Armory Sponsor
Posted: 9/27/2002 8:00:47 AM EDT
|
What is the difference in Forged Lowers and Cast Lowers? Isn't cast when the shoot molten steel/aluminum inside a molding and let it cool to make the lower? And I think that forged is when they heat up the metal and bend it into place, right? Now supposing that these two methods are correct, the forged lower would be superior in strength and durability, right? Therefore a Rock River Arms Forged Lower is superior to a DPMS Cast Lower, right? Please someone explain this to me, I don't want to buy a crap-ass reciever. -Uhlek- |
|
I've worked at a world renowned foundry where I designed castings and forged parts, and I laugh when I hear about how one type is far superior than the other, what a joke! It has to due with the application. They both just hold the components that actually due the work. I don't imagine that any of us will use a forged lower or upper as a pry bar or tire jack. Cast recievers are just as good in the application as forged. But now, lets say I'm gonna use my AR-15 to change track pads, after I hammer away at the bolts with the weapon, I might want a Slegde hammer with a long handle to reach the enemy. |
|
I thought FORGED meant that it was a solid piece of steel that was drilled out to the final shape. Am I wrong here? I thought that's how it was more dense since stronger steel could be used, then milled out to create the final product, thus you get a stronger receiver. |
|
To illustrate: www.olyarms.com/castorforged.html Maybe it helps, maybe not. |
|
In a casting, the molten alloy is poured into a form and allowed to cool. In a Forging the alloy is poured into a form which is spun at considerable speed to "press" the molten alloy into the shape of the form. This process produces a higher dimensional accuracy from the form, and ensures that no weakness in the alloy will exist in the finished product. 
|
|
The AR was engineered to use forged parts. Why save $6 on your $600 rifle and go with something that's going to give you problems later on? In forging a hammer is used to pound the metal in a mold and normally produces a wide seam of metal that sticks out. This is then milled out leaving a tell tale scar - look forward of the magazine well. Corners are sharp and well defined. Lettering is often CNC cut into the receivers. Casting is fine and strong enough for use in many cases when engineered to be used. Castings often have small pockets and flaws that will show up in the finish. Corners and radius can not be made as sharp. Lettering and markings (like the safe/fire) will appear to rise up out of the background in a casting - vice being cut down into the background on a forged receiver. I have seven forged and one casted (Hesse) receiver and haven't broken any of them. The dimentions in the Hesse are by far the worse ... might be forge problem, might be a Hesse problem. |
|
The site that IMHO linked is actually a good one for determining if a lower is cast or forged. I happened to talk to the fine folks at Olympic for a while yesterday (I'm buying a pre-ban Oly and wanted some info). The above-linked site pretty much says exactly what the guy on the phone told me. Also (and this depends on the finish applied), cast lowers will often have a dull, matte finish because of the microscopic voids in the surface; a forged lower will have a slicker appearance. To echo what someone else said above, for an AR I doubt that cast or forged makes a bit of difference; CavArms lowers aren't even metal, and they can stand up to full-auto fire. |
|
Note: Cast lowers converted into full auto work just as well as a forged lower. The cast metal is not as dense, but for what 95% of us do with our rifles, it will not make any difference. In regards to imperfections/voids, it depends on the casting process implemented. Some have few if any imperfections. You can save $20-40 in buying a cast vs. forged. www.triplebreakproducts.com/TechTips/castorforged.htm |
|
I've had both cast and forged receivers. Forged do LOOK better, but the lower is a low stress part. Heck, the UPPER is a low stress part. It is a non-issue to me. I keep saying it, the BOLT locks into the Barrel Extension. That is the high stress area. Tell you guys what... you can send me all your cast lowers, and I will make sure they are safely disposed of. (Edited to add:) The cast lowers I have had were Essential Arms, and of very good quality. All parts fit and functioned well. |
|
The alloy used has a great deal to do with how it's worked as well.. I have yet to see any cast component fabricated from 7075 alloy. While a casting (5000 series? Or are they 2000 series alloys? I'm guessing they are heat treated at some point-) may prove satisfactory for a lower reciever, I'd still prefer a 7075T6 forging for an upper reciever, thank you..(Personal paranoia, not based on fact) Regarding application, there IS a diffrence, in refrence to grain structure and orientation of said grain. A casting will posess a homogenous grain structure. In most applications this is not a problem, until one applies repetetive stresses in localized areas. Especially with aluminimum alloys, where work hardening and resultant stress cracking can occur if one tries to save money through the use of low quality castings. A well engineered forging will orient the grain structure of the finished component to allow the part to resist a known stress issue.. All this is well and good, until one realizes how short the stress paths in an AR-15 actually are, and how isolated they are from the recievers.Borne entirely within the lugs of the bolt, and barrel extension, the reciever sees little of the actual stress of firing. One will not appreciate the diffrence between a forging and casting til something goes wrong within the upper reciever. Meplat- |
|
Over the years, we've had a number of members post stories, often with pics, about mishaps that they've had with their ARs. I've noted that a surprising majority of the cases where the lower was damaged, the lower was of the cast variety. This is significant, especially when you consider that the majority of lowers overall are forged, so the pool of cast lowers is much smaller. Granted, in the cases I refer to, the rifles suffered *abuse*, not simply normal use as would be expected at a gun range. In one case, an AR was in the trunk of a car in an accident. In another, one of the pivot lugs was broken due to the gun being dropped on it's side. In another, the lug holding the bolt stop was broken off as the pin was being driven out. And in yet another, the rifle was slung over the back of someone who wrecked on a 4-wheel ATV. Still, we've not seen problems such as these reported with forged lowers, even though there are far more forged lowers out there. It is pretty obvious that forged lowers will stand up to significant levels of abuse without damage, and cast lowers will not. How important this is to you, I can't say. I own a cast pre-ban lower (Essential Arms), but given the oppertunity, I'd upgrade it to a forged lower without hesitation, even if it cost $300 to do so. That isn't because my lower isn't working; it works great. But I'd rather it was strong enough to handle unexpected abuse, and I honestly don't believe it can. -Troy |
Would you upgrade to SS or Titanium lowers for the added strength? :-) |
Both of these would be considered castings. The only difference being that one is using centrifugal force to fill the mold out, usually because the mold is more intricate and needs the extra force to fill out the mold completely. Forging involves tremendous pressure slamming metal into or between molds to get them to the rough shape of the object. You guys have seen footage of them I'm sure. It's where you see this huge press continiously lifting and dropping a huge weight onto a glowing white hot piece of steel.....it's being forged. It doesn't HAVE to be into or between a mold, but that helps to save on machining steps if you do so. |
|
I still say that if you insist on an aluminum lower, for most people, it wont matter If I wreck on a 4 wheeler bad enough to break my rifle, something tells me I will have other things to worry about. I still think the best route for a lower is injection molded. they are strong, dont have to worry about corrosion (sp?). light weight. Just my .02 worth |
|
As for ARs and the like... A forging involves taking a "plug" or a "slug" of the metal you want to use for the final product and smashing it into shape between two dies (molds). Usually, for the harder materials, the "slug" is heated to red-hot in order for it to flow into the form better. Most of the crankshafts in your cars' engines are made this way, along with some of your more expensive, hi-performace pistons. Sometimes it takes 3 or 4 molds to make the part. Parts are then machined from there. This involves the removal of a lot of 'flashing', with thick parts needing removal in most cases. A "true" forged part is the strongest, as the metal is forced (to a point) to 'flow' into the final shape. The crystalline structure of the metal is kept intact. Most all of the stuff I have seen has been "investment cast" which is a VERY OLD process. Parts are made by pouring the molten aluminum into sand-cast forms (kinda oily sand), then they are machined from there. Usually, to make good investment casts, the mold will spin and enact centrifugal force into the process of making the metal have less voids. SOME (but not many) of the parts out there are from billet, which is almost as good as a true forging. A billet is basically a slab of metal cut from a sheet or extrusion (very high quality). Every single little detail on the billet part is machined into shape...everything. Honestly. I think forged parts kick-ass over cast parts any day, at least for aluminum stuff. This post was written by:Devilsadvocate. |
So that if it hits someing while turning it will shatter and blow away instead of bending (with a stronger metal) and possibly ripping more blades off with it. 
|
|
A bad analogy of course but lets say you have an artificial leg,and you can get it made of cast steel or forged steel! The cast is cheaper but if I jump out of a window and hit just right it could shatter causing sever damage! But with the forged steel leg it would stand much higher stress before it would or could break,(more than I could put on it) Which one would you buy? Bob 
|
|
I spent 14 years machining aluminium forgings for Boeing airplanes. When Boeing wants something to stay together, they use a forging. Whenever we machined plate, we used forged plate and cut it according to the blueprint callout for grain direction. A forging is stronger. If you have a bayonet lug and want to be able to use it as a bayonet lug you'd be better off thrusting with a forged lower. |
Armory Sponsor