Odd groupings...whats happening?

Like I said, hand built, using cherry picked parts,
Hand fitted, gaged, even knurled for tight interference fit,
And that's starting with a 'Star' stamped barrel to begin with.

And you report no function or accuracy problems!

Now, to the discussion at hand,
Which is a barrel of unknown origin, unknown material, unknown rifling twist rate, never been gauged by the user/builder,
Unknown harmonics,
Unknown cyclic vibration patterns,
Unknown muzzle crown preparation,
Unknown muzzle attachments,
Ect. Ect. Ect.

And yet you are ready to throw down a blanket statement with all those unknowns...
I'm uncomfortable with that.
I would do a little non destructive experimentation to help pin point exactly what the issue is before I made any absolute proclamations about what it is or isn't.

Low carbon ordnance steel, high nickel steel, stainless steel,
With or without a muzzle attachment, is the muzzle attachment centered or off center,
What condition is the crown, rounded or face cut, how clean is the muzzle breaks from rifling, ect.

I haven't shot competition in 20 years,
I have had to deal with the last 20 years of firearms stupidity on the civilian market, and there simply are no 'Standards', you work with what shows up at your door.
Everybody makes something, its all different quality, machining standards, ect. so blanket statements simply do not apply.

Military life was MUCH more simple, you had an expectation of reasonable quality, standards.
Not so out here in the world, it doesn't have to have a function, just be an accessory, and it doesn't even have to be safe to sell a million units...

Its like the bench shooter on the bench next to me last week, bragging he had $5,000 to $15,000 each in his rifles.
I sat down with an AR and he s-CENSORED--CENSORED--CENSORED--CENSORED--CENSORED--CENSORED-ed, then I shot one ragged hole groups at 200 yards, he kept telling me it couldn't be done with a military top and barrel,
He watched my targets to see if I was shooting them or palming a ringer target,
Just ranted and raved it simply couldn't be done...

The very reason I recondition and tune up military barrels is because they have good ordnance steel to begin with.
Close up freebore, cut a decent chamber in them, cut a good crown and have fun for cheap!

The uppers are the same way, 90% of military assembled uppers that get rejected are from the anodizing screwing up tolerances,
Clean that up, you get a high quality, hammer forged, rigid upper for cheap that shoots very good, that makes it cheap & fun.

-----

And you are correct, the BARREL doesn't change its harmonics/oscillation once final manufactured.

Everything else effects the harmonic patterns,
Anything attached to the muzzle,
Anything attached to the barrel anywhere,
Any different friction bullet will cause a different harmonic pattern,
Physics is pretty boring until something starts to move, then it gets exciting quick!
 
All I can say is, if you're uncomfortable with my blanket statement, then one of us is better informed and knows more than the other.
 
Wow guys. Guess my idea of simple answers waved bye bye. Wasnt tryin to start a d@*% measurin contest.

Some info on the gun. There are no crown chips or anything like that. My muzzle break is a JP bennie cooley, normal size. Barrel is a 20" heavy profile stainless non crome lined Fulton Armory Match. 1-10 twist. Aero upper/lower. Geissele SSA-E trigger. Aero NiBo bcg. Magpul PRS stock. Vortex 4-16x44
 
Taco-- You got some good answers and a little bit more detail then you were looking for:D.
Try different primers and powder. Only switch one component at a time.
 
I think I'd start simple and easy,
Try the same loads, see if the same effect happens.
Then switch powders,
OR,
Unscrew that break, use a thread protection nut and try again.
That will tell you if its harmonics cycling or ammo right away if it repeats.

The KISS approach, costs nothing and easy to do.
 
Bart,
If its a question of who knows more...
And I'm not saying I do, but I do know this,

My first job in the custom shop was air gauging barrels back in '79.
The first thing my instructor said to me was, "This ain't the Navy kid, you are going to do this right."

Since your 'Chief' didn't give you any tolerances from the air gauging,
The imperfections were either averaged, and stated as a single number,
Or the air gauging wasn't done correctly.

The entire point of air gauging is to find tight or loose spots,
And a proper air gauging will be expressed in Minimum & Maximum tolerances judged by the amount of air that escapes between test gauge head and bore.

When the bore fell into a certain tolerance range, since none of the single pass button rifling was ever perfect, and I'll get into that in a minute,
It was the tolerance range that was approved for the 'Star' stamp,
The preferred barrel proof mark the US military has used since Hiram Berdan's "Sharps Shooters" started using it during the Civil War.
That includes WWI 03 Springfields, the WWII Garands, M14/M1A/M21 rifles.

Now, bragging about "Single Pass Button Rifling" is like bragging about the belt sander you have.
It's a manufacturing process that German gunsmiths invented when rifling became common in the mid 1700s.
It simply means someone stuck a long rod down the barrel,
Connected it to a pulling/twisting jig of some sort,
And dragged a metal chisel down that piece of tubing.

The master gun smiths (which I'll get to those comments also) called it "One Gouge" rifling,
Mostly since the torque on the LONG rod loaded & unloaded unpredictably leaving hesitation & gouge marks in the rifling,
Not the long, controlled spiral twist they were hoping to get.

That circles back around to two points,
One would be the hand lapping or with modern machines, machine lapping to correct the gouges, and inconsistant cutting action of the broching head cutting the rifling since with torque loading and unloading on the rod/shaft, the rifling didn't run true.
So someone had to get in there and lap those defects out,
The entire point of lapping a barrel.

The second is there are MUCH MORE ACCURATE ways to cut closer tolerance, more consistent rifling than a 300 year old method still used by high volume producers.
It ranks right up there with hammer forging that misses places on the barrel stock, rather than roll forging that gets every part of the barrel void pressed and the grain compacted...

Now,
Your snide remarks about "Parts Breakers" and "Marketing" when referring to a master gun smith...
When a guy works all his life making guns,
Can conceive of, design, prototype, and build every single finely crafted firearm you have ever seen or read about, that is a master gun smith.

He can turn blank pieces of untreated steel into springs, receivers you need a magnifying glass to see the parts seperation lines,
Can heat treat that steel,
Assemble the parts that will last a century or more,
And still function well and shoot well (Barring abuse from idiots),
That's a master gun smith.

Since every fine firearm ever made had to have a master gun smith involved at some point, if nothing more than final fit and finish,
Since kitchen table hacks can't do it...

Now, for the remarks about my AR10s,
The AR 10 wasn't in common US military use when I retired,
I'm learning...
And since I started with an AR10 that came to me as it was, its not cherry picked parts, built or shot by the best marksmen in the world.

If you have an issue with my fitting or building of rifles,
Or my marksmenship abilities, that's just plain tough.
It's your problem, not mine...

If you insist in being obtuse just so you don't have to learn anything new,
Again, that's your choice.

Since Uncle Nick has verified what I've written about the manufacturing processes (Before this post, he can comment on this post also if he cares to)
That should tell you who knows what about that end of things.

Since nothing I've posted about squaring/truing receivers, correcting off center chambers or bores is anything new in the gun smith world,
That's pretty easy to verify.

Harmonics/cycling vibration is also pretty easy to verify,
There are a ton of high speed videos on the net, mostly showing off what high speed cameras can capture, but interesting none the less,
And proving the point at the same time.

Bart, you are arguing machining with a machinist,
You are arguing harmonic vibration cycling with a guy that deals with compression, rebound, cycling, vibration patterns, friction oscellations, dynamic drag, ect.
In metals,
That works in that very field everyday.

You are arguing gun smithing with a former military small arms specialist.

I didn't like competition shooting when I did it in the military,
So as soon as I retired, I stopped competition, and went back to working on and shooting for fun.

My knowledge base, experence & abilities are technical, metallurgy, machining, chemical, electrical,
My experence spans over 40 years,
I would be the last one to declare I was the last word in anything, since someone, somewhere is going to know more than me on any given subject...
Keeping that in mind, I'm always willing to learn, not closed off to new ideas, processes, materials.

NOT sitting on my laurels, I'm looking for the next bit of information to connect the dots on something I'm doing, have done, and could do better...
Lording over an Internet forum isn't something I'm interested in,
Figuring out what does work, why it works, and to what degree is something I'm interested in,

So Bart,
If you don't mind, I'd like to converse with Taco and find out what he finds...
Without anymore snide, back handed comments, arguments that are clearly out of your depth and knowledge base.
 
It'll be a week or so before i get time to shoot anymore, but i will post my findings, maybe with pics. Going to try the best 3 loads again, but probably more rounds for each. I also may go up another .5-1 grain, as I did not approach published max load data, per Lyman's 49th. I may alternate the shots (one shot each load, then start again). Im thinking this may take out some more variables. I also plan to work up some IMR 4064 in the same fashion as my original test.
 
Taco, I think you are on the right track.
You have a very good start, with one of those head scratchers thrown in just to make it interesting!
What fun would it be if everything worked out perfectly...

I would like for everything work out perfectly just once in my life!!!
Everything I do I have to tune... Even if I get the results I expected I screw with it until I mess it up...
 
Not cheap...
I just updated to a bullet puller that doesn't damage the bullets since I had years of 'Scrubs' around here, and there isn't any 'Cheap' bullets anymore.

They probably won't be high accuracy round, but 5 or 10 pounds of bullets will make for some fun shooting!
I'm going to give some clays any ground hogs a real hard time...
 
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