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September 9th, 2021

Headspace Basics — What You Need to Know

Ultimate Reloader Brownells headspacing go gage gauge barrel gunsmithing
This illustration shows headspace measurement for the popular .308 Winchester cartridge, which headspaces on the shoulder. Image copyright 2015 Ultimate Reloader.

In this Brownells Tech Tip Video, Brownells gun tech Steve Ostrem explains what headspace is and why it’s one of the most critical measurements for nearly all firearms. Even if you’re an experienced rifle shooter, it’s worth watching this video to refresh your understanding of headspace measurements, and the correct use of “GO” and “NO-GO” gauges.

Headspace Definition
In firearms, headspace is the distance measured from the part of the chamber that stops forward motion of the cartridge (the datum reference) to the face of the bolt. Different cartridges have their datum lines in different positions in relation to the cartridge. For example, 5.56x45mm NATO ammunition headspaces off the shoulder of the cartridge, whereas .303 British headspaces off the forward rim of the cartridge. If the headspace is too short, ammunition that is in specification may not chamber correctly. If headspace is too large, the ammunition may not fit as intended or designed and the cartridge case may rupture, possibly damaging the firearm and injuring the shooter. (Source: Wikipedia)

Forster Headspace diagram belted magnum rimfire

Problems Caused by Too Much Headspace
Excessive headspace issues can include: light primer strikes, failure to fire, bulged/blown cases, case separations, split shoulders, or unseated primers after firing. Case ruptures caused by excessive headspace can lead to catastrophic failures causing serious injury. That is why headspace is such an important measurement.

Problems Cause by Too Little Headspace
Insufficent (or excessively tight) headspace can prevent the firearm from going into battery, resulting in failure to fire or deformation of the cartridge case. Various feeding and functioning problems can be caused by cases with too little headspace, even if a round can be chambered (with effort).

Go gauge gage NOGO no-go field gaugesHeadspace Gauges
Headspace is measured with a set of two headspace gauges: a “Go” gauge, and a “No-Go” gauge. Headspace gauges resemble the cartridges for the chambers they are designed to headspace, and are typically made of heat-treated tool steel. Both a “Go” and a “No-Go” gauge are required for a gunsmith to headspace a firearm properly. A third gauge, the “Field” gauge, is used (as the name implies) in the field to indicate the absolute maximum safe headspace. This gauge is used because, over time, the bolt and receiver will wear, the bolt and lugs compress, and the receiver may stretch, all causing the headspace to gradually increase from the “factory specs” measured by the “Go” and “No-Go” gauges. A bolt that closes on “No-Go” but not on “Field” is close to being unsafe to fire, and may malfunction on cartridges that are slightly out of spec. (Source: Wikipedia)

To learn more, read Brownell’s article Headspace Gauges and How to Use Them. Among other things, this explains the relative lengths of “Go”, “No-Go”, and “Field” gauges. The “Field” is actually the longest: “The GO gauge corresponds to the SAAMI minimum chamber length, while the FIELD gauge usually matches the maximum chamber depth, or slightly less. NO-GO gauges are an intermediate length between minimum and maximum, that, technically, is a voluntary dimension. A firearm that closes on a NO-GO gauge and does not close on a FIELD gauge may not give good accuracy and may have very short cartridge case life from the ammunition re-loader’s standpoint.”

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January 9th, 2020

GUN INFO 101 — Headspace Defined and Illustrated

Ultimate Reloader Brownells headspacing go gage gauge barrel gunsmithing
This illustration shows headspace measurement for the popular .308 Winchester cartridge, which headspaces on the shoulder. Image copyright 2015 Ultimate Reloader.

In this Brownells Tech Tip, Brownells gun tech Steve Ostrem explains what headspace is and why it’s one of the most critical measurements for nearly all firearms. Even if you’re an experienced rifle shooter, it’s worth watching this video to refresh your understanding of headspace measurements, and the correct use of “GO” and “NO-GO” gauges.

Headspace Definition
In firearms, headspace is the distance measured from the part of the chamber that stops forward motion of the cartridge (the datum reference) to the face of the bolt. Used as a verb, headspace refers to the interference created between this part of the chamber and the feature of the cartridge that achieves the correct positioning. Different cartridges have their datum lines in different positions in relation to the cartridge. For example, 5.56x45mm NATO ammunition headspaces off the shoulder of the cartridge, whereas .303 British headspaces off the forward rim of the cartridge.

If the headspace is too short, ammunition that is in specification may not chamber correctly. If headspace is too large, the ammunition may not fit as intended or designed and the cartridge case may rupture, possibly damaging the firearm and injuring the shooter. (Source: Wikipedia)

Forster Headspace diagram belted magnum rimfire

Go gauge gage NOGO no-go field gaugesHeadspace Gauges
Headspace is measured with a set of two headspace gauges: a “Go” gauge, and a “No-Go” gauge. Headspace gauges resemble the cartridges for the chambers they are designed to headspace, and are typically made of heat-treated tool steel. Both a “Go” and a “No-Go” gauge are required for a gunsmith to headspace a firearm properly. A third gauge, the “Field” gauge, is used (as the name implies) in the field to indicate the absolute maximum safe headspace. This gauge is used because, over time, the bolt and receiver will wear, the bolt and lugs compress, and the receiver may stretch, all causing the headspace to gradually increase from the “factory specs” measured by the “Go” and “No-Go” gauges. A bolt that closes on “No-Go” but not on “Field” is close to being unsafe to fire, and may malfunction on cartridges that are slightly out of spec. (Source: Wikipedia)

To learn more, read Brownell’s longer article Headspace Gauges and How to Use Them. Among other things, this explains the relative lengths of “Go”, “No-Go”, and “Field” gauges. The “Field” is actually the longest: “The GO gauge corresponds to the SAAMI (Sporting Arms & Ammunition Manufacturer’s Institute) minimum chamber length, while the FIELD gauge usually matches the maximum chamber depth, or slightly less. NO-GO gauges are an intermediate length between minimum and maximum, that, technically, is a voluntary dimension. A firearm that closes on a NO-GO gauge and does not close on a FIELD gauge may not give good accuracy and may have very short cartridge case life from the ammunition re-loader’s standpoint.”

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February 4th, 2018

Full-Length Sizing Die Fit — Diagnosing Stiff Bolt Lift Problems

Resizing Die Alex Wheeler Shoulder Bump Die fitting Full-Length

In this video, gunsmith Alex Wheeler explains how to ensure that your full-length sizing dies fit your brass properly. With many cartridge types, it’s not unusual for factory dies to be slightly large in the bottom section. When the diameter of a FL-sizing die is too large near the base, this can leave the bottom section of fired cases “unsized”, with the result that you can have extraction issues and stiff bolt lift, or what Alex calls “clickers”. At the same time, it’s not unusual for dies to over-size fired cases at the shoulder (i.e. reduce the shoulder diameter by .004″ or more).

We strongly recommend that all hand-loaders watch this video, particularly if you load cases 6+ times with relatively high-pressure loads.

Alex explains that a key dimension is the diameter of a fired case 0.200″ above the case head. If your die does not size your fired cases at this point, you should get a FL die that does. This could be a custom die ground to fit your chamber, or it could be a “small-base” die specifically designed to “hit” the bottom section of the case. Alex also notes that some FL dies have an inside chamfer at the mouth of the die, right at the very bottom. (See video at 3:55). This can leave the section of the case right above the extractor groove unsized, which can also lead to “clickers” and stiff bolt lift.

Paint Your Brass to Find Problem Areas
If you are having stiff bolt lift or extraction issues, Alex explains that you can “paint” your brass with magic marker (or dye-chem), and then place the case in your chamber. On the “hot spots” where the case contacts the chamber wall, the marking will rub off, allowing the brass metal to shine through in the problem area(s). This will illustrate where you need better sizing from your die.

“You can ink up the case with some magic marker or dye-chem. If you are getting clickers, go ahead and mark up the case and chamber it and see where it’s wearing. This will help you diagnose [whether the problem] is coming from the base, is it coming maybe from a score in the chamber… it can even happen at the shoulder although that’s pretty rare. Usually the dies size enough at that point.”

Did you find this video helpful? View more informative Tech Tip Videos on WheelerAccuracy.com.

Video Tip from Boyd Allen. We welcome reader submissions.
Permalink - Videos, Bullets, Brass, Ammo, Reloading 2 Comments »
October 6th, 2017

The Firing Sequence — What Happens Inside Cartridge & Chamber

Sinclair International Reloading Videos

Sinclair International has produced an eight-part video series on metallic cartridge reloading, hosted by Sinclair’s former President Bill Gravatt. The entire series can be viewed (for free) via Sinclair’s YouTube Channel. While this set of videos starts with the basics, it covers many more advanced aspects of reloading as well. Accordingly, both novice and experienced reloaders can benefit from watching the eight videos. We think everyone should watch Video No. 2. Introduction to Reloading Safety, which provides guidelines for safe reloading practices.

Watch Firing Sequence Video

We also strongly recommend Video No. 4 to readers who are getting started in reloading. This “How Things Work” segment covers the sequence of events inside the chamber (and barrel) when the cartridge is fired. The video includes helpful graphics that show what happens to the primer, powder, cartridge, and bullet when the round is fired. The video also illustrates “headspace” and explains how this can change after firing. We think this video answers many common questions and will help reloaders understand the forces at work on their brass during the firing process.

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January 28th, 2017

TECH TIP: Clean Your Chamber and Lug Recesses

Most competitive shooters are pretty good about bore cleaning (some may even clean their bores too aggressively). However, we’ve found that many shooters neglect the chamber area and the bolt lug recesses. It’s too easy to clean the bore, slip out the guide rod and say “I’m done.” Sinclair Int’l explains why it’s important to clean the action interior: “Shooters use a lot of grease and oil on their bolts to reduce friction and to prevent wear[.] Unfortunately, both of these compounds attract grit, powder and primer residues. Cleaning your receiver is especially critical [with] custom actions where the fit between the action and bolt is held to very tight tolerances. Routine cleaning of the action will prevent unnecessary wear on the bolt body, locking lugs, and the action raceways/guide rails. Frequent action cleaning is also essential to keeping the trigger area free of debris which can cause trigger hang-ups and failures.” Below, we present action cleaning advice from Sinclair’s Reloading Press Newsletter.

Cleaning the Chamber
Combustion by-products, lubricants, and solvent residues can collect in your chamber. Severe build-up of grease and carbon can interfere with chambering. Also some solvents will promote corrosion. You need to keep your chambers clean.

Bolt Action Cleaning

1) Install a clean cotton mop of the correct size on the end of a chamber rod and insert the mop into the chamber. Rotate the mop several times to remove any brush bristles left behind and any excess solvent that was between the rod guide snout and the end of the chamber. Make sure the chamber is dry. Prior to storing a rifle you can oil the chamber but make sure the oil is removed prior to firing the rifle.
2) Alternatively, install an old bore brush on a chamber rod, overlap a couple of patches on the brush bristles, and wrap them around the brush completely. Then insert the patch-covered brush into the chamber while rotating it to remove the excess solvent and debris. Push it firmly into the neck area of the chamber. A similar method is to pierce a large patch on the end of the brush loop and insert it into the action, again rotating the brush as you push the patch up against the breech.

Cleaning the Lug Recess Area
The action lug recess area is one of the dirtiest places on a bolt-action rifle. To properly clean this area, always use a tool designed for the task, such as the $21.50 Sinclair Action Cleaning Tool (part # ACT1) which is part of the Sinclair Action Cleaning Tool Kit (now on sale for $29.99, part #ACT2).

Bolt Action Cleaning

1) Insert a cotton roll or cleaning felt into your lug recess cleaning tool and wet both ends and the face of the cotton roll/felt with solvent.
2) Insert the tool into the action and push it forward until it is positioned fully in the lug recess area and rotate the tool head several times. Then reverse the rotation for another few turns. While rotating the tool move it slightly in and out to cover the entire recess area and to also clean the breech face.
3) Remove the tool from the action and inspect the surface of the felt or cotton roll. If there is quite a bit of residue on both sides of the felt/roll, then repeat with another wet felt/roll.
4) When you feel the recess area is completely clean, insert a dry cotton roll into the tool and rotate the tool head to remove any remaining solvent and debris. If necessary, use a second dry cotton roll.
5) You can follow this step up with another pass of a mop or patches into the chamber to get any debris or solvent that pushed forward out of the lug recess area.

Bolt Action Cleaning

Cleaning Tips from The Reloading Press, used courtesy Sinclair Int’l, All Rights Reserved.

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January 14th, 2017

TECH TIP: How To Cast Chambers Using Cerrosafe

Cerrosafe Chamber casting bismuth

There are many reasons you might want to make a chamber cast. You may have acquired an older rifle and need to verify the chamber dimensions. Or, if you have a new reamer, you may want to check the exact “cut” dimensions against the blueprint specs. A chamber casting is also valuable if you run across a firearm that you believe has a custom barrel on it and you want to find out the dimensions of the chamber. Lastly, you may want to prepare a chamber casting to be used in the making of custom dies. (Most reloading die makers know how to work from Cerrosafe chamber casts.)

Cerrosafe Chamber CastingCerrosafe is a metal alloy that has some unique properties which make it ideal for chamber casting. First, it has a relatively low melting point of 158 to 190° Fahrenheit. This makes it easy for the handloader to melt the Cerrosafe in his home shop. Second, it shrinks slightly during cooling which allows it to be extracted from the chamber easily. It then re-expands to the chamber’s original size after about one hour at room temperature. After cooling for about 200 hours, the chamber cast will expand to about .0025″ larger than the actual chamber size.

One of our Forum members has done many Cerrosafe castings and he offers this smart advice:

1. Remove the barrel from the action to make the pour much easier. If you don’t remove the barrel, it can be hard to pour through the action (even with a funnel) and can make a mess if you’re not careful.
2. Pre-heat the barrel for 5-10 minutes in the oven on the very lowest setting (170° F in my oven). (DON’T overdo it!). Allow to cool for a couple minutes so you can pick it up and it is under 120° F. Pre-heating the barrel helps the Cerrosafe stay liquid as you pour the casting. This helps ensure a good, complete fit to the chamber.

Brownells has an article about Cerrosafe chamber casting that explains how to use this unique material:

How to Use Cerrosafe for Chamber Casting
The basic ingredient of Cerrosafe is bismuth. Bismuth is a heavy, coarse, crystalline metal which expands when it solidifies, up to 3.3% of its volume. When bismuth is alloyed with other metals, such as lead, tin, cadmium and indium, this expansion is modified according to the relative percentages of bismuth and other components present. As a general rule, bismuth alloys of approximately 50% bismuth exhibit little change of volume during solidification. Alloys containing more than this tend to expand during solidification and those containing less tend to shrink during solidification.

What all this means for the gunsmith is that you can make chamber castings using only Cerrosafe and a few, simple hand tools. To make a chamber casting, first clean and degrease the chamber. Use a tight-fitting, cotton patch that’s wrapped around a bore mop or brush to plug the bore just ahead of the throat. I usually leave the cleaning rod attached to the plug until it’s time to remove the plug. Melt the entire bar of Cerrosafe in a heatproof container that you can easily pour the hot Cerrosafe out of. You can use a propane torch or heat over a hot plate or the burner of a stove. Cerrosafe melts easily at 158°-195° F. While the casting metal is still liquid, stir very well, skim off the dross, and pour your chamber. The real trick with Cerrosafe is not to overheat it. If you heat the solid slowly, and keep it within the required temperature range, you shouldn’t get any dross.

Note the time the casting was poured. The casting will take only a very short time to solidify, usually within a minute. Wait 30 minutes and then remove the plug from the bore. Turn the muzzle upward and the casting will fall from the chamber. At 30 minutes after initial solidification, Cerrosafe shrinks slightly, so removal is very easy. Allow the new casting to cool thoroughly then measure the casting exactly one hour from the time it was cast. The casting will give you an exact measurement of the chamber. Cerrosafe casting metal can be used over and over. Remelt the entire amount back together and pour the Cerrosafe into a small mold of the appropriate size. Always melt the entire Cerrosafe ingot to make a chamber casting. For best results, never cut off, or use, just a part of the ingot.

Permalink Gunsmithing, Tech Tip 5 Comments »
August 3rd, 2015

New Bore Guide Products from 21st Century Shooting

Chamber-specific bore guide off barrel solvent chamber seal 21st Century Shooting John Perkins

It’s important to use a good-fitting bore-guide whenever you clean your barrel. A good bore-guide will keep solvents out of your action and help your cleaning rods run straight and true.

Not all bore guides are created equal. Some offer a sloppy fit and/or fail to seal your chamber effectively. 21st Century Shooting has changed all that with a new generation of chamber-specific Bore Guides. These have a close fit (with O-rings) to seal your chamber completely. The design is intelligent — these bore guides are long enough to extend well past the end of your scope, while the minimal rod diameter provides sufficient clearance for most combs. Priced at $49.99, these high-tech guide rods are custom crafted to fit many popular chamberings: 220 Swift, 223 Rem, 22-250, 6PPC, 6mmBR, 6 Dasher, 6×47, 6-284, 6mm Shehane, 243 WSM, 6.5×47 Lapua, 6.5-284, 6.5 Shehane, 6.5 WSM, 25-06, 270 WSM, .284 Win, 7mm Shehane, 7mm WSM, 30 BR, 308 Win, 30-06, 300 WSM.

Chamber-specific bore guide off barrel solvent chamber seal 21st Century Shooting John Perkins

Email John [at] 21stcenturyshooting.com to ask about your application. These chamber-specific guide rods are designed fit actions with BAT bolts or Rem 700-style bolts (Borden, Kelblys, Ruger, Savage).


In addition to the new chamber-specific Guide Rods, 21st Century just released a clever new product for shooters who regularly swap barrels (or who need to clean dismounted barrels). If you have a switch-barrel rig, check out 21st Century’s new Barrel Off Bore Guides. Like the full-length 21st Century bore guides, these are manufactured specifically for your chamber, for a perfect fit. These chamber-specific “Barrel Off” bore guides cost $19.99.

Chamber-specific bore guide off barrel solvent chamber seal 21st Century Shooting John Perkins

Product Tip from EdLongrange. We welcome reader submissions.

Permalink Gear Review, New Product 1 Comment »
December 6th, 2014

Got Stub? Barrel Stub Gauges Serve Many Functions

Next time you have a barrel fitted, consider having your gunsmith create a “stub gauge” from a left-over piece of barrel steel (ideally taken from your new barrel blank). The outside diameter isn’t important — the key thing is that the stub gauge is created with the same reamer used to chamber your current barrel, and the stub must have the same bore diameter, with the same land/groove configuration, as the barrel on your rifle. When properly made, a stub gauge gives you an accurate three-dimensional model of the upper section of your chamber and throat. This comes in handy when you need to bump your case shoulders. Just slide a fired case (with spent primer removed) in the stub gauge and measure from base of case to the end of the gauge. Then, after bumping, re-measure to confirm how much you’ve moved the shoulder.

Barrel Stub Gauge

In addition, the stub gauge lets you measure the original length to lands and freebore when your barrel was new. This gives you a baseline to accurately assess how far your throat erodes with use. Of course, as the throat wears, to get true length-to-lands dimension, you need take your measurement using your actual barrel. The barrel stub gauge helps you set the initial bullet seating depth. Seating depth is then adjusted accordingly, based on observed throat erosion, or your preferred seating depth.

Forum member RussT explains: “My gunsmith [makes a stub gauge] for me on every barrel now. I order a barrel an inch longer and that gives him enough material when he cuts off the end to give me a nice case gauge. Though I don’t have him cut that nice-looking window in the side (as shown in photos). That’s a neat option. You can tell how much throat erosion you are getting from when it was new as well. For measuring initial seating depths, this is the most useful item on my loading bench next to calipers. Everyone should have a case gauge made by there smith if you have a new barrel put on.”

Forum member Lawrence H. has stub gauges made with his chamber reamers for each new barrel. He has his smith cut a port in the stub steel so Lawrence can actually see how the bullet engages the rifling in a newly-cut chamber. With this “view port”, one can also see how the case-neck fits in the chamber. Lawrence tells us: “My stub gauges are made from my barrels and cut with my chamber reamers. With them I can measure where my bullets are ‘touching the lands’ and shoulder bump dimensions. This is a very simple tool that provides accurate information.” To learn more about stub gauges, read this Forum Thread. The photos above and below show Lawrence’s stub gauges:

Barrel Stub Gauge

Permalink Gunsmithing, Reloading No Comments »
January 12th, 2014

Barrel Stub Gauges — Handy for Many Reloading Tasks

Next time you have a barrel fitted, consider having your gunsmith create a “stub gauge” from a left-over piece of barrel steel (ideally taken from your new barrel blank). The outside diameter isn’t important — the key thing is that the stub gauge is created with the same reamer used to chamber your current barrel, and the stub must have the same bore diameter, with the same land/groove configuration, as the barrel on your rifle. When properly made, a stub gauge gives you an accurate three-dimensional model of the upper section of your chamber and throat. This comes in handy when you need to bump your case shoulders. Just slide a fired case (with spent primer removed) in the stub gauge and measure from base of case to the end of the gauge. Then, after bumping, re-measure to confirm how much you’ve moved the shoulder.

Barrel Stub Gauge

In addition, the stub gauge lets you measure the original length to lands and freebore when your barrel was new. This gives you a baseline to accurately assess how far your throat erodes with use. Of course, as the throat wears, to get true length-to-lands dimension, you need take your measurement using your actual barrel. The barrel stub gauge helps you set the initial bullet seating depth. Seating depth is then adjusted accordingly, based on observed throat erosion, or your preferred seating depth.

Forum member RussT explains: “My gunsmith [makes a stub gauge] for me on every barrel now. I order a barrel an inch longer and that gives him enough material when he cuts off the end to give me a nice case gauge. Though I don’t have him cut that nice-looking window in the side (as shown in photos). That’s a neat option. You can tell how much throat erosion you are getting from when it was new as well. For measuring initial seating depths, this is the most useful item on my loading bench next to calipers. Everyone should have a case gauge made by there smith if you have a new barrel put on.”

Forum member Lawrence H. has stub gauges made with his chamber reamers for each new barrel. He has his smith cut a port in the stub steel so Lawrence can actually see how the bullet engages the rifling in a newly-cut chamber. With this “view port”, one can also see how the case-neck fits in the chamber. Lawrence tells us: “My stub gauges are made from my barrels and cut with my chamber reamers. With them I can measure where my bullets are ‘touching the lands’ and shoulder bump dimensions. This is a very simple tool that provides accurate information.” To learn more about stub gauges, read this Forum Thread. The photos above and below show Lawrence’s stub gauges:

Barrel Stub Gauge

Permalink Bullets, Brass, Ammo, Gunsmithing, Reloading 3 Comments »
December 9th, 2011

NEW Caliber-Specific Laser Trainer Cartridges from LaserLyte

Here’s a clever product that provides visual feedback of your aim on the target while you dry-fire. LaserLyte, makers of laser pistol sights and bore-sighting tools, has come up with a smart new application of a miniature laser system. The new caliber-specific Laser Trainer Cartridge fits inside the pistol chamber and features a firing-pin activated switch that indicates bullet impact with a bright red laser dot. To practice, simply cock the hammer or striker, and pull the trigger as you would normally. When the firing pin hits the Laser Trainer Cartridge, a bright red laser displays on your target for 100 milliseconds. Available for 9mm, .40 S&W, and .45 ACP, the $99.95 (MSRP) Laser Training Cartridges are rimless so you can work the slide without ejecting the Laser Cartridges.

Laser Training Cartridge

With a Laser Trainer Cartridge in the chamber of your 9mm, .40 S&W, or .45 ACP pistol, you can practice your trigger pull and sight acquisition. But unlike traditional dry-firing, you can see your point of aim when you “break the shot”. This modified cartridge is rimless, so the Laser Trainer Cartridge is not expelled during dry fire, which allows for tap, rack, bang or malfunction training drills. A hardened rubber plunger on the laser also acts as a built-in snap cap to protect the firing pin. The Laser Trainer Cartridge requires three #377 batteries, good for approximately 3,000 shots. For more info on Laser Training Cartridges visit LaserLyte.com.

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Permalink - Videos, New Product, Shooting Skills 1 Comment »
December 4th, 2011

FREE Official Cartridge Diagrams on SAAMI Website

SAAMI, the Sporting Arms and Ammunition Manufacturers’ Institute, is an association of the nation’s leading manufacturers of firearms, ammunition and components. Founded in 1926, SAAMI promulgates industry standards for firearms ammunition safety, interchangeability, reliability and quality.

SAAMI Cartridge Diagrams

New SAAMI Website Offers Free, Printable Cartridge Diagrams
SAAMI recently rolled out a new website loaded with invaluable info for shooters. From the new SAAMI site you can access hundreds of FREE official cartridge diagrams and chamber drawings for all ammo types: Rimfire, Pistol Cartridges, Rifle Cartridges, and Shotshells. Are you looking for the official 17 HMR diagram, or 6.5 Creedmoor, or 7mm Winchester Short Magnum? You’ll find them all, along with hundreds more, on the SAAMI site. Said Rick Patterson, SAAMI’s managing director. “This redesigned website will help provide greater visibility and understanding of SAAMI’s important work.”

Please Read These Instructions Carefully
To access the diagrams, go to SAAMI’s Information & Specs webpage (sample above), and CLICK ON “Cartridge and Chamber Drawings” to reveal categories. Then click on a category: Rimfire, Pistol/Revolver, Rifle, or Shotshell. This will launch a PDF file in your browser (if you have the Adobe Acrobat extension installed). Once the PDF file loads, then put your mouse over a cartridge title (e.g. “6.5 Creedmoor”) and click. When you click the title, the official SAAMI chamber drawing for that cartridge will load. It may not be obvious, but Cartridge Titles in the list ARE hot-linked to the drawings. YOU MUST CLICK THE TITLE OF EACH CARTRIDGE to SEE the MATCHING DIAGRAM.

Below is a sample of the first page of the Rifle Cartridge Diagram List.
Red arrows show you where to click, after you launch that page.

SAAMI Cartridge Diagrams

SAAMI Standards Documents With Additional Info
You can also click the subcategory links under SAAMI/ANSI Standards to see multiple diagrams in a larger PDF file. You may have to click the SAAMI/ANSI standards line first to display the four sub-categories: Pistol/Revolver, Centerfire Rifle, Rimfire, and Shotshell.

Credit Boyd Allen for finding SAAMI’s Cartridge Diagram PDF Archive.

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Permalink - Articles, Bullets, Brass, Ammo, Gunsmithing 7 Comments »