rather disappointing. My average group size was running 1¾ to 2 inches. Not at all what I expected out of the rifle. My measurement technique was to take my targets home, where I could measure them in a controlled environment with dial calipers. I eyeballed the centers of the two holes furthest apart in each group, and rounded to the nearest .005".
About midway through that first morning's shooting, I did discover that my action screws were loose. In the past, I found that loose action screws can have a significant effect on accuracy. I borrowed some screwdrivers from the shooter next to me and tightened them the best I could. This did seem to help a little, but not dramatically.
Another thing had been bothering me since the rifle was new. The barrel is supposed to be free floating, but the right side of the fore-end wood, near the tip of the stock, was lightly touching the barrel. That afternoon, I finally decided to do something about it. I removed the barreled action from the stock, wrapped some 100 grit sandpaper around a 1" wooden dowel and opened up the barrel channel, concentrating on the front-right side. And while I was fiddling, I lightened the trigger to minimum pull weight (screw adjustment to 3½ pounds), and finished by making sure that the action screws were cranked down real tight with my gunsmith screwdriver set.
My next range session was a bit more satisfying as I brought the average group size down to 1½". Not spectacular, but I wasn't yet worrying, figuring that I had not yet found the sweet spot. Gee, Weatherby only guarantees that their rifles will shoot 1½" using Weatherby factory ammo.
Let's take a look now at the data. The spreadsheet starts with data for BOSS settings from 1.0 to 9.0, and then more trials labeled "Supplemental Settings Fired." On the first day I fired three settings (75 rounds) and the rest of the data was taken four settings per day (100 rounds).
Looking now at the graph, we see data connected by lines, and then points hanging out in space by themselves. The connected data is the original course of fire, and the unconnected data points are those "Supplemental Settings Fired." The graph shows that a funny thing happened for settings 7.0 through 9.0. All of a sudden, a significant improvement occurs in the average group size, and it stays very steady over the range. A look at the standard deviation data shows that although these settings all have the same average, they are not equally "sweet."
On the day I finished shooting settings 6.5 through 8.0, I measured my groups and entered the data into the spreadsheet. When I looked at the chart, I noticed the sudden jump downward in average group size, and it caused me to question whether or not something was going on here. Thinking about it, I did make some subtle changes in shooting procedure around setting 6.5 to 7.0. I finally found a stable and comfortable hold on my sandbags, and instead of cleaning the barrel between each group of 5 shots, I had switched to cleaning once every 10 shots, and started firing a fouling shot before starting the next group.
I found myself questioning whether I had just invalidated all my shooting from settings 1.0 to 6.5! Believe it or not, I was starting to get quite weary of the shoot100 - reload100 - shoot100 - reload100 cycle I had gotten into for the past several weeks, and did not look forward to doing all that shooting over again.
I decided to finish the course, and then take another look at the data to see what I wanted to do. Well, I only needed two more settings to finish the course, but I could do four. I didn't want to waste a trip to the range, so I looked at the data to see what two settings deserved a re-shoot. First, setting 4.5 looked like a particularly "sour" spot with a high average group size and a high standard deviation. Was it really that bad, or was it just me on that day? Second, setting 7.0 yielded my best single group of all; 5 shots in only .445"! And it also had the lowest group average. But the deviation was relatively high for the 5 groups at this setting. This one deserved some further investigation.
My original plan was to determine the sweet spot and refire it for verification, then probe ¼ turn on either side. But in real life, things seldom work to plan. When I saw the data for the completed course of fire, it looked like I had a "sweet band", rather than simply a sweet spot. And the previous "sour spot" looked like it wasn't that sour after all, because a second chance had brought the group average way down, below the overall average of the original course. Standard deviation for the 4.5 BOSS setting also came down significantly.
Meanwhile, the group average for setting 7.0 got slightly higher, on a par with the other members of the "sweet band", and standard deviation also dropped down to fall in line with the others in the sweet band. These two re-shoot results tended to confirm that there was a significant difference between the shooting I did for settings 1.0 through 6.5, and the shooting for 7.0 through 9.0.
Moan. Groan. The last thing I wanted to do was reshoot 1.0 through 6.5, but I had a decision to make. I was prepared to go out one more time, 100 more shots, 20 more groups, 4 more BOSS settings. I wanted to be done. What 4 settings should I re-shoot that would settle the matter and decide my sweet spot?
My best setting between 1.0 to 6.5 was 3.5, with both a small average group (1.341") and a small SD (.224"). Using the techniques of the steadier hold, cleaning between every other group, and firing a fouling shot after cleaning, could I improve on my previous results for 3.5?
In the "sweet band", I had already re-shot 7.0. Setting 8.0 looked very promising also. It had a low figure for average group, but more importantly, the lowest SD. Standard deviation provides a measure of the reliability of the setting to produce groups close to whatever it's average is. The lower, the better.
To get a feel for how bad the earlier shooting really was, I wanted to reshoot a sample of the earlier settings. Almost arbitrarily I chose 1.5 and 5.0. A second look at these settings, plus the others I had already chosen for a second look, would give me a broad second sampling of the entire range, without actually re-shooting everything twice.
I was quite pleased with the results of the last four re-shot BOSS settings. If you mentally connect the re-shoot dots on the graph, the trend mirrors the original course, just a little lower overall. It also shows that 3.5 is a viable contender for title of Sweet Spot. Actually, I had three contenders for Sweet Spot; 3.5, 7.0, and 8.0. What was amazing about the re-shoot of 8.0, is that both average group and SD came out almost exactly the same as when they were first shot.
To decide my sweet spot, I calculated the overall 10-group average and standard deviation for the three contending sweet spots. Although setting 7.0 gets the nod for best average group of 1.198", I hereby award the title of Sweet Spot for 165 Grain Projectiles to BOSS setting 8.0, based on a second best average group size of 1.242", and a remarkably stable standard deviation of only .203".
And yes, of the 115 5-shot groups fired, setting 7.0's best group of .445" was the one that was sent in to the National BOSS Shootout as my contest entry. I guess I'll find out soon enough whether it's a contender.
5 shots in .445 inches!
(Those are 1/2" grid squares)
Well, boys and girls, there it is. Does the BOSS live up to it's hype? That's for you to decide. For the first time, you've got some hard, independent data to ponder. In my test, average group sizes ranged from 1.983" to 1.117", a difference of .866", 76% of the smaller number. Yes, some of that larger number is due to shooter error. The only way to avoid that is to perform the test in a shooting tunnel with a machine rest.
For me, the test was a lot of fun. Blame it on my inquiring, analytical mind. I was hoping to find a setting with an average group size under one inch, for bragging purposes, of course. But average 1¼ inch groups at optimum BOSS settings are nothing to be ashamed of, that's for sure!
When I started, I didn't think that standard deviation would play such a large part in evaluating the data. I started calculating it almost as an afterthought. But once I started plotting it, and coming to an understanding of how it related to the groups I was firing, I came to realize it's importance. What good is a low group average if you don't know whether the next group you shoot will be a small one or a large one? With a low SD, you know within a reasonably narrow band, how large the next group will be.
After last November's hunt, my rifle was no longer beautifully virgin. Each day in the field, I tried to protect it as best I could, but it now sports some minor dings and scratches, and a scuffed finish in a couple of spots. It was a tough thing, to accept these first blemishes. But as every hunter knows, these marks are what fond memories are made of.
I once remarked to a fellow hunter that there are two types of beautiful rifles; those that are made that way, and those that earn the title through success in the hunting fields. Mine was made that way, but it is also well on its way to achieving its own inner beauty the old fashioned way.
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