O.A.L. gauging .223 AR15 makes bullets to long for mag


December 4, 2008, 09:33 PM
I have a Bushmaster with a 24" shaw Bull Barrel and I also have the factory m4 upper that came with it as well. I just got a new Hornady curved O.A.L. Gauge and the .223 Modified Case to go with it. I used it on both with a 55 gr v-max and a 75 gr hpbt. both showed to be in the range of 2.358 to 2.360 O.A.L. wich is WAY to long to fit in any mag. and way longer then the 2.260 max shown in my Sierra reloading data book. Im thinking if I want to shoot a bullet thats been O.A.L. gauged Ill have to load one at a time and I dont have a problem with that because 99% of my shooting is benchrest. I shoot at ground hogs, hogs, and the dog food thieving grackle birds every now and then but not much. So either am I not using this thing right or am I right about having to shoot these one at a time because they wont fit in a mag but will be super accurate? any input would be very helpful

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December 4, 2008, 09:38 PM
There is no reason why you can't load a 55g bullet to a short enough OAL to fit in a magazine. Now it has been a while since I was dealing with this, but I think you can load 75g hollowpoints to magazine length also.

December 4, 2008, 10:01 PM
i think what you're trying to say is that you can't seat the bullets in the cases so that the bullet touches the lands when chambered. if so, that's pretty normal, especially for a gas gun. it's a liability issue for the mfgs and it would be very unusual for them to produce a gun that will allow factory bullets to touch the lands. it's just not safe.

odds are, you can get the gun to shoot just as good loading to magazine length as you can seating bullets into the lands.

if it's really bugging you, get a gunsmith to rebarrel it with a chamber more to your liking.

December 4, 2008, 10:09 PM
Lone Gunman, I know I can load them to any O.A.L. I normally size them to 2.260, but I got the O.A.L gauge so I can seat the bullet in the brass so that it is snug in the chamber (of the barrel im using at the time) and has as little travel from the cartidge case to the rifling as possible for improvment in accuracy.

December 4, 2008, 10:11 PM
any input would be very helpful

thats just not true.

if i were to tell you that rounds loaded to an o.a.l. of 2.358 will fit in your magazine vertically, it wouldnt be any help at all.

December 4, 2008, 10:31 PM
Well FlyinBryan I just tried that. and being that I use a 10 rnd clip, it still didnt fit. maybe I should just train a doodle bug to talk and have him go in my chamber with a tiny doodle bug retro fitted mic that you have to have hundreds of tiny little doodle bug arms to use, and have him mic it all out for me so ill know for sure what im working with. but the bullet in the mag vertical was, how should I put this, beyond genius.

December 4, 2008, 11:32 PM
lol, doodle bug

December 4, 2008, 11:35 PM
take it to work and bring it by 2morrow afternoon. i wanna see if mines the same or close

cracked butt
December 5, 2008, 08:13 AM
I would try them both ways, but I'm not sure that you are going to see great gains in accuracy. I'm inferring that you might be shooting Hornady 75gr HPBT bullets? If they are anything like the 75gr AMAX bullets, they were designed to shoot well seated to magazine length in an AR-15.

If you were shooting a heavier VLD bullet, then they do need to be seated on of close to the lands for the best accuracy.

December 5, 2008, 08:32 AM
I'm not exactly sure what kind of solution you are looking for. It looks like you have three options:

1. Make the rounds long enough to be barely off the lands and shoot them singly.

2. Make the rounds short enough to just barely fit in the magazine and not worry about distance to lands.

3. Have a custom barrel/chamber made so that both 1 and 2 happen at the same time.

December 5, 2008, 09:34 AM
5.56 chambers have longer throats than .223 chambers. a close to touching rifling load is likely more than spec OAL.

if you want to load that way a 223 chamber is the ticket, but same is a bad idea for nato spec ammo due to other dimensional differences.


PS----hate using wiki as a source, but i am pressed for time:

below from:


While the external case dimensions are very similar, the .223 Remington and 5.56x45mm differ in both maximum pressure and chamber shape. The maximum and mean pressures for some varieties of the 5.56 mm (different cartridge designations have different standards) exceed the SAAMI maximums for the .223 Remington, and the methods for measuring pressures differ between NATO and SAAMI.[2] The 5.56 mm chamber specification has also changed over time since its adoption, as the current military loading (NATO SS-109 or US M855) uses longer, heavier bullets than the original loading did. This has resulted in a lengthening of the throat in the 5.56 mm chamber. Thus, while .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, firing 5.56 mm ammunition in a .223 Remington chamber may produce pressures in excess of even the 5.56 mm specifications due to the shorter throat.

December 5, 2008, 11:45 AM
If you're using a normal magazine, you'll have to resign yourself to 2.260" OAL if you want to load multiple rounds.

There is a single-loading follower available for AR15 pattern magazines that permits longer OAL. You single-load the magazine after it is inserted into the lower receiver.

The Hornady 75g HP's are about the limit on magazine length compatible projectiles for .223 Rem.

December 6, 2008, 06:42 AM
Well, I guess your original post summed it up nicely:
1) Seat shy of the lands, and single load your rounds, or
2) Seat to magazine depth and work on other variables.

While not always the solution, sometimes the Lee FCD will assist in uniform starting pressures, or "pull." I have seen its use bring very mediocre groups on down to respectable size.

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