80% Arms lower incompatible with Magpul D50

[Guns and Radios]

 Anybody using a magpul D50 drum with an 80% arms brand lower? I have one and it will not function in my 80% Arms lower. I have 520 rnds thru the gun using Magpul 20 rnd Pmags with 100% reliability. I called Magpul and was told the D50 is incompatible specifically with 80% Arms lowers. Checking both the Magpul and 80% Arms website for AR-10 compatibility it looks like it should work.

[Belt Fed]

KInda strange, seems if the  20 round mags work the drum should also.

 

Welcome to the site and i'm sure someone with more knowledge than me will show up shortly.

[Belt Fed]

Also, nice looking rifle you got.

[DNP]

Is there some sort of clearance issue?  

[RacerX]

I would look at the difference between the drum and the magazines and see if something (e.g. shave a little off somewhere) can be modified to make it work.

Looking at the technical specs, there's a whole lot of things it's incompatible with.

 

Edited November 10, 2021 by RacerX

[shooterrex]

My drum works fine w/ PSA and Bushmaster lowers.

[Guns and Radios]

5 hours ago, Belt Fed said:

KInda strange, seems if the  20 round mags work the drum should also.

 

Welcome to the site and i'm sure someone with more knowledge than me will show up shortly.

Thanks that's what I thought also. Thanks for the nice reply I also posted on Reddit and got nothing constructive just excrement 

[Guns and Radios]

5 hours ago, Belt Fed said:

Also, nice looking rifle you got.

Thanks 

[Guns and Radios]

2 hours ago, DNP said:

Is there some sort of clearance issue?  

That what I think I can not see any differences between the part that enters the mag well between the drum and the Pmags. Just wanted to put the issue out to see if I could get a second opinion or someone else who has had that issue

[Guns and Radios]

2 hours ago, RacerX said:

I would look at the difference between the drum and the magazines and see if something (e.g. shave a little off somewhere) can be modified to make it work.

Looking at the technical specs, there's a whole lot of things it's incompatible with.

 

Can I ask politely what tech specs you looked at from what I read on the Magpul website it should be compatible. Here is their statement   NOT compatible with Armalite AR-10B, Springfield Armory M1A, Rock River Arms LARS, FN SCAR 17S, PTR-91, HK417 or any other rifles that utilize M14, FN FAL, or HK 91 / G3 patterned magazines. My lower is an AR/LR 308 compatible upper which it clearly states the drum is compatible with Thanks for the input and reply

[RacerX]

31 minutes ago, Guns and Radios said:

Can I ask politely what tech specs you looked at

 

The same technical specs section you pasted from.  Looking at it a second time, I do see now where they say it is compatible with DPMS LR308...  I skimmed right over that the last time.  Sounds like they need to update the "not compatible" caveat section.  I wonder if they actually tested (or had customers report) on the other brands, like 80% Lowers, 5D, Modulus, etc. 

The incompatibility is definitely curious.  I would grab a dial caliper and start taking some measurements to compare.

[Guns and Radios]

13 minutes ago, RacerX said:

 

The same technical specs section you pasted from.  Looking at it a second time, I do see now where they say it is compatible with DPMS LR308...  I skimmed right over that the last time.  Sounds like they need to update the "not compatible" caveat section.  I wonder if they actually tested (or had customers report) on the other brands, like 80% Lowers, 5D, Modulus, etc. 

The incompatibility is definitely curious.  I would grab a dial caliper and start taking some measurements to compare.

Thanks. What is your thought on the fact that I have cycled 600 rnds thru the gun using 15 different 20 and 25 rnd Pmags. If they work and as far as to all the measurements That I have taken the portion of the drum that enters the magwell are the same as the Pmags I would think the drum should work. I am wondering more towards buffer or spring issues.  my research shows that the spring pressure from the fully loaded drum is pretty strong. Any thoughts?. 

[Belt Fed]

5 minutes ago, Guns and Radios said:

my research shows that the spring pressure from the fully loaded drum is pretty strong. Any thoughts?. 

I was about to mention that just before i seen your post. that could play a role. 

[RacerX]

The spring difference was the very next thing I would expect as well, pending all measurements are the same.  Does the drum act any differently half-loaded versus fully loaded?

Edited November 11, 2021 by RacerX

[shooterrex]

Try the drum w/5 rounds. if it works increase the amount of ammo till failure. Might just be a strong spring that needs to be broken in. How much does your buffer weigh? What recoil spring are you running?.

[Guns and Radios]

On 11/10/2021 at 5:21 PM, RacerX said:

The spring difference was the very next thing I would expect as well, pending all measurements are the same.  Does the drum act any differently half-loaded versus fully loaded?

Have not had a chance to test that yet. It is one of the things I will do the next time I go shooting

[Guns and Radios]

On 11/10/2021 at 5:53 PM, shooterrex said:

Try the drum w/5 rounds. if it works increase the amount of ammo till failure. Might just be a strong spring that needs to be broken in. How much does your buffer weigh? What recoil spring are you running?.

Standard AR-10 Carbine buffer and spring I think its around 3.5 oz. I have it written in my log its just not handy right now. Five rounds then work up to failure sounds like a plan. I will try that next time I take it shooting.

[edgecrusher]

On 11/19/2021 at 2:16 AM, Guns and Radios said:

Standard AR-10 Carbine buffer and spring I think its around 3.5 oz. I have it written in my log its just not handy right now. Five rounds then work up to failure sounds like a plan. I will try that next time I take it shooting.

If it’s a standard Armalite AR10 buffer you may have it backwards, should be 5.3oz