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)
Headspace 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.”
SUMMARY: Powder can have a very long shelf life. You need to watch for changes in smell and color. A reddish tinge, almost like rust on the powder, is a bad sign, as is a foul odor, not to be confused with a normal chemical smell. Either of these signs indicate it is time to dispose of your powder by means other than shooting.
Ever wondered about the stability of the propellants in your reloading room? There are some important things you should know about powder storage, to ensure consistent powder performance and safety. On its website, Western Powders (vendors of Accurate, Norma, and Ramshot powders) published an informative Q & A series entitled Dear Labby: Questions for our Ballistics Lab. Here are some excerpts that pertain to powder storage and shelf life. Worried that your powder may be too old? Western’s experts explain how to check your propellants for warning signs.
Proper Powder Storage
Q: I live in southern Arizona where it is very hot. I am told powders will become unstable if stored in an area not air-conditioned. My wife says no powder or primers in the house. Can powder be stored in a refrigerator? What about using a fireproof safe? I would appreciate your ideas. — M.C.
Lab Answer: SAAMI guidelines are pretty clear on issues of storage. They recommend storing smokeless powder in containers that will not allow pressure to build if the powder is ignited — ruling out gun safes and refrigerators.
In their original containers smokeless powder’s lifespan is quite long, even in your hot, arid climate, typically longer than the average handloader would need to store them. Stored safely in a garage or outbuilding, your powder should last years. If you see the powder developing a reddish tint, or giving off a foul odor, it is time to discard it.
Clumps in Powder Container
Q: I ordered some of your Accurate 1680 powder back about in December. I just now opened it … and it is full of clumps. My knowledge tells me that means moisture. Am I wrong? I just now broke the seal and it has been stored in a ammo can with desiccant packs around it and a dehumidifier running 14-16 hours a day. I can’t imagine this being my fault, if this does indicate moisture. I don’t know if the pink part on the label is suppose to be red or not, but it is definitely pink, so if it was red I am wondering if I was shipped an old container? I hope that this isn’t bad and I am stuck with it…
Lab Answer: All powder contains a certain amount of moisture. When the powder is stored or during shipping, it can go through temperature cycles. During the cycling, the moisture can be pulled to the surface and cause clumping. Clumping can also be caused by static electricity if too dry or the powder has limited graphite content. You can break up the clumps before metering and they shouldn’t be a problem. This will not affect the powder performance, so your product is fine. Accurate 1680 labels are designed in Pink. As a side note, specification for testing powder is at 70° F and 60% humidity.
Utah Monument photo by DOI. Inset graphic from Ammoland.com, DOI source.
U.S. Secretary of the Interior Ryan Zinke has announced the newly-appointed members of the Hunting and Shooting Sports Conservation Council (HSSCC). The Council, established on January 9, 2018, is intended to provide the Secretary of the Interior and the Secretary of Agriculture with advice regarding the establishment and implementation of existing and proposed policies and authorities with regard to wildlife and habitat conservation. The Advisory Council will meet at least twice a year.
The Council will also examine ways to benefit wildlife resources; encourage partnership among the public, the sporting conservation organizations, state, tribal, territorial, and federal government; and benefit recreational hunting and recreational shooting sports.
“We have assembled here some of the best conservationists in America,” Secretary Zinke said. “Over a century ago, Teddy Roosevelt established the American conservation ethic — best science, best practices, greatest good, longest term. These sportsmen carry on the American conservation ethic in the modern day. Bringing these experts together will be key to ensuring the American tradition of hunting and shooting, as well as the conservation benefits of these practices, carries on.”
Secretary Ryan Zinke (left) believes we can learn important conservation lessons from President Theodore Roosevelt (right), an avid hunter.
“America’s hunters and recreational shooters have a champion in Secretary Ryan Zinke,” said Chris W. Cox, executive director of the NRA’s Institute for Legislative Action. “Zinke is fighting for our sportsmen and women to have greater access to our public lands. I am pleased to work with the Trump Administration’s new Hunting and Shooting Sports Conservation Council to make it easier for Americans to enjoy our public lands.”
“Comprised of national leaders throughout the hunting and recreational shooting communities, the HSSCC is widely regarded as one of the most effective and productive federal advisory committees across the federal government,” said Lawrence Keane, NSSF Senior V.P. and General Counsel.
“What an exciting time for our hunting and shooting sports! This Shooting Sports Council is yet another way Secretary Zinke and staff is making the expansion of our great American heritage a priority,” said Smith & Wesson Pro Shooter Julie Golob.
“President Trump and Sec Zinke continue to make major positive structural changes to America’s land and wildlife conservation systems,” said Sportsmen for Fish and Wildlife Founder Don Peay. “This new Council, made up of the most accomplished hunter/conservationists in North America, will assist in revitalizing conservation of our nation’s natural treasures for generations!”
“I am very pleased and honored to be appointed to this Council by Secretary Zinke,” said Rocky Mountain Elk Foundation Chief Conservation Officer Blake Henning. “I look forward to representing the interests of big game and big game hunters as this Council does important work.”
“I am honored to be asked by Secretary Zinke to serve on the federal advisory council,” said Bob Model, Chairman of the Boone and Crockett Club. “Sportsmen and women are vital stakeholders in federal land management.”
Members of the Hunting and Shooting Sports Conservation Council are listed below
MEMBER NAME
ORGANIZATION
Mike Budzik
Retired Chief of the Ohio Department of Natural Resources
Chris Cox
Executive Director of the NRA’s Institute for Legislative Action (NRA-ILA)
Jeff Crane
President of Congressional Sportsmen’s Foundation (CSF)
John Devney
Vice President of U.S. Policy for Delta Waterfowl
Dan Forester
Vice President and Chief Conservation Officer, Archery Trade Association
Ward “Trig” French
Chairman of the Hunter’s Leadership Forum
Julie Golob
World and National Shooting Champion, Team Smith & Wesson
John Green
CEO of Crossroads Strategies and Board Member of the Congressional Sportsmen’s Foundation
Dale Hall
CEO of Ducks Unlimited and former Director of the USFWS
Blake Henning
Chief Conservation Officer for the Rocky Mountain Elk Foundation
Graham Hill
Principal and Founding Partner, Ice Miller Strategies LLC. NRA Board of Directors member
Larry Keane
Senior V.P. for Governmental and Public Affairs, Asst. Sec. and General Counsel for National Shooting Sports Foundation (NSSF); General Counsel, Sporting Arms and Ammunition Manufacturers Institutes (SAAMI)
Bob Model
Former President of the Boone & Crockett Club; President/CEO of Mule Deer Foundation; previous Deputy Director of Utah’s Div. of Wildlife Resources
Collin O’Mara
President and CEO of the National Wildlife Federation
Donald Peay
Founder and Former CEO of Sportsmen for Fish and Wildlife (SFW)
Eva Shockey
Co-Host of Jim Shockey’s Hunting Adventures on Outdoor Channel
David Spady
President of the Liberty and Property Rights Coalition
Do you know what the inside of a rifle chamber (and throat zone) really looks like? Do you understand the concept of headspace and why it’s important? If not, you should read the Brownells GunTech article Gauging Success – Minimum Headspace and Maximum COL. This article explains the basics of headspace and shows how to measure headspace (and length to lands) in your barrels with precision. The article also explains how to adjust your full-length sizing dies to “bump the shoulder” as needed.
Why is headspace important? The article explains: “Controlling headspace and setting proper C.O.L. also represent improved safety and reduced cost of handloading. Excessive headspace can cause case head separation and gases in excess of 60,000 PSI escaping from a rifle’s chamber. Too little headspace can result in a chamber forced bullet crimp and a bullet that becomes an obstruction more than a properly secured projectile. Excessive C.O.L. can result in a rifling-bound bullet, a condition that could result in spikes of excessive pressure.” [Editor’s NOTE: It is common for competitive benchrest shooters to seat bullets into the rifling. This can be done safely if you reduce your loads accordingly. With some bullets we often see best accuracy .010″ (or more) into the lands. However, this can generate more pressure than the same bullet seated .010″ away from initial lands contact. As with all reloading, start low and work up gradually.]
How is headspace specified? Most cartridges used within the United States are defined within ANSI/SAAMI Z299.3-4. Brownells explains: “In the case of the .243 Winchester, as an example, there are pressure specifications, cartridge drawings and, as pictured above, chamber drawings. Armed with a chamber drawing, each manufacturer producing a firearm for the .243 Winchester knows the proper standard dimension to cut chambers and set headspace. Notice there are two headspace reference dimensions for the chamber. The upper is a place in the chamber where the shoulder is .400″ in diameter; the “datum” or “basic” line. The lower is the 1.630″~1.640″ minimum – maximum dimension from the breech face (bolt face) to that point in the chamber that measures .400″.”
The actual headspace of any firearm is the distance from the breech face to the point in the chamber that is intended to prevent forward motion of a cartridge.
Looking for authentic U.S. Military Specification Standards (MIL-STD) for gun parts, safety products, or other hardware? Log on to EverySpec.com. This website provides FREE access to the complete archive of U.S. Government spec sheets and technical manuals. You can quickly access and download thousands of public domain U.S. Government documents. For example, we searched for “Picatinny” and came up with MIL-STD-1913 “Dimensioning of Accessory Mounting Rail for Small Arms Weapons”. With one click we downloaded the file as a PDF. Then a search for “M118″ yielded the engineering drawing for 7.62×51 M118 LR Match ammo. Pretty cool.
Using EverySpec.com is fast and easy. And everything you find and save is FREE. Search as often as you like — there are no limits on search requests or downloads. You can either search by keyword, or Federal Supply Class Code (FSC). CLICK HERE for a complete list of FSCs for all products.
Here are FSCs for a few common product types. Keep in mind that there are hundreds of other FSCs — for everything from Office Supplies (FSC 7510) to Nuclear Projectiles (FSC 1110).
1095 — Miscellaneous Weapons (incl. Knives) 1240 — Optical Sighting and Ranging Equipment 1395 — Miscellaneous Ammunition (incl. Small Arms) 3455 — Cutting Tools for Machine Tools 6140 — Batteries, Rechargeable 6230 — Electric Portable Lighting Equipment 7640 — Maps, Atlases, Charts and Globes 8340 — Tents and Tarpaulins 8405 — Outerwear, Mens
Credit Gunsmith Thomas ‘Speedy’ Gonzales for finding this resource. Thanks Speedy!
NOAA photo of flooding after Hurricane Floyd in 1999. The Colt Python Revolver once belonged to Elvis Presley (Rock Island Auction).
Firearms owners who have seen their guns and stored ammunition submerged by flood waters in storm-wracked areas are probably wondering if their firearms and ammunition can be salvaged and safely used. To answer these questions, the NSSF and the Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI®) created two documents outlining the proper response to submersion of guns and ammo. If you’ve got wet guns and/or ammo, download these two PDF files and read them carefully.
The SAAMI document “Guidance on Firearms That Have Been Submerged or Exposed to Extensive Amounts of Water” points out two major concerns about firearms that have been exposed to water: parts susceptible to moisture and rust damage such as metal parts, wood stocks and grips, and optics; and, secondly, infiltration of the action, barrel and safety systems by grit, silt and other foreign debris.
#1 Always unload firearms before beginning any treatment process.
It’s important to limit moisture and corrosion damage to the component parts of the firearm. This can be accomplished by disassembling the component parts and using up to two coats of a moisture-displacing lubricant such as Hoppes #9 MDL or WD-40 to clean and stabilize the parts while, importantly, following the product’s directions so as not to damage, for instance, plastic or synthetic parts. Another tip is to allow wood stocks and grips to air-dry and not be force dried by exposure to heat.
The document emphasizes that once the firearm has been thoroughly dried, consideration must be given to having the firearm inspected and serviced by the manufacturer, an authorized service center, or a qualified gunsmith before putting the firearm back in service.
Dealing with Ammunition That Was Submerged
Bottom Line, if your ammo has been submerged — DON’T USE IT. SAAMI explains why…
To help firearms owners determine what to do with ammunition that has been affected by water and moisture, SAAMI offers another helpful document, “Guidance on Ammunition That Has Been Submerged in Water.” This document covers differences in moisture resistance between centerfire, rimfire and shotshell ammunition, and potential hazards associated with “drying out” cartridges, including possible deterioration and damage to cartridges due to drying methods.
Another serious hazard that could result from using compromised ammunition is the potential for a bore obstruction due to partial ignition of either the priming compound or the propellant powder charge, or both. Firing a subsequent round through an obstructed barrel can result in bodily injury, death and property damage.
SAAMI provides the following cautionary conclusion: “It would be impossible to ascertain for certain the extent of the deteriorating affect, if any, the water may have had on each individual cartridge. Therefore, the safe answer is that no attempt be made to salvage or use submerged ammunition. The ammunition should be disposed of in a safe and responsible manner. Contact your local law enforcement agency for disposal instructions in your area.”
Here are five Peterson .308 Win casings after 32 loading/firing cycles (31 at SAAMI max). The brass remained intact, with no cracks. The circles below the shoulders are markings from pressure testing.
Recently Peterson’s ballistician had some extra time in his schedule, and asked what he should work on next. He was told, “Just for the heck of it, see how many times you can fire our .308s before you experience failure.” So that’s what he set out to do.
He took five casings out of inventory and loaded them at SAAMI max pressure, which is the pressure we use for all of our longevity testing. It is a hot load, and he did the firing out of Peterson’s Universal Receiver. This way he could measure pressures and velocities each shot. He shot all five, 20 times. (It takes a long time to do that. Load five casings. Shoot five times. Back into the lab to reload, back into the indoor range to shoot, back into the lab, and so forth.)
After 20 firings with no sign of case deterioration, Peterson’s tester asked if he should keep going. “Sure, let’s see how long these can go”, was the reply. So he shot them five more times. Same result. All casings still in good shape. We told him to keep going. He shot each of them six more times. At this point each of the five casings had been fired 31 times. After several days of this the casings were still in good shape but “ballistician fatigue” was setting in. Finally he said, “Let me take these cases to an outdoor range and see how they do for accuracy.” The Peterson team agreed.
Five Shots at 100 Yards after 32 Load Cycles:
For the 32nd firing, the cases were loaded with a somewhat lighter load, and then tested for accuracy. The test rifle was a Tikka T-3 bolt action, with a 20 inch, 1:11″-twist barrel. After 32 firings the primer pockets had opened about 0.002″ (two-thousandths) but were still tight enough for further use. There were no cracks or signs of head separation. The tester put five shots in three holes at 100 yards. The group was 1.5 inches for the five shots, on a somewhat windy day.
Story Tip by EdLongrange. We welcome reader submissions.
Planning a rimfire build in the future, or want to get the exact specifications for your 17 Mach 2, 17 HMR, 17 WSM, .22 LR, or .22 WMR rifle? Then we’ve got you covered. CLICK HERE to download an official SAAMI document with specs for all popular rimfire ammunition. This FREE 89-page PDF includes complete Cartridge and Chamber drawings and headspace specifications. The document even includes info on pressure terminology, headspace gauges, and test barrels.
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 offers diagrams for ALL popular, modern rimfire cartridges:
Here’s the Official SAAMI Drawing for the 17 HMR Cartridge:
SAAMI Website Also Offers Centerfire Cartridge and Shotshell Diagrams
From the SAAMI website you can also access hundreds of FREE official cartridge diagrams and chamber drawings for all centerfire ammo types and Shotshells. Click on the Cartridge and Chamber Drawings link, then go to the SAAMI Standards Page. On the Standards Page, choose your ammo type: Rimfire (Z299.1), Shotshell (Z299.2), Pistol and Revolver (Z299.3), Rifle (Z299.4). This will then load large PDF files which include multiple cartridge diagrams.
This important video shows what really happens when loaded ammunition burns. You will probably be surprised. Contrary to Hollywood notions, the ammo doesn’t ignite in a massive explosion. Far from it… basically the rounds “cook off” one by one, and the bullets release at relatively low velocity. We’ve featured this SAAMI research project before, but it is worth reprising for those who have not yet seen the burn tests.
A couple years back, SAAMI released an important video concerning ammo and fire. With professional fire-fighters standing by, over 400,000 rounds of ammo were incinerated in a series of eye-opening tests. If you haven’t had the chance to view this video yet, you should take the time to watch it now
The Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) has produced an amazing 25-minute video that shows what actually happens to sporting ammunition involved in a fire. This video shows the results of serious tests conducted with the assistance of professional fire crews. We strongly recommend you watch this video, all the way through. It dispels many myths, while demonstrating what really happens when ammunition is burned, dropped, or crushed.
Watch SAAMI Ammunition Testing Video
Video Timeline
2:10 Impact Test (ignited outside firearm)
3:40 65-foot Drop Test
5:08 Bullet Impact (.308 Win firing)
7:55 Blasting Cap Attacks
9:55 Bulldozer and Forklift Tests
12:20 Boxed Ammo Bonfire
15:37 Bonfire without Packaging
17:21 Retail Store Simulation Burn
20:55 Truck Trailer Burn
Over 400,000 rounds of ammunition were used in the tests. Some of the footage is quite remarkable. Testers built a bonfire with 28,000 rounds of boxed ammo soaked in diesel fuel. Then the testers loaded five pallets of ammo (250,000 rounds) in the back of a semi-truck, and torched it all using wood and paper fire-starting materials doused with diesel fuel.
The video shows that, when ammo boxes are set on fire, and ammunition does discharge, the bullet normally exits at low speed and low pressure. SAAMI states: “Smokeless powders must be confined to propel a projectile at high velocity. When not in a firearm, projectile velocities are extremely low.” At distances of 10 meters, bullets launched from “cooked-off” ammo would not penetrate the normal “turn-out gear” worn by fire-fighters.
We are not suggesting you disregard the risks of ammo “cooking off” in a fire, but you will learn the realities of the situation by watching the video. There are some amazing demonstrations — including a simulated retail store fire with 115,000 rounds of ammo in boxes. As cartridges cook off, it sounds like a battery of machine-guns, but projectiles did not penetrate the “store” walls, or even two layers of sheet-rock. The fire crew puts out the “store fire” easily in under 20 seconds, just using water.
Additional Testing: Drop Test, Projectile Test, Crush Test, Blasting Cap Test
Drop Test
The video also offers interesting ammo-handling tests. Boxes of ammo were dropped from a height of 65 feet. Only a tiny fraction of the cartridges discharged, and there was no chain-fire. SAAMI concludes: “When dropped from extreme heights (65 feet), sporting ammunition is unlikely to ignite. If a cartridge ignites, it does not propagate.”
Rifle Fire Test
SAAMI’s testers even tried to blow up boxes of ammunition with rifle fire. Boxes of loaded ammo were shot with .308 Win rounds from 65 yards. The video includes fascinating slow-motion footage showing rounds penetrating boxes of rifle cartridges, pistol ammo, and shotgun shells. Individual cartridges that were penetrated were destroyed, but adjacent cartridges suffered little damage, other than some powder leakage. SAAMI observed: “Most of the ammunition did not ignite. When a cartridge did ignite, there was no chain reaction.”
Bulldozer Crush Test
The test team also did an amazing “crush-test” using a Bulldozer. First boxes of loaded ammo, then loose piles of ammo, were crushed under the treads of a Bulldozer. A handful of rounds fired off, but again there was no chain-fire, and no large explosion. SAAMI observed: “Even in the most extreme conditions of compression and friction, sporting ammunition is unlikely to ignite. [If it does ignite when crushed] it does not propagate.”
Blasting Cap Test
Perhaps most amazingly, the testers were not able to get ammunition to chain-fire (detonate all at once), even when using blasting caps affixed directly to live primers. In the SAAMI test, a blasting cap was placed on the primer of a round housed in a large box of ammo. One cartridge ignited but the rest of the boxed ammo was relatively undamaged and there was no propagation.
Nosler has just introduced a new SAAMI-spec .338-caliber cartridge, the 33 Nosler, which is based on the 404 Jeffrey parent case. This efficient new cartridge rivals the velocity and energy of the proven .338 Lapua Magnum while using significantly less powder. AND, the Nosler 33 fits in a standard, long action receiver. Accordingly the 33 Nosler should be popular with extreme long range (ELR) shooters and big game hunters. The 33 Nosler fires .338-caliber bullets which are tough on big game and typically boast high Ballistic Coefficients and sectional densities. For long-range target work, Nosler will offer 33 Nosler match ammo with a high-BC 300gr bullet.
Notably, the 33 Nosler will fit in a standard-length Long Action. That’s a big deal because it means you can now achieve .338 LM performance in a rifle that is lighter and less costly to build. Nosler lists a 3.340″ COAL for the 33 Nosler. Compare that to 3.681″ for the .338 LM. Nosler will offer loaded ammunition as well as 33 Nosler brass.
The above chart was created by Nosler. It shows the 33 Nosler can push a 225gr AccuBond at 3025 fps and the 265gr AccuBond at 2775 fps. That’s 275 fps faster (with 20% more energy) than the .338 Winchester Magnum using the same length action. According to the chart, the 33 Nosler is also 25 fps faster than the .338 Lapua Magnum at the muzzle while burning 18% less powder. However, the numbers quoted by Nosler for the .338 LM are conservative.
The 33 Nosler® is SAAMI-standardized for consistent industry-wide brass and chamber dimensions. Nosler will be supporting this new cartridge with Nosler Brass, factory ammunition, and Nosler factory rifles. Expect 33 Nosler products to be available in early 2017.
Headspace Gauges
The Sporting Arms and Ammunition Manufacturers’ Institute (
We are not suggesting you disregard the risks of ammo “cooking off” in a fire, but you will learn the realities of the situation by watching the video. There are some amazing demonstrations — including a simulated retail store fire with 115,000 rounds of ammo in boxes. As cartridges cook off, it sounds like a battery of machine-guns, but projectiles did not penetrate the “store” walls, or even two layers of sheet-rock. The fire crew puts out the “store fire” easily in under 20 seconds, just using water.
