Gunsmithing Does this muzzle look right?

[acttacus]

So a friend bought a KIDD 10/22, and showed off some pictures to me yesterday. The first thing I noticed was the serrated crown on the muzzle. I've told him that it looks a little off but he insists that it's suppose to look like this.

What do you guys think? From my understanding a crown is suppose to be mirror smooth and uniform, and not jagged. Is this a new trend that I haven't heard of? If so please enlighten me.

Thanks

 

[mscott]

Re: Does this muzzle look right?

Looks like it was crowned with a coutersink or something?
Is there any rifling in there?

 

[acttacus]

Re: Does this muzzle look right?

I'm not sure. He lives in New Zealand, and just sent me some photos.

You meant it could be that the bore was machined back, so crown was actually recessed back in the barrel? interesting~ I"ll ask him.

He said that this is a KIDD bull barrel.

 

[Country]

Re: Does this muzzle look right?

There is too much chatter on the surface of the cut . You want the internal chamfer of the crown to be as neat as possible. I would say it was chamfered after it was turned down and threaded allowing some flexing and vibration. It does not have to be mirro smooth but just a good finish . The ends of the lands and in the grooves should be neat and without burrs and you only need to cut the chamfer deep enough to just kiss the end of the lands. That chamfer is way too excessive.
A few shots usually clears any small burrs but if the end off the land is burred up a good deal from cutting too far onto it with a poor tool and technique then those burrs may stay for some time . It needs to be put back in the lathe centered and the whole chamfer turned off with a new sharp single point tool and chafered again with a single point tool , run the lathe fast . Slow it down some then set the shoulder back by the same amount.

 

[jeepguy242]

Re: Does this muzzle look right?

that looks like some crap that i did when i was trying to countersink for a rivit when i didnt know what the hell i was doing...

 

[acttacus]

Re: Does this muzzle look right?

Thanks, that makes sense.

so is the chatter going to have a big effect on accuracy? From my experience I just can't see how this will not affect accuracy~

Thanks

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Country</div><div class="ubbcode-body">There is too much chatter on the surface of the cut . You want the internal chamfer of the crown to be as neat as possible. I would say it was chamfered after it was turned down and threaded allowing some flexing and vibration. It does not have to be mirro smooth but just a good finish . The ends of the lands and in the grooves should be neat and without burrs and you only need to cut the chamfer deep enough to just kiss the end of the lands. That chamfer is way too excessive.
A few shots usually clears any small burrs but the chatter wil remain . </div></div>

 

[Country]

Re: Does this muzzle look right?

It's one of those things that you can't be sure until you shoot it. However if it has raised burrs on the ends of the lands it will affect accuracy . If the chatter upsets the release of the bullet by uneven channeling of the powder gass pressure then that can upsett accuracy also.
If it was done by a professional then I would take it back and ask them to re machine it and you want it all done in the lathe with the same center setup.

 

[jeepguy242]

Re: Does this muzzle look right?

i'm not sure if it will effect the bullet exiting the barrel, but it may effect the gasses coming out and these might effect the bullet, but that is just a wild ass guess, i'm by far NO expert, but i bet there are others here that can tell you...

 

[Country]

Re: Does this muzzle look right?

I blew your photo up 300% and it looks a nasty out of shape job to me. I will be very surprised if it does not affect accuracy to some degree .
It just goes against what most try to achieve when doing a crown .
I rekon they may have forgotten to do the crown in the lathe and did not want to re center it in the spindle all over again so just used an external chamfer tool . If the crown is recessed back and it is neat and straight then the external crown may not affect accuracy . It's possible as I can't see any lands or grooves in the photo .

 

[jeepguy242]

Re: Does this muzzle look right?

i understand what you are talking about, by recessing the crown, but could you explain why anyone would do that? what would be the advantages other than the obvious of protecting the crown from getting dinged up.

 

[acttacus]

Re: Does this muzzle look right?

I'm just a little surprised when I saw the photo. I think Country may have it spot on about forgetting to do the crown and can't be bothered to re-center the barrel onto the spindle. so the crown was made with an external chamfer and recessed into the bore.

This thou, is kind of unacceptable in my book, considering it's suppose to be a $200+ match barrel.

Either way, my friend said that he's put about 100rds down range and the accuracy is acceptable~

 

[jonaddis84]

Re: Does this muzzle look right?

I dont know if anyone pointed out yet or not, but I dont think the crown is even visible in this picture. For whatever reason, the crown is somewhere further back from the end of the barrel now. Its been bored back and the chatter you are seeing is definitely from a countersink, but that wont affect any accuracy. The question is what does the actual crown look like?

Assuming its 1/2-28, that hole in the end looks like its about .300. Surprising that chatter is there because the thread surface finish is excellent.

 

[LRI]

Re: Does this muzzle look right?

Tool chatter.

Too much RPM
Dull Tool
Too slow a feed
No rigidity in the setup



Just pick one.

Best fix is to single point a new crown if it doesn't shoot well.
I'd personally shoot it first just to see. Won't hurt anything.

C.

 

[gunnergirl81]

Re: Does this muzzle look right?

Well, first. If we assume thats a .920 od barrel with 1/2-28 threads then thats a huge bore. I'm guessing thats the lightweight aluminum sleeve we're looking at and the barrel liner is pushed back, or cut back. You can see the twist mark on the inside where someone was turning on the liner while installing or removing it.

If everything I'm guessing is accurate then that chatter at the "crown" will have zero effect on anything. The crown on the liner is all that matters. The only question here is why is the liner not up even with the end of the barrel sleeve?

I posted a thread a while back about Tactical solutions 22 barrels and have almost the same pic (minus the crappy chatter)in that thread.

 

[acttacus]

Re: Does this muzzle look right?

Oh wow, so you're saying that this barrel is actually made of two barrels, and aluminium sleeve and a barrel liner? That I have never heard of. The rimfire world sure is weird. Is this just to cut back in manufacturing cost or is there a functional purpose to this?

Thanks for all the response, I'm learning~

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kenda</div><div class="ubbcode-body">Well, first. If we assume thats a .920 od barrel with 1/2-28 threads then thats a huge bore. I'm guessing thats the lightweight aluminum sleeve we're looking at and the barrel liner is pushed back, or cut back. You can see the twist mark on the inside where someone was turning on the liner while installing or removing it.

If everything I'm guessing is accurate then that chatter at the "crown" will have zero effect on anything. The crown on the liner is all that matters. The only question here is why is the liner not up even with the end of the barrel sleeve?

I posted a thread a while back about Tactical solutions 22 barrels and have almost the same pic (minus the crappy chatter)in that thread.</div></div>

 

[LRI]

Re: Does this muzzle look right?

I'd bet a buck it's a one piece barrel.

Your looking at/witnessing something called "surface speed".

When a tool is at the center of a face and the lathe is spinning at "X" rpm the speed of rotation in FPM is Y. As you pull the tool out to the edge the rpm of the lathe is still "X" but now the speed of rotation is Z. At center the surface speed is essentially zero as you get to a point where no matter how much rpm you use, the part isn't really moving. That begins to change progressively the further from center you go.

Think merry go round as a kid. We got our asses kicked trying to hang onto the outside, but it was much easier in the center cause we weren't moving nearly so fast.

With a manual lathe it's not usually practical to vary the rpm of the spindle with the machine running. With a CNC its pretty simple with the addition of a couple lines of code.

M03S2500
G96S600
G50S2500

M3 turns on the spindle clockwise. S2500 is 2500rpm
G96 turns on CSS. S600 sets it at 600 feet/minute
G50 limits the spindle to 2500 rpm max so that you don't over rev a chuck or part. Failure to do this could blow up a chuck or have a part come wizzing out of the machine. The control is going to do its diligence to make that machine buzz at 600SFM all the way to center. Very possible to run it up to the limit of its RPM capacity.

If this were done on a CNC the RPM of the spindle would vary with tool position, but the surface speed would remain constant.

Why they called it "constant surface speed".

When this isn't done, it can create "lines" on a face similar to a vinyl record. I speculate this is what Kenda is looking at and summarizing to be a sleeve of some sorts.

Pretty sure it's not though.

Hope this helps.

C.

 

[300sniper]

Re: Does this muzzle look right?

that would be the case for any tooling lines on the shoulder and square part of the muzzle but i think what kenda is noticing is the lack of rifling and the large bore for a .22.

 

[gunnergirl81]

Re: Does this muzzle look right?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">that would be the case for any tooling lines on the shoulder and square part of the muzzle but i think what kenda is noticing is the lack of rifling and the large bore for a .22. </div></div>

Correct.

But...

Its not a guess based on anything like Chads experience (or big word science based thingys). I'm not even sure I understood anything in your last post Chad. You're just too damned smart.

Instead it is based on me holding a barrel that looked almost identical just a few weeks ago. Lemme see if I can find the thread.

 

[gunnergirl81]

Re: Does this muzzle look right?

Here it is:
http://www.snipershide.com/forum/ubbthre...193#Post2822193

 

[HuskerP7M8]

Re: Does this muzzle look right?

It’s a one piece Lothar Walther barrel threaded for a can or silencer with an approximate 0.32” counterbore. There’s no liner and the rough tooling on the crown of the counterbore will have no effect on accuracy.

Landy

 

[buffybuster]

Re: Does this muzzle look right?

If that barrel is threaded 1/2"-28thd, no way that is .22cal. That has to be some kind of bloop tube/very deeply recessed muzzle crown.

 

[Sportin Wood]

Re: Does this muzzle look right?

Easiest way to tell.... Email Kidd the pic and ask them!!!

 

[Country]

Re: Does this muzzle look right?

The surface feet per minute would be very constant at the point of the crown chamfer as it is only a very fine short cut so the chatter came from bad machining technique in general possibly including Speed , Feed and tool choice not the change in SFPM from radial center to outside as there would not be much right on that thin edge that has the chatter.

 

[scrtshtr2286]

Re: Does this muzzle look right?

alrighty then, can someone show me what the numbers mean when you thread a barrel in different sizes. I understand the 28 threads per inch means it's going to thread almost an inch of the barrel with 28 threads. What I don't understand is what the 1/2 or 3/4 part of the equation means. Any help?

 

[LRI]

Re: Does this muzzle look right?

The first set of numbers means diameter.

Imperial: 1/2- . . . means the thread will measure a nominal diameter of .500" or 1/2" in diameter.

In practice this doesn't work. It'll be more like .490, .495, .498, etc. You must leave a little clearance on the crest (peak) of the male thread.

The same applies for metric. 13mmX. . . Means 13mm diameter.

Second number is the pitch. It's expressed in two ways. A whole number generally means the # of threads per inch. Another way is to express the true pitch in thousanths.

Say you have a 1/4-20 bolt. 1/4 is the OD and 20 is the threads per inch. 20 threads per inch has a pitch of .05 (.05x20='s 1 right?)

This is the number I'm most concerned with as its how stuff gets programmed on my machinery.

Metric is actually pretty cool in that its simple to figure tap/drill sizes. Take the diameter, subtract the pitch, and you have the hole size.

Example:

20mm x 1.5

18.5mm is the hole you'd want to drill for the tap.

Imperial is a bit more involved, but you can do the same thing.



Use the following formula for finding the correct drill bit size: Dh = Dbm -- 0.0130 (percentage of the full thread desired/ Ni). Dh is equal to the drilled hole size in inches. Dbm is the basic major diameter of the thread, in our case 0.252 inches. The "percent" of full thread desired is your choice, but a good number is 70 percent to 85 percent depending on the material being used. "Ni" is the number of threads per inch, again, in our case, this is 20.

Like I said, a bit more involved. (going to puke now)


Best to get a cheat sheet chart or a copy of machinery handbook.

Hope this helped.

C.

 

[skog]

Re: Does this muzzle look right?

1/2 inch is the major diameter by 28 threads per inch.

 

[scrtshtr2286]

Re: Does this muzzle look right?

Definitely helped. To make sure I got it, this means threading the barrel to a certain size is like choosing a socket for a bolt. 1/2x28 means a "half inch" or .495 is going to be remaining on the barrel right? So just like the picture posted, it should measure somewhere around .495 in diameter from one side of the thread to the other 180 deg out? Sorry for the ignorance but I am literally starting fresh here. Wonderful things happen when you fall 15 to 20' and land on your head. Short term memory is shot and problem solving....forget it.

 

[AXEMAN]

Re: Does this muzzle look right?

no. it doesnt.

 

[Keith Johns]

Re: Does this muzzle look right?

Chad, how do you have the time?
Must not sleep.