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Mid length vs. Carbine length Gas Systems


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#1 BTSmith10

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Posted 11 September 2016 - 09:10 AM

I'm trying to do some research on my next AR. Right now I have a cheap DPMS and eventually (I do have a kid due any day now) I want to upgrade to a Daniel Defense.

I'm drawn to the idea of having a fixed front sight; so that narrows it down to the V1 (carbine length gas system) and the V3 (mid length gas system). That is really the only difference I can see between the two models. They both have 16' barrels. I do like the 12' rail on the V1, but I'm assuming that would be easy to change. My use for this new rifle would be general purpose focused on home defense.

My question is this - what would be the the pros and cons of each system?

#2 pira114

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Posted 11 September 2016 - 12:32 PM

Mid length gas systems are supposed to offer the ability to go with longer hand guards and lower overall felt recoil.

The downside to me is that there still doesn't seem to be an agreed upon standard gas port dimension. That and parts commonality in regards to gas tube goes out the window compared to standard carbines.

#3 AaronK

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Posted 11 September 2016 - 04:07 PM

In my experience, for whatever reason a mid length recoils "flatter" where as car length has more muzzle rise.

#4 BTSmith10

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Posted 11 September 2016 - 04:31 PM

So the carbine length is sufficient for a 16" barrel?

#5 jvandivere

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Posted 11 September 2016 - 07:22 PM

So odd question- was looking at barrels- what's the difference between mid length and rifle length? I know the difference between rifle and carbine... Is Mid and rifle interchangeable terms? Looking at a 18" barrel build SPR/3gun rifle.


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#6 AaronK

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Posted 11 September 2016 - 08:08 PM

Rifle is longer than mid
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#7 pira114

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Posted 11 September 2016 - 11:07 PM

So the carbine length is sufficient for a 16" barrel?


Yes

#8 Spartan24

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Posted 12 September 2016 - 08:17 AM

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Now, here's where it gets tricky, and I'm lost on this, but don't different gas lengths require different weight buffers? For instance, don't rifle length gas systems need heavier buffers?


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#9 pira114

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Posted 12 September 2016 - 12:48 PM

Buffer weight has been another issue, but I believe that the better manufacturers have it pretty well figured out.

To use an example, I only have experience with BCMs mid length. I want to say they kept the standard "milspec" gas port size for carbines. In which case the H buffer works well. But I've heard others say they needed a regular weight buffer in a different brand of mid length.

Reports of short stroking or bolt over ride are common with home builds of mid length systems. Major quality brands bought complete have much less reports I think.

With these reports, it's impossible to know if under or over gassing was the issue. Or if buffer weight tweaking was a solid solution or just a band aid. Again, there's no TDP for mid length since it's a civilian proprietary creation. Even then, only Colt and FN have the TDP for the M4 or M16 variety. So everything else is kind of a reverse engineered job. But they've done that we'll for decades.

I'm not a hater of mid length. I see the benefits. But I also see the upside to using a system that's been around and figured out decades ago. And I love being able to switch parts from most any carbine to the next. So I'll stick with carbine length.

#10 B3dlam

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Posted 12 September 2016 - 07:55 PM

All things being equal a mid length gas system puts your gas block mounted front sight further down the barrel than a carbine length gas system this results in a longer sight radius (~2" longer).  A longer sight radius means it is in theory easier to be more precise in your sighting. If you're set on having a fixed front sight vs a rail mounted sight.  A rail mounted sight mounted front sight can increase your sight radius by roughly 3-6" over what you would get with the mid length so more food for thought.


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#11 Psybain

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Posted 12 September 2016 - 08:42 PM

I have a ddm4v1 and I love it. No non-user-induced problems over the last 4 years. I only have a little more than 1000 rounds through it, almost all of which were done when I lived in nc. I'd like to get a middy eventually, but the v1 does everything I need it to do.

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#12 jvandivere

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Posted 13 September 2016 - 10:29 AM

I'm thinking of building either a 16 or 18" faxon barrel upper with mid or rifle length gas system- using either an ACS or PRS stock- Looking at the Vseven systems upper and lower. not sure. Would be SPR/3 gun use and some tactical stuff I suppose.


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