Another 50Millionths Man?

I'll never say never to .25 minute factory ammo, but a one-inch piece of steel will grow or shrink 50 millionths if you open a window in the shop. When someone suggests they are holding tolerances that are physically impossible, it calls into account their understanding of the mechanics involved. That doesn't mean their rifles are crap, but it may mean they're more expensive than they need to be.
 
A fellow I shot with in Seattle several years back who is a top notch machinist from all reports I've ever heard or seen, commented one day that when he worked at Boeing pieces that HAD to be accurate to 0.0001" were measured in a climate controlled room with calibrated equipment. I never had reason to question the accuracy of his statement, but would be willing to bet that climate controlled rooms and calibrated measuring equipment might be a little scarce outside of the aerospace industry or other manufacturing processes that require such accuracy.
 
Butch Lambert said:
Al,
I believe he is guaranteeing 1/8MOA now.
Butch
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kinda read thru about half the posts here, and found the whole thing interesting, but I'm inline with with most all of you. Is it possible to ream a hole per Mr. Spencer's specs? You can rest assured with a good piece of equipment you can. Will it make it shoot 1/8" groups all day long? I doubt it! With machinery built thirty five years ago we thought we were at the top of the heap holding six or eight tenths. By the mid 1980's we had equipment that would do four or five tenths all day long, and machine centers that were doing stuff well under three tenths (Devlieg jig mills for one). But you say "nay not so with a lathe!" A properly aligned Hardingh CNC lathe will do .0003", and with a custom ground Mapol reamer it ought to be well under .00025" compound error on an everyday basis. But then can you hold a 12" bar of steel to .0001" in a foot? I really doubt it unless it's three inches in diameter or larger due to flex alone. But it can be ground to a tenth. I've seen CNC lathes cut shafts a little over forty inches long, and hold them strait to
.00035" (properly tooled). Most of it depends on the bearing packs and condition of the ways. Yet with todays programing you can actually take 95% of all the machined taper out of the part without too much trouble. Still the average lathe somebody like us would be using will not come close to these specs, but never think it can't be done
gary
 
Larry Elliott said:
A fellow I shot with in Seattle several years back who is a top notch machinist from all reports I've ever heard or seen, commented one day that when he worked at Boeing pieces that HAD to be accurate to 0.0001" were measured in a climate controlled room with calibrated equipment. I never had reason to question the accuracy of his statement, but would be willing to bet that climate controlled rooms and calibrated measuring equipment might be a little scarce outside of the aerospace industry or other manufacturing processes that require such accuracy.
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actually fairly common these days. I well remember an irregular profiled curve being ground on a piston cup in a hydrostatic drive that had to be held to .000025" on a Cinn plunge grinder. I've seen paper rolls being ground to .00025" in 12 feet, and I've had ways ground to .00025" in 12 feet as a regular thing.
gary
 
I think that as with many things there is a point of diminishing returns. Could we even see the difference in accuracy between chambers that are aligned to .0002 as compared to .0005?
 
I was thinking of mentioning that too, but didn't want to stick my neck out any farther....
 
IIRC, Michael Turner once made this claim, and was hooo-rahed. Except look at how his rifles have done in the crucible of competition. Far as I'm concerned, when M Turner speaks, I listen. I'll reserve judgment on the 50 millionths, but I'll always listen to him.
 
I for one don't care what the numbers are as long as it shoots, and can you shoot as good as the rifle will perform. To much human error as I found out this weekend.

Joe Salt
 
I haven't seen a bore straight enough to warrant that kind of effort. I guess I can understand doing the best you can. There is something to be said for taking pride in your work, doesn't seem to be out there much these days. The guy seems to me to be selling fluff but the bottom line is if it shoots then........
Jim
 
Boyd Allen said:
I think that as with many things there is a point of diminishing returns. Could we even see the difference in accuracy between chambers that are aligned to .0002 as compared to .0005?
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I doubt it! I doubt you'd see much with .00075" TIR
gary
 
Nader said:
Has anyone ever tried to cut a crooked, non-concentric chamber and see how far out of alignment with the bore it could be before it effected accuracy ?. . .
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I've done that many times - usually not on purpose. I couldn't tell the difference. I won just as many fake-wood trophies (not many), and shot just as many 4 and 1 groups (a lot). ;) ;)

ray
 
What makes me chuckle is that after all this fancy measuring and everything, they grab a reamer and jam it in the hole. If these were CNC internally ground chambers, I'd feel better about buying this stuff. I'm not opposed to someone saying they are capable of checking things to within very close tolerance. Making things that close is generally another story. Doing both, in a machine not intended for either, is a real stretch.

Today I was trying to make a part that needed a hole very concentric (non gun related). The hole was supposed to be for on a 6mm shaft, and needed to be real close. I have a brand new 6mm reamer here. A straight one. I made the part, and reamed the hole, low and behold the hole was over by .0018. ??? wth? Yes, I swept the morse taper before beginning, and the reamer was as aligned as I can make it. The hole was prebored 1.2" deep. The reamer simply is bigger than the numbers etched on it. My box of 6mm dowel pins are .0002 over and won't fit inside a bearing diameter without modification.

On the reamer, you can measure .2374 across any two flutes (6fl reamer) and who's to say how out of round they are. Clearly etched on it is .2362. Well, I guess it's .2362 +/- .0015 Lmao!

And this is on a straight reamer, not one that has all sorts of tapers and shapes. Good thing they are 5 flutes eh! People'd be measurin the hell outa them.
 
Boyd Allen said:
Al,
I'll pay your entry fee for one day, and try to help to make arrangements for you to do that at a match in Tacoma. I would think that it would be very good for business. I didn't say that I knew that it couldn't be done, just that absent published match results, I am extremely doubtful. Oh, and I wasn't talking about just any caliber. I believe that the claim was made for a .308. Added later: Make that a tactical rifle, in .308.
Boyd
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And exactly what good is a quarter minute rifle "at Tacoma?" (I'm _assuming_ you mean that I "should take one to a BR match"??)

Why?

Are you trying to make a point somehow, what with all the "I'll even pay your way" stuff? What would be accomplished by wasting range time with a quarter minute rifle at a BR match? "Proving" 1/4moa accuracy?

And BTW I still have several cases of 308 Match (yes, that'll shoot in a 308 Winchester)..... I used to buy cases of the stuff, Match Fed/Win/Rem and until one of you guys steps and tells me HE'S TRIED IT I can't give any credence to people thinking that factory loaded Match ammo can't shoot. Build a gun around Match ammunition and it'll shoot "quarter minute all day."

As far as building quarter minute rifles in a variety of calibers, Dan Kinneman's been advertising it for 20yrs. Kenny Jarrett, Darrell Holland, Dan Dowling, Speedy....... I could go on with folks who'd be happy to put a 1/4moa spec on a steenking varmint rifle.

And constantly throwing in garbage about "but matches are won with quarter inch groups" and "yeahh but a PPC won't shoot 1/4" groups where I shoot" is completely irrelevant. Unless someone steps up to say "I built a bunch of rifles and fired them in good testing conditions and couldn't get 1/4 inch groups" they're just speculating......... And If anyone REALLY wants to know I'll bet them plane fare, come on out and shoot 100yds on my range with my 308's, me calling the wind, and if YOU can't shoot 1/4" groups with one of those stupid tacticool 308's then I pay your fare..... well OK, if you suck enough I might have to pull the trigger while you watch BUT, you will definitely see "quarter inch 5-shot groups" fired from a "stupid tacticool rifle." I'll shoot 1/4" groups from a friggin bipod fer cryin' out loud. You WILL be buying your own plane ticket.

Getting 1/4moa accuracy from a custom rifle using short/fat bullets is dead easy.

Now getting 1/4moa from long/skinny bullets is hard, but that's a whole nuther ballawax.

but that was never the question was it? :p

al


:D:D I just hadda' adda edit......

Come on over here to the NorthLeft Coast, up near where Boyd's wanting me to "shooot a 308 in competition" and I could introduce you to a group of Good Ol' Boys who'll show you full-on 308's shooting 1/4 minute aggs WITH 6X SCOPES! And little skinny forends....Ohhh yes, and it's a form of competition too.... altho some will argue it's "too easy."

And then there's Michael Cavanaugh........


308's ROCK! Bruce D'Artus useta' shoot 1/4moa at a friggin' MILE with a 308....
 
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Here's what bothers me

Those people that bend spoons with their minds. Not the act of bending the spoon but rather I worry that it's somebody else bending the spoon playin' a trick on the guy that thinks he's doing the bending. The guy gets up a crowd to show off and the spoon just sits there. Think about it....why else would the guy gather folks to witness if he didn't think he could bend a dadburn spoon.

I tried and could only bend one 50 millionths no matter how hard I concentrated. When I let up, it sprung back to its old self.....so I thought. Some time later my wife was eating a "Snack Pack" and said..."this spoon is bent...but not enough to notice"
 
I think its important to get the chamber aligned and indicated to the best of our abilities, however, there are so many other variables.....I agree 50 millioniths thing is over-rated and not practical. Here is a neat one involving making a fire-form barrel. I have taken what I thought was a shot out barrel, chucked it in the lathe, re-thread, cone and chamber without ever looking at in indicator. The Bore scope reveals the expected outcome - chamber pushed to one side. Guess what - it shoots......about the best barrel I have and its 19 3/4 inches long! I might not admit it but don't be supprised if it on my gun at the Super-Shoot.

Nader.....Wyatt says your going down at the Hog Roast!
 
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