Home Forums Hunting & Shooting AR and Tactical Rifles Forged, Cast, or Milled?

Of course for those anal,, doesn't DPMS still offer a SS lower?

Wow what a pack of misinformation!. The "hardness" of the material has nothing to do with it's method of manufacture but it's alloy and it's heat treat. Forging will not increase the density of a metal either. Forging has this benefit- it help align grain structure in the metal to increase it's tensile strength IF properly heat treated. This is primarily due to grain structure control. Non heat treated forgings indeed are often of higher tensile strength than castings of the same alloy. A proper heat treat process will make the difference negligible in any non load bearing or structural application. It is more expensive and if paying more for something means it's "better" to you, go for it.
Often when heat treating fully machined parts they warp as the billet had stress which when machined to shape were released and the part warps.
As the upper and lower of an AR are not load/stress bearing structural parts the difference is final appearance to you and cost when any of the 3 methods is properly done.

So a metallurgist is saying, thats why my 50 buck cast EA lower from years ago, is still running fine in a rattle battle gun(ones that take the most abuse as they let us open up with as many rounds we can pour down range in 50 seconds....). I always thought it was a big dog ugly, but I could care less about looks anyway, long as it works..

Jeff

Looks are a whole different arena But from a durability or strength standpoint there isn't a real difference for this application. Obviously a poorly finished piece is reflected in cost. To simply reject an upper or lower because of method of manufacture is foolish. Now if it's poorly finished, over or under size etc. reject it. the two hardest alloys- those used for structural component forgings and castings in aviation 6061 and 7075 are great alloys with substantial abrasion resistance over 1100 or 2024. Though 2024 is used extensively in aircraft- usually skin and stamped former/stringers. Not aware that anyone uses 2024 for uppers or lowers though.

I have worked with truck-loads of forged receivers, and have had my share of billet receivers through the shop. The billet receivers are softer, and as I said: "will probably get slopy in the pin-holes well before a forged receiver would"

If the billet receiver were better, there would be more of the mfgs. using them. The fact is that NONE of the main-stream makers are using them.

THey are made to tighter tolerances and the only reason why more dont make them is cost...Yes the Billet is softer. But I still dont see how you could even say probably. But hey thats me...

a

Are you saying that it costs more to cut a chunk of aluminum off of a 20' bar than it does to have it forged into a shape? And what in the world makes you believe that just because it is a "billet" that closer machining tolerances are used? That's a stretch.

The pin-holes in good quality forged receivers will beat-out. The softer billet receivers will as well, and it will happen faster.

The coating on the receiver is of huge importance as far as wear. Just comparing the major AR makers, the "hardness" of the coating used is all over the board. Oly used to produce receivers that were called "Max-Hard" It was not a coating like most of the forgings. the process went into the metal and made the surface screaming hard. The process was done "out of house" and they no longer offer these receivers. I have a couple of them that I've had for years, and they hold-up as well as my stainless DPMS lower.

One thign I know, the one reciever we had that had developed sloppy pin holes was an older oly, circa 1990... John sold me a swage kit and I swagged the holes back to size in a vise with sized hardened pins.... Worked very well so I no longer worry about pin holes wearing out.... though you could crack one according to John, its rare though.

And this was not a shot at oly, simply the one that happened to have that issue, and was the one with the barrel that never functioned.... accurate as an SUM, but function in rapid fire, nope, something wrong with the chamber.... They did eventually replace the barrel, just like good CR.

Jeff

Jeff, Oly went through a stage where their coating was on the soft-side. The coating that they are using now is top-notch, much harder than some of the other major mfgs. Oly does have their issues with machining from time to time on their lowers, but they are much harder than they used to be.

Back in the "old days" I made myself a swage kit to do the same thing. Haven't used it in years, but you mentioning it did bring back some memories.

How are you measuring the hardness of the coatings?

On the second receiver from the right you will see a little square bump sticking out right below where the pistol grip attaches. As a raw forging this is a 1/4" wide extrusion that sticks up from the inside of that nice curve. It is where the metal flows into the seam of the forging mold. All the manufactures machine this off but in different ways. That double radius is hard to cut and you can see how some makers mill it with a large flat while others use a radius cutter to make a nice smooth curve.

On an all milled receivers the manufacturers use the correct radius cutter because they have to cut the large curve instead of having it forged into shape.

It's the ALLOY and the HEAT TREAT that determines the hardness NOT THE METHOD OF MANUFACTURE.

Planemech, sent you a PM.

Most are forged very few are totally machined andf even fewer are cast anymore. Forging means they take a billet of aluminum alloy usually a7075 T-6 alloy that is what is known as "mil-spec" That billet is run through a series of dies and beaten or perssed into the shape desired, a machined reciever is the same block of 7075 alloy put into a CNC machine the parts of the billet that do not fit the program are removed, and casting is just that the molten aluminum is poured into a mould to get the rough shape then Machined to final demensions, but the mould makeing process is so exact anymore that final machining is very minimal. BTW the casting method seems to work better with harder alloys like steel like with Ruger firearms recievers.
The majority of AR recievers are forged as that is the best compromise between speed, price, and quality of finished product. They then get heat treated and teflon coated as per "Mil -Spec"

There's a fair bit more specified in the military specifications or mil-spec than simply the alloy used and it's heat treat and finish applied.

Well, if you buy a forged lower your most likely to get a out of spec lower/upper. Billet will be square and in spec..If you did a study you'll find that Forged lowers/uppers will be out of spec more than Billet...

BTW, dont you build on Olympic? So basically you dont know what quality parts are anyways

The language that you are using is misleading. ALL surfaces on a billet receiver are machined, where quite a bit of the surface of a forged receiver are NOT machined. I don't doubt for one moment that some of the forged receivers have a flaw or other problem, in or on an area not machined, that will put them "out of spec." Any surface of a forged receiver that has to mate with another part IS machined, and I don't believe for a moment that there is ANY, and I don't believe you can claim, difference between a forged or billet receiver on the machined areas.

BD1 the alloy is 7075 in your example the heat treat condition would be T6. T6 is a very high level of solution heat treat for that alloy- it's as hard as one can get aluminum and nobody would start to forge or machine 7075 in that state, hard on tooling and wasted money as the heating to forge it would wipe out the expensive T6 heat treat to the billet. Which brings me to a great point, forging starts with a billet too

All of the Thompsons were made from investment castings from orilader spain,then shipped to caspian arms to be machined,then shipped to New Hurley New York to be hand fitted!

They worked great then and now!

So whats your question about casting?

Bob

Cast steel such as Ruger's Pine Tree Casting are great.
Cast aluminum such as Olympic sucks.