Rifle or Carbine?

After the US Army cancelled the Individual Carbine competition in 2013 it was pretty much decided that the M4A1 design will soldier on for at least another decade before serious efforts begin to find a replacement for it. By the time that happens, there’s a good chance the competition entrants will be in a different, probably larger, caliber. In the meantime, it’s worth looking at whether the Army should be contemplating a new carbine at all, or if it would be better returning to the rifle format.

Rifle or CarbineTraditionally a carbine was a short-barreled version of the service rifle issued to supporting troops as a defensive weapon – the original users were artillerymen and cavalry. Meanwhile, the infantry relied on the longer range and heavier punch of a rifle, which was their primary weapon for both offense and defense. The US Army has now turned that on its head. The M4 will eventually replace all M16s in the Army but they were issued to the infantry first, while other specialties were left with rifles until enough carbines were procured. The USMC isn’t as convinced this is the way ahead – while they do use the M4, the primary weapon of a Marine rifleman remains the latest version of the M16A4.

So what’s prompted the Army to go down this path? Mostly it seems to have been the experience of Iraq, where the short M4 proved to be a very handy weapon in urban combat. There’s no doubt that, at 6 inches shorter than an M16, it’s easier to maneuver through doors and handle in a vehicle. Unfortunately this compactness comes at a price.

It’s been known since the early days of Vietnam that the effectiveness of the tiny 5.56mm bullet comes from its high velocity. Lopping nearly a third off the barrel reduces this velocity substantially – from 3,050fps to 2,900fps. That doesn’t seem like much, but the kinetic energy of a bullet increases with the square of its velocity, so the energy loss is much greater. At lower velocities, the bullet also doesn’t fragment as reliably, and often just drills a neat hole in the target. The result is that while the M16 is effective out to about 330 yards, the M4 can’t drop enemies reliably beyond 150. And as the urban warfare of Iraq gave way to the open fields and high mountains of Afghanistan, that became a problem.

There are various solutions to this issue either in service or under evaluation, including improved 5.56mm ammunition. However, with the M855A1 it’s likely the little bullet has been developed as far as it can go. Alternative weapon layouts are another option. The British L85A2 is shorter than an M4 with the stock extended, but has a longer barrel than an M16. On the other hand, bullpups have their own issues, mostly ergonomic, and the L85 in particular is a very heavy weapon for what it does.

As always with infantry weapons, the argument returns to heavier calibers – thousands of 7.62mm M14-series rifles have been reissued during the Afghan operation, many of them modified with shorter barrels, and the British SAS are enthusiastic users of the HK417 with barrels as short as 13 inches. The reason is simple – heavier rounds gain more of their energy from weight, and retain more power and range when fired through a shorter barrel. It’s generally agreed that 7.62 NATO is overkill for the average infantryman, but if the US Army wants to stick with carbines, something bigger than 5.56mm is definitely going to be required in the next generation.

Disclaimer: The content in this article is the opinion of the writer and does not necessarily reflect the policies or opinions of US Patriot Tactical.

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8 thoughts on “Rifle or Carbine?

  1. Loved this article.

    If the infantry branch were to go back to full powered battle rifles, wouldn’t they lose the benefit of controllable full auto fire? Many countries teach their soldiers to only use the semi-auto function with their assault rifles to conserve rounds and maintain accuracy, but full auto does have its uses in close quarters.

    Also, battle rifles like the M14, G3 and SCAR H tend to be heavy (along with their bigger rounds). Reducing the barrel length and using lighter materials will increase felt recoil and impact follow up shots right?

  2. Rifles are much like golf clubs. Different rifles are designed for different jobs. Many attempts have been made to design one type performs all. But, after a while, we’re right back to a specific rifle for a specific task. Ideally, we need a rifle that weighs 7-9 pounds (loaded with a thousand round magazine) capable of killing the enemy at ranges of one mile or more and be only about two feet long. I’m sure somebody, somewhere, is working on this.

    1. Robert,
      I want one of these as soon as they get the civilian price point below $1,000 (without optics—I’m not greedy).

  3. to keep logistics simple we need to stick to something that works. The question was rifle vs carbine in that sense Infantry should stick with rifles until a carbine is needed which means if they are deploying to a primarily urban setting then carbines would be issued. another option would be to increase barrel length from 14.5 to 16.5 inches that would help with velocity of rounds. Of course I say forget the whole hollowpoint ban and issue Barnes tripleshock ammo. There is better ammo but we are restricted due to Geneva convention.

  4. Robert is spot on, and yes someone is working on this. I believe money will be the biggest hurdle, and the cost of buying new mags, and parts is gigantic. I believe for the money reason alone the AR/M4/M16 platform is here to stay, until someone effectively bridges the gap. As much as I think the guns trying are cool, the IWI Tavor and others do not share enough parts just yet, nor are they light weight.

    Speaking of weight, the ammo weight is a big deal, and that is why you have seen all these “wild cat” cartridges come to market. On the rifle end I like the 6.5 Grendel best, but the mags need to be changed. The 6.8 spc has mag issues too. The 25-45 Sharps looks promising, but it too needs more time (and I wish it performed like the 6.5G). All three of these are light recoiling, and ballistically better than 5.56×45.

    On the CQB end, we have 300blk, 458 SOCOM, and 450 bushmaster. All of which use a standard mag fairly well with minimal, to no, part replacements (of the mag). Of those three, 300lbk is a bit more versatile than the other two, and weighs a whole lot less.

    I bet the future looks like the 25-45 Sharps and 300blk, but that future is as far off as our supply of 5.56×45. Oh and Troy I totally agree, lets start shooting people with more humane bullets.

  5. the M16 and M16A1 seemed like pretty short rifles back when I was Airborne. It seems rather short sighted to adopt only short barreled weapons because you might run into urban combat. Most infantry actions throughout history haven’t been house to house. In WWII infantrymen used the M1 in house to house combat. M1s are a lot longer than M16A2s. Have to give the USMC the thumbs up for this one.

    1. The first few times I did FIBUA training I was carrying an L1A1, which is a good bit longer than an M16. We managed. Short barrels are nice to have but a long way from essential, and personally I don’t think the loss of range is a reasonable price to pay.

  6. Realistically, the whole ballistics picture has changed dramatically since the M16 was introduced 50 years ago. The 55 grain bullet fired out of a slow twist barrel of 1/12 or 1/10 would begin to destabilize after 250 meters which was ok for jungle fighting. Today the m4’s 14.5 and 16 inch barrels have a 1/7 twist rate that stabilize much heavier bullets out to longer ranges. We have 4-H high school shooters using 16-inch barrel AR15’s scoring very high at 600 yards using 75-80 grain match bullets. The U.S. Military has gone to a 77 grain open tip match bullet as its latest combat round for the M4 that should be plenty good for any situation short of distances requiring a trained sniper. At ranges under 600 yards with the 77 grain ammunition the advantage of a M16 over a M4 are negligible. What the military needs to spend money on is more marksmanship training.

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