Why does action trueness matter?

B

Bnhpr

Ben Hooper
Everyone talks about blueprinting, squaring the action etc. I just do not understand why it matters to the bullet, which is 3 inches in front of the action.

How does it degrade accuracy?

It seems to me that if your lands/grooves/chamber are concentric and your headspace is minimized, your barrel is floated, you have covered your bases.

Is it a frequency thing? It seems black magic to me.

Thanks

Ben
 
The bolt holds the chambered round, which the action needs to be true to support the bolt and round in perfect alignment with your perfect chamber and barrel. Just a simply answer, you prob will get the detailed version soon,lol
 
Bnhpr said:
Everyone talks about blueprinting, squaring the action etc. I just do not understand why it matters to the bullet, which is 3 inches in front of the action.

How does it degrade accuracy?

It seems to me that if your lands/grooves/chamber are concentric and your headspace is minimized, your barrel is floated, you have covered your bases.

Is it a frequency thing? It seems black magic to me.

Thanks

Ben
Click to expand...

Probably a consistency, vibration, voodoo thing. See Vaughns, "Rifle
Accuracy Facts" for more detailed speculation...............Don
 
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tinman said:
The bolt holds the chambered round, which the action needs to be true to support the bolt and round in perfect alignment with your perfect chamber and barrel. Just a simply answer, you prob will get the detailed version soon,lol
Click to expand...

Let me rephrase the question:

Has anyone ever just re-worked the action on a lousy shooting rifle, and made it shoot well?

I know you can just re-work the barrel and make a rifle shoot well. Well defined as shoot under 1/2"
 
Imagine that your barrel is at a slight angle to the centerline the action. How can the bolt face be square to the chamber? How can a fired case's head be square? What happens when unsquare cases are reinserted in the chamber with random orientation? What causes the barrel to vibrate differently from shot to shot? If vibrations are not the same, what is the chance that the muzzle will be pointed in the same direction for each shot? If the face of the action is not square with the threads, will the the threads and shoulder of the barrel be under an even load when the barrel is tightened? That will the result of that unevenness be? And finally, what is the rifle to be used for, what level of accuracy satisfactory?

Your question indicates a healthy curiosity. I hope that my questions have not discouraged you in your pursuit of understanding of the theory of accuracy. Might I suggest Harold Vaughn's book Rifle Accuracy Facts. You may find some of the answers that you are looking for on its pages.
 
No, but

I've reworked / rechambered several [decent shooters to begin with, btw] that shot about the same after all the work... Kind of leads me to think that barrel quality, combined with a good chamber of course, would at least be the foremost accuracy factor.... I've rebedded and/or recrowned several that have improved however. Not that I'm a "guru" on the subject by any means, but that's been my limited experience.
 
Bnhpr

Without stepping on too many toes, or commiting Heresy, I would venture to say that, on the vast majority of Rifles, how true an action is means little as far as the everyday function of the Rifle is concerned.
But, on a Benchrest Rifle, where we go to every extreme amaginable to remove every variable from the accuracy equation, it, (probably) makes a big difference.
I will admitt that there are many things that seem overboard to the Lay Person when it comes to extremes of Benchrest. But, as I said in another post, when you are staring over a set of flags with a Rail Gun, and you are trying to put 10 shots in a sub .150 group, everything that can be done, is done. You cover all of the bases, because the agging capability of a given combination is only as good as it's weakest link.........jackie
 
Yes!! I Think

Bnhpr said:
Let me rephrase the question:

Has anyone ever just re-worked the action on a lousy shooting rifle, and made it shoot well?

I know you can just re-work the barrel and make a rifle shoot well. Well defined as shoot under 1/2"
Click to expand...

Here's my example--I had a Remington 40XB single shot made about 1970 that had 2 different barrels on it including the original factory barrel. It was accurate but not a tack driver. I sent it off to a top benchrest gunsmith who gave it the full Monty--about everything you can do to ensure it is "true." This included shimming the bolt for minimal clearance.

I put a new barrel on it so I guess your question is not exactly answerable, but now I have a real tackdriver.

In my opinion, if you have a standard factory action that is quite a bit "unsquare" in several areas, you will be hard pressed to get sub 1/2 MOA performance no matter how good the barrel.
 
All's I can say to that Jackie is that you must have gotten nice square easy-to-tune actions in your time :):):) There ain't NUTTIN' more provocative than a crooked action or rifle. And NO! a crooked action will not shoot well. Alla' this "reworking" and "trueing" etc of factory actions is NOT done just to satisfy someone's anal sense of security.............it's done to WIN. A straight rifle is a joy and a pleasure, a crookedy one is worse than a lamed horse on a rocky downhill grade, and you wit' a bad back.


And just "straightening" or trueing a factory rifle isn't normally enough to make it agg, it must also be tightened up.


And proper brass must be made for it.



This only applies to guns which actually shoot under 1/4"...............to those who only expect 1/2 moa or so, you'se can just ignore action trueness as you'll never find it in the noise. Just throw a "custom" barrel on and be happy. But it bugs me when "gunsmith's" come on this board and talk about how screwing such-and-such barrel on a factory action will make it "drive tacks". These same guys get into endless discussions about how their fireforming loads shoot just as good as their "fully prep'd" loads so their gun must be "really good". The same folks don't tune, don't use flags, throw "called" shots out of their agg's, and gener'ly use all sorts of mathematical and statistical analyses to "prove" how well their rifle's shoot instead of just poking bullets into one hole.


An accurate system absolutely requires a straight assembly, or an assembly which "relaxes" the same every time which is another way of saying a consistent firing system.



I doubt Jackie's ever had a bad rifle :)



LOL



al
 
Crow99 said:
I've reworked / rechambered several [decent shooters to begin with, btw] that shot about the same after all the work... Kind of leads me to think that barrel quality, combined with a good chamber of course, would at least be the foremost accuracy factor.... I've rebedded and/or recrowned several that have improved however. Not that I'm a "guru" on the subject by any means, but that's been my limited experience.
Click to expand...

Rebedding is a different story, I'm a believer. I learned that a long time ago that action stresses in the stock moves your point of impact.

As far as the case deforming from bolt face angles, I'll have to get my test indicator out on a before and after fired casing. You have my curiosity there.

I have some experience with vibration analysis, and I know frequency is a factor from reloading and shooting, but I will have to do my own experiments before I'm a true believer with the frequency theory.

I'm trying to plug the lowest holes in the accuracy bucket. This is what I believe to be true so far in priority list?

Barrel/Chamber precision and quality.
Headspacing
Bedding/stock fit
Trigger quality
Action alignment

Sound right?
 
"True" isn't quite the same as "straight." The late George Fulmer, some years back, wrote in Precision Shooting about some highpowder customers who wanted to keep using their existing barrels, which meant the action threads couldn't be enlarged. So, he set up on the thread in the action. Everything was trued to it, though it was off-center to the bolt raceway. But the receiver ring was trued to the thread, as were the lugs, boltface, and barrel shoulder. Fulmer as so sure this was wrong he stamped "Experimental" on the barrel. But the rifles shot very well indeed.

Of course, it is more work to do this -- easier to just set up on the bolt raceway & true everything -- including the action thread -- to that.

As to why it matters, I 'm not sure either, but following Vaughn, my thinking is that variations in bolt thrust account for variations in vibration, and while you cannot eliminate all variation in bolt thrust, you can minimize it when everything (esp the lugs) are bearing the same with each shot. This is aided a great deal if things are both true & without slop.
 
Of course, it is more work to do this -- easier to just set up on the bolt raceway & true everything -- including the action thread -- to that.



Do you use an expanding mandrel through the action or build your own mandrel?
 
It is hard to know what to attribute improvement to when making more than one change at a time, but generally one of the problems that the average shooter faces when making one of these how far to go decisions is that they have no way to know how bad things are in the first place. If you are lucky, and the action that you start with was made on a day when the stars were in the proper alignment, you may get away with doing less than the full treatment. The problem is how do you know how bad your action is in the first place?

I have an old 722 action that has had everything short of the threads being recut done to it. It lives behind a good old Hart barrel that was reamed with a tight necked .222 reamer. Some time after the rifle was put together the bolt was sleeved. It seems to me that it shot better. After that, it was glued into a prototype EDGE stock. It seemed to shoot still better. All of the shooting was done over flags, with loads tuned at the range, with a 2oz. trigger and a 36X B&L scope, with a good rest and bags.

Recently I loaned it to a friend so that he could try the whole Benchrest thing before investing a chunk.The guy is a better than average trigger puller, and a quick study. All but one of the times that he took that rifle to the range it produced sub .2" groups, and the time that it didn't there were some major distractions. I guess that my point is that I don't think that the threads in that old action were very far out. The pin strikes are centered in the primer, and my cases remain square. I got lucky, but everything else was redone, including replacing the stock recoil lug. These days, given the cost of all of that work, I would sell the rifle and start with an action that is straight and tight as is...like my Viper.
 
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Bnhpr said:
I'm trying to plug the lowest holes in the accuracy bucket. This is what I believe to be true so far in priority list?

Barrel/Chamber precision and quality.
Headspacing
Bedding/stock fit
Trigger quality
Action alignment

Sound right?
Click to expand...

I would change "Headspacing" to "brass fit to chamber and squareness of brass after resizing".
Does "Action alignment" refer to receiver being straight in the stock for tracking? That is important.
 
Al

If you go back and read the first sentence in my post, you will see that I said "the vast majority", and "everyday function". There are literally millions of Rifles on the planet for which the everyday function is being able to hit something as large as the kill area of a White Tail Deer at 100 yards. True actions arenot a big concern here.
The rest of us, which really makes up a small part of the shooting world, is more interested in ringing what ever last little bit of accuracy we can out of a specific combination, whether it be a full custom live varmint rig in "super dooper Ackley Improved", a full custom 6BR for producing 'wallet fillers", or a 6PPC Benchrest Rifle.
I should have included the accuracy minded custom builders in my post.
My apologies........jackie
 
Stephen Perry said:
Don't understand where are coming from. You talk the talk of a smith but seem nieve on basic gunsmithing. These are all good guys answering your questions but you are puzzling when you make statements that shooting a factory action without accurizing will give 1/2" accuracy. Come on fess up who are you? Your not looking for knowledge your playing a game.

Stephen Perry
Angelesr BR
Click to expand...

Is your question directed to me?
 
Stephen Perry said:
Don't understand where are coming from. You talk the talk of a smith but seem nieve on basic gunsmithing. These are all good guys answering your questions but you are puzzling when you make statements that shooting a factory action without accurizing will give 1/2" accuracy. Come on fess up who are you? Your not looking for knowledge your playing a game.

Stephen Perry
Angelesr BR
Click to expand...

That's a little obtuse Stephen, I didn't deserve that. And let me be clear, that I am not a gunsmith, nor pretend to be one.

I am, However, a machinist/Chief Engineer, with 20 years experience in a manual shop, as well as 3 years teaching experience of machine tool operations, and 13 years of training of Marine Engineers. I've been involved with maching operations in the oil and gas industry, which you cannot imagine, or begin to comprehend.

And by the way, I do have a factory rifle that shoots a 1/2" group. It's a Remington XR-100.
 
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