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Posted: 6/18/2008 9:22:16 PM EDT
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I am going to build a SASS type rifle. Likely to use a noveskie barrel, which is one of the benefits of the AR10b system of course. Are there any other benefits of the AR10 system over the DPMS? I kind of like the idea of having a DPMS thick walled A3 upper w/ FA so I can chamber weapon silently if I am on manual operation, so there is more support for the barrel, & so I can get cheaper magazines. Can you mount a Noveskie barrel/extension/bolt & gas system on a DPMS upper? The gas tube wouldn't be too short? Are the carriers interchangeable? What about the DPMS/SR/AR10/JP/Fulton etc magazines. I know the old waffle mags are realtively cheap, but aren't they a little flimsy. What about newer production steel magazines in the DPMS/SR25 pattern, are they as good as the Armalite Gen II magazines? Are they as expensive as the Armalite Gen II mags or are they cheaper. |
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wrong forum mags cost the same, armalite has better features, uppers are forged so they are stronger but thinner, one of the reasons I don't like DPMS among others chambering a round "silently" is for ninjas, are you one of those? You can also do it with a Armalite, or slick side AR15. Read the FAQ for more info on 308 variants Did you really expect to get votes for DPMS on a AR10 forum? |
  yep, many thing the 308 needs to be rammed in there for some reason. If you are having to do that, then you have a brass problem. there have been more than one "love fest/pissing matches" between the 2. it comes down to what features are important to you and what you expect out of a rifle-no matter what anyone thinks. |
That has always been the preferred method IMHO. As far as the thicker upper walls on the receiver the ArmaLite is forged which is much stronger than billet machined for the same weight. |
| I really wish the "forging for strength" hype would stop. The reason for forging receivers that see little real stress is for saving manufacturing costs, not for strength. If you are going to make thousands of identical receivers, the forging process provides a near net shape exterior surface that requires less expensive machine time. Less expensive machine time means greater profit potential for Armalite. As an evil Capitalist, I approve of Armalite's use of forging. |
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I looked long and hard at both Armalite and DPMS, both SASS. With the DPMS you got more accessories bipod, grip, flip up sites etc and it was cheaper like $1700+tax, the Armalite was $2600 + tax. After some thought I decided on the Armalite the main reason was the basic gun was better. I was only buying this gun once so I wanted my BEST value for my money. A local shop had both in stock and being that I was paying cash they gave me a fair deal on the Armalite. |
Then I apologize for bursting your bubble. I think you are confusing sheet metal stamping dies with forging dies or something...the two processes are vastly different. Forged aluminum parts are very expensive to produce. You can't just mash a chunk of aluminum between two dies and viola! out pops a receiver...LMFAO!!!! First, the dies are made from machined and heat-treated tool steel, which is extremely hard and is WAY tougher to machine than aluminum. They must also be highly polished to a mirror finish in order to get the desired finish...as such, those dies are hideously expensive to produce. Not only that, but there are normally multiple sets of dies used, you have pre-forming dies, forming dies, and finishing dies...and the dies only last for a limited number of cycles before they are NFG and new ones must be made. Also take into consideration that aluminum, from a thermal standpoint, shrinks and expands far more than steel, so those dies are designed to be larger by a certain percentage to allow for the finished parts to shrink to a nominal size as it cools down to ambient temperature. As such, tool & die makers and engineers spend a huge amount of time designing and manufacturing forging dies to perform to a strict set of specifications. In addition, temperature control in the forging environment is absolutely critical, the forging process occurs in a furnace where the dies are kept at a constant temperature somewhere around 600-800 degrees Fahrenheit (do you have any idea how expensive it is to keep something heated to 800 degrees 24/7?). Not to mention the fact that aluminum has a tendency to stick to steel in a high-temperature environment, so high-performance release-agent chemicals/compounds are used, which aren't cheap. Also take into consideration that MASSIVE hydraulic presses that apply hundreds of thousands of TONS of pressure, (operating inside of a high temperature furnace mind you...) are needed to form the parts. So it is plain to see that the tooling expenses that are required in order to manufacture aluminum forgings to close tolerances are hideously expensive! A nice $250,000 Mori-Seiki 3-axis CNC mill, a CAM program like MasterCAM or SurfCAM, and a kid fresh out of machinist trade school can churn out billet-machined parts. An aluminum forging plant is going to cost on the order of many, many millions of dollars. Tool & die makers are the most talented, knowledgeable, and experienced type of machinists on the planet and are very highly paid. A manufacturer doesn't do forgings if they want to hammer out thousands of parts cheaply (lol!!!!) A manufacturer demands forged aluminum parts because they require the greatest strength-to-weight (aspect ratio) humanly possible and is willing to pay a hefty price to do so. In addition, it is a well-documented FACT that forged aluminum has far greater resistance to WEAR than standard billet, so a forged aluminum receiver will last through far more bolt carrier cycles (number of shots) before wearing out and therefore possessing a longer service life...any wonder why forged receivers are the only ones that are considered mil-spec? So even though the Armalites are more expensive, you're getting a hands-down better product...and I am willing to bet real money that Armalite doesn't get a higher profit margin on their products despite selling them for higher prices. |
Sorry to burst your bubble, but the methods you described to churn out cheap machined bullet receivers also work for producing relatively inexpensive dies from a customer's CAD drawing. No small manufacturer, like Armalite, does it's own forging but instead hire shops who specialize in forging. (Most small manufacturers subcontract out all their operations that require heavy investment in expensive capital equipment because they don't have a high utilization rate to justify the expense). The engineering departments for big forging shops have the software to translate customer manufacturing drawings to die drawings while accounting for draft angle requirements and material shrinkage. Specialized 6 axis machining centers do the majority of the work but dies are hand polished to meet the final surface finish requirements. The same method would apply to producing the extrusion dies used for DPMS 308 uppers or injection molding dies used by Cavalry Arms. The bottom line is, there are costs associated with overbuilding a product. That other "not so strong" methods and materials have been used for AR-style receivers gives a hint that strength may not be the operative factor in selecting the forging process. It comes down to a cost trade off of the cheapest way to produce a receiver based on the engineering department's requirements. Below are different equally valid approaches that have been used over the years to manufacture receivers for AR-style rifles (remember the max stresses are in the barrel extension and bolt lugs, not the receiver):
Which method is the cheapest way to meet the engineering department's requirements? A? B? C/D/E/F? It all depends on the size of the production lots, cost to run a lot, cost of subcontractor services, cost of in-house assembly labor, ETC. |
Grain direction plays no role in a low stress part like the receiver on an AR-style rifle. We know they are low stress because AR-style recievers have been made of plastic for God's sake! Sure, forging does promote grain flow. But so does extruding where grain flows parallel to the axis of the extrusion. (But can have other issues such as "piping"). And so does what we call "billet" (which is more accurately described as thick plate), whose grain flows parallel to the direction of the rollers used to roll out the plate. |
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I agree that Armalite would have to subcontract to a forging facility for their forged uppers and lowers and then finish machine the remaining operations in-house. A modern pallet-loading three axis CNC mill running through-tool-coolant can machine the outer profile of a AR lower or upper extremely fast. Especially when running an aluminum rougher to hog material in preparation for finish passes where you can run the mill at 800 surface feet per minute or faster. Once you get to the point where your cnc program is proven and first article is inspected, you can literally go into a "lights-out machining" mode where all you need is a button-pusher/operator to swap out parts and clean out the chip conveyor every so often. It is still going to be a more expensive proposition to purchase those forged uppers/lowers from the forging plant and you're still getting a stronger and more durable product versus machining from standard billet. I also agree with you that the operating stresses in any AR are focused around the barrel, barrel extension, and bolt (instead of barrel, bolt, and receiver in other designs) as I have stated in previous posts. This means that the AR upper receiver simply acts as a raceway for the bolt/carrier assembly to translate back and forth along an axis concentric and coincident with the barrel/bore axis. Is the extra strength and durability of a forged receiver really necessary for such an application? I honestly don't know as I am not in the gun making business and don't have the time/energy/finances to run an FEA analysis on multiple receiver models  or do any destructive testing on different brands/types of receivers  before making a decision on which brand of rifle to buy...that would be absurd.All I can do is be aware of the fact that forged receivers are stronger and more durable than billet and take note of the fact that only forged receivers qualify as mil-spec. Not to mention that very best and most discriminating AR manufacturers in the country such as MSTN and Noveske choose to use only forged mil-spec uppers/lowers in their builds. These reasons justify the extra price in my mind and it is a price I am willing and able to pay. I do believe that Armalite is a little on the stodgy side when it comes to innovation by only offering .308 Winchester and .338 Federal in their AR-10 caliber line-up. I believe that ending .300 RSAUM rifle production is a bad decision in light of the many calibers that DPMS offers. I guess it's like driving a Hyundai versus a Mercedes...both are good, honest cars and both will get you where you want to go. Simply a matter of reliability and durability over time and which car would you rather be driving if ever SHTF (in this case a collision of some sort)...my money will go on the Mercedes. |
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Though its true that the receiver is not a stressed part in terms of the lock-up, the receiver can flex somewhat where the barrel attaches which could degrade accuracy of you were using a heavy long barrel & scope. Sounds like the Armalite uppers being forged & lighter weight than the heavy extruded DPMS uppers makes them the best of both worlds. |
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You're hitting on an important point. A forged aluminum receiver would obviously have a greater material density. In addition to possessing superior wear qualities, a greater material density equates to higher ridgidity, and would thereby have an effect on something known as a natural frequency. This might be a bad analogy...but think of when a diver jumps off of a diving board and the board whips up-and-down for a time afterward. Some diving boards have a adjustable fulcrum point and when moved toward the front of the board, the board is "shortened" and so is effectively more ridgid. As such it will flex up-and-down less (decreased positive and negative amplitude) but at a faster "rate" (shorter wavelength) versus when the fulcrum point is shifted further away from the end of the board. In a rifle like an AR, a forged receiver would possess a "higher" natural frequency (effectively a shorter wavelength and therefore smaller positive/negative amplitude...amplitude being the "height" of the "crest" or "trough" of a wave, or sort of like an inflection point...wavelength being the period of time between "crests" and "troughs") Anyway, the higher natural frequency of a forged receiver equates to a smaller positive and negative amplitude and thus less "flexing" while shooting. This might have a superior effect on accuracy (doubtful) but would have an advantageous net effect on fatigue of the receiver over time...being that the receiver would "flex" less. You could also affect the natural frequency of a receiver by making it thicker...but if the receiver was not forged, you're still not getting any improvement in wear qualities, not to mention a weight penalty. Of course all of this is simply conjecture and is based on my own little opinion as I do not possess a fully equipped prototyping and research laboratory with which to test and evaluate these notions so as to provide empirical research data for testing, duplication, and verification by any anonymous internet experts... |
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Been beaten to death in a previous thread... www.ar15.com/forums/topic.html?b=3&f=62&t=366199 |
I will send this to AR Variants, stand by... |
I see what you are saying. I was actually just talking about flex in so far as the the bore coming out of alignment w/ the POA of the receiver mounted scope. But the harmonic vibrations of the barrel during firing would also affect the receiver. |
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As fun as these material arguments are to have on the Internet, I think I'll start giving it some serious concern when somebody posts a pic of a failed DPMS 308 attributable to the material choice. Even the harmonic frequency argument above is essentially bunk, at least in the context of these guns. Are you really going to launch into an argument saying that the DPMS guns have accuracy issues or are inherently less accurate in a perceivable amount than the Armalite guns? Buy what you want because you like it. Don't make up reasons to justify why you bought what you did. |
McDonnell Douglas (bought by Boeing) uses 6061 T6 to make F/A-18s. The USN spec'd that material to withstand the rigors of carrier takeoff/landing and flight maneuvers. It also has better corrosion resistance and weldability than 7075 T6. Do you think MDD is fucking up when they make F/A-18s out of 6061 T6? If so, you can call Jim McNerny in the morning and tell him he's fucking up. But wait! MDD also builds F-15Es out of 7075 T6 in the same damned factory! So you see it all depends on the requirements laid out by the engineering staff during the design process. Both materials perform pretty well in similar applications. The whole forged "7075 is better than extruded 6061" is like "9 vs 45" or "AR vs AK". It just another argument about how many angels can dance on the head of a pin. |
If you read my post, I said that it MIGHT have a superior effect on accuracy but it was DOUBTFUL. Changes in natural frequency would have more of an effect on FATIGUE over time. Admittedly a forged mil-spec receiver owned/used by the military is going to see a lot more use and abuse than the comparatively luxurious and pampered life that a mil-spec receiver would see being owned/used by a civilian. Still, it is nice to know that the durability is there if ever it is needed...so I'll stick to 7075/forged uppers and lowers for my AR's...thanks. |
Thank you for your observation in blue above. Controlled (reduced) harmonics is one of the keys to an accurate rifle. And one of the best ways to minimize the negative effects of non-repeatable harmonics is to increase the moment of inertia of a component. Increasing the moment of inertia commonly involves making cross sectional areas thick (that means large diameter barrels and thick walled receivers). |
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I essentially said the same thing previously... "You could also affect the natural frequency of a receiver by making it thicker..." Sure, you're affecting the natural frequency by increasing the moment of inertia/sectional density or by increasing the material density... Still...a thicker walled receiver made of a softer material does nothing to increase wear resistance...nor make the rifle any lighter. |
Bells (the ding-dong type) have dense tough material, but low thickness. I don't think I'd want to make a receiver out of one. Give me a thick walled receiver. The bench rest guys even go as far as bonding a thick walled aluminum sleeve over Remington 700 receivers to stiffen them up. |
Seriously? Though I own several Sako's including a TRG-22...I know next to nothing about customized high end benchrest bolt guns. That would effectively increase the moment of inertia/sectional density of the M700 receiver and therefore affect the natural frequency... However you're talking about bonding two materials (steel within aluminum?) with two completely different thermal properties with respect to expansion and contraction...doesn't make any sense to me why somebody would do that. Seems like it would be difficult to keep the two materials bonded through a number of heating/cooling cycles. |
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Dpms uses extruded thick wall receivers on the uppers-Amralite use thinner forgings neither company has had problems with cracked receivers lately. Dpms uses forged lowers so does Armalite Dpms .308s are more accurate out of the box than Armalite in general. Which is a better rifle?? That is an argument that has gone on since DPMS went after the .308 market. Now RRA is trying to get a piece of the pie, all are good choices buy what you like I don't think you can go wrong with any of them. |
Lots of bench rest competitors sleeved their 700s in the 1990s. 700s were cheap and easy to sleeve because the receiver is round and the sleeve is round with cutouts for a reduced size ejection port and window to view the serial number. The sleeve was epoxied to the receiver. The sleeved action was then epoxied into the stock with the rear of the sleeve forming a recoil lug. Sleeving isn't done much any more because the bench rest guys have all switched to extremely thick walled aluminum or stainless receivers which can be had for a couple hundred dollars more than a sleeved 700. Kelby's Aluminum Panda Receiver Nesika Stainless Receivers Bench Rest is a tough and expensive sport, where competitors may throw away four or five $500 barrels in a season because they cannot be made to shoot 0.10" groups. |
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If I was to pick one of those brands just by what you get out of the box I would go DPMS. Another vote would go to DPMS cause of the mags. Since alot of the new 308s will be or are using the SR/DPMS style mags it makes more sense to go that rout. Plus the DPMS mags are a bit cheaper. My biggest turn off with Armalite would be the mags that has been why I have not got one. But in true ARF fashion I might give into that and buy a couple lowers for custom builds. But at the same time all be doing that with DPMS style lowers as well. |
Really then they need to update their website
Hmm last time I checked Armalite will guarantee the accuracy, dpms won't. Thats a hell of a claim since you don't have dick to back it up. If anything many will say that the AR10 shoots better. These vs threads are stupid as are many of the post |
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Stiffening receivers is a time tested method of improving accuracy. HK makes PSG-1 sniper rifles out of standard G3 receivers be welding rails to the side of the gun. The flexing of the receiver is controlled by the moment of inertia, which is calculated based on receiver geometry, and the modulus of elasticity of the material. Both the 7075 and the 6061 are very close, (7075 -> 71.7GPa, 6061 -> 68.9GPa) The thicker walls of the DPMS receivers probably more than ofset the 4% reduction in the modulus. The receivers are essentially the same. Although the surface wear characteristics of the two materials may be different and affected by the forming process (forged vs. extruded), it will be dominated by the surface treatment. IIRC, this is a hard anodizing, which has wear characteristics far better than either material formed in either process. The receivers are essentially the same. Yes, in terms of pure material properties, 7075 is stronger than 6061. As has already been pointed out, AR receivers have been made out of aramid fiber, so either is a more than adequate choice. I can't tell you why 7075 was initially chosen. You'd have to ask Eugene Stoner... The fact that we have to delve into discussions of material grain structures to discern a difference between these two fine products tells us just how similar they really are. Pick which one you want based on aesthetics, options, chrome, whatever, but the material properties of the receivers are a non-issue. I really wish the price of ammo would come back down so we could all be out shooting rather than having some of these pointless discussions.
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