5.56 Timeline

Silencers and Semi-autos – A Parable

Imagine that you have a friend who is ready to buy his first AR15. Instead of following any reasonable advise, they go to a gun show and buy a random AR from one of these fly by night companies no one has ever heard of before or will hear of again.

Then they have some issues. Not being the sort to just settle, they work them out. Now your friend goes online and is is an “experienced expert” on the AR15. They go into great detail on how you have to take the gas block off and open up the gas port with a drill to get the gun to be reliable. How you need to take a file and open up the back of the mag well so that magazines will seat correctly. How there are so very many things you need to do to make an AR15 a reliable combat worthy firearm.

You try to tell them that none of that would have been necessary had they bought the right AR15 to begin with, but instead they insist that this work needs to be done to ALL AR15s.

Wouldn’t that be pretty damned infuriating? In the good ol’ days you might punch a man in the face for being so obstinately wrong, but we are more polite than that now.

There are people out there who claim that you have to use an adjustable gas block with a silencer. That all silencers cause excessive back pressure. That you need to switch buffers or change the gas system when running a silencer on an AR15.

This isn’t a matter of someone buying a cheap junky silencer to put on a cheap junky rifle, this is a matter of compatibility. Someone can buy a top of the line silencer and throw it on a semi auto and run into issues because the silencer was designed with bolt actions in mind. It might be the best silencer to put on a bolt action, but no consideration was made as to back pressure with that design. So when they throw it on a semi-auto, suddenly they have an over gassed gun. Now this expert tells everyone that every silencer will cause an over gassed gun. No, your bolt gun silencer will cause an over gassed semi-auto.

I saw a post on a forum today where someone was wanting to suppress a standard M4 configuration AR15. They said that they knew that a mid length 14.5 would be better for being silenced (WTF did that come from? Someone show me the research that says that.) This person was worried if it would even work at all, or if they would have to get an adjustable gas system and tune the buffer weights, etc.

Fortunately several people responded that they had the same setup and didn’t have to change a thing.

Yes, all guns can be tuned and improved, and that isn’t what I am talking about. I’m talking about those loud mouthed know-it-all’s, that once tried to make a soup sandwich and failed, that now claim that all sandwiches are bad.

Understanding the USMC new ACOG reticle

The Marines started using a new ACOG reticle in the Squad Day Optic (SDO) on the M249 Squad Automatic Weapon (SAW). That optic got moved to the M27 IAR when the USMC switched over, and now the Corps is having the 4X Rifle Combat Optics (RCO) scopes get this reticle.

Simple, right? Pretty much self explanatory. I feel like I would be insulting your intelligence to explain how to use it.

But, just in case you weren’t clear how to use it, I’ll explain.

First, back ground info:
M249 SAW has been available in various barrel lengths. I’ve seen different numbers thrown around, but 16.3 and 20.5 inches seem to be the official lengths.
The M4 and M4A1 has a 14.5 inch barrel, and the M16 series of rifles has a 20 inch barrel.
M27 IAR has a 16.5 inch barrel.

Previously the USMC fielded two different ACOGs, the TA31RCO-A4 (AN/PVQ-31A) and TA31RCO-M4 (AN/PVQ-31B) for the 20 inch rifle and 14.5 inch barreled carbine respectively.

There is a rumor that Trijicon used the same BDC in each scope, but I don’t believe that. I do know that back in 06-07ish, higher ups in the USMC claimed that the scopes were interchangeable. I think that it shows that the level of precision considered acceptable by the USMC allowed either scope to be used.

The SDO optic, adopted for the SAW, needed to be able to work for either barrel length. It used this reticle with green illumination.

Blah blah blah, let us talk about this reticle. I could type up an explanation, but it would be easier for me to copy and past from the USMC own Squad Weapons manual.

First Zeroing:

Ideally you zero at 300m using the tip of the post. If not that, then use the top of the dot at 100m. Reduced range zeroing can be done using the tip of the post at 33m/36 yards for the M16.

Unlike the RCO models which had a Chevron and Bullet Drop Chart (BDC) that went out to 800m, these have a BDC that goes out to 1000m.

Note the narrower lines below the marked lines. We will come back to that in a moment. Those are important.

Ater the 500m line, instead of using a line to cover your target to estimate range, the SDO reticle has a gap. You fit the torso of your target into these gaps to find the distance to them when you are using the 600-1000m section of the reticle.

What are all these smaller lines below the BDC range lines?

As previously explained, we have these 14.5-16.6 inch barreled guns, and 20-20.5 inch barreled guns. The lower smaller line is for the ballistics of the shorter barrel.

This scope had a BDC for the rifle and the carbine (or the Para-SAW and the standard SAW). This lets the USMC have a single ACOG that can work on the M4/M4A1, M16A4, M249 (regardless of configuration), and the M27 IAR.

I’ve shot out to 1000 yards (~914m) with an ACOG and it is far from ideal for that job. But it is far better than using iron sights at that range. While stuffing a 1000m BDC in an ACOG may be idealistic for the one shot one kill rifleman, it very useful tool for the automatic rifleman’s suppressive fire. It is better for our troops to have it and not need it, than the other way round.

Thanksgiving Plinking

Went to the range today. Hadn’t shot shotgun in a while and was starting to grow fond of them. A few shots reminded me why I don’t care for them. Low capacity, slow to reload, etc. Still worth having one.

I received a Geissele Super Dynamic 3 Gun trigger (SD3G) in that Larue PredatAR rifle I talked about recently. I replaced it with a Larue MBT trigger in that rifle. I am going to sell this trigger, but I figured I should it before I do. In the past, when I used a Super 3 Gun trigger (S3G) I found it so light and the reset so short that I was inadvertently getting double and triples when I didn’t want it. That happened with two different lowers, so I quickly got rid of the trigger. Trying this one in one of those same lowers, I had no issues with unintentional bump firing. Geissele’s “3 Gun” triggers are very light, short trigger, and very quick to reset. It makes for a very easy to shoot fast firing gun, but I’d rather have heavier trigger for any gun that I would expect to use for any serious or dangerous work. Still, something like the S3G or SD3G triggers would be perfect for the gun games they are designed for. The S3G has a standard curved trigger, while the “Dynamic” SD3G has a straight trigger.

I’ve started playing around with the Magpul 40 round Pmags. Initial impressions are excellent. They are easy to load, smooth to use, standard Magpul AR15 Pmag excellence. I expected they might be so long as to be awkward but I was wrong. As of now, I would wholeheartedly recommend them.

Field // Pins, another product I don’t get.

Some company is letting you preorder field pins. They have some renderings of the product you could preorder. These “Field // Pins” are a take down and pivot pin for the AR15 with slots in the head that you can hook the rim on a round to pull open.

I don’t get it. If I have a round, why not use the bullet tip to push out the pin from the other side?

I thought, “Maybe it is to prevent scratching or marring your pins?” But I think the brass rims will mark up this pins just as much as push the pin.

Adding style an ease to a part most don’t think much about till it’s time to use. Field Pins are designed to use the rim of your cartridge to easily pull if need be. No more jamming your finger nail, using a pin and hammer, or using the actually bullet tip to disengage your takedown pins.


I think their first two words explain the whole arguement for this part. “Adding style” is probably the only real justification for these. For the people who want a Gucci rifle.

This just doesn’t seem like an upgrade in any way to me. Not worth $45. But hey, there are worse ways you could spend your money.

I don’t get it, a QD MLOK handguard

Tactical Machining has come up with a quick change handguard system for the AR15.

Product link https://www.righttobear.com/product-p/10500.htm

Not a quick change barrel, but a quick change handguard.

You know, for all those times when you wanted to quickly change out handguards.

A low cost light weight handguard is great. But I just don’t see the need for a quick detach handguard.

Are you going to need two different handguard lengths and the ability to rapidly switch between them?

Now back in the day, I rarely heard of people getting an extra KAC RAS lower handguard so they could switch between one that was slick and one that had a vertical forward grip.

But it doesn’t really take long to take off most forward grips from a piccatinny rail. There are some that screw on and the Tango Down grips can be very hard to install and remove.

I think this QD handguard might be a solution to a problem no one asked about. But I do think it also shows what I have been saying that MLOK and Keymod accessories lack the quick detach ability we had gained with piccatinny rails.

Some people have difficulty installing and removing MLOK accessories. With with these handguards getting slimmer and smaller, it becomes harder to install MLOK accessories because of the protruding screws. I am told that the MLOK LMT monolithic chassis, for example, can not have the barrel removed when MLOK accessories are installed. Being able to remove your handguard would make it easier to install accessories.

Still, with out a QD barrel, is it really worth having a quick detach hand guard?