piston – Firearms4u

January 4, 2011

AR-15: Handguards and Barrels

Recently a friend asked me a few questions about an AR-15 he was considering for purchase. It prompted a lengthy response on my part that I thought would be good to share here. The rifle in question was a Smith & Wesson M&P15PS, which is a piston carbine with traditional carbine-length handguards. Here is a summary of his questions:

Do you know if it’s possible to put a longer handguard on a carbine setup? The handguard always look so short which seems to be bad for retention and also for possibly burning your self or resting it on something… I would like to put a longer handguard on the M&P piston one, but would then need to put a rail mount sight further down the barrel do you know about people doing stuff like that?

As you can imagine, I had a few things to say about this setup:

I don’t know much about that particular model but on paper it looks like a decent, relatively basic rifle. I don’t see a forward sling mount and the barrel is the “M4 contour” which I would avoid personally given the relative thinness of the barrel at several points along the barrel. Sure, it probably won’t matter under light use but a medium or heavy barrel will last longer and dissipate heat better, especially under rapid or extended fire.

You asked about the handguard. The standard carbine-length hand guard is 7-8″. Mid-length is usually 9-10″ and rifle length is 12″. Given that this rifle has a piston system you might be limited in what you can do. Specifically, you mentioned concerns for having the hot components touching stuff. I’m not really sure this is something to be concerned about. I can’t imagine ever reaching my hand that far forward while carrying or shooting the gun although I do like the 10″ rail on my SR-556, which covers most of the gas block. Perhaps with your reach it could be an issue but that setup is standard issue for M4 military users (82nd Airborne, Rangers, etc.). You might touch something with the barrel or gas block, but that’s possible with any AR-15.

So, with the gas block you have, there may be no way to put a free-float tube on that rifle without it being some sort of over-size (large diameter) tube. You can of course replace those handguards with anything else that will fit a carbine setup but that will by definition not go beyond the front handguard ring, i.e., not achieve your stated goal.

My preference is and has always been to have a free-floating handguard with an integrated rail system (quad rail). This is because you can attach a sling, bipod or whatever you want and not have it create any stress on the barrel. If you press hard into a sling that is attached to the barrel, you can significantly change the geometry such that your shot goes way left (or right in your case). Same goes for bipod: it can make the POI go high if attached directly to the barrel as is the case with rail systems that simply replace the stock handguards.

The rifle in question looks quite good as a general purpose carbine. Put an optic on the top rail and you are all set. However, you don’t have any mounting points for lights, FVG, bipod, etc. and if you created a sling mount on the hand guard, that would stress the barrel as mentioned.

If this is to be a patrol carbine you have to ask yourself which features are really important. Would you even use a sling? Probably only in a SWAT/HRT role I would think. Same goes for FVG, bipod and perhaps even for a tactical light although I certainly keep one on my AR at all times. Bad things don’t always happen in the daylight.

Lastly, you mentioned the need to place a front sight further down the barrel if you covered or otherwise compromised the existing front rail, right? Be aware that this would only be ideal if the sight is rigidly attached to either the barrel or a free-floating handguard. In other words, if you cover that existing gas block with some sort of after-market extensions, they may not be rigid enough (mounted in the handguard rings) to keep zero with the new front sight. The plastic handguards don’t usually have to be held very tightly in place.

So, I would say that it is probably hard to go wrong buying any M&P product but depending on your intended purpose this particular model might be too much of a compromise. Then again, it might be perfect as a light, simple, accurate piston gun. Only you can determine that.

Well, you knew you would get an earful, didn’t you? 😉 Darn it, I need to get back to my blog!

And so I have.

October 8, 2010

Sig556 and Sig522: a comparison

I recently had the chance to check out a Sig522 rifle, owned by my friend Dashiell. While I was evaluating the rifle it was pointed out that our friend Bill had the Sig556, on which the 522 was modeled. Wouldn’t it be interesting to look at them together? Shazam! It was done.

I had both rifles for a week, during which time I shot them both several times, separately and together. What follows are my thoughts on the subject.

But first, some current events…

There is quite a trend lately by firearms manufacturers to build copies of their battle rifles chambered in .22lr. It seems to me that two things are driving this. First, a .22lr version is cheaper to buy and much cheaper to shoot than a 5.56/.223 version and second, the brand name and the form factor attract many folks who might not be nearly as excited by say a Ruger 10/22, which is arguably the best all-around .22lr rifle currently in mass production. Speaking of Ruger, even they have succumbed to the allure by producing the SR-22, which at its core is in fact a 10/22. Here’s how they summarize the rifle:

“The final product is an affordable, feature-loaded rifle that faithfully replicates the AR-platform dimensions between the sighting plane, buttstock height, and grip. Although it looks really cool out of the box, there is an extensive array of accessories available allowing a custom configuration, limited only by the shooter’s preferences.”

The SR-22’s internals are pure 10/22 but wrapping it in an AR-15 “skin” is apparently a marketing requirement. Well, it wouldn’t be the first time that companies have jumped in like Lemmings to the sea, but perhaps there’s more to the story. After all, buyers aren’t foolish enough to buy a $400 rimfire rifle just because it “…looks really cool out of the box…” would they? OK, some undoubtedly will, but there’s more to the story I think.

Stay with me for a minute.

The Sig556 is an export version of the Swiss SG-550 military issue rifle. Actually, Sig has based enough of its business here in the US to establish themselves as a US arms manufacturer, so technically the rifle is not an import for us. The parts however are mostly from Switzerland and Germany.

I found the rifle to be a great handling weapon. It is a bit heavier than a standard M4-style AR-15 but lighter than my Ruger SR-556. It feels really solid. The rifle uses standard AR-15 magazines. (I used stanag and PMags without issue) The trigger was adequate but had a long take-up and reset. I suspect one could get perfectly accustomed to shooting this rifle and the ergonomics were great except for the safety. It is simply too far forward to reach with my thumb unless I un-shoulder the rifle and twist my hand 90 degrees around the pistol grip. I found it much simpler to use my index finger to operate the safety on the right side (strong side) of the receiver. This is not easy to do after being so accustomed to the AR platform. In fairness, it is much easier to operate than say an AK-47.

The setup of Bill’s Sig556 included an optional fore stock with small rail sections. This allows quick-disconnect sling mounts, etc. The rifle also sports a nice CompM3 battle sight, which is awesome. All this works just fine for me except for that darned safety. Shooters with larger hands will have no problem however.

With this rifle’s long-stroke piston, solid design and manufacturing, and the Sig reputation for quality, I am certain this gun would be a reliable weapon. For shooters with smaller hands it might be problematic however.

One functional issue I must mention is that the rifle is tough on brass. At first I couldn’t find my spent casings. After several minutes of looking further and further afield, I found them about 30 feet away at about the 1 o’clock position. The gun does have a gas adjustment so perhaps this could be dialed down a bit to keep the brass closer and more at the 3 o’clock position. I didn’t want to mess with Bill’s setup so I left it alone but I will say that every single case (a couple different factory loads and several different handloads) was dented significantly in more than one location on each. As a reloader this is a major concern. I would not reload these cases. Some would, noting that a full-length sizing die would do much to restore the case to its original dimensions. Nevertheless I suspect these dents would not be fully removed. Some were worse than those in the included photo. Given the tremendous stresses these cases endure, I would not feel comfortable reloading the brass coming from the Sig556. Of course if you don’t reload then this is irrelevant.

Three_Down — Ruger SR-556, Sig556 and Sig522

OK, so the Sig556 is a nice gun. But what about this .22lr version? Glad you asked. The Sig522 is a very interesting firearm to me. Leaving aside it’s pedigree, it is just a fun gun to shoot. The included mag holds 22 rounds of .22lr and with the weapon’s heft (slightly less than the Sig556) there is essentially zero felt recoil. I had intended to shoot only about 100 rounds and before I knew it I had burned a whole brick! This is of course the beauty of .22lr. All this for about $16. With the rifle’s top rail the installation of optics is easy and then you’ve got a pretty close replica of the Sig556. So, why have this thing?

I think that aside from pure cool factor, there’s a very good reason to have the Sig522: for training purposes if you happen to already shoot the Sig556. Perhaps it is obvious to others but this was a novel idea for me. Training with .223 rounds can quickly become a very expensive proposition, but if a shooter with a Sig556 wanted to get in some trigger time on the cheap, the Sig522 would work nicely as a substitute. This is particularly true when the actual shooting isn’t the most critical component of the tactical training. For movement drills, room clearing, stacked approaches, etc., this rifle would allow the same muscle memory development as the 556 and would even allow the trigger pulls, but without the cost associated with the 5.56/.223 rounds. Is this ideal? Probably not, but it beats dry fire drills or simply not training.

So, in summary I like both these guns and I think the 522 is a good replica for the 556. I can’t say that I would go buy either of these guns myself, especially with the safety location on both, but I can appreciate what others like about them. I will say that if push came to shove I would not hesitate to depend on the Sig556.

July 29, 2010

Ruger SR-556: my latest AR-15

With Ruger’s foray into the AR-15 market, many have taken notice. Some because Bill Ruger always said there was no reason for civilians to own “high-capacity” semi-auto rifles. Others because this seems like an awfully late arrival to the party. After all the noise died down we discovered that the rifle was in fact a very nicely built, well-appointed, great shooting gun. I tried shooting one twice and was very much impressed. When it came time for a new AR-15 it was the obvious choice to me. Yes, I really wanted the Masada/ACR but we know what happened there.

I got my SR-556 from a local dealer at a very good price then installed my Magpul CTR stock, GripPod forward vertical grip/bipod, sling mounts and the Aimpoint CompM3 and away we went. The gun is awesome. The weight at 8 lbs unloaded is a full pound heavier than my Bushmaster but this is to be expected with a piston system and a 10-inch quad rail. I think you get what you pay for with weight. This is “good weight”, so to speak since I would want a quad rail anyway and the 2-stage piston system is superb.

I don’t notice any difference in the recoil impulse from any other 5.56 AR-15. Also the inside of my buffer tube shows no signs of the dreaded carrier tilt problem. In fact I can’t see any markings at all in there. After about 1k rounds the gun still shoots beautifully. My accuracy using the CompM3 is dependent on my vision, which is simply not that great. I can get 2″ groups at 100m from the bench, which frankly is better than I’ve ever done before with those optics. At 25m all five shots touch so I’m very happy. With a scope I suspect one could do much better at distance.

The gun runs very cool and clean. Yes, I can touch the bolt carrier immediately after a mag dump. The upper receiver, bolt carrier group and the chamber appear almost as if the gun hasn’t been fired. This is just amazing and very welcome compared to the sooty mess that is the normal direct gas impingement system experience. The only “gotcha” is that the gas block, piston and regulator valve do in fact get quite dirty. The good news there is that they are very easy to disassemble and clean. This contrasts sharply with the usual AR cleaning regimen.

I personally do not like the Troy Industries rail covers as they make the quad rail too big. I really like the Ergogrips Low Pro rail covers for taming the quad rail. They make it really comfortable to grip, they protect your weak hand from getting cut on the rail edges and they cover up those annoying white indexing labels on the rails.

ruger sr556 — Ruger SR-556 stock configuration

I also am not a big fan of the standard M4 buttstock. I hate when they rattle and I don’t like the lock release because it is so obtrusive. The Magpul CTR is the best stock I’ve ever used for a multi-use carbine. It locks up solid, there is nothing on which to snag clothing or other material, it has a built-in quick-release sling mount and it is beautiful to look at. This is essential kit for any AR that I own.

The Hogue grip is just wonderful. I really like how sticky it is. I have not noticed it catch on clothing or tactical vest but it does provide a very solid connection between my strong hand and the rifle. I would not change it.

As I’ve already mentioned the Troy battle sights are outstanding. I had originally intended to swap them for Magpul MBUS sights but when I tried the Troys I was hooked. Also, they are just as light as the MBUS sights. No-brainer there.

So my initial impressions of the SR-556 are very positive. It is everything I love about the platform without the thing I disliked the most: the DI system. I expect I will have this rifle as a permanent member of the collection.

UPDATE Fall 2010: I’ve lately switched to the Eotech 5.12 over the CompM3. Also, I neglected to mention the sling, which is detailed here.