Roam rifles? Magnesium alloy..

[DDadams]

Anyone here ever use any of Roam rifles receivers? I am still a bit on the fence even though the weight savings would be incredible for the build I'm wanting.

I know there were a lot of magnesium lowers and some uppers in the last few years that caught a lot of flack for just breaking on users.

But I can't seem to find even one bad review on Roam.

Plus the coating they use is what the defense industry uses on their magnesium alloy parts in jets and helicopters so if it's good to go for them I figure it should be solid for gun parts too, right?

 

[mike4]

Seeing no replies I will throw out some thoughts. Looked at Roam's webpages, and could not find any reviews pro or con from actual users via web search. I see they are all .308 sized uppers and lowers, versus 5.56mm. Typical 5.56mm lower and flat top upper you would only save around 5 oz. going from Al to Mg; should save more weight on the larger .308 receivers but difficult to compare given the lack of a standard for comparison there.

You'll noticing deleting the forward assist saves a lot of the weight. While I have advocated leveraging the large statistical sample size of military experience in other threads for a mil/defense/reliability/durability-oriented AR (BCG hard chrome lining, and barrel assembly methods), the forward assist weight, cost, additional parts, and additional protrusion close to the charging handle make it a feature that is not adding enough benefit to earn its keep. A non-forward assist upper is a good place to save weight, but barrel and stock choices are going to provide more opportunity to trim weight, and I would not roll the dice with Mg to trim only 1/3 of the receivers' weight.

Strength in AR receivers is a function of alloy, grain structure (forged, billet, cast?), and heat treat; then surface hardness/treatment particularly important where the bolt carrier rides inside the upper. Impossible to assess Roam's strength claims because they don't identify alloy, but one or more properties of most Mg alloys are less ideal than the Al alloys with very well-established mfg techniques for AR receivers. New alloys sometimes change the tradeoffs that excluded certain applications in the past, could be the case, but I still see two showstoppers in my own risk assessment.

1) I did not see any mention of Roam's site answering the forged, billet, cast question. Mg is much more difficult to forge correctly than Al, it is most often cast in all the automotive and aerospace applications they mention. Which creates non-ideal material properties in many metals which are probably the source of past failures you mention with Mg receivers. Roam may be superior but they aren't stepping up with information to counter the "rule of thumb" metallurgical wisdom. Lacking that Roam needs proof in numbers, a lot of people putting a lot of rounds and wear on their stuff.

2) Mg has serious corrosion problems, that's why they emphasize the coating. But no aerospace application I'm aware of involves sliding/wear interface with other parts or metals without some sort of bushing insert or similar. I'd be very concerned about the bolt carrier wearing through that coating and corrosion starting on the inside of the upper receiver.

If you don't mind being an early adopter and taking that gamble, go ahead. If I'm going to spend the money, time and increasingly expensive ammo I try to bias all factors toward probability of successful outcomes.

It's certainly not the lightweight direction, but when I finally went 7.62mm NATO in AR, I went with LMT MWS. Functionally I think they are very solid, but LMT were pushing their prices up to SCAR 17S levels and toward KAC levels before the Trump era gun buying slump took the wind out of their pricing sails for a time. I timed that just right to get one under $2000. Now they are back to high prices combined with an irritating lack of stock on parts, BCGs, and extra barrels which undermines the quick change barrel advantage.

 

[DadSmith]

I ran across these but was concerned about their strength. It isn't magnesium but it definitely is light at just 15oz combined weight of upper and lower receiver.

Receiver Sets - Page 1 - War Dog Industries

wardogindustry.com

 

[JEBland]

I ran across these but was concerned about their strength. It isn't magnesium but it definitely is light at just 15oz combined weight of upper and lower receiver.

Receiver Sets - Page 1 - War Dog Industries

wardogindustry.com

For AR 15s, Fortis can get you to 15 oz with ambi mag & bolt releases:

License AR15 Matched Set Ambi

There are separate lowers & uppers, too, as well as a non-ambi matched set. I like my handguard from them, but I haven't tested it by bashing it against a tree or anything. The Fortis ambi lower is ~7 oz, but the ADM ambi lower with cut outs is 10 oz and includes the magazine release and enlarged bolt catch (plus the ambi bolt release also serves as a catch, Fortis is release only), so it seemed like it was a 2-3oz trade off once actually putting the stuff on. I just don't see the purpose in shaving off those 3 oz from the middle of the gun between the hands, but some folks might. I have an ADM4 ambi lower and I think it's awesome.


Coming back to AR308/AR-10s (the sea of incompatibilities in which has kept me from trying to hard there):

mike4 posted a great list of comments. But just to add a small note, from the Roam website, they say that their alloy is superior to 6061 aluminum, but even for AR-15s most folks would turn their nose up at 6061 for the receivers. For me, I'd probably want to see some sort of durability test before committing to it given the recoil response of a .308-esque cartridge vs a 5.56-esque cartridge.

 

[DDadams]

@mike4

Great points raised, and I think even the guy answering at Roam thought so too.

For anyone interested here is his reply. I emailed him asking a couple questions and sent a link to the thread if he wanted to address any of Mike4's concerns.

Here is his reply + pictures he sent.

"
Hi Danny,



It’s no problem. Below hopefully answer all your questions.



Our R-10 Uppers and Lowers are extruded. This takes billet and pushes it through a die to form a cross sectional shape. Extrusions can have wildly different properties. One big factor for magnesium is something called the “reduction ratio”. It is basically how large of a billet you start with and how small of a formed piece you make. You want to “work” the metal a lot by having a large reduction ratio. This gives your parts good material properties. Our parts have this. Most aluminum is pushed soft with a lower reduction ratio because they can effect material properties a lot in a heat treat. You can’t do this with magnesium. The properties are pretty much set once formed. None of our components are cast, either die cast or sand cast. They are also not thixomolded. I mention thixomolding because this is a process used in the past to make some infamous lowers by a now defunct company. The combination of the alloy they used and forming method made those lowers too weak and the primary failure was due to mortaring rifles made with those lower. The ends of the lowers (curving up to the buffer tube) would crack. They were also very poorly machined…



The interior of our uppers is tagnited and cerakoted. We have a rifle that has several thousand rounds through it, all fired dry without any oil, and the Cerakote has worn through in some areas. I have attached a photo of the interior of that rifle’s upper. Some of the damage in that upper is not from the BCG rubbing, but from gouging and other types of damage. This rifle has seen a lot of testing and abuse. The rifle is still functional and has not turned into Swiss cheese due to corrosion. Most people will not fire several hundred rounds through their rifles, let alone several thousand and will not wear through the coatings. Even if you put enough rounds through it to cause comparable wear, if you don’t store the rifle wet, you’ll be fine. Nothing is perfect, wear surfaces wear and nothing has an infinite lifespan but there is no reason one of our rifles will not last you as long as you are around to shoot it.



A few other issues were brought up. It is not difficult to forge magnesium. We are going to start selling AR-15 components this year. The uppers and lowers are forgings. One of the attached pictures is of a cut up magnesium AR-15 test piece. Once we are done with the 15, we will switch to forgings for our R-10 stock. The perceived difficulty is in reality unfamiliarity. If you want an aluminum forging it is drop dead easy to buy from multiple sources, if you want a magnesium forging you must design the forging and buy your own die. If you notice in that picture the die mark is the stylized mountain in our logo turned on its size that looks like an “R”. It is our forging die.



Someone suggested that matching 6061 might be dismissed as not good enough because most AR components are made out of 7075 now. Our value add is the weight savings. If we were selling actual 6061 components, then what would be the benefit over 7075? Nothing, but we are not selling 6061 components. The question shouldn’t be “are our parts the strongest” but “are they strong enough”. The tensile strength of the magnesium we use is between 6061 and 7075. Yes, it is not as strong as 7075, but do people doubt that 6061 or a material with comparable strength properties is up to the task? You get a considerably lighter part that is more than strong enough to the task, so isn’t really a compromise any more than an F-150 is a compromise compared to an F-250 hauling a load well within the F-150’s tolerance. To illustrate the point of adequate strength, look at photos “h-1” through “h-5”. A customer handloaded his ammo and used the wrong powder. The pictures show the aftermath of firing one of our rifle with one of those rounds. No one was hurt. Picture “h-4” is particularly interesting. The force of the blast literally bent and gouged the cam pin. The upper receiver, while no longer functional, held the blast. The lower still is functional except for the bolt catch that shattered. The only thing that went flying was the magazine.



I understand the concerns people have that we are not listing the alloy. We are not sharing too many details because we consider this valuable intellectual property.


Axel"