if i recrown my factory barrel will it shoot more accuratly?if so what find of crown?also what else can i do to make it shoot better.i shoot a 7mm rem mag model 700 adl.

Some people think so but since this is my post I will say not unless the existing crown is seriously defective.

Most M700's shoot decent if not good without a lot of fuss. Best single thing you can do is tune or replace the trigger. Next, make sure the barrel is not intermittently rubbing on the stock -- the barrel should either be pressure bedded or free floated. Check the bolt lugs and lap if necessary. Try different bullet weights.

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Some people think so I will say not unless the existing crown is seriously defective.

Yes...of course....why else would a new crown fix anything unless the previous one was defective in some manner.

Personally, I've never seen a bad (defective) crown in my life!!!

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Originally posted by vapodog:

Personally, I've never seen a bad (defective) crown in my life!!!

You haven't either look much, or, you need better light! They're like bad drivers, they're all over the place.

Vapodog:

You wann see a bad crown? I'll show you one, it was on that rifle I did the other day with the Bondo bedding job that was done by that "professional" from Gander Mtn.

I have read that button-rifled barrels sometimes lose "flakes" of metal at the muzzle over time. A new crown will improve accuracy in such a situation.

I just walked away from the lathe to type this. I have a brand spanking new Winchester 70 in the shop presently being "improved". And as is the rule in this shop for ALL accuracy related jobs, the crown is the first issue addressed. For laughs, I dialed in the outside of the barrel and watched as the bore wobbled like an old, out of balance wheel. You don't want to stare at something like that for too long or you'll lose your breakfast.

Now to be fair, Remingtons are no better. In fact, when a Remington crown is out of whack, they're visibly worse. They not only wobble, but they rock to and fro. Seems like that last little chamfer they add usually kills it. If you look the chamfer over closely as you rotate the barrel, you will almost ALWAYS, 99.5%, see that that chamfer is heavier on one side than the other. It's like someone walks the assembly line with one of those Hornady chamfering tools, you know the kind you use for deburring case mouths, and gives each Remington muzzle a little twist for good measure. Have a close look next time, only under good lighting.

The important aspect of any crown is that the bore ends up the same length all the way around, if that makes any sense to you.In other words, a line drawn through the juncture of the crown and the bore on both sides will be perpendicular to the bore centerline.
In the case of the typical radiused crown as found on most sporters,this intersect between bore and crown will be just fine providing the bore was used as the reference when the crown was cut. If the outside of the barrel was used and was eccentric to the bore (common) then the crown is crooked. If the radiused crown is crooked in this way but finished of with a piloted 60 degree center reamer, it might not look perfect but can be functionally so.
A flat recessed crown is more likely to be perpendicular to the bore and, if not, the error will be less significant.
Regardless of the type of crown used, I think finishing with a slight bevel is beneficial since it will minimize possible cleaning rod damage at the crown.
FWIW, I have used all sorts of different crowns over the years (flat, 11 degree, radiused,counterbored, etc.) and have seen no real difference in performance. I use flat recessed crowns more than any other on both sportersand target rifles just because people seem to like them. I use radiused crowns on my own hunting rifles just because it looks right on the type of rifles I usually make for my self (kind of a 1950s sporter as built by a semi skilled maker sort of thing).
One thing is certain regarding recrowning, if it is well done it never does any harm. If itis poorly done it seldom does any good. Regards, Bill

The reason I said the crown is not critical is because Dr. Mann experimented with mutilated crowns and found that while the POI did change, there was little effect on group size.

If anyone has any data to the contrary, please share it with us.

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Originally posted by popenmann:
The reason I said the crown is not critical is because Dr. Mann experimented with mutilated crowns and found that while the POI did change, there was little effect on group size.

If anyone has any data to the contrary, please share it with us.

Are you sure he wasn't talking dental crowns? Because I could see where a mutilated dental crown might not affect group size. But their ain't no way a mutilated rifle crown won't affect groups size.

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Originally posted by malm:
I just walked away from the lathe to type this. I have a brand spanking new Winchester 70 in the shop presently being "improved". And as is the rule in this shop for ALL accuracy related jobs, the crown is the first issue addressed. For laughs, I dialed in the outside of the barrel and watched as the bore wobbled like an old, out of balance wheel. You don't want to stare at something like that for too long or you'll lose your breakfast.

Now to be fair, Remingtons are no better. In fact, when a Remington crown is out of whack, they're visibly worse. They not only wobble, but they rock to and fro. Seems like that last little chamfer they add usually kills it. If you look the chamfer over closely as you rotate the barrel, you will almost ALWAYS, 99.5%, see that that chamfer is heavier on one side than the other. It's like someone walks the assembly line with one of those Hornady chamfering tools, you know the kind you use for deburring case mouths, and gives each Remington muzzle a little twist for good measure. Have a close look next time, only under good lighting.

When cutting a new crown,one is working off the bore,this is what should be centered. Since the crown also is working off of the bore. Not the tapered outside of the barrel.How can one align the bore off of a tapered outside of the barrel is beyond me and i have done barrel jobs for 40yrs. van

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Asked by Van: How can one align the bore off of a tapered outside of the barrel is beyond me and i have done barrel jobs for 40yrs. van

It's pretty easy once you get the hang of it. You use a 4 jaw chuck, and you loosen one jaw and then tighten the oposite, working your way around until the bore is running true. Pretty straight forward. Of course with a factory barrel, the outside is likely to be running a bit out of whack with the bore.

Sometime you might need to true the outside of the barrel so you can precisely match a factory barrel with a thread on muzzle brake. Of course this is done AFTER the crown and threads have been cut with the bore centered. How have you been doing it?

40 yrs and not guaranteeing the crown is concentric and perpendicular to the bore. Where did this guy go to school? DOn't mean to be sarcastic, but if you are just setting the barrel up on the outside of the muzzle in the steady, how do you even keep it round. Most barrels are polished on the exterior with a rotating belt sander and most finish up out of round also, let alone not concentric to the bore. When I do a crown, it is always set up with the bore indicated concentrically with the lathe axis and parallel to it.

I just had my Mod 70 375H&H recrowned & restocked. I don't know what worked but from shooting 2" groups I am shooting 1/2".

i beleave you would have to have a long needle indicator to indicate the i.d. of the barrel strait.i dont no how close it would have to be running but i would say within .001 frount to back.i would think the best way to cut the crown is to use a boring bar and set your compound to 11 degrees and then break i.d. with a sharp 60 degree centerdrill about .02 to .03 long.then polish with some fine grit emery cloth.

Van:

I just went back and re-read your post. I misread it and apologize for giving you a bad rap. You are indeed correct.

Jim

quote:

Originally posted by malm:
.....

Now to be fair, Remingtons are no better. In fact, when a Remington crown is out of whack, they're visibly worse. They not only wobble, but they rock to and fro. Seems like that last little chamfer they add usually kills it. If you look the chamfer over closely as you rotate the barrel, you will almost ALWAYS, 99.5%, see that that chamfer is heavier on one side than the other. It's like someone walks the assembly line with one of those Hornady chamfering tools, you know the kind you use for deburring case mouths, and gives each Remington muzzle a little twist for good measure. Have a close look next time, only under good lighting.

Remington M700 with factory crown: