Obviously a damaged crown, ie; a dent causing distortion of the muzzle will cause inaccuracy.

Also obviously, repairing said damage will restore original accuracy.

As far as a less than perfect crown reducing accuracy, I strongly suspect it will.. But, I don't know as I only put perfect crowns on.. If they're not right do it until it is.
Pat

After doing this poll here it might be interesting to take the same poll of Custom Barrel makers and BR Gunsmiths and see how the results add up.

Here is partly why I feel the way I do. I have no problems with others opinions as some here do.

Saeed experiment

The quality of the bore is known to effect accuracy and the crown is the last part of the bore the bullet touches, why wouldn`t it have an effect? I feel any damage to the crown is detrimental to the accuracy of the barrel, just how much is debatable.

I do believe a "perfect" crown contributes positively to the accuracy potential of any barrel, regardless of quality.

I've owned well over 100 centerfire rifles and never ever seen one with a defective crown or damage to the crown that might deter accuracy.

I agree that a bad crown will have a negative effect on accuracy.....but have never seen it.

quote:

Originally posted by larrys:
Here is partly why I feel the way I do. I have no problems with others opinions as some here do.

Saeed experiment

I rember reading this back in 01 makes a guy think!!

If the crown has some imperfection in it, every time you shoot that gun, the bullet exiting the muzzle encounters the same imperfection at the same point in the firing sequence. This consistent encounter with the same imperfection every time might displace the impact point some, but to a first approximation*, it should not affect group size. Consistency will not degrade accuracy.

I hadn't followed up and read Saeed's results yet. My preliminary interpretation is that I don't need to worry about my crowns on my hunting rifles and that maybe barrel harmonics and other stuff is more important.

H. C.

*This first approximation is crude.

quote:

... but to a first approximation*

As is (linear) Taylor series approximation???

All of this is really getting amusing if you also read some of the other tread topics on the forum.

On one you have a big argument going on about how clean and spotless a bore has to be to shoot good ...then you have a big argument over here going on about how you can take a air hammer to the muzzle, and let the bore rust, and actually get better accuracy.

I’m a convert!!!!!!!

Went out earlier and pounded some nails with the muzzle of an old rifle that had never shot worth a damn, then had my dog piss down the bore, and now the sucker shoots one-hole groups at 2,000 yards...off-hand!!!!

quote:

Went out earlier and pounded some nails with the muzzle of an old rifle that had never shot worth a damn, then had my dog piss down the bore, and now the sucker shoots one-hole groups at 2,000 yards...off-hand!!!!

Old News..........

When ya learn to do it on one leg get back with us..

I actually had one such experiment "imposed" upon me many years ago. As a teenager hunting beavers in spring breakup, I was swept out of a boat into a river that was running plenty of ice. In doing so, I lost my trusty single shot Mossberg 640 .22 WMR. It was extremely accurate, and capable of ragged one-holers at 50 yards even with a crude Weaver C-4 scope, and I was heartbroken at losing it - brand new, it had cost me a very hard earned $35.

In late autumn when the water was low, I walked the river and found the rifle lying on the rocks, rusted almost beyond recognition. I soaked it in a pail of diesel fuel for a week or so just to be able to get the bolt open, but amazingly, once I got the mud and sand out, the bore remained bright. The muzzle, however, had rusted back around the bore and the crown was 'jagged', to say the least.

After literally days of cleaning and de-rusting (there were, and remain, pits 1/16" deep on the outside of the barrel and action) I took it out and gingerly touched off a few rounds. One jagged hole at 50 yards, the same as always.

Many years later, I had the barrel shortened somewhat, and had it crowned with a recessed 'target' crown. It still shoots exactly the same.

In another instance, I once bought a used Browning Safari in .270 that didn't shoot well at all. I noticed that the crown had a very visible 'ding', and trotted off to my favorite gunsmith to have it trued. It shot exactly the same as before.

I still take care about protecting the crowns on my firearms; logic still tells me a bad crown should harm accuracy - but my experience is to the contrary. Mark me down as "damned if I know!"

quote:

Originally posted by Rick 0311:
I’m a convert!!!!!!!

Went out earlier and pounded some nails with the muzzle of an old rifle that had never shot worth a damn, then had my dog piss down the bore, and now the sucker shoots one-hole groups at 2,000 yards...off-hand!!!!

Rick,

I never go to all that trouble. I just whip out the ole Sawz-All, an 8 tpi blade, and my trusty 1/2" ratbastard file for finishin' em up. Gives them that "crowning touch".

quote:

Originally posted by craigster:

quote:

Originally posted by Rick 0311:
I’m a convert!!!!!!!

Went out earlier and pounded some nails with the muzzle of an old rifle that had never shot worth a damn, then had my dog piss down the bore, and now the sucker shoots one-hole groups at 2,000 yards...off-hand!!!!

Rick,

I never go to all that trouble. I just whip out the ole Sawz-All, an 8 tpi blade, and my trusty 1/2" ratbastard file for finishin' em up. Gives them that "crowning touch".

Well craigster...that’s because you are a true craftsman and I’m just a back-yard gun butcher!

quote:

Originally posted by Tumbleweed:
I took it out and gingerly touched off a few rounds. One jagged hole at 50 yards, the same as always.

Could it be that only one bullet hit the target and it was going sideways?

quote:

then had my dog piss down the bore, and now the sucker shoots one-hole groups at 2,000 yards...off-hand!!!!

Now there's some bore cleaner. Rick you should bottle that stuff and sell it, maybe call it:

FOUL IN

You might want a little warning label on the back though, just to keep people of complaining of burned dog piss

quote:

Originally posted by Alberta Canuck:
In a couple of other threads there seems to be some heated debate as to whether a square-to-the-bore, un-nicked, smooth barrel crown is necessary for accuracy (small group size). Some folks believe strongly that it is, others seem to think it is irrelevant....

I went with "A damaged crown can cause inaccuracy", simply because I "believe" that is true.

I'd say it also depends where the actual damage is located on the muzzle. The closer to the Bore, and the larger the imperfection is, the more effect it would have.

It might be relative to think about the actual distances some folks actually shoot at Game. For those who hunt up close, it might or might not be noticable at all. For those of us that occasionally shoot a bit farther out, we need all the accuracy we can get, so I choose to eliminate as many (potential?) negative influences as possible.

I think of it similar to putting up with a "nagging woman". You know in the back of your mind it is going to eventually be an issue you must deal with. So, it is better to just eliminate the problem when it is first noticed.

I didn't vote. I'm an agnostic.

I wish Saeed's experiment had continued further.

But I'll posit a hypothesis: Crown damage might be a more significant factor when the throat's worn, the bore's worn and loose, or the bullet's too small.

Saeed was doing his muzzle damage tests on a brand new factory take-off barrel. It shot very well to begin with. As many people have said already, an asymmetry at the muzzle ought to affect every bullet the same way, if the bullets are passing through it the same way every time. In that case, you should still see good groups, perhaps with the point of impact shifted. If you've got a barrel with a very loose, eroded throat, the bullets can start off canted in the bore, and likely won't all cant the same way. A loose bore, the worst case being one that loosens up going toward the muzzle, can let the bullet rattle around laterally as well as tipping. With any of these conditions, the bullets passing the asymmetrical crown will get different "shoves" from one side, depending on how they're oriented when they pass it.

A couple of years ago, Precision Shooting ran an article where a decent barrel(1/2" approx. groups) was damaged at the crown, and cut off at an angle. The rifling was worn off at the muzzle with emery for about 1/4"-this opened up groups to 2 1/2" approx. Then the barrel was cut back and recrowned nicely-back to 1/2" groups. Then the thing was cut at a 10 deg angle-groups were about 3/4", but 3" off aim.Recrown normally again-good groups. Then a ding was put into the edge of the bore with a sharp rock-bullets were keyholing,off paper at 100 yds and copper was built up at the sharp edge of the bore. Recrown back normally- back to 1/2" groups on point of aim. I personally restored accuracy to a worn garand, and a 45-70 marlin with a muzzle ding by recrowning. The 45-70 only needed the round lap, and grinding compound, the garand 3/8" shorter, and lapping.

I bought a win classic in 270wsm,adjusted the trigger and it wouldn't hit a bull in the a--@100 yds,had a friend that does a super job to bed it for me still wouldn't shoot,took it to a fellow that builds 1000 yd rifles he took one look at the crown and said that was my problem,he recrowned it and it started shooting 1/2 in groups.This was a new rifle from the factory.So I would have to say the crown is very inportant.

I’d like to hear from the one guy that says “other.†What the hell is that???

I'll ask Bob Hart about this topic, in a couple of weeks.
Going to pick up my BDL that is being made into a VBDL.

I read somewhere once the effect on the bullet from a bad crown was mostly caused by gas blow-by escaping unevenly at one point on the bullets base. This caused the bullet to start wobbling in an eratic manner. The line of thought was the higher the muzzle pressure the more effect the damage would show. I can`t remember where I saw this but it made sense at the time and I`ve always took it as plausible explanation.

quote:

Originally posted by Ol` Joe:
I read somewhere once the effect on the bullet from a bad crown was mostly caused by gas blow-by escaping unevenly at one point on the bullets base. This caused the bullet to start wobbling in an eratic manner. The line of thought was the higher the muzzle pressure the more effect the damage would show. I can`t remember where I saw this but it made sense at the time and I`ve always took it as plausible explanation.

First off, I don't recall the magazine, the author, or the exact year, BUT, I remember a series of articles which appeared in some shooting magazine years ago, which, over a period of time, discussed with various experts, bedding choices and techniques, chambering, throating, crowning, optical choices, and rifle rests for benchrest competition.

One of the articles caught my attention. It was about the bullets exit, and the effects that the shape of the muzzle and crown had on accuracy. It showed a series of "dye" enhanced, still photographs, of blast angles from various shaped muzzles. The off center, lop sided blast, from non-concentric, factory type muzzles were clearly visible in the photo's as well as the concentric and well defined blast of the precision, trued and squared variety.

The guy who did the article was as I recall, an areo-space engineer (a rocket scientist) and was himself a benchrest shooter. This appeared back about 1980 and it was the first time I had read or heard ANYTHING regarding the merits of an 11 degree recessed crown.

He talked about the effects heated air (that which preceeds the bullet), super heated air (that which follows the bullet), and the ambient air (that which surrounds the muzzle) has on the flight path of a bullet and how important it is to accuracy, that this air "turbulent effect", or, disturbance, be reduced as much as possible.

He determined, through the use of high speed film and observation of various blast patterns, that the dispersion angle that produced the LEAST amount of disturbance at the muzzle was 11 degrees.

As I remember, he called the resulting disturbance at the muzzle, when the heated air and the super heated gas collides with the ambient air as "gas slap". And, he explained how an "off center" or "of axis" gas slap is detrimental to bullet flight.

He further went on to explaine how this "gas slap" disturbance would shift about, like a mirage, as the barrel steel at the muzzle would heat and cool throughout a competition.

Now, whether this has any effect on accuracy with the average hunting rifle, and to what extent is something each of you will have to determine for yourself. As for me, I have seen the proof countless times. Maybe it isn't so much the 11 degree angle as much as it is the fact that the muzzles are clean, square and concentric, but I have been installing precision 11 degree recessed crowns ever since, and have had nothing but positive feedback and reports of "miracles" as a result.

So for me, I am in the "A less than perfect crown will reduce accuracy, whether by damage or by manufacture" group. I firmly believe the bullets exit is just as critical to accuracy as it's beginning journey at the throat. JMPOBOYODTS...

G.Malmborg,
IMO, you hit the target with your statement saying, "as long as it's (the crown) clean, square and concentric", it will offer good results. I know many of the current benchrest gunsmiths and in fact do my own work as well and many use a straight 90' crown these days. Some recess it others do not.. Speaking strictly of benchrest rifle here. I'm confident that the 11' is just as good, however.

The photo’s malm spoke of are in Harold Vaughn’s book “Rifle Accuracy Facts.â€

A damaged or less than square and concentric muzzle has an effect on the bullet...PERIOD end of story. How much effect can be debated till the cows come home... but it is ludicrous, and defies physics and logic, to say that it has no effect at all.

The 11 degree crown is “thought†to be the closest shape that approximates the most natural shape of the cone of gases as they exit the bore.

It is also the most difficult to machine because it is far less forgiving in the lathe set up and in any slight out of roundness of the OD of the barrel... whereas a barrel that runs out of round a few thousandths can easily be faced off to 90 degrees with no problem.