Oal 5.56/223

[Henry45]

Hey folks, i'm setting up my new Dillon for 5.56. I'm using M193 55g bullets (pulls) and am wondering about OAL.

My books range around 2.20. But, all the M193 Lake City I measure are 2.250.

All the LC fires fine in my AR. If I set my OAL to 2.250, will that be pretty close for all the M193 bullets?

I know if i use Hornady 2266 or 2267 I need to set OAL to what the manual state (2.20).

This is my first run on rifle reloading, and don't understand why all the fluctuation in OAL's.

Thanks..

 

[rcmodel]

The book OAL is not set in stone.

That is just the length they tested them at.

Mil-Spec 5.56 ammo runs on average 2.247" OAL.

But you just need to set your OAL to the bullet cannulure on the bullets you are using as if you were going to crimp them.

Whatever that turns out to be is the correct OAL for that bullet.

rc

 

[Fired]

You'll be fine at 2.20 or 2.250, make sure the cases are trimmed to correct length.

If oal is set too long cartridge might not fit the magazine. If too short pressure rises in case.

From wiki
The overall length of an ammunition cartridge is a measurement from the base of the brass shell casing to the tip of the bullet, seated into the brass casing.[1]

Handloaded cartridges and commercially available cartridges for firearms are normally created with a maximum length standardized by the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI). A cartridge's overall length may be shorter than the maximum standard, equal to the standard, or sometimes even longer.

The maximum overall length is dictated by the need to fit into a box magazine of standard manufacture. For example, the .223 Remington cartridge, when loaded for use in the AR-15 rifle (or the military's M-16 rifle), has to fit into the removable box magazine for that rifle. This dictates that the cartridge's maximum overall length be no greater than 2.260". However, for competition purposes during off-hand and slow fire prone match stages, the .223 Remington is loaded one cartridge at a time into the rifle's receiver. This allows for the cartridge to be longer than the standardized 2.260" SAAMI maximum overall length. These cartridges can be safely loaded to a length that has the ogive portion of the bullet just touching the rifle's lands. Many competitive shooters will make these cartridges 0.005" less than the truly maximum allowable overall length, for the sake of safety.[2]

It is desirable for these single-loaded cartridges to have as little bullet jump as possible before the bullet's ogive begins to be engraved by the rifle's lands. This minimized bullet jump increases the accuracy of the rifle, all else being equal. This practice of long-loading a cartridge must be adjusted for each individual rifle, since there are variations from rifle to rifle as to how far down the barrel the rifling begins.[2]

 

[Henry45]

So, if I set the OAL to fit.. say,,, in the center of the cannalure, that should be ok? As long as the OAL doesn't exceed the specs for the certain rounds?

 

[rcmodel]

Zactly.

MAX OAL for the .223 is 2.260".

I'd stay around 2.250" to insure free movement in the magazine and more reliable functioning.

rc

 

[Henry45]

Thanks RC...

 

[rg1]

Hornady's 55 fmj has a blunt rounded bullet tip. Most military style 55 fmj's have a long very sharply pointed tip. Hornady's rounded tip makes the oal shorter and seating for them is usually 2.200-2.230". The sharp pointed M193 55 fmj's normally are seated to 2.250".

 

[Walkalong]

Like rcmodel posted, load them to the cannelure and call it good.

 

[KansasSasquatch]

I trim my once fired brass to 1.752" and typically use some sort of Hornady 55gr bullet, then seat them to the middle of the cannelure. If a piece of brass gets trimmed a little shorter or a little longer (within 3-4 thousandths either way) it will still crimp in the cannelure. My OAL typically comes out to 2.190" with the Hornady bullets I use. You'll be fine with 2.20".

 

[Hondo 60]

So, if I set the OAL to fit.. say,,, in the center of the cannalure, that should be ok? As long as the OAL doesn't exceed the specs for the certain rounds?

Yup, that should be just fine.

 

[helotaxi]

If too short pressure rises in case.

In a rifle the point where pressures increase from deeper bullet seating reducing case capacity almost always has the ogive of the bullet in the case mouth. The difference in bullet-to-lands distance is what controls the pressure spike and max pressure in a rifle. This is dictated by the relatively small bullet diameter to case volume ratio, the high engraving force on a rifle bullet and the relatively slow burning powder used in rifle loads.

As usual, Wikipedia proves to be inaccurate and/or incomplete. Some of the generalized statements in your quote there hint at truth but are stated in terms that makes them misleading. The last paragraph tries to sound so definitive but is speaking in general terms and as such comes up lacking. The reality is every rifle and bullet combo has a "jump-to-lands" distance that works best. While one rifle might work best with the bullet jammed in the lands, another might like the same bullet with a jump of 0.005" and yet another the same bullet with a jump of 0.015" or so. Stating unequivically that "as little bullet jump as possible" is "desirable" is not accurate unless you are talking about a particular rifle with a particular bullet.

 

[steve4102]

If oal is set too long cartridge might not fit the magazine. If too short pressure rises in case.

In straight walled pistol rounds, yes. In bottle necked rifle rounds, not so much. In fact reducing OAL decreases pressure the farther the bullet gets from the lands.

 

[helotaxi]

In fact reducing OAL decreases pressure the farther the bullet gets from the lands.

To a point. That point varies with the particular cartridge and is usually ends up with the bullet mostly inside the case. Stating it as an absolute is inaccurate, but within the reasonable range of bullet seating depths, it makes a good rule of thumb.

 

[Henry45]

I came across with something unusual... Or seems to me to be. I'm loading some Everglades Ammo 223/556 bullets. They are like the Hornadys, with the round nose.

My OAL is 2.20. It seats the bullet just to the top of the cannalure with a case length of 1.750.

So, I picked up a M193 pull just to see what it would do... (Sharp nose military pull). It seated to a OAL of 2.250 with the case length at 1.75, but was barely in the cannalure.

Seemed odd, that without any adjustment on the seating die, a RN bullet seats OAL at 2.20, and a sharp nose M193 seats at 2.250, exactly like my manual shows... Tried several, and they came out the same....

Coincidence????

 

[KansasSasquatch]

That's just a result of the seating die contacting the bullet on a different spot due to the differing shapes of the bullets.

 

[Magnum Mike]

As someone mentioned, the OAL is not set in stone, one factor to take into consideration is the barrel's throat wear, which is the distance the bullet has to travel before it contacts the riflings in the barrel, the more travel the less the accuracy and that usually happens when the barrel has had excessive wear. For any caliber I load, I usually push the bullet I load into the end of the chamber, into the beginning of grooves, then run a cleaning rod with a brass tip into the barrel from the muzzle, use a felt marker to mark the point where the cleaning rod stops. Push the bullet out with the cleaning rod, put the bolt into the chamber and lock it, run the cleaning rod into the barrel from the muzzle again until it stops, then use the felt marker again to mark the spot on the cleaning rod at the end of the barrel. The distance between the two marks on the cleaning rod, minus roughly .07" would be the ideal overall cartridge length for that particular bullet.

I've been doing that for years and I've had excellent accuracy on the rifle rounds, from the .223 Remington in my AR-15, to my .300 Winchester Magnum.