Sean Nack,
a ‘drum’ is a magazine with a circular or spiral feed of cartridges and no belt. I think what you’re thinking of are ‘belt boxes’, which hold belted rounds in a box (which may be round). The Germans call theirs belt holders for the MG42/MG3 ‘sturmtrommeln’ or ‘assault drums’; and the RPD circular belt boxes are usually called ‘drums; but this is really just a confusing special case usage… generally speaking, a ‘drum’ means it doesn’t use a belt.

I don’t have any experience being shot at; but I do think that having the *option* of giant-capacity magazines is a good one. Jerry Miculek points out that 100-round Betaco mags actually stick out the bottom less than 30-round magazines, so you can get down into a lower prone position with them. Jim Sullivan has said that they timed a man on the move trying to load a new belt into an M249 and it was over 20 seconds; whereas a mag change takes only a few seconds (even if it’s a giant mag). So there’s a lot to be said for magazines of various sizes, to suit your tools for the task at hand.

I have no idea what happened to the Shrike. Rumor has it that there’s a trickle of them coming out. It seems like a pretty good idea and I’d love to get ahold of one; but I also wonder why other companies haven’t picked up the basic idea… I suspect there’s non-obvious flaws. (price possibly being one of them, durability likely to be another). If the concept could be perfected tho (which may require a whole new platform — keep in mind that the Stoner 63 wasn’t adopted in large numbers either) it may be the best of all worlds, offering belt and magazine feed (of whatever magazine size you can make work with an AR15) with no parts change.

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You don’t need a fancy thermostat (that WILL break) to switch from closed bolt to open. What’s the need of a SAW to fire from the closed bolt anyway? Its not meant to be a precision weapon, It just needs to put down suppressive fire. If the barrel heats up you can just change it on a 249.

I think this is a waste of time and money for nothing. Why did we stop using the BAR in the first place? Fire Power!! I think we are better served with linked ammunition.

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Ditto on the RPK question. The first thing that popped into my mind upon hearing of the USMC IAR project, was that the RPK is exactly the sort of weapon the fills the IAR role.

As far as box vs drum feed, the Chinese and Singapore seemed to have been happy using drum fed squad automatic weapons, unlike the Russian RPK experience. I understand the Chinese made drum for the RPK is somewhat different and much easier to load and unload than the Russian design.

I have also heard rumors that the Russians experience from fighting in Grozny influenced them to prefer 7.62×39 caliber weapons to those in 5.45mm. Supposedly the 5.45mm was inferior for shooting through walls, floors, ceilings and other typical urban cover. That sort of area fire would seem to directly reflect on caliber selection for a squad automatic.

(Maybe it’s a good thing for the new Iraqi army that 7.62×39 RPK remains the squad automatic weapon?)

I appreciate the problem the USMC is trying to solve with the IAR. The USMC fire-team needs an automatic weapon suitable for suppression and the assault roles, given the limited quantity of people in a fire-team. The M-249 is too clumsy for use in assault.

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As for the magazine vs. linked ammo debate, why not both? How about a modular weapon system that can be configured as magazine only, belt only, or both magazines and belts. There is only one real option for a M249 companion/replacement, the Shrike Modular Weapon System. Light weight, dependable, field configurable and all mounted on the familiar M16/M4 lower receiver. What more could you want? Add the open bolt/closed bolt fire controls of the LWRC IAR or the FN IAR and you would have the perfect IAR contender. But why stop there? With the Shrike’s belt feed capability, it could replace the M249 entirely. And with no stamped metal bits to tweek, it may even be Gomer friendly.

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The open bolt/closed bolt cutoff switch in the FN IAR is not electronic. It’s functions by a little tab of metal (either a thermocouple or a shape-memory-effect alloy) that changes shape as the chamber heats up and flips the switch. Sort of like the mercury vial in a thermostat.

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The Soviet got rid of their drums. The RPK-74 use box magazine, no drum.

Drum are unreliable and not durable enough for the battlefield. 100 rounds drum is over 3 times heavier then a 30 round magazine. The spring has to push three time weight at a speed that can keep up with the rifle cycle. That’s is very hard to do consistently. When a full loaded drum drop to the ground it can/will be damage. Any damage to the drum will effect reliability (Thomson’s drums are notorious for this).

I am surprise the Marine want drum magazine. Countless hours and money has been thrown at it over 100 years to make it work.

40 or 45 rounds magazine are the way to go IMO. They’ve proven to work.

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Has anyone used the Russian RPK ( http://en.wikipedia.org/wiki/RPK ) or one of the semi-automatic clones. How does it compare with the SAW.

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“The IAR shall utilize a magazine with a capacity of 100 rounds (Threshold). The magazine shall permit rapid visual determination of the number of rounds remaining (Objective). Magazine Compatibility. The IAR shall accept and function with the current Marine Corps service rifle (the M16A4) 30 round magazines.”

https://www.fbo.gov/index?s=opportunity&mode=form&id=a8698386e4300ceee7bc1067a71dab5c&tab=core&_cview=0

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