A proper crown . . . Is there only one type?

[OS OK]

GENTLEMEN . . . I am running a thread in the rimfire area about shooting a 'Peep & globe'...in that thread I had shown a picture of my crown on a Savage MKII FVT, .22lr.



We were discussing the bore condition when one of the fellas mentioned that he thought the crown might be the culprit for creating shot dispersion.
I am reading this book to find out about the crown this gunsmith does on his work but haven't found an answer yet as there's no chapter on crowns...this book is a collection of papers and articles that Bill Calfee has written over about a 20 year span and then later published in book form.



All I have discovered thus far is that a taper like this keeps the live center part of the lathe better engauged with the barrel on the lathe. He didn't go on in that paper to say what he does later with the crown.
I'm sure to find it somewhere in this 721 page book but...I thought perhaps one of you might comment on this subject of 'CROWNS' in a lead shooting barrel like the .22lr.

I don't know my butt from my elbows about machine work or gunsmithing and would appreciate you fellas giving me a good education along with the folks following that thread I'm running.

Thanks very much . . . charlie

[FLINTNFIRE]

Does not look like there is anything wrong with that crown , the outer portion that has its own crown is only protecting the true inner crown , but that is only my opinion , I have rifles with that style and those with only a crown and those with no crown , accuracy seems fine with all of them as long as no damage where the bullet exits my 2 cents

[Tatume]

Does not look like there is anything wrong with that crown , the outer portion that has its own crown is only protecting the true inner crown , but that is only my opinion , I have rifles with that style and those with only a crown and those with no crown , accuracy seems fine with all of them as long as no damage where the bullet exits my 2 cents

Agreed. A completely flat face on the muzzle is as good a crown as any so far as accuracy is concerned. My Winchester Model 52 has such a crown. It may be a little more susceptible to damage than a recessed crown, but for target work it works fine. As evidence consider the number of championships and records won with the Model 52.

[OS OK]

Agreed. A completely flat face on the muzzle is as good a crown as any so far as accuracy is concerned. My Winchester Model 52 has such a crown. It may be a little more susceptible to damage than a recessed crown, but for target work it works fine. As evidence consider the number of championships and records won with the Model 52.

Calfee talks a lot about that Win 52 in his book. He said that it was the forerunner for all modern rimfire .22 actions.

One of the fellas posting in my thread, said that a friend told him...
"when the projectiles leaves a tapered crown, it leaves the lands first and allows gassing before the base leaves the grooves, that this specifically is the culprit in upsetting the projectile."

In my little brain, I would think the tapered crown would upset the round each and every time, that I couldn't have any bughole groups.
I have shot many tight groups in the past 6 months since I got it new. Some as small as 3/8"...this shouldn't be possible, right?

[Tatume]

People says lots of things without a basis in fact.

[curdog007]

I think, too, having a crown square with the bore axis for the last couple of inches of barrel is critical as well. This may or may not be the same as square with the exterior of the barrel. Especially on a production factory crimp.

[gpidaho]

There's an old thread over at the Cast Bullet Association Where folks purposely filed notches in rifle barrels to test the old saw of damaged crowns. The outcome of these test showed that while point of aim was changed the damaged crowns had no effect on the rifles accuracy. Gp

[303Guy]

There's an old thread over at the Cast Bullet Association Where folks purposely filed notches in rifle barrels to test the old saw of damaged crowns. The outcome of these test showed that while point of aim was changed the damaged crowns had no effect on the rifles accuracy. Gp

That's interesting. My thinking is that the crown is a potential variable that is easily eliminated and that the squared recessed crown is the easiest to get square to the bore.

One reads that testing has shown the 11 degree crown to be the most accurate (providing it's perfectly concentric to the bore). Thing is, if the crown makes no difference then it would be impossible to determine the most accurate crown. Unless the difference only becomes apparent with quality match bullets?

Anyway, I have not done comparative tests so I can't say. What I can say though is that my Toz 17 has a deep recessed crown that has a 45 degree chamfer. I can do a comparative test on that rifle. I have a few groups from it and I can do a few more, preferably with a better scope and better ammo. I might be able to shoot groups in two weeks time. If I can then I'll square the crown and shoot it again and see what results I get. I'm betting that it won't get worse. But will it get better and will I be able to tell? One way to find out. I was in any case going to square the crown but now I'll wait and shoot more groups with it first. I would also need to check the bedding before I do anything else.

[john.k]

A flat crown is the easiest to get done accurately in a lathe.....basically ,if the barrel is clocked in to the lathe spindle,the cut across the muzzle is dead square.....now any angle of crown,and the muzzle must also be exactly centered,or the cone wont be concentric with bore.......Note the military style rounded crown is designed so that hits on the muzzle dont adversely affect accuracy.....Ive found 45deg style countersinks the most problematic,probably because they were done with a countersink bit in a carpenters brace.

[303Guy]

In my little brain, I would think the tapered crown would upset the round each and every time, that I couldn't have any bughole groups.
I have shot many tight groups in the past 6 months since I got it new. Some as small as 3/8"...this shouldn't be possible, right?

I having wondering about this very thing.

[john.k]

If muzzle blast had a measurable effect,then every target rifle would have a Pendelton style group of holes to bleed away pressure before bullet exit.......which they dont......With EDM it would be possible to place all the holes in rifling lands,so there was no effect on bullet surface.

[tazman]

I read an article about making the accuracy of a Kimber 82G better by truing the crown. What that particular gunsmith did was to use an appropriately sized spherical ball with a light coat of abrasive compound of some type and spin it in the end of the bore to get a perfect crown. This method would have given the rifle an angled crown similar to your Savage.
The guy claimed it was the only way to accurately do it since the bores on the 82G rifles was rarely centered in the barrel.
I don't know anything about how the barrel or the tool was supported or how much metal he took off.
I am sorry that I can't remember or find the article now. I have no way of testing his process.
The Kimber 82G I owned, didn't shoot nearly as well as my CZ MTR at 50 yards.

[303Guy]

If muzzle blast had a measurable effect,then every target rifle would have a Pendelton style group of holes to bleed away pressure before bullet exit.......which they dont......With EDM it would be possible to place all the holes in rifling lands,so there was no effect on bullet surface.

What target shooters do is use target bullets with perfectly symmetrical and consistent bullet bases and trailing edges. Tests have been done on bullet noses, damaging them in different ways. Nose damage had little to no effect. But damage to bullet bases was found to have a large effect. That only means the trailing edge effects bullet flight.

Here is a rather strange muzzle crown test. http://www.accuratereloading.com/crownr.html

What this shows me that even a rough hacksaw cut crown is better than a 45 degree crown. This particular crown damage test was to show that a simple hacksaw repair can keep you in the hunt after a crown damage.

[Mk42gunner]

My feeling on crowns is that as long as it is even you will not be able to tell the difference with a rifle held by human hands; maybe with a rail gun, maybe not.

And yes, I have shortened and hand crowned a few rifles.

Robert

[303Guy]

Well, it looks like the crown is over-rated. Have a look at what this guy did. https://rifleshooter.com/2018/03/do-...fect-accuracy/

Well, I'll do that test on the Toz 17 just the same. But seems that we can relax some.

And yet, a 22 bullet seemed to have shaved a sliver on chambering and upset the accuracy for several shots. We also know that a 22 won't shoot straight after cleaning until the bore has seasoned. Often (or sometimes) they won't shoot straight when changing brands or types of ammo until the bore has seasoned. So who knows? Maybe it's worth squaring that crown for good measure.

[OS OK]

Well, it looks like the crown is over-rated. Have a look at what this guy did. https://rifleshooter.com/2018/03/do-...fect-accuracy/

Well, I'll do that test on the Toz 17 just the same. But seems that we can relax some.

And yet, a 22 bullet seemed to have shaved a sliver on chambering and upset the accuracy for several shots. We also know that a 22 won't shoot straight after cleaning until the bore has seasoned. Often (or sometimes) they won't shoot straight when changing brands or types of ammo until the bore has seasoned. So who knows? Maybe it's worth squaring that crown for good measure.

That is a bizarre article you posted 303Guy...he cut that barrel over and over again and did an intentional awful job on the cut(s)...didn't do anything at all to the crown and yet all the various cuts and barrel lengths produced groups at 100 yards that hovered around one MOA.

He got a wild hair and did this to the crown...



It shifted his POI 16 MOA at 100 yards but after re-sighting the scope...this dang cut of the barrel still produced MOA groups...I am astounded at this.
Average group size was 1.106″ (1.056 MOA)!

Here's his bottom line regarding the crown...


Does a rifle’s crown affect accuracy? Yes, it can. Bear in kind what accuracy means, how close we are to the target. We can have a precise rifle that isn’t accurate and an accurate rifle that isn’t precise. If you have a zero on your rifle and damage the crown you’ll most likely have a POI change which in turn affects accuracy.
Does a rifle’s crown affect precision? Not necessarily. I think the take away message from this post is that you can do some pretty awful things to your muzzle and still have a rifle that groups fairly well. Am I shooting 1 and 2″ groups? No, but I’m not about to do any load development on this gun. Would I want to take a rifle with these crowns to a match? No way. But it sure is interesting to see how well a tube like this can shoot!

I am still going to get Bill Calfee's opinion about the crown. I read earlier in his book that he distinguishes between a lead shooting barrel crown and say a centerfire that deals with jacketed.
When I find the right paper in that collection I'll be sure to post it here.

[samari46]

Do you know where I could get a copy of Bill Calfee's book?. Thanks Frank

[OS OK]

Do you know where I could get a copy of Bill Calfee's book?. Thanks Frank

I got mine from Amazon. https://www.amazon.com/Art-Rimfire-A.../dp/B07957WYDS

[303Guy]

This whole crown issue has been very interesting and educational. During my 'research' i.e. looking up on Google, I came across a forum chat. One poster had this to say;

Crowns do matter. If you have a burr anywhere on it that happens to shave copper, not only will it upset the bullet but it will off balance so it is important to have an excellent finish on your crown. Maybe the other details don't matter so much, but that one sure does.

Another fellow on that forum had this to say;

That article was obviously written by someone who just does not have a clue to begin with. Anyone who has spent any time working with guns generally has it figured out and know that little things like crowning, bedding, action truing, running bullets for concentric, grooming primer pockets and flash holes, turning necks, stress relieving barrels, lapping barrels and the whole other gambit of miracle accuracy cures do not automatically take a 2 inch gun and turn it into a 1/4 inch gun. At most, individual work like that (including crowning) improves your end score by thousandths of an inch. Yes, the odd time a damaged crown will cause a gun to open up from 1/2 inch to 3/4 inch but that's the exception, not the rule. If you take the time and spend the money to nitpick every one of those little details to the extreme, like Butch Lambert and guys like him do, you can take a good action with a good barrel and squeeze it from 1/2 inch at 100 yards down to acceptable bench rest accuracy. All that work and money to gain 1/4 inch better groups and you need the half inch capability to begin with before you even start to work.



It seems pretty obvious that for the last umpteen years this guy has thought that re-crowning a gun would turn it into an automatic bench rest gun which is just not the case and it's guys like that who end up spreading the rumors of such. On top of that he did not bother to test his findings. He is using a gun that is obviously not capable of recognizing the minute changes in accuracy from damaging the crown and to get any sort of solid, accurate results he would have to confirm his findings by firing the gun about 100 to 500 times before and after with an iron monster or lead sled in an indoor range to eliminate human error and mother nature. (we all did) The before and after changes that he is really looking for are very slight and shooting a half a dozen groups tells you nothing. On top of that, running a bunch of numbers and theoretical data is fine to confirm and explain your findings. But it's by no means solid evidence. You need to confirm the numbers with field trials and confirm the field trials with numbers. Now that he has it partly figured it out he seems to think he's saved the world. Well Buddy, I'm sorry but we had all that figured out when we were 18 or 20 and it's old news to us. Welcome to the club, be it a little bit late.

To know what it's all about if anyone is interested, here's the link; https://www.practicalmachinist.com/v...7/index2.html?

So, all I can say is this; "Don't confuse me with facts and logic - my mind has already been made up!"

But notice that nobody has ever claimed that a good crown does any harm? So, I'm sticking to my view that if the crown is known to be good, then whatever is happening on target is not to do with the crown.

[M-Tecs]

When you get to the high end of the accuracy game crowns do matter. It is well know that a damaged or inconsistent crown will affect accuracy and in some case a simple re-crowning will restore accuracy. What is much less understood what is the best type of crown if there is a best?. Lots of arguments generated and many articles have been written over the subject but very little agreement on what is best. Also looking at the winners circle equipment there doesn't appear to be a clear this is the best. The stepped 90 degree and the 11 degree tend to be the most popular.