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Discussion Starter · #1 ·
Hi guys,
I've been getting a bunch of questions about the M, and since I don't have one I'd like to get some clarifications.

So the M Mini upper is a similar length as the L Standard?
M Mini vs Standard, do they share the same gas system length?
Assuming the same barrel profile, what kind of weight difference is there between the M Mini and M Standard?

The Mini seems more attractive due to weight saving. I'm just wondering if I'm pushing people the wrong way by recommending it.

Thanks!
 

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I will be criticized for this opinion, but I see no advantage to an M-Mini. Extra weight, size, blast, cost with little gain over a .300 BO L-Mini. I have a 7.5” 5.56 and it is a beast to shoot—noise, concussion, flame/flash, greatly reduced terminal ballistics. Barrels CAN be too short.

All M’s are heavy for their size, and plenty of weight is in the barrel. While longer is heavier, shorter is unpleasant and less effective. The monolithic receiver and metal stock are heavy either way. A longer upper adds only a little weight. Gas ports should generally be far away from the chamber. Longer barrels allow for that.
 

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I'm with CB3 on this.

I don't have numbers for you but I'd put money down that barrel profile is going to be a much more important factor fur weight than upper length.

With the type 3 gas system, mini gas length with standard upper would be my choice IF your barrel length won't allow for a standard gas. If you can get a standard gas length, I'd go with that.

For the same barrel length, the only savings a mini is going to give you is the extra gas tube, piston and upper length. It's America, do what you want but if weight is your only concern at that point, I think you're trying too hard.

The difference in weight between a mini and standard upper isn't something I would be real worried about but it depends on your ultimate goal.

Ymmv
 

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Discussion Starter · #4 ·
So on the M Mini it's something like a 9" gas system and the standard is around 11-12"?
Either way I'm not really interested in short barrels on a 308 or 6.5, something like 16 or 18"
Just looking at options to limit the weight if possible. I find the L standard upper to be long enough, that's about the same as the M mini, correct?
 

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Discussion Starter · #5 ·
Also, type 2 vs type 3 on the M? Type 3 just allows a buried gas block and has more adjustment, but is there a mechanical advantage outside suppressor usage?
 

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Personally, I’d rock a suppressed 12” 308 all day.

You’re not giving up all that much velocity and what you gain in maneuverability accounts for the loss in velocity. Plus now with 25rnd pmags available and the still relatively inexpensive bulk 308 that can be found, I think it’s a win win.

If you’re not going to run a can though, just go 16” on the barrel and get whatever upper length you feel comfortable with.


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TTEngineer, do you have a 12" 308 just curious how those that own them like them. I can't decide wether my next xcr is going to be a 12" M or a 18" comp length 556.
 

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Also after looking at their website I didn't see an option for a buried gas block with 12" barrel in the M, did I just miss it or what?
 

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I have a 12" XCR-M in .308 with the standard upper. AFAIK, RA is still not offering this configuration and you'd have to machine the upper to make it work like I did. Your factory options for a 12" bbl is an exposed gas block (mini length gas system) and a mini upper or a buried block (micro gas system) and mini upper.
 
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Sean, does your 308 have a standard length gas system or the mini?
Mini. Meant standard upper, mini gas (buried...sort of...type 3)

 

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No, but I’ve shot one with a can and loved it.


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While pistols are still currently legal....my 12" -M in .308 is kind of my go to travel across state lines rig. LPVO, Can, bipod and sling and enough gun to pack a punch in a package that fits in a standard size backpack. Hard to go wrong with that set up. Theoretically, I could pack an 18.6" bbl with mini gas block position too and not change pistons/gas tubes to reach out further.
 

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Sean's setup was my baseline for previous comment. I was thinking L standard 12" but per Sean's pics, that wouldn't work. Looks like you'd have to go 14"ish to use a standard gas length on a M. If you're ok with the extra length, I think that and a can is the sweet spot for compact/performance. 12", even with the shorter gas system is a nice setup for a good all arounder.

.......I might need to get an M again.....
 

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Sean that's a beautiful build you've got there, I really like how it protects the gas black but it's still easily accessible..
Thanks...I'm VERY happy with how it came out....I still need to really do more testing with it, but with ammo prices what they are...and the fact that in 4 days it may be illegal, I will probably be delayed in that endeavor. What it does do now is go bang every time with the cheapest of ammo...so I trust that part.
 
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Sean's setup was my baseline for previous comment. I was thinking L standard 12" but per Sean's pics, that wouldn't work. Looks like you'd have to go 14"ish to use a standard gas length on a M. If you're ok with the extra length, I think that and a can is the sweet spot for compact/performance. 12", even with the shorter gas system is a nice setup for a good all arounder.

.......I might need to get an M again.....
Yeah, for some reason a 14.7 with pinned FH and a comp length upper (buried gas block) holds appeal for me....just really like the longer handguards for some reason.
 
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I sure hope the pistol market doesn't go to hell in a few days... I sure want a shorty 308, but obviously at this point I'm on the edge of my seat like everyone else waiting for the other shoe to drop.. might just treat myself to an order if we have the luck of getting over this speed bump and are still able to "buy" such things...
 

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Yeah...betting it's all going to get ruled NFA and the 4999 worksheet doesn't really mean shit as they left a loophole saying if they feel like it's an SBR in spite of meeting all the criteria laid out in the worksheet, they'll prosecute you.
 

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I think I spoke to you about this elsewhere, but I'm of the opinion that the mini M gets you access to all the relevant .308 barrel lengths. 18.6" is JAG as 20" for what the cartridge can do with modern loadings, and 13" is the sweetspot, imo. I'm just waiting for Robarm to do a bit of painting so I can clone what @Sean K. did with his, albeit with a quad rail and 13" bbl.
 
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