DPMS 308 Woes

[knownalien]

So, the empty cartridge did not touch the feed ramp going in, dropped to full seating depth in the chamber freely, then you dropped (closed) the bolt and the cartridge had scratches and a distorted mouth after extraction?

yes. the distorted mouth could have come from the spring loaded pin in the bolt pushing it towards the side, though.

 

[clandestine]

Its normal to dent the case mouth. Its what the ejector does if its working properly. The spring should be very strong but the ejector should never stick, it should always pop back once depressed.

The ejection problem is likely a combination of a tight chamber, rough chamber, narrow ejection port, wrong size gas port, obstructed gas system, or a gas leakage.


If the Bras is Striking the front of the ejection port too son it will jam consistently. A mill should be used for this. You basically want to lenghten the ejection port forward about 1/4", sometimes a 45 degree bevel from the inside helps too. Sharp edges on the inside make it hard for the brass to get out. The bevel helps the brass walk out of the gun.

The Gas Key is likely leaking gas, so you remove it, seal it with Green Loctite, install the Gas Key and retouque the 2 bolts, then restake.

To fix the chamber issue you need a .308 and 7.62 NATO set of headspace gauges. If all headspaces right then the throat me be too shallow. A Reamer can addres that but unless the bulet is engaging the rifiling thats not necesary. Removing too much throat will make the gun shoot like crap.

Then the chamber needs to be polished to a mirror finish.

If the gas system is leaking the Gas Block could have a bad seal or obstructed port. Check the port size and oversize if necessary. Check the gas block for obstrustions along with the gas tube. Once all is clear degrease everything and green Loctite the Gas Block to the Barrel and reinstall clamping screws or cross pins and blow air into the barrel from a compressor to clear any in the gas path so the loctite dont obstruct the barrel or gas path. It very important to be sure the gas tube is perfectly straignt and the end (In the receiver isnt dinged ot undersized). If the gas tube is not straight the carrier gas key will damage it (Ruining the gas seal), or will prematurely wear one side causing gas leakage.

If the feedramp is rough or improperly cut it can deflect the bullet when feeding causing casings to stick, it can also shave brass and copper off causing the chamber to get rougher or cause extraction problems.

Replace the Gas Rings, its just a precaution. Make sure there a good seal. Use an air comprees in the gas key to see if air will kick the bolt out of the carrier.

If the extractor dosent have enough of a hook or tension replace the extractor, extractor spring and add a insert to improve extractor strength. The Extractor may need to be polished in key areas to keep it from gouging the brass when feeding. Shaving can accuminate and cause the gun not to extract.

Has a replacement stock been installed? If so a fixed stock screws can protrude into the buffer tube too far and limit bolt and buffer travel causing problems. If the bufer tube is bent or out of spec it can cause cycling problems.

Get a New Buffer and Buffer Spring

Be sure the hammer isnt notched and replace if it is. Polish the Hamer Face, Bolt Botom and the bottom of the 3 lower Bolt Head lugs.

Check the firing pin and cam pin to see if they bind up. if they do the gun wont lock and unlock right. It will also give light firing pin strikes. If any parts binf replace them.

 

[knownalien]

^^^ about two of those things I can do (maybe). I think I read loctite in there. this rifle's gonna be like the ugly step-child.

 

[clandestine]

^^^ about two of those things I can do (maybe). I think I read loctite in there. this rifle's gonna be like the ugly step-child.

No. If its professionaly done you wont notice a thing. None of this work should be visible except the polished parts. None of it. If you can see any of this work the person doing the work is a hack.

The polishing has to be precise. no rounding parts or edges or grinding, JUST polishing. You want minimal metal removal. the more metal you remove the softer the metal will be underneath. On the surface its still super hard.

BTW only use Magpul PMags as well. i hate the DPMS mags. Those things are junk.

 

[MrWhiteRabbit]

1) at the neck (that is a stock photo), there are lines that run parallel north to south. can't be "rifling" because that part shouldn't need it.

2) the mouth of the rim becomes distorted and is no longer perfectly circular. not super distorted, but enough

I imagine the bent mouths would be common, especially if it's normal to have that strong of an ejection spring.

I think your rifle is in need of professional help at this point. It sounds like clandestine is willing to look at it for you, or that other armored who chimed in earlier.

 

[knownalien]

Its normal to dent the case mouth. Its what the ejector does if its working properly. The spring should be very strong but the ejector should never stick, it should always pop back once depressed.

The ejection problem is likely a combination of a tight chamber, rough chamber, narrow ejection port, wrong size gas port, obstructed gas system, or a gas leakage.


If the Bras is Striking the front of the ejection port too son it will jam consistently. A mill should be used for this. You basically want to lenghten the ejection port forward about 1/4", sometimes a 45 degree bevel from the inside helps too. Sharp edges on the inside make it hard for the brass to get out. The bevel helps the brass walk out of the gun.

The Gas Key is likely leaking gas, so you remove it, seal it with Green Loctite, install the Gas Key and retouque the 2 bolts, then restake.

To fix the chamber issue you need a .308 and 7.62 NATO set of headspace gauges. If all headspaces right then the throat me be too shallow. A Reamer can addres that but unless the bulet is engaging the rifiling thats not necesary. Removing too much throat will make the gun shoot like crap.

Then the chamber needs to be polished to a mirror finish.

If the gas system is leaking the Gas Block could have a bad seal or obstructed port. Check the port size and oversize if necessary. Check the gas block for obstrustions along with the gas tube. Once all is clear degrease everything and green Loctite the Gas Block to the Barrel and reinstall clamping screws or cross pins and blow air into the barrel from a compressor to clear any in the gas path so the loctite dont obstruct the barrel or gas path. It very important to be sure the gas tube is perfectly straignt and the end (In the receiver isnt dinged ot undersized). If the gas tube is not straight the carrier gas key will damage it (Ruining the gas seal), or will prematurely wear one side causing gas leakage.

If the feedramp is rough or improperly cut it can deflect the bullet when feeding causing casings to stick, it can also shave brass and copper off causing the chamber to get rougher or cause extraction problems.

Replace the Gas Rings, its just a precaution. Make sure there a good seal. Use an air comprees in the gas key to see if air will kick the bolt out of the carrier.

If the extractor dosent have enough of a hook or tension replace the extractor, extractor spring and add a insert to improve extractor strength. The Extractor may need to be polished in key areas to keep it from gouging the brass when feeding. Shaving can accuminate and cause the gun not to extract.

Has a replacement stock been installed? If so a fixed stock screws can protrude into the buffer tube too far and limit bolt and buffer travel causing problems. If the bufer tube is bent or out of spec it can cause cycling problems.

Get a New Buffer and Buffer Spring

Be sure the hammer isnt notched and replace if it is. Polish the Hamer Face, Bolt Botom and the bottom of the 3 lower Bolt Head lugs.

Check the firing pin and cam pin to see if they bind up. if they do the gun wont lock and unlock right. It will also give light firing pin strikes. If any parts binf replace them.

i wonder if I can forward this to DPMS and watch their head explode?

 

[clandestine]

i wonder if I can forward this to DPMS and watch their head explode?

I wouldnt recomend shoving that summary in front of any gunsmith/armorers/techs face or the manufacturer. The DPMS guys may not even know what the heck Im talking about. Generally, they dont take to well to it, they want to troubleshoot it their own way (Or perhaps pretend to troubleshoot it).

Best bet is to give a detailed account of what has been replaced, how many times DPMS has serviced it, how many rounds have been fired. How often it jams, what type of jams, any parts replaced, and some fured brass if you have it.

 

[MrWhiteRabbit]

Generally, they dont take to well to it, they want to troubleshoot it their own way (Or perhaps pretend to troubleshoot it).

... A fourth time.

 

[clandestine]

... A fourth time.

Really? 3 times?

How often is this thing failing to fire and eject? Percentage wise?

 

[MrWhiteRabbit]

Really? 3 times?

How often is this thing failing to fire and eject? Percentage wise?

Knownalien will be along shortly with details, but he was delighted to get ten rounds in a row to fire correctly while we were at Hap on Sunday.

 

[knownalien]

Knownalien will be along shortly with details, but he was delighted to get ten rounds in a row to fire correctly while we were at Hap on Sunday.

I'd say out of 30 rds, we had issues with 6 or 7.

here's the guns history . . .as told to the white rabbit . . . . foibles and all.

one day I got my gun; I was happy. It was beautiful. Only, I thought the gas block was a little ugly.

I wanted to replace it with this:

The gun had never been fired. I was unable to unscrew the set screws in their gas block. I stripped them. Beer was involved. A hammer came out. A hammer banged the shizznit out of the gas block and marred it to high hell. It came off. So did the barrel! Popped the indexing pin right off. Called DPMS and asked if they could at LEAST put the indexing pin back in. "Sure," they said. I sent in the upper. They, out of pitty, replaced the barrel, gas block and gas tube, figuring maybe the screws were cross threaded. Needless to say, I was happy. I noticed a minor issue from the get-go with the rifle. The latch of the charging handle never really securely latched to the upper (I think the groove in the upper was too shallow). so I went to shoot it. this same issue happened like every 5th round. went and bought retail 7.62 ammo, just to be sure. same thing. Sent the upper in. Their note said "faulty upper; replaced; tested 20 rnds rem UMC." I was elated. Took it to the range. This time, I bought their Rem UMC ammo (.308: what they used) just to be able to tell them I did. Same issues. Teared up. Sent it back to them with the empty box of ammo and in a seperate box I sent Federal 7.62 for them to try. Their response was "bolt letting go of spent case too early . . . .replaced bolt; fired 10 rnds of customer's ammo and 50." got it back. Took it to the range with Mr Rabbit and the rest is history. Same issues.

anyone looking for a club???

 

[platekiller]

Oh yeah and if you really feel the need to give it away I am always open for donations.

Still holds true. Seriously how much are you looking to get out of it?

Platekiller

 

[Weber]

Yup, how much you want for a rifle that doesn't work?

 

[knownalien]

Still holds true. Seriously how much are you looking to get out of it?

Platekiller

I had not thought of a number since my goal was to get it working.

Yup, how much you want for a rifle that doesn't work?

it'll work . . . . just not 100% . . . . maybe 80% of the time

 

[rseymorejr]

I'd say out of 30 rds, we had issues with 6 or 7.

here's the guns history . . .as told to the white rabbit . . . . foibles and all.

one day I got my gun; I was happy. It was beautiful. Only, I thought the gas block was a little ugly.

I wanted to replace it with this:

The gun had never been fired. I was unable to unscrew the set screws in their gas block. I stripped them. Beer was involved. A hammer came out. A hammer banged the shizznit out of the gas block and marred it to high hell. It came off. So did the barrel! Popped the indexing pin right off. Called DPMS and asked if they could at LEAST put the indexing pin back in. "Sure," they said. I sent in the upper. They, out of pitty, replaced the barrel, gas block and gas tube, figuring maybe the screws were cross threaded. Needless to say, I was happy. I noticed a minor issue from the get-go with the rifle. The latch of the charging handle never really securely latched to the upper (I think the groove in the upper was too shallow). so I went to shoot it. this same issue happened like every 5th round. went and bought retail 7.62 ammo, just to be sure. same thing. Sent the upper in. Their note said "faulty upper; replaced; tested 20 rnds rem UMC." I was elated. Took it to the range. This time, I bought their Rem UMC ammo (.308: what they used) just to be able to tell them I did. Same issues. Teared up. Sent it back to them with the empty box of ammo and in a seperate box I sent Federal 7.62 for them to try. Their response was "bolt letting go of spent case too early . . . .replaced bolt; fired 10 rnds of customer's ammo and 50." got it back. Took it to the range with Mr Rabbit and the rest is history. Same issues.

anyone looking for a club???

If it aint broke fix it till it is!

 

[knownalien]

I think I can add this for my gunsmith friends: I can offer any of you $150-$200 cash to fix this problem. I will also buy any parts needed (though they may take time to get). If it can't be fixed, or that amount of money is insulting (I have no idea what to offer, but it is all I can afford), then I must get rid of the rifle

I think I could part with it for less than 1/2 of what I bought for it. $500?

p.s. I was never looking for a handout. It's not my way, and esp. not in this economy.

 

[MrWhiteRabbit]

Dude, clandestine is a gunsmith and he's in (or maybe near?) you in GB. Why don't you drop him a PM and make an offer?

If that doesn't work out, the guys at Gun Connection are a longer drive for you, but good with ARs, too.

Foregoing all that, I call dibs, and can hand you cash tomorow. (all transfer laws apply.)

 

[knownalien]

Dude, clandestine is a gunsmith and he's in (or maybe near?) you in GB. Why don't you drop him a PM and make an offer?

If that doesn't work out, the guys at Gun Connection are a longer drive for you, but good with ARs, too.

Foregoing all that, I call dibs, and can hand you cash tomorow. (all transfer laws apply.)

can you post the pic you took? Mike from DPMS just responded to my email. there inclination is to blame it on the ammunition. If I send it back to them, I will (in a seperate box) send them nearly every 7.62 I have!!!

 

[wilcam47]

I'd say out of 30 rds, we had issues with 6 or 7.

here's the guns history . . .as told to the white rabbit . . . . foibles and all.

one day I got my gun; I was happy. It was beautiful. Only, I thought the gas block was a little ugly.

I wanted to replace it with this:

The gun had never been fired. I was unable to unscrew the set screws in their gas block. I stripped them. Beer was involved. A hammer came out. A hammer banged the shizznit out of the gas block and marred it to high hell. It came off. So did the barrel! Popped the indexing pin right off. Called DPMS and asked if they could at LEAST put the indexing pin back in. "Sure," they said. I sent in the upper. They, out of pitty, replaced the barrel, gas block and gas tube, figuring maybe the screws were cross threaded. Needless to say, I was happy. I noticed a minor issue from the get-go with the rifle. The latch of the charging handle never really securely latched to the upper (I think the groove in the upper was too shallow). so I went to shoot it. this same issue happened like every 5th round. went and bought retail 7.62 ammo, just to be sure. same thing. Sent the upper in. Their note said "faulty upper; replaced; tested 20 rnds rem UMC." I was elated. Took it to the range. This time, I bought their Rem UMC ammo (.308: what they used) just to be able to tell them I did. Same issues. Teared up. Sent it back to them with the empty box of ammo and in a seperate box I sent Federal 7.62 for them to try. Their response was "bolt letting go of spent case too early . . . .replaced bolt; fired 10 rnds of customer's ammo and 50." got it back. Took it to the range with Mr Rabbit and the rest is history. Same issues.

anyone looking for a club???

i hope you had the lower off during this time...I have a 308 Dpms didnt have any issues with the stock mags...or the pmags...id examine the bolt and receiver...also i think stated in different posts...the gas rings, gas tube etc...

 

[CWood]

I have a DPMS in 7.62 and the only problem I have had was with some Brazilian NATO the jammed every time. The cases were almost impossible to get out and the extractor was braking the side of the case off. With German NATO, no problems at all. I use Pmags and wouldn't trade the DPMS for anything. Only other thing I did with it is a Geisillie trigger. Incredible! I do know a little about how ARs work and DPMS has had a few problem but this Riffle works.