I'v been doing some load developement on my new AR15 Critter Getter and have been using WW748 powder which works good. I thought that since I load most of my 223 Rems with IMR 4198 I'd try that today. After shooting about 20 round loaded with the WW748 I switched over to the IMR 4198 powder loads. Out of 4 different loads with 50 grain bullets with 22.0 and 22.5 grs of powder there was not one that would cycle the action and chamber a new round. I thought that somrthing had gone wrong, so I switched back to the loads with 748 and everything was back to normal. Have any of you guys/gals run into this in your dealings with the AR? Are there some powders that just don't seem to work in the AR? At least now I know one powder that doesn't work (for me).

Yes, I am battling this problem too.  I was surprise to see someone else post the same problem as me !!!

I am still early in my testing and debugging, but I have a theory I feel good about.

Here is my theory.

I have been usin Vihtavuori 133, which is slightly faster than your 4198.  My theory is that the powder burning finishes too early in the cycle, and the pressure and recoil impulse have died-down too must by the time the bolt unlocks.  

Whereas a slower burning powder will be burning longer into the cycle, thus making more pressure and still producing recoil impulse by the time the bolt unlocks.

My theory also says that you can not add more powder (hotter load) of the fast powder to compensate because the higher pressure from the hotter load just causes the powder to have a even high burn rate due to the increased pressure.  So, the hotter load of fast powder still completes the burn too early.  

4198 is a relatively "fast" burning powder.  What's happening here is the gas port pressure is just not enough once the bullet reaches the port.  The available pressure is just not enough to reliably cycle the bolt/carrier assembly.  

The condition you describe happens most often in 20" barrelled guns.  CAR's, M4's or anything with the gas port set back will usually cycle OK with 4198.

I would recommend you use a slower powder such as H335, BL-C2, or Varget.

Pick up a bottle of Hodgdon H322 and try it out, too.  I'm getting outstanding results from the stuff.

CJ

I had a similar experience with different powders.  A bunch of loading tables I had made 2400 look like a good powder for .223.  For the AR, it's worthless crap.  I never could find a load that would reliably cycle the action.  I switched to BL-C(2) (aka WC846 in the military/surplus world) and have had no problems.  It just takes some experimentation and advice from others.

2400 burns faster than IMR 4198, which is faster than 748, which is slightly faster than BL-C(2), according to my Speer reloading manual.  H322 is between IMR 4198 and 748.  So it looks like [b]G35[/b] and [b]Russ4777[/b] are on the right track by leaning toward the slower powders.  From what I understand, BL-C(2) is mil-spec and pretty reliable for .223 / 5.56mm

I like Varget for my AR 15 reloads, works well with 55, 69, 70, 75, 77 & 80 gr loads. Use moderate loads per published info and you won't have any problems.

pwiz

748, BL-C2 and H335 are all very close to mil spec depending on load.  Win 844 and 846, both milspec, are available on the surplus market.  i have gotten very good results with 748.  IMR powders seem to burn very dirty in the AR.  ops

Thanks for the replys. My initial thread was to see if I was having bad results with 4198 or if it was not usable in the AR. I am relieved to find that I was not alone in thinking that 4198 doesn't word in ARs. I have been using 748 and H322 and have been getting good groups with 40 grain V-MAX and 50 Blitz bullets ignited with Rem 7 1/2 and Fed 205M primers. With only 350 rounds through this 24" V-Match I am quite happy with the results. I'll soon run the most accurate loads over the chronograph and see what is happening there. Winter's coming and I've got to get this thing ready for next year's crop of P-dogs and Rock Chucks.

Hi OutBack,
Not all .223 loads will work in the AR rifle.  Many loading manuals are not very good at making this clear.  The new Sierra Manual (Fifth Edition, I think) separates out .223 Bolt Action data from AR data.  Sierra also has a very informative chapter detailing reloading techniques for the "Service Rifle", including some recommendations regarding powder selection ( Varget, Vihta Vuori N135 & N140, and Reloader 15 being top choices). Hornady's fifth Edition has a separate listing for the 5.56 Nato round, but it's only data for the heavier Hornady bullets.  I don't remember seeing anything for 55 grain bullets.  Speer makes a 62 grain BTFMJ w/cannelure which is supposed to be the duplicate of the M855 military bullet, but then combines the data with .223 general data.  I strongly recommend buying a chronograph.  I've got a Gamma Master Chrony which I got from Sinclair International.  I've just started using it, but already I'm amazed at the information I'm gleaning.  I already can't understand how people can reload for semiautomatic firearms without one.
Coolio

Thanks, guys for your input. I have been working with H322 and 7 1/2 and 205M primers and am getting some GOOD results. I plan to go to the range Thursday and do some more testing. I hope to nail down it least one load before the weather settles in. Here in SE Idaho the snakes, ground squrells and rock chucks are already underground. This is my first AR 15 and I don't know why I waited 'till I was 65 to get one. I'm amased at the accuracy. What I have is a Bushy V-Match with 24" barrel. I do have a Chrony, but I want to get at least one good load and then I'll check the speed. I know what you mean thou about using a chrono while developing loads, but I'm doing it this way for now.