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Posted: 1/29/2015 11:36:31 AM EDT
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Lookng at this DPMS bull barrel upper to buy.
The owner says it does not feed from the mags dcmp sent him, all 3. does not feed in the sense of does not strip from the mag. The bolt hits mag lips he says. Is this a mag problem or something more serious? He saus he never shot it. Secondly, whats a good price for this upper? PO is not the original buyer and round count is unknown, I am thinking 330-350 maybe? I will examine it today. |
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There are two generations of DPMS dedicated 22 uppers. The first generation the bolt is patterned off the Colt 22 conversion which uses a completely different magazine than the second generation. The second generation bolt is patterned off the Ruger 10/22 bolt design and is also used in JP Enterprises and Nordic 22 uppers. The second generation DPMS uppers use the same magazine as the CMMG/ TAACOM / Atchisson style of 22 uppers with mags from Black Dog Machine and CMMG.
It is possible he is trying to use the wrong magazine with his DPMS. IF it definately has the correct mags then a little more information available or pictures might help trouble shoot the problem. Generally both generations of DPMS function best with high velocity ammo when new. Since the bolt seems to be hitting the feed lips I'd bet it is a Gen 1 upper and he's trying to use BDM style mags. The gen one DPMS bolt is cylindrical in shape and there are two guide rods which screw into a barrel collar which slides over the barrel on assembly. This style upper requires a mag with built in ejector and mags are not readily available for gen one DPMS uppers but they are accurate. |
Here is a photo of a Colt 22 conversion and a DPMS Gen I bolt.
Here is a photo of a DPMS Gen I 10 round mag. 
Here is a photo of a Colt conversion mag next to a DPMS Gen I mag. Colt has a tab on the front which mates to a notch under the chamber insert. 
This is a photo of a BDM 30 round mag designed for the Colt/ DPMS mags, notice the ejector formed into the inside feed lip. 
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| whether it is the old pattern or the new pattern upper, the problem may be with the lower that is being used. if the magazines are being locked in too high, they will interfere with the bolt. if possible, test the upper with different lowers and see if it makes a difference, if it doesn't then the upper is out of spec. a possible cure might be putting O-rings on the front and rear lugs of the upper to gain a bit of clearance, put as thick an O-ring as possible so it is a bit of a strain to push the take down pins into place. and again, try it with different lowers. |
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