Finding a good load for Win 748 in .223

[Leonidas24]

I happened upon a few pounds of Winchester 748 last year when my other favorite powders were in little supply. I decided to try to use up the 748 I had as opposed to the TAC that I normally use for training ammo. TAC's a little harder to get in quantity and I'm only able to find maybe a pound every two weeks or so.

I settled on a charge weight of 25.8 gr using a Hornady 55 gr FMJBT with a S&B SRM. Brass is usually Remington or PMC. I've been unable to chronograph this particular load but shot out of a 14.5" middy with an H2 buffer I was getting 2" groups at 100 yds and good reliability, but that was unsuppressed. Yesterday I took 250 rds of this load to the range to run some drills and do a little plate work between 50-100 yds standing. After all was said and done while shooting suppressed (Silencerco Saker) I had 7 feed ramp obstructions where the bolt slammed the round into the feed ramps, crushing the case and stopping the rifle. Clearance was accomplished by locking the bolt to the rear and removing the magazine. After a few of these stoppages I exchanged the H2 buffer for an H3 thinking the pressure curve of the Win 748 was doing something funky, but to no avail. The malfunctions continued intermittently until I was out of ammo.

With all that said, using the same bullet, brass, and primer but using 24.5 gr TAC, the rifle runs flawlessly using an H2 buffer, suppressed and unsuppressed. I still have over 4 lbs of 748 that I can load. Should I be looking at a higher or lower charge weight to shoot suppressed with?

[markm]

For 55 gr FMJs, I use 26.5 gr of W748. It gives me a nice, stout load that's in between .223 and 5.56 velocities.... about 3100 plus FPS out of a 20 inch AR.

[Leonidas24]

For 55 gr FMJs, I use 26.5 gr of W748. It gives me a nice, stout load that's in between .223 and 5.56 velocities.... about 3100 plus FPS out of a 20 inch AR.

I remember reading at one point that you used 26.0 gr a few years back. I'll see about working up into the charge range you mentioned to see if anything improves. Do you shoot this particular load suppressed?

[markm]

Man... I'm almost certain it was 26.5 grains. But I could be mistaken. I've used it a little suppressed. 748 is a nice, low flash powder that should be good for running suppressed.

[Leonidas24]

Man... I'm almost certain it was 26.5 grains. But I could be mistaken. I've used it a little suppressed. 748 is a nice, low flash powder that should be good for running suppressed.

It was 26.5 like you said. I found it in an old archived thread but I'm still somewhat in the dark here. Think the rifle is short stroking just enough to catch the back of the round and shove it forward? I was honestly thinking the gun was overgassed at this point.

[bigedp51]

I use the links below for load comparisons with the manuals, I also loaded 55 grain Hornady FMJ with up to 26.5 grains of 748 and from looking at the case and primers I think it is a mild load. The Hodgdon's manuals lists 26.3 grains of 748 with a 55 grian bullet as max with a bolt action rifle with a 1 in 12 twist at *39,000 cup meaning to me a short throated SAAMI chambered rifle. At the link below you will see a load of 27 grs of 748 or BallC2 for a 62grain bullet duplicating a military load.
NOTE: This information is from memory but I think Quickload lists 28 grains of 748 as max with a 55 grain bullet from a military chamber. My main computer is down and I can't run Quickload to verify this data, and all my practice ammunition is loaded conservatively and nowhere near max.

*The .223 and 5.56 are both loaded to the same chamber pressures listed below.
(The milspec for U.S. commercial contract 5.56 ammunition made for the military is listed below as 52,000 cup and 55,000 psi.)
52,000 cup, copper crusher method SAAMI
55,000 psi, transducer method SAAMI
62,000 psi, transducer method European CIP EPVAT pressure testing at the case mouth. (American SAAMI method is pressure taking at the mid point of the case)
"ALL" three pressures above are exactly the same chamber pressure and just measured three different ways.

Duplicating NATO cartridges (cloning) This main page will take you to other loading information.
http://www.223reloads.com/home/223-5-56-info/223-5-56-reloading/duplicatingnato

The only way to double check this data is with a chronograph and compare with military velocities. But your port pressures will be higher with slower burning powders and this will effect ejection.
Also a ballpark method for checking pressure is brass flowing into the ejector and case head swipes. Meaning you have exceeded the elastic limits of the brass and the high pressure caused the brass to flow.

At the top of the page below base expansion is also used as a sign of pressure, BUT not all .223 cases have the same hardness in the base web area with Remington and Federal having the softest brass. If the base expands over .001 after firing your are getting warm and anything over this and you will start getting loose primer pockets. So just as the reloading manuals tell you start low and work up your loads with YOUR rifle and the components used.

55gr 223 loads
http://www.223reloads.com/home/223-5-56-info/223-5-56-reloading/55gr-reload-info

To confuse the issue further my Savage .223 bolt action has a longer throat than either of my AR15 rifles and can be loaded warmer. And the various .223/5.56 chambers do effect max pressure.

[colt933]

For 55 gr FMJs, I use 26.5 gr of W748. It gives me a nice, stout load that's in between .223 and 5.56 velocities.... about 3100 plus FPS out of a 20 inch AR.

This is my load also, in LC brass. 2 MOA easily in a good rifle with a 5.56 chamber. I don't think it's particularly hot.

[markm]

This is my load also, in LC brass. 2 MOA easily in a good rifle with a 5.56 chamber. I don't think it's particularly hot.

It's just perfect. Hotter than most .223, but not abusive to the gun or brass.... just a 100ish fps under M193.