LR308 not stopping on bolt catch, beating up brass

[Revelation]

I realize similar threads have been created, I've read through 3+ dozen to no avail. Any help much appreciated.  

DPMS LR308: 

Aero M5E1 enhanced upper

Aero M5 lower

Faxon .308 18" 1/10 barrel .750 rifle length 

Faxon .308 BCG

Aero melonite gas tube rifle length

JP .750 adjustable gas block 

VG6 muzzle brake

PMAG's

Using a normal Aero 7" carbine adjustable buffer tube paired with Kynshot 2.5" Hydraulic .308 buffer and JP tuned and polished .308 CARBINE LENGTH buffer spring 

AMMO:

Federal Gold SMK 175 grain (Factory) 

SO:

Yes, I can manually pull the charging handle and the bolt will come back and it clears the bolt catch by about 1/4" inch just fine.

Manually, it easily catches back and functions fine in every way that I can tell. 

The JP gas block can go to about 7 turns out which is maxed, they suggest starting at 2 turns out and going a half turn with each shot to adjust. 

I have tried every setting from 1 turn out which will not push the bolt back at all (single shot), to 7 turns out which acts way over-gassed brass-wise (tears up brass, shells come out hotter than a cat on fire, excessive primer cratering possibly?) and the bolt gets halfway stuck on the mag. I couldn't tell if it was still not going far enough back or if it was going too far back too fast and catching halfway and sticking on the empty mag. Either way, the bolt head never caught on the actual bolt catch properly when testing the single round lock-back; I am stumped.

MY NEXT STEPS:

I have returned the Faxon BCG and JP gas block just incase, I am going with an Aero Nickel Boron BCG, SLR sentry 7 adjustable gas block and I will have the head-spacing checked this time before I install the new parts. (I had not before, didn't know it was a thing) I also ordered a regular .308 carbine buffer spring and new gas tube as extra options just incase. 

Pictured is the .308 buffer and spring I am running on the right side vs just my normal AR-15 buffer and spring on the left. 

Sorry if this is too much info or not enough at the same time. I have built many AR-15's successfully, the .308 world is new to me. 

Thank you.

 

[edgecrusher]

One hundred percent the hyd buffer did not slow the cyclic rate down enough and between that and the spring may not have been correct in size. Also, brass isn’t terrible in the pic but I’m curious (knowing you already returned it, doesn’t matter much now) what the firing pin liked like. 
 

Also, how well lubed is your weapon. These large frame rifles need to be well lubed, dripping just about, for break in period. No mil spec and a lot of surfaces that need to mate properly. Possible cause of your issue with bolt but maybe only part of the problem. On your next outing with all new parts, please give us the following info prior to shooting:

 

 

new buffer length and weight

spring length and coil count

picture of the gas tube in cam cut out in a well lit vertical picture 

picture of your lube job and round count prior to and post shoot

 

 

welcome aboard and have no fear, we will solve this

[Revelation]

edgecrusher: I want to clarify.. you think the hyd buffer and spring ARENT enough to slow it down? When I pull the charging handle with this setup, it is STIFF. Probably 3x stiffer than my average AR-15. I thought it would be too much, not too little. I would love to keep this buffer, but you may think I need something heavier. Easy fix maybe heavier Sprinco brand or similar spring instead of replacing the pricey buffer itself?

Also, not questioning your knowledge dont take me wrong, but this same Kynshot buffer and JP spring are the ones recommended to mate together for a regular carbine adjustable stock like im running. Could it be this far off still? Just provoking thought, don't think I'm questioning you on everything. I could use some more lube most definitely. I will do all those things listed this next time around, might be a couple weeks the way things are shipping currently.

I appreciate the help!

Edited August 28, 2020 by Revelation

[Albroswift]

Take a look at this thread. Fill in as many of the blanks as possible .

 

[Revelation]

13 minutes ago, Albroswift said:

Take a look at this thread. Fill in as many of the blanks as possible .

 

Thank you, will do!

[edgecrusher]

3 hours ago, Revelation said:

edgecrusher: I want to clarify.. you think the hyd buffer and spring ARENT enough to slow it down? When I pull the charging handle with this setup, it is STIFF. Probably 3x stiffer than my average AR-15. I thought it would be too much, not too little. I would love to keep this buffer, but you may think I need something heavier. Easy fix maybe heavier Sprinco brand or similar spring instead of replacing the pricey buffer itself?

Also, not questioning your knowledge dont take me wrong, but this same Kynshot buffer and JP spring are the ones recommended to mate together for a regular carbine adjustable stock like im running. Could it be this far off still? Just provoking thought, don't think I'm questioning you on everything. I could use some more lube most definitely. I will do all those things listed this next time around, might be a couple weeks the way things are shipping currently.

I appreciate the help!

You’re ok, I don’t have any feelings to hurt. What is the hyd buffer weight simulate? A .308AR needs at least 5.6oz buffer, most likey more. If you are going springco get the orange spring. Another tried and true is the Armalite recoil system. It’s complete and will work 100% of the time. I know nothing about the buffer you have, the only one we ever hear about is typically the JP Silent capture System. That one seems to be hit or miss and better designed for .556 applications. 
 

Just question but who recommended that set up to you? 
 

Edit: just looked it up, it is 3.6 oz buffer weight. Your not getting enough mass in the ass bud. Your bcg is moving way to fast. You need a heavier buffer or turn your gas way down. Until your rifle is completely broken in I suggest a traditional set up, but don’t take my word for it.......

[Matt.Cross]

Remove the hydraulic buffer from the equation and get a buffer or buffer + spring combo from @Slash and be done with your issues.

Pawn the hydraulic buffer off on the next poor soul who can't be persuaded against their better sense that they're junk.

[98Z5V]

Hydraulic buffers have hydraulics in them, which means they have seals, to seal in the hydraulics.  And seals fail over time, and when they do, your gun fails. You have a catastrophic gun failure (it won't cycle after that buffer fails), and your gun won't function at all after that buffer fails.  Hydraulic buffers are a stupid reason to build a gun, or build a recoil system - but it's smart from the manufacturer side of the house - when your shiit fails, in your gaming competition that you just took last place in, you have to go back to them, and get another...  They just built in their own "if you want reliable, you NEED US!"   standpoint.  Bullshiit.  This isn't about games, and high scores during a competition.  This is about a reliable rifle.  Period. 

Build whatever you want, but if you're not a Gamer, then don't build a Play Rifle - build a real rifle, that will work all the time, with whatever ammo you feed it. Hey, once you do that - go build your Gamer Gun to run competitions with, adjustable gas blocks, reduced-weight carriers, all that - and win money on the Gamer Circuit - you might get sponsors to cover parts.  Around here, we give not one shiit about a Gamer Gun, High-Points Scores in Whatever Circuit that you're currently Gamer-winning...  Just Ain't Care...  Please reference 2:09 in this video...  This is what you'll see...

I've never seen a mechanical buffer fail. Ever.  Have tried to kill several, have I failed at killing them.  Even militarily, through a very, very high round-count for an individual weapon.  There's a simple rule behind this - You Don't Complicate Shiit With Complicated Shiit...

If you DO complicate shiit with complicated shiit (like hydraulic buffers), then you better know what the min and max is on the life of those things.  And, expect complicated failures,that not many people can diagnose. We can diagnose them here - and do regularly, and laugh when they happen - and when it happens, you need to know - You did this to your self...  

There's no lifespan on a mechanical buffer - it'll last until you break the buffer bumper on the end of it.  Because it's not complicated...  Still never been able to break one, and I've tried.

[98Z5V]

Get the garbage out of your gun - and I don't care who told you it wasthe "gold ticket" - get the junk parts out of your gun, build a gun with real, no-shiit reliable parts.....

Then come in here and tell us what your failures are.  We can identify bullshiit parts and junk parts real quick - and it usually hurts "feelings."  Building a running gun doesn't have a single thing to do with "feelings", though.  We don't care about your "feelings."  You want a running gun?  Don't get butt-hurt when we tell you that you have bulshiit parts in there, that don't work, and were sold to you on a whim, hypothesis, unproven theory, whatever... 

Just man up and fix your gun, so you have a running gun. That's the only thing we care about here... 

[98Z5V]

Bird's Eye View:

[Revelation]

I'm not sure where any of you got that I'm butt hurt from? Maybe you were talking to the general audience though. Just my attempt at being respectful to edgecrusher. I appreciate the help very much actually and I only enjoy singling out junk parts if they are junk. 

 

Anyways, that really helps so I will take a gander at a more original setup to start with and also take a look at Slash.

 

Will report back later.

Edited August 29, 2020 by Revelation

[Albroswift]

2 minutes ago, Revelation said:

Will report back later.

We are here to help, and have a hell of a lot of fun doing it!

[edgecrusher]

Rev, no worries. Like I said in my last post, that buffer isn’t heavy enough. Let’s get the recoil system right and the rifle well lubed then start again

[98Z5V]

15 hours ago, Revelation said:

I'm not sure where any of you got that I'm butt hurt from? Maybe you were talking to the general audience though.

Mainly speaking to the Gen Pop out here in the Prison Yard - and trying to head off the filing of the Hurt Feelings Report to the Administrators, if it was gonna head that way.

No worries, and glad you took it like you took it - which is the way it was intended.  It wasn't intended to go after you, in a personal way. 

We'll get your gun sorted out.  Have no fear. 

[jtallen83]

This set-up is the gold standard recoil system for the large frames, get one when you can as it has already went up $20 since I bought my last kit.

https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories&Category=4eeff98b-d9a6-40fd-be6b-ab2e44ec1080

 

[Revelation]

While we are waiting on parts.... WHICH bolt catch?

They are both advertised as .308 catches. One came with my Tom's Tactical AR-10/LR-308 lower parts kit (the beefy one) and the other is a V Seven Weapons S7 LR308 catch. 

Any difference to be had here except for possible shear resistance? 

It does look like the S7 catch sticks up a tad bit further when the mag is in. 

Thanks boys! Excited to start sending freedom bits downrange. 

[98Z5V]

That one on the left in your pics is gonna work better - whichever one that is.  The "spike" that grabs the follower in the mag, and actually makes the mag catch work - is further away from the paddle handle, and the pivot point. 

You took some pics of how high the stick up - post some pics of each one of those, please identify which is which, and show where the spike portion that engages the follower is, actually on the follower.  That one on the left in the pics above - it's gonna be more in the center of the follower, and the one on the right is gonna be more to the left side of the follower, if the pics are taken straight down on them.

[Revelation]

I have tested both manually, they both sit in exactly the same spot on the follower whether they are engaged or depressed. No difference there. The S7 sticks up slightly further which you can sort of see in the two pictures, but its overall mass is less. When I receive the rest of my parts and initiate testing and take additional pictures, I will try both again. 

 

Thanks again!

[edgecrusher]

Great! A write up may help others. If you wouldn’t mind post it in the part section so it’s easier to find?

[jtallen83]

It would be great if you could add to this thread;

 

[Merle]

When I put together my Aero M5 I just used an Aero M5 lower parts kit. I had zero issues with the bolt not locking back with their bolt catch. I did stray from their DPMS 308 buffer tube, spring, and buffer set up though. I went with an Armalite AR10 kit. Again, zero issues. 

Edited September 5, 2020 by Merle

[Merle]

Take 98Z5V's advise and ditch that gimmicky buffer setup. Get this and never look back: https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories/Lower-Receiver-Parts&Category=ac614400-ff09-4cdf-9d35-419a654e7201

[mrmackc]

Anyone ever used one of these night vision things on your riflescope?

[98Z5V]

[Revelation]

Update:

Received the new parts. Went with the Slash CAR-10 buffer system as well. Will post more on the new parts with plenty of pictures later. We have a problem though.

Had headspacing checked by a reputable shop, it was a no-go. They currently have the upper and are going to space it correctly. 

Will update as soon as possible so this thread isn't open-ended!