Explain "truing" a bolt

[S1gnal]

Ok I come to you all humble with a simple request...

Can someone please explain the process of " truing a bolt" in layman's terms

1.)What is done to make it true
2.) How does it change the bolt
3.) what performances are gained
4.) negative effects

It came up when I was talking to a co-worker about how "stiff" the action was on my Remington and I was asking if the prob would cure itself with more shooting (break in) or if I needed to be pro active about it. From there the conversation took several left turns, a right, a detour and a u-turn and we got into "truing"
He tried to explain what "truing" was but what seemed simple to him was a lot of shop talk to me....

 

[Qbeam]

Paging E.Shell.... Paging E.Shell...... Please take your party's call on the nearest posting please.

S1gnal, E.Shell is one of our resident long-range/precision shooting gurus. He speaks, we listen.

 

[S1gnal]

Oh trust me I know, I met him when he assisted me in mounting my scope and rings. (ok, more like he did all the work and I looked, listened, and tried to keep up)

But hey I totally nailed the part where I took the rifle out of the case.

 

[E.Shell]

1.)What is done to make it true

The several engagement surfaces of the bolt are re-cut to be square with the bolt body, which follows the bolt bore in the receiver.

2.) How does it change the bolt

A) The face of the bolt is lightly cut to provide perfectly square engagement with the head of the cartridge case.
B) The rear surface of the locking lugs are re-cut to provide square and even engagement to the lug recesses in the receiver.

3.) what performances are gained

By having a perfectly square bolt face, all pressure forces are in line with the action of the rifle and any tendency to flex in an inconsistent manner is reduced. By having perfectly even bolt lug engagement, we eliminate the flexing that occurs in the bolt body and the action due to putting too much pressure on one lug and not enough on the other. Flexing causes movement, movement causes inconsistent reaction. Inconsistent "anything" detracts from accuracy.

4.) negative effects

Because material is removed from two surfaces that affect headspace, headspace is then altered. This may or may not cause headspace to be excessive, since, without gauging, we don't know where it was to begin with, and since we don't know how much we'll have to remove from the bolt face and lugs to produce a square condition, we could end up anywhere. If your headspace was at SAAMI minimum, the bolt face mostly square and only a .001" cleanup cut was taken, and the lugs are mostly square and we only took a cleanup cut of .001" there too, headspace is only lengthened by .002" and you're still in spec. The single biggest problem with truing the bolt is that doing just the bolt is not really fully addressing any potential problems in the mating surfaces of the receiver.

It came up when I was talking to a co-worker about how "stiff" the action was on my Remington and I was asking if the prob would cure itself with more shooting (break in) or if I needed to be pro active about it. From there the conversation took several left turns, a right, a detour and a u-turn and we got into "truing"

Lets figure out what is making bolt operation tight. Is it tight to slide back and forth? Is it tight to turn into battery? Is it tighter with a round present? The bolt, and it's bore, may only need to be cleaned with lighter fluid or solvent to remove dried grease and/or fouling, and very lightly oiled. It may be that you're feeling normal friction from the mag follower pushing against the underside of the bolt, and this can be checked by opening the floorplate and cycling the bolt. It may be that you're feeling the action of the striker being cocked on the closing stroke, wherein the spring is compressed. The bolt lugs may be dry, and should be cleaned and then lightly greased with a high pressure grease. I find that the bolt lugs require grease at almost every cleaning.

He tried to explain what "truing" was but what seemed simple to him was a lot of shop talk to me....

Well, it really IS "shop talk" in the truest sense of the expression, but it can be discussed in it's various elements to keep it readily understandable to those who do not work in a shop.

The concept that something must be trued implies that something is not straight, square and/or uniform. In the case of a factory rifle action, it may be all of the above.

How can it get out of square and/or not be already true - it IS new, after all?

As is the case in many things in life, there is a compromise to be found. Here, it is between production costs and market acceptance. Mass production techniques that lend themselves to profitability and competitive sales prices do not render the absolute best product quality possible. In fairness to the manufacturers, we must also remember that the most demanding users form the smallest segment of the buying demographic, and most shooters/buyers can't or won't shoot the performance difference another couple hundred bucks in attention to detail will add to the rifle's cost.

To simplify the concepts of truing a rifle action and it's parts, simply think of it as a cylindrical assembly made up of multiple parts that must be in complete alignment and solid contact to resist deflection under pressure of firing and recoil.

Using your Remington as an example, the bolt is the main moving part, and follows a bored hole through the theoretical center of the receiver. The steel in both parts must be heat treated to provide optimum hardness and tensile strength. The parts must be very close to finished dimensions and shape to be ready for treatment, but process of heat treating slightly distorts both parts, which are ground afterward to restore them to shape.

If the bolt bends slightly during processing, the previously square-to-the-axis bolt face can no longer be square, and will not support the case head evenly. If we wouldn't mind another $50 tacked on to the raw cost of the rifle, we would re-cut the bolt face, but Savage is already selling their rifle cheaper, so what can we do to stay competitive? Skip it, the effect is small and we have bigger fish to fry. . .

The bolt lugs are ground to be square to the bolt body, and, while not always perfect, are often the most accurately cut surfaces we'll see.

The action is ground around it's outer circumference to be cylindrical, and depending on numerous factors affecting grinding precision, the axis of the action may no longer be parallel to the axis of the bolt bore. The process required to precision grind the outside of the action is much more involved (read that "expensive"), and we're already selling this model for as much as a Winchester, so what can we do to stay competitive? Skip it, the effect is small and we have bigger fish to fry. . .

The lug recesses are cut into the action and dimensionally referenced to the action body. Since we know now that the outer surfaces may not be perfectly parallel to the bolt bore, then too will the lug recesses be a little out. What do we do . . . Skip it, the effect is small . . .

The rifle receiver is made of a piece of round steel bar stock that is cut from a long section of bar stock. It is cut with a saw. Ideally, it would be cut with a lathe, but, this is yet another step that would add involvement (cost). The saw is set up to be square, but, remember we've done a few things that can affect this originally square cut. What do we do? Skip it, the effect is small.

We thread the front receiver ring to accept a barrel, and guess what? It's referenced to the action's outer surfaces and not necessarily square to the bolt bore either. What do we do . . . Skip it, the effect is small . . .

We install a recoil lug, cut from sheet stock, the most efficient way to make a small, "flat" part. This recoil lug fits between the front of the receiver and the barrel shoulder at the rear of the barrel (yet another sad story). Guess what? "Flat" sheet stock is not perfectly flat, plus, it's heat treated too, and prone to warp slightly. What do we do? Skip it. . .

So, now we assemble all these warped and ground and bent and very slightly mis-cut parts into a "precision" rifle, and we suddenly have "hunting accuracy" as these many small contributing factors stack up.

Fortunately, this level of accuracy satisfies 95% of the demographic, who will buy too much gun and be afraid of the recoil and slam their eyes shut when they shoot, feed it the cheapest available bulk hunting ammo, shoot from the most rickety position possible at moving game that is at an unknown distance, and if they can manage to land one in the milk-jug sized heart/lung/shoulder area, their rifle is a tac-driver. . .

But, what if we really DO need more accuracy? What then, how is this feat accomplished? Simple, we now put in the missing labor and costs required to make the important parts fit together in a straight line and be square with each other. This process is what is referred to as "truing the action".

Some of this work may be done as a factory upgrade. Using Remington as an example, their "hunting rifles" lack some refinement, and nothing is really deliberately trued. We might get a good one and shoot <1 MOA, or one that is not so good and shoot >2 MOA. Their "varmint rifles" are held to slightly higher standards, and either some truing steps taken, or a higher level of QC used to select those assembly components that display best qualities. We might reasonable expect 1 MOA from a factory varmint rifle. Their "tactical rifles" are held to even higher standards, and can be expected to deliver even better accuracy. Sales prices reflect this, and both the varmint rifle and tac rifle cost more than their hunting rifle counterparts that use the same materials and essentially the same stocks.

If we need more accuracy than is provided by these upgraded rifles, or, if we're converting a hunting rifle, we'll need to perform a series of steps to reduce the variations.

We'll pull the barrel and the first thing we'll do is either replace the recoil lug or grind it flat. This gives us a square barrel-to-receiver junction. Replacement precision-ground lugs are very popular, and another improvement to the recoil lug is to use a thicker replacement, to provide greater rigidity to resist deflection.

Then, the action will be set up in a lathe and made to spin true, referenced not to the re-ground exterior, but to the all-important bolt bore, our primary reference point. Once we have the bolt bore running true in the lathe, we cut the front of the action, replacing the OEM saw cut with a fine lathe cut. We'll re-cut the bolt lug recesses to be square with the bolt bore. Finally, we'll re-cut the receiver's barrel threads to also be axially aligned with the bolt bore.

We already talked about how we'll true the bolt, and since the bolt face and bolt lugs are both already re-cut to be square to the bolt body, they'll also be square to the action. This puts all recoil and pressure forces directly in line with each other, and there is no longer any accuracy-killing lateral deflection

We'll assemble the bolt and action together, and lightly lap the engagement surfaces of the lugs to provide optimum contact.

At this point, the bolt body is in line with all critical receiver surfaces, and all other receiver surfaces are either parallel with or square to all mating parts. Very little else can be done that will have as big an effect on accuracy as what we have already done.

We can sleeve the bolt to reduce clearance and play between it and the bore, to ensure that our axial alignment is closely held. We can drill out the slightly off-center firing pin hole in the bolt face, install a bushing, then redrill it in the right place. We can install a spring guide to reduce the effects of the striker spring rubbing the inner surface of the bolt. There are yet other things that we can do, but these nuances are lost on anything short of a full blown benchrest rifle capable of consistently delivering .1" groups at 100 yards.

For all the work to get the action to this point, it's a shame to re-install the original barrel, but even if we do, we should cut 1/2" off the rear end to set it back, and then recut the chamber and threads to be as axially aligned as possible.

Because of the involvement, action truing would normally be delayed until the barrel requires replacement or needs to be set back due to erosion/wear.

 

[Houndkeeper]

OMG. It's like a dissertation written by God. Good stuff but so over my head.

 

[Drmsparks]

Can we start an E.Shell archive/Library?

 

[trickg]

Wow. Ed, that was a fantastic bit of information but I do have one question about another term that is bandied about when talking about rifles and precision accuracy, and that is the term "blueprint". I've read many times about how you can send a rifle off to a company and they'll do some of the various accurizing things you mentioned above, and about how they will "blueprint the action". What exactly does that mean?

Man - your post above makes it so that I don't ever want anything less than a fully accurized rifle, even though it's doubtful that as a shooter I'd be able to tell the difference. Still, there's something to be said about knowing that any shooting deficiencies a person might have are theirs alone to bear, and that the rifle cannot be blamed due to having been set up to be as accurate as possible.

 

[E.Shell]

Wow. Ed, that was a fantastic bit of information but I do have one question about another term that is bandied about when talking about rifles and precision accuracy, and that is the term "blueprint". I've read many times about how you can send a rifle off to a company and they'll do some of the various accurizing things you mentioned above, and about how they will "blueprint the action". What exactly does that mean?

"Blueprinting" an action is the same thing, a bit of a misnomer, and actually a carryover from automotive terms. "Blueprints" (production drawings) contain the "ideal" dimensional information that "perfect" production methods would produce, and give acceptable deviations ("tolerances") that can be permitted and still provide a product that will perform as expected.

In theory, since we have slightly compromised perfection in the name of practicality, we're looking at running on both sides of the tolerance limits given by the blueprints. To true an action doesn't necessarily create a product more faithful to the original plans (hence the misnomer), but does create technically correctly cut engagement surfaces that will work together to provide minimum stress and maximum repeatability, which contributes to improved accuracy, even though both surfaces might now be out of tolerance.

Man - your post above makes it so that I don't ever want anything less than a fully accurized rifle, even though it's doubtful that as a shooter I'd be able to tell the difference. Still, there's something to be said about knowing that any shooting deficiencies a person might have are theirs alone to bear, and that the rifle cannot be blamed due to having been set up to be as accurate as possible.

It will all depend on the way the tolerances and errors stack up, and many rifles shoot extremely well right out of the box. 3/4 MOA is better than most shooters can hold from field positions and/or evaluate environmental conditions well enough to compensate for them.

I've seen quite a few Remington Tac rifles and Savages shoot to 3/4 MOA or less with no modifications other than to make sure all screws are tight and set the trigger at some reasonable value.

It is a learning curve, and game of limiting factors, first, the rifle is sufficient, and the shooter needs work. Then, the shooter begins to work against the accuracy limitations of the rifle. We improve the rifle, and again the shooter is becomes the bottle neck to progress. The shooter then learns yet more nuances to accurate shooting, and we're finally limited by equipment again, if not the rifle, the ammo. We go to a custom rifle and carefully handload our ammo, and at some point the shooter will again become the limiting factor, in that the shooter must learn more about environmental conditions to derive the accuracy potential of him/herself and the gear.

Because of this, I normally suggest that new long range or precision shooters get the best equipment they can, but not to become obsessed with trying to get too much performance from the gear until they themselves can effectively utilize it, and plan to upgrade at some point.

The most effective way to get into precision shooting is often to get a relatively accurate rig, learn to handload, then just burn that sucker up in practice. By the time the typical barrel is toasted, you've got a lot of rounds under your belt and a lot of tricks up your sleeve and you're likely ready to take full advantage of the enhanced accuracy available in a trued/custom rifle. In theory, it's tempting to just jump into a custom rifle, but, how efficient is that when we burn up a high dollar barrel learning to shoot?

One of my favorite rifles is a stock OEM Remington LTR in .308, which shoots about as well as I can from field positions. It will drive FGMM 168s into one hole at 100 and FGMM 175s into 3/4 MOA all day long and I use it to work on my position shooting (prone slung & sitting slung). I helped one of the members here set up a new rem 5R that shoots to 1/2 MOA. With that kind of accuracy available in factory guns, one really has to develop a good skill set to be limited by the gun itself and a full blown custom is not a necessity to get into precision shooting in any class short of benchrest.

 

[trickg]

Ed - thanks for that. I was wondering if it wasn't more or less the same thing, but simply refered to differently.

The average person might not be able to tell the difference, but the same can be said of any accurizing process that can be applied to many different things. I might have mentioned this before, but I'm a trumpet player, and a couple of years back I got a great deal on a Schilke trumpet, which is a finely crafted, hand-made instrument.

There is a company in Californa owned and operated by a man named Bob Reeves, and he does what's known as a precision valve alignment on the valves of a trumpet - essentially he takes the horn, scopes it, and uses pads and "felts" that are specifically sized and made of a very stable, long lasting material so that after installation when the valves are pressed or up, they are at their optimal placement for the best response from the horn. It's like you mentioned with blueprinting - it may be slightly outside of the spec of the blueprint, but ultimately it provides for better accuracy and performance.

Could I tell the difference when I got my horn back from being aligned. Yeah, I could, but I'm not sure that the average hobbyist weekend warrior player would have been able to. But for me the best part is that with the alignment, I now know that any issues I have as a player are mine alone because I have a hand-made, precision instrument that has been fine tuned to offer optimal performance.

As a side note, what does it generally cost to have a rifle accurized according to what you posted above, and what companies would you recommend for that service?

 

[E.Shell]

Ed - thanks for that.

As a side note, what does it generally cost to have a rifle accurized according to what you posted above, and what companies would you recommend for that service?

Almost any good quality custom rifle maker will true an action as a necessary part of accurizing a rifle or building a custom gun based on a production action.

Jared Joplin, of Patriot Arms, is a great 'smith who both fully understands the requirements of an accurate rifle and innovates. George Gardner of GA Precision is another very good guy that routinely turns out exemplary work and experiments to find improvements. Terry Cross of KMW and Randy at R&D Precision are a few more that come to mind.

George at GAP has done my last few customs, and I plan to have Jared do my next one, not due to being unhappy with George, but because Jared is a friend and I want one of his guns. I tend to go to George and Jared also because they support the shooting sports and both are regular contributors to the prize tables at several of the matches.

There are many precision 'smiths that do benchrest quality work, but the rifles they turn out are a little too "tight" for the average shooter and are a PIA to shoot in the field or a lot. Sid Goodling in Spring Grove, PA built a VERY nice 1,000 benchrest gun for me in the mid-90s that shoots 1/4 MOA, but it requires neck turned brass and cleaning at very frequent intervals. It's great for what it is, but these days I don't have the time or patience to fool with all the case prep and rifle maintenance required to run a rifle like that to it's full potential and I seldom shoot it.

ETA: Forgot to say that the cost of truing and action will vary from 'smith to 'smith, but most get between $175 & 250, and it's usually a substantial part of the total labor cost to fit a custom barrel. To pull a factory barrel, true the action and reinstall that same barrel will likely put you on the upper end of that range. One typically does not have an action or bolt "checked", since the same machinery setups required to check a part are required to make the cut. Setup is always the most labor intensive part, and by the time we make a tedious precision setup on a machine tool necessary to check a parameter, the actual cut is rather anticlimactic.

 

[B1web]

Can we start an E.Shell archive/Library?

+1

Thank you Mr. Shell.....!!!

 

[S1gnal]

The most effective way to get into precision shooting is often to get a relatively accurate rig, learn to handload, then just burn that sucker up in practice. By the time the typical barrel is toasted, you've got a lot of rounds under your belt and a lot of tricks up your sleeve and you're likely ready to take full advantage of the enhanced accuracy available in a trued/custom rifle. In theory, it's tempting to just jump into a custom rifle, but, how efficient is that when we burn up a high dollar barrel learning to shoot?

This would be me minus the handloading part
I jut came back from Hap Baker yesterday trying out some Hornady 165 Custom. It shot well but not as well as that Remington 165 Nosler tip I had. I think in the last two trips Ive shot 60 rounds already.

Thanks for the reply Ed. I actually have read it a couple of times since you posted it. Believe it or not, I understand it all..lol
When I mentioned the bolt was stiff it was in reference to turning it, to eject a casing. I always remembered when I first began looking at the rifle at how smooth and free the Tikka Bolts were so Ive been using that as a measuring stick.
During yesterday session it seemed like it improved a little.

I'm surprised this isn't a sticky o in the FAQ or something

 

[E.Shell]

Believe it or not, I understand it all..lol

When I mentioned the bolt was stiff it was in reference to turning it, to eject a casing.

The fired brass of some ammo will be easier to extract than others, and this is part what you feel when you turn the bolt to open it: "primary extraction".

As good as your chamber looked when we bore scoped it, I'd suspect that this resistance you feel is normal. Also, don't compare extracting a fired cartridge case to opening the bolt on an empty chamber.