Have to use forward assist

Posted by: Powerfisher

Have to use forward assist - 01/25/22 01:25 PM

Hey everyone. So I am having problems with my AR-10. It is a .308 and it is a DPMS LR 308 platform. It has a low profile non adjustable gas block. So, I have to use forward assist after every round or I get a light primer strike and it won't fire. When I chamber the first round by pulling the bolt back, it shoots fine but if the action is open after the last shot and I close the bolt by pushing the bolt release lever, it will not shoot unless I use forward assist. I have tried a stronger buffer spring but then it would be too stiff and it wouldn't grab a new round from the magazine. I cleaned my BCG thoroughly and have lube in all the right places. My next step is to replace the gas rings. Any other ideas?
Posted by: SlickerThanSnot

Re: Have to use forward assist - 01/25/22 02:37 PM

sounds like the brass is not sized enough. are these your hand loads or factory loads?
Posted by: Powerfisher

Re: Have to use forward assist - 01/25/22 03:05 PM

I have used all factory ammo. Mostly military.
Posted by: GC

Re: Have to use forward assist - 01/25/22 03:49 PM

Clean your chamber - thoroughly.
Posted by: Tonester

Re: Have to use forward assist - 01/25/22 03:50 PM

Agree with GC. Start by using a chamber brush and clean thoroughly.

TC
Posted by: Tonester

Re: Have to use forward assist - 01/25/22 03:51 PM

You could also test the military ammo with a case gauge (never hurts if you got one).

TC
Posted by: Bowhntr6pt

Re: Have to use forward assist - 01/25/22 03:55 PM

Who made the barrel?
Posted by: spotstalkshoot

Re: Have to use forward assist - 01/25/22 06:54 PM

Also make sure the gas tube and bcg are aligned properly and barrel nut gas tube are not touching. It would probably run without gas rings.
Posted by: crapshoot

Re: Have to use forward assist - 01/25/22 07:01 PM

Might also check the barrel extension for burrs.
Posted by: AdamT

Re: Have to use forward assist - 01/25/22 07:37 PM

I would do a very thorough cleaning. If it only happened after firing a round, I would suggest checking your gas and recoil system as well. It should go into battery when using the bolt release. Clean it good, check the dimensions on the loaded ammo since it sounds like it may be mil surplus, also try a different magazine.
Posted by: Powerfisher

Re: Have to use forward assist - 01/25/22 09:18 PM

Thank you all for your replies. I have cleaned it thoroughly but I did not use a chamber brush. I will invest in one asap. The barrel is stamped, DPMS 7.62X51 with a 1-10 twist. I have tried different magazines with no success. I will mic my ammo and make sure that it's within tolerance. My buffer weight is not adjustable and I was thinking that I may need a new one so that I can adjust the weight. Thanks again for the advise and I will report back with, hopefully, positive progress.
Posted by: SubpaR

Re: Have to use forward assist - 01/26/22 12:45 AM

Was it bought new or used. If bought new, it probabaly wouldn't hurt to manually cycle the BCG a few hundred times to speed up the break in period. Just adding some spitballs...
Posted by: Powerfisher

Re: Have to use forward assist - 01/26/22 09:56 AM

It was used but with a very low round count.
Posted by: Coyote-conquest

Re: Have to use forward assist - 01/26/22 01:19 PM

It may just need broke in really well. I had a 223 AR that took quite a few rounds to break in before it would seat a round every time. That and clean it really good.
Posted by: Plant.One

Re: Have to use forward assist - 01/26/22 05:32 PM

have you tried more than one magazine?

you could easily be dragging on the feed lips or something similar. DPMS LR series rifles are known to be especially fond of magpul LR/SR series 308 mags. and we all know how fussy some metal mags can be. one wrong feed lip angle, or a little burr... and you got trouble.




as others have mentioned i would suggest hand cycling it to break it in after giving it a really thorough cleaning of the bcg, barrel, chamber, and barrel extension.

start by delubing the [beeep] out of it. take the BCG out and spray it with brake clean or gun scrubber. same goes for the upper itself. if you have an ultrasonic cleaner, disassemble the bcg and drop it in there first for 8-10 mins. then brake clean & scrub to get all the carbon out. when you reassemble you want that thing DRY DRY DRY. like painfully dry. you should cringe putting any rifle back together this dry type of dry.


then hand cycle it without any ammo several hundred times. pull the bolt and let it fly. wash, rinse, repeat. this dry lapping process will allow mating surfaces to smooth out on each other and run any burrs off that might be holding things up.

HTH and keep us in the loop on how things work out!
Posted by: Plant.One

Re: Have to use forward assist - 01/26/22 05:37 PM

you also mention that an extra power spring is causing it to not pick up rounds... thats kind of suspicious in itself. DPMS usually way over gasses those rifles, and you can usually run a LOT of buffer weight back there before they will fail to cycle. or do so in combination with an XP spring.

i would do a single round bolt hold open test, make sure that its catching the mag at the right point, etc. if its not doing that properly you may have a gas block alignment issue too as well as something rubbing wrong.



do give us a little more info on the rifle itself too - barrel length, gas system length, what type of stock (adjustable carbine, or fixed a1/a2), what weight buffer you currently have in there, etc etc.
Posted by: Powerfisher

Re: Have to use forward assist - 01/27/22 11:10 AM

Thanks again for the replies. I have two magpul magazines and the issue happens with both of them. I also tried a metal magazine that I borrowed from a friend and it did not solve the problem. I am going to spend the weekend crawling through it, looking for burs and any other thing that may cause the problem and am going to clean it again using a chamber brush. I used gun scrubber and I will do it again and I will use break clean as well. I did the one shot test and the bolt does stay open but when I push the bolt release lever, it doesn't close all the way and I have to use forward assist. If the bolt is closed and I pull it back to chamber the first round, it shoots fine, but the next round needs forward assist. I do know that the buffer weight is not adjustable and that's why I am going to buy an adjustable one as well as new gas rings. I will assemble it dry, dry, dry and cycle the bolt manually a couple hundred times. I will also get as much information as I can about the upper and will let you know what I have. Thanks again!
Posted by: SlickerThanSnot

Re: Have to use forward assist - 01/27/22 11:42 AM

have you tried any ammo that is not mil surplus?
Posted by: Plant.One

Re: Have to use forward assist - 01/28/22 01:56 PM

Originally Posted By: Powerfisher
Thanks again for the replies. I have two magpul magazines and the issue happens with both of them. I also tried a metal magazine that I borrowed from a friend and it did not solve the problem. I am going to spend the weekend crawling through it, looking for burs and any other thing that may cause the problem and am going to clean it again using a chamber brush. I used gun scrubber and I will do it again and I will use break clean as well.



that eliminates the magazine.


Quote:
I did the one shot test and the bolt does stay open but when I push the bolt release lever, it doesn't close all the way and I have to use forward assist. If the bolt is closed and I pull it back to chamber the first round, it shoots fine, but the next round needs forward assist.


so the bolt wont even close all the way with no ammo being loaded?

have you taken the bolt carrier group apart and cleaned it super well? the chamber where the gas rings slide along tend to build up a lot of carbon, and will often need to be scraped out to remove it. solvents usually wont get it all, especailly if its heavily built up. this is why i mentioned using a ultrasonic cleaner if you have one. TBH i think my Ultrasonic tank is one of the best small gun parts cleaning tools i own.

field strip the bcg - take the bolt, cam pin, etc out - and really give it a once over. you might be surprised what comes out from inside of it.


Quote:
I do know that the buffer weight is not adjustable and that's why I am going to buy an adjustable one as well as new gas rings. I will assemble it dry, dry, dry and cycle the bolt manually a couple hundred times. I will also get as much information as I can about the upper and will let you know what I have. Thanks again!


do you have an adjustable "carbine" stock? or a fixed a1/a2? that will help us determine the base weight. you can always take it out and pop it on a scale to find out what you have.


do note, that with the DMPS LR308 system, you CANNOT use a standard ar-15 buffer, the 308 carbine buffer is SHORTER than a standard AR-15 Carbine buffer due to the standard buffer tube length but longer BCG.

i would not waste your $ on an adjustable weight buffer system for it, if you're gonna upgrade at all, go straight for an XH from slash's - once you have your cycling issue sorted out anyway. the system isnt under gassed (trust me, its a dpms 308 ar... lol), and is likely over gassed unless the block isnt aligned properly.
Posted by: Powerfisher

Re: Have to use forward assist - 01/31/22 10:39 AM

Yes. Winchester .308 180 gr.
Posted by: Powerfisher

Re: Have to use forward assist - 01/31/22 10:56 AM

The stock is an adjustable carbine. I have disassembled my BCG and cleaned it thoroughly. I do not have an ultra sonic cleaner. There is still some carbon build up in it and I did not scrape it. That will be my next move. Thank you for that tip. From what iv'e gathered, it's some deep carbon fouling and/or a break in period. The whole rifle is going through a total deep clean and then I will cycle the action, dry, dry, dry manually a couple hundred times to break it in. I will report my next range results.

Thanks everyone!
Posted by: baitpile

Re: Have to use forward assist - 02/01/22 10:11 AM

Make sure to get the inside of the bolt carrier scraped out good, as well as the cone on the rear of the bolt. These have worked very well for me for that task.

https://botach.com/kz-bolt-buddy-carbon-scraper-for-7-62mm-bcgs/
Posted by: Powerfisher

Re: Have to use forward assist - 07/03/22 10:08 AM

Update:
Multiple problems. I cleaned the holy crap out of everything and nothing seemed to work. I put in a new buffer spring, new buffer weight, replaced the gas rings and so on. I had the upper looked at by the local gun shop and they said the head space and everything looked fine. So, I was getting ready to just buy a whole new upper but decided to start with replacing the BCG first and bingo! It started to run! Then, there were a few times when the bolt wouldn't close all the way. It was mostly with the military ball ammo. So now I am reloading with a full length case sizer to see if this cures that problem. It could also be a magazine feeding issue but first things first. At least it's finally running. Thanks again for all the help and advise. Happy Hunting!