DPMS LPK's....do they all suck.

[Flatlander.54]

Got a DPMS LPK the other day and installed it in my stripped lower, it was absolute junk. Roll pins were borderline too big, selector spring and detent was so tight you couldnt work the selector, trigger pull is in excess of 10 pounds, 5 miles of creep, and feels like two pieces of 100 grit sandpaper rubbing together.
Anyone else have this trouble with a DPMS LPK?

[lmtrocks]

I used a DPMS lpk in a spikes lower recently. I've only built 3 lowers for myself but it worked fine. If the safety selector detent is too tight cut a couple coils off or grind down the detent a little bit...like 3 sheets of paper...

[SDDuc996]

Can't say I'm a huge fan of them. I was assembling a DPMS lower for a friend and when installing the roll pin for the trigger guard, the piece of the receiver (behind and to the side of the trigger) on the other side of where the roll pin sits broke off. I felt bad that I did that, so I swapped him for a Bushmaster receiver I don't use. I ended up using a MIAD on the DPMS and built an M4 for my dad.

[rebelEMPIRE]

My experience with DPMS LPK is that their roll pins are a little more tight than the others. But for me, that wasn't so much an issue since I don't 'hammer' them in. Rather, I 'press' them in slowly to avoid scratches, gouges and other potential damage. The trigger pull is less than great, but most of my shooting is short range. I've been using FailZero's exo-treated hammer, and it makes the trigger pull extremely smoother, like night and day.

-Lonni

[Eric]

Like many, they seem to be hit and miss. A recent one exhibited the same issue with the somewhat tight roll pins, especially for the trigger guard. I've had better luck with Stag kits.

[chase102798]

+1 for stag kits. Had good luck with a Daniel defense kit also. Had to think about it, but the one time I used DPMS kit, I remember having difficulties. I guess I just never tried to figure it out, I just took some time and did some parts fitting.

[JustMatt]

+2 for Stag
My only build using a DPMS lpk was gritty and the safety selector is super stiff.
Gonna use the Daniel Defense kit in the next build.

[federalist22]

I have the same problems with the safety selector, selector detent and detent spring that I used from a RRA LPK on my custom build. From reading what others have posted, I think any LPK is going to be hit or miss for standard parts.

I took my stiff safety apart last night to examine the detent and the spring after reading a thread on that problem. When I looked at the detent, it looked as though it was being ground down on the top (cuts and gouges in the tip).

So, to fix the problem I am throwing out the safety, detent, and spring.

I will be ordering DPMS replacements for all three parts from Midway.

[m24shooter]

Can't say I'm a huge fan of them. I was assembling a DPMS lower for a friend and when installing the roll pin for the trigger guard, the piece of the receiver (behind and to the side of the trigger) on the other side of where the roll pin sits broke off. I felt bad that I did that, so I swapped him for a Bushmaster receiver I don't use. I ended up using a MIAD on the DPMS and built an M4 for my dad.
DPMS has been known for spotty quality. However, the issue described above is not due to DPMS quality. The easy ways to prevent that are to use a large set of pliers and squeeze the pin in as described by another poster or to make sure that you have the ear supported on the underside with a small block of wood.
As for tight pins, if you use roll pin punches that center the pins while you insert them by use of an indexing bump on the end of the punch or a sleigh punch, that will help.
For the 10 pound trigger, I believe the allowable range of trigger pull in the TDP is 4 to 12 pounds, so 10 is still in the acceptable range. For grit, there are some parts that aren't machined well. Some fine stoning or polishing will go a long way towards improving that. Hitting the hammer and trigger pins with some steel wool, and then very finely polishing the trigger and hammer engagement surfaces can smooth out even some otherwise very bad interfacings.
Any LPK with obvious large forging/machining marks or rough surfaces should be replaced and is unacceptable. At the same time, realize that the TDP is not about match grade components. If you want a better chance of good parts, buy from one of the high end producers. Yes, they are probably made in the same place but the QC difference can be noticeable in terms of what is acceptable to go out the door and what is not.
As always, if you are working on a duty weapon the above tips should only be performed by someone authorized to work on your weapon.

[Quib]

I took my stiff safety apart last night to examine the detent and the spring after reading a thread on that problem. When I looked at the detent, it looked as though it was being ground down on the top (cuts and gouges in the tip).

So, to fix the problem I am throwing out the safety, detent, and spring.

I will be ordering DPMS replacements for all three parts from Midway.



Before you give up on that stiff safety, try this:

- Take a jewelers file and lightly round over the tip of the detent.
- Apply light grease or oil to the safety detent track and detent positions.
- Reassemble and function check.

I’ve personally “softened up” a stiff safety or two by following the above. The opposite can apply for a safety that is too soft. In that case:

- Take a jewelers file and re-contour the tip of the detent to a sharper point.
- Using the appropriate sized drill bit, clean up the detent positions in the safety.
- Reassemble and function check.

ETA: It also helps in certain situations, to take a jewelers rat tip file, and clean up the track the detent rides in on the safety.

[Quib]

Hitting the hammer and trigger pins with some steel wool.....

I like to take the trigger and hammer pins from new LPK’s and chuck them in an electric drill. I’ll then place a small amount of Brasso on a pistol patch and slowly turn the pin to smooth it up. I don’t go to the extent of removing the park, but I simply smooth up the exterior of the pins.

For the hammer and trigger to pin contact surfaces, I’ll snip a q-tip in half, dip it in Brasso and chuck it in the drill. I’ll then insert this into the FCG pin contact points and smooth them up as well.

The final step before reassembly and function check, is to apply Tetra grease or BF LP to the pins.

[m24shooter]

Good points Quib.

[federalist22]

Quib,

Thanks. Will do.

[SDDuc996]

DPMS has been known for spotty quality. However, the issue described above is not due to DPMS quality. The easy ways to prevent that are to use a large set of pliers and squeeze the pin in as described by another poster or to make sure that you have the ear supported on the underside with a small block of wood.
As for tight pins, if you use roll pin punches that center the pins while you insert them by use of an indexing bump on the end of the punch or a sleigh punch, that will help.
For the 10 pound trigger, I believe the allowable range of trigger pull in the TDP is 4 to 12 pounds, so 10 is still in the acceptable range. For grit, there are some parts that aren't machined well. Some fine stoning or polishing will go a long way towards improving that. Hitting the hammer and trigger pins with some steel wool, and then very finely polishing the trigger and hammer engagement surfaces can smooth out even some otherwise very bad interfacings.
Any LPK with obvious large forging/machining marks or rough surfaces should be replaced and is unacceptable. At the same time, realize that the TDP is not about match grade components. If you want a better chance of good parts, buy from one of the high end producers. Yes, they are probably made in the same place but the QC difference can be noticeable in terms of what is acceptable to go out the door and what is not.
As always, if you are working on a duty weapon the above tips should only be performed by someone authorized to work on your weapon.

That definitely makes sense, though the DPMS has been the only one out of seven lowers that I've done the same for. I do use a roll pin punch and try to use an armorers block underneath for support.