Fantastic! Let’s make a sticky out of this, assuming we get some good info of course:D WTF? My time stamp is still off!
What have others used? Whats worked for you? Trying to get an idea of where to start.
Powders, Primers, Bullets. What have you tried thats comes close to XM193 loads?
I cannot give exact details. My elevation, climate, lot of powder, etc are all different than yours, and I was not exactly trying to reach XM193 performance.
However, my understanding is that the mil ammo uses WC844 powder. This is a surplus powder (see Pat’s Reloading – google is your friend). It is a non-canister grade which means that it can vary a lot from lot-to-lot. It is roughly similar to H335. Again, it is not canister grade and you cannot necessarily use H335 data straight across. Usually the people you buy this stuff from have some sample data to get you started.
Having said that, using both IMI 55gr and PRVI 55gr slugs, I was loading this powder (in the WC844T variant) and running it across a chronograph, I had near 193 velocities, but not quite, out of my 16" barrel M4 type gun. I saw no noticeable difference between the IMI and PRVI slugs and would guess you would get similar results with any normal 55gr FMJ like PRVI or Hornady (the IMI I bought back 15 years ago and have some left – they were $240/8000 delivered back then from Wideners). I used Wolf small rifle magnum as well as some CCI small rifle or small rifle magnum primers. Again, I did not notice any great differences with both kinds of primers. I was not going for ultimate accuracy or smallest deviations so there could have been some small deviation but it was within my needs of practice ammo. I used mixed cases.
I started with the data that came from the provider of my WC844T and worked up from there
I would also search this site and other loading sites for 55gr loading data and see what powders and stuff people are using. There is lot of 55gr data out there.
Then work up loads using your components, powder lot, and for your location.
Somewhere between 23.5 and 24.9 of AA2230 will get you near XM193 velocities over a 55gr FMJBT.
Things to know:
All small rifle primers are NOT equal. You have to use Remington 7 1/2s, CCI 450s, CCI #41, or Winchester Small Rifle Magnum primers, or you take the risk of perforating the primer and blowing your ass up.
Remington 6 1/2s are NOT SAFE for .223/5.56, and any of the standard (not Magnum) small rifle primers are asking for trouble, especially when you start pushing 5.56 pressures. The best ones to get are the CCI #41 arsenal primers, as the cup is very thick.
I had heard that before on the primers. I believe I have Winchester Small Rifle Magnum, but I need to verify
I have Remington 7 1/2’s and some CCI 450’s. More so of the Rem 7 1/2’s.
Also have AA2230 that Im gonna give a try.
I’ve been trying to work up a “close to” XM193 load myself. I’m using TAC and either PMC, LC or WCC cases. I get about 50 FPS more from the random LC cases I used as compared to the PMC cases. With CCI#41’s, 25.5gr TAC and LC cases I’m at about 2930 FPS, same load in a PMC case and I’m at 2870 FPS (temp approx 50 degrees F). The PMC case/load clocked 2980 FPS on an approximately 80 degree F day from the same rifle. I thought TAC was supposed to be more temperature insensitive than that - I have a 5.56 chamber (Ned Christensen took care of that detail). As a comparison, this particular 16" AR gets about 3100 FPS out of XM193 and about 2960 FPS out of Q3131A.
I have noticed a somewhat significant difference in small rifle primers. I try to use CCI#41 whenever possible, but I recently bought some of the “WOLF223” primers from Wideners. They said they were slightly hotter than the Wolf Magnum primers. I chronographed some through my 16" AR and got about 100 FPS less with the WOLF223 primer vs the CCI#41 with everything else being the same. I’ve had the same kind of differences appear when changing brands of case.
As for primer cup thickness, this guy seems to have a good list part way down this page (source is listed as “calhoun”, I don’t know who that is):
http://www.radomski.us/njhp/cart_tech.htm
Handily, the CCI#41 is not listed.
Overall, trying to reproduce the XM193 has been trying to say the least. I don’t have a good place to regularly test loads so development has been slow. With TAC I don’t have much hope of really getting there safely. 
While I have some TAC, I have not used it. But supposedly real M193 uses WC844 which is a faster powder than TAC I believe. I would try X-TERMINATOR or whatever the western powder is that is slightly faster than TAC. Or try H335 or similar. (H335 is supposedly the closest canister grade commercial powder to WC844). I would guess (and this is a WAG) that you are getting a more incomplete burn than you would with a slightly faster powder.
I also failed to mention that my cases come out quite dirty. The Q3131A and XM193 come out much cleaner - could be the incomplete burn you speak of. I’m pretty sure I don’t have low pressure problems with the amount of powder I’m using. I had problems with this carbine early on in that it was ripping rims from the cases. It had the standard carbine buffer. Changing to H2 buffer has mostly fixed that. I think that it is overgassed based on the gas port diameter I measured. I’ve thought about putting in a manifold, but I don’t want one more thing to be able to break or lose a set screw!
Well, if you are getting a more incomplete burn than other things that would, using my simple mind to think it through, probably mean a slower pressure curve or a lower pressure than you otherwise think you should have.
Dirty cases are one sign of a more incomplete burn but there are other reasons for that as well.
Also, smokeless powder requires high pressure to burn well (relatively speaking). Different powders have different requirements. If you had a crappy burn it could not be reaching peak pressure which contributes to the crappy burn. If that makes sense.
I am not an expert at this (while I have been doing it a long time and sell the presses etc I am not an expert on the mechanics of what happens inside the cartridge) and don’t have all the fancy equipment to measure these things so I would welcome informed correction.
I appreciate your input!
I’d be happy with Q3131A performance in this gun since this is mostly practice ammo. 
Just using random cases, I’m getting ~2800FPS using 25.4gr of H335 from a 10.5" barrel. That’s faster than the M193 I’ve chronoed.
The problem is finding H335 in stock any where haha
Very true. Over the last few weeks I’ve seen them pop up ever so often, however.
our local Cabelas had a few 1lb containers of it the other night. You just need to look everywhere and often. Our sportsmans warehouse also has powder on the shelves. The assortment changes everytime I am there but they have it coming in.
I use Benchmark, Varget and 335. That is also my ranking of these powders for myself. I cannot find Benchmark or 335 in my neck of the woods. Bought 8#'s Varget locally. Extremely high volume powder. I am getting 3120±fps out of a 16in 1/7 barrel. The case is full to achieve this. But not over max. Plus I’m using magnum primers. I had some flattening of primers when I pushed the Benchmark loads with mag primers. But that’s really not uncommon in 556.