As some are aware I have been doing some serious deep dives and documentation on the MDRx performance, especially in 308.

I recently rechecked my locking block fasteners and they were loose.  It ends up the thread locker was improperly assembled at the Factory.

You may want to check and see if any of your screws are loose, especially if you have accuracy problems.

More details, reassembly instructions, and images here.

Thanks for the PSA. I'll check mine.

Did you contact DT about this?  I wonder what the torque spec on these?  Nevermind, it was in the link: Torque in a star pattern to 40 in-lbf

I wonder if Rocksett should be used on these?

Yes, I contacted DT and they provided the DT assembly instructions section.

You could use Rocksett, but I suspect that it won't ever come out again unless you submerge the entire rifle in a heated bathtub.  If you don't expect it to come off again, I'd try LT 263 first, as it replaced 262 and is rated for the size fasteners.  That being said, purple might work better as it is designed for these sized fasteners.  Both are rated to above 572 F which should be good for firearm use.

I am definitely interested to hear if yours were loose as well and what LT they used if they are loose.

Why would you ever need to remove it?

Not many reasons to, outside of a broken fastener.  Which a few people have reported happening.

Cool - look forward to your reviews. In particularly your accuracy behavior with heavy loads, and how well the zero holds when switching to different ammo.

Certainly, I generated a report a few months back you may want to take a look at.

https://www.ar15.com/forums/Armory/MDRX-308-ES-Tactical-Barrel-Performance-Post/43-535710/

I am currently looking at a substantially larger data set as well as trying out a few other ideas.  Will be a few months at least but will report back with the progress when it is available.

Sadly...spotty QC out of DT is the norm...

Here you go - Threw this up over in the AR15.com Precision Rifle sub-forum on my 6.5 CM MDRx.  

https://www.ar15.com/forums/precision-rifles/MDRx-6-5-Creedmoor/4-11264/?r=160463&page=1&anc=160463#i160463

Taking it out to 500 yards this weekend.  It did... OK.  around 2-2.5 MOA at 500 yards, but I'm here to tell you it took quite a bit of tuning and load development to get to even that.  This gun will give you 8 MOA in a hurry, if you aren't very careful on your ammo development.  Don't even try to run factory ammo.  Maybe .308 is better, but I doubt it as it will be subject to same chassy-flex and barrel whip under full load inherent to the gun.  An issue .223 shooters don't really see as the gun is a .308 chassy gun, that they download to weaker .223 which doesn't flex the receiver the same way.  JMHO; but there are a whole lot of options both cheaper and lighter and more proven for .223.  What makes this gun particularly unique is the ability to fire 1000+ yard 6.5CM ammo in a bullpup that you can also run CQB (because it's a bullpup) in the same magazine.  You can do that similar with the .308 version as well; but then, there are a spectrum of other .308 options out there in Bullpup.   That and I'm one of those insufferable Cross-fit / Vegan / 6.5mm fans (1 of those 3 is accurate).  And this is the only factory 6.5CM (or 6.5 ANYTHING) bullpup out there.  Which is why I got it.

New large scale community report is out in the wild and located here Lazy.

Also, did you check your barrel block fasteners?  We are so far seeing a 2 moa improvement in performance between loosening fasteners and factory tight fasteners.

Thanks.  FWIW, no, the screws holding the block to the reciever have not come loose on mine and I have maybe 1000 rounds in it now - I'll confirm later tonight.

Sounds good.

The OEM setting torque value is 40 in-lbf.  You will want to use a Wheeler Torque wrench or something else equivalent to +- 3 in-lbf full scale.

For comparison out of 9 people that tested their 308 chassis so far and told me about it.  Only 1 had person's chassis was tight, and his chassis was produced by DT 3 months before (of this year).

Went to 30 in-lb on the torque wrench and checked my block.  It's holding fine



1000 rounds on the gun - 6.5 CM version.

Thank you for the follow up.  It ends up that the one guy that tested his block screws prior that were tight tested again and were loose.  His chassis was produced early this year and included LT blue on 3 of the 8 screws, LT red on one of the screws, and 4 screws without LT.  So you have replaced him as the only one who hasn't detected loose screws yet in the responders so far.

Unfortunately you won't be able to improve accuracy by tightening loose screws.

Sounds like I got lucky, but I also had sent it back to DT early on, due to dissastifaction with the accuracy.   They say the replaced the barrel, and maybe they torqued and loc-tite teh barrel again or something on mine.   I will say, fat lot of good it did.  If you look at my photo, in the top right, you can see the top of the gas block (the little rail section sticking up, even with the rest of the rail).  If I grab the end of the barrel, I can move that with my bare hands. Which tells you how weak the entire barrel mount system is, if I can see that move in relation to the reciever portion, just by putting hand-pressure on the barrel.   Hence it wants mild force balance to actually shoot well.  So sure, I can see 5.56 guns with half the power level this gun was rated for, shooting great and acting free-floated.  But shoot what the gun was actually made to shoot, and the force balance is a very different level, and that whole barrel just flexes within the frame.  Which is why it took a heck of a lot of tuning for me to figure out how to get the gun down to 2-3 MOA, and to stop zinging flyers out 8 MOA or worse off to the side.  DT basically said this is normal, and not much I can do about it.

So alas, the whole point of the purchase was a 1000 yard capable bullpup that I can CQB with.  And being 6.5 Creedmoor and being a semi-auto from a precision rifle company like Desert Tech, I thought that this would be it.   I haven't sold it off, because it IS capable of 1000 yard performance - when I use mild loads of 130 gr or lighter bullets and am OK with 2+MOA.  But I won't be shooting any bullseye 1000 yard matches with it.  That, and it's the only .308 sized frame rifle I actually enjoy shooting.  The AR10 class rifles just aren't nearly as pleasant an overall experience to me as an MDR.

Interestingly, a lot of people bitch non-stop about the mechanical reliability of the MDRx. I'm here to say mine is rediculously reliable, and I would trust my life to it as much as most anything, it's been that good.  Curiously, I have found that bolt-lock is less reliable with I run S&B 6.5 CM brass.  My theory is that S&B I've found is known stiff as Hell, and as such, sucks up more energy scissoring into the ejection shoot, which is robbing me of just enough energy to prevent full bolt travel enough to lock.  Though that's just a theory.  Gun runs fine with any brass, just sometimes won't bolt-lock with that particular brass - same load as other brass.

Would I recommend an MDR?  TBH, not really. It's far too heavy to be a 5.56 platform, and it's not really accurate enough to realize the benefit of being offerend in 6.5 CM.  

Am I going to sell the MDRx?  Probably not, I actually quite enjoy shooting and running it.  I've figured out how to make it accurate enough for what I like to do.  And frankly, I'm a big 6.5mm diameter affectionato; and this is the one and only option for 6.5mm anything out there right now.   Give me an RDB in 6.5Grendel, and I'll have my everything-Gun; but those don't exist, sadly.  Weak 6.5CM ammo in the MDRx is about the same thing though (+2lb), and I can get 6.5 CM brass common as dirt.