The scoped carbine, an outline and ammo/optic considerations

A guest article from David Gheriani a Vortex sponsored PRS and Precision Carbine shooter

The scoped carbine, an outline and ammo/optic considerations

When it comes to scoped carbines there are tons of acronyms and abbreviations floating around: DMR, SPR, Recce rifle, etc. So what is a scoped carbine? In this context we’re simply talking about a semi-automatic, magazine fed rifle of an intermediate caliber (think .223/5.56 or 7.62x39) with some kind of magnified optic and generally in a non-restricted barrel length (ie 18.5”+). The kind of rifle most people will put a red dot on and never shoot past 200 yds/m. In reality, these rifles, in the hands of people who can properly apply the fundamentals of marksmanship and with a basic grasp of ballistics, are generally capable to 600 yds or so with the limitation being more the type of ammunition and the optic than the rifle itself.

How does ammo choice help you stretch your carbine out to distance? Well, generally speaking, match ammo (68/69gr or 75/77gr) tends to shoot more precisely (ie smaller groups) than does standard “ball” ammo like 55gr M193 or 62gr M855. That’s because the ammo is both loaded more consistently and because the bullets themselves are more consistent and designed for precision. Furthermore more, those heavier bullets have a higher “ballistic coefficient” which is really just a way of saying that they perform better in the wind. So what does that mean for increasing your range? If your rifle groups “ball ammo” into 4” (roughly 4 minutes of angle or moa) at 100yd/m that means that it will group 20” at 500yds (which is wider than a full-size IPSC target). If shooting match ammo reduces your group size to 3” or even 2” it would then be grouping 15” or 10” at 500yds ( 3 or 2 moa). As can be expected, this increase in precision will drastically improve your hit probability. The improved “bc” comes into play as you stretch the range out because it essentially gives you more room for error when making a wind call. I won’t get into the math but generally speaking 75/77gr ammo will drift 1.5”/mph of wind less at 500 yds than will 55gr ammo. That doesn’t seem like much but when you think that the best wind callers can generally call the wind to 2mph in field conditions you can see how that could help with making consistent hits on a 12” target at 500 yds. Engaging targets at 500m is very possible with “ball” ammo but optimizing your ammo selection will improve your ability to make consistent hits, especially on smaller targets.

When deciding what type of optic to use its best to keep in mind that everything is a compromise. Here’s a quick rundown on possible optic configurations and their pros and cons with regards to shooting to further distances.

Red dot with a magnifier:

This is probably the most simple optic setup to step into as many people will already have a red dot on their rifle. The addition of a magnifier simply allows you to see greater detail and therefore shoot at targets at ranges that you otherwise couldn’t properly resolve them at. Although 3x magnifiers have long been the standard, there are many 6x magnifiers available these days and I would highly recommend going that route instead of getting a 3x. With a 6x magnifier behind a simple red dot and an understanding of your bullet’s trajectory you can be making consistent hits at 400yds/m. Beyond that it becomes quite difficult to be consistent as there is no longer much reference in the optic to properly hold over. Red dots with multiple dots (such as the Eotech XPS or EXPS 2-2, 2-4, 3-2 or 3-4) give you additional points for holding over and generally allow you to extend your range to 500 yds/m so long as the wind is relatively mild (as you have no points of reference for wind holds). 

Fixed magnification prismatic scope:

This type of scope was the optic of choice (and still is) for many military issue rifles. The Acog and Elcan in all their varieties are quite well known for being robust and having nice glass. This class of optic is normally seen with a 4x magnification level and a BDC (ballistic drop compensation) reticle that is matched to some flavour of issued ammo with elevation holds out to 5-600m. Although the elevation holds on the reticle might not line up perfectly depending on what type of ammunition you’re using, you can figure out how they match up to your real world holds and be quite effective out to 5-600yds/m with the limiting factor being the size of the target and whether or not it is out in the open or somewhat obscured. 4x is not much magnification so it can be quite challenging to resolve smaller targets or those that are in the shadows or just not obvious. Furthermore, it can be very challenging to spot the “splash” (ground disturbance from the bullet’s impact) when you miss with only 4x of magnification and this makes it difficult to make the necessary corrections for misses due to an incorrect wind call.

Low power variable optic (LPVO):

LPVOs are one of the most popular types of optic these days and are possibly the most versatile when it comes to a scoped carbine. By definition they are a scope that has 1x magnification (ie no magnification, like a red dot) on the low end and 4, 6, 8 or now 10x on the top end. They combine the speed of a red dot on 1x and the magnification of a “regular” scope at the higher magnification levels. They can be had with many different reticles, be it BDC or with mo or mad sub tensions like any other tactical/target scope. The thing to bare in mind with LPVOs is that the higher the max magnification is the greater the technical challenge for the manufacturer to build it and that either results in poor resolution or clarity at max magnification as well as a tighter “eye box” (essentially requiring very precise placement of the eye behind the optic) and a tighter field of view as well as increased cost. For someone wishing to extend their engagement range with a carbine while still retaining the ability to use a low end of 1x magnification, there really is no downside to a high end 1-8 or 1-10 LPVO other than cost. They allow you to make accurate holds out to the limits of the cartridge’s effective range where your limiting factors will be the accuracy capability of the rifle and ammo combo as well as the ammo’s ballistic performance. The higher level of max magnification also makes spotting misses (and therefore making corrections) much easier than with a fixed power 4x. The less expensive LPVOs are perfectly serviceable but you just need to understand that for optics of an equal cost, a fixed 4x optic is going to be clearer than an LPVO at 4x and the less expensive 1-6 or 1-8 will be less clear than a similarly priced 2-10x or 3-9x scope at 6 or 8x. Everything is a compromise and there is no free lunch

Medium power variable optic (MPVO):

MPVO is essentially referring to your standard scope that has a relatively low bottom end (think 2 or 3x) and a “medium” high end (usually 10, 12 or even 18x) but optimized for extended range engagements either via target turrets or a BDC or mrad/moa reticle (as opposed to a typical 3-9x hunting scope with capped turrets and a duplex reticle). While they give up the 1x low end of the LPVO they will generally have a larger field of view and better clarity at the same magnification level as an LPVO of the same price. This type of optic is probably the most suited to shooting a carbine out to extended distances with the higher level of magnification making resolving the target and spotting hits/misses easier again. The downsides are the lack of 1x on the low end, a generally heavier weight and a more length/bulk. 

This list is by no means exhaustive but hopefully it’s given you an idea, from an equipment perspective, on how to optimize your typical NR .223 or 7.62x39 semi-auto to be able to extend it’s effective range and what some of the pros/cons of different setups are. Once you have your rifle set up, the most efficient way to extend your effective range is through participation in a course administered by qualified instructors.

Dave Gheriani is an experienced competitor in long range/practical precision rifle and an instructor with Dragon Risk Management specializing in precision/long range shooting.