Ask Ian: .223 vs 5.56 and "Military Grade Ammo"

Ask Ian: .223 vs 5.56 and "Military Grade Ammo"

Cool Forgotten Weapons merch!

From Michal on Patreon:
“Can you talk about difference between .223 Remington and 5.56 NATO? Or in more general terms about possibility of using military grade ammo in civilian rifles. I heard everything from ‘it will explode’ to ‘it will work normally’.”

The short answer is that the difference between .223 Remington and 5.56mm NATO is immaterial to most people. It’s better the use .223 in .223 chambers in the long run, but really not a big deal. There is an excellent article on this written by Andrew Tuohy on the LuckyGunner blog which I can’t link to in a YouTube description.

As for military grade ammunition, it is really no different than civilian packaged ammunition. Some folks with minimal firearms experience have the notion that commercial ammunition is somehow derated in quality or capability compared to military ammunition, and this is simply not true.

Forgotten Weapons
6281 N. Oracle 36270
Tucson, AZ 85740


  1. Harry Fuller on May 12, 2023 at 3:54 am

    I laugh when I see things advertised as "Military Grade"

  2. M. Reginald Goldstein on May 12, 2023 at 3:54 am

    How many guns are being sold new in stores right now that are specifically chambered in .223 rather than 5.56? I mean they’re out there but it’s probably about as common as guns chambered for 38 Special rather than 357 Magnum. Just buy a 5.56 rifle and run .223 ammo in it. It’s kind of pointless to do otherwise.

  3. Randall Barrick on May 12, 2023 at 3:55 am

    As always, thank you Ian for telling the absolute truth in all of your videos. This .223/5.56 & .308/7.62X51 BS is aggravating.

  4. Toast-Kaki on May 12, 2023 at 3:57 am

    I will not shoot 9mm for MAT49 in a luger P08. It’s called in both cases "9mm parabellum" but it’s not the same cartridge.

  5. Richard Powell on May 12, 2023 at 3:59 am

    Yes military chambers are a smidge looser & military ammo is a smidge hotter. This is not making them separate ctgs. The confusion is because of 2 different names. About the same time that the US Army was adopting 5.56 the US Govt was on a big push to convert the US too the metric system. This of course crashed & burned. but one place the govt could make it stick was the US Army, so Remington called it .223 & the Army called it 5.56 mm. Simple as that. I’m old enough to remember this stuff & no one considered them different ctgs until some idiot started preaching this crap about 20 years ago.

  6. James Anderson on May 12, 2023 at 4:00 am

    Is tracer one of the night fighting options for the upcoming brutality match?

  7. Knifegash on May 12, 2023 at 4:01 am

    Do this for 7.62×51 & .308 next!

  8. ssnydes S on May 12, 2023 at 4:01 am

    There are some differences in military grade ammo and that:
    1. The bullet and primer are sealed with a paint-like substance that seals those areas against water and helps long term storage as well as operation in wet tactical areas. They have no effect on performance.
    2. In vintage ammo such as Soviet and to a lesser extent Nato rounds, the primer and propellants (powder) may be corrosive. This does require more maintenance. And additionally, this was one of the teething problems with the M-16 when it was deployed. The government changed powders to save some money without thoroughly testing and low & behold, the new powder had severe fouling problems that the hapless GI’s who had not been issued cleaning kits found themselves with useless weapons.

  9. Friendly Reptile on May 12, 2023 at 4:02 am

    I would like to see a video about the 7.62 Nato vs 308 b.c. most people think they are the same but they are not if we talk about microsopic differences. You could stop all those people talking bs 😀

  10. Fire Storm on May 12, 2023 at 4:07 am

    One gun, one, that I have had, absolutely would not work properly with both caliber designations. It was an H&R Handy rifle marked .223 Rem. It fired and functioned perfectly with .223 cases but ANY military Headstamped ammunition simply would not eject. The cases had to be knocked out with a cleaning rod. There was always a shiny ring on the brass right behind the shoulder. But , keep in mind that this ammo was NOT factory loaded and was all loaded in dies marked .223 Rem. But those marked with military headstamps still would not eject.

  11. Darrin Clough on May 12, 2023 at 4:09 am

    I went shooting this weekend and shot my freind’s AR and was wondering exactly this

  12. Bradley Rounds on May 12, 2023 at 4:11 am

    Do you think anyone gives a rats ass what you are saying,they both work in the same

  13. Tommy T on May 12, 2023 at 4:12 am

    I have fired many 5.56s in my Remington 700 chambered for .223. All was 55 grains. I did this because I sold a 5.56 semi auto and had a lot of redundant cartridges. I never had a problem. No hang fires from light primer strikes, and no extraction or ejection issues. The 700 is a strong action with a long leade. I can’t think of any reason not to use up cheaper 5.56 ammo if it’s accurate enough for your purposes.

    PS. Love Ian’s videos!

  14. David Gearardo on May 12, 2023 at 4:12 am

    I have found that my 14.5 chambered in 5.56 actually loves 62 grain .223 rounds, idk why and it’s irrelevant to me , it likes it so I shoot it.

  15. Jeffrey Heronemus on May 12, 2023 at 4:14 am

    There is a huge difference between an M193 round an M855 round. Regardless of this explanation I would not suggest firing M855 through anything short of a 1 in 7 twist thickened barrel .223/5,56, I can also say from experience there is a huge drop off in performance if you fire M193 ammo out of an M16A2/AR15A2 vs using its proper ammo..

  16. Clint Babb on May 12, 2023 at 4:14 am

    .223 Wylde is an intermediate chamber designed specifically to address this. I don’t know from personal experience, but I’ve read .223 Remington from a 5.56 NATO chambered firearm is less accurate, while 5.56 NATO from a .223 Remington isn’t technically designed for these pressures. Wylde allows for both accuracy and also designed for 5.56 pressures regardless of the choice between .223 Remington or 5.56 NATO. I’m no expert, but I like the idea my .223 Wylde is designed for both, rather than taking a chance. But I’d trust Ian with my life, so I’d have no problems putting a 5.56 NATO in a .223 Remington after seeing this video.

  17. michael taylor on May 12, 2023 at 4:15 am

    i have fired an awful lot of 5.56 out of my .223 remington stamped ruger mini14.

  18. Jack DeLancey on May 12, 2023 at 4:16 am

    It has been my experience military ammo tends to be dirtier, Leaves more powder residue. For what it’s worth.

  19. happy haunter_55 on May 12, 2023 at 4:16 am

    as a fool who worked shortly in ye olde local gun shoppe, the 9×18 Mak was by far the most common thing that people did

  20. Blackhawk 7R on May 12, 2023 at 4:16 am

    Sooooo AR experts. Do you need a .085” leade chamber or .162”? And which neck diameter do you require, a .248”? .250”? .255”?
    See where I’m going here young grasshopper? It goes far deeper than a mere cartridge discussion.

  21. John Daltrocanto on May 12, 2023 at 4:18 am

    Finally the chief justice of the supreme court of firearms has issued a ruling, thanks gun Jesus.

  22. Destroyer Of Worlds on May 12, 2023 at 4:19 am

    Sort of related… I asked the kid at the ammo counter for a box of 38 super and he handed me a box of 38 special. He didn’t know the difference.

  23. Scott McCrea on May 12, 2023 at 4:21 am

    Your videos are consistently some of the quietist videos on YouTube. Not a problem, exactly, but I have noticed it.

  24. Mike M. on May 12, 2023 at 4:21 am

    .223 Wylde?

  25. Titan on May 12, 2023 at 4:21 am

    So in short: a rifle chambered for .223 can shoot 5.56 as well, but you may rarely have an issue or two. One chambered for 5.56 can shoot both without issue. Got it. Glad I have a multi-caliber AR-15 then.

  26. Archie Silkworth on May 12, 2023 at 4:21 am

    There is a caveat with shooting. 5.56X45 in a .233 Rem. Rifle and that is it depends on the individual rifle. I had an early Ruger Mini 14 that would absolutely not handle 5.56 NATO. If you had the misfortune to actually chambered and fired it, you instantly had a stuck case. While I personally don’t believe pressure to be a concern and have no issues shooting. 223 ammo in my 5.56 rifles, I will never again shoot 5.56 ammo in a .233 rifle.

  27. Jim H67 on May 12, 2023 at 4:22 am

    I’ve heard by an old timer that military ammo brass is thicker and stronger,at least in 30-06? Hes reloaded for years and prefers military brass . Anyone heard this or know if that’s true?

  28. DLN1234 on May 12, 2023 at 4:24 am

    Today I finally got the truth about 5.56 vs. 223 from a Vietnam war Vet.
    Pre Vietnam and post for a few years 5.56 was different from 223 but just in case wall width. The real difference was in the chamber primarily the throat which the 5.56 throat was longer so when fired the case neck could expand further due to the increase in pressure over 223 plus primer crimps.
    Nowadays the ammo manufacturers realize they could have the identical measurements in cases for both 5.56 & 223 BUT the increase in pressure to 60k for 5.56 requires longer chamber throats for case expansion which is not needed at 55K or less that is on the 223.
    If you are going to be shooting any round in excess of 55K of pressure then make sure you are using a 5.56 chamber for that extra expansion length for the neck. If you don’t the neck in a 223 could hit the end of the throat and then push backwards into the bolt which if very or no space between the case head and bolt face ; well you can figure out that one right ?
    Hornady manual for 223 – 62gr FMJ-BT W/C max load is 27.4gr. of CFE223 powder and for 5.56 NATO – 62gr FMJ – BT W/C max load is 27.7. More pressure in 5.56
    Hornady has no data for bullets less than 62gr for 5.56 with the exception of the GMX 55gr which is a copper bullet so these Winchester & PMC 5.56 rounds being sold as 5.56 are truly 223 rounds with a little more powder. My last bunch of Winchester 5.56 55gr had 27.5 gr. of powder and sold as 5.56 rounds requiring a 5.56 chamber to be safe.
    What a scam people what a scam. 223 with a little more powder that’s all it is !
    No additional brass in the wall widths.


  29. Nigel 900 on May 12, 2023 at 4:26 am


  30. 12vscience on May 12, 2023 at 4:29 am


  31. Chuck Mellette on May 12, 2023 at 4:29 am

    in an AR, if you shoot true 556 in a true 223 chamber, you will have problems. sure might work ok but is a problem. chambers are marked for a reason. I have seen lots of major malfunctions in training events that in combat would be EOL.

  32. J B on May 12, 2023 at 4:32 am

    Gotta disagree. I have seen several instances where .223 designated AR 15s from the late 90s/Early 2000s, were significantly and dangerously damaged by 5.56. Fortunately, there were no serious injuries, but I would NOT risk firing 5.56 in a .223 designated barrel, even modern guns.

  33. William on May 12, 2023 at 4:34 am

    August 2005 my battalion deployed to Baghdad, Iraq. Went to the zero range to get our M-4 carbines zeroed for patrols we were about to start going on. Got issued 5.56 ammo and started shooting. Every single weapon was having problems with the ammo. Failure to fire, failure to eject. Turns out, we were issued British 5.56 ammo and it was not designed for US military weapons. Once the ammo was switched, our weapons performed like they were supposed to.

  34. P C on May 12, 2023 at 4:34 am

    I’ve been handloading since the 1970s and I figured as long as 5.56 ammo wasn’t pressed up against the rifling, it would be safe to shoot in a rifle chambered in 223. Therefore if the 5.56 ammo was seated just a bit deeper, it would be fine to shoot. Thanks for the video.

  35. Gary Totty on May 12, 2023 at 4:34 am

    so what’s the real difference? Two things; the chamber (mostly the throat area), and the case is roughly loaded 10% hotter. But that’s still less than 65K psi. The .223 is loaded to the area of 57K psi. Yet 99% of the 5.56 rounds are loaded at 59K psi (per factory). Now lets say you got a typical bolt action that you’d like to shoot surplus 5.56 ammo in. Go ahead! If the bolt action won’t handle 80K psi, then it isn’t safe to shoot anyway! In an AR15, remember you’re still using a steel to steel action lock up just like the bolt gun. One issue that most fail to see is the real fast twist rifeling we see. Pressures will spike, but will not goto 65K psi.

  36. wishiwascooler on May 12, 2023 at 4:36 am

    Always wondered this and asked my gun buddies this and they could never fully answer me. Thanks for the vid as always!

  37. Paul on May 12, 2023 at 4:36 am

    There are a lot of guns marked .223 with 5.56 chambers and the owner will never know the difference. The mini-14 is a prime example and I’m sure many different bolt action .223’s as well. The 223 Remington cartridge has a maximum pressure of 55,000 psi and the 5.56 Nato has a maximum pressure of 62,000 psi. If you a fire 5.56 Nato round loaded to full pressure in a true .223 Remington chambered bolt action rifle you will find there is a big difference in the two cartridges. It will require a good amount of force to rotate the bolt and the brass will be deformed. I learned this from a very accurate Howa 1500 mini action chambered in .223 Remington. Semi-auto’s may be more forgiving but not bolt guns with true .223 Remington chambers.

  38. Rick on May 12, 2023 at 4:37 am

    this one of several videos I watched on this this morning, and by far the best. Thanks.

  39. R3CKLESSRHINO on May 12, 2023 at 4:38 am

    9 Makarov ammo in a 9mm lol, dude should have bought 380 it would run but really unreliable.

  40. Metatron Men on May 12, 2023 at 4:38 am

    5.56x45mm ammunition is loaded to a significantly higher pressure than .223 ammunition. So you can fire 223 in a 5.56 but no 5.56 in a 223 chambered rifle.

  41. Ru2yaz on May 12, 2023 at 4:38 am

    For safety purposes, the rifle chamber safety factor design is typical n×(max pressure) where n could 1.5, 2, 2.5, 3, and so on.

  42. Fenrir Lokisson on May 12, 2023 at 4:40 am

    Nice this confirm my suspicion that this debate arised from misinformation, the only thing i was surprised about is tht mil-grade is actually made with more loose tolerance for a lower price point, i actually thought mil ammo was more tighter grouping and consistent, now it makes sense that marksmen use match grade ammo

  43. Eloise Harbeson on May 12, 2023 at 4:41 am

    My T/C Contender .223 barrels do not tolerate 5.56 cartridges. The 1/12" rifling doesn’t stabilize a projectile heavier than 60gr, and 5.56 loads nearly always stick in the chamber causing the gun to be difficult to unload and the extractor to bend.

  44. Richard Powell on May 12, 2023 at 4:41 am

    Look at some old reloading manuals. They don’t list separate data for 223 & 5.56.

  45. billm23456 on May 12, 2023 at 4:42 am

    So I can use 5.56 in my Remington 700 .223? I’ve never seen a reference to bolt actions.

  46. ReaperCH90 on May 12, 2023 at 4:47 am

    If you own a Sig 550 (Sturmgewehr 90), using Swiss military 5.56 ammo (GP 90) is the best choice because optimized for it. Of course you fan use anything else and it doesn’t matter if you shoot short range anyway.

  47. ferrall derrall on May 12, 2023 at 4:47 am

    One is ok with alot more zippy zap powder and another was never meant for this?…just never got tested for these propellant

  48. James Herron on May 12, 2023 at 4:48 am

    And I did not know that the armor light was originally chambered in 222 I would love to have one I have a 222 Remington bolt action my father purchased in the 1950s The cartridge is extremely versatile and there is a wide range of bullet weights and powder charters

  49. James Herron on May 12, 2023 at 4:49 am

    thank you very much Gun Jesus lol there are a whole bunch of idiots on the Internet with YouTube channels who are still telling people that there is a difference between 556 and 223 Remington I seen one just the other day where the guy said there is a difference in the length of the case I’ve been reloading ammo for 40 years I tried to correct him he called me a Effing moron I will be sending links to your channel

  50. Henning Klaveness on May 12, 2023 at 4:50 am

    I’ve experienced real-world problems feeding surplus 7.62×51 NATO through a modern bolt action hunting rifle chambered in .308 (many years ago so I don’t remember which exact model). There was noticeable drag feeding the the rounds into the chamber, and the case consistently got stuck when firing, so that you had to use an uncomfortable amount of force to unlock the bolt and extract. I seem to remember striking the bolt handle with the palm of my hand. The owner said that this had never happened when using civilian ammo; have I been wrong in my assumption that the problem was due to tolerance deviation between civilian and military grades of ammo?

Leave a Comment