There are a lot of Enfields with worn or damaged crowns, and owners looking to counter-bore or re-barrel - is it necessary ?
Here is an interesting article suggesting that maybe it is'nt always necessary
The Over-Rated Crown
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There are a lot of Enfields with worn or damaged crowns, and owners looking to counter-bore or re-barrel - is it necessary ?
Here is an interesting article suggesting that maybe it is'nt always necessary
The Over-Rated Crown
If the .301" gauge runs freely then leave it alone is my option
I don't think I've come across an Enfield that appeared to have its shooting affected by crown damage. No4s in particular very frequently have dents and dings around the crown, but it doesn't seem to have any noticeable effect. Same goes for pitting in the couple of inches at the muzzle.
Interesting results especially with such ugly looking damage to the muzzle/crown. 'Hard to believe the results. Now, an explanation would be great as I have spent considerable funds and time and anguish recrowning several rifles for negligible improvements over what were essentially fine shooting Swedish Mauser rifles........I did the re-crowning simply because I believed/had been educated to believe it had to be done and that it was necessary and for aesthetics. Is recrowning primarily an issue to improve long range accuracy? Does it have practical value for short range shooting/hunting?:sos:
I've been educated to the same end. Re crowning was the only way to re establish accuracy. Is this so much balloon juice?
Me too - thats why I posted it.Quote:
Originally Posted by browningautorifle
Maybe one of our 'engineering' type forummers has an old rifle they dont mind butchering and could duplicate the test and see if the results match ?
I have burnished the dinged crowns of a few rifles, with a good cosmetic results. I am too poor a marksman to really know if the group tightened, but I was pleased. I used a long, thick, countersunk brass wood screw, valve grinding paste to go between the screw head and the crown, a power drill/driver to spin the screw, and an aluminium sleeve to protect the bore. I ended up with a sparkling smooth crown and absolutely no damage to the rifling. I can explain in more detail if anyone is interested.
Surely............ Leaving aside the .306 or .307 gauges that are simply barrel/muzzle WEAR gauges, then if the actual BORE gauge of .301" runs smoothly '.... without let, hinderance or hesitation' (or .297 in the case of the 7.62's) then THAT is the final arbiter.
Or am I missing something in the telling here? After all, if whatever it is you're fretting about ain't impeding the gauge, then the bullet MUST be good to go.
A bbright shining crowned muzzle might LOOK good but it ain't doin' nothin!
The perceived wisdom seems to be that ' having a nice shiney, perfect crown / muzzle' helps accuracy - a damaged crown / muzzle has a negative effect on accuracy.
My very limited understanding - what I have been told - is that if the last inch (for example) is bit chewed up with little of no rifling then the bullet will 'flop about' as it comes out of the muzzle, will be unstable and accuracy will be lost.
I suppose you could say that a .306 (or .301) gauge would run thru' a .500 barrel, but, the accuracy would be pretty poor
Alan....... It's correct that it's what's ahead of the bullet that counts, not what it's left behind. But you're missing the point. We're on about muzzle crowning. Muzzle crowning is a totally different matter to a worn/corroded/shot-out/cordworn muzzle. You ain't comparing or thinking like with like.
As told to me, the pressure wave which both precedes and follows the bullet needs to expand smoothly and symmetrically at the tip of the barrel. A ding on the crown can give an assymmetry in the suddenly-expanding pressure wave. This in turn can act on the bullet and disturb it as it exits the barrel. Thus, the bullet doesn't touch the ding, but is nonetheless affected by the ding. Now, if bullsh*t was told to me, then I do apologise for repeating it here and would appreciate to know the truth. But, as I stated above, it is simplicity itself to burnish a ding out of the crown.
I suspect that the answer is in the CONSISTENCY of the "crown".
If some dopey digger has used a dirty pull-though poorly for some time, there will be "wear" to both the ends of the lands and the grooves.
Thus, the gases exiting at "ludicrous speed" from behind the bullet will generate an "eccentric" blast cone that briefly races past the bullet as said projectile exits the muzzle. "Gas erosion" of the "crown" is a factor.
NO bullet is perfect. Thus the bullet will be precessing (making a small spiraling motion) as it leaves the muzzle. Enveloping it with an eccentric shock wave is probably not helpful.
HOWEVER, I suspect that all of the preceding applies MUCH more to the dreaded boat-tails than "proper" Mk7 bullets. That little cone of a boat-tail means that any following gases have a GREATER time during which they can bear on the bullet. Many hard-core bench-rest types use flat-based bullets for "short ranges" and only reach for the boat tails when working 500-1000 yards. Additionally, forming a boat-tail involves the use of another die-station in the machinery and thus adds another process that can result in tiny, but significant eccentricities in the core and particularly the jacket, and ultimately, balance. Again, this is most noticeable at "shorter" ranges.
Finally, if your trusty Lee Enfield barrel has been fed a steady diet of Cordite-fueled Mk7 ball, its throat WILL be eroded to some extent. Gas "blow-by" similar to that which occurs at the muzzle WILL also occur briefly at the throat upon ignition. Furthermore, as "sporting" boat-tailed bullets have a "solid" base, they are less likely to "bump-up" when kicked in the backside by many thousands of PSI. Think of using such boat-tails as applying a tiny, circular plasma cutter to the inside of your barrel.
That sums it up.Quote:
Somebody want to explain these results? How can a barrel with a crown that has been absolutely destroyed shoot under ¾ MOA? Beats me. I saw it and I still don’t believe it. Well I do believe it because I saw it, but I can’t explain it. And since I can’t explain it I am going to continue to insist on having as perfect a crown as is possible.
Now that we've been all through this, that statement seems like a bit of "Pig headedness". I still believe that when producing a barrel, the end result should be as cosmetic as possible...clean and sharp.Quote:
Originally Posted by Surpmil
An interesting thread, think there will be a few on either side of the fence on this one, I,ve only re crowned a few full bore barrels but this was due to visible damage etc and the owners request, I've done plenty of my own and heaps of Ruger 10/22 and similar barrels after length reduction and cut a 11 degree crown and had no complaints, (yet).
After working on very big oil fired boilers, that require atomising steam for a cleaner burn, a vital bit of kit is the swirl plate which..... anyway when blocked or semi blocked can have a dramatic effect on efficiency, so I,m in favour of clean sharp ( like BAR) machined edges (but that also goes back to my apprenticeship)
Thanks for bringing this up Alan. I've always heard how important this was, even did the brass screw and valve compound jobby on a couple rifles... Didn't notice anything except an incongruent look in the finish of muzzle :) still not sure about the stressed importance.
Cheers