2Xalpha

Typically people say thinner barrels will have more dispersion as they heat up, but data seems hard to find. Faxon, do you have any data on heat dispersion with the 18" 5.56 Gov't/Socom Rifle Gas barrel? (http://www.faxonfirearms.com/p/98/18-556-ar-15-4150-black-qpq-govtsocom-rifle-gas) If you were to guestimate, how much will the heat dispersion be different from for instance one of your 18" heavy barrels: http://www.faxonfirearms.com/p/106/18-556-ar-15-416-r-stainless-matte-heavy-fluted-mid-gas Mrgunsngear did a short test with one of your 16" pencil barrels where the group seemed to open up from about .75 to 1.25" at 100 yards after a 30 round mag dump, I would love to see more tests like this.

"It's the archer, not the arrow". I think we can agree that, shooting as much offhand as we do in IPSC & 3 Gun, shooter error often will be way more determinantal than the mechanical precision. However it's good to know in the back of your mind that you have a minimum level of accuracy to fall back on when engaging those long range targets. What should one expect, 1 MOA, 2 MOA? And how does that change as the skinny barrel starts to heat up? Probably it sounds like I'm a little hung up on accuracy, but as you mention it's actually more important how many thousands of rounds the barrel will hold its level of precision. I think different steel quality (CrMo 4150, vs. 4140 vs. 416) and treatments (chrome lining, nitriding or cold hammer forged) comes into play.

By DPMS rear sight, do you mean the "FT-RS Detachable Rear Sight"? I've seen some good shooters use it.

OK, I think I've found that the accuracy in the lighter barrels typically will be good enough. The next question is balance. While I want a light rifle, I still want it to balance well. How can I determine the balance with the different parts? Parts list: - Regular mil-spec upper/ lower - ACE ARFX rifle length stock - Handguard choice: Leaning towards AP Custom 15" Ultra Light handguard at 6.2 oz/ 175 grams (http://apcustomusa.com/product/gen-ii-ultra-light-series-carbon-fiber-handguard/) Also consider: - JP 15.5" MK III Modular Hand Guard (JPHG3-6M-RC) at 15.2 oz/ 430 grams (http://www.jprifles.com/buy.php?item=JPHG3-6M-RC), or - JP 15.5" MK III Modular Hand Guard (JPHG3-6M) 18.3 oz/ 519 grams (http://www.jprifles.com/buy.php?item=JPHG3-6M) (weight difference between AP and the lightest JP is 9 oz/ 255 grams) - SJC Titan comp Some barrel examples: - JP 18" light contour 31 oz/ 878 grams (http://www.jprifles.com/buy.php?item=JPSM223-18L8) - BCM 18" 40 oz/ 1133 grams (http://www.bravocompanyusa.com/BCM-18-SPR-SS410-Barrel-with-Rifle-Length-Gas-p/bcm-brl-rec-18ss.htm) (weight difference between BCM and JP barrel is 9 oz/ 255 g) Looking at their location, the different handguards and barrel profiles will approximately have the same impact on the balance.

Thanks, found this one from Faxon Firearms: http://www.faxonfirearms.com/p/98/18-556-ar-15-4150-black-qpq-govtsocom-rifle-gas 18", rifle gas, 1.95 lbs/ 885 grams. Look really cheap at MSRP $179, but how is the quality?

JP says the accuracy of the light and medium contour is the same, they all shoot 1 MOA or better.

So you are suggesting for instance a light contour JP barrel? JP barrels have a very good reputation, but they are a bit expensive. The CMMG barrel was cheap, but the quality probably suffers.. Other good light profile alternatives?

Hi, I want to build a lightweight competition AR, and think about saving some weight going with a lighter barrel. In general I was recommended the BCM 18" as a good value/ quality option (2.5 lbs/ 1133 grams, http://www.bravocompanyusa.com/BCM-18-SPR-SS410-Barrel-with-Rifle-Length-Gas-p/bcm-brl-rec-18ss.htm),but I wonder if I should go with a lighter profile instead. Some other options I've seen: - CMMG 18" (weight?): https://www.cmmginc.com/shop/barrel-sub-assm-18-0-mt-416ss-5-56mm/ - Noveske 18" Lightweight Contour, 2 lbs/ 907 grams: http://www.shopnoveske.com/products/lightweight-5-56mm-stainless-barrel - JP Light Contour, 1.94 lbs/ 878 grams: http://www.jprifles.com/buy.php?item=JPSM223-18L8 Is it dumb to skimp on the weight? Anybody have some comparable data on how much impact might change (I say might, because I guess it will depend on the quality of the barrel)? Will the difference in accuracy be noticeable, especially for the requirements we have in IPSC/ 3 Gun (I guess not)? Again, does anyone have some data? Please recommend some other good value barrels for the build, and comment the ones I've mentioned. The requirements are an 18" barrel with rifle length gas tube, preferably with a good quality/ price ratio.

Also posted on hitfactor.no This article is going to be an overview of the different options on iron sights for the IPSC Semi Auto Standard division and the USPSA Heavy Metal Limited division, which are rifle divisions limited to iron sights only. I found little information about the subject, but hopefully this will spark some intereset and discussion. One of the first thing you hear about iron sights for competition use is sight radius. It's generally desirable to keep the sight radius as long as possible for several reasons, primarily to help focusing. If the front sight is further away from the face, the target will appear less blurry when you are focusing on the front sight for precision shots, and vice versa the front sight will appear less blurry if you are using target focus when blasting at shorter ranges ranges. In addition the sight picture will be perceived as steadier, and any errors in sight alignment will have less impact downrange because of the greater distance between the front and rear sight. To achieve longer sight radius many choose a 20" barrel for IPSC Semi Auto Standard instead of the regular 18". Preferably the front sight should also be attached to the barre instead of the handguard, as most handguards can be flexed to a various degree which will start to have a significant effect at longer ranges. Mainly two types of front sights are used; post sights and globe sights. Both are very precise, and what you like is a lot of personal preference. You will be able to shoot both fast and accurately with each of them, and many have tried back and forth until they’ve found what works best for them. Post Sights JP Clamp On Front Sight Base. Photo: Brownells As in the traditional front sight gas block (FSB), but with thinner post for competition use. Front sight bases usually come with the standard mil-spec post insert which is .072" wide, but at longer distances these cover too much of the targets. Usually they are swapped to thinner posts between .030-050" for competition use. The traditional front sight base is a simple and robust design. For competition use a new front sight may be mounted right behind the compensator to increase the sight radius. “Clamp on” front sights are made for this purpose, attaching by tightening a screw unlike the usual pinned front sight base. Obviously the new front sight can't also function as a gas block due to the location on the barrel, so a separate low-profile gas block (or at least a gas block without a front sight) must be used in conjunction. The biggest pro of this type of sight is the ruggedness, and due to their shape they are less likely to snag when you pull your rifle out of ports etc. The precision is very good. Not quite as good as a well matched globe sight, but plenty for our use. Globe Sight A globe sight on a Schuster sight block. Image courtesy of Flickr user "slemmo" Favored by some Finnish top IPSC shooters, these sights are capable of extreme precision. Sometimes they mistakenly are called diopter sights, because globe sights often are used together with a rear diopter sight for precision shooting. Among the pros of globe sights is that you can choose from a myriad of inserts to find one you like, and they are easy to change. For instance there are very thin or wide posts, large or small circles, crosshairs, squares (!) and so forth. The outer "tube", or globe, protects the inserts well from damage, but also counteracts change in point of impact due to which direction the sunlight comes from. To achieve extreme precision the front and rear sight can be two matched circles with some air in between, while others prefer a thin post which is both very fast at short ranges and also very precise at longer ranges. Some again prefer a crosshair. A pack of Lee Shaver Inserts, Photo: Brownells Among the disadvantages of globe sights is that the globe itself covers more of the targets, but then again the whole outer globe may be used successfully as a large front sight at shorter ranges. Some would argue that they more easily catch on stuff (i.e. in and out of ports) and that they aren't rugged enough, especially for 3 Gun where the equipment is tossed more around. Several different sizes of globes sights exist, mainly the 22 mm is the "new” standard, while many older globe sights tend to be 18 mm. The nomenclature refers to the metric threading of the ring used to fasten the insert. Both types attach to the standard 11 mm rail, same which is found on many "traditional" target rifles such as Anschutz. To get the globe sight high enough above the barrel on an AR, an height adjustable base with an 11 mm rail on top therefore is needed, and there are several solutions available. - JP JPFS-ALS is a kit where you get a 22 mm globe sight, some Lee Shaver inserts, and the most important part which is the adjustable base to achieve the right sight height. The adjustable base is intended for mounting on a picatinny rail, and JP has gas blocks and dedicated sight blocks with picatinny rails available . - Uronen Precision "diopteritähtäimen jalusta": A barrel band with an 11 mm rail on top. Stepless adjustments with no indication, may therefore be a little more hassle to get sighted in, but once it’s set you have a simple and sturdy sight base. Diameter is .725”, included is a Lyman #93 globe, Lyman 17 inserts and some Uronen inserts. Photo: Uronen Precision - Schuster (out of production): A very nice and solid sight block. Standard 11mm rail for attaching a globe sight at the top, gradual adjustment with two set screws for locking. Available in diameters .740 "and .750". - Lipski (out of production): A barrel band (quite similar to Uronen), with an 11mm rail on top and stepless adjustments without indication. The design is simple and solid, diameters are .750 "and .812". - Accuracy Speaks (out of production): Quite similar to Lipski, but with some minor differences regarding adjustment. A possible reason for why so many sight blocks are no longer in production may be that the USPSA Limited division has allowed “one non magnifying optic", which has led to very few still using iron sights. The only USPSA division still restricted to iron sights is the Heavy Metal Limited division (.308 and larger caliber), however internationally the IPSC Standard division continues to be limited to iron sights only. Mounting Whichever type of front sight you choose, mounting it to the end of the barrel may present some challenges. There are many different barrel profiles, so check the diameter your barrel before ordering. In general the most common barrel diameter at the gas block is .750", which gradually becomes thinner towards the end of the muzzle to about .740". The idea behind this is that it should be easier to slip on a gas block, but it can cause us some challenges when trying to mount iron sights out there. If there is a gap between the barrel and the front sight base, one solution may be to use brass shims. Some Rear Sight Options Many rear sights have two apertures of different sizes, one large for short range and a smaller one for precision long range shots. Carrying handle rear sights are rugged, and usually have two different hole sizes that can be easily flipped. Note that some of the apertures will have different zeroes when flipped which may be an advantage or disadvantage depending on use, just be aware. Many replace the mil spec aperture with a national match that has two smaller apertures, and then drill out one of them. A smaller aperture will be more precise, but require more light and therefore become difficult to use when the daylight starts to go away. Click values ​​are also influenced by a longer sight radius, becoming proportionally finer with the increase of the sight radius. If a standard rifle length AR-15 with a front sight at the gas block has a sight radius of 500 mm, and it is increased to 667 mm by mounting the sight further forward, the click values can for instance go from 1 MOA to 3/4 MOA. This starts to eat from the long range capacity of the sights, so if the sights originally could be used out to 600 m you will now only be able to reach 450 m without holding over. Therefore you should choose a rear sight that goes a little further than what you need! Due to range availability we rarely shoot above 300 m in IPSC, but it's nice to have the ability to reach out there. Image courtesy of CO-Exprs, using two flip up sights for different ranges A rear sight that attracts me is the Matech, it has very little occlusion around the rear sight, providing the shooter fast sight acquisition and a good field of view. The rifle in the picture above has two Matech sights, the foremost is drilled up to a larger aperture and is used for short ranges. It is left up all the time, while the rearmost with a smaller aperture is for precision shots, and is popped up when needed. Note however that any flip up sights in general will not be as rugged as for instance a carrying handle. Many are plagued with the double vision experienced when trying to use use iron sights, and the Orlob Rifle Occluder is a gadget some might find handy. It "hides" the front sight from your "non-shooting" eye so you only see one front sight instead of two while shooting with both eyes open. The invention doesn’t look very advanced, so you can certainly try to make something similar out of cardboard before you order it, to see if it’s something that is going to work for you. Orlob Rifle Occluder More on Iron Sights This article has focused on the equipment, but shooting well with iron sights is an art that I hope more people now will try to master (at least I’ve been intrigued). As Patrick Kelley rhetorically asks in his article "The Power of One" from Shooting Illustrated: Why would anyone shoot iron sights “when one can slap on a scope and achieve instant mediocrity”? Well, firstly it is more challenging and thus more fulfilling when actually mastering it. Secondly, you will bring the good habits you learn with iron sights over to optics, and will probably become a better shooter. I mention consistent cheek placement every time, which is a must to be quick with iron sights while one can get away with some errors and still get a good sight picture with optics. Have a look at Patrick’s article for more information and tips on techniques when using iron sights on a rifle. Shooting rifle, it is always important to know your zeroes and the adjustments required to hit at different ranges, but with iron sights it is perhaps even more important. A stage may have a long range target, but due to poor contrast between the sight and target, one must aim somewhere above or below the target to get some good contrast to aim at. Then it becomes handy to have a ballistic table so that you in advance of that stage know how much elevation to dial (mils). Kelley has some examples on the importance of knowing your ballistics, and the only way to find out of your rifle's ballistics is by training and verifying. A ballistic calculator is a good tool, but you still must go out and verify. Don’t be too concerned that for instance the meter marks on the Matech rear sight will become incorrect when you increase your sight radius; you will have to make a ballistic table to suit your rifle and your load anyway. You should have good enough control on the ballistics to know how much to dial as long as the distance is given.

I have an ADM Recon with a height above rail of 1.47" (top of rail to the center of the optic), which I think is pretty common for AR scope mounts. See some data on other scope mounts below. Lots of numbers, seems like there might be some trial and error.. Need to collect some data on how much the different offset mounts effectively changes the height over bore, and compare that to the red dot choice to make an educated guess.. Some common 30 mm scope mounts: - ADM Recon (2" offset, 1.47" height over rail) - ADM Recon X (3" offset, 1.47") - ADM Scout X, (3" offset, 1.47") - Bobro Precision Optic Mount (1.52") - Bobro Dual Lever Precision Optic Mount (1.52") - JP JPFTSM-30/1 (1.47") - JP JPFTSM-30/1E "extended" (1.47") - LaRue SPR-1.5 (LT104) (2" offset, 1.50") - LaRue SPR-S (LT158), (2" offset, 1.44") - LaRue SPR-E (LT139), (3" offset, 1.50") - Warne XSKEL (?) - Warne R.A.M.P (?) - Spuhr SP-3016 (1.46") - Spuhr SP-3026 (1.26") I think mil-spec iron sights typically sit a little lower at around 1.4" over the rail, which translates to 2.6" ≈ 65 mm height over bore (center of bore to center of the optic). Many numbers..

I have a Burris Fastfire III that I want to mount at 45° on my Open rifle. It currently sits in a ADM low profile picatinny mount that I want to keep, so an offset mount with a rail is preferred. The listed mounts seem to give some difference in height over bore, is that an issue? I guess the same height over bore as the scope will be ideal. - Burkett Offset Mount - Daniel Defense One O'Clock Offset Rail - JP 45 Degree Rail Offset Adapter - American Defense 45 Degree Offset Mount 2" Rail - GG&G 45 Degree Offset Rail

Ended up with ADM Recon (2" offset), the reason was I wanted rail space for a 45° offset red dot behind the scope.

Of course I'm over thinking it, want to do it right the first time you know. It looks like the 2" mounts usually are put as much forward on the upper as possible, while the 3" gives the opportunity of further forward adjustment. Rearward adjustment doesn't seem to be an issue, except that with a 3" there is less rail estate behind the scope for side mounted irons or a red dot. Luckily the Swarovski has a long tube offering plenty of adjustment in both directions, so I think either 2" or 3" will be fine. I just want to do it right the first time, and wonder what seems to be the optimal.

The Scout models have one locking lever as opposed to two, resulting in reduced weight and a little bit cheaper mount. However I want two locking levers for added rigidity, so I would prefer the Recon mounts. kampr and Suff: I suppose you use your mounts with a Swarovski 1-6, right? It looks like 2" offset is the most common, but for instance the Vortex HD Gen II 1-6 is an exception in that 3" is recommended. So the question is: Which is more suitable for the Swarovski? Some pictures: 2" offset 2" offset 3" offset 3" offset

I need help on choosing a mount for my new Swarovski Z6i 1-6 which will be sitting on top of my AR-15. The big question is whether to go with 2" or 3" offset. QD mount is a must, since the optic will be moved between different uppers. I've narrowed it down to either American Defense or Larue and the following models: - ADM Recon (2" offset, 1.47" height above rail) - ADM Recon X (3" offset, 1.47") - ADM Scout X, (3" offset, 1.47") - LaRue SPR-1.5 (LT104) (2" offset, 1.50") - LaRue SPR-S (LT158), (2" offset, 1.44") - LaRue SPR-E (LT139), (3" offset, 1.50")