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M400 Barrel Nut & Handguard Cross-Compatibility

1832 Views 0 Replies 1 Participant Last post by  McSweeney
Good evening y’all!

As we are all more than likely aware, the M400 series of rifles & large format pistols (Tread, Snakebite, Predator, Switchblade) are all outfitted with Sig’s proprietary barrel nut featuring it’s own unique handguard “mounting pattern”. It looks like this:
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Now, I don’t want to get into the specific issues because that isn’t the focus here so let’s just say that finding some handguard options that do not require removal of the barrel nut could potentially be very helpful to some owners...That said, I have researched and found a few “cross-compatible” handguard options and would like to catalog them here. There are also a couple “potential candidates” that I have not yet had the opportunity to check for fitment. I will list these as “possible fits” in hopes that someone here can offer their opinion, expertise and/or experience. Please share what worked for you. Help add to this list if you can!

1. Samson Mfg. SXT M-Lok
A perfect fit out of the box, this handguard is an easy job as well as a high quality and practical option as an upgrade to the M400’s stock hand guard. Take a look at the barrel nut included:

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Seems almost like they were influenced by the M400? Well, in fact, this handguard is included from the factory on the M400 Elite model. Available at a variety of lengths and featuring a full-length picatinny top rail, this is a great option.

2. Luth-AR Palm Handguard
This is another option that just happens to fit the stock barrel nut. Offered in M-Lok, Keymod or Smooth, this is a cost-friendly option that also fixes the issue of the absent top pic rail.
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3. Ruger AR-556 Stock Free Float M-Lok
This is another coincidental direct fit and although they are not easy to find and most were marked with Ruger’s logo, they work and could be used in a pinch.
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4. AIM Sports M-Lok/Keymod Freefloat
These hand guards are reported to fit the M400 barrel nut as well. They are offered in many sizes and configurations and include a barrel nut that looks very similar to Sig’s.
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5. KAK Industry M-Lok Freefloat
These hand guards are very new to market and I have not been able to test their fitment as of yet. However, from the looks of their barrel nut, it would definitely be worth attempting. Let me know what you think...
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Although I have a few more potential options, I think that is where I will leave off for now. I may have a few more to add in the near future. In the meantime, I would love to hear from anyone who has any experience or opinions on this. Thank you for reading!

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