How To Read A Saami Cartridge Drawing

SAAMI was founded in 1926 at the behest of the US government, with a charter to create standards, coordinate technical data, and promote firearms safety.

The Sporting Artillery and Armament Manufacturers' Institute (SAAMI, pronounced "Sammy") is an association of American firearms and armament manufacturers. SAAMI publishes various manufacture standards related to the field, including fire code, ammunition and bedchamber specifications, and acceptable bedchamber pressure.

Only manufacturers that are members of SAAMI are bound by the Institute's guidelines.

six.5×55mm maximum C.I.P. cartridge dimensions

SAAMI Committees

SAAMI's work is broken up in various committees each with a specific charter.

The Technical Commission does the master work of SAAMI. It is their job to set standards for ammunition and firearms. They interface with their European analogue C.I.P. to try to develop mutual, internationally recognized standards. The technical committee provides an industry glossary to facilitate amend communication.

The Logistics and Regulatory Affairs committee (also called SLARAC) is responsible for helping create transportation and store regulations. This is done mostly through educating people and agencies on safe practices.

They work with and are members of Dangerous Good Informational Council, International Gild of Explosive Engineers etc.

SAAMI Guidelines for Pulverization Storage (PDF)

The Environmental Committee works on science-based direction of ecology issues such as wildlife, conservation, and human health as they relate to products produced past SAAMI member companies.

Their goal is "A clean and salubrious ecosystem.

Legal and Legislative Affairs Commission tracks and lobbies for and against legislation, and works with regulatory agencies such every bit the ATF to correspond their fellow member's interests.

Internationally, accredited United Nations ECOSOC Non-Authorities System (NGO) with Consultative Condition. It is their job to exist a technical resource for various decision making groups inside the UN.

Conflicting industry standards (C.I.P)

Despite working together, the two main manufacture standards organizations SAAMI and C.I.P. have assigned different standards for some cartridges.

This leads to officially sanctioned alien differences between European and American armament and bedroom dimensions and maximum immune chamber pressures.

Some cartridges with possible chamber and ammunition dimensional conflicts, like to the dangerous combinations listed in a higher place, are listed in the Delta L problem article.

Proof test differences

Under SAAMI proof exam procedures, for bottlenecked cases the middle of the transducer is located .175 in (4.4 mm) behind the shoulder of the case for large bore (.250 in (6.4 mm)) transducers and .150 in (three.8 mm) for small diameter (.194 in (4.9 mm)) transducers.

For straight cases the middle of the transducer is located one-half of the transducer diameter plus .005 in (0.thirteen mm) backside the base of the seated bullet.

Small transducers are used when the case bore at the point of measurement is less than .35 in (8.9 mm).

Nether C.I.P. proof exam standards a drilled case is used and the piezo measuring device (transducer) will be positioned at a distance of 25 mm (0.98 in) from the breech face when the length of the cartridge case permits that, including limits.

When the length of the cartridge case is too brusk, force per unit area measurement will take place at a cartridge specific divers shorter distance from the breech face depending on the dimensions of the instance.

The departure in the location of the pressure measurement gives dissimilar results than the C.I.P. standard

Sporting Arms and Ammunition Manufacturers' Plant (SAAMI)

About loading manuals (including the Berger Manual), present loading information according to SAAMI (Sporting Artillery and Ammunition Manufacturers' Institute) standards.

SAAMI provides max pressure, COAL and many other specifications for commercial cartridges so that burglarize makers, ammo makers, and hand loaders can standardize their products so they all work together.

As we'll see later on in this article, these SAAMI standards are in many cases outdated and can dramatically restrict the performance potential of a cartridge.

Bullet seating depth is an important variable in the accuracy equation. In many cases, the SAAMI specified COAL is shorter than what a hand loader wants to load their rounds to for accuracy purposes.

In the case where a paw loader seats the bullets longer than SAAMI specified COAL, at that place are some internal ballistic effects that have place which are important to understand.

Effects of Seating Depth / COAL on Pressure and Velocity

The primary effect of loading a cartridge long is that it leaves more internal book inside the cartridge.

This extra internal volume has a well known result; for a given powder charge, in that location will be less pressure and less velocity produced because of the extra empty space. Another way to look at this is you lot have to use more than powder to achieve the same pressure and velocity when the bullet is seated out long.

When the bullet is seated farther out of the case, in that location is more volume available for powder. This enables the cartridge to generate higher muzzle velocity with the same pressure.

In fact, the actress pulverisation you lot can add to a cartridge with the bullet seated long will allow you lot to achieve greater velocity at the aforementioned pressure than a cartridge with a bullet seated short.

When you call back about information technology, information technology makes good sense. Afterward all, when you seat the bullet out longer and leave more than internal case volume for powder, you're finer making the cartridge into a bigger cartridge past increasing the size of the combustion sleeping accommodation. Effigy one illustrates the actress volume that's available for powder when the bullet is seated out long.

Before terminal that it'southward a good idea to start seating your bullets longer than SAAMI spec length, in that location are a few things to consider.

Geometry of a Bedchamber Throat

The bedchamber in a rifle will take a certain throat length which will dictate how long a bullet can be loaded. The throat is the forward portion of the sleeping room that has no rifling.

The portion of the bullet's bearing surface that projects out of the example occupies the throat

Bedroom throat geometry showing the bullet jump to the rifling or lands.

The length of the throat determines how much of the bullet tin can stick out of the case. When a cartridge is chambered and the bullet encounters the beginning of the rifling, known as the lands, it's met with hard resistance.

This COAL marks the maximum length that a bullet can be seated. When a bullet is seated out to contact the lands, its initial forrard motility during ignition is immediately resisted by an engraving force.

Seating a bullet against the lands causes pressures to be elevated noticeably higher than if the bullet were seated just a few thousandths of an inch off the lands.

A very common exercise in precision reloading is to constitute the COAL for a bullet that's seated to impact the lands.

This is a reference length that the paw loader works from when searching for the optimal seating depth for precision. Many times, the all-time seating depth is with the bullet touching or very near the lands.

However, in some rifles, the best seating depth might be 0.100″ or more than off the lands. This is simply a variable the paw loader uses to tune the precision of a burglarize.

Considerations for Magazine Feeding

When a hand loader is working to plant a seating depth to utilize with a particular bullet, he must decide if he needs the cartridges to feed thru a magazine or not.

Illustration of a bullet being seated out of the case also far to feed thru a mag

If the shooting application is hunting or tactical shooting, so the shooter probably needs the rounds to cycle thru the mag so the burglarize can exist used as a repeater.

However, in many deadening fire target shooting applications, it'south non necessary to magazine feed the cartridges.

Often times when a shooter doesn't demand to feed rounds thru a magazine, the shooter can take advantage of substantial functioning improvements by loading the bullets out long.

This brings up an important reality of seating depth and COAL.

SAAMI COAL Limits Ballistic Performance

It is a fact that the ballistic performance of modern ammunition is directly limited by the SAAMI COAL standards that are currently in place and that burglarize manufacturers build to.

Even when a shooter understands the implications of cartridge case volume and has a chamber that allows them to load the rounds out long, the rifle itself (having been congenital to feed SAAMI length cartridges) won't allow the shooter to do so.

This fact is one reason for the popularity of custom rifle builders who understand the importance of feeding longer than SAAMI length rounds and building rifles with long plenty deportment and magazines to cycle the rounds.

The first commercial rifle manufacturers who effigy this out and get-go building rifles capable of feeding longer rounds will atomic number 82 the mode into modern times.

There have been many improvements to several primal components of modern rifle armament, specifically bullets and powder.

It's unfortunate that many rifle makers proceed to adhere to the antiquated SAAMI limitations that were put in identify and so long agone when components were and then different, standards which limit the performance of modern potential.

Summary of COAL discussion

To epitomize the of import considerations regarding bullet seating depth as it relates to COAL, we can say:

Seating a long bullet to the restrictive SAAMI COAL can severely decrease the internal volume of the cartridge which will limit the max velocity the cartridge can achieve.
If magazine feeding is not a requirement (or if you lot have a longer than standard magazine) y'all can load your bullets long, which increases the volume for pulverisation and allows you to utilise more than powder and achieve faster MV for the same force per unit area.
If you load the bullet as well long and it encounters the lands, this tin can elevate pressure due to the engraving force resisting the bullets' initial forward movement.

Effects of Cartridge Over All Length (COAL) and Cartridge Base To Ogive (CBTO)

The kickoff half of this article focused on the importance of COAL in terms of SAAMI standards, magazine lengths, etc. There is another mensurate of length for loaded ammunition which is highly important to precision.

Chamber throat geometry showing the bullet spring to the rifling or lands.

Suppose the bullet was seated out of the case to the signal where the base of operations of the bullet's olfactory organ (ogive) just contacted the beginning of the riflings (the lands) when the commodities was airtight.

This bullet seating configuration is referred to as touching the lands, or touching the riflings and is a very of import measurement to understand for precision handloading.

Due to the complex dynamics of internal ballistics which happen in the glimmer of an centre, the distance a bullet moves out of the case before it engages the riflings is highly critical to precision potential .

Therefore, in order to systematically optimize the precision of his handloads, it'due south critically important that the precision handloader understands how to modify bullet seating depth in relation to the riflings.

Role of the required noesis is agreement how to accurately and repeatably measure the Cartridge Base To Ogive (CBTO) dimension, and furthermore how to communicate this dimension to other shooters. The following material will shed some light on the subtleties, and pitfalls of the various methods available for measuring CBTO.

Why non use CBTO equally a SAAMI standard?

If CBTO is then important to the precision capability of rifles, yous might enquire, "why is it not listed as the SAAMI spec standard in add-on to COAL?"

There is one primary reason why it is not listed in the standard. This is the lack of uniformity in bullet olfactory organ shapes and measuring devices used to determine CBTO.

Let'southward get-go by acknowledging the diverseness of bullet nose shapes. All noses are essentially a bend that is part of a larger circle. Y'all would recall this would brand nose shapes fairly consistent. The trouble is that the circular arc geometries are different for each bullet design. Fifty-fifty for a given bullet blueprint, tool making is non a precise plenty process to make these shapes precisely the same from tool to tool. Add to this the claiming of putting this curve on a surface that is round (similar a bullet). Doing this means that the size and location of the curve is influenced by the diameter of the bullet.

When your bullet seater touches the tip of 1 bullet, the distance to the betoken on the nose that engages the rifling is fixed. If your bullets have precisely the aforementioned nose curve and the aforementioned diameter and so your CBTO will be very uniform and should easily exist able to maintain a +/- .001 tolerance. This is achieved when using expert bullets, properly camfered example mouths, and a seater die that does not allow the bullet to lesser out (within the seater dice cone) on the tip of the bullet.

Ii different bullet shapes, seated to the same CBTO length, but unlike COAL. Note the shiny scratches on the bullets made by the comparator tool which indicates a betoken on the bullet ogive near where the ogive will appoint the riflings.

Measuring, Recording and Communicating CBTO

There is a vast lack of uniformity in comparators and measuring devices used to determine CBTO.

This is a disquisitional betoken to understand. To measure from the base of operations of the cartridge to where the bearing surface ends on the bullet you must apply a estimate that will attach to your calipers and which also goes over the olfactory organ of the bullet to touch the point where the begetting surface transitions into the nose curve.

We already sorted out that bullets tin and will vary in this area (at least from blazon to type if not lot to lot).

This makes it impossible for gauge manufacturers to use 1 given diameter and shape in there gauges. And so at that place is no standard shape and diameter for gauges. Said differently, gauges can and will vary in both within diameter and the shape where the gauge contacts the bullet.

There is some other reason why these gauges are not standardized. Since bullet olfactory organ shapes and diameters volition vary, judge manufacturers know that gauge standardization is impossible.

Since this is true the end result is that this measurement becomes a comparison used by one shooter rather than a consistent dimension used by many shooters.

Given this fact, they are gratis to open up their tolerances upwards from gauge to judge. Anyone who understands tooling knows that information technology is much cheaper to make a tool with a larger tolerance window.

Some of yous might be proverb, "Hold on a 2d, if the gauge tin vary and so how tin anyone employ CBTO successfully?"

The answers is because since this dimension cannot (or is non) standardized the specific CBTO dimension used by ane shooter is disquisitional merely this dimension is likely non to match the specific dimensions of a cartridge shot by another shooter.

"Huh?" y'all say? Let me explain.

If yous have one gauge and you lot are shooting ane lot of bullets, you lot have the ability to measure and suit CBTO to get the most performance out of your burglarize. All of the dimensions using your guess and bullets are meaningful to your rifle.

Testing to detect the best CBTO is a key function of getting the most precision from your burglarize and handloads.

For example, suppose that your CBTO using a 308 Winchester is 2.110".

Yous have this to the range and it shoots like a house a fire (shoots great). If you call your buddy up and tell him that he should try a CBTO of 2.110" in his rifle he volition be grateful until he goes to the range.

When your buddy who has a different rifle/bedroom, is using a different bullet (type or lot) and dissimilar approximate sets up his cartridge to have a CBTO of 2.110" he will await the same level of performance. Just his rifle doesn't shoot well at this CBTO dimension. You both are puzzled until yous try something.

You take your gauge and your bullets over to his house to find out what he has done incorrect. The outset thing you lot practice is you lot measure the CBTO of his ammo.

This is when you discover the kickoff problem.

His CBTO is 2.074". Only equally y'all start to requite him a hard time for getting it wrong he pulls out his estimate and measures his ammo again. When he does it with his gauge he gets 2.110". In this scenario, the difference is due to the fact that your gauges are not the same .

Trying to sort information technology out further, you determine to load some of your bullets into his cases with his seating dice fix exactly the same. Then you should be able to go the same measurement, correct?

You load 1 round and take a measurement. With your bullet at his seater die setting your CBTO is at 2.093". When he measures this cartridge with his gauge he gets ii.057". What the heck?

Now you both are all over the place. This second attempt to become things sorted out is thwarted by the fact that the olfactory organ shape of your bullets is different than the nose shape of his bullets. You both decide that this is a waste of time since the variation is and then much. How tin can something that varies so much be important to performance?

This elementary answer is that you have to apply it correctly and to your rifle using your own gauge and your own bullets .

The first pace is to establish the altitude from the commodities face up to the rifling.

How is this done? In that location are a two virtually common ways and neither is without difficulties. The about consequent and accurate fashion is to load a cartridge purposefully long using medium to calorie-free neck tension.

When you bedchamber the round and close the bolt the bullet gets pushed into the case.

If you slowly open the bolt and remove the cartridge information technology should be a representation of the distance from your commodities face to where the bearing surface of the bullet engages the rifling.

You lot need to practise this several times because with medium to light cervix tension the bullet may pull dorsum out of the neck if it is wedged too tightly into the lead angle of the rifling. If you practice this several times and come up with the same dimension (within .001) yous can call it good.

There are a few things you need to be aware of when using this method. It is important that you employ exactly the same bullet each time.

Not the same blazon of bullet or aforementioned lot simply the exact same bullet. If the cervix tension is calorie-free enough you should not change the shape when you pull information technology for another measurement.

Yous as well need to measure the COAL to make sure the bullet moved in the first identify. You lot may seat it long thinking that your throat couldn't be longer than this COAL but detect out that when yous do this check the bullet doesn't motion at all.

This indicates that either the bullet pulled dorsum out when you opened the commodities or the bullet was not out far plenty to touch the rifling. The more you lot do this check the better yous will become at doing it well.

The other common manner to get this dimension is to use the Stoney Betoken (or Hornady) Overall Length Guess.

This is a device that allows you to button a instance into a bedchamber that holds a bullet in the neck loosely. Subsequently the case is inside the chamber you push the bullet forward with a rod until it stops at the rifling.

Standard Chamber Specification

Copyright restrictions concerning intellectual material do not allow distribution of SAMMI and C.I.P. chamber drawings.
However access to their website drawing information and values of the dimensions is not restricted. The published values may be entered into the bedroom and cartridge records that are used in this software.

U.S. SAAMI Standards:

Click the link, and when the website opens, select the type of chamber and click on the quotient list to open up the cartridge and chamber data for that caliber.
To catechumen the inches to metric values, multiply each value past 25.four.

SAAMI Data and Specs

SAAMI Rimfire Cartridges

SAAMI Centerfire Pistol & Revolver Cartridges

SAAMI Centerfire Burglarize Cartridges

SAAMI Shotshell

European C.I.P. Standards:

Click the link, and when the webpage opens, go to the bottom right of the nautical chart to select one of several pages of calibers.

Select a caliber and, in the cavalcade labeled "TDCC", click on "EN" to view the bedchamber and cartridge drawings. To view the tolerances and other specs for the selected quotient, click on "EN" in the column titled "Annexe".

The C.I.P. Standard dimensions are listed every bit metric values.
To convert the metric values to inches, split up each value by 25.4.

C.I.P. Rimless cartridges

C.I.P. Rimmed Cartridges

C.I.P. Magnum Cartridges

C.I.P. Pistol & Revolver Cartridges