I am having a problem of FTE/FTF with Lot 13 XM193 from Natchez.  I bought a new JT kit (16” standard HBAR, non-chrome lined), and have test-fired several types of surplus ammo through it after break-in to see what worked the best.  I shot 50 rounds of each ammo in ten round groups, random order.  Here are the results:

Round 1
Winchester White Box 55g FMJ(no problems)
Federal Lake City XM193 lot 13 (2 shots - FTE, 3 more shots-FTF, last 5 shots cycled fine)
Wolf 55g FMJ (no problems, just dirty)
UltraMax 55g FMJ (no problems)

Rounds 2-5
I changed the firing order around on the ammo, but every time I came to a mag with XM193 my rifle would jam/FTF/FTE at least twice during the 10 rounds.  BTW, I thoroughly cleaned the rifle before round 3 and fired the XM193 right after this cleaning with similar FTE/FTF results.

It (the rifle) acts like the XM193 rounds are not returning enough gas to cycle the action and eject the spent shell.  In almost all of the cases, the spent casings were halfway out of the chamber or just sitting on top of the magazine well blocking the action with a new shell behind/beneath it trying to chamber, like they just about made it out (ejected), but ran out of steam.

Has anyone experienced a similar problem with this ammo or can lend me some advice?  If it happened with the other types of ammo I would make the assumption I was having a gas port/tube problem on the rifle, but it is not. I was really surprised.  None of these are “match-grade” rounds, but of all of them I would have bet money the XM193 would have performed the best.  Any thoughts &/or experiences appreciated.  

XM193 is the only NATO pressure load in your group so it is likely a chamber problem.

What is happening is you have both higher pressure in the barrel and a chamber that is easier for brass to stick to (no chrome lining and probably .223 SAAMI spec instead of 5.56mm NATO).

As a result, there is more force trying to keep the empty cartridge in the chamber and your bolt and extractor have to work harder to pull it out. Usually the extractor will slip first and the shell will stay in the chamber; but you can also have the bolt use up a lot of momentum pulling against the higher pressure and it will not cycle completely or fail to throw the empty clear.

The cheapest way to solve your problems is just to stick to SAAMI spec ammo; but if you have to use NATO pressure ammo and want reliability I'd recommend a 5.56mm chamber reamer and polishing the chamber.

Since your barrel is non-chrome lined you should be able to send the upper to Kurt's Kustom (Industry section) and have him ream it to the M16 specs.

Are you saying that a nonchrome lined bbl. will have problems with M193 spec ammo?

No, barrels with a SAMMI spec chamber are MORE LIKELY to have problems with M193 ammo (and it usually shows up as a FTE).  Not all non-chromed barrels have SAMMI spec chambers.

Thanks for the advice and input guys.  

I posted a link to this over on the JT forum, and Jesse replied with a solution.  It seems that the chamber coating (parkerizing) is sometimes tighter than black oxide and sticking the 5.56 rounds in the chamber on a few of their barrels.  He recommended chucking up a chamber brush in a drill and running it through for a few seconds.  I will give this a try and see what happens.  I was beginning to wonder, since all JT barrels are supposed to be 5.56mm.  I thought I might have received a .223 accidentally.

Great analysis Bartholomew .  You were right on about the chamber tolerance being closer to a .223 than a 5.56, but instead of a .223 chamber it appears I have a "tight" 5.56 that needs a little TLC with the brush.  

All J& T Barrels are 5.56 NATo, Not .223 SAAMI, it shoiuldnt be a barrel problem, everyone seem to think that A non Chrome Barrel is to be blamed for every Ar Failure.

The truth is , Federal XM193 ammo is not what its cracked up to be , its not high quality ammunition, its hot and somewhat accurate but it is not a quality made product, that Dingy unpolished case will Jam your Gun everytime.

.But thats NOT your Problem right now , The Cases on the XM193 are reused cases, they are expanding too much and jamming in your Chamber because the Brass is soft, Get a micrometer or Caliper and measure the Base of one of these XM193 cases and see if they are not Way too much expanded compared to the other ammo that is not Jamming up your Gun.
Its the soft Dingy Xm193 cases not your Non-Chromed Barrel/Chamber.

Poke, glad to hear you have the problem worked out (although I'm a Sooner myself). Let us know how that works.



Well if it is the ammo that "will jam your gun everytime", you would think you'd see a lot more unsatisifed XM193 users. How do you explain the high regard for XM193 here?

This problem w/ JT barrels & the Park flowing into the chamber has been addressed before. I personally think JT should be checking & cleaning chambers long before there shipped off. What ammo do they test fire w/?? You guys just need to quit being so cheap($30-$40); Pony up the extra $$ for quality w/ chrome ch/br. I have had problems myself, until I chromed up. Easier cleaning & not one extraction problem. I'm not saying chrome is end all, but for me it has made a difference.   -Justin

Not every one, but it ranks right up there as being a top cause.


If that is the case with your rifle, why don't you try a real barrel - say a nice chrome lined Colt or Bushmaster.  I can assure you my Bushy's don't have any problem with those 'dingy unpolished' rounds.


BS any DECENT barrel should be able to handle it.  If the barrel is so finnicky it can't handle XM193 then it should be fixed or replaced.

Bart-
A very articulate response...makes a lot of sense. Thanks.

Got to go with Forest on this.  My LC brass is great and has been loaded over and over and shows no sigs of being shitty soft brass.  My Bushy's run LC XM193 as good (or better than) ANY 223/556.  I have run well over 2K LC XM193 (various lots) and can count the FTF's/FTE's on one hand.
Sleepy717

I'm gonna agree with the latter portion.....The second quote... And No "ding" has ever fouled my rifles into FTE/FTF's from XM193.  Lucky I guess!

Bring on the dingy unpolished brass for me!! Two Bushmaster's and a Rock River all with a bunch of xm193 through them and not one, not even one problem ever.

And BTW, when I was working for the Gov several years ago the brass we used was unpolished, can't say it was dingy, but definitely unpolished.

Lucky(?) for me in my 223 chamber/no chrome Eagle I have shot up 2K of LC M193, Fed XM193, IMI M193, IMI M855, Q3131A, RG SS109 [b]without a SINGLE FTF that wasn't magazine-related[/b]
No signs of overpressure or bulging cases, ever.

Only ammunition I had trouble with was the Spanish Santa Barbara green tip. FTE (3/40 fired) caused by extractor ripping through case rim at chamber. I concluded the brass was weak/defective. I just don't shoot those anymore.