6mm SPC. Would you?

[Sean K.]

I can't help you with 10.5" barrel performance. The only gel tests I've seen are for 6.8 SPC and 6.5 Grendel fired from 14.5" and 16" tubes. Here's what I have for those two rounds:

Sierra MatchKing loads (16" barrel)

----------------------- Range _ 0 __100 _ 200 _300 _400 _500 _600 yards
Silver State  6.8 SPC 115gr
--------------------- Velocity 2550 2287 2042 1812 1601 1414 1256 ft/sec
---------------------- Energy 1660 1336 1064 _839 _654 _511 _402 ft-lbs
----------- Drift (10 mph wind) _0.0 _0.5 _2.3 _5.4 _10.2 _16.9 _25.7 inches
Black Hills 6.5 Grendel 123gr
--------------------- Velocity 2450 2285 2127 1976 1831 1693 1564 ft/sec
---------------------- Energy 1639 1426 1236 1066 _916 _783 _668 ft-bs
----------- Drift (10 mph wind) _0.0 _0.4 _1.5 __3.4 _6.3 _10.2 _15.3 inches

Terminal Effects

Wound profiles in gel tests are similar for both 115gr 6.8 SMK and 123gr 6.5 SMK, with early yaw and fragmentation.

Anecdotal reports in the "Hunting" sections of both forums indicate equal effectiveness on animals, when using hunting loads.

Thanks for the info.

Sean

[DSM]

Reading up on the various, and many, 6mm wildcats out there I remembered the 6mmAR cartridge.  It's really just a 6.5G necked down to 6mm.  Now before everyone assumes I've got some sort of man crush on 6mm let's revisit the motive:  6mm just offers more capability in bullet selection without being wed to long ogive, match bullets.  [whispers] ...although the match 6mm slugs have higher BC's than 6.5 does, and are proven performers in benchrest and highpower.  I don't like the short, squat cases you have to use but I might concede that as a compromise in the same bolt conversion discussion.  

I'm still of the opinion that a 6x43mm SPC/6 WOA  or the slightly modified 6x41mm would offer a lot when paired with the XCR platform.  Distance?  Well, John Holliger (White Oak Armament) does the 6 WOA for highpower.  Yes, those are race guns but the potential is obviously there.  If extended distance and accuracy is your goal then I'm doubting your XCR is your first pick.  (OK, prove me wrong with a pic of you and your XCR on the line at Camp Perry! )  Cost associated with such a mod would also be lower.  6.8 brass is still pricey but still cheaper than 6.5G, from what I've seen.  (Once again, I'm sure someone knows a Cousin Eddie that sells it for a nickel per 100!)  The heavy, match bullets will always be comparable in price however if that is your choice of fodder.  

[stanc]

I'm still of the opinion that a 6x43mm SPC/6 WOA  or the slightly modified 6x41mm would offer a lot when paired with the XCR platform.

And I still agree.

[DSM]

I'm still of the opinion that a 6x43mm SPC/6 WOA  or the slightly modified 6x41mm would offer a lot when paired with the XCR platform.

And I still agree.

But there's at least one person praying for my salvation!   

[crenca]

Good question(s).

I think I still think of all of these variations as man stoppers.  For dear, hog, and hunting of medium game they work but then a dedicated hunting rig (in a standard hunting caliber) is the answer for most folks.  I know the 6.8 fans/promoters like to promote them for hunting but I think that is mostly due to the fact that they can't promote them as economical assault rifle cartridges since there is no significant .mil/.gov adoption.

Sooooo, since 6.5G and 6.8x43 are both improvements in typical engagement distances (I know Afghanistan is an exception that proves the rule) over 5.56 - and anything beyond 500 yards is probably better served by 7.62 mags or 338 - I suppose I would like to see improvement in the economics (by greater adoption or some other change) before an intro of another 6.x round even if it has better ballistics in this or that performance profile.

At some point you are tweaking for small gains around a limitation (the dimensions of AR15 mag, certain conceptions about weapon weight/size, etc.) that really begs the question - why not go to the source and revaluate the limitation. 

I guess what I am trying to say is that for the normal purpose (my purpose) of a black rifle I don't think I would be interested - unless there was a significant $cost$ saving over 6.8x43 and 6.5G.  Since any new spec would likely equal or exceed the cost of 6.8x43 for several reasons, I don't think the performance gains would overcome this.  For a few yes, but the number would be small...

[DSM]

crenca-  True, economics will always be a factor.  Until Uncle Sam adopts something other than 5.56 or some country surpluses boatloads of a better round I don't reckon anything will be able to compete, in terms of bulk components driving availability up and prices down.  Larger bullets take more resources too.  

For now, 6.8 brass is still cheaper than 6.5G.  Necking down to a caliber that offers more choices in usable bullets can save $$ too by not being stuck within a certain weight class or type of bullet.  Savings?  Slight, it's still basically a reloader's cartridge at the end of the day.  Alex did apparently negotiate the 6x45 with CorBon and I suppose the option is there to try with the same or other companies, SSA maybe?  Factory ammo will still be about the same cost however.  

I believe the fact is that we are wading through so many cartridges designed to "solve" the problems of 5.56 that no one round will really shine above the others. (...and I'm admittedly adding to it!   )  It's all subjective based on what one thinks is ideal to their given situation.  

[stanc]

I believe the fact is that we are wading through so many cartridges designed to "solve" the problems of 5.56 that no one round will really shine above the others.

I agree. However, I've always thought that neither 6.5 Grendel nor 6.8 SPC are the optimum alternative to 5.56 NATO, so that's why I'd like to see as many different options as possible developed and evaluated.

[DSM]

I believe the fact is that we are wading through so many cartridges designed to "solve" the problems of 5.56 that no one round will really shine above the others.

I agree. However, I've always thought that neither 6.5 Grendel nor 6.8 SPC are the optimum alternative to 5.56 NATO, so that's why I'd like to see as many different options as possible developed and evaluated.

Therein also lies a problem because until someone lays out a specific, operational requirement for a cartridge to achieve, anything that is developed makes the comparisons moot.  I could say that going back to 7.62 NATO is optimum because it is already in our supply chain, is standardized in NATO, there are vast stocks of it in war reserve and the ability to increase production is a shift change away.  The round is proven, powerful and has the advantage of "same caliber" logisitics for the fighting unit.  No cartridge development is needed, adopt and go.  But then again, 7.62 is heavier and would require more training to learn control in rapid fire and quick, close-in engagement.  Costs would increase and more resources would be expended, not to mention an entirely new rifle has to be adopted or adapted.  Even with that, adopting a new cartridge other than 7.62 means I'm not only paying for the new round but also to adapt/adopt the rifle to fire it, the 7.62 route is solely a rifle.  And so on, and so on....  Without a constraint to work in or a standard to meet it gets too fuzzy and just becomes whatever the next guy feels is the best way to tackle the problem. 

[stanc]

I believe the fact is that we are wading through so many cartridges designed to "solve" the problems of 5.56 that no one round will really shine above the others.

I agree. However, I've always thought that neither 6.5 Grendel nor 6.8 SPC are the optimum alternative to 5.56 NATO, so that's why I'd like to see as many different options as possible developed and evaluated.

Therein also lies a problem because until someone lays out a specific, operational requirement for a cartridge to achieve, anything that is developed makes the comparisons moot.

I'm sure you're right...but, I'd still like to see it happen.

I could say that going back to 7.62 NATO is optimum because it is already in our supply chain, is standardized in NATO, there are vast stocks of it in war reserve and the ability to increase production is a shift change away.  The round is proven, powerful and has the advantage of "same caliber" logisitics for the fighting unit.  No cartridge development is needed, adopt and go.

I agree, but by "optimum alternative to 5.56 NATO," I meant an alternative cartridge of size and power usable in existing 5.56 weapons, not an alternative that's fiscally and logistically optimum.

But then again, 7.62 is heavier and would require more training to learn control in rapid fire and quick, close-in engagement.  Costs would increase and more resources would be expended, not to mention an entirely new rifle has to be adopted or adapted.  Even with that, adopting a new cartridge other than 7.62 means I'm not only paying for the new round but also to adapt/adopt the rifle to fire it, the 7.62 route is solely a rifle.

IMO, training would be manageable; after all, they did it before, with the M1 and M14 rifles. And it'd certainly be easier and faster for the U.S. to adopt a new 7.62 rifle, than it would be to get a new cartridge adopted by NATO.

OTOH, there are few people in the military who want to revert to 7.62 for rifles. I think the two-caliber system has proven to be a better concept overall than the unitary caliber approach of full-power rounds like 7.62 NATO. It's just that some tweaking is needed to get an intermediate-power round with greater range, penetration and stopping power than 5.56 NATO, but without incurring too much penalty in ammo weight and magazine capacity.

[DSM]

Devil's advocate, stanc, I didn't want to drag around a full-on 7.62 when I was in! 

[crenca]

It's just that some tweaking is needed to get an intermediate-power round with greater range, penetration and stopping power

IMO, the last two are the really needful thing, where as greater range is best handled by already existing 7.62 NATO and magnums.  Seems to me that as soon as you throw all three into the mix you have moved out of the "assault rifle" concept into the "main battle rifle" concept and requirements which means bigger/heavier rifles and ammo.  If you keep the requirement of effective terminal ballistics/accuracy within 4 or 500 yards then you can keep your lightweight AR.  If you don't then I am not sure you can have your cake and eat it too.  What do you guys think?

[stanc]

It's just that some tweaking is needed to get an intermediate-power round with greater range, penetration and stopping power

IMO, the last two are the really needful thing, where as greater range is best handled by already existing 7.62 NATO and magnums.  Seems to me that as soon as you throw all three into the mix you have moved out of the "assault rifle" concept into the "main battle rifle" concept and requirements which means bigger/heavier rifles and ammo.

I concur that greater range is better handled by 7.62 NATO, but disagree that range can't be increased sigificantly for assault rifles and squad autos. The ability to increase range while remaining within the intermediate cartridge envelope is demonstrated by 6.5 Grendel.

IMO, the only question is what degree of balance between range, penetration, and stopping power is optimal. Clearly, the British soldiers cited in the story at http://xcrforum.com/index.php/topic,5335.msg77795.html#msg77795 want their rifles to be capable of longer range engagements than is possible with 5.56x45.

[aziator]

I think the issue that you run into when tyring to increase the range of the common rifle issued to everyone is the ability to aquire and engage targets with optics that are light enough to carry around all day.  They aren't going to put a NF or other scope on every rifle.  How far can one realistically (and accurately) engage a man with a zero magnification red dot (or at best, a 4x ACOG).  Bottom line, I don't think that DOD is interested with putting bigger and heavier stuff on the rifles.  Average joes that are running around with a M2 or M4 on top right now are not going to engage someone past 300-400m at best.  The people that habitually engage targets at longer ranges have what they need to do that. 

We really just need something with a little more knockdown out to the 300-400m range.  After that most weapons systems in country don't have the correct optic to ID or engage the target.

[Sean K.]

I think the issue that you run into when tyring to increase the range of the common rifle issued to everyone is the ability to aquire and engage targets with optics that are light enough to carry around all day.  They aren't going to put a NF or other scope on every rifle.  How far can one realistically (and accurately) engage a man with a zero magnification red dot (or at best, a 4x ACOG).  Bottom line, I don't think that DOD is interested with putting bigger and heavier stuff on the rifles.  Average joes that are running around with a M2 or M4 on top right now are not going to engage someone past 300-400m at best.  The people that habitually engage targets at longer ranges have what they need to do that. 

We really just need something with a little more knockdown out to the 300-400m range.  After that most weapons systems in country don't have the correct optic to ID or engage the target.

But isnt' that somewhat systematic to the Army's training and engagement philosophy?  Granted in WWII we had the .30-06 Garand, but if an American "farm boy" could see someone, he shot at him....and since many of these guys grew up shooting (unlike today's youth), they had a fair amount of hits.

I think that while an important aspect in this discussion is the tool (i.e., the caliber and rifle).....more importantly is that the Army may need to be training the troops (the real weapon) to be more accurate at longer ranges. 

It certainly couldn't hurt.

Sean

[DSM]

I didn't want to get into the "range" discussion so much but since Aziator has broke spades on it, then game on!  Seriously though, it's true, target detection is a huge slice of the pie.  Unfortunately them boys don't habitually stand out in the open and allow you to dope in your sights and walk your shots in.  Lugging my M24 around all that time, it's hard to find people that don't want to be found!

[crenca]

My albeit limited understanding is that most countries infantry in WWII could not engage enemy very effectively (except for suppressing fire) beyond 2 or 300 meters with regular issue rifles.  Sure, there was the occasional exceptional "farm boy" that stretched this but this was (again) the exception that proved the rule.

One country that in one sense bucked this trend was Britain during WWI (not sure about WWII).  The Germans consistently over estimated the number of machine guns the British employed simply because the typical British infantry man was a much better marksmen than his German counterpart.

It has been said that our modern infantry man is also a marksmen - due to both training and the accuracy/recoil of our standard issue rifle.

All that being said I have to agree with what aziator said that putting a weapon that is a true beyond 3-400m range in the hands of the most rifleman is not necessary - unless battlefield conditions have fundamentally changed and I am not aware.  Increasing terminal ballistics within that range seems to me to be where any effort (and what we are talking about is a replacement of 5.56) needs to be directed.  It appears the 6.8 does this as is.  Of course, like aziator says the DOD does not seem interested in that either.  Lots of reasons speculated as to why...

[MickeyC]

It wasn't so much the marksmanship as the line batallions using volley-fire and ripple fire drills that allowed the Enfields to put down a huge volume of fire.

[stanc]

Up until 1985, it was standard procedure to train [British] infantry units to fire collectively at targets at ranges of up to 600 metres. This could easily be achieved with...the 7.62 mm L1A1 SLR rifle.

http://www.quarry.nildram.co.uk/btb.pdf

Since long-range engagement by infantrymen using iron sights was done in the past, why can't it be done now using 4X optics? Assuming a proper cartridge, that is.

With more than 50% of infantry engagements in Afghanistan taking place at ranges above 300 metres, it is clear that long-range performance remains a desirable characteristic for general purpose small arms ammunition.

http://www.quarry.nildram.co.uk/btb.pdf

Is there any reason to think that a "5.56 alternative" cartridge viable for long-range engagements wouldn't also have greater terminal effects at the 300-400 meters cited as necessary by aziator?

[stanc]

I have to agree with what aziator said that putting a weapon that is a true beyond 3-400m range in the hands of the most rifleman is not necessary - unless battlefield conditions have fundamentally changed and I am not aware.

Conditions have changed. Perhaps you didn't see the thread noting that 50% of engagements in Afghanistan occur at ranges up to 900 meters?
http://xcrforum.com/index.php/topic,5335.msg77795.html#msg77795

Increasing terminal ballistics within that range seems to me to be where any effort (and what we are talking about is a replacement of 5.56) needs to be directed.  It appears the 6.8 does this as is.

Yes, it does. So does 6.5 Grendel. And probably the wildcats based on those two also would.

The question is, why intentionally limit the engagement range of a 5.56 replacement to 300-400 meters, if 600-800 meters is achievable?

Of course, like aziator says the DOD does not seem interested in that either.  Lots of reasons speculated as to why...

Yes. My speculation is that they're holding out as long as possible to see if the caseless/cased telescoped ammo being developed for the LSAT program proves successful or not. If LSAT does pan out, it'd be illogical to make what would be only a temporary switch to a brass-cased round like 6.8 SPC.

In line with this discussion, it might be worth noting that the LSAT program is looking at developing a 6.5mm round with a streamlined projectile like that of 6.5 Grendel, rather than a stubby, low-BC bullet as is used in 6.8 SPC.

[crenca]

Again, I suppose I side with those that believe Afghanistan is the exception that proves the rule (that in most conflicts and for most soldiers 3-400 is the realistic limit).  But who knows, maybe longer distance is achievable for most (using a standard issued rifle) now for reasons I don't quite understand.

And if you can have light weight rifle and ammo/light recoil, good TB, and 5,6,700 meter range all at the same time why not? 

I have been a bit leery of the relative low velocity of the 6.5G, but perhaps I need to get over this. 

Hey, perhaps you guys have convinced me a 6.0-6.5 based on 6.8SPC is worth doing...on the other hand, as far as personal adoption probably not as I don’t need the range and/or another expensive caliber…

[stanc]

Again, I suppose I side with those that believe Afghanistan is the exception that proves the rule (that in most conflicts and for most soldiers 3-400 is the realistic limit).

Clearly, circumstances in Afghanistan are outside the norm. But, IMO it only proves that equipping with a 300-meter cartridge is another example of "preparing for the last war."

You can do CQB with a long-range caliber, but you can't participate in the long-range fight with a CQB caliber.

I have been a bit leery of the relative low velocity of the 6.5G, but perhaps I need to get over this. 

I'd prefer a higher muzzle velocity, myself. However, MV isn't nearly as important as terminal velocity.

Sierra MatchKing loads

------------------------- Range _ 0 __100 _ 200 _300 _400 _500 _600 yards
Silver State _ 6.8 SPC 115gr
------------------------ Velocity 2550 2287 2042 1812 1601 1414 1256 ft/sec
------------------------- Energy 1660 1336 1064 _839 _654 _511 _402 ft-lbs
------------- Drift (10 mph wind) _0.0 _0.5 _2.3 _5.4 _10.2 _16.9 _25.7 inches
Black Hills 6.5 Grendel 123gr
------------------------ Velocity 2450 2285 2127 1976 1831 1693 1564 ft/sec
------------------------- Energy 1639 1426 1236 1066 _916 _783 _668 ft-bs
------------- Drift (10 mph wind) _0.0 _0.4 _1.5 __3.4 _6.3 _10.2 _15.3 inches

[DSM]

So after about a week of discussion there are some interesting poll results.  The majority of folks are of the opinion the 6.8 cartridge is fine as-is although there seems to also be fair interest in a 6mm.  The parameters of the poll indicated a lower cost, same bolt conversion which may have been an influence to a positive vote.  I wonder though if that interest would translate to an entirely new and just as capable option even if the same bolt theory were not applicable?

I don't know what, or even if, RobArm has in store for the XCR in terms of future caliber conversions.  The 6x45mm was mentioned as the "mystery" conversion earlier this year but the focus has shifted from that project.  The 6.5 as originally envisioned seems dead for unknown reasons.  The last update was around the announcement of PDW production taking priority.  There does seem to be a market for folks to try something new but the three existing conversions are it for now.

[DSM]

3500fps, 55gr, 22" barrel.  Saw those numbers printed on an AR varmint rig in this caliber.  Light bullet, but that's a laser beam.

[johnny mac]

     Well, like many of you on this forum, I am at the same time searching for one gun/caliber to "do it all" while continuing to add to my already well-beyond-justification collection.  Crenca pointed out that many people are better served by a dedicated hunting rig for hunting, and other than varmints the 5.56/AR is pretty much a dedicated "fighting rig" with little usefulness for hunting.  Used to be that a gun was a gun, you fought with it, hunted with it and competed with it.  I would like the same thing-one gun/caliber suitable for everything.  I'm not going to kid myself and say I would thin out my collection much, but it might become more of a "collection", while my one rifle would become my everyday "tool".  The 6.8 nearly fits the bill, lacking only a little range.  The 6.5 fits even better, lacking only availability in the XCR.  Then again, these days I'm all googly for the MSAR E4, and if it ever becomes available in 6.8, or better yet 6.5 I'll be in another pickle.  The one huge factor for the XCR, and presumably the MSAR is that just a barrel/bolt swap, rather than a complete upper is needed to switch barrel length or switch to 5.56 if I run out of whatever "ideal" caliber I settle on and still need to shoot.

[MickeyC]

Again, I suppose I side with those that believe Afghanistan is the exception that proves the rule (that in most conflicts and for most soldiers 3-400 is the realistic limit).  But who knows, maybe longer distance is achievable for most (using a standard issued rifle) now for reasons I don't quite understand.

And if you can have light weight rifle and ammo/light recoil, good TB, and 5,6,700 meter range all at the same time why not? 

I have been a bit leery of the relative low velocity of the 6.5G, but perhaps I need to get over this. 

Hey, perhaps you guys have convinced me a 6.0-6.5 based on 6.8SPC is worth doing...on the other hand, as far as personal adoption probably not as I don’t need the range and/or another expensive caliber…

That basically sums it up, a light weight rifle, light weight round that gives you good teminal ballistics from 0-1000 m.

As for the velocity, it's no worse than 7.62x39 at the muzzle and a whole lot better at range due to the cd value.