OAL question

[hamster]

I've reloaded 100 rounds of 155gr 308 rounds using bullets from Lapua making a OAL of 2.8". They shot fine. I've since bought some 155gr bullets from Sierra (cheaper) and the bullets are 0.254" shorter than the Lapua bullets. Does this mean my OAL is now 2.546" or is it still 2.8"? I looked on the Sierra website and couldn't find anything on what the OAL should be.

[bruceflinch]

If the bullets are the same shape the seating die doesn't care if the bullet is shorter. What are you measuring the OAL with?

I load .308's to the length of my particular chamber, not to mil spec, they're longer than the mil spec. I have the bullet seated to .010" off the barrel lands. Improves accuracy. I use a tool from Sinclair International to take the measurement.

[mattman]

You can make it shorter but never exceed 2.8. The bottom of the bullet will be in the same position at 2.546 with the Sierra and the longer Lapua which will lead to the same pressure. If you were to seat the bullet farther out you would end up increasing the case volume and changing your desired result. What powder are you using?

[hamster]

I'm using RL15, but I'm going to switch to Varget soon.

So if I understand correctly, I can leave it at 2.8 or create the same pressure by making the OAL to 2.546. If that's the case, what do you recommend?

[pdq_wizzard]

I'm using RL15, but I'm going to switch to Varget soon.

So if I understand correctly, I can leave it at 2.8 or create the same pressure by making the OAL to 2.546. If that's the case, what do you recommend?

OAL is a funny thing, it depends on the bullet you use.

just as an example

a 150 gr flat point and a 150gr speer point will have a big dif in OAL. just as you have found every bullet manufacture makes there bullets (of the same design) different.

you really need to find were the curve of the bullet (the first part of the bullet to hit the lands) hits the lands then backoff from there (at lest .010) until it shoots the way you want it. (never go under min OAL for said bullet)

the farther you are away from the lands the more pressure you get. but you get to close and that is bad too, I think .010 is as close to the lands as I would load.

[hamster]

OAL is a funny thing, it depends on the bullet you use.

just as an example

a 150 gr flat point and a 150gr speer point will have a big dif in OAL. just as you have found every bullet manufacture makes there bullets (of the same design) different.

you really need to find were the curve of the bullet (the first part of the bullet to hit the lands) hits the lands then backoff from there (at lest .010) until it shoots the way you want it. (never go under min OAL for said bullet)

the farther you are away from the lands the more pressure you get. but you get to close and that is bad too, I think .010 is as close to the lands as I would load.

So how do you know when your bullet is touching the lands of the barrel? Is that another tool I need to buy? Am I just safe leaving it at a 2.8" OAL? Seems like the more I know the more questions I have.

[WyoDuner]

So how do you know when your bullet is touching the lands of the barrel? Is that another tool I need to buy? Am I just safe leaving it at a 2.8" OAL? Seems like the more I know the more questions I have.

The easiest way is to buy an OAL gauge.

The poor mans method is to get properly trimmed piece of brass but do not resize it yet. What you want to do is just barely size the neck enough so that the bullet will stay in the neck but can be pushed in and out easily. Leave the bullet long - just inserted in the neck enough to hold it in place. Chamber this by hand gently and the bullet will be pushed back into the case. Pull the round out and measure the length. That is the length where your bullet just touches the lands. It takes a little trial and error with the neck tension but try it and you will see what I mean.

[Jonathan Doe]

I have never measured the OAL on my rifle cartridges. For gas guns, I load them to magazine length. For long range single load, I load it about .010" from the rifling. Good enough for me without a problem.