Confused about COL of Rem .223

[wwillson]

All,

I'm going to reload Rem .223 soon for my AR and don't understand the requirements for COL. The Hodgdon load manual says the COL is 2.200" with IMR-4064 and a 55g bullet. Does the COL mean that the overall length of the loaded cartridge MUST be 2.200"?

Thanks,

Wayne

[RLH70]

It means that that is a safe place to start for that particular load. You will likely need to adjust the COL to find the max accuracy in your rifle though.

[wwillson]

Would if be correct to say that you can seat the bullet with a COL equal to or longer than 2.200", but not shorter?

Wayne

[RLH70]

I would go no shorter than the listed COL for a particular load,or longer than the SAAMI max which is 2.260". If you go shorter you may experience feeding or more importantly pressure issues.

[JSharp]

The 2.200" they list is the reference length they used for their listed loads. As RHL70 said it should be a safe place to start if want to duplicate their loads and will likely also feed adequately in most weapons.

Generally, going shorter will increase pressures and might cause some feeding problems in some firearms. Conversely, going longer out to the maximum SAAMI length of 2.260 should reduce pressures and feed more readily.

A lot of people load longer, out to the maximum their magazines or their chambers will allow, whichever is shorter. This is especially common with long VLD bullets that long range shooters use.

In the end you'll have to figure out what works best in your rifle. Until you do, picking a length that's similar to what's used in your loading books and is under SAAMI maximum should be safe and usable in most guns.

[wwillson]

Thanks guys really appreciate the info...

Wayne

[Trapper]

The COL listed in the data is the COL that was used to develop that data only. Every gun is different and so will the achieved velocity and pressure. Some will run hotter, some won't get near the performance. All data that you see is guide, not an absolute. Always approach max loads with caution looking for signs of pressure on fired brass after each shot. As the internal capacity of a case gets smaller, the more critical the COL is when approaching max loads. An example would be a comparison of a 300 Win Mag versus a 9mm pistol case. You can move the 300 COL around the listed data and it will hardly effect the pressure even at max loads. The 9mm case is another issue. At max loads, seating a bullet another .010 deeper will probably raise pressure enough to be unsafe. Going shorter than the published data on a 223 case is only critical if you are shooting max loads and then it depends on the particular rifle. Some have longer throats which allows for the bullet to jump to the rifling and reduces pressure. Most often you'll find best accuracy with a powder that fills the case about 80%, using about 80% of max data and the bullet seating at max length. Once you have found a load that shows promise, dial in accuracy by adjusting COL in .005 increments.

[wwillson]

Trapper,

Great information - thank you!

Wayne

[Shannow]

Bear in mind that the ogive of the projectile and the chamber reamer affects how much "jump" to the rifling...go too long, with too rounded an ogive, and you can bump the rifling (unlikely in your case) increasing pressure at the other end.

Most of the serious reloaders that I know make up an overall length guage from an old case, drilled and tapped to take a fine brass thread, and push the projectile through until it touches the rifling...then back their loads off a little to give their desired jump.

Military chamberings are unlikely to ever have such an issue...my CZ527 I can put a 62 gr FMJ in BACKWARDS and not touch the rifling.

Still shoots fine, 'though.

[xtell]

Wayne,

Also, in addition to the ogive as mentioned previously, remember the overall length of the bullet you chose will have a bearing on the COL in your gun in regards to pressure. As an example, when loading for my 308 Win, the Nosler BT or Sierra Match King are longer overall than a Speer Hot Core or Winchester Power Point. If all are seated to the same COL, the Nosler or Sierra will have a higher cartridge pressure. If you can gauge how far off the lands your .223 loads are for best acuracy, without high pressure signs, and the finished loads fit your magazine and cycle smoothly, slight variations in the COL (less or more) are acceptable. It all becomes a balance between many different variables.

Xtell

[wwillson]

It all becomes a balance between many different variables.

Xtell,

You sure are right about that! I've been loading about 10% off max with 55g bullets out of my 24" 1 in 9 twist barrel. This gives about 3200fps, which is close to the limits on rotational velocity with the 55g bullets. I think I've seen a few come apart in mid-air because they sure didn't hit where I was looking.

Wayne

[xtell]

Wayne,

That 1 in 9 twist of your barrel is a good middle of the road twist rate for the .223 with 55 to 62 grain bullets. You would probably not have any trouble going up to the 70+ grain bullets if you ever chose to. Good luck and good shooting.

xtell

[wwillson]

xtell,

We're going to SD soon to shoot prairie dogs again. This time we're taking 6,000 rounds of .223 for 3 shooters..!! I hope we run out again... :-)

Wayne

[FNFAL308]

Hey Wayne~

Something to consider is yout MAX OAL in an AUTOLOADER is usually limited by the Mag.. With most bullets I doubt you could have an OAL long enough to engage the rifling and still have the round fit in the Mag.

If using bullets with a cannelure and properly trimmed cases your OAL is easy to figure. I don't crimp my .223 Ammo so I'm not too concerned by the position of the cannelure and just shoot for my usual OAL. which for me is a pretty standard 2.220"-2.250" depending on bullet weight.. Stretch this OAL out to 2.260 and you can expect feeding issues because of the mag..

This is why the heavy bullets (.223 heavy) are SINGLE loaded.

If your still looking for more info or data LMK, I have worked up some pretty impressive .223 data with a variety of bullets.

As to your 1:9 twist I can tell you most of my AR's are 1:9 Barrels and I have had excellent luck with weights ranging from 50-75 gr.

I hope your trip went well, 6K rounds should be enough to get your barrel hot that's fer sher..

[wwillson]

Thanks for the info. I loaded some 75g VLD's, which must be loaded one at a time, as you said. They are very accurate, but not that much fun to load. When I get this 100 shot up that it for those.

See this thread on PD shooting... http://www.practicallyshooting.com/forums/ubbthreads.php?ubb=showflat&Number=4958#Post4958