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Barrel Crown?
#1
Can someone please explain this to me? I dont think I am understanding it properly. Thanks.
das, proud to be a member of pa2a.org since Sep 2012.
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#2
das;12099 Wrote:Can someone please explain this to me? I dont think I am understanding it properly. Thanks.

http://www.youtube.com/watch?v=otpFNL3yem4

Not a crowned rifle barrel but watch this video of a .45 leaving the barrel in slow motion.

And then ask yourself..

If there were any deformities at the end of the barrel that allowed gas to escape prematurely on one side of the muzzle and not the other, then don't you think the bullet would tip/ yaw or be pushed by the premature gas in a certain way that affected the bullets accuracy??


That's the way I always look at it anyway.
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#3
das;12099 Wrote:Can someone please explain this to me? I dont think I am understanding it properly. Thanks.

Ok, I'll see if I can clarify a bit here with some photos, and then I'll explain them. The first part that is in red is the "actual" crown, and what really matters when it comes to accuracy.

[Image: barrelcrown1.jpg]

This second photo has 2 areas in red. The parts in red and what is between them is commonly what is referred to as the "crown".

[Image: barrelcrown2.jpg]

The reason the crown is so important is because it's the last thing that ever touches the bullet, as it exits the barrel. The "true" crown is also what affects the way the escaping gases are vented around the bullet. You want the gases vented in a very uniform manner around the bullet, so they don't push the bullet one direction or another, and cause it to yaw as it starts its flight. If the bullet begins to yaw or wobble, it won't fly consistently, or as accurately. For this reason, the crown needs to be sharp and even, meaning no dings or burs. If there are dings, it'll make the gas vent around the bullet unevenly, and the dings or burs can even touch the bullet and engrave it in an uneven manner or push it. One of the first things you want to inspect on a used rifle is the condition of the crown. If it's damaged, it really says a lot about the rifle. It means that there's a fair change it won't shoot as good as it "could" (undamaged). It also means that there's a fair chance that the rifle wasn't properly maintained and cleaned, which means it may not shoot as well as it a properly maintained rifle.

This is the reason that lots of us say that more barrels have been ruined from improper cleaning, than from just being shot and never cleaned. This is why you should NOT clean a rifle from the muzzle if you can help it (certain designs). If possible, you should always clean from the breach/chamber side, pushes the patches out, and be VERY careful when bringing the tool back into the barrel. Lots of us never let the tool truly exit, and we NEVER pull brushes and such back in down the bore. As a matter of fact, lots of us don't use brushes and such at all, only patches and proper solvent.

Ok, so we talked about the "true" crown and how important it is. Most of the time, when people are talking about the crown, they're using the broad general term that I show in the second picture. The "crown" (general term) is sort of a "system" that protects the "true crown". You want to try to make sure that the true crown never gets any dings, or is hit. For this reason, this whole system is referred to as the crown, and there are several different styles. Most people will say there's basically 3 styles of crowns, and the rest are sort of variations or melding of the 3. There are Rounded, Target (11 or 9 degree), and Recessed/Stepped/90 degree Crowns. Here is a photo to kind of give you an idea of what those look like.

[Image: barrelcrowns.jpg]

You see lots of "rounded crowns" on hunting rifles, and older rifles. Personally, I don't like them as much, although they can look quite handsome. For the most part, the "true crown" is almost flush with the end of the barrel. The edges are rounded (radiused) and look really nice, and the true crown is just barely lower than the rest of the crown. The trouble is, if you set the barrel down muzzle first (which you shouldn't do in the first place), there's not a lot of wiggle room to keep something from touching the true crown and damaging it.

Lots of people consider and prefer the "11 degree target crown". The nice thing about this is that the true crown is usually deeper in the barrel, so it's more recessed and down in a depression. This keeps the true crown further back away from being flush with the muzzle, and offers a bit more protection. Target crowns are renowned for how evenly and nicely they vent gases around the bullet. It's part of the reason why most competition and target shooters prefer it. Something I view as a slightly downside to it is that fact that it sort of funnels everything to the true crown. If you set the rifle down muzzle first, and something hit the crown, it would basically be funneled TO the true crown and could ding it. Again, ideally you don't want to set the rifle down muzzle first on anything, and if you hold to that rule, it doesn't matter.

The last style is referred to as a "recessed", "stepped" or "90 degree" crown. The reason it's referred to in this manner is because the crown is recessed, and it's usually done so in what is a pretty obvious "step down". The cuts right at the true crown meet at a 90 degree angle, and they do not go into the true crown on an 11 or 9 degree crown. So that's why some people refer to it as a 90 degree crown. There are several different styles that have come from this, and I'll post some pictures of them. Some of the styles include multiple "steps" or recesses, and not just one.

[Image: rs_kimber-model-8400_d.jpg]
This is a pretty traditional recessed crown. It has a pretty deep recess, and very steep 90 degree edges. The distance from actually being flush with the muzzle is pretty obvious. Some target shooters do not like this crown because they believe the steep angles can create turbulence in the gases as they hit the edges and are turned back inward towards the bullet. Whether the bullet is still there during this time, depends on a lot of factors, including the bullet design, powder, seating distances from the lands, etc. The other thing to remember is that the bullet is also surrounded by a supersonic shockwave since it's breaking the sound barrier inside the barrel, and the turbulence likely has very minimal if any affect.

[Image: MVC-265F.jpg]
The machining in this photo leaves a LOT to be desired, so please take that into consideration. I did want to show you this crown because it is sort of a cross between an 11 degree crown and a recessed crown. You'll see the step and the deeper recess, but instead of having 90 degree edges, it has some 9 or 11 degree shoulders as it transitions in the steps. This style is personally my favorite because you get the benefits of a deep recess, a flat area for some contact to stop on and not be funneled to the true crown, and because of the angles they also vent gases very even and cleanly around the bullet. There are some differences here in that some people leave the true crown completely at 90 degrees and then the 11 degree is only at the step of the recess. Others will do 11 degree at the true crown, a nice flat stepped recess, and then 11 at the transition to what people would consider the first true "step". This crown has the 11 degree at the true crown, as you can see that there is a small angle where the rifling meets the barrel.

[Image: 198230_412244878813899_1744048769_n.jpg]
This is actually a thread protector over a muzzle that has already been crowned. Still, barrels CAN and ARE crowned this way, and this is the multi step style crowning that has the 11 degree angles between the steps. While there are 2 steps in this picture, you'll notice in this one that there is NOT any angle where the rifling meets the barrel. So it's like the first picture of the recessed crown in that where the rifling meets the barrel is a true "90 degree crown" and then there is angles on the steps (both of them). You'll also see variations where the outsides can be rounded like the rounded crown, even though it's a recessed crown.

In the end, ANY of the crowns shown are very effective. Honestly, I've never seen one shoot better than the other if they are done properly. Some will argue that one style will hold up better than others, and that's why lots of us tactical shooters will prefer a stepped style crown over the other styles. Honestly, it all ends up being a personally preference, and a lot of it is merely cosmetic. I would never let the cosmetics keep me from buying one brand of rifle or barrel over another IF (can be a big if), the true crown is intact and in good shape. Does this help clarify the crown? If you need some elaboration on them, please feel free to ask. As you can see, they can vary and be combined in interesting ways.
Tomcat088, proud to be a member of pa2a.org since Sep 2012.
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#4
That was a good post about Crowns. I know that a gunsmith messed up the Crown on my Rem model 700 in 300RUM and it was all over the paper after that. And it ended up costing me a new barrel.
Shorty, proud to be a member of pa2a.org since Nov 2012.
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#5
Shorty;40379 Wrote:That was a good post about Crowns. I know that a gunsmith messed up the Crown on my Rem model 700 in 300RUM and it was all over the paper after that. And it ended up costing me a new barrel.

You should have just taken it to someone else to have it re crowned.
The only reason I can think of to not re crown an otherwise good barrel would be if it was already at the minimum legal length (16") and I really doubt that you were there.
There are three types of people in the world:
Those who make things happen,
Those who watch things happen,
And those who wonder what happened.
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#6
What does a re-crown usually cost?
gascolator, proud to be a member of pa2a.org since Nov 2012.
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#7
gascolator;40455 Wrote:What does a re-crown usually cost?

I don't know, I've only had that service done when I had other work done and I looked at the total price. The most recent was a 6.5X55 Swedish Mauser that someone butchered. I had the barrel cut and re-crowned, rear sight ring removed, drilled and tapped for scope mounts, set back 2 threads, re-chambered to 6.5X55 BJ Ackley and headspace checked. My total bill was right around $100.00. (I have the chamber reamer so that helped keep the cost down).
It's not a real expensive operation.
There are three types of people in the world:
Those who make things happen,
Those who watch things happen,
And those who wonder what happened.
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#8
mauser;40449 Wrote:
Shorty;40379 Wrote:That was a good post about Crowns. I know that a gunsmith messed up the Crown on my Rem model 700 in 300RUM and it was all over the paper after that. And it ended up costing me a new barrel.

You should have just taken it to someone else to have it re crowned.
The only reason I can think of to not re crown an otherwise good barrel would be if it was already at the minimum legal length (16") and I really doubt that you were there.

I did take it to another Gunsmith and had it re Crowned and was still all over the paper. Anything less than a 26 inch barrel on a 300RUM is unacceptable.
Shorty, proud to be a member of pa2a.org since Nov 2012.
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#9
Shorty;40556 Wrote:
mauser;40449 Wrote:You should have just taken it to someone else to have it re crowned.
The only reason I can think of to not re crown an otherwise good barrel would be if it was already at the minimum legal length (16") and I really doubt that you were there.

I did take it to another Gunsmith and had it re Crowned and was still all over the paper. Anything less than a 26 inch barrel on a 300RUM is unacceptable.

You need to find some new gunsmiths.

Crowning does not remove inches off a barrel, and if it does, the guy does not know what he is doing.

______________________________________________________________
Even if it were 16", using a recessed crown would not shorten the overall length. And if it did, threading and permanently attaching a muzzlebrake would solve that.
Some people need to read this book: http://www.amazon.com/dp/1936976021/ref=...jwbZH1GAZF

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#10
39Flathead;40589 Wrote:
Shorty;40556 Wrote:I did take it to another Gunsmith and had it re Crowned and was still all over the paper. Anything less than a 26 inch barrel on a 300RUM is unacceptable.

You need to find some new gunsmiths.

Crowning does not remove inches off a barrel, and if it does, the guy does not know what he is doing.

______________________________________________________________
Even if it were 16", using a recessed crown would not shorten the overall length. And if it did, threading and permanently attaching a muzzlebrake would solve that.

There is more to the story. I had a muzzle brake put on and from that point the rifle would not even come close to shooting good groups. I am talking about 10 inch groups at 50 yards. Tried new scope and diff ammo nothing fixed problem. Smith would not stand behind his work. Took it to diff GunSmith he re-crowned barrel with Diff Brake, glass bedded, jeweled trigger, and pillar bedded and would still not group. Then I said the hell with it and had new Barrel put on and now it will shoot MOA all the time.

And that is the rest of the story.
Shorty, proud to be a member of pa2a.org since Nov 2012.
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