SAAMI Velocity Data Question

[Brians356]

In SAAMI's published rifle data, when does it mean when they list more than one velocity for a particlular bullet weight?

For the large majority of cartridges, they list just one velocity for a particular bullet weight (at a particular Max Average Pressure or MAP).

But, for example, under 22-250, they list 2 velocities for both the 40-gr (3975 and 4125) and 50-gr (3800 and 4000) bullets.

Similarly, for 257 Roberts +P they list 2 velocities for 117-gr bullet (2760 and 2920).

Finally, under 270 Win they list 4 (!) velocities for 150-gr bullet (2830, 2925, 2950, and 3000).

In all cases the MAP for each bullet is constant, for example all 4 270 Win 150-gr velocities are shown at 65,000 PSI.

Anyone know how to interpret the multiple velocities?

http://saami.org/specifications_and...ons/download/Z299-4_ANSI-SAAMI_CFR.pdf#page=1
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[JPeelen]

In the 1992 standard, there was only one velocity (2830 fps) recommended for 150 gr 270 Winchester. This served as a recommended velocity. The aim was to give the buyer a cartridge of comparable power, whatever the brand name was. If his usual brand A was not available, he could buy brand B and have a cartridge of very similar performance.

Today, manufacturers try to set themselves apart from the competition at all cost. And new propellants allow better performance. The common performance figure is thrown overboard and every brand now has its "own" velocity. SAAMI is financed by the manufacturers. So it has no choice than to declare practically every "proprietary" new level of muzzle velocity produced by its members as "recommended." This way you end up with the examples you cite.

Basically it is a step backwards by one century, because this type of confusion existed at that time and one reason to found SAAMI was to achieve basic standardization to make life easier.

 

[mysticplayer]

So called high energy powders are offering a distinct VELOCITY increase for a given pressure rating.

SAAMI is concerned about velocity at a certain peak pressure over their test parameters. With new gen small kernel slow burn rate powders, it is possible to put more fuel into a given case which allows more energy to propel the bullet for a given pressure limit.

That's it. compare similar chemistry and dimensioned powders and you get comparable data.

Accuracy, that is a whole other story.

Jerry

 

[Brians356]

Ok, thanks. But more specific to my question, is SAAMI then just listing the velocities of commercial loads it knows about, without identifying them?
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[mysticplayer]

I doubt their lawyers would let them take other lawyers information as gospel.

But you can contact SAAMI and ask them directly.

Jerry

 

[Brians356]

I doubt their lawyers would let them take other lawyers information as gospel.

I meant they may list loads they know about and have tested, without identifying them.
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[JPeelen]

The first and foremost task of SAAMI is to remain neutral.

Important is its task to ensure common measurement procedures and limits for cartridge pressures as well as cartridge and barrel dimensions.
The recommended velocities are nice to know, but not really important. User safety depends on the pressure, not on velocities.