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Dpms .308 frequently jams

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2 hours ago, Radioactive said:

Welcome from Alabama

We need a little more to go on...


when did it start

what else have you changed

is it lubed - really lubed

what do you mean by jam- double feed, fail to eject,  fail to feed

does bolt lock back on last round 

give us as many details as possible

Agreed need more info


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It is a live freee armory receiver set with a 18” bsf barrel  ,mid length gas system ‘with a aero m5 carbine buffer tube kit. Before I put the adjustable block on every two or 3 rounds a stove pipe jam wouls happen I figured it was a over gas but even wen I fined tuned it still had same issues and the bolt wouldn’t always lock Back after tunneling it  I don’t have any pictures of jam but here’s the rifle. Also my bcg is a toolcraft . Every thing seems to be working as it should except for the ejecting process 


Edited by Outdoorsman71914
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What made you suspect over gas condition?

how wet with lube are you running it?

any idea what size gas port you have?

how hard is it to manually charge a round or manually lock the bolt back?

im not as knowledgeable on this platform as most of the guys here but my first thoughts are lube and or recoil system

parts compatibility can be a real issue with the large framed platform due to no real standard design

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Ty for replying wat made me thing it was over gas was I felt like the gun gun was kicking pretty hard so I was thinking it was cycling to fast to eject but now IM lost lol ..... always keep it Wet considering it’s new but the only thing I can think of to switch out Mayb the ejected or buffer mayb I did my research before I built and made sure everything was dpms the gas port is .875 od

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You're not overgassed.  You're under-recoiled.  What's the gas port diameter in that barrel?  What's the gas block journal size?  Got a pic of how far the gas tube extends into the upper receiver?

You could have multiple things going on here - buy you are under-recoiled.  Not over-gassed. That's why it's kicking hard.

Oh, and it's not a DPMS .308.  It's based on the pattern - but thats why I backed up edgecrusher, asking if it was a factory DPMS rifle - which it is not.

Edited by 98Z5V
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Your gas tube is good to go.  Cross that off the list.  Recoil system needs fixed, and there are a couple ways to do that.  You'll need a gas port diameter of 0.085"~0.090" for that rifle to run correctly.  Next step is finding out what the gas port diameter really is. 

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3 minutes ago, Outdoorsman71914 said:

On rrhe bsf website it’s says barrels .875 of I’m assuming that’s not the gas port size now now that I think of it right that’s just the measure around barrel near gas port how do I go about finding that information also any suggestions for recoil?

That 0.875" is the diameter of the gas block journal, and the size of the gas block that you'd need to buy, if you were buying another.  Gas block sizes (standard sizes) are 0.625", 0.750" 0.875", and 0.936".  Yours is 875.  Gas block journal size has a direct effect on gas port diameter size - two barrels made identical, say 18" midlength gas barrels, one with a 0.750" gas block journal, and one with the 0.875" gas block journal - the same-sized gas port is not going to work perfectly on both those barrels. It's a pressure that needs to be maintained for cyclic function.  You change that pressure when you change the cylindrical volume of a gas port:  make it smaller or larger - gas port size - or, make it deeper or more shallow - gas block journal size.

For recoil - you need to balance the system, and if it's kicking you hard, it's not balanced.  The first indication is that 3.8oz buffer weight, and that spring. The easiest, cheapest thing to do is buy the Armalite (real Armalite, not copies) AR-10 Carbine Receiver Extension kit.  That will SOLVE the recoil system.  The next thing you need to do is determine the diameter of your gas port.  Then drill it up, if it needs it. Buy a cheap digital vernier caliper from Harbor Freight, use numbered drill bits, there are numerous ways to determine gas port size.

This is the recoil system that you need to be running on a .308AR:


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2 minutes ago, Outdoorsman71914 said:

Thank you I appreciate I’m going to order that product and find out the exact gas port size if it’s where u say it should be as in size could it be any thing else or would u say that pretty much it 

That would be the last thing remaining - gas port diameter. 

Your gas tube is the proper length. 

Your recoil system is too weak to handle .308 Winchester recoil, the mass of a .308-sized BCG.  There's a way to make your 7.000" internal depth receiver extension work, with a heavier buffer from an aftermarket company, combined with a spring from another aftermarket company - but those two things are going to cost you more money than just buying that Armalite kit, and paying shipping one time. The Armalite system is fool-proof - as well as idiot-proof.  It's made in one place, one company, with the same materials every time, to the same tolerances and specs, and it just works.  

If you want the details of the other system - the buffer and spring - it's the KAK .308 heavy buffer that weighs 5.3oz, combined with the Sprinco Orange spring.  That combo makes 7" receiver extensions (AR15 Carbine receiver extensions) work, when used on .308ARs.

All that's left is gas port diameter. 

35 minutes ago, 98Z5V said:

You'll need a gas port diameter of 0.085"~0.090" for that rifle to run correctly.


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