Is this crown acceptable? (pics)

[pronoun 1]

Hi everyone,

 

Working on a new upper build. Picked up this barrel, and upon inspection noticed the crown seems to be canted to one side. Wanted to get your opinions on whether this is "standard deviation" so to speak, or if it needs to go back. I've asked around but gotten mixed answers. Here are a few pictures. The piece of tape is for point of view reference. As you can see, the crown is much deeper in the second picture.

 

Edit: Im asking because obviously I can't put it on a gun to test it first, since all NJ barrels need to be pinned.

 

Thanks for your help

 

[PK90 3,570]

I do not think it is an issue.

[Old School 611]

Personally...I would send it back.....I've not noticed that as bad before

 

Nick - can you see a variance? I can't.

 

Nick- Run it between centers,,,

[Old School 611]

The crown should be evenly concentric ....

 

I think you guys are looking at the "lead thread" which will be closer to the bore axis.

[Old School 611]

Frank...it's a new barrel.....would you build on it and expect moa accuracy....IMHO...and all I have ever been told...crown concentricity is key to bullet stability and accuracy .... I could be wrong...but why risk it... Again. * I * would send it back....

 

I can't see a thing in those pics. Really have to throw it in the lathe if there's any doubts.

 

It's things like this that frustrate me. People thing AR's are an "erector set" and you throw parts together.

 

Gotta look at stuff gotta measure.

 

Do you what understand what I'm saying about the lead thread? Because the thread has a lead the face of the crown is not going to be the same width all the way around.

[Pew Pew Plates 358]

I see it...

 

I dont like it...

[Dan 177]

I see it, seems the crown is set back further into the bore on the 2nd pic. Not sure how it would impact accuracty, if it was me I'd send it back.

[Old School 611]

I see it now. The angle the crown is cut at is wider on one side. I don't like it.

 

I know Colin's other rifle well. It's a tack driver so build the best rifle you can, because to stand up to his other rifle it needs to be pretty good.

[vjf915 456]

I see it. If it can be seen that easily, I would without a doubt send it back.

[specopsscout 26]

Can't tell from the photo. Sometimes the barrel can be drilled slightly off center and the crown is concentric to the center of the bore, not the barrel. The barrel can still be accurate. You'd be surprised at how well some truly crappy barrels I've seen shot.

I knew one idiot and former friend that cut his Remy 700 PSS barrel down to 18" himself with a hacksaw, and then used a hand drill to recut the crown. It looked like absolute hell, but still shot to about half MOA at six hundred yards.

Still, I'd return it for a new one, but that's just because I'm anal as hell(read OCD), and that lack of concentricity would drive me nuts. Even if I couldn't see it under a muzzle break, I'd know it's there...

[heaterbob 53]

all the crown does is break the edge of the bore so there is no sharp edge, i doubt it would effect accuracy.

[Old School 611]

The only issue I really see is concetricity with the bore of the muzzle brake. That is an issue enough that if you put enough good quality uppers together you can get a muzzle brake reamer to make the bore of the brake concentric.

 

 

[Old School 611]

That is not all it does......

 

Hey Nick...SOB...We agree... Just look at any crown that is a a square target crown or 11* crown. An even dispersion of powder residue around the crown is an indication of a good crown.

[PK90 3,570]

As a point of reference, pull out your dioper and look at all the barrels in your collection. You might be surprised.

[Old School 611]

As a point of reference, pull out your dioper and look at all the barrels in your collection. You might be surprised.

 

On the money Paul! Ever look at military recrowns...LOL

[Old School 611]

I am NOT saying that certain rifles of many makes and models have differing crown types or none at all....

 

What I am saying is that for a new barrel why take a chance....?

 

Wisdom indicates that crown not only shield the lands and grooves from damage (we all know how bad nicks can be), but they also serve additional purpose....

 

It does not take much to search for more detailed information on this...HOWEVER to make it easy here are some 'web excerpts':

 

"It aids in the bullet and gasses leaving the barrel cleanly and uniformly.

Improving accuracy.

 

The bullet is under complete control of the barrel until it exits and any unevenness in

the gas escaping can push the bullet off course.

 

When a proper crown is used It is sharp and square to the bore. This is the reason it is best

not to clean from the muzzle end of the barrel if possible because you can damage the crown

and hurt the accuracy."

 

"With M14/M1 Garand barrels a good rod and muzzle guide set-up is especially important as all the cleaning must be done from the muzzle. Even slight damage, or eccentricity, to the barrel crown is extremely detrimental to accuracy."

 

"

Crown

 

The crown is the muzzle face of the barrel. The crown's integrity is critical for two reasons:

1. It is the last part of the firearm touched by the bullet before it exits.
   
2. As the bullet clears the crown, it will release upwards of 5,000-10,000+ PSI of back pressure, which must be as uniform as possible.
   

While many barrel manufacturers recess the crown to protect it from accidental damage, it can still be damaged over time by cleaning rods that are too hard. It is also not uncommon for factory crowns to be cut slightly off-center, so that one side of the bullet exits slightly earlier than the other, and this will result in the bullet being pushed away from that side, causing a significant deflection in its path. A crown may be re-cut with relative ease, and this can fix any problems caused by a defective or damaged crown, by ensuring an even release of the bullet.^[39]"

 

^{and the list goes on and on and on ................}

 

 

 

Very nice Nick, You did very well on yourt homework assignment.

 

Now I just hope the noobs read this so we don't have the same question next week.

[Shane45 807]

Bottom line, with that much varience, something is significantlhy off somewhere. Bore axis to barrel, face of barrel to bore, crown to bore, crown to barrel, something is amiss, send it back.

[Dan 177]

Now I just hope the noobs read this so we don't have the same question next week.

 

Lil' bit of an elitist remark there Old School?

[Old School 611]

Lil' bit of an elitist remark there Old School?

 

Not at all Dan. Learning to research is important. Obviously Nick knows how to research.

[pronoun 1]

Thanks for all the good info guys.

 

I posted this same question on another forum too, and it seemed to stir up a similar debate. The bottom line is I am not confident in the barrel, and whether or not it is a mechanical flaw, I want to have it checked out so that I can enjoy shooting my rifle instead of wondering if it could be better.

 

Steve from ADCO has offered to test fire the barrel since assembling without a pinned comp in NJ would be a no-no. I took him up on the offer and will update once we get some empirical data in the form of a test target.

 

In the meantime I called Daniel Defense, and sent them the two pictures in my OP. They said it "looks fine." We'll see what happens.

[Dan 177]

Not at all Dan. Learning to research is important. Obviously Nick knows how to research.

 

Isn't posting a question on a forum where lots of experts hang out and enjoy answering such kinds of questions a form of research?

[Old School 611]

Isn't posting a question on a forum where lots of experts hang out and enjoy answering such kinds of questions a form of research?

 

No