We build a lot of exceptionally accurate rifles in our shop. To date, all of these guns have had 11 degree crowns or Vais brakes on the end of their barrels. In fact, even the guns equipped with Vais brakes have small 11 degree crowns inside the brake; so really, all of our guns have had 11 degree crowns. This allegiance to the 11 degree crown has occurred as much by default as by design. Years ago, my husband cut an 11 degree crown on the first hunting rifle he ever built; a .300 Win. Mag. that placed its first three 210g Berger’s into 0.23" @ 100 yards. Success begets success and the 11 degree crown became King in our shop. We never looked back.
Well, truth be told, perhaps we have glanced over our shoulders just a time or two. For instance, I definitely did a double take when a perpetually disorganized friend whacked off the end of his barrel with a hacksaw late one Friday night, and then proceeded to place in the top five at the weekend tactical shoot! Somehow that just didn’t seem right!
I also took more than a cursory peek at all the guns at the last “short-range” match I visited. Surprisingly, (at least to me) the old 11 degree standby is rapidly being usurped by the straight 90 and recessed 90 degree crowns! What heresy!
Unexpectedly, I also spied a tidbit of crown counsel on a Richard Franklin metal working video I purchased. It seems that the eminent Mr. Franklin had a habit of putting deeply recessed 90 degree crowns on many of his guns – a process he referred to as the “quiet crown”- and all those guns shot very well indeed. Hmmm…..
Finally, I was recently visually assaulted by the “Over-Rated Crown” article that appeared in the March issue of Precision Shooting magazine. (The Over-Rated Crown, by Alan Marshall, 3/11.) The abuse Mr. Marshall inflicted on the crowns featured in his article was almost painful to view; yet the guns kept shooting reasonably well. Some of those guns even shot better groups with the damaged crowns than with the “good” crowns! What the heck? Could it be that our meticulously cut, anal retentive, perfectly formed 11 degree crowns were superfluous? I decided to find out. In fact, being a bonafide accuracy freak, I needed to find out.
Luckily, for some unknown and inexplicable reason, we found ourselves in possession of an “extra” Krieger Standard Palma .308 barrel. Now although we maintain an inventory of 30 to 50 barrels at any given time, all of those barrels are usually dedicated to some future project. So where this “extra” oddball, 31.5" long, 1-11" twist, tight .298" x .3075" barrel came from is anyone’s guess. Considering what they cost, hopefully they are breeding on the rack. The point is, I had an “extra” barrel that was extra long and perfectly suited for some serious crown contortions and muzzle manipulations. (Possibly it came from Bruno Shooters Supply.)
Not knowing how this experiment might turn out, and fearing the worst, I decided to build a relatively inexpensive test gun. No McMillan stock or BAT action for this questionable venture. I used a Rem. 700, stainless, short action that my husband had previously blue-printed and fit with an after-market PTG fluted bolt and a Holland Tig-welded handle. The barrel was chambered with a PTG minimum spec., factory load, .343" neck, .308 Winchester reamer. Then, I turned the barrel around in the lathe, inserted a piloted PTG range rod and indicated both ends of the rod as close to absolute zero run-out as possible. I then lopped off about 0.40" of the barrel end with a parting tool and cleaned up the cut with a razor sharp H.S.S. facing tool. Next, I reinserted the range rod and indicated both ends back to zero-zero. Then, I took another very light 90 degree cut across the face of the muzzle just to square everything up. Next, I proceeded to cut the most perfect 11 degree crown that I am capable of cutting. Finally, I bedded the whole shebang in a Bell & Carlson, Medalist, tactical stock. Not exactly a bench-rest rig, but hopefully good enough for what I had in mind.
In the interest of uniformity and impartiality, I decided not to do any specific “load-work” for this new test rifle. I simply picked components that have repeatedly proven accurate in the .308 Winchester cartridge and called it good. (Federal brass, Varget powder, Fed. 210M, 168g Sierra M.K.) Out of force of habit and my compulsive nature, I did do complete “bench-rest” brass preparation.
In order to magnify the results of these crown tests, positive or negative, I elected to do all test shooting at 200 yards. In the interest of fairness, I did not use wind flags or attempt to “steer” the bullets in any way. But, I did attempt to shoot in similar atmospheric conditions; which unfortunately turned out to be a bit breezier than I would have preferred. Also, because I knew I would be repeatedly pulling the gun apart to reinsert it in the lathe, I decided to use our Schmidt & Bender 10x42 PMII scope in steel Leupold Mk 4 rings. Although this outstanding tactical scope is a far cry from a fine reticle competition model, it has proven capable of returning to almost the exact point of impact regardless of the number of times it is removed and replaced. Plus, like all the Schmidt & Bender PMII’s that we own or have used, there is never any doubt that you are actually testing the gun and not the scope!!!
As it happened to turn out, for test # 1 with the 11 degree crown, the barrel was 30.75" long overall. If you have ever wondered just how fast a nearly 31" long .308 Winchester barrel would be, check out the Oehler 35p chronograph slip pasted to test target #1 – 2,876 FPS @ 45°F. That is smoking for a 168g bullet!!! As you can see in the photo, the group was decent, (1.36"@ 200) but certainly not great. The wind was erratic and coming from three o’clock and obviously I got caught at least three times.
Back at the shop I pulled the scope from the Badger rail and the action from the stock. I stuck everything back in the lathe and meticulously re-indicated both ends of the range rod. I parted off 0.110" which completely separated the old 11 degree crown from the end of the barrel and left me with a cool souvenir. I took a good 90 degree clean up cut across the end of the barrel, and then re-indicated everything again. I took another very light clean up cut to square everything and then switched tools to a very sharp mini boring bar. I then cut a very pretty 90 degree recessed crown on the barrel end. Once again, more by happenstance than planning, the overall barrel length ended up at exactly 30.5".
Out in the field, conditions for test #2 were very similar to those for test #1; a breezy 5-7mph cross wind with a slightly warmer temperature of 48 degrees. Once again, I simply held in the center of the target dot and pulled the trigger. The results of which can be seen in one of the accompanying photos. Although this 90 degree recessed group (1.31" @ 200) was not significantly smaller than the 11 degree group, there was a “cluster” of six shots that looked rather promising. You will also note that the velocity only dropped from 2,876 to 2,864, and that the standard deviation actually got better going from 13 FPS to 6 FPS. So does barrel length have anything to do with extreme spreads and standard deviations? Beats the heck out of me! That experiment will need to wait for another day.
Returning to the shop I repeated the same old routine; pull it apart, chuck it up, indicate it, cut it, (another souvenir) re-indicate it and then cut my very first 45 degree crown. As luck, or some strange Voodoo would have it, the finished barrel length turned out to be exactly 30.25"!!! Maybe it’s some Idiot savant, left brain, machinist thing, but this unplanned uniformity happens all the time. Perhaps I should just throw all my expensive measuring tools away and start eyeballing everything!
Speaking of eyeballing, after firing five shots at the #3, 45 degree test target, I could only make out one hole through the 10 power scope! Either I was going blind or some really good things were happening 200 yards down range! Can you spell – NERVOUS? Two more shots and still I could only make out one ragged hole. Can you spell – PANIC? Well, the photo tells the sad story of the final three shots. Obviously, I folded like Chuck Shumer at an NRA convention.
Despite the shooter induced flyers, the 45 degree crown group was much smaller and much more uniform than the previous test groups. If you disregard the three errant shots, the seven shot array went 0.58" @ 200, which isn’t too bad for a sporter weight rifle wearing a 10 power scope. And, lest I forget to mention it, the atmospheric conditions for this 45 degree crown test were slightly worse than those for the 11 degree and recessed 90 degree tests!
Before firing this small 45 degree test group, I had fully intended to continue experimenting and try one of Richard Franklin’s deeply recessed 90 degree quiet crowns. But, honestly, after firing that last small group I simply lacked the fortitude to continue on. If I (we) have learned anything in this gun building career, it is that “extreme” accuracy is a fickle and temperamental Mistress and when she smiles on you, it is best just to embrace her and leave well enough alone.
Unless, of course, she is 30.25" long! Holy cow, that long tube was hard to pack around on the mountain. So, against my better judgment I decided to revisit this project, take a big chance and whack-off a full three inch section of barrel.
For the fourth (and hopefully final) time I once again went through the entire pull it apart, chuck it up, indicate it to zero-zero and cut a new crown routine. This time electing to try my first deeply recessed 90 degree crown. Which actually turned out great and looks pretty cool if I do say so myself. But, how would it shoot?
On test day, the conditions were downright crappy; a switching right to left cross-wind gusting to 20 MPH or more. As much as I wanted to “hold for the conditions,” I stuck with the established “no hold” protocol and blasted away. Would you believe the first three shots nearly went through the exact same hole? Then, inevitably, I got “caught” and opened the five shot group to 0.65˝ @ 200 yards (no vertical-all horizontal). Under those nasty conditions it seemed pointless to attempt a ten shot group so I quit while I was ahead. Obviously, the gun still shot just as good, or even better, than it had before. Truly amazing! And, you will note that we only lost 30 fps by cutting off three inches of barrel!
So does all this testing mean the 90 degree deep recessed crown will be my new Holy Grail? Not necessarily. In fact, given that it is absolutely square and perfectly concentric, I am beginning to wonder if the actual angle or shape of the crown matters much at all!!!! (I can’t believe I just said that!) Moreover, I am seriously beginning to contemplate the feasibility of “tuning” barrels to a specific load, as opposed to the established doctrine of tuning loads to a specific barrel. Think about it; you pick the load you want to shoot, and then start cutting the barrel off in ¼ inch increments until you hit a “sweet spot” and the desired level of accuracy! I am willing to bet that the length of the barrel would have more influence on the group size and shape than the angle or type of crown. Seems like another experiment to me – I’ll leave some Viagra on the barrel rack.