New ammo - 5.56 x 45mm 77gr Mk 262 Mod 0

[1feral1]

This new type ammo is all new to me, but a new ammo is being used by the US in limited issue in both for operational and training. it is made in the USA by a company based out od South Dakota, and is called the mk 262 mod 0 5.56mm cartridge. There is even an upgraded version called Mk 262 Mod 1 type out too.

To refresh ourselves on 5.56mm ammo:

5.56mm M193 has a 55gr projectile
5.56mm M855 has a 62gr projectile ( this is the NATO std SS109 which both Australia and Canada use - we have different names for it)
5.56mm Mk 262 Mod 0 has a new 77gr projectile, and is now in limited use

M193 is suitable for 1/9", 1/12" twist
M855 is suitable for 1/9" and 1/7" twist
Mk 262 ????

I don't know much more, but I am assuming 1/7" is compatable.

if anyone elsel out there knows anything, or wishes to add anything on this thread, feel free.

I will know more myself when I actually see this stuff, which is coming up soon. Australia as of yet is NOT adopting it. I'll see this thru US troops here.

I'll be googling it myself later.

Cheers,

Wes

 

[TCBF]

The mk designator makes me think Navy, which makes me think SEAL.  If the weight is increased with no appreciable increase in diameter - a safe assumption in the case of a rifle bullet ;D - then either heavier cores are used, or a longer bullet.  If a longer bullet, they will need the 1:7.  Though we all know the 1:7 was for the M856 Tracer.  M855 Ball would have done OK prob with a 1:9.

Heavier may mean slower, so it would make life easier - and longer - for one  if one were to be re-incarnated as - say... - a supressor.

;D

Tom

 

[1feral1]

Maybe you are right about the Mk designator, as its the USMC who are going to be using it. Buyt yet again what about the Mk11 Mod 0 SR-25's (is ther anything US navy about these - but wait, I think I remember the US Navy Seal badge on the operator's manual.,   I have closely examined these 7.62mm rifles with Brunell's u-bewt leather slings (early Garand type) and equipped with Pellican water tight cases.

Cheers,

Wes

 

[greentips]

The mk 262 uses a  77gr SMK ( I think they might have user Nosler at one point....KevinB knows the finer details better) and they worked fine out of 1/7. I think 1/8 is the optimal. 

 

[Cold Warrior]

To refresh ourselves on 5.56mm ammo:

5.56mm M193 has a 55gr projectile
5.56mm M855 has a 62gr projectile ( this is the NATO std SS109 which both Australia and Canada use - we have different names for it)
5.56mm Mk 262 Mod 0 has a new 77gr projectile, and is now in limited use

M193 is suitable for 1/9", 1/12" twist
M855 is suitable for 1/9" and 1/7" twist
Mk 262 ????

Those are the US DOD designations.  Canada only has one loading of ball ammo and it is the 62 Grain SS109 with the Cdn Designation of C77 Ball.  As far as I am aware we don't have any of the 77 grain ammo in general issue.

Anyway,, the MK262 needs at least a 1 in 8 twist,, and our C7's with 1 in 7 is good to go with it.  75 grain ammo is iffy in a 1 in 9,, it may or may not stabilize,, mileage varies.  I'm not aware of anyone who has success with 77gr in a 1 in 9.

 

[1feral1]

Either way, it will be interesting to see how the ammo performs, as the USMC will be the only team out of 15 other international teams with the 5.56mm Mk 262 ammo at AASAM.

France will be using their steel cased 55gr rd in their G2 FAMAS and Para Minimi (both 1/12"), Thailand too, and The Philippines, I am sure are equipped with 1/12" M16 FOW's and the rest of the teams are all pretty much SS109 variants.

M193 is alive and well in many nations still.

Cheers,

Wes

 

[Troopasaurus]

Just thought i would add some links with info on teh mk262... looks interesting.
http://www.btammolabs.com/tests/6.htm
http://www.ammo-oracle.com/body.htm#mk262

 

[Kal]

I am under the impression that the 77gr. round is superior to that of the 55gr. and 62gr. rounds.  However, wouldn't the effective range be shorter because of the slower, larger round not causing the same wounding characteristics as the lighter rounds.  Or does the mass of the larger round overcome it's velocity short-comings?  Am I making sense?

 

[greentips]

Match bullets such as the SMK ususally have a much thinner jacket.  The 77gr bullet improved terminal ballistic, based on my understanding, comes from a lower velocity threshold of fragmentation. IIRC, it will frag at 2200 fps while the M855 and M193 needs between 2600 fps and 2700 fps. This roughly means the 77gr SMK will frag at about 250 yrds out of a 18" barrel while the M855 will max out at about 150 out of a M16  The 77gr bullets are also match bullets, if they are loaded properly, they can be very accurate. Furthermore, 77gr bullet has a higher ballistic coeffiicient and its weight retains velocity much better than the lighter bullets. The heavy bullet starts slower in the begining but outrun the lighter bullets at somewhere around 400 yrds downrannge, with less wind deflection. 

 

[1feral1]

Can you define frag? It sounds like your saying the bullets looses it and falls apart at 250 meters out???  I have hit tgts (fig 11)  in excess of 400m with M193 alone, and I thought the MV for M193 was about 3200 FPS from a 508mm bbl, and a little less for C77 (IVI) and F1 (ADI) ball?

Wes

 

[greentips]

http://www.btammolabs.com/fackler/wounding_patterns_military_rifles.pdf

KevinB probably knows the number by heart and he is more of a subject expert than me....but a SS109 type bullet travelling with a MV of 3050fps will drop to roughly 2600 fps at 150 yards while the M193 with a MV of 3250fps will be going at 2600fps at about 180yrds.  however, if you have a ballistic calculator handy, the advantage of the low frag velocity of Mk262 becomes apparent with a short barrelled weapon.  M855 has a frag range about 50M out of a M4, but becasue of the low frag velocity of the MK262, its frag range is much farther even if the MV is much lower.  I am definitely not an expert with 6.8 SPC, but IIRC, it is designed from ground up to frag at low velocity so it will be effective with very short carbine. 

 

[1feral1]

Can you define what you mean by 'frag'.

I know upon impact of mass the projectiles do come apart, the M193 more than the SS109. I am familiar with these patterns with 5.56 (various), 5.45, 7.62 M43, and 7.62 NATO on ballistic gel composite.

Also I am aware of the principles of ballistics with both a decreasing velocity, and drop of the projectile over distance. I am just confused with the terminology (frag) you are using.

Cheers,

Wes

 

[Kal]

Greentips - Thanks for the clarification.  Would you or anyone else know the effective wounding ranges for this round for barrels, 20, 16 and 10 inches in length? 

 

[KevinB]

Sorry I have been out -- I will get back to this when I can - Coles notes history currently...


US Navy started using the 77gr Sierra Match King for their rifle matches, both they and the US Army Markmanship Unit (AMU) foudn it to be the best performing "cross the course" round out there. This was in the mid/late 90's - they where using factory loaded ammuntion by HSM (Hunter Shack Munitions) then out of Missoula Montana

At a similar time frame the US Army was developing the SPR (which started out as special purpose receiver - an upper to drop on a SOCOM M4A1 lower - andthat had a 22", 20" or 18" barrel - which was standardised upon the 18" Douglas Stainless Steel barrel in to flavour the SPR and SPR-A (these became the Mk12 Mod0 and Mk12 Mod1 once typce classified)

This round called AA53 in terminology - but upon accpetance in "standard" USSOCOM circles it was classified as Mk262 Mod 0 - a Sierra Match King 77gr BTHP.  Problem with bullet set back led to the search for a round that had a cannelure with the added advantage that the cannelure would decrease the length of the neck of the wound track on human tissue.

Sierra intially resisted adding the cannelure and the Nolser 77gr OTM (BTHP) was chosen to be the round of choice for the Mk262Mod1 ammuntion.

Sierra relented and only some small runs where done with the 77gr Nosler.

Mk262 Mod1 is currently the production ammo for use with USSOCOM and other US Military branches.
  I am guessing the USMC is issuing old lots of Mod 0 - since they seemed a bit more accurate than the Mod 1 due to the cannelure.

_____________________________________________________________________________________________________________

M193 impact velocity in human tissue for relaible fragmentation 2700 fps

M855 = 2600 fps

Mk262 = 2200 fps.

M855 DOES fragment better than M193 - and due to the disimilar construction (the steel pentrator and lead under cover) and longer length fragments at a slightly however some lots have a large neck and as a result has gained a reputation for unreliability in stopping foes.

 

[Dissident]

All hail KevinB!

Thank you.

 

[KevinB]

Shortly after it became AA53 - BlackHills was awarded the contract - they have and still produce the only Mk262 (both Mod 0 and 1) ammuntion.


My Mk262 Mod1 ammuntion that I have gotten from BlackHills and USASOC chrono's at lot faster than the HSM ammuntion.  The HSM was a SAAMI spec round while the Mk262 is a NATO pressure spec round with an accordingly faster MV.


With C77 ball

Your looking at a fragmentation range of:
5-10m with a 10" C8CQB
45m with a 14.5" C8/C8A1
90m with a 16" C8SFW / C8FTHB
130M with a 20" C7/A1/A2


I dont have the Mk262 frag distance in front of me - I will dig them out


http://nightoperations.com/Doc/Infantry-Rifle-Carbine1.pdf

 

[TCBF]

Good article Kevin, thanks.

Tom