DPMS LR308 24" Precision Rifle

[Paradox]

update- Thanks for all the suggestions, i ended hitting the rail points on the bolt with a little emory cloth, soaked the disassembled bolt in a pan of oil overnight, drained it a day and ran a hundred rounds through it without issue. Never had an issue with any AR15 including those i built from scratch, so I guess the 308s are just temperamental.

 

[bfoosh006]

As a starting point...

Do the "mag fed, one round... looking for BCG lock back" test.

After firing the single mag fed round.. and If it locks back on the empty mag... it appears to have enough gas to function.

Then we'll chase other possible issues.

FWIW... there is a good chance it needs a proper cleaning and relube be sure to clean the chamber of any storage oils.... and more break in time.

 

[Captrjc]

It cycled 10 rounds of factory ammo? Did you try that same ammo after you had issues with the hand loads?
What powder and charge did you load?
Check to make sure that your gas tube didn’t get moved or smashed in the receiver by the bolt carrier? Check gas key for loose or stripped bolts.

 

[davsco]

Do the "mag fed, one round... looking for BCG lock back" test.

After firing the single mag fed round.. and If it locks back on the empty mag... it appears to have enough gas to function.

Then we'll chase other possible issues.

FWIW... there is a good chance it needs a proper cleaning and relube be sure to clean the chamber of any storage oils.... and more break in time.

yeah if it's real hard to manually rack the slide with no ammo in it, i'd be sure to strip it down completely and use some lighter oil. with the lower removed, any issues with the bolt carrier and charging handle not sliding in and out easily?

with a mag in, can you manually rack rounds in and out using the charging handle?

 

[davsco]

Check to make sure that your gas tube didn’t get moved or smashed in the receiver by the bolt carrier? Check gas key for loose or stripped bolts.

think he was saying he reloaded a mag, not necessarily changed to reloads.

in any event, yeah if the first ten rounds fired fine, perhaps something did, strip, come loose, get boogered up. again i'd manually cycle some rounds in and out before chasing gas issues.

 

[Paradox]

As a starting point...

Do the "mag fed, one round... looking for BCG lock back" test.

After firing the single mag fed round.. and If it locks back on the empty mag... it appears to have enough gas to function.

Then we'll chase other possible issues.

FWIW... there is a good chance it needs a proper cleaning and relube be sure to clean the chamber of any storage oils.... and more break in time.

Hi, and thanks, forgot to mention i tried that, all three mags, and same result, ejects between 3-4 o'clock, but doesn't lock back, Also I disassembled 3 times, cleaned, reoiled to no avail, after 3rd time i did manage 2 instances in 40 rounds where i managed two rounds before reverting back to original issue.

 

[Paradox]

It cycled 10 rounds of factory ammo? Did you try that same ammo after you had issues with the hand loads?
What powder and charge did you load?
Check to make sure that your gas tube didn’t get moved or smashed in the receiver by the bolt carrier? Check gas key for loose or stripped bolts.

Hi, and yes, tried the original factory rounds that worked initially but same feed issue, also checked gas tube, appears ok, and gas block seems ok as well.

 

[Paradox]

yeah if it's real hard to manually rack the slide with no ammo in it, i'd be sure to strip it down completely and use some lighter oil. with the lower removed, any issues with the bolt carrier and charging handle not sliding in and out easily?

with a mag in, can you manually rack rounds in and out using the charging handle?

Yes, charging is no issue, and ejected rounds are free of any marks or damage as well. I have 8 AR15s and 2 LR308s and all of them cycle smooth as glass, this one however is stiff, even when heavily oiled it feel like its dragging. I've read other posts about this same rifle, one of the excuses was that DPMS claimed sub MOA performance which they did, however even if it was built a bit tight i can't imagine it wouldn't cycle, another rumor was that the buffer/spring combo was too heavy, and one individual did have success installing a carbine stock with adjustable weight buffer. I'd like to think i can make it work without workarounds though.

 

[hafejd30]

Yes, charging is no issue, and ejected rounds are free of any marks or damage as well. I have 8 AR15s and 2 LR308s and all of them cycle smooth as glass, this one however is stiff, even when heavily oiled it feel like its dragging. I've read other posts about this same rifle, one of the excuses was that DPMS claimed sub MOA performance which they did, however even if it was built a bit tight i can't imagine it wouldn't cycle, another rumor was that the buffer/spring combo was too heavy, and one individual did have success installing a carbine stock with adjustable weight buffer. I'd like to think i can make it work without workarounds though.

Is the dragging caused by the bolt/receiver in the action or the buffer/spring in the stock? As in does the bolt move freely without spring pressure on it? Like when you remove the BCG to clean it

If it moves freely you likely will need to play with buffer and spring

 

[Ravenworks]

Put an empty mag into the weapon, pull the changing handle back as fsr as you can.
Now take a look, does the bolt have clearance between itself and the bolt release?

 

[LRRPF52]

This was the 2nd type of .308 AR I purchased many years ago after my first ArmaLite AR-10T.

That’s the original DPMS LR-308 configuration. I remember when it catalogued, because we got one through the FFL in 2004 for a customer/friend of mine.

I got mine in 2007, and its extractor bent within the first few rounds. The chamber was also really tight and needed polishing, but you don’t want to polish excessively because that doesn’t help with obturation, and increases bolt thrust due to reduction in coefficient of friction of the case against the chamber walls.

I would have a competent smith (good luck with that) take a look at it with some chamber gauges.

Another problem with them was that they used a cheap aluminum gas block, which will run ok on a loose schedule for a while, then expand too much with thermal loading and lead to gas leakage.

If I had such a rifle again, I would basically replace the gas block with a steel one custom-fit to the journal. The barrel is so heavy on those rifles too. Mine got reprofiled and the chamber reamed and polished. I called DPMS CS and got a new extractor.

It was an entirely different experience than the ArmaLite.

DPMS is no longer a company, so you’re kinda on your own sourcing replacement parts, though much of the market is common with that bolt and barrel extension combo.

Mine was definitely not sub-MOA. The ArmaLite was an honest sub-MOA rifle. The guy I sold it to came back with a huge grin and a paper target in hand. “Thas thang is uh shooter! Look at this!"

He had a ragged 10-round group that would pass as about an inch.

“Yeah, it shot really well for me too."

Him: “This was at three hundred yards!"

I shot 3-Gun with him on occasion and he worked in the North Carolina Attorney General’s office, so he was a long-time shooter, nut bubba.

 

[Evintos]

Some general diagnostic steps for you assuming everything is cleaned and lubricated properly.

1. remove upper, remove bolt from bolt carrier, remove charging handle, insert carrier sans bolt into receiver and check that it moves freely back and forth with gravity. Reinstall upper onto lower, remove buffer and spring, reinstall charging handle with the bolt carrier sans bolt. With gravity, bolt carrier should freely move backwards and forwards into and out of the receiver extension. Inspect gas key to ensure it's secured.

2. With bolt removed, insert bolt into the barrel extension and rotate, it should rotate 360 degrees freely without binding. Inspect barrel extension for burs.

3. Parts inspections - Inspect cam pin for burs. Inspect upper receiver cam pin recess for burs. Inspect bolt gas rings for damage. Inspect firing pin - should move freely in firing pin channel (making sure it isn't bent). Inspect bolt inside bolt carrier without the cam pin or firing pin, pull and push the bolt in and out to see if it can move freely. Inspect bolt lugs for burs. Inspect bolt ejector and extractor pins to ensure they do not protrude. Inspect buffer detent for damage. Inspect buffer for damage and ensure that the roll pin that retains the buffer bumper is flush or below flush.

Try to find out where it's dragging.

 

[Paradox]

Is the dragging caused by the bolt/receiver in the action or the buffer/spring in the stock? As in does the bolt move freely without spring pressure on it? Like when you remove the BCG to clean it

If it moves freely you likely will need to play with buffer and spring

I took it apart again and oiled the heck out of it, and it moves ok in the upper, the bolt is however very stiff in the carrier. i'm starting to think maybe the buffer., as it does feel stiff hand cyclling. i'm going to swap out the rifle tube for a carbine i have and see if that does anything.

 

[Paradox]

This was the 2nd type of .308 AR I purchased many years ago after my first ArmaLite AR-10T.

That’s the original DPMS LR-308 configuration. I remember when it catalogued, because we got one through the FFL in 2004 for a customer/friend of mine.

I got mine in 2007, and its extractor bent within the first few rounds. The chamber was also really tight and needed polishing, but you don’t want to polish excessively because that doesn’t help with obturation, and increases bolt thrust due to reduction in coefficient of friction of the case against the chamber walls.

I would have a competent smith (good luck with that) take a look at it with some chamber gauges.

Another problem with them was that they used a cheap aluminum gas block, which will run ok on a loose schedule for a while, then expand too much with thermal loading and lead to gas leakage.

If I had such a rifle again, I would basically replace the gas block with a steel one custom-fit to the journal. The barrel is so heavy on those rifles too. Mine got reprofiled and the chamber reamed and polished. I called DPMS CS and got a new extractor.

It was an entirely different experience than the ArmaLite.

DPMS is no longer a company, so you’re kinda on your own sourcing replacement parts, though much of the market is common with that bolt and barrel extension combo.

Mine was definitely not sub-MOA. The ArmaLite was an honest sub-MOA rifle. The guy I sold it to came back with a huge grin and a paper target in hand. “Thas thang is uh shooter! Look at this!"

He had a ragged 10-round group that would pass as about an inch.

“Yeah, it shot really well for me too."

Him: “This was at three hundred yards!"

I shot 3-Gun with him on occasion and he worked in the North Carolina Attorney General’s office, so he was a long-time shooter, nut bubba.

I had an AR amorer inspect it, and he found no issues parts wise, and also commented on it being new and needing to break-in with 500 rounds or so, which is fine and dandy but i'll give it away if i have to hand cycle that many rounds, it already has over 100 through it. what about swapping out the gas block for an adjustable and bumping up the pressure?

 

[Paradox]

Some general diagnostic steps for you assuming everything is cleaned and lubricated properly.

1. remove upper, remove bolt from bolt carrier, remove charging handle, insert carrier sans bolt into receiver and check that it moves freely back and forth with gravity. Reinstall upper onto lower, remove buffer and spring, reinstall charging handle with the bolt carrier sans bolt. With gravity, bolt carrier should freely move backwards and forwards into and out of the receiver extension. Inspect gas key to ensure it's secured.

2. With bolt removed, insert bolt into the barrel extension and rotate, it should rotate 360 degrees freely without binding. Inspect barrel extension for burs.

3. Parts inspections - Inspect cam pin for burs. Inspect upper receiver cam pin recess for burs. Inspect bolt gas rings for damage. Inspect firing pin - should move freely in firing pin channel (making sure it isn't bent). Inspect bolt inside bolt carrier without the cam pin or firing pin, pull and push the bolt in and out to see if it can move freely. Inspect bolt lugs for burs. Inspect bolt ejector and extractor pins to ensure they do not protrude. Inspect buffer detent for damage. Inspect buffer for damage and ensure that the roll pin that retains the buffer bumper is flush or below flush.

Try to find out where it's dragging.

I'll try that and let you know, thanks

 

[TonyTheTiger]

what about swapping out the gas block for an adjustable and bumping up the pressure?

 

[LRRPF52]

I took it apart again and oiled the heck out of it, and it moves ok in the upper, the bolt is however very stiff in the carrier. i'm starting to think maybe the buffer., as it does feel stiff hand cyclling. i'm going to swap out the rifle tube for a carbine i have and see if that does anything.

If it’s grinding in the carrier, the carrier bore might have tool marks in there.

Check that and then polish if necessary, without opening the Inner Diameter, but just smoothing out the carrier bore.

That’s a common problem, especially in that timeframe.

 

[Paradox]

View attachment 7833503

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