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Author Topic: MDR Chamber Questions  (Read 287 times)
mityno1
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« on: May 17, 2018, 11:31:23 PM »

Some theories have been tossed around about perhaps some MDR's with issues being related to the chamber design.

If this were true, a competent gunsmith could make a casting of the chamber of an MDR with RR issues (Rim Ripper).

This chamber casting could then be measured and evaluated to determine if it is within either 7.62x51 or .308 specifications and if it is not, and the chamber is tight, perhaps the chamber could be reamed to acceptable semi-auto specifications.

Yes, if this were the case, this might open her up to say 2MOA accuracy in exchange for reliable reliability, but who wouldn't make that trade-off besides a very few. Law enforcement would as the typical engagement is not only inside of 100 yards but is likely to be well within 50 yards. I would think law enforcement would be looking for the increased firepower of .308 in a compact an easily portable package that could defeat more levels of cove and body armor and 2MOA that is reliable would more than serve that purpose.

A 1MOA rifle that is not reliable and is difficult and time-consuming to clear malfunctions will get you killed.

I pose this MDR chamber thread because while it may prove that the chamber is fine and the issues are gas and/or timing related, the possibility of a non-standard chamber being used must be considered until it can be eliminated from the equation.

There are reasons to deviate from standard specification chambers and the .223 Wylde is proof that some deviations offer improvements over standard dimensions, especially in accuracy. However, the MDR being a new design with a new gas system could cause chamber deviations that work well on other platforms not to work so well on the MDR.

I am suspicious of the MDR's chamber until several MDR examples have been accurately measured and published to determine exactly what they are. I say this because you can do a lot to a bolt gun's chamber to improve accuracy that will simply not work in semi-automatic. I could see that the fact DT is a word class bolt gun maker might tempt them to employ some bolt gun chamber accuracy tricks like tightening up some chamber dimensions rather than making them looser for improved semi-auto reliability.

I can also see that by not making their own barrels in-house, DT is at the mercy of their supplier and checking every barrel received for chamber dimension tolerances would be an impossibly long and expensive task. But if it is found there is a problem with MDR's chamber dimensions, not doing so may bankrupt the company or at least kill off the MDR. 

Gas system and timing issues will be difficult to impossible to diagnose by most gunsmiths.

But accurately measuring chamber dimensions should be easy for most decent gunsmiths and that is why I propose those with the ability to have their MDR's chambers measured please do so in order for this possibility of the cause of many reported malfunction issues to be confirmed or eliminated.

 
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Re: MDR Group Buy - official BPF list!
Reply #360 on: January 04, 2015, 05:29:50 AM
(Still waiting patiently on an FDE...)
kfeltenberger
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« Reply #1 on: May 18, 2018, 12:48:37 AM »

I can also see that by not making their own barrels in-house, DT is at the mercy of their supplier and checking every barrel received for chamber dimension tolerances would be an impossibly long and expensive task. But if it is found there is a problem with MDR's chamber dimensions, not doing so may bankrupt the company or at least kill off the MDR. 

Regardless of whether DT outsources the barrels, makes them in house, or cultivates them in the lower 40 acres, each and everyone should be tested for fit and function when its received for assembly and then after assembly. Just because the barrel is "to spec", there is also a barrel extension that needs to be figured into the equation and that could be where the issue is.  Faxon knows what they're doing and I don't think they'd send a customer something that wasn't to that customer's spec, and after watching the interviews that Ian and Karl did with them, their QC is pretty thorough.

Just a thought way past midnight.
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Kurt
Blackandwhiteknight
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« Reply #2 on: May 18, 2018, 01:18:30 AM »

I can also see that by not making their own barrels in-house, DT is at the mercy of their supplier and checking every barrel received for chamber dimension tolerances would be an impossibly long and expensive task. But if it is found there is a problem with MDR's chamber dimensions, not doing so may bankrupt the company or at least kill off the MDR.  

Regardless of whether DT outsources the barrels, makes them in house, or cultivates them in the lower 40 acres, each and everyone should be tested for fit and function when its received for assembly and then after assembly. Just because the barrel is "to spec", there is also a barrel extension that needs to be figured into the equation and that could be where the issue is.  Faxon knows what they're doing and I don't think they'd send a customer something that wasn't to that customer's spec, and after watching the interviews that Ian and Karl did with them, their QC is pretty thorough.

Just a thought way past midnight.


I've held off concerns about anything barrel related because I know Faxon runs a tight ship, and I'm sure their stuff is good.  Barrel extensions, that's a different story.  Same goes for headspace.  That said, if DT requested something specific Faxon may have done it for them, even if it was a bad idea. It's quite possible DT gave specific dimensions based off their experience with bolt guns thinking it would work.  Semi autos and bolt guns are two different games.  You would think Faxon would say "you sure about that?"  But hey, who knows.  All speculation.
« Last Edit: May 18, 2018, 01:57:13 PM by Blackandwhiteknight » Logged
mityno1
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« Reply #3 on: May 18, 2018, 03:19:21 AM »

 Faxon knows what they're doing and I don't think they'd send a customer something that wasn't to that customer's spec...

But exactly what is that chamber spec, is the question at hand.

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Re: MDR Group Buy - official BPF list!
Reply #360 on: January 04, 2015, 05:29:50 AM
(Still waiting patiently on an FDE...)
thehun
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« Reply #4 on: May 18, 2018, 08:00:45 AM »

I can also see that by not making their own barrels in-house, DT is at the mercy of their supplier and checking every barrel received for chamber dimension tolerances would be an impossibly long and expensive task. But if it is found there is a problem with MDR's chamber dimensions, not doing so may bankrupt the company or at least kill off the MDR. 

Regardless of whether DT outsources the barrels, makes them in house, or cultivates them in the lower 40 acres, each and everyone should be tested for fit and function when its received for assembly and then after assembly. Just because the barrel is "to spec", there is also a barrel extension that needs to be figured into the equation and that could be where the issue is.  Faxon knows what they're doing and I don't think they'd send a customer something that wasn't to that customer's spec, and after watching the interviews that Ian and Karl did with them, their QC is pretty thorough.

Just a thought way past midnight.

This. FAXON is not a rookie on this...its to DT's spec...second...you are talking about spending money on a rifle you shouldn't have to spend ANY money making it more reliable...that is expected from any manufacturer that quite honestly charges above $1500 for a non AR based rifle.
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mityno1
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« Reply #5 on: May 18, 2018, 11:58:09 AM »

This. FAXON is not a rookie on this...its to DT's spec...second...you are talking about spending money on a rifle you shouldn't have to spend ANY money making it more reliable...that is expected from any manufacturer that quite honestly charges above $1500 for a non AR based rifle.

It isn't very hard or expensive to do:

https://www.youtube.com/results?search_query=chamber+casting

And probably more than a few MDR owners have everything they need including micrometers. It is pointless to cast the chamber without the micrometers needed to accurately check the casting.

In other MDR news, the barrel extension is now looking to be the more likely culprit of many malfunctions. If the barrel extension is deforming the projectile and brass going into the chamber, then it could account for pressure spikes and extraction problems.

See this thread: http://bullpupforum.com/index.php?topic=13106.0
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Re: MDR Group Buy - official BPF list!
Reply #360 on: January 04, 2015, 05:29:50 AM
(Still waiting patiently on an FDE...)
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