If polymers and plastic work better than metal, then i have no problem using them. The SCAR is just in its infancy, though it amuses me how quick everybody is to “forget” about the M16′s flaws when it was first introduced. It is not just “plastic”. It is a specified polymer. Similar to saying a Romanian AK is the same as a Russian one because it is “made of metal”. Generalizations are very rarely true.

I have yet to see the “see saw” effect on gas piston AR15′s (that DI mongols are always screaming about). I must have awesome luck, because the three models that I own work quite well despite thousands of rounds going through them (bushmaster XM15 ES2, LWRC M6A2, and Olympic Arms with a osprey defense conversion kit). I enjoy my civilian SCAR 16S (as well as its competitor, the Robinson XCR) and will see how long it lasts versus AR15 rifles of direct impingement and gas piston operation.

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The newer 51 tooth suppressor mounts are far superior, and have been out for almost two years now.

Are the SCARs going to stick with the 18 tooth mount indefinitely?

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http://i49.photobucket.com/albums/f270/Mr_Blazin/Rifle%20Pics/Bravo-craqckedlower-02.jpg

From Ar15.com

http://www.ar15.com/forums/topic.html?b=3&f=62&t=369202&page=30

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Sig uses a plastic hammer in their P250
H&K uses plastic hammers in their G36/SLR-8
FN uses plastic hammers in their FS2000 and SCAR

What the hell’s the matter with these people? Haven’t they heard of Forgings?

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HK are decent overpriced firearms. You can get much better firearm at a lower price then HK. Glock and CZ comes to mind. HK416 as well as other piston AR type have a lot of flaws that must be overcome.

Plastic firearms are bad. The only plastic gun that worth a damn are Glocks.

http://larrycorreia.wordpress.com/2007/10/09/hk-because-you-suck-and-we-hate-you/

Ken, the see-saw affect applies to piston AR and not DI AR.

DI AR receiver will last forever.

http://www.ar15.com/forums/topic.html?b=2&f=130&t=165511

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Keep it up, kid. The only way to learn it is to teach yourself. I was a teenage gun nut once. Now I work in the industry. I got the greatest job in the world, and all of my friends are doing lame-ass conventional stuff. You won’t learn this stuff in school, it is VERBOTEN.

P.S.: H&K thinks you suck, and they hate you.

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I agree that two springs are superior. You may note that some newer designs, such as the Kel-Tec RFB, use two recoil springs instead of one. They are not absolutely essential in most designs.

The problem is not the gas system, and for all intents and purposes, the DI gas system is actually better than most, including the AR-18. This is because the bolt is actually pushed forward as it rotates to unlock, which takes the stress off of the lugs. The gas pushes directly on the bolt as well as on the carrier, which causes the bolt to unlock. The best version of this system to date IMHO is the Zitta system used in Para USA’s TTR.

With a conventional piston driven system, which by design is pushing on the bolt carrier outside of it’s central axis, the bolt is pulled backwards against the lugs as the carrier moves. This creates stress on the lugs, as well as friction and heat. The piston, whatever it’s design, pushes a bolt carrier, which pulls the bolt. The weak design of Johnson/Stoner bolt is due to the unequal distribution of forces around the circumference of the bolt and the locking surfaces of the lugs. The lugs nearest to the extractor will be under the most stress, and the ones opposite those two will be under more stress than the others. This is not a big deal when the bolt is pushed forward during rotation, but when it’s pulled, it gets bad.

The carrier being pushed off of it’s central axis by the piston, usually from the top means that it wants to go in the opposite direction, usually downward, tilting at it’s center of gravity. This creates a sea-saw effect on the carrier and causes it to tilt very slightly as it travels reward, which causes the bottom end of the rear of the carrier to drag, as well as the top end of the front. This creates legions of problems in an AR upper, and excessive rail wear on other designs, such as the FAL and the SCAR. This is described quite admirably in part 1 of the Small Arms Review interview with C. Reed Knight, Jr., February 2009, Vol. 12 No. 5.

Apologies to Steve for my long posts.

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What I recalled, that around 800 rounds the spring will start to lose it strength and malfunction will happen more. By using double recoiled spring the elastic limit will not be reach. So basically the springs will last for a long time.

Small Arms Review is the only gun magazine that worth the time to read. Check it out.

ACR use the AR18 action so it won’t have the same problem as the AR15 DI where the locking lug will break. This is because most of the stress is directed at the bolt. This is not the case for the AR18.

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jdun1911 is right about the ACR being in limbo. The Magpul engineers that I’ve spoken too seem to be somewhere between skeptical and outright pessimistic on that dog ever seeing the light of day. I can never get a straight answer out of the people from Bushmaster, which means they really don’t know anything more than we do.

The major flaw I see in the Masada/ACR (I will continue to call it the Masada until somebody else actually produces an ACR or whatever) is that it uses a Johnson/Stoner bolt. All piston driven ARs suffer from the same faults with sheared off bolt lugs, and the Masada will be no exception.

The SCAR is only a slight improvement, since they went with a different bolt that has lugs completely missing on about 1/3 of it’s circumference, I am skeptical of the SCARs long term durability as well, but probably most of the plastic parts will break several times before that bolt does.

Cerberus now owns such a large chunk of the AR market that perhaps they are reluctant to create a rifle which will compete with that market, even if it uses many AR parts. No, it doesn’t make sense to me, either.

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Bushmaster has all the tools and molds needed to start production last year from Magpul. In fact Bushmaster could have shipped them out to dealers around Nov. IIRC.

When Bushmaster heard about the new Army rifle completion, they decided to hold off. They wanted to know all the requirements in the new program which should be available around Nov. of this year.

Both system is probably flawed because Author Miller has pointed out that the AR18 action in order to work reliable needs to use double recoil spring. Both the SCAR (modified) and ACR relies on a single recoil spring.

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