Gentlemen,

In your experience, which type of crowm gives the best accuracy?

a clean concentric one...........
I have factory, target, and recessed, the only difference in my opinion, is the level of finish. There was no difference in accuracy between the different types, including recrowning to a different style.

Saeed my friend,
My experience would agree with Carnivore's. I think you know this and have even test butchered crowns with little effect on accuracy. No dings is best in most cases, however.

Are you setting us up for another demonstration? Has Walter come up with an innovation in crowning?

RAB,

You should see the arguments we have here! We have a mini civil war going on constantly in our workshop. I try to stay away from all the arguments, but this does not stop everyone asking me what I think.

So I thought of asking our friends who have a lot more experience than I do.

Personally, I have settled on one type of crown. That is the recessed 90 degrees.

Walter is in a bit of trouble since he has announced himself being an aunty to my daughter!

The boys are driving him nuts with thier comments about his change of "equipment"!

The bets are about half and half right now, and I imagine soon they will have to tie him down and take his trousers off to see if he IS an aunty

It is one of the very few times ever that I have heard him asking me to help him, and as he has not been what you might call a good friend to me lately, I think I will decline.

I have my video camera ready though

Absolute squareness to the longitudinal axis of the bore is the key determing factor in the success of a crown now matter what style. Saeed you did test with damaged crown; what about off axis crowns? Start off with a square 90 degree crown then progressively off axis crowns.

[ 10-12-2002, 17:14: Message edited by: Bear Claw ]

I agree about the most important thing with a crown is that it is must be concentric. However, in the benchrest game, which is the peek of accuracy, it has long been accepted that an 11 to 14 degree concave crown is what is most accurate. Engineering types, far smarter then me, felt that this was what was best. Something about the way the gases escaped behind the bullet.

Now in a accurate hunting rifle, I don't think that you will see a major, or even minor, difference as long as the crown is concentric and smoothe. Personally, I prefer a 14-degree concave with the corner of the rifling cut at a 45-degree. This 45-degree cut minimizes gas wear and brush wear at the crown. I've found that if you don't do this, you need to re-crown about every 400 to 500 rounds.

as with the above style does not matter, as longe as it is square. My dad has a Springfield that was hack sawed off and will shoot 1 to 11/4" groups.

I guess I don't follow the in-crowd these days with the eleven degree crown theory because I don't believe that it offers sufficient protection to the rifelings. Square and concentric is the key, and most everything else that gets brought up on the subject you can normally throw in the anal retentive round file.

Triggerguard, I've never seen any crown that offered what I consider to be "sufficent" protection. If you stick your rifle muzzle down into the carpet of your truck and ride it around it doesn't matter what kind of crown it is. In the twenty years I've been using this crown, I don't think I've ever had to re-crown one that has been damaged from hitting something or any kind of normal use except wear from shooting and cleaning. I've tried all of the other types of crowns and have never seen any advantadge whatsoever to them. Admittedly, as I said, in a sporter weight rifle I don't think there is much of an accuracy advantage with the 11-degree, but I'll take every little bit I can.

John,
With a recessed crown of around .075 or so, you'll get away with riding around in your pickup with the muzzle in the carpet far better than the eleven degree system. As with all things pertaining to fireams and life in general, the best medicine is good ole common sense. I've seen guys that could break an anvil, so you can't allow for everything, but a little more insurance never hurts.

Saeed

After observing a lot of bench rest gunsmiths and some gunsmiths who cater to the high power and 1000 yd competitors and reading many articles in Precision Shooting and Accurate rifle I have come to the conclusion that the most accurate shape is a counter bore 90 degrees to the axis of the bore. Most of the accuracy gunsmiths beleive there is no proof that the 11 degree crown is any better than the 90 degree, and it is an accepted fact that if the 11 degree is not perfectly square with the bore that you will create an elipse which would be most detremental to accuracy.

Some of the accuracy specialist after cutting the 90 degree crown will take a spherical shape tool and carefully lap the crown untill the lands are recessed and the sharp edge disapears from the bottom of the grooves.

I know you asked about shape and here I am discussing technique but I would like to point out one more technique and that is when making your finish cuts always cut from the center out to reduce burrs. I like to take a Q tip and drag accross the crown to see if it picks up lint. If you dont want to lap the crown, sometimes you can eliminate them with a new bore brush.

When a customer asks me about crown shape I always tell them that accuracy is dependant 99 % on technique and 1 % on shape and they should choose the shape they like. I have built some very accurate rifles with the traditional rounded recessed hunting crown too.

One more thought and I'll shut up. I think the gun manufactors have picked up on the 11 degree crown just like they did on fluting and have used it as a marketing tool to sell more guns.

Saeed - I've never been able to tell any difference but I've always had my rifles built with the recessed crown just because I like the way it looks. How's that for scientific?

Oops, sorry. Just noticed this was a "gunsmith" question. I don't qualify. I just like to sit and watch a good one work.

[ 10-13-2002, 06:16: Message edited by: Pecos45 ]

I read an article written quite a few years ago, by some areospace technician in some magazine, but when, who and where does not matter, it was the jist of the article that had my attention. He wrote that the 11 degree angle at the crown was considered and provable by science, as the perfect angle for muzzle crowns. It had something to do with the hot air ahead of and hot gas behind the bullet as it met the cooler ambient air surrounding the muzzle, and the ability of the 11 degree angle to quickly and more uniformly disperse the gas, which greatly reduced the turbulent effect at the muzzle. He figured that "bullet slap" was reduced as much as 30 percent with the 11 degree angle which, according to his article, would allow the bullet to recover some 30 percent quicker as it exited the bore. I remember seeing the photographs accompanying the article which showed the 11 degree crown and a couple of the other popular designs of the day. The photo depicting the 11 degree crown as I recall, showed less disruption of the air surrounding the muzzle than the other styles.

Soooo, I have been cutting crowns to the 11 degree form since and have had nothing but outstanding performance. I have noticed, due to the 11 degree angle, the blast pattern around the crown is more uniform than that of the flat 90 degree form which might account for something.

Malm

I've been using the 60 degree center reamer with a floating pilot .0002" under bore diameter in order to recess the crown for protection. This pretty well assures accurate crowning. Have tried all others and found no difference. Except for the concentricity of the actual rifling at the end of the barrel, I think, the rest of it is for show.

Never put anything in the bore of a precision weapon that you wouldn't put in your eye... were the words of the tribal elder. I would assume that would apply to piloted crowning reamers as well?

Malm

Hey'
A layman would like to ask this question.On rifles used for hunting,do muzzlebrakes,negate the crowing?
1geejay
www.shooting-hunting.com

As the bullet leaves the bore and enters the brake, the escaping gas is distributed out through the ports so that by the time the bullet actually leaves the brake, the turbulent effect is severely diminished resulting in less bullet slap. This is probably why weapons, when "properly fitted" with muzzle brakes, can be so accurate. Bullets traveling through improperly fitted muzzle brakes can suffer from "off side gas influence" which destroys accuracy. Regardless of which style of crown in used, it must be clean and square so as to guide the bullet straight through the brake.

Malm

Thanks Malm,
I was hoping I would get a positive response,since many of my rifles,have brakes.
1geejay
www.shooting-hunting.com

Hey'
If you go tmy site,you can most likely find a stockmaker in your area,or several.In key words just type in stock,and city and state.
1geejay
www.shooting-hunting.com

G. Malmborg

If you don't use piloted tools how do you ream your chamber? Do you use a boring tool?

Grkldoc,

Boring bar? hardly... I use a lathe. The axis of the bore spins "dead center" and the reamer is introduced into the bore "on center" and held in place and fed by the tail stock which is "centered", which, assures "dead center" results.

Introducing a hand reamer or one you can operate with a drill into the muzzle end of a precision barrel regardless of the tolerance of the "floating pilot" results in less than dead center results and is a kin to "malpractice". It might work good enough for close in shooting, but when the ultimate accuracy of the weapon counts, to overcome sloppy human shooting habits, there is no substitue for "machine precision".

In summary: It does little good to machine true and blue print an action and barrel only to finish off one of the most important areas of the job, the crown, with anything piloted. My opinion of course. If a piloted crowning reamer works for you, then hey, good luck!

Malm

Very good post Malm, I agree with you completely.

G. Malmborg
I agree. I wouldn't use a hand reamer or a drill either. I do this on my lathe and have had exceptional accuracy on the range. However, someone still needs to prove to me that its ok to use a pilot where the bullet gets its start but not ok where the bullet exits because I haven't seen a difference.

Grkldoc,

Every now and again a weapon will show up that suddenly shoots like lightning, never hitting the same spot twice, and upon initial examination, it is discovered that the barrel has a buldge right at the muzzle or within 1.5 inch of the muzzle. Everyone would agree that this is sufficient to destroy accuracy right, yet, I have had guns come into my shop, that shoot phenominal groups only to discover later that a spider had at one time, placed it's web down deep in the barrel creating a buldge, yet it still shoots great. Go figure.

Now getting back to your post concerning the use of a pilot on one end, versus the other end. Knowing that a bullet will travel a distance beyond where a chamber reamer pilot would run before the bullet is completely sealed, (evidenced by powder residue on the case neck) probably explains why pilot use at the chamber end is less likely to affect accuracy than having the bullet suddenly hit a rough spot just as it's about to leave the safety of the bore, at the muzzle. We ignore the minor damage or buldge down deep in the barrel because it hasn't adversely affected accuracy, but we'll cut the barrel back and recrown it because of it's affect.

The one place where you want everything to be in perfect sinc once you touch that trigger, is at the muzzle, because it is the last thing to touch the bullet and it is the last thing you have complete control over, and it had better be as perfect and flawless as possible.

It is my opinion, that any defect or flaw, be it machine or human caused, in the muzzle end of the barrel, can have a detrimental effect on accuracy, and, it is my job as a professional, to repair and to educate people (not you of course) so that they take better care of their weapons.

So now tell me, why would you use a piloted reamer to cut the crown when you have better and total control using a single point tool, and with less chance of causing damage? Just curious. If reaming the crown is working for you and you are getting every drop of accuracy you can wring out of the weapon and load, then that is great. I'm relieved to know you don't use one of the piloted hand operated reamers offered to the trade to crown with. I'm new to this list and do not know you, so when I read someone using a piloted anything in the muzzle of a weapon I flinch.

Regards,

Malm

If the crown is well done so that the point of departure is the same all the way around, no particular type of crown will do any better than another.
I once looked over pages of data covering testing done by winchester where they found (to their satisfaction)a counterbored flat crown to allow the bullet to depart least disturbed.
I have used counterbored crowns, flat recessed crowns, 11 degree crowns and a simple center reamed crown on my BR rifles over the years and have had successes with each type. My favorite is the conventional flat recessed crown and that is what I use now.
Finishing of the crown can be done by polishing or lapping or by the use of a piloted reamer. While there may be some risk of marking the bore with the pilot, I have never had it happen. I'm a firm believer that if the bore appears unmarked then it is unmarked!
A rifle with a muzzle brake is usually crowned square or with a center reamer after the threading operation. So the crown is inside the brake. Regards, Bill.

Ive heard nothing but good about the 11* target crown (that is until I read this topic). Im still planning on having my rifle rebored from the factory recessed crown into a 11* target crown. I have my doubts about a mass-produced rifle having perfectly square or concentrict crown, thus Im getting recrowned by a good gunsmithing outfit located here in Montana (Montana Rifleman up in Kalispell).

The opinions over types and styles of crowns are as varied as "what is the best all around gun". I think everyone will agree, that whatever style one chooses, it must be clean, square, centered and above all, undamaged.

Malm