- Stripped Upper Receiver Overview
Stripped Upper Receiver Overview
The upper receiver is the foundation of an accurate rifle, where all the parts attach to complete the top half. There are many types of receivers on the market, from basic forged receivers to unique, billet machined units. The differences between forged and billet production processes has been explained a little more in depth in our article on Lower Receivers, but we will hit on them quickly below. The following is a quick description of the different types of uppers, parts and features to look for or avoid. We will go more in-depth with each part on upcoming articles, as well as update info here from time to time.
Materials - We encourage our customers to find a receiver made of 7075 or better alloy. Most, if not all, of the higher end upper receivers on the market are 7075 or something even better. Cast and polymer receivers are not recommended for center fire or blowback rifles. Rimfire setups can get away with using these materials because the pressures and abuse the receivers see are much less than a conventional AR15. New, high-tech materials like 2055 Lithium alloy from V SEVEN or 7095 Tennalum from Master of Arms have become popular to shave weight without sacrificing strength, but with a higher price point. The more exotic the material and the more time in a CNC machine, the higher the price. On the other hand, it is pretty cool to have the latest and greatest materials available.
Forged (MilSpec) - The most popular receiver type, by a large margin. Cost effective, strong, basic and battle-proven. Quality between the different brands can differ greatly depending on the material, CNC machines, tooling and programs used for final cutting. Most of the upper forged blanks come from a small handful of companies like Cerro and look identical cosmetically. The end quality of the upper receiver will be reflected in the tolerances and machining capabilities of the company that machines the raw forging. Options are usually minimal and would be things like T-marking style, color, burnishing the interior or materials. While 2 receivers might look the same, the quality of machining will show with correct and tight tolerances, a better/smoother feel and a nice, dark anodized finish. Common forge markings like keyholes, letters or squares will let you know who did the original forging.
Billet - These receivers have been very popular due to their strength, ease of assembly and aesthetics. The downside is that they are expensive and are not technically MilSpec, so some small parts might be proprietary. Options can include thickness of the walls, T-markings, extra machining to save weight, extra material for strength (at the cost of higher weight), set screws instead of roll pins (eases install), deleting the forward assist and/or port door, undersized bolt carrier raceways, side charge operation and others. Many customers start with wanting a unique looking setup, so a billet receiver is perfect. There are plenty of designs and feature sets available to get exactly what you’re looking for.
Thick Wall Forged - VLTOR makes their Modular Upper Receivers (MUR) a little differently than most, using a forging with a thicker wall for added strength. One reason to take the plunge into the billet setups is for the added thickness for strength, but VLTOR took a different route to a stiff foundation. The benefits of the forging process have been combined with added thickness for a very rugged, strong upper receiver that can handle any caliber or setup you can throw at it. As an added benefit, they’re available with or without a forward assist, and they can both be swapped around using the modular plate that either houses the forward assist or a smooth delete. All VLTOR uppers (not including the QC10) include a dust cover assembly. Each VLTOR upper is serialized at the rear of the top rail, along with an American flag engraving.
Forward Assist - This is used to help close the bolt carrier group if it fails to go into battery, instead of racking the charging handle and ejecting a good round. The function is basic, but some people chose to delete it completely. It's a personal choice and you should choose the setup that makes the most sense for you. Assists are similar to each other, with the exception of materials, finish and functionality. Utilizing the forward assist can be tricky though, as it's possible to jam a bad round even further into the chamber. This will depend on how you're trained to clear a malfunction, as most people will tap/rack, which will get a bad round out, but might strip out a good round. If you jam a bad round in, this will introduce more problems. One great use for a forward assist is when hunting suppressed. Some people don't like to walk around the brush with a round in the chamber. Once you find your prey, you could slowly cycle a round in and use the forward assist to completely seat the bolt. If you don't see yourself using this option, look for an upper receiver without an assist to save weight and clean up the look of the receiver.
Dust Cover/Port Door Assembly - The dust cover does exactly what you'd think, it keeps dust and debris out of the action while not being used. This assembly consists of a rod, C clip, spring and the dust cover/port door. Some upper receivers don’t have a provision for a dust cover or a forward assist and are known as “basic” uppers, which can be found in both billet or forged versions. The cover will automatically open once the bolt carrier moves rearward and hits the back of the cover, opening it to let the brass eject.
Brass Deflector - Most upper receivers incorporate some sort of shell deflector for the brass to hit and bounce out of the way. We don't recommend deleting this feature, as it helps control brass in front of your face, as well as helping to keep some gas out of your face when shooting suppressed. Quite a bit of oil and carbon can build up on the deflector, which could have been in your face. On some pistol caliber and rimfire uppers, you'll see a big deflector on it that is mainly designed to deflect gas, due to the blowback operation. Some companies have also been milling out some of the material around the base of the deflector to shave weight and give an aggressive look.
Stripped Upper Receiver Options
There are quite a few variations of stripped uppers available, and each has its own feature set. Most of these features come at a premium, with the exception of deleted items. It’s usually a little cheaper for an upper without a forward assist or dust cover, assuming everything else is the same. Here is a run down of some features you’ll see:
Feed Ramp Cut - Most barrels for the AR15 have M4 feed ramps, so good quality uppers will usually have notches in the upper receiver that work with the feed ramp to help smooth the transition of the bullet being loaded from the magazine and into the chamber. We choose to only carry barrels with M4 extensions and most uppers we stock do have the M4 feed ramp cut, however, a barrel with an M4 ramp can be used on a either receiver type. There are also rifle barrel extensions, which cannot be paired with an upper using the M4 notch and also big bore calibers like 458 SOCOM that should be using a single, centered feed ramp due to the large cartridge and single stack magazine being fed from the middle.
Interior Treatments - Companies like Wilson Combat, LMT and VLTOR chose to spray an anti-friction dry lube film or burnish the inside of their uppers. The coating is a light grey color and feels slick to the touch. Burnishing smooths out the surface and leaves a rainbow type finish. As with any slick coating, the coefficient of friction of the surface is lower, which also means oil/lubricants will want to run off and not stay put. Some users prefer to utilize a thicker, heavier oil/grease to try to combat the running effect. Even when a finish or coating is advertised as "no lube", we always recommend some sort of lube to prevent excessive wear and to promote reliability. Strong Side Tactical offers interior upper receiver coating using Cerakote's MicroSlick, which is a thin, slick addition that makes it much easier to clean and adds a smoothness to the action.
Exterior Finish - The basic finish of an upper receiver is a Type 3 hard coat anodize. Many companies use their own proprietary process, or choose brand name coatings like Cerakote, Ion Bond or GunKote to apply to their parts. Using these coatings, just about any feasible color or combination of colors can be achieved. Strong Side Tactical offers Cerakote services for just about any rifle, pistol or shotgun part, large or small. We also have our own unique color called Urban Bronze, which is a dark, non-metallic, earthy-tone bronze. As with any finish, with use it will show wear. Over time, you can always refinish parts to bring them back to like new condition.
T-Markings - In between each picatinny rail section, you’ll see a letter T and then a number. These can help with a situation where the removal of any accessory from the top rail is common and constantly being moved. You would write down which T-Mark number lined up with your part so next time you install it, you just index and tighten down. T-Marks can be in white to stand out or anodized black to blend in with the rest of the upper receiver. Some hand guards also support a T Marking system, which can help for hand guard accessories.
Monolithic Style - LMT has a patent issued for the monolithic upper receiver, which is a very nice feature if you’re looking for an uninterrupted one piece top rail. The upper receiver and hand guard are actually one piece, requiring much more machining than a standard upper or hand guard. Monolithic uppers function well and have a unique look because the hand guard and upper are blended into one piece for a smooth transition, allowing for mounting your scope further forward without the need for an extended cantilever mount. These uppers come at a premium price, but when compared to a nice upper and hand guard, they aren't out of line. Another cool feature of the LMT monolithic upper is the addition of the MRP style barrel, which can be changed in a matter of minutes, without the use of vise blocks and a bunch of tools. LMT includes a torque wrench that's specifically made to tighten and loosen the 2 screws on the side of the hand guard, making it easy to pull out the barrel, gas system and all, out of the upper to swap for a different length or a different caliber, like 6.8 SPC. LMT recently came out with their MLok monolithic uppers in Rifle Length and Carbine Length, instead of their Screw Type Picatinny rail models, allowing for a smooth rail and easy attachments.
Polylithic Uppers - Polylithic uppers from VLTOR include the upper receiver with a hand guard, machined as one piece. A window at the bottom gives room to tighten the barrel nut, so you won't need a long barrel nut wrench to change barrels. These are similar to the monolithic design, but incorporate a different barrel nut and attachment. The polylithic style is also much cheaper than other monolithic options.
Proprietary Uppers - Some setups require a specific lower that was made as a set. One example is the JP Enterprises SCR-11 side charge set. The traditional charging handle has been deleted in favor for a left side, non-reciprocating, flip out charging handle. These uppers can offer very unique, useful features, but give up compatibility and are usually higher in price. We LOVE the JP Enterprises SCR-11 (AR15) and LRP-07 (AR10) rifles and receivers! This style works extremely well for setups using a suppressor or a hotter caliber, reducing blow back to the face by closing off the rear charging handle.
Side Charge Operation - If you don’t have multiple complete uppers that you swap back and forth, then the compatibility issue on a SCR-11 isn’t a big deal. If you want a JP side charger and have a standard lower receiver, look at the PSC-11. It has the side charge capability, along with the traditional T-handle and will fit on most lower receivers. Another option would be a standard style upper with a side charge only operation, like the X-Products SCU billet upper. This unique upper uses a special cam pin to interact with the side charge lever, not requiring a proprietary bolt carrier.
Carry Handles - The original Stoner rifle had a big carry handle on the top instead of the picatinny rails that people are accustomed to seeing these days. There are still many of these setups in production, but the ability to mount an optic in the optimal location makes the flat top uppers more popular. There are some uppers with a removable handle, and aftermarket/removable handles can be added if you'd rather carry the rifle than sling it up. These carry handles also have a rear sight built in for use with the front sight style of gas blocks.
Pistol Caliber - Quarter Circle 10 teamed up with VLTOR to create a nice upper receiver specifically for the pistol caliber carbines (PCCs) and 22LR that are popular today. Since the casing of a pistol or rimfire cartridge is much shorter than a rifle, the port can be shorter. This results in less of the bolt carrier being exposed to the elements and makes for a clean look. These uppers are lacking a forward assist, dust cover and the clover hole for a gas tube, since it’s not necessary in a blowback design. These uppers are high quality and come with the same burnishing process as the other MUR uppers. These aren't necessary to run a pistol caliber setup, but they sure are nice! Because of the lack of a gas tube hole and the short ejection port, their uppers cannot be used on any gas impingement or piston operated rifle.
Undersized Carrier Raceway - Wilson Combat’s billet series of upper receivers are undersized slightly in the channel that the carrier rides in. This helps to reduce slop, get a tighter fit and reduce carrier tilt to get an even wear-in pattern of the two parts.
Undersized Barrel Extension - BCM utilizes an undersized barrel mount receiver extension so that the barrel to upper receiver fit is precise and tight. Most quality uppers have a snug fit, but BCMs are a little on the tight side, which is not a bad thing. A tighter fit between the barrel and upper receiver is desired to keep the barrel from floating around over time and heat cycles. Some shooters even choose to temperature set their barrels with shims to get the tightest fit possible. Heating the receiver and cooling barrel, along with an appropriately sized shim, can yield a very tight barrel fit. This practice is used by JP Enterprises on their centerfire rifles.
Lightened/Skeletonized - One trend over the past few years is to get the lightest rifle possible, even down to 3.5 pounds like the Fostech rifle. In order to accomplish this, many manufacturers are reducing weight on the upper receiver by cutting away excess material. This also has an aggressive look, to which the company can tailor a certain look, like V SEVEN’s Enlightened upper or the Master of Arms Esoteric set. The most aggressive pattern we've seen is the new F1 Firearms BDR-15-3G receiver set, featuring milling work that completely goes through the receiver, exposing the internals and shedding weight. This receiver set is a fantastic lightweight route, but keep in mind that it's easier to let dirt in.
Tolerances - Most of the higher end companies run with a tighter tolerance range to help produce a tight, slop free fit and a good fitment for the small parts. These companies can easily have half the tolerance of the MilSpec, making for some very precise parts. MilSpec tolerances are generally +/-.010", while companies like Wilson Combat and other high end manufacturers use a +/-.005" tolerance. This means that parts should fit more precisely and the manufacturer has a smaller window of forgiveness when making parts. Parts that fit well together will make for a precise rifle with no loose fitting parts. While not as big of an issue as in a 1911/2011 pistol, tolerance stacking can make for a loose or overly tight fit, depending on how the stacking occurs.