I recently started loading .223's for my AR. I've settled on 27.0g of W748 and 55g bullets of various manufacture.

After loading several batches, I finally got out the Chrony and checked velocities....and was surprised to see differences of up to 100fps for the same load. I've weighed the charges and checked the cases. The cases all are within 1.5g of each other, and the charges are within .1g.

I've been using WSR primers. Is this a case of needing magnum primers for the W748, or erroneous readings on the chrony? That's about all I can think of. Anybody got any other ideas?

Thanks.

org,

748 is a powder famous for velocity swings under many different conditions. How's the accuracy? If it's good I wouldn't lose sleep over it.

I have a .22-250 load (with another ball powder) that shoots really well out to 300 yards despite extreme spreads of 100+ fps. Go figure.

Redial

Hi ORG:

Not sure you have a problem. I've never loaded for a semi-auto so not sure if some of your measured variation could be due to gas bleed-off to cycle the action. I know I've read about changing the springs in ARs to slow the extraction for better accuracy. Seems as though this could affect velocity too. (?)

I've loaded about 6 lbs. of W748 the last two years and love it. I use CCI 400 primers. My 3 .223s all shoot very well with it, and it runs through a powder measure like water. I've Chrony'd a couple hundred loads and have seen variations in 5-shot strings of 78 fps with neck-turned, weighed cases. Have also seen 5-shot spreads of 10 fps.

Sounds to me like your loads are OK. If you don't already, get yourself a flash hole cleaner and use it; and double-check to make sure your case lengths are all under 1.760".

Let us know if you find anything. Good shooting ...

Thanks, fellows. The accuracy is pretty good (.6 to 1.0 inch at 100 yds, 1.5 to 2 inches at 200) with cheap Win 55PSP's, so I'm glad to hear it's not unusual to get the velocity variation. Generally, the velocities run around 2880 to 2930, with the occasional 3000fps. This from a 16" 1 in 9 twist.

My cases have all been resized and trimmed, so I guess I'll try the flash hole treatment, more because I'm stubborn than anything else:-)

Thanks for the info.

I had the same problem, only with WC844. Hand weighed everything on a digital scale.

The .223 is a fairly small case, which is one problem. The barrel of most .223's is on the short side, which also adds to the spread. A standard deviation of 35 fps is pretty normal under those circumstances. That means that 95% of your shots will be within plus or minus 70 fps, so a max spread of 100 fps is not out of line.

I would not worry too much about it. I have been using 748 with CCI mag primers and 40 gr V-max bullets with great accuracy around 1"-1.5" at 200 yds My bbl is a heavy 26" though. I've never gotten hung up over a larger SD if they still shot accurately

the best powder for the .223 is H335 as to velocity, and it has proven super accurate in my guns...Along with H322 for pure target work.

The first thing I would do is increase neck tension (either smaller expander button or smaller bushing). You can also increase neck tension by seating the bullet deeper.

If that doesn't do it, changing the primer might help, though I would not choose a magnum primer in a 223. As a matter of fact, I would go looking for a milder primer before I would go to a magnum. JMO, Dutch.