5.56 75 ELD-M - 2.26 COAL???

[MMH]

When loading a 75 gr. ELD-M to a 2.26 max COAL, the bullet sits deep in the case. 2.6 COAL obviously to get the round to fit in a magazine. The bullet would have to be seated to a COAL of 3.03 for the full bullet diameter to be is the case. Looks a little odd. Any issues with seating a bullet this deep?

Initially I seated the bullet to the same case to ogive length (1.820") that I used to load the Hornady 75 gr. BTHP, but this bullet would have a COAL of 2.23 seated like this.

Bullet jump will be BIG seated this deep - estimating 0.090", but if I don't seat this deep it will not fit in a mag.

What are the potential issues w/ deep seating?

 

[memilanuk]

You do know that bullet is not intended for gas-gun mag-length loads, right?

 

[CheapBasterd]

you want the 75gr BTHP Match for gas gun mags or 73gr ELDM.

 

[MMH]

You do know that bullet is not intended for gas-gun mag-length loads, right?

No, I did not realize that.. Understand why now. Looks like I have 900 bullets to sell now...

 

[MMH]

you want the 75gr BTHP Match for gas gun mags or 73gr ELDM.

I have been shooting the 75 BTHP for a while. It does not have the BC I needed to get out to 1000 yds,

 

[Doom]

The 5.56x45 Nato chamber was designed around the SS109 bullet (M855 Round) and the original 223/556 weapon magazine length over 40 years ago. There have been several cartridges designed more recently around the 224 caliber including the 224 Valkerie and the 22 Creedmoor that are designed around longer secent ogive and hybrid ogive bullets. Bullet weight can no longer be the guide to the proper selection of the proper bullet for a selected cartridge.

 

[MMH]

The 5.56x45 Nato chamber was designed around the SS109 bullet (M855 Round) and the original 223/556 weapon magazine length over 40 years ago. There have been several cartridges designed more recently around the 224 caliber including the 224 Valkerie and the 22 Creedmoor that are designed around longer secent ogive and hybrid ogive bullets. Bullet weight can no longer be the guide to the proper selection of the proper bullet for a selected cartridge.

I understand that the 5.56 cartridge was designed for shorter bullets.

What is the downside in me shooting the 75 ELD-M seated deep assuming that it will feed? It chambers feed from a magazine & dropping the bolt just fine. I admit I don't like the excessive bullet jump, but other than that, what is the downside?

 

[Basher]

Looks like I have 900 bullets to sell now...

Hell yeah you do, PM sent!

 

[supercorndogs]

I understand that the 5.56 cartridge was designed for shorter bullets.

What is the downside in me shooting the 75 ELD-M seated deep assuming that it will feed? It chambers feed from a magazine & dropping the bolt just fine. I admit I don't like the excessive bullet jump, but other than that, what is the downside?

The amount of bullet you have to stuff in the case eating powder capacity.

 

[918v]

I understand that the 5.56 cartridge was designed for shorter bullets.

What is the downside in me shooting the 75 ELD-M seated deep assuming that it will feed? It chambers feed from a magazine & dropping the bolt just fine. I admit I don't like the excessive bullet jump, but other than that, what is the downside?

Besides being mechanically incorrect, the already short neck of the 223 will not have adequate purchase on the bullet shank and accuracy will be shit.

 

[Doom]

I have been shooting the 75 BTHP for a while. It does not have the BC I needed to get out to 1000 yds,

There is a potential issue with the combustion process as you create an annular area between the case body and the bearing surface of the bullet that may not burn uniformly or consistently from shot to shot increasing the standard deviation from the shot.

There is nothing that says you can't do it. Hopefully you have a 24" barrel and will get the velocity that you will need. Be careful about checking for bullet setback on chambering (per 918v comment).

 

[MMH]

There is a potential issue with the combustion process as you create an annular area between the case body and the bearing surface of the bullet that may not burn uniformly or consistently from shot to shot increasing the standard deviation from the shot.

There is nothing that says you can't do it. Hopefully you have a 24" barrel and will get the velocity that you will need. Be careful about checking for bullet setback on chambering (per 918v comment).

You guys convinced me that doing this would not be a good idea.

My AR has a 22" barrel & that gets me out to 800 w/ a 75 gr. BTHP. Past that it falls off a cliff accuracy wise. JBM confirms that I will have issues past 800. I have a MV of 2850 FPS & use a G7 of .18 to get the dope to match up. At 1000 ft. elevation the JBM calculated velocity is 1187 fps (M=1.063).

 

[xsn10s]

When loading a 75 gr. ELD-M to a 2.26 max COAL, the bullet sits deep in the case. 2.6 COAL obviously to get the round to fit in a magazine. The bullet would have to be seated to a COAL of 3.03 for the full bullet diameter to be is the case. Looks a little odd. Any issues with seating a bullet this deep?

Initially I seated the bullet to the same case to ogive length (1.820") that I used to load the Hornady 75 gr. BTHP, but this bullet would have a COAL of 2.23 seated like this.

Bullet jump will be BIG seated this deep - estimating 0.090", but if I don't seat this deep it will not fit in a mag.

What are the potential issues w/ deep seating?

Here's a good thread on getting more COAL out of an AR15. All of it's pretty good but take special notice of post#15. https://www.snipershide.com/shooting/threads/longest-internal-length-ar-mags.6905874/

 

[xsn10s]

I've been using the modified stainless mags with a COAL of around 2.360". Or at least that's the COAL of the top of my head. It works in my Bushmaster lower due to the factory relief channel down the middle of the magwell.