OAL for Different Bullets

[tkcomer]

OK, the OAL of the 223 is 2.260”. Why does Sierra recommend an OAL of 2.260” for their 69gr Match Kings and yet recommend an OAL of 2.250” for their 52gr Match Kings? I've noticed that they recommend a shorter OAL for the lighter bullets. Is it for neck tension?

 

[Big Nugget]

Just taking a hunch, but is it because of a shorter bullet length?

 

[tkcomer]

I can load the 52gr MK to 2.260" and the base is just below the case neck. Just wondering why Sierra recommends the 2.250" OAL.

 

[rfwobbly]

Maybe it's because that's where their canelure falls.

 

[tkcomer]

No cannelure on the MKs.

 

[mdi]

OAL is bullet specific. Case capacity and neck length will determine seating depth, so OAL will be different with each different bullet...

Jes my thoughts.

 

[rcmodel]

An OAL of 2.260” the the absolute max length that will function through an AR-15 magazine.

Seating a heavy / long boat-tail bullet deeper then that causes the base of the bullet to project inside the case, and use up available case capacity and lower how much velocity you can get at safe pressure.
It could also be that the end of the case neck would be hanging out over the bullet ogive at a much shorter length, leaving a gap.

The 53 grain is also a boat-tail, but the distance between the end of the BT and the start of the ogive is necessarily much shorter then it is on the 69 grain bullet.

So yes, you could say neck tension plays into it.
You want to:
Keep part of the full dia bullet bearing surface inside the case neck.
Keep the ogive curve out of the case neck.
Still fit in a magazine.
And keep the bullet base out of the powder charge.

rc

 

[918v]

Lighter bullets have shorter noses. Heavier bullets have longer noses. Lay them down side by side and compare their shank lengths and their nose lengths.

 

[tkcomer]

But as reloaders, we try to get the longest OAL we can for accuracy. Or in my case, the longest OAL that will fit in a magazine. Why would Sierra publish an OAL that's shorter than SAMI max? I understand bullet profile. I load for the 7.5x55 Swiss. A lot of bullet profiles can't be loaded to SAMI max because the bullets hit the lands of the barrel. That's not the case with the 52gr SMK.

 

[rcmodel]

But as reloaders, we try to get the longest OAL we can for accuracy.

No we don't.

Sometimes seating to the lands helps, and sometimes it doesn't.
And sometimes you can't if you wanted too.

I load all my .223 varmint & AR ammo to the standard military length of +/- 2.250" and shoot them in three different very accurate rifles.

I shudder to think I had to keep three different .223 OAL's separated for best accuracy in each rifle!

You might also notice that the most accurate factory ammo you can buy (Match & Varmint) is loaded to a standard length that will fit in any rifle.

And some of it is very very hard to beat with our handloads, no matter what OAL we use.

rc

 

[tkcomer]

So what your saying is Sierra has found the 2.250 OAL shoots best for that bullet. This is from their AR-15 section. I'm sure they know more than I do. And I know what ya mean by trying to load better than match ammo. So far, that's been no trouble in 308. The 223 has been hit and miss. I've always used the 69gr bullets. Trying out the 52gr bullets. That's the real reason I asked.

 

[918v]

Shoots best for that bullet in their firearm. Your firearm may prefer a different OAL. You should experiment with different OAL's to fine tune your load. The 2.250" is a good baseline.

 

[tkcomer]

My curiosity got the best of me. Dug up some 223 Black Hills Match ammo. The 52gr bullets measure from 2.187” (Shortest I found) to 2.207”. The 68gr bullets measure from 2.188” to 2.201”. Forgot I had these. OAL is all over the map. Just like my reloads. Though they are much more consistent with the new Redding comp die. Maybe I'm going about this all wrong. I guess Black Hills thinks shorter is better.

 

[Striker Fired]

take a measurement off the ogive not the tip and see if your measurments are that different.I made attachments for my calipers with a small holes(different size holes for different calibers) in them so when I measure my finished round, I measure to the same spot on the ogive and don't pay attention to actual oal(after I find what fits in my gun).The tips of bullets are usually dented or nicked and it takes almost nothing to make an oal seem .01 longer or shorter even though the ogive is in the same place.

 

[BADUNAME37]

The ogive, or taper of the forward section of projectile, has more to do with seating depth, i.e., distance from rifling, than the OAL.

The OAL is important in certain guns with magazines as it is desirable to be within specs so the finished cartridges will fit in the magazine and feed properly from the magazine into the chamber.

If you are loading each cartridge in the gun one-at-a-time, then OAL does not really matter, but rather the distance of the tapered forward portion (ogive) from the lands is what is typically measured.

 

[gamestalker]

OAL is bullet specific and thus varies from one bullet to the other. OAL is also specific to each chamber for most firearms, however, AL actions are not as flexable in this manner as would B.A.'s or other simular actions that allow for custom jump to lands seating. For AR's and other simular fuctioning firearms, just stick to what is published and what will feed and fit and you'll be OK.