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Author Topic: MDR Accuracy  (Read 1195 times)
AF Gunner
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« on: July 09, 2018, 09:07:35 AM »

I wanted to start this out because I have been getting terrible accuracy with my MDR. The sad part is I don't want to complain because I have a working rifle.  After this weekend I'm at around 950 rounds with my rifle and 460 since I last cleaned it. The short back story is nearly all of that is surplus M80 stuff from different manufactures, PMC, MEN, Lake City. With ball ammo the best I have done is about 3" at 100 yards. But most of my groups are 3 to 5 inches.

I thought it was me, but I have a friend that is really good with his bolts guns and he was getting the same. I shot some hunting rounds from 150gr to 180gr and had the same size 3-5 inches, this was done with the rifle clamped in a lead sled.

I did shoot one box of Sig Match Elite 168 OTM SMKs also in the lead sled and I was around 1.5 to 2.0 MOA. This is by far the best groups I have gotten with my rifle. I expect my rifles to be able to shoot around 1 MOA and am very disappointed that I have not been able to do so with my MDR. I want to be fair and do need to shoot some more match ammo, but I wanted to see what some of you are getting.



* pixlr_20180709080834317-Small.jpg (238.9 KB, 640x640 - viewed 70 times.)
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thehun
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« Reply #1 on: July 09, 2018, 09:32:14 AM »

MEN is probably the most accurate M80 ball out there other than, believe it or not, the Malaysian L2A2 out of semi-auto (American Eagle ball seem to do good as well from reports...but I haven't use them).

What were your groups with MEN? I don't have a MDR but my LMT MWS groups at 1.5-2MOA with MEN and L2A2...and .75MOA with 155gr TMK out of a 16" barrel (soon to be chopped to 13.5").

You might try 155gr TMK out of the barrel and see what happens...I know it has 1:10 twist...but the MDR might be like the LMT where it likes lighter match ammo vs the heavier stuff.

The military requirement for M80 ball is I believe 10" @ 600 yards for what its worth which is like 1.6-1.7 MOA at 100yards for reference...so if you are getting 2 or so MOA...I don't think you have much to worry about...but if you are grouping outside of 3" consistently with those ammos...you might give DT a call.
« Last Edit: July 09, 2018, 09:35:57 AM by thehun » Logged
Blackandwhiteknight
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« Reply #2 on: July 09, 2018, 01:21:03 PM »

AFGunner, I have been able to get MOA or better out of my MDR (coming up on 1300 rounds) but only with handloads.



 The thing that bothers me is the inconsistency.  What would normally be considered flyiers I think is attributed to something more fundamentally broken.  A while back I brought up the really low feed ramps as a concern, not only for reliability and feeding but accuracy as well.  With this much impact with the feedramp all kinds of bad things could be happening to the bullet while chambering. Here's what I'm referring too.



  I have completely written off using ballistic tip bullets of any kind due to concerns of bent and broken tips.  The other thing that may be happening is setback and tilt due to neck tension issues.  If the neck tension is off in one case compared to the previous it could shift the bullets alignment in the case neck, and it will engage the lands crooked.  Obviously not a good thing.  Even a little bit of setback will alter the chamber pressure, and thus consistency.   A lot of setback... well that's really bad, like kaboom bad.

  With the load I posted above I seem to be holding a real consistent MOA but I'm not sure I want to try many other loads. I think a moderate load behind a cannilured FMJ (mine likes 150's), with a solid crimp is about all the MDR will do.  Fortunately there are quite a few .223 bullets that should work really well, given the constraints of the MDR's design.  I almost think DT should post a warning about using non cannilured bullets in the MDR.  I'm sure that wouldn't go over well though...
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Siris
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« Reply #3 on: July 09, 2018, 01:58:06 PM »

AFGunner, I have been able to get MOA or better out of my MDR (coming up on 1300 rounds) but only with handloads.



 The thing that bothers me is the inconsistency.  What would normally be considered flyiers I think is attributed to something more fundamentally broken.  A while back I brought up the really low feed ramps as a concern, not only for reliability and feeding but accuracy as well.  With this much impact with the feedramp all kinds of bad things could be happening to the bullet while chambering. Here's what I'm referring too.



  I have completely written off using ballistic tip bullets of any kind due to concerns of bent and broken tips.  The other thing that may be happening is setback and tilt due to neck tension issues.  If the neck tension is off in one case compared to the previous it could shift the bullets alignment in the case neck, and it will engage the lands crooked.  Obviously not a good thing.  Even a little bit of setback will alter the chamber pressure, and thus consistency.   A lot of setback... well that's really bad, like kaboom bad.

  With the load I posted above I seem to be holding a real consistent MOA but I'm not sure I want to try many other loads. I think a moderate load behind a cannilured FMJ (mine likes 150's), with a solid crimp is about all the MDR will do.  Fortunately there are quite a few .223 bullets that should work really well, given the constraints of the MDR's design.  I almost think DT should post a warning about using non cannilured bullets in the MDR.  I'm sure that wouldn't go over well though...

I've not had any issues with any of the special tips my budy has been hand loading for me. The ramps dont look too different from the scar but I'll see if I can get a direct side by side tonight.
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AF Gunner
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« Reply #4 on: July 09, 2018, 02:58:09 PM »

I have not reloaded in a long time and probably wont start as I would need to purchase all new equipment and I'm not sure that is a rabbit hole I want to go down right now. I saw your post earlier on the bullet height and I have not polished my ramps yet, guess I need to do that. I would think some good M80 ball should at least give me 2 MOA, but as guys stated above, it's the flyers. I might get a decent 3 shot group then a flyer. I don't know, its just frustrating.

I also think being a Bullpup, it can be tough to get comfortable behind the rifle like a standard bolt gun. Which is somewhat what I was attributing the accuracy too... basically Me. But this last week I used a rest and was still seeing it. I think if I was see 2moa with ball and 1 or better with match, I would be fine.

I could still be me, but I'm thinking at this point something is up.
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Blackandwhiteknight
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« Reply #5 on: July 09, 2018, 04:19:43 PM »

I have not reloaded in a long time and probably wont start as I would need to purchase all new equipment and I'm not sure that is a rabbit hole I want to go down right now. I saw your post earlier on the bullet height and I have not polished my ramps yet, guess I need to do that. I would think some good M80 ball should at least give me 2 MOA, but as guys stated above, it's the flyers. I might get a decent 3 shot group then a flyer. I don't know, its just frustrating.

I also think being a Bullpup, it can be tough to get comfortable behind the rifle like a standard bolt gun. Which is somewhat what I was attributing the accuracy too... basically Me. But this last week I used a rest and was still seeing it. I think if I was see 2moa with ball and 1 or better with match, I would be fine.

I could still be me, but I'm thinking at this point something is up.

You should be getting a solid 2 MOA with M80. Mine does that easy.
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kfeltenberger
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« Reply #6 on: July 09, 2018, 05:04:18 PM »

My plan for the next trip is to use a Caldwell Lead Sled and do as much as possible to remove the human element while ensuring that the rifle is secured.  Also, I'll take 10 round PMags to remove the "monopoding" issue that longer mags cause.
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Kurt
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« Reply #7 on: July 09, 2018, 06:03:45 PM »

If you don't have 10rd PMAGS let me know...I'll lend you mine two for your testing...just throwing it out there.
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kfeltenberger
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« Reply #8 on: July 09, 2018, 07:47:59 PM »

If you don't have 10rd PMAGS let me know...I'll lend you mine two for your testing...just throwing it out there.

Thanks for the offer!  I have one that came with my Mossberg MVP, and that should suffice, but I still want to pick up a couple more because of PA's weird hunting laws and the hope that we will get the ability to hunt with semi-autos next year.
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Kurt
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« Reply #9 on: July 09, 2018, 09:54:04 PM »

Anytime.
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ney1
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« Reply #10 on: July 11, 2018, 03:23:08 AM »

Ensure your barrel block screws are tight, we red lock tight them from the factory.
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AF Gunner
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« Reply #11 on: July 11, 2018, 08:10:28 AM »

Ensure your barrel block screws are tight, we red lock tight them from the factory.

Thanks for checking in Nick!.

I checked torque on the two barrel screws frequently and they are always torqued down tight, I don't believe I have ever had them come loose. I did check them on my last range visit and the they were good. I will check to see if the red lock tight is present when I get home.
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mityno1
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« Reply #12 on: July 11, 2018, 08:41:38 AM »

Have you removed and reinstalled the barrel?

One reported problem with the SCAR-17 is that some have shipped with the "canted barrel" problem. That is where, for whatever reason, the barrel was not fully seated in proper axle alignment to the receiver. It was installed at the factory by FN just a little off-center, "canting," usually slightly to the left or to the right. It is easily fixed by removing and reinstalling the barrel fully seated squarely with the receiver.

My speculation here is that if FN has shipped some of its modular SCAR's with a very similar barrel mounting system as the MDR with the barrels canted slightly, I see that same issue as an MDR possibility since I have no MDR to verify this theory with. This possibility could easily be eliminated by removing and reinstalling the MDR's barrel just to make sure it is seated squarely before tightening the barrel screws.

Also removing the barrel would allow a close inspection of the chamber and mating surfaces with the receiver to make sure everything is clean and square with no burrs or other minor obstructions that could affect barrel alignment and accuracy.

No two rifles will ever shoot exactly the same, not even two sequential sequence number rifles off of the same assembly line on the same day. There are reasons for this.  Minute differences in tolerances and tolerance stacking are primary among these reasons. Just like no two barrel riflings are exactly the same, which is why modern forensics can do a pretty good job of matching fired projectiles to the firearm that fired them.

In your case, your accuracy appears to be far enough off from the average being reported from other MDR's that it has to be some factor more than normal minute variances. Hopefully, it will be something obvious that you can spot and correct yourself.  
« Last Edit: July 11, 2018, 08:45:08 AM by mityno1 » Logged

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AF Gunner
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« Reply #13 on: July 11, 2018, 12:04:22 PM »

The barrel has been on and off several times with similar results. Always torqued to the proper specification using a torque limiter. it's would hard to cant the barrel on the MDR because of the gas block and rail section. I could see maybe a slight variation, but not much because of the gas block and single rail still need to align with the receiver.
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knipple
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« Reply #14 on: July 11, 2018, 05:16:43 PM »

Have you removed and reinstalled the barrel?

One reported problem with the SCAR-17 is that some have shipped with the "canted barrel" problem. That is where, for whatever reason, the barrel was not fully seated in proper axle alignment to the receiver. It was installed at the factory by FN just a little off-center, "canting," usually slightly to the left or to the right. It is easily fixed by removing and reinstalling the barrel fully seated squarely with the receiver.

My speculation here is that if FN has shipped some of its modular SCAR's with a very similar barrel mounting system as the MDR with the barrels canted slightly, I see that same issue as an MDR possibility since I have no MDR to verify this theory with. This possibility could easily be eliminated by removing and reinstalling the MDR's barrel just to make sure it is seated squarely before tightening the barrel screws.

Also removing the barrel would allow a close inspection of the chamber and mating surfaces with the receiver to make sure everything is clean and square with no burrs or other minor obstructions that could affect barrel alignment and accuracy.

No two rifles will ever shoot exactly the same, not even two sequential sequence number rifles off of the same assembly line on the same day. There are reasons for this.  Minute differences in tolerances and tolerance stacking are primary among these reasons. Just like no two barrel riflings are exactly the same, which is why modern forensics can do a pretty good job of matching fired projectiles to the firearm that fired them.

In your case, your accuracy appears to be far enough off from the average being reported from other MDR's that it has to be some factor more than normal minute variances. Hopefully, it will be something obvious that you can spot and correct yourself.  

The MDR is packaged in a hardcase that is too short to use with an assembled MDR.  The MDR barrel is not installed in the receiver when you open the case.  You have to follow the instructions in the owners manual to assemble the rifle.
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Blackandwhiteknight
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« Reply #15 on: July 11, 2018, 08:37:37 PM »

Ensure your barrel block screws are tight, we red lock tight them from the factory.

Thanks for checking in Nick!.

I checked torque on the two barrel screws frequently and they are always torqued down tight, I don't believe I have ever had them come loose. I did check them on my last range visit and the they were good. I will check to see if the red lock tight is present when I get home.

The barrel block screws are the four smaller torx head screws that hold the block in the receiver.
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newguy2k3
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« Reply #16 on: July 11, 2018, 09:53:31 PM »

From the few hundred rounds I've put through mine it seems to be a little more accurate than my MWS. The poi seems inconsistent from day to day though. I haven't kept track of all the barrel r+I's and times I've cleaned it though so I can't link it to any one thing right now.
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HBeretta
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« Reply #17 on: July 11, 2018, 10:05:17 PM »

I expect my rifles to be able to shoot around 1 MOA and am very disappointed that I have not been able to do so with my MDR. I want to be fair and do need to shoot some more match ammo, but I wanted to see what some of you are getting.

I understand your disappointment Gunner, but it seems your expectations parallel the prelaunch speculation and alleged accuracy claims; DT never guaranteed 1 MOA - not implying you weren't aware.  3 moa or worse with ball sounds about right and agree that you need to burn through more match ammo to have a fair assessment rather than hoping for above average results with subpar ammo.
« Last Edit: July 11, 2018, 10:07:58 PM by HBeretta » Logged
AF Gunner
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« Reply #18 on: July 12, 2018, 09:24:31 AM »

The barrel block screws are the four smaller torx head screws that hold the block in the receiver.

Thanks for clarifying. I'll definitely check them.
« Last Edit: July 12, 2018, 09:28:56 AM by AF Gunner » Logged
AF Gunner
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« Reply #19 on: July 12, 2018, 09:28:05 AM »

I understand your disappointment Gunner, but it seems your expectations parallel the prelaunch speculation and alleged accuracy claims; DT never guaranteed 1 MOA - not implying you weren't aware.  3 moa or worse with ball sounds about right and agree that you need to burn through more match ammo to have a fair assessment rather than hoping for above average results with subpar ammo.

Agreed; however, I don't think MEN and Lake City should be getting 5 MOA. From what I have heard they should be around 2. I think the 1MOA and smaller would come for better ammo. If I was getting 2 MOA maybe even 3, I don't think I would have started this thread.
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