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Thread: Could A .308 Upper For The Mac Style Family Of RRs Be Designed

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    Could A .308 Upper For The Mac Style Family Of RRs Be Designed

    There was some controversy as to scaling up the S.A.B.R.E., Max 15, Ultramac style upper from an AR-15 based medium rifle caliber to AR-10 full power rifle caliber on the Lage congratulatory thread. It would seem to me that moving that discussion to another thread would be more appropriate.

    For those that are not familiar, the AR-10 was developed by Fairchild in the 50's. It has a gas impingement system for function. It was originally designed for use with the .308/7.62X51 NATO cartridge. Fairchild did have some commercial success with the AR-10. I am not going to go into the history of how and why the AR-10 was down sized from .308/7.62X51 NATO to .223 Remington/5.5.56X45 NATO. Some of the things that were changed from .308 to .223 was the diameter of the bolt and the barrel extension to which the bolt rotates to lock into was reduced for the smaller diameter round. If the bolt diameter is deduced then the diameter of the carrier can also be reduced. If the bolt group is smaller then the upper receiver that holds the bolt group can also be smaller. If the upper receiver is smaller and the length of the cartridge is shorter then the lower receiver can also be shortened.

    My experience has been that the ATF set up the determination process to diminish the changes of litigation in bringing a firearm related product to market. Richard certainly knows what is required to get approval of firearm related products to market. Had I kept quiet and patiently waited my product would have been approved by now. There are those that feel that the determination process is not required. By the letter of the law, that is true. But unless you have very deep pockets, the ATF can make it very difficult to bring a product to market.

    Could the Max /15 series be scaled up from medium caliber AR-15 parts to use AR-10 parts? I would certainly think so. But because of the size difference of the AR-10 parts, it would require a whole different "upper" to accommodate those larger parts and bigger magazines. The real question is, is there a big enough market for a .308 upper to justify the cost of development? The same could be said for beltfed development. Time will tell.

    Scott

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    Bear in mind that a shoulder fired 7.6251 is much more difficult to control than a 5.56. This may, or may not, affect the number of potential buyers. If a beltfed 7.6251 upper became available, it's possible that a greater number of people would be interested.

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    Designed? Absolutely! Without getting into the engineering or marketing aspect of it, I would be curious as to how many people have any real time on a FA battle rifle, AR10, FAL, M14,G3 SCAR heavy, etc.? To me they are all pretty worthless in FA. They are just to light and the cyclic rate is to high. I did play around with the gas and buffers/springs on a AR10 (the most controllable of the 7.62 battle rifles IMHO) with a post sample DIAS and even though I could get the ROF down to around 800rpm, it was tough for me to get 2-3rd burst on a target at 100yds off a bipod. The weight just was not there. I have put about 15k of .308, 30/06 through a FND this year and can easily keep 2-4rd burst on targets out to 200yds (furthest I have shot it). The big difference? Weight (17.5-20lbs depending on which barrel Im using) and the ROF (400-700rpm). The FND is a BEAST even at 17.5lbs. I shot it in our assualt rifle match a month or two ago and it got really heavy shooting it off hand before long. I guess what I am saying is that in order to be useful, even as a toy it is going to need to be heavy. Would be people be cool with that? Regardless I would buy one!


    ***just remembered. The AR10 was actually pretty soft shooting with some 125gr, speer TNT bullets that I loaded moderately. Just for reference the AR10 I was using weighed 10.5lbs
    Chris Hipes
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    Like one of these ?
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    You're a madman Mike! looking good Sir. Let me know when it's available for the M11A1.

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    Paging theredneckengineer

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    Quote Originally Posted by mak91 View Post
    Like one of these ?
    how controllable is it? What's the rough weight?
    Chris Hipes
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    poulan10takethisoutsoidonotgetmorespam@yahoo.com
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    Quote Originally Posted by chili17 View Post
    how controllable is it? What's the rough weight?
    While I am enough of a mad man to shoot a 22lr with a 3d printed receiver, I'm just not mad enough to shoot a 308 with a 3d printed receiver. I hope to cut some hard parts in the near future and then I may have your answer. I don't expect it to be pleasant :-) One may ask why do it then? And to them I say "because I can".

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    Think "constant recoil" ....like Jim Sullivan did with the Ultimax ....otherwise there is no way a registered MAC receiver would ever last....

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    Quote Originally Posted by chili17 View Post
    Designed? Absolutely! Without getting into the engineering or marketing aspect of it, I would be curious as to how many people have any real time on a FA battle rifle, AR10, FAL, M14,G3 SCAR heavy, etc.? To me they are all pretty worthless in FA. They are just to light and the cyclic rate is to high. I did play around with the gas and buffers/springs on a AR10 (the most controllable of the 7.62 battle rifles IMHO) with a post sample DIAS and even though I could get the ROF down to around 800rpm, it was tough for me to get 2-3rd burst on a target at 100yds off a bipod. The weight just was not there. I have put about 15k of .308, 30/06 through a FND this year and can easily keep 2-4rd burst on targets out to 200yds (furthest I have shot it). The big difference? Weight (17.5-20lbs depending on which barrel Im using) and the ROF (400-700rpm). The FND is a BEAST even at 17.5lbs. I shot it in our assualt rifle match a month or two ago and it got really heavy shooting it off hand before long. I guess what I am saying is that in order to be useful, even as a toy it is going to need to be heavy. Would be people be cool with that? Regardless I would buy one!


    ***just remembered. The AR10 was actually pretty soft shooting with some 125gr, speer TNT bullets that I loaded moderately. Just for reference the AR10 I was using weighed 10.5lbs
    I also did a post sample DPMS G2 and it is pretty controllable. I need to do a video and clock the cyclic rate.
    Mine is using a 20" Hunter upper.
    I'm using a rifle length buffer tube, 308 Tubb flat spring, special spacer and the RB5015HD hydraulic buffer.
    I've tested using 8 different factory loads and surprised to see so much variation in the required ports sizes to run reliably.

    I personally don't see much of a market for a full auto 308 conversion upper.

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    As cool as a 308 upper would be it's not something I would be interested in. Intermediate calibers, 556, 7.62x39, 5.45, stuff like that is just so much more controllable. And cheaper to shoot. Especially with current ammo lunacy. Also would be a good bit of abuse to the lower.


    I'm still hopeful for the Ultimac and the Tenko! I'm a good ways down the list for the Max10/15. It'll be a while. I'm hoping by summer I'll get an email.

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    Quote Originally Posted by Deerhurst View Post
    As cool as a 308 upper would be it's not something I would be interested in. Intermediate calibers, 556, 7.62x39, 5.45, stuff like that is just so much more controllable. And cheaper to shoot. Especially with current ammo lunacy. Also would be a good bit of abuse to the lower.


    I'm still hopeful for the Ultimac and the Tenko! I'm a good ways down the list for the Max10/15. It'll be a while. I'm hoping by summer I'll get an email.
    Indeed Yes, a belt fed in 5.56, 7.62x39, for the match, game, and point. A real Win-Win in all aspects IMHO. Build it, and the will indeed come $$$.

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    Quote Originally Posted by Villafuego View Post
    Think "constant recoil" ....like Jim Sullivan did with the Ultimax ....otherwise there is no way a registered MAC receiver would ever last....
    If the upper was designed so that the bolt recoiled above the lower, and had a buffer tube attached to the upper vs the lower, minimal recoil should be transferred to the lower.

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    Quote Originally Posted by sniperdoc View Post
    If the upper was designed so that the bolt recoiled above the lower, and had a buffer tube attached to the upper vs the lower, minimal recoil should be transferred to the lower.
    You folks are the Wizz/Experts... could a hydraulic buffer, like the type used in the new high tech plastic SMGs, also be a good design concept? (No 100% printed frames/receivers poop plz. Great for some parts, and not so good for other parts.)

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    Quote Originally Posted by sniperdoc View Post
    If the upper was designed so that the bolt recoiled above the lower, and had a buffer tube attached to the upper vs the lower, minimal recoil should be transferred to the lower.
    There are a couple of things that the ATF focuses on as to whether an item is considered an "upper" or firearm. An "upper" does Not have fire control and the mechanism (the recoil spring) bears on the registered receiver. If the mechanism is contained within the "upper", especially with an open bolt mechanism, would tend to be considered a machinegun/firearm. Even if the "upper" is only considered a Title I firearm, it can not be used with a machinegun receiver as that would be one too many firearms firing automatically. For reference look up XMG upper.

    Scott

    ETA Y'all have a safe and enjoyable holiday.
    Last edited by A&S Conversions; 12-25-2021 at 10:01 AM.

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    Quote Originally Posted by A&S Conversions View Post
    There are a couple of things that the ATF focuses on as to whether an item is considered an "upper" or firearm. An "upper" does Not have fire control and the mechanism (the recoil spring) bears on the registered receiver. If the mechanism is contained within the "upper", especially with an open bolt mechanism, would tend to be considered a machinegun/firearm. Even if the "upper" is only considered a Title I firearm, it can not be used with a machinegun receiver as that would be one too many firearms firing automatically. For reference look up XMG upper.

    Scott

    ETA Y'all have a safe and enjoyable holiday.
    You'd probably have to build it with a "captured" Recoil Spring System that does not support the Bolt (ie, the Bolt would simply fall out of the Upper if not attached to the Lower). You'd also need a block that sits in the Lower (maybe through the Magwell?) that pushes the Bolt upward, as well as a way to trip the sear since the Bolt will be too high for normal operation.
    Otherwise, you'd need a "Locking Device" in the Upper which physically blocks the Bolt from any movement without the Block/Sear Trip mentioned above.

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    Would I buy one if it was available? Sure, would I shoot it much? Probably not. I have .308 select fire rifles and they are not very controllable. That does not mean they are not fun to shoot.

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    Quote Originally Posted by nklf View Post
    Would I buy one if it was available? Sure, would I shoot it much? Probably not. I have .308 select fire rifles and they are not very controllable. That does not mean they are not fun to shoot.
    X2. IMHO .308 is best in belt fed format.

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    Quote Originally Posted by sniperdoc View Post
    You'd probably have to build it with a "captured" Recoil Spring System that does not support the Bolt (ie, the Bolt would simply fall out of the Upper if not attached to the Lower). You'd also need a block that sits in the Lower (maybe through the Magwell?) that pushes the Bolt upward, as well as a way to trip the sear since the Bolt will be too high for normal operation.
    Otherwise, you'd need a "Locking Device" in the Upper which physically blocks the Bolt from any movement without the Block/Sear Trip mentioned above.
    Could you please go into more detail? I am trying to understand what you are saying. Are you saying that the bolt/carrier group would fall out? Most every rifle system I can think of is held over, under, or beside the magwell and has an ejection port 90 to 180 from the magwell. So where would the hole for the bolt group to fall out of be? Could a "Locking Device" be made? Certainly but how would such a device be only activated by the actual receiver? If this "Locking Device" could be held in the open position by something like a zip tie, the ATF can say that the "upper" is easily converted. I am not trying to mock or belittle. I am just trying to understand.

    Scott

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    Only large cal FA gun worth a crap for controlability would be the 1918 BAR. Or tri/bi pod mounted.

    Like many I have no interest in any FA over the typical 762x39 or 556 in rifle.

    I would want snatch a BAR up in a heartbeat and still am sick i passed on 4 BAR rifles that Mr. Ross ( famed author of unintended consequences) was selling for 8 to 12k each in the late 90's to pay for his cancer TX.

    Like many its a real easy pass on larger calibers in FA with light frames.

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