Selecting Carbine Ammunition

I have read a great deal of discussion on the internet over which ammunition is best for your AR15. Much like pistol and shotgun ammunition, deciding upon a self-defense load is a straightforward task, provided you understand how you need the ammunition to perform. Here is what I feel are the basic criteria for an AR15 self-defense load.

First and foremost is reliability. All the accuracy and ballistics in the world are for naught if you experience a stoppage. To me, this means brass cased ammunition. Like it or not, steel cased ammo causes stoppages in ARs for a variety of reasons. I have heard the argument that if your AR cannot run steel cased ammunition then it is not a reliable AR. I will counter that if your AR runs steel reliably it may likely be over-gassed. I understand being on a budget, and steel cased ammo is fine for plinking or training. But for defensive purposes, I think it is best to stick to brass cased ammunition.

Second would be accuracy. Reliability and projectile performance are great, but if you cannot hit your target it is a moot point. Now, we must be reasonable with our expectations of accuracy. All too often I see people chasing accuracy without regards to the terminal performance of the round. Generally, the loads which produce impressive accuracy at long ranges provide less than impressive terminal ballistics. Not too long ago I attended a lecture put on by the FBI’s Ballistic Research Facility, arguably some of the foremost experts in the field. The presenter was discussing ammunition selection for police marksmen. He spoke at length about misdirected efforts towards extreme accuracy – agencies were chasing half minute groups with match grade bullets which were poor terminal performers, when almost all police marksmen engagements were inside of 100 yards, the majority of which take place around 50 yards. His recommendation was a rifle / terminally effective ammunition combination that would provide a 10-shot group inside of a watch face at 100 yards. While it does not make for very pretty Instagram posts, one cannot help but understand his point. Look at the accuracy requirements for military ammunition lots sometime if you want a further demonstration of this point. Accuracy is important. When selecting a self-defense load you should be sand bagging your carbine and shooting for groups as part of the selection process. But raw accuracy is pointless without terminal effectiveness.

Which brings us to our next point – projectile performance. When it comes to pistol ammunition the gap in performance between ball ammunition and specialized defensive loads is massive. For 5.56mm carbines, the gulf is less pronounced, but it is still there. While ball ammo like M193 or M855 will serve you well in a variety of environments and barrel lengths, consider more tailored projectile choices such as jacketed soft points and  barrier blind loads (rounds which exhibit solid terminal performance even after passing through a barrier such as auto glass). These all merit a look, depending on your intended use. Police agencies should not overlook the use of barrier blind loads, consider how often police involved shootings occur around vehicles. Remember – 5.56mm carbines like the AR are very velocity dependent. A load which excels in an M16A2 with a 20” barrel will likely exhibit significantly different performance out of a 10.3” Mk18. As with pistol ammunition the FBI standards are a great starting point. While the FBI standards should not be considered THE standard, they provide a useful metric because they are A standard.

Availability also plays a major role. If you cannot find the ammo in stock anywhere with any sort of regularity, then it doesn’t matter what kind of wonderbullet it is, as you can’t zero with it or practice with it. Along the same vein is access to ranges where you can shoot your chosen ammo. M855 is certainly available, but many ranges restrict its use due to how hard it is on backstops. Just one factor to consider.

The last item I look at when selecting defensive ammunition is very much subjective but to me it is important. For the AR, there is ammunition in both .223 Remington and 5.56mm NATO available. In an AR15 with a to spec 5.56mm chamber, both can be used interchangeably. Terminal ballistics testing data shows that with proper bullet choice, the differences are allegedly negligible. That is fine. However, I have anecdotally noticed a difference in function. As your carbine gets more fouled, if firing .223 pressure ammunition, it will cycle noticeably more sluggish when compared to 5.56 pressure loadings. Additionally, knowing that this load will likely be shot out of a shorter barrel than it was originally designed (16”-10.3”), I feel more confident in a load that will give me every last bit of performance.

In closing, while ammunition selection is important, its far less important than training with what you chose. It is a rifle and is an incredibly effective tool for self-defense even with less than ideal ammunition. So do some basic research, test it for accuracy, reliability, and function, then get to the range and train, train, train. The shooter who knows his mechanical offset inside and out, though he be armed with Walmart clearance rack ammo, will be far better off than the guy who spent his days arguing with strangers over which grain weight is better. Equipment can provide you an edge, but only through training will you obtain the tools for success.

—Flynn