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I own a DPMS AR-15 Sportical and I have a problem.

This is a discussion on I own a DPMS AR-15 Sportical and I have a problem. within the M16 AR15 forums, part of the Rifle Forum category; It's a smooth side. It fires 556 and hates 556 NATO. How does one upgrade it to handle NATO. Or should I just sell it ...


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Old August 6th, 2012, 08:00 PM   #1
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I own a DPMS AR-15 Sportical and I have a problem.

It's a smooth side. It fires 556 and hates 556 NATO. How does one upgrade it to handle NATO. Or should I just sell it and use the money for a M1A.

I bought it years ago put maybe 500 round through it and only just now realized it can't take NATO even though the dealer told me "it's mil spec it will take anything the military uses." or somthing to that effect. I got it for around $200 new. I got suckered into the Obama ban thing when he was voted into office.

I know I need a new upper to have the dust cover forward assist etc. Striped upper is about $126ish from dpms.


NATO is to hot for my rifle and causes double/triple feeds and tears the sides of the shell off.

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Old August 6th, 2012, 08:39 PM   #2
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First 200 for a new ar is a great deal. I would go to a heavier recoil spring and buffer. I use an H2 heavy recoil buffer and a wolff extra power buffer spring. That should slow down your bolt some and hopefully keep it from tearing up your brass. You probably looking at about 40-50 in parts and if it doesn’t work then just keep those parts for a future build.

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Old August 6th, 2012, 08:40 PM   #3
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What kind of warranty does DPMS have?

If the barrel is marked .556 it should chamber and shoot .556.
I'd call DPMS and see about getting it fixed first.

Thanks from louie and Philz M1A
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Old August 6th, 2012, 08:42 PM   #4
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It's marked 556 but not 556 NATO like I see on the oracle dpms. I believe it's a 4 year warranty.

It's amazing what you can get when a dealer does a bait and switch on you. Came with a eotech too :p for an extra $200


Last edited by Wolfstanus; August 7th, 2012 at 12:58 AM.
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Old August 6th, 2012, 08:48 PM   #5
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It's not a total loss, you don't need a new upper if you don't want to spend the money.

A lot of people these days feel that the slick side is more desirable, as the forward assist is superflous and may actually cause more malfunctions. If the rifle won't chamber the cartridge, then there is probably something else going on and it's probably worth performing corrective action anyway.

As far as the .223 vs 5.56 thing goes. Pick up a barrel from any of the reputable makers- BCM, Noveske, Centurion, Daniel Defense, Rainier Arms, and many others. Have a reputable smith install it for you. I would suggest picking up a new BCG, or at least a new properly made bolt to go along with it.

Or, you could just get a new upper from any of the above mentioned companies. Your lower should be fine.

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Old August 6th, 2012, 10:04 PM   #6
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lol he suggests you build a new rifle... other than the receivers thats what that amounts to.

can you be more specific about what you mean about it doesn't like NATO?

If your saying it has malfunctions.. then play with the buffer and spring first...


in one thread you said 400 now your saying 200 .. and with an eotech..dude are we talking dollars or pounds sterling?

you got a "too good to be true deal"on that rifle.. maybe call NICS and see if it has a body count or something. (only half serious)

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Old August 7th, 2012, 12:47 AM   #7
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Double feeds, triple feeds and rips the lip of the rounds off or fails to eject and if it does it does eject properly it fails to chamber. But 223 has no problems.

I was at work and using a phone. Had no time to correct. Correcting. Eotech did not have proper papers for it as it was a floor model and they "found" a eotech box for it. The DPMS was a "sorry we sold your custom rock river ar to some other guy." $400 in total and bought a German 98k that day at a ffl that does not try to sell anything to you and let's you hold and work the weapons action. Maybe it's failures are why I got it for cheap.



I have since sold the 98k and added a magpull pistol grip and magpull trigger guard. No internal changes to it so it's fairly bone stock. Also the setup has changed. Forward grip is all the way to the end of the rail. Eotech is further up and the light is on the left side rail and all the way forward.


Last edited by Wolfstanus; August 7th, 2012 at 01:21 AM.
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Old August 7th, 2012, 04:21 AM   #8
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Sounds like you've got a problem on your hands. Otherwise known as typically shoddily-built DPMS product.

Despite the barrel being marked 5.56, you more than likely have a .223 chamber. You can have a gunsmith use a reamer and remove some material to make your chamber properly-sized, then try it with some different ammo and see how it does. If it were me, I'd look at that issue first, followed by a quick gas system check, and then check out the buffer/spring.

If it were me, I'd get the rifle's issue(s) fixed so it worked properly, then sell it. Considering that you can buy a Colt LE 6920 at a local Wal-Mart for just over a $1,000, that direction might work out a little better for you. Just saying.

HTH, and good luck to you.

Thanks from Philz M1A
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Old August 7th, 2012, 07:47 AM   #9
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Looking at the photo I'd say you have a timing issue.

You have a 16" barrel with a 7" carbine length gas system, yes?

Your 5.56 ammo is likely keeping the chamber pressure high for longer than your .223 ammo. As the bullet passes the 7" mark gas bleeds back to cycle the action. But, with the bullet still in the barrel and the hot 5.56 powder keeping the chamber pressure high the case will still be gripping the chamber at the same time the gas system is trying to open the bolt /carrier and yank it out. It ends up jumping or ripping the rims, and causes misfeeds due to shorter cycling.

The easiest way to fix it is to choose different 5.56 ammo, or stick with .223 which has a lower chamber pressure. Other ways to fix it is to have a shorter length barrel after the gas port so the bullet exits sooner and drops chamber pressure sooner. Or, you have a longer gas system; mid length if you want to stick with 16", or go a longer barrel with a rifle length gas system. The AR was designed around a 20" barrel with rifle length gas system, so with anything shorter you increase the risk of timing issues.

Replacing the buffer and spring with a heavier one will also help by slowing the start of the cycle, hopefully until the chamber pressure drops to a level where case friction is not an issue.

Your chamber is probably what it says it is; 5.56NATO and is probably fine.

Can you give us any more detail on the type of ammo are you using? Along with the damage are the 5.56 spent cases noticeably dirtier, especially round the neck, than the .223?


Last edited by Klem; August 7th, 2012 at 08:01 AM.
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Old August 7th, 2012, 08:23 AM   #10
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Don't just ream out the chamber. If the metallurgy wasn't meant for 5.56, then you're asking for problems with fatigue which could lead to catastrophic failure down the line. It's not a huge probability (check out Vuurwapen Blog's comparison of .223 and 5.56 on luckygunner), but it is a risk.

The reason you are having so many problems with the firing sequence with NATO ammo is that the gas port in the barrel is probably drilled too large. That works fine for .223, which is lower pressure, but the higher pressure 5.56 spec is feeding way too much gas back down the tube and causing violent action. NOTHING will fix that except a replaced barrel.

Either stick to shooting .223 until the barrel reaches the end of its life, or replace the barrel and bolt.

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Old August 7th, 2012, 08:40 AM   #11
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Quote:
Originally Posted by DisposableHero View Post
Don't just ream out the chamber. If the metallurgy wasn't meant for 5.56, then you're asking for problems with fatigue which could lead to catastrophic failure down the line. It's not a huge probability (check out Vuurwapen Blog's comparison of .223 and 5.56 on luckygunner), but it is a risk.

The reason you are having so many problems with the firing sequence with NATO ammo is that the gas port in the barrel is probably drilled too large. That works fine for .223, which is lower pressure, but the higher pressure 5.56 spec is feeding way too much gas back down the tube and causing violent action. NOTHING will fix that except a replaced barrel.

Either stick to shooting .223 until the barrel reaches the end of its life, or replace the barrel and bolt.
The gas port being too large is both unlikely, and unlikely to be causing your problems. I say this because the gas volume is limited by the standard diameter of gas tubes (0.120").

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Old August 7th, 2012, 09:18 AM   #12
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I'd stick with the .223 rounds until you decide what to do with it. For 200 bucks you've got a cheap plinker.

Thanks from svandamme
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Old August 7th, 2012, 09:32 AM   #13
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Was using green tip if that tells you anything.

I'll try the buffer spring.

If I buy a new rifle it's going to be a M1A. Been wanting one for years.

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Old August 7th, 2012, 09:54 AM   #14
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Quote:
Originally Posted by Klem View Post
Looking at the photo I'd say you have a timing issue.

You have a 16" barrel with a 7" carbine length gas system, yes?

Your 5.56 ammo is likely keeping the chamber pressure high for longer than your .223 ammo. As the bullet passes the 7" mark gas bleeds back to cycle the action. But, with the bullet still in the barrel and the hot 5.56 powder keeping the chamber pressure high the case will still be gripping the chamber at the same time the gas system is trying to open the bolt /carrier and yank it out. It ends up jumping or ripping the rims, and causes misfeeds due to shorter cycling...

Replacing the buffer and spring with a heavier one will also help by slowing the start of the cycle, hopefully until the chamber pressure drops to a level where case friction is not an issue.
A properly built carbine functions just fine with a 16" barrel and a carbine-length gas system. I've got one - Colt 6920 - that's had a diet of nothing but 5.56 NATO ammo and it's a very soft shooting and reliable carbine. I agree that a TDP-standard buffer spring and an "H" buffer is much more preferable than a regular carbine buffer, and considering the OP has a DPMS, I can pretty much guarantee that he's got a generic buffer spring and an unmarked buffer.

Quote:
Originally Posted by Klem View Post
Your chamber is probably what it says it is; 5.56NATO and is probably fine.
This is a known issue with DPMS and quite a few other manufacturers (Olympic Arms being another) that will mark a barrel "5.56" and still utilize .223 Remington chamber dimensions.

Thanks from BSalty

Last edited by ArmyCPT; August 7th, 2012 at 11:19 AM.
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Old August 7th, 2012, 10:17 AM   #15
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I know my dpms lower was out of spec. The mag catch was way too low. It caused the rounds to strip half way off the mag and stop. I found that by using a micrometer and comparing the measurements to my friends in spec BCM lower.

Granted, I know your situation is different but I would double check anything with a dpms label and compare it to known in spec parts.

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