COAL Tolerance?

[Jarhead]

+ or - .005 ok or too tight / loose?

[Enfield47]

For what? If it's blaster ammo it won't make a difference.

[thospb]

Measured to the tip or the Ogive? Tips get damaged and irregular. The Ogive is more consistent. Either way, .005" is not much effect on pressure, about the same as .05 grain of propellant.

[Jarhead]

Measuring to tip, so it what what would be maximum tolerance for COAL. There has to be a point where it affects performance. Shooting out of WWII style replica Sniper Rifles so they are not tack drivers but I want ammo to be as consistent as possible.

[allenj]

The only way to get true consistant OAL measurement is to measure from the cartridge base to the ogive. If you do not have the equipment to do that your best bet is to not exceed your maximum COAL and don't worry about those that are shorter.

[Jarhead]

Best tool to measure at ogive?

My targeted COAL is 3.115 and I'm getting 3.110 - 3.120 measuring at tip

[J-cat]

OAL variance is caused by two factors: bullet POS-ness and case POS-ness. In the former, the bullets are made using inconsistent length jackets, multiple lots are mixed together, etc. The bullets are wider or narrower at the seater stem contact point and that causes different seating depths. Usually, you can get mass produced match grade bullets to seat within .007" of one another. So, .010" is decent.

The latter factor is inconsistent case neck tension. The harder the bullet is to seat, the longer the OAL. If neck tension varies, so will the OAL.

[thospb]

Hornady offers an attachment for calipers, a complete set for most caliber is about $30 or you can get the individual pieces too. The difference you are measuring is just on the tip of the bullet, your seater die is pushing against the Ogive. For people who want each round to be perfect, they will modify the tip with a Meplat uniforming tool. I am not up to that level of perfection yet.

[Jarhead]

Just reloading for MilSurp right now, but want to learn the Art along the way

[J-cat]

So you're using 7.62 NATO brass?

[Jarhead]

This last batch was 7.92mm for my replica K98 snipers, but my next batch will 7.62 for my M40 and M40A1 and I will be using Lake City brass with either 168 match.

[J-cat]

Sort them by year. LC13 is very heavy and will throw off your OAL due to the additional neck tension.

[ElDub1950]

So, a varying OAL of .006 for generic 9mm, 115 Lead Bullets and mixed range brass, sounds like it's not unexpected?

Light loads, so not concerned. Just new at it and not sure what tolerance I should expect.

[J-cat]

If you are running mixed brass with max loads, then you are running excessive pressures in some of those cases.

[rcschummers]

Good stuff here, pressures because of decreased oal can be a serious issue if you are loaded to max.