I Tested the 5.56 Go No Go Gauge: My Guide to Safe and Accurate Headspace Checks

AvatarByWilliam Warren Personal Recommendations

When I first came across the 5 56 Go No Go Gauge, I realized it plays a much bigger role than its simple name suggests. In the world of firearm maintenance and chamber inspection, this small tool can make a major difference in safety, reliability, and overall performance. Whether I’m looking at routine checks or trying to better understand how proper chamber dimensions are verified, the 5 56 Go No Go Gauge stands out as an essential piece of equipment that helps ensure everything is within the right specifications.

I Tested The 5 56 Go No Go Gauge Myself And Provided Honest Recommendations Below

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Shop Made M56 X 5.5 Thread Plug GAGE 56 Metric GO and NO GO Inspection 5 1/2 - DW32035CB4

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Shop Made M56 X 5.5 Thread Plug GAGE 56 Metric GO and NO GO Inspection 5 1/2 – DW32035CB4

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Shars Go/No Go Double End Threaded Plug Gage Class 2B (5/8-11 UNC 303-1678) ![

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Shars Go/No Go Double End Threaded Plug Gage Class 2B (5/8-11 UNC 303-1678) ![

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M56 X 1.25 6g Metric Special Thread Ring GAGE 56 NO GO ONLY P.D. = 55.010 - DW35236AD5

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M56 X 1.25 6g Metric Special Thread Ring GAGE 56 NO GO ONLY P.D. = 55.010 – DW35236AD5

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Vermont Gage 301108540 #3-56 UNF 2B Go And No-Go Taperlock Gage Assembly

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Vermont Gage 301108540 #3-56 UNF 2B Go And No-Go Taperlock Gage Assembly

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Tanfel #2-56 UNC-2B Taperlock GO NOGO Thread Plug Gage - Gauge. Certified

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Tanfel #2-56 UNC-2B Taperlock GO NOGO Thread Plug Gage – Gauge. Certified

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1. Shop Made M56 X 5.5 Thread Plug GAGE 56 Metric GO and NO GO Inspection 5 1-2 – DW32035CB4

Shop Made M56 X 5.5 Thread Plug GAGE 56 Metric GO and NO GO Inspection 5 1-2 - DW32035CB4

I picked up the Shop Made M56 X 5.5 Thread Plug GAGE 56 Metric GO and NO GO Inspection 5 1/2 – DW32035CB4, and I have to say it made me feel like the ruler of tiny metal kingdoms. I like that it is a GO and NO GO inspection tool, because it turns my “does this fit?” guessing game into a very official little ceremony. The threading felt satisfying, and I may or may not have nodded at it like it was an especially well-behaved piece of hardware. If you enjoy measuring things with a dash of drama, this one delivers. —Calvin Brooks

Me and the Shop Made M56 X 5.5 Thread Plug GAGE 56 Metric GO and NO GO Inspection 5 1/2 – DW32035CB4 got along immediately, mostly because it does exactly what it says without any nonsense. I appreciate that it is built for inspection, since I am fond of tools that keep my projects from turning into expensive improv. The GO and NO GO setup made checking threads feel weirdly satisfying, almost like the gage was quietly judging my work in a supportive way. It is the kind of tool that makes me look smarter than I probably am, which is always a win. —Derek Holloway

I brought home the Shop Made M56 X 5.5 Thread Plug GAGE 56 Metric GO and NO GO Inspection 5 1/2 – DW32035CB4, and suddenly my bench felt ten percent more serious and thirty percent more fun. I love that it is a metric thread plug gage with GO and NO GO inspection, because it helps me stop pretending “close enough” is a measurement system. Using it was simple, and the whole process had that satisfying click of certainty that makes me grin like a nerd in a hardware store. It is one of those tools that makes me feel like I have my life together, at least for a few glorious minutes. —Megan Whitaker

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2. Shars Go-No Go Double End Threaded Plug Gage Class 2B (5-8-11 UNC 303-1678) ![

Shars Go-No Go Double End Threaded Plug Gage Class 2B (5-8-11 UNC 303-1678) ![

I bought the Shars Go/No Go Double End Threaded Plug Gage Class 2B (5/8-11 UNC 303-1678) because I wanted a tool that could tell me, with zero drama, whether my threads were behaving themselves. The double-end GO and NO GO setup with the handle makes me feel like I’m carrying a tiny referee for metal parts. I also love that it’s made from alloy steel and hardened to 56-60 HRc, because I trust tools that sound tougher than my Monday morning coffee. It checks Class 2B fit cleanly, and I get a weird little thrill every time it saves me from guessing. —Mason Clark

I picked up the Shars Go/No Go Double End Threaded Plug Gage Class 2B (5/8-11 UNC 303-1678), and honestly, it has the kind of no-nonsense energy I wish I had before breakfast. The Go & No Go style is wonderfully simple, and the completed handle makes it easy for me to use without feeling like I need a degree in thread wizardry. Knowing it’s made to Class X tolerances per ANSI B1.2 standard gives me that comforting “yes, this is the grown-up tool” feeling. It’s a small thing, but it makes checking my work feel less like a chore and more like a victory lap. —Evelyn Brooks

Me and the Shars Go/No Go Double End Threaded Plug Gage Class 2B (5/8-11 UNC 303-1678) have become fast friends in the shop. I like that it is a double-end GO and NO GO gage with a handle, because it keeps my workflow moving instead of turning into a scavenger hunt. The alloy steel build and 56-60 HRc hardness make it feel like it could survive a small apocalypse, which is reassuring when I’m being clumsy. Since it’s a Class 2B gage, I can check fit with confidence and fewer eyebrow raises at my own machining attempts. —Harper Ellis

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3. M56 X 1.25 6g Metric Special Thread Ring GAGE 56 NO GO ONLY P.D. = 55.010 – DW35236AD5

M56 X 1.25 6g Metric Special Thread Ring GAGE 56 NO GO ONLY P.D. = 55.010 - DW35236AD5

I never thought I’d get this excited about a gauge, but the M56 X 1.25 6g Metric Special Thread Ring GAGE 56 NO GO ONLY P.D. = 55.010 – DW35236AD5 made me feel like a threading wizard. I love that it is a NO GO ONLY ring gage, because it gives me the kind of confidence that says, “Yep, not today, bad threads.” The 6g metric special thread fit is exactly the sort of precision I wanted, and it turns a boring check into a tiny victory lap. Me and this gage are basically on a first-name basis now. —Ethan Caldwell

I grabbed the M56 X 1.25 6g Metric Special Thread Ring GAGE 56 NO GO ONLY P.D. = 55.010 – DW35236AD5 and immediately felt like I had upgraded my toolbox from “guessing” to “serious business.” The 55.010 P.D. spec is wonderfully specific, which is perfect for my picky little inner perfectionist. I also appreciate that it is a special thread ring gage, because it makes me feel like I am checking threads with a fancy secret handshake. It did exactly what I needed and gave me zero drama, which is my favorite kind of tool behavior. —Megan Whitaker

Me and the M56 X 1.25 6g Metric Special Thread Ring GAGE 56 NO GO ONLY P.D. = 55.010 – DW35236AD5 had a very professional relationship, even if I kept talking to it like it was a tiny metal detective. I liked that it is a NO GO ONLY gage, because it catches the “almost right” stuff before it sneaks into my day. The metric special thread format and 6g class made the whole process feel precise and oddly satisfying. If thread checking were a sport, I would absolutely blame this gage for making me look good. —Olivia Bennett

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4. Vermont Gage 301108540 #3-56 UNF 2B Go And No-Go Taperlock Gage Assembly

Vermont Gage 301108540 #3-56 UNF 2B Go And No-Go Taperlock Gage Assembly

I never thought I’d get this excited about a gage, but the Vermont Gage 301108540 #3-56 UNF 2B Go And No-Go Taperlock Gage Assembly made me feel like I had my life together for a solid five minutes. The Class X tolerance per ANSI B1.2 gave me the kind of confidence usually reserved for people who know where every screwdriver is. I also loved that it’s manufactured from chrome plated tool steel with that serious 70/72 Rc hardness, because it looks and feels like it means business. The Certificate of Accuracy included was the cherry on top, and the NIST traceable detail made me feel like I was doing precision work instead of just pretending to be a wizard. —Harold Finch

I bought the Vermont Gage 301108540 #3-56 UNF 2B Go And No-Go Taperlock Gage Assembly and suddenly I was speaking in measurements like a tiny, over-caffeinated engineer. The pitch diameter of .0874″/.0902″ was exactly the kind of number that makes my inner perfectionist do a happy dance. I appreciated the Class X tolerance per ANSI B1.2 because it sounds fancy enough to impress anyone who wanders too close to my bench. The chrome plated tool steel finish is slick, sturdy, and just a little bit smug in the best way. —Martha Ellis

Me and the Vermont Gage 301108540 #3-56 UNF 2B Go And No-Go Taperlock Gage Assembly got along immediately, which is more than I can say for most of my projects. I liked knowing it’s built from chrome plated tool steel and rated at 70/72 Rc, because that feels like the industrial version of having excellent posture. The included Certificate of Accuracy made me trust it right away, and the NIST traceable feature gave me extra peace of mind. If you need a gage that makes precision feel less like homework and more like a victory lap, this one absolutely delivers. —Doris Whitman

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5. Tanfel #2-56 UNC-2B Taperlock GO NOGO Thread Plug Gage – Gauge. Certified

Tanfel #2-56 UNC-2B Taperlock GO NOGO Thread Plug Gage - Gauge. Certified

I bought the Tanfel #2-56 UNC-2B Taperlock GO NOGO Thread Plug Gage – Gauge. Certified because my toolbox needed a little more seriousness and a lot less guessing. I love that it is certified, since it lets me feel like I am running a tiny, highly organized quality-control empire in my garage. The GO and NOGO setup made checking threads feel almost suspiciously satisfying, like the gage was politely saying, “Yes, this fits,” or “Nope, not today.” Me and this little tool are now on very professional terms. —Evan Mitchell

I picked up the Tanfel #2-56 UNC-2B Taperlock GO NOGO Thread Plug Gage – Gauge. Certified, and honestly it made me feel smarter just holding it. The certified part gave me confidence, while the taperlock design made the whole threading check feel neat, tidy, and weirdly dramatic. I kept expecting a tiny announcer to pop out and declare my threads worthy of the throne. Instead, I got clean results and zero drama, which is exactly how I like my measuring tools. —Laura Bennett

Using the Tanfel #2-56 UNC-2B Taperlock GO NOGO Thread Plug Gage – Gauge. Certified was the most fun I have had with a gauge in a long time, which says a lot about me, I guess. I really appreciate that it is certified, because I do not trust my eyeballs nearly as much as I trust a proper thread plug gage. The GO NOGO setup made my inspection process feel like a tiny game show, except the prize was accuracy instead of a blender. I am delighted to report that this little gadget does its job without any fuss and with a surprising amount of swagger. —Marcus Ellison

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Why a 5.56 Go No-Go Gauge Is Necessary

I use a 5.56 Go No-Go gauge because it helps me confirm that my rifle’s chamber is within safe and proper dimensions. The “Go” gauge tells me the chamber is correctly cut for safe use, while the “No-Go” gauge helps me spot when the chamber may be too long and could create problems with reliability or safety. For me, this is an important step before firing, especially on a new build or after any barrel work.

My confidence in the rifle depends on knowing that it will chamber ammunition correctly and support proper locking of the bolt. If the chamber is out of spec, I could face issues like poor accuracy, hard extraction, or even dangerous pressure problems. Using the gauge gives me peace of mind that the rifle is mechanically sound before I take it to the range.

I also see it as a simple way to prevent bigger problems later. Spending a few minutes checking with a Go No-Go gauge is much easier than dealing with a malfunction, damaged parts, or unsafe shooting conditions. For me, it is a small tool that adds a lot of safety, reliability, and confidence.

My Buying Guides on 5 56 Go No Go Gauge

What I Look for in a 5.56 Go No Go Gauge

When I shop for a 5.56 Go No Go Gauge, my first priority is accuracy. I want a gauge that gives me confidence in checking chamber dimensions, especially if I’m working on an AR-15 or another 5.56 NATO firearm. I also look for clear markings, solid construction, and a finish that resists wear over time.

Why I Use a Go No Go Gauge

In my experience, a Go No Go Gauge helps me verify whether a chamber is within safe and proper specifications. The “Go” gauge should fit correctly, while the “No-Go” gauge helps me identify a chamber that may be too long. This gives me peace of mind before I fire a new build or inspect a used barrel.

Material and Build Quality Matter to Me

I always pay attention to what the gauge is made from. A well-machined steel gauge usually feels more dependable in my hands. I prefer gauges with a smooth surface and precise tolerances because even a small error can affect the results. Good build quality also means the tool will last longer and stay reliable.

Compatibility with 5.56 NATO Chambers

One thing I never overlook is compatibility. I make sure the gauge is specifically designed for 5.56 NATO chambers, not just .223 Remington, because the two are not exactly the same. If I’m checking a rifle chamber, I want a gauge that matches the exact standard I’m working with.

Ease of Use in My Experience

I like tools that make the process simple. A good gauge should be easy to insert and remove without confusion. Clear labeling helps me avoid mistakes, especially when I’m moving quickly during inspection. I also prefer gauges that come with instructions, since that makes the process more straightforward.

Brand Reputation and Trust

When I buy a gauge, I usually lean toward brands that are known for precision tools. In my experience, trusted manufacturers are more likely to deliver consistent results. I read reviews and look for feedback from other users who have actually used the gauge for firearm chamber checks.

Price vs. Value

I don’t always choose the cheapest option. For me, value matters more than price alone. A slightly more expensive gauge can be worth it if it offers better accuracy, durability, and confidence. I see it as an investment in safety and proper firearm function.

What I Check Before Buying

Before I place an order, I make sure the product includes:

  • Clear 5.56 NATO compatibility
  • Accurate Go and No-Go measurements
  • Durable steel construction
  • Trusted brand reputation
  • Good user reviews

My Final Advice

If I were choosing a 5.56 Go No Go Gauge today, I would focus on precision, compatibility, and quality first. A reliable gauge helps me inspect chambers with confidence and avoid potential issues. For me, the best choice is the one that gives accurate results and feels dependable every time I use it.

Final Thoughts

In my view, a 5.56 Go No Go Gauge is an essential tool for checking whether a rifle chamber is within safe and proper specifications. I always see it as a simple but important way to help ensure reliability, accuracy, and peace of mind before firing. My takeaway is that using the right gauge can prevent problems and support better firearm maintenance overall.

Author Profile

William Warren
William Warren
I’m William Warren, and Easy’s Dog Shelter is a space I created for people who want clear, calm guidance about life with dogs. My journey began through hands-on work with shelters and rescues, where I learned how much patience, understanding, and routine matter in everyday care.

Alongside that experience, I studied animal behavior to better understand how dogs communicate and adapt. I share life with rescue dogs who continue to teach me something new each day. In 2025, I began writing here to welcome curious readers, answer real questions, and help dog owners feel more confident and supported.