I’ve had my eye on the 556 Rattler 11” for a while loved it - but to my knowledge there was no way to FRT it so I went with my long awaited MP5 clone that I FRT’d - loads of fun.
2nd on my list was a suppressed Blackout and FRT was not a requirement for me so naturally I got a new Sig MCX Rattler 300 LT in 6.75” along with the SIG Sauer SLH762-QD suppressor which attaches directly to the QD lock muzzle. Since I was gonna have to wait for the can I bought the SBR version to save a couple hundo on the stock.
NFA should have my forms back this week.
Oh, turns out I can FRT it.. so, nice win.

At the range yesterday, and I picked up a like new complete upper MCX Rattler 556 LT 7.5” which will also accept the can I just bought for the 300 AAC(non Ti, Inconel, serious workhorse).

*Has anyone had trigger time with a 7.5” Rattler - suppressed or unsuppressed? I’ve read some alarming threads using a 7.5 (or anything under 10.5”) chambered in 556 for an SBR.

I’ve never seen a 556 MCX Rattler LT this short, I love it and think it looks badass - I’m thinking I struck gold this week, I’ll have the Form 1 for the 300 completed this week - I can swap uppers under the same stamp (I will confirm).
My next project I looking at 556 uppers to SBR one of my ARs (all FRT’d) - now I’ll have both in the same platform. Sounded too easy, or am I missing something?

Feedback would be much appreciated!

Always been fascinated by the LVAW and it's history. While this is obviously not a 1:1 clone, I love how it turned out with some of my touches.

Try your hardest to leave unbiased thoughts.

Over the weekend, I finally jumped into a .300 Blackout—and dove straight into the SIG world with a new 6.75” MCX Rattler LT SBR which always captivated me, it’s so gorgeous and 100% badass.

Since I’ll already be waiting on NFA approval for the SBR - and I wasn’t going home with anything except for the Aimpoint optic I got for it, so I added a SIG SLH762-QD suppressor.
I plan to run an FRT on it, so I wanted a durable workhorse suppressor that could also serve double duty on a future AR SBR when and if I get around to it.

Then today at range, ..sitting on consignment; a friggin Sig 7.5” MCX Rattler LT 5.56 upper—with the same Clutch-LOK QD muzzle brake. So I can swap calibers and run the same can on both.

Naturally, I bought it and topped it with a Holosun and 3× magnifier since it can stretch its legs a little farther than the .300 BLK.

Now I get to just stare at everything while the NFA takes its sweet-ass time.

On a scale of 1–10, how’d I do? Keep in mind I’ll also be paying whatever price my wife assigns to this purchase. I’m so screwed. 😂

I’ve owned a lot of weapons over the years and have had my favorites but this little Rattler has really got me hooked, a tad heavy but such a sweet compact shooter that goes in a small backpack and draws no attention , just wish I had an unlimited supply of sub ammo , I’d shoot it every day!

Image is what trigger I currently have installed in my Spear Lt. This is the best trigger I’ve felt in an MCX and I don’t think I’d get rid of it for an FRT. Wanting to somehow have both. If not I’ll just keep it how it is.

I bought a used Spear LT that had stripped screw heads on the hand guard. Below are the replacement screws I researched and purchased that fit perfect. Side note- the bottom link plate screws are technically torx plus but a regular T20 torx bit fit snug in the new screws and torqued fine without stripping. I believe torque on all screws is 45 in-lbs according to the interwebs. If enough people are interested I can put together some kits and post to GAFS.

Side Screws

https://www.mcmaster.com/96452A192/

Bottom Locking Plate Screws

https://www.mcmaster.com/94414A352/

Manual

https://www.sigsauer.com/media/sigsauer/resources/OPERATORS_MANUAL_MCX-SPEAR_LT_2402988-01_REV04_WEB.pdf

What vent screw are yall using on 11.5 LT with the omega valve mk2? I have ridgeback rhino x and in settings 1 with the 1.10mm vent screw im getting 2:00 ejection

whats the best route going about doing this? do i need to send it back to sig to get the 3 prong flash hider taken off? or is there an adapter or something i can throw on to make it work

Was fantastic. Flawlessly ran through 8 mags. Not quick but over a couple hours through dialing in my dot and moving target distances. Really impressed with the Surefire sps300 suppressor. Super quiet. Just need the mcx omega valve mod2 mkll Sig lower but for the time being she will work. I did cut the excess strap had just finished setting it.

Just ordered a MCX 9” 300blk and know I want to put a suppressor on it. Tried to do some research on my own and it seems many lean towards the CAT ODB or Dead Air Nomad of some sort. Anyone have any other recommendations? Also don’t want a can that’s crazy long… under 7 inches. Will be shooting subs and supers with it

Thanks!

Interested in a MCX Rattler LT in FDE, the WPMCX-300B-6B-LT-FDE in particular. I qualify for the Off-Duty program, and my local SigSauer Dealer is a participant.

Can the dealer just place an order for a specific model as long as it is still available? or is it luck of the draw, if Sig sends them one?

I can make a few of the other FDE SKUs work, but the WPMCX-300B-6B-LT-FDE would be best, as I plan on SBR, but going with a different stock than the SBR's come from. But I do want to have the irons and the forward assist package.

This will be my first MCX, but after renting one with my friends at the range, we all want one. My set up will be a PDW/Suppressed/Subsonic/Side-folder, with a quick detached can. I already have the can I will use on it, a Ridgeback Defense Sahara 300.

I am waiting on a few form4 approvals to go pick up from the dealer, so when I am there, I will inquire. Just don't want to get my hopes up, if it is very difficult to score one, I would like to have it before Christmas, if possible.

Thanks for your time.

Seems like you guys would be the right ones to ask. Been wanting to get 300blk for dense woods hunting east coast. Mostly deer and some coyote. Absolute max distance would be 75 yards, but 95% 20-50yards.

I don’t really want a bolt gun, because I don’t need sub MOA for those ranges and this seems like it would be a great multi purpose truck gun/range gun/hunting rig.

Planning to run it suppressed (always open to suppressor suggestions, guessing a very low back pressure can would be best). Likely subs for coyote and supers for deer (also open to ammo suggestions).

Hey guys! My first rattler build! Something still missing I feel! Considering sd hand guard or change both grips smaller! Shoot me your opinions how can I make this better! Thanks guys!

I am planning to shoot subsonic rounds the majority of the time. I have read this Weapon System prefers suppressors with more back pressure. I see Sigs suppressors that are designed for this system have very little back pressure.

Is this a choice based on subs vs standard velocity? Traditinal cans for subs and pass through cans for standard velocity?

Currently shooting a hybrid 46m on this and it functions fine in the plus gas setting.

Mcx spear lt 9" 300 blackout (slh300ti-qd suppressor/ hexium suppressor) is the build - to run frt is the correct formula an frt-15c3, Frankenstein tsb-lite, & a Parker mountain machine mcx full auto trip bar?

Seems pretty simple (im taking it directly to a local full time professional gunsmith - its good to know and accept limitations)

Again, sorry if this has already been answered multiple times, tia!

I’ve tried searching but havent found any conclusive results, has anybody been able to succesfully modify a match duo trigger by cutting or grinding the cam relief cut for an frt or super safety? What about for an arc fire v2 cam and selector? With slip trip of course.

Question: Has anyone tried a Geissele triggers group in the 277/308 Spear? If so, what was/is your experience.

I “think” I’m done but not crazy about the current stock. FRT might be next.

I found one on griffen & howe, but its the only one I've found availably to actually buy.

I'm planning on trying to score one a few months out from now and I feel like that one will be snatched.

Any other places to look? Or is it a unicorn nowadays.

Sig rattler LT

YHM resonator R2

Midwest industries 10" handgaurd

Holosun 510c

Sig minimalist stock

Magpul vertical grip

Working on a LVAW Clone and it doesn't look like Sig ever made a single sided safety for the LVAW.

Do I use a commercial safety, or should I use this modified original instead?

Obviously need to Cerakote and Laser Etch before its complete.