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KAC RAS M4 8.9oz + barrel nut 2.5oz + FSB 5oz = 16.4 oz
DD Mk18 RIS II 14.1oz + DD Fixed Pic FSB 1.1oz = 15.2oz
I’m sure there’s some variation and fudge factor, but essentially they are the same weight, and the RIS is longer. In this thread: https://www.m4carbine.net/showthread...59#post2963559 we discussed weight a bit, comparing my M4A1 clones, the point being that even the M4 RIS really isn’t that much heavier than a RAS.
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I said "like..or something like that," as in I'm guessing. In any case, it's heavy.Originally Posted by Five_Point_Five_Six
There's not much information out there. The Mk18 bolts were breaking at random intervals, so they started putting out feelers for a tougher bolt. That's when LMT came up with the enhanced bolt. Colt figured out how to toughen up the legacy bolt at the last minute, at no additional cost, so that was the obvious choice.
Yea...and then they put a gas block under it, and then a backup iron front sight. Not exactly a fair comparison there, especially when you consider that the RAS has heat shielding built into it.
The weight distribution is also a factor. All I can say is I feel it. The mod 0 I can shoot longer without feeling fatigued.
Would definitely take a Mod 1 over a URG, though, that's for sure.
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I misinterpreted your comment about superiority then, my apologies. It's my understanding that the shift wasn't as a dramatic or relevant as hyped...but I do concede the RIS is a stronger/less flexible option.
If that's the case, then I would think the Super Duty 10.3" would be the most viable option. With their C158+ steel and forged bolt...you get increased lug strength/longevity but retain mil-spec component (vice KAC E3). So as far as DD vs Geissele as OP asked, that alone would sway me towards Geissele. To your suggestion, the controls/other components utilized in their Super Duty rifles would sway me from "building" a Colt. Dollar for dollar to spec out similar rifles it wouldn't be much savings.
Last edited by sidewaysil80; 10-14-21 at 09:16.
Senior Member
To be completely fair to Geissele, any lightweight free float handguard like that isn't going to play nice with optics. No matter how sturdy the lockup at the nut, just the flex alone is going to throw you off a few MOA. You can mitigate that by putting your optic further back on the rail, but then that kind of defeats the purpose of having the additional length in the first place. IMO, free float rails are for 3 gun, and then some very stiff, heavy duty ones for SPRs. I have no idea what a free float rail would ever be doing on a Mk18, but I guess that's really all beside the point. In any case, that rail alone on the URG is reason enough for me to avoid it.
Can't really speak to the Geissele BCG, but if we're going to speculate then I would be very suspicious of its implied greatness. The main problem with AR bolts isn't the material but the geometry. They screwed up by including a lug opposite the extractor. It places almost all the force on the two lugs adjacent to the extractor on either side. It wasn't a problem with the M16, and was only a slight problem with the M4. But when the Mk18 started being fielded in large numbers they started noticing a disturbing number of bolts breaking at random intervals. Side note on that, that's a prime example of why the TDP is so important, because of the large sample sizes behind the data that drives it. It's not like the Mk18 was the first AR15 SBR. It was just the first to be fielded in large enough numbers that the problem became obvious.
It's not just the lugs, either. The cam pin slot and the cam pin itself are also prone to failure. That was another area where LMT/KAC changed up the geometry. They also changed the shape of the lugs. As far as I know, all those changes were patented.
In any case, without some very extensive testing, it's impossible to know what changing the material alone will do for bolt life in SBRs. And if it's an improvement, how much of an improvement, if any, over whatever Colt came up with. If I remember right, they just tweaked the heat treat but kept the same material, and the prices didn't go up.
To make a long story short, if I were going to spend big bucks on a non milspec BCG, I would go the LMT/KAC route. That actually fixes the root of the problems, vs. just putting a bandaid on it.
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I did forget to count a gas block, but if you take a look at my math you’ll see that I accounted for a backup front sight. Adding a gas block would make the RIS II like an oz heavier than the RAS. The weight and balance difference is a wash, in my opinion. But, that is totally irrelevant to the OP.
What I will offer up is that DD is more of a known quantity than G, and I dig their rail. I’m fairly certain that they have supplied barrels to gov organizations over a significant time period. I think either gun will be fine, though I lean toward longer barrels than Mk18s these days.
Last edited by 1168; 10-14-21 at 10:16.
Banned
Colt didn't change the geometry, and only altered their heat treating process?
Is there any objective data floating around that supports this statement that they changed the bolt? This is the first time I am ever hearing of this.
Last edited by scooter22; 10-14-21 at 11:04.
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Just as a data point in reference to the original question, my Geissele 10.3 shot great. It appears to be properly gassed with ejection at 4:00 exactly with M193. I’m sure the H3 buffer helped. This will eventually wear a suppressor when it gets out of jail. Accuracy was fine and only hindered by me. 1.5-2 MOA at 100 yds with a PRO. I’m certain the gun is capable of much better. I fired exactly 120 rds between a quick zeroing and several drills and reliability was 100% during this time.
Member
Seems like his reputation among forum members started after rail-gate. It didn’t sit well with people when he promised to give more info before the holidays and just ghosted them. The whole bendy rail thing must have left me with some deep rooted trauma as I now shoot Colt LE6945 monolithic guns.
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Geissele's handling of the Black Friday fiasco left a rather sour taste in my mouth but I'm still not a hater. Them, Cloud Defensive, and SOLGW are three companies who I'll still buy products from but only from their dealer network.
Senior Member
It is what it is, and totally not his fault. I feel for him because the industry demanded something ludicrous, then cried foul when it didn't meet their impossible expectations. They wanted a Honda Civic with Suburban leg room, and they just can't understand why poor old Mr. Geissele can't defy the laws of physics for them.
Bottom line is if you want a 10-15 inch lightweight rail, it's gonna flex. And if you drop a 15 inch rail on the end, it's probably going to lose zero. If you want to attach optics to a free float rail, and have it hold zero, it's going to be heavy. No way around that. The original PRI on the Mk14 mod 0 is a good example what lengths you have to go to.
You are correct, though, monolithic is the right way to do it. Solves the root of the problem.
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