So you're really saying you think that the AR manufacturers are keeping everyone in the dark about how to make their products work? What's their motivation for doing something like that?
This is a question that has a very broad reach. I decided to search just what ammunition AR manufacturer's recommend and what ammunition they do not. Given a few web searches is very easy to find all sorts of ammunition warnings for AR15's.
This is from the DPMS web page:
DPMS Ammunition warning
After extensive testing, we have found that only ammunition manufactured to SAAMI (Sporting Arms and Ammunition Manufacturers Institute) specifications is reliable in DPMS rifles. DPMS recommends the use of high quality, domestically produced ammunition for best results and highest accuracy. For plinking and practice, we recommend only domestic, commercially manufactured ammunition. Please note: the use of hand-loaded ammunition voids the factory warranty. The use of all ammunition listed below also voids the warranty.
We have incurred feeding problems with the following:
• Israeli ammunition
• Korean ammunition
• Chilean ammunition
• Portuguese ammunition
We have reviewed several reports, from several manufacturers', regarding problems using this ammunition. The problem appears to be the bullet contour and the overall length of the cartridge, which is contacting the rifling before firing. This is creating a gas port pressure and chamber pressure higher than recommended, therefore causing feeding and extraction problems due to the increased bolt carrier velocity. In addition, there is accelerated fatigue on internal parts. There are also indications that brass may be out of spec, which could create an unsafe condition.
• South African produced surplus
We have used this ammunition in the past for testing purposes and found the brass is extremely soft and can "flow" into microscopic pores and grooves in the chamber creating "sticky" extraction. This has been reported in many types of rifles, but is more prevalent in semi-automatic weapons.
• Lacquer Coated Ammunition or Steel-cased, lacquer coated ammunition
• Silver Bear
• Any steel-cased (coated or non-coated) ammunition
The problem with this ammunition is that the lacquer coating on the case. As the barrel heats up, the lacquer turns to a soft, varnish substance and upon cool down, becomes very solid and difficult to remove. This effectively creates an undersized chamber and creates understandable problems.
Your rifle is an investment and it only makes sense to choose quality ammunition for a quality rifle!
This is from the Olympic Arms web page:
About Ammo - Warning! by Thomas Spithaler
Information About Types Of Ammunition
This warning comes based on an increased volume of customer calls regarding feeding and ejection malfunctions of AR-15 style rifles. Further investigation of these situations came to prove that the vast majority of these malfunctions were based on ammunition, and not the firearm itself. Following is some of the information that have compiled based on this investigation.
Lacquer Coated Ammo
If you plan on using lacquer-coated ammo in your Olympic Arms AR-15, please be aware of the following. We have received many recent phone calls, as well as some rifles sent in for repair, complaining about reliability problems in their Olympic Arms AR's. The first question usually asked is, "What ammunition are you using?" The answers to the question, as well as seeing the chambers of the rifles that were sent in are showing us that lacquer coated ammo is clogging the chambers badly.
What we are seeing is that once the chamber in the rifles gets hot, it is melting the lacquer off of the casings, and leaving a gelatinous goo in your chamber. Under continuous fire, this is usually not noticed, but once you stop, the barrel cools, the lacquer sets and you now cannot chamber and/or properly extract your ammunition. You will experience this in AR-15's much more frequently than other rifles such as the SKS and AK/MAC variants. In most cases the 7.62x39 rifles have chambers cut to the large end of the safety spectrum so that feeding and reliability is uncompromised by the type of ammunition or the consistency of the case dimensions. AR style rifles, and especially those from Olympic Arms will have tighter chambers so that you can experience a greater level of accuracy that these rifles are capable of performing. Olympic chambers specifically are cut to 5.56 NATO specs via Clymer reamers in all button rifled barrels, and minimum SAAMI spec .223 Remington on all SUM Ultramatch barrels. Our rifles will provide superior accuracy, partly based on that fact.
Our recommendations: DO NOT USE LACQUER COATED AMMO. Otherwise, be prepared for the consequences. Additionally, most lacquer-coated ammo utilizes steel cases instead of brass. BAD FOR YOUR CHAMBER.
The Consequences: Poor feeding, poor extraction, poor accuracy, and an impossible to clean chamber possibly resulting in a rifle that simply does not work.
Although Olympic Arms only warrants their firearms when used with new production brass cased US manufactured ammo, we would be remiss to think that the bulk of our customers do not use remanufactured, imported or reloaded ammo. We know that they will, and do. The reason that our warranty does not cover the use of this ammo is as much to protect you, as it is our product and our product. If you are using factory US new manufactured brass cased ammo, and something goes wrong and the rifle is damaged, the ammo manufacturer will usually take care of any repair costs. If not, and the damage can be proven to be the fault of the ammo, you have some sort of course of action you can take against that manufacturer to recover some or all of the expenses of the repairs. If you use foreign lacquer coated ammo as an example, you have NO options.
Is your rifle worth it?
I'll make this brief. For the reloader, Winchester brass is usually not the first pick. It's not mine. But until recently we have had no problems with Winchester ammunition. As of late however, we have been seeing a great many problems related to oversized brass and blowing primers. Please take this warning seriously. We have nothing against the Winchester company, as a matter of fact we had used Winchester ammo for years as our official testing ammo, but there seems to be a large batch out there that simply does not work well.
Recommendation: Stay away from Winchester ammo, unless you are getting the really good match grade stuff, at least for now.
What ammo should I use?
We recommend that you use brass cased domestically produced new production ammo only. There are many manufactures and types of ammo that meet these specifications, so your options are large. But remember this, any autoloading rifle is only as good as the ammo and magazines you use in it. I will never understand why a person would spend $800- $1,000 on a new firearms, and then go out and buy a whole case of the cheapest garbage ammo he can find, and then complain because his rifle does not work properly when firing it. To me this is a bigger mystery than Bigfoot or the Bermuda Triangle. Use junk ammo, get junk results. Use quality ammo, get quality results.
Fine Print Warning!
We have all heard this before, but it applies here as well; always read the fine print. There are several well known manufacturers of ammunition that also sell ammo that is manufactured over-seas and then imported to the US. Additionally, most major manufacturers offer "less expensive" lines of ammunition bearing their factory names. I will not single out specific brands other than the Winchester which has caused many a problem, there's no getting around that.
The thing that these major brands have going for them is the name recognition. People see names they recognize, and they buy the ammo with confidence thinking it is a good quality ammo. But the fact remains, that this is not always the case. CHECK THE FINE PRINT!
I have some ammo in my hand, sold under a major brand name label. I have 6 boxes of ammo, all from the same manufacturer, and they manufactured in 5 different foreign countries and imported back into the US. Italy, R.P. (Haven't figured this one out yet), RSA (Republic of South Africa), R.O. Korea, are all represented on this list.
Again, BE CAREFUL, and READ THE FINE PRINT!
So what is quality ammo?
Here is a short (incomplete) list of quality ammunition in no particular order:
Ammunition that has been used by Olympic Arms as test fire ammo Ammo that may cause reliability problems *
Black Hills (new production)
PMC (US Manufactured only)
Remington (new, non-UMC brand)
American Eagle Wolf (lacquer coated types not recommended)
PMC (imported ammo only: READ the fine print)
Reloaded ammo if not properly re-sized
Winchester (imported only: READ the fine print)
* Based on customer reported reliability problems
What becomes apparent is that the AR15 is very picky about its ammunition. It would be interesting to research the ammunition recommendations of all AR15 manufacturer's and see if cumulatively, that all brands of ammunition are not recommended. I searched for similar warnings for the AK47 and found basically nothing. The difference in complaints is striking. An AK47 will feed and extract basically anything it can chamber. It has zero problems with steel case ammunition.
What this shows is that the 7.62 X 39 cartridge is a well analyzed and well developed cartridge. The Soviets obviously looked at different case materials, different tapers, different powders before base lining the cartridge. The AK47 was chosen after a competition of designs and then underwent years of development where top designers picked through the mechanism eliminating failure mechanisms.
From what I can tell, the 223 round was a wild cat and the M16 was adopted after a watermelon shoot. Once quantities were issued in combat, the accounts of early M16 malfunctions would fill a book (if they were not classified) and hundreds if not thousands of Grunts died clearing jammed M16’s.
While the mechanism was improved, there is only so much that can be done once form and fit are fixed. So it is no wonder that the modern AR15 does not handle steel cased ammunition. The cartridge and weapon were an immature design and today its lack of development is still apparent. From web accounts it even has problems with brass cased ammunition:
Problems with sticky extraction of REM UMC ammunition
Steel case ammunition has been particularly troublesome in this mechanism. As an example, at this link, the OP added pictures of as extractor rim torn off a brass case when it was chambered in a rifle which had been fired with steel case ammunition.
The authors of this DTIC were researching a problem I have not encountered: extractor lift.
Understanding Extractor Lift in the M16 Family of Weapons
The report begins:
Several theories for explaining extractor lift and failure to extract in M16 family weapons have been proposed.
If you notice, for maximum extraction reliability the Army had to lubricate the case:
For shot #7, the (lubricated ) case coasts along behind the bolt when the ejector is not present, allowing the extractor to lift and then return to the case rim
The report conclusion is:
Extractor lift occurs during the initial rearward translation of the bolt after bolt rotation stops.
Case extraction and ejection successfully occur as long as the case is held against the bolt face by the residual chamber pressure while the extractor lifts and returns to position.
To hold the case against the bolt face the authors found they had to eliminate chamber to case friction. Even a dented case had enough friction to create a failure to extract.
The AR15 had issues with South African military brass cased ammunition: We have used this ammunition in the past for testing purposes and found the brass is extremely soft and can "flow" into microscopic pores and grooves in the chamber creating "sticky" extraction.
The South African Army uses a licensed variant of the Galil, http://en.wikipedia.org/wiki/R4_assault_rifle
obviously this mechanism is more tolerant of ammunition differences than the AR15 mechanism.
Considering all the posts of the issues shooters have had with steel case ammunition, I think it is not a bad practice to lube your steel case ammunition. While this is a band aid cure, something to rectify an intrinsic design defect by an operational practice, oils will break up the fouling associated with steel case ammunition, will break the friction between case and chamber, and as messy as this practice may be, it will keep the mechanism functioning longer between jams.