Factory Tolerances: Hey Danr (or anybody else)

[Elkgunner]

Do you know what the factories use for a tolerance on powder on the mass produced factory ammo?

Have you spent much time figuring out what is a reasonable tolerance for powder?

 

[MarvB]

Gunner, I know this isn't the direct answer you're looking for but it might lead you down the right road. I'm not sure what the individual mfg. specs are but, for our cops, we spec out the ammo for order by the following tolerances below- you might go to to the SAAMI site to see what they've established:


SPECIFICATIONS FOR NEW AND RELOADED AMMUNITION
1. New Ammunition shall be recently manufactured by an established, and recognized manufacturer that is a member of SAAMI.
2. Ammunition shall fully comply with the various applicable standards pertaining to safety, manufacturing tolerance, pressure level, velocity, and energy as jointly established by the American National Standards Institute (ANSI) and the Sporting Arms Ammunition Manufactures Institute (SAAMI), As follows:
• ANSI/SAANI Z 299.2-1982 Shot shell Ammunition
• ANSI/SAAMI Z 299.3-1984 Centerfire Pistol & Revolver Ammunition
• ANSI/SAAMI Z 299.4-1981 Centerfire Rifle Ammunition
3. Remanufactured/Reloaded ammunition shall meet the appropriate ANSI/SAAMI requirements.
4. Remanufactured/Reloaded, clean polished brass with no defects, military (scrap) and multi-fired brass is not acceptable, military surplus primers and powder are not acceptable, new or once fired commercial or military brass is acceptable, sizing and dimensions must be between minimum and maximum SAAMI specifications, primers must be proper.

 

[danr55]

Tolerance for what? Overall cartridge length? Bullet weight deviation? Powder charge deviation? Chamber pressure variation? There are all kinds of things that are measured on every lot of commercial ammo made. They all have tolerances. You have to ask a more specific question and I can give you a more specific answer.

...all of that being said, if you can keep the standard deviation of the velocity of a five shot string to under 15fps, you are doing OK. If you keep it under 10 fps, you are doing exceptional.

 

[Elkgunner]

Do you know what the factories use for a tolerance on powder on the mass produced factory ammo?

Have you spent much time figuring out what is a reasonable tolerance for powder?

Uh Danr..... I think I might have mentioned "powder" a couple of times in the original post....

Luckily Jose hasn't found this thread...

So, when I re-load, I generally only concern myself with one variable as it relates to powder on a cartridge by cartridge basis. And that variable is weight of the powder (or more correctly, mass of the powder). So my question was, when you are trickling charges of powder, what is the "tolerance" that the factories use? +/- .1 grain??? or bigger???


And to ask a follow-up, All other factors being the same, how much powder on a typical .308 load would equate to an additional 15fps?

 

[danr55]

WHen I am loading rifle rounds, +/- 0.1 grains is about what I look for. I tend to be a bit more relaxed with handgun rounds.

For your second question, I will say "it depends." Bullet weight, barrel length, powder burn rate, cartridge load density all count toward velcoity variation. It's hard to say specifically. The closer you get to maximum performance, the less velocity variation you see in relationship to powder charge weight, until you hit a critical point. THen everything goes to hell in a hurry. Frequently with the same powder charge weight, you will see more than 15 fps variation from round to round.