In the interest of reading fewer posts by people who don’t know what they’re talking about, I’m going to lay down the law on one of the most misunderstood concepts in the precision rifle world.
Specifically, tolerances and clearances.
99% of the time, when someone who isn’t an engineer (so, me, @308pirate, and a few other people) says “tolerances” on this website - for example, complaining about loose tolerances - they are actually talking about “clearances”. They also have no idea what they’re talking about because loose clearances are not inherently a bad thing. Too-tight clearances are inherently a bad thing, so if you have to pick a direction to err...
Nominal clearance is how much gap there is supposed to be between two components. If the bolt rattles around like it’s dancing the Macarena, the actual clearances are loose. If a gnat’s testicle can cause the action to lock up, the actual clearances are tight. Clearances allow you to coat your actions with insert-coating-here, operate in dusty/muddy/icy environments, and can make it slightly easier to bind the action if you’re running the bolt weird. Clearance is critical to proper function, and the range of possible clearances for a product is something that is very much engineered for a specific purpose.
Tolerances are how much the size of something varies from part to part. Tight tolerances have less variation, loose tolerances have more variation. If every individual piece is hand fit, tolerances don’t matter because you start with an interference and remove material as needed. If you’re in a mass production environment, you need to make sure an arbitrary bolt can work with an arbitrary action - and if the combination of nominal clearance and achievable tolerance can result in an interference, you get to deal with horrifically expensive rework, possibly of an entire production run.
The problem is, cutting tolerances in half increases manufacturing cost by an order of magnitude. As such, when Remington or someone is making a bunch of cheap rifles, they increase clearances by an astronomical amount to make sure the ancient machines and tools that they never budgeted to maintain, and therefore are incapable of holding reasonable tolerances, deliver parts that can technically fit together. And hey, for someone who thinks minute of deer at 50 yards is all anyone needs, and who thinks cherry-picked 3-shot groups are enough to prove accuracy, that works just fine. That describes pretty much everyone who bought Remington rifles in the last couple decades, and the manufacturing is cheap, so the profit potential is phenomenal, and so only a conglomerate of assholes intentionally trying to suck out every penny of value into their own pockets could drive company into bankruptcy.
On the opposite end of the spectrum, you have companies like Defiance, with tight tolerances that allow them to have really tight clearances that are legendary for locking up in dusty environments - unless you tell them you’re going to be operating in dust, or cerakoting, or whatnot, and they are perfectly happy to loosen clearances up for you while keeping tight tolerances. They know essentially exactly how much clearance they’re going to have between the bolt and the action body, and know what the clearances need to be for pretty much every use case to feel perfect, but since the default buyer tends to only care about how tight the bolt is in the action body that’s what they default to.
Then you get to some of the other cases who hold very tight tolerances, so they can have variable clearances for different parts of the bolt cycle. Borden and ARC actions both have looser clearances when the bolt is traveling, and use various methods to remove the wiggle when the bolt is locked up.
Anyway, in summary:
Specifically, tolerances and clearances.
99% of the time, when someone who isn’t an engineer (so, me, @308pirate, and a few other people) says “tolerances” on this website - for example, complaining about loose tolerances - they are actually talking about “clearances”. They also have no idea what they’re talking about because loose clearances are not inherently a bad thing. Too-tight clearances are inherently a bad thing, so if you have to pick a direction to err...
Nominal clearance is how much gap there is supposed to be between two components. If the bolt rattles around like it’s dancing the Macarena, the actual clearances are loose. If a gnat’s testicle can cause the action to lock up, the actual clearances are tight. Clearances allow you to coat your actions with insert-coating-here, operate in dusty/muddy/icy environments, and can make it slightly easier to bind the action if you’re running the bolt weird. Clearance is critical to proper function, and the range of possible clearances for a product is something that is very much engineered for a specific purpose.
Tolerances are how much the size of something varies from part to part. Tight tolerances have less variation, loose tolerances have more variation. If every individual piece is hand fit, tolerances don’t matter because you start with an interference and remove material as needed. If you’re in a mass production environment, you need to make sure an arbitrary bolt can work with an arbitrary action - and if the combination of nominal clearance and achievable tolerance can result in an interference, you get to deal with horrifically expensive rework, possibly of an entire production run.
The problem is, cutting tolerances in half increases manufacturing cost by an order of magnitude. As such, when Remington or someone is making a bunch of cheap rifles, they increase clearances by an astronomical amount to make sure the ancient machines and tools that they never budgeted to maintain, and therefore are incapable of holding reasonable tolerances, deliver parts that can technically fit together. And hey, for someone who thinks minute of deer at 50 yards is all anyone needs, and who thinks cherry-picked 3-shot groups are enough to prove accuracy, that works just fine. That describes pretty much everyone who bought Remington rifles in the last couple decades, and the manufacturing is cheap, so the profit potential is phenomenal, and so only a conglomerate of assholes intentionally trying to suck out every penny of value into their own pockets could drive company into bankruptcy.
On the opposite end of the spectrum, you have companies like Defiance, with tight tolerances that allow them to have really tight clearances that are legendary for locking up in dusty environments - unless you tell them you’re going to be operating in dust, or cerakoting, or whatnot, and they are perfectly happy to loosen clearances up for you while keeping tight tolerances. They know essentially exactly how much clearance they’re going to have between the bolt and the action body, and know what the clearances need to be for pretty much every use case to feel perfect, but since the default buyer tends to only care about how tight the bolt is in the action body that’s what they default to.
Then you get to some of the other cases who hold very tight tolerances, so they can have variable clearances for different parts of the bolt cycle. Borden and ARC actions both have looser clearances when the bolt is traveling, and use various methods to remove the wiggle when the bolt is locked up.
Anyway, in summary:
- Nominal clearance: how much gap there is supposed to be
- Actual clearances: how much gap there actually is, which should be within tolerance bounds of the nominal clearance
- Tight clearance: less ability to handle dust/etc
- Loose clearance: people complain
- Tolerance: how much the gap is allowed to vary from part to part
- Tight tolerance: really expensive, but allows good control of clearances, and prefits, and interchangeability, and...
- Loose tolerance: really cheap
Last edited:
