Skip to Content

How to Measure Headspace Without a Gauge?

Do we believe the title is a bit too perplexing? Not to worry, we will be sharing a lot today to make sense of what you’re reading. After all, that’s what we all want right?

Our discussion will be on how to measure headspace without a gauge. Taking that as the base of our discussion, we will be talking about why it is a bad idea and what are the steps you should follow.

If you want to know how to measure headspace in a rifle then you should have a commitment to follow the instructions to the letter. And eyeballing such things isn’t too healthy for the rifle and the round you’re about to fire.

We already talked about the basis of our discussion. The rest will be simple guides to measure headspace with the right tools. And the discussion will continue with expert opinions on not using gauges.

So, let’s get started, shall we?

How to check AR headspace without a gauge: Things expert do

Before diving into the basic discussion, it is important to discuss what is headspace.

Headspace: The Definition

Headspace, in simple terms, is the measurement of the cartridge chamber. You measure it from the ‘datum line’ – a proper place in the shoulder that has a finite and predetermined diameter (the distance from the face to bolt).

It’s a measure of the minimum chamber size that a round sits in before firing, even when there are gunk and grime in it.

Hopefully, the definition won’t carry any misconception of gun part names any further. 

Importance of headspace

The headspace is a measure of suitability.

Let’s say the chamber size is not within the error percentage. It means that the calibrated rounds are either too large or too small to fit in it.

This may cause issues like pressure failures and uneven firing. Other problems include decreased precision, reduced case lifetime and no firing.

Also, the gunpowder may also get discarded into the face of the user (it’s one of the very reasons for users to use eye protection while using a firearm for the very first time).

Error percentage for headspace

You will find that each gun can chamber specific types and shapes of ammo.

That’s because the spacing from the cartridge to the shoulder is needed to fit 99.99% of the time. The tolerance levels for both the chamber and the round must be minimum. It means they must not match each other’s headings.

The only compromise you can make is for the chamber size, which shouldn’t vary more than six-thousandths of an inch or 0.006. It is the current standard for variation.

How to check headspace on ar15: Things you’ll need to measure properly

­We will provide the three basic elements that you can use to check the headspace for an AR15. But these tools will work for other firearms as well.

The ‘Go’ Gauge

If the bolt doesn’t close correctly, then the barrel screw is tight. In short, you don’t have the correct fit for a bullet to sit in a chamber.

Reliable fit is what the Go-gauge tries to determine.

The ‘No-Go’ Gauge

If the chamber closes, then you have a bigger chamber. It’s a situation where the brass gets stretched, which is never a good thing.

Brass stretching is a sign of decreased lifetime for the brass.

The Field Gauge

The field gauge is for military purposes only.

  • Insert the gauge
  • Close the chamber

If it closes immediately, then you have a large chamber size. For military use, a large chamber is okay because they are not bent on the brass lifetime.

Checking headspace without a gauge: How it’s done

If you want to know how to measure headspace on a bolt action without a gauge, then there’s hope for you.

Just follow the steps below:

  • Place a piece of brass and flush timer without ammo and gunpowder into the chamber. Insert the bolt
  • Slide a firing pin by the back of the bolt and let it touch the brass.
  • Try and see the difference between the firing pin flush with the bolt face along with the brass.
  • If the gap is minimal, then the headspace you have is substantial.

Be aware that this method is from an expert user who knows his way. If you’re not confident enough, then don’t put the integrity of your materials in jeopardy. There are a lot of inconsistencies, which will lead to failure.

Final thoughts

All you need is to have gauges to measure the headspace. Although they are a bit pricey, you should try and get your hands on any of the suitable options.

The risks involved are just too great, especially if you are not a seasoned rifleman. But make sure that the metal part of the gun is taken through proper metal maintenance chores. 

We gave you the tools and a fair warning. The rest is up to you.