What is the length added to the barrel length to determine the over all length for a DPMS pattern 308 rifle?

Examples if I'm not being clear:
For my standard AR-15 lowers I add 18.75" to the barrel length to determine OAL. My 10.5" barreled 5.56 SBR has an OAL of 29.25".

For my pistol caliber lowers I add 17.75" to the barrel length to determine OAL. My 5.5" barreled 9MM SBR has an OAL of 23.25".


I plan on submitting the Form 1 for a 12.5" barreled 308 SBR (using an Aero M5 lower) but as you know the ATF won't let me assemble it to measure!

Just leave the stock at a buddies house and assemble your "pistol" lower and measure from the back of the buffer tube forward.

That's not a horrible idea, the whole SBR rules are silly (but the ATF doesn't think so). I know a lot of guys on this board have SBR 308s but it's Friday so they must all be out shooting them!

Read 109 times but not by anyone that has a 308 SBR!? I really didn't expect this to be that tough of a question, still looking for some dims!!!

SBR OAL is measured with the stock fully extended.

OP it's really not too critical to be perfectly accurate. Compare the length of the 308 receivers to the AR15 as well as the buffer tube and adjust as necessary.

If the receivers are 1'' longer and the buffer tube is standard, add 19.75'' to your barrel length.

Thanks for the response. I have 5 AR-15 based SBRs but wasn't too sure about the upper differences. I can easily measure the length difference between lowers but expected it to not be a direct correlation.

you should be right around 32.5"

I agree, I'm going to go with +20" to the 12.5" barrel. Now time to Form 1 and wait! Thanks again for the replies.