Seating depth or OAL

[paperwork351]

I had developed a load for the AR using IMI 55g FMJBT's that were actually m193'ish right in crimp groove and the OAL was 2.250. I switched to the Hornaday 55 FMJBT but kept the same OAL but below the groove (can't spel cannalure rite now). Ten years passed and I' starting to reload again. Can't get IMI now and OAL's seem to be 223'ish and around 2.220". I googled till my eyes fell out because no one really talks seating depth with their pet loads. So I'll ask the site I look at the most. What's y'all doing with your loads and any particular reason? Again, AR-15 20" barrel.

Thanks

 

[alucard0822]

I mostly use the Hornady 55gr FMJ, and load them to 2.220. The Hornadys have a pretty fat ogive and don't have to be seated that far out to engage the rifling quickly, crimping in the cannelure ahead of H335 and a CCI SR primer is my go-to bulk AR load

 

[Biggfoot44]

Haven't yet done a lot of work up for .223 yet, but with my lond distance handloading partner's prefered bullet ( 50gr Varmit Grenade) I settled on 2.23 OAL . It just seems fitting to have 2.23 for .223 .

 

[Half-cocked]

My COL using Hornady 55gr FMJBT's has been coming out to around 2.216", a few thousandths shorter than you guys because my trimmer has been cutting the cases a little bit short (1.747"), so I'm seating a little deeper to reach the canellure. I have shot a couple of hundred rounds at this COL with no problems.

 

[Fustercluck]

OAL in 223 only matters if you need to load them in factory AR magazines. The absolute longest the cartridge OAL can be, and still reliably fit in a magazine, is 2.260".
As long as the OAL is under that number, it doesn't really matter what your OAL is, within reason. There is no need to push the muzzle velocity of the 223 for plinking, tactical, or 3-gun use, as practical accuracy inside 200m will not be affected. So, with that said, you don't need to fill the case with powder and run the risk of compressed loads when you over-seat the bullet. Keeping the OAL between 2.22 and 2.25" is pretty safe when you keep the powder in the middle of the recommended loading range, and anywhere on the cannelure should be fine.

When reloading an AR for accuracy shooting, all the above advice is totally meaningless, and OAL will become one of several critical factors in maximizing the accuracy of your weapon. OAL for accurate AR loads will be in the 2.375-2.41" range, depending on bullet, which is way too long to fit in a magazine and requires single-load magazine followers, or sleds. At these lengths, the OAL is a rather meaningless number, as the tip of all these bullets will load at various lengths into the barrel. The shell base to bullet ogive becomes the critical measurement, and a bullet comparator becomes a necessary addition to your calipers in order to get the correct numbers.

I'm not sure what numbers you are looking for, but if you are, indeed, loading competitive accuracy, the above paragraph only scratches the surface of the Zen of accurate reloading.
D

 

[paperwork351]

Thanks for the info. I had determined where the lands started using the blackened bullet method which was around 2.260 if i did it correctly. That's what i load for the Sierra 69gr match. Since I don't check the "run-out", I was wondering about the increased bullet jump.

 

[Fustercluck]

2.260 is too short on a milspec AR chamber, using the sierra 69HPBT bullet. Let me be clear on that measurement: the distance from the case head (primer end) that contacts the breech face to the tip of the bullet (sierra 69) should be in the neighborhood of 2.400", plus or minus 0.002". The stony point (now Hornady) chamber OAL measurement tool is a cheap and accurate way of measuring this. Sinclair international also makes one (which I use). 2.4" on the sierra bullet will put it in contact with the leade of the barrel.

 

[paperwork351]

Thanks Fustercluck. That clears up the mental picture. I went back over my records and it was early after I got the rifle. I didn't pursue much after that. Shows how good that Sierra bullet is. I will stick to the published loads and hey, I get to do more development.