Magazine specs

[gravismaximus]

Looking to find out info.  What is the spec for the magazine lips.  Also is there a preference for how high a cartridge sets in the magazine? Thanks

[98Z5V]

hello all, i am having a problem with my bcg not going fully into battery 50% of the time after i chamber the first round.  i would like to know what the spec is for the magazine lips.  i plan on spreading the lips some as well as sanding them some so there not as sharp. i also will be polishing the feed ramps. thanks for the info

Need to know more about what's going on here.  BCG isn't going into battery - BCG is not seating when you try to chamber a round? 

Usually, there are other things going on to cause a malfunction like than, than a magazine issue.  With more details, it'll be alot easier to narrow it down. Need alot more details, though, before you start spreading magazine lips and sanding them.

[ARTrooper]

Maybe start out with your rifle setup and what type of magazines you are using and then tell us what is or isn't happening that needs correcting

[gravismaximus]

Ok here's some info.  Aero m5 upper, lower and bcg. Ballistic advantage gov mid length barrel 18". I have Asc magazines one 10 and one 5 round. Carbine stock with luth-ar 308 buffer spring. A carbine 308 buffer (tungsten powder) can't remember what brand. Spikes Mid length gas tube, seekins adj gas block.

A little more to the story, ok so I go to fire it for the first time this spring withonly 1 round in magazine (going to set gas block), pull the changing handle and had multiple failure to feeds. It was originally a Franklin arms dfm (ASC) magazine which I have removed and gone to normal mags. Installed the 10 round magazine per NY safe act and at first had same problem on and off.  So I hand cycled  with no rounds in magazine 150 times, just letting it slam home.  Now I don't have failure to feeds. So that  helped.  I have set the gas block, locks open after last  shot 100% of time. So my current situation.   Load magazine, pull charging handle let it slam home, goes into battery. Fire first round boom. Next round  click or boom for rest of magazine. What I know is if I  use forward assist it will go boom.  The bolt at random 50% of time does not go into battery, the bcg is a 1/16 inch away from being fully forward. Pull trigger when it's like this you get click (hammer falling) and the bcg/ bolt finish going forward/ into battery. Round will have light primmer strike.

Now I install my 5 round magazine, 90% chance it's not going into battery. This magazine is new, so it seems something in magazine needs to get broken in.

I ruled out gas problem, locks back right.

I did have headspace checked by two different gun Smith's (pass)

Running very wet at times, makes no difference.

I checked to be sure hammer does not hit lock release.

Lightly sanded gas rings so bolt moves easier. Still passes bolt test

Removed 1 oring from extractor

Removed extractor and ejector put BCG back in to upper and hand cycled, goes into battery every time.  Now if I simply let gravity let BCG fall into battery it goes 75% of time and I find the 1/16 problem, and a little push puts it into battery. So possible BCG problem or maybe need a heavy buffer?  I would think I would always get a FTF if the timing of BCG was bad.  Changing the magazine made the biggest difference, so that's why I was going to check the lips just to be sure there in spec.  And I was going to sand the lips due to the scratches there leaving on the brass. I'm sure I've left out other things I've tried,  I took a video of it doing the problem. I'll post the link.  Rifle currently has 180 rounds through it.

https://youtu.be/Rj-sbEY07Wg

Edited October 1, 2018 by gravismaximus
Added video link

[98Z5V]

NOW we have something to work with here. 

Since you're running a carbine receiver extension, you might as well rule out all the weird shiit that you can get form SO many manufacturers, and just run the AR-10 Carbine Recoil System, complete.

A real 7 5/8" internal depth receiver extension that will take a real AR15 H3 3.250" carbine buffer, and the Armalite EA1095 spring.  The real receiver extensions you can get are the Armalite AR-10 Carbine receiver extension, the VLTOR RE-10/A5SR receiver extension, the VLTOR RE-A5, or the new MagPul Enhanced Receiver Extension – SR25/M110. Trust nothing else for being "right," because most of the time, it is not right. 

Pick up one of two buffers:  The real Armalite AR-10 Carbine buffer, or any AR15 H3 Carbine buffer - they're the same, at 3.250" long and 5.4oz.

Only use the Armalite EA1095 spring.

That will solve any possible issues that you might encounter in a carbine recoil system of a .308AR rifle. Period. You won't have recoil system problems, and if you have further problems - it's not your recoil system.

Next - gas tube length.  Take a picture straight down into your upper receiver, of how far the gas tube extends into your upper receiver.  Straight down.  It needs to come to the center of the cam pin cutout. 

Next - just get some P-Mags.  Eliminate the possibilty of the ASCs. MagPul makes them NY-legal, varying capacities, and they're out there.

All the info you provided above would have helped, greatly, on your first post - and you would have had more responses.  Generic input = generic output.

EDIT - While we're on it- remove complicated shiit from the equation, and just wide-open that gas block, until you get a functional rifle.  AFTER you have a functional rifle, then you can mess with that fancy adjustable gas block. 

Edited October 1, 2018 by 98Z5V

[DNP]

 thank you for the details!  Usually it takes 3 pages to get all of that out of someone. That much info also saves us from recommending stuff you've already tried, which actually looks like a pretty good list of attempts. I have no experience with those mags you're using. To help rule them out I would attempt to try a few other brands and see what happens. Got any local buddies with mags you could borrow?

Edited October 1, 2018 by DNP

[survivalshop]

I don't see where your description of Receiver Extension inner depth ( Buffer Tube ) , is it 7" or 7 5/8" ? Also Buffer Spring length & coil count , Buffer length & weight . If BCG is locking back on last round fired in the Mag ., it doesn't sound like a Buffer system issue , but we still need to check it .

It appears that the BCG is hanging up & the dropping of the Hammer on it is completing the Bolt locking into the Barrel extension . You say the Bolt locks properly with out the Extractor & Ejector installed , is that with a loaded round being chambered ? 

I have seen stiff or out of spec Extractors cause the same issue you are having . You say you removed an O-Ring , is there just O-Rings for an extractor spring or is there a double Spring set up like a DPMS LR308 system . Photo's of all this helps .

I see no need to just change components to see if they work , lets see what you have to begin with .

[ARTrooper]

What's makes you think it might be magazine besides the better percentage with the different magazine? is there sign of contact between the mag lips and the bcg?

Sounds to me like it is feeding fine if the bolt grabs a new round each time, it just might be a failure to fully chamber or lock. Of coarse buying a few magpul mags never hurts, can never have to many. and it will completely illuminate that possibility. 

[gravismaximus]

Looks like it is a 7" tube (ar15)with a 2.530" buffer (said for 308). I don't remember the weight of it and for some reason I can't find the receipt for it (I saved them all) but I do remember that it was not a heavier than normal buffer, and the one I have has the tungsten powder inside instead of the balls.

It is a lr308 dpms system as far as I know/think. The extractor had 2 orings and has double springs. Which spring should I take out if I was to, the inner or outter?

As for the buffer spring I count 26 coils.

I do not believe I had a round in the camber while gravity dropping the bcg when it was going into battery,  however it was going into battery after I installed them both as well., But tonight I tried and ist not going into battery, maybe I need more lube on the rings, I haven't lubed it in 2 weeks (haven't used it).

[gravismaximus]

Looks like it is a 7" tube (ar15)with a 2.530" buffer (said for 308). I don't remember the weight of it and for some reason I can't find the receipt for it (I saved them all) but I do remember that it was not a heavier than normal buffer, and the one I have has the tungsten powder inside instead of the balls.

It is a lr308 dpms system as far as I know/think. The extractor had 2 orings and has double springs. Which spring should I take out if I was to, the inner or outter?

As for the buffer spring I count 26 coils.

I do not believe I had a round in the camber while gravity dropping the bcg when it was going into battery,  however it was going into battery after I installed them both as well., But tonight I tried and ist not going into battery, maybe I need more lube on the rings, I haven't lubed it in 2 weeks (haven't used it). Bcg is fully assembled  with no round in camber in this video.

https://youtu.be/ocaPg_kRJyA

[gravismaximus]

Bcg is fully assembled  with no round in camber in this video.

https://youtu.be/ocaPg_kRJyA

it was going in before, maybe I had the charging handle out and had it picked up higher before.

ha, I found it, buffer is a guntech ar10 308 caliber carbine gt-10 so the description says.

bought from optics planet, sku is    2ah-rbf-gt-10

[98Z5V]

That spring looks SHORT, man!  What's the relaxed length on that thing? 

I wouldn't worry about gravity-dropping that BCG,and it going into battery.  Everything is new, and it goes through some serious "meshing of parts" in the first couple hundred rounds.

Buffer length matches the receiver extension internal depth - but that spring is way outta whack. Buffer weight for a .308AR in .308 Win should be 5.4oz, whether it's rifle buffer or carbine buffer - that's how much weight it takes to control these things, when all other parts are working as designed. 

I've combined buffer parts before, and made a shorty buffer (almost 2.500" long) that weighed in at 5.7oz. I'll try to find the info.  You can make a shorty buffer with off the shelf parts that will weigh in at 5.1oz.  By the time you spend the money to do it, then the time to do it, you're better off just getting the Armalite AR-10 Carbine recoil system in your gun. At that point, no more worries.

Thank you for the information - it's helping greatly.

Here's the info on short .308 buffers:

 

[98Z5V]

Here's that GunTec buffer - it comes in at 4.4oz.

https://www.guntecusa.com/ar10-lr-308-car-buffer-and-spring-set

You buy it with that spring?

[98Z5V]

5 minutes ago, gravismaximus said:

Bcg is fully assembled  with no round in camber in this video.

https://youtu.be/ocaPg_kRJyA

it was going in before, maybe I had the charging handle out and had it picked up higher before.

ha, I found it, buffer is a guntech ar10 308 caliber carbine gt-10 so the description says.

bought from optics planet, sku is    2ah-rbf-gt-10

Nope, I was wrong - HERE is your GunTec GT-10 buffer, at 3.8oz.  That's H1 weight.  You need H3 weight in a 308.

https://www.guntecusa.com/ar-308?product_id=1675&sort=rating&order=DESC&limit=100

[gravismaximus]

I had a gut feeling it was going to end up being a buffer, I remember it wasn't a heavy when I bought it.  Now I'll have another useless buffer, (have the ar15 buffer and spring that came with the stock).

I will measure the relaxed length of the buffer spring, what should it be, and was the coil count on?

Please explain/ teach me as why there are two different tube lengths and what buffer length goes with what tube length and what spring length goes with each. I realize there is carbine vs rifle, is that the difference 7 vs 7 5/8? 

Still going to ask this again, what is the spec for magazine lips, I want to check mine.  I am assuming that my 5 round magazine just has to be installed and hand cycled a 100 times to get it to work like my other magazine?

Thanks for help so far

[survivalshop]

These are DPMS Buffer & Spring spec's from a DPMS Carbine 308  with a  7 " AR 15 Receiver Extension . This is from a real DPMS Buffer system & works flawlessly .

Buffer length- 2.5"

Buffer weight - 3.5 oz. ( anything really near that is OK , because I'm not sure how accurate any scale is , this is mine 3.3 oz. )

Buffer Spring length - 11 1/4 - 11 1/2" or some where near that , the one I have measured has got thousands of rounds through it & it measures a touch over 11 1/4" 

Coil count should be around 29 

This will work with a AR 15 Receiver extension ( Buffer Tube  7" ) 

There is DPMS Receiver Extensions & then there is Armalite Receiver Extensions , two different ways of making it happen , if you have a AR 15 Receiver Extension use the 308 DPMS components or those to their spec's & it will work , there are tens of thousands of them out there working just fine , if the correct components are used . Order parts from retailers that have the component spec's or can look them up .Most confuse AR 10 & LR 308 as all AR 10 , they are not !

You spring seems short on Coils , which makes it a little short in length , most likely & will have reduced spring power .

Don't be afraid to use a small amout of good synthetic Grease on the Bolt Lugs & Carrier Cam Pin for break in or general use . Very small amounts of grease , to help the components mate .

Edited October 2, 2018 by survivalshop

[survivalshop]

 There may be , but I have never heard of Mag Feed Lip Spec's , we used to tweak the early DPMS Mags all the time to get them to the correct angle to feed properly (DPMS was the only source at the time ). DPMS would replace them if they had issues , maybe they had a bad run from a supplier , but that was long ago ,seems like . I think there is a tool to Tweak the Feed lips of Metal Mags some where . With Magpul coming out with there LR Mags for SAR25/DPMS , bending or tweeting feed lips went out the window , so to speak .

If you have a Mag that feeds well , try to copy that feed angle with the one not feeding so well .Trial & error type thing , just remember that by changing the feed lip , it could open them up too much & cause other issues . Also look at how far the Mag sits in the Mag well inserted in the Lower & how tight is the Mag Catch , AR 15 Mag Catches can be too short & cause issues with not enough tension on the Catch .

Some times sanding & de-burring them helps , as with cleaning & light lubrication .

[gravismaximus]

Ok so the spring is short, measured 9 5/8. What is that supposed to be used in? I checked my receipt and went online to look at the part number, 308-cs-10a says it's for a 308 carbine, but a closer look on the webpage at cheaper than dirt the luth-ar number changes to a L308-cs-10a down in the specs, sure enough go to the luth-ar page it's a 9.5 spring, .  ugh!!! Why'd it say for a 308 carbine then????  Is that for a pistol set up?

I also see spings in 12 3/4 i assume that's for a2 butt stock setups rifle length? 

I also see 11.5  that says carbine standard rife length, little confused there which is it carbine or rifle?

What one do I need to get 11.5 like survialshop stated with a h3 buffer 98z5v said or just keep my h1.

I can definitely see how a 2" short spring would not have the umph needed to close that bolt into battery, so hopefully with your help we got this figured out. Thanks

[98Z5V]

Here's the real deal on receiver extensions.  There are only 3 types.

1. Rifle receiver extensions.  They're the same across all platforms (we're talking "common ARs" here, not custom Long Action or Lapua Magnum ARs). AR15 rifle buffers are 5.900" long.  308AR rifle buffers are 5.200" long. Both buffers weigh pretty close to 5.4oz. 

2. AR15 Carbine Receiver Extension.  It's either Commercial or Mil-Spec (doesn't matter here, in this discussion), and it has a 7.000" internal depth.  It works with the AR15 Carbine buffers that are 3.250" long - in an AR15.  When you adapt that into a 308AR, your 308AR BCG is longer than an AR15 BCG.  To run that longer BCG back into that receiver extension, you have to use a shorter buffer - you still have to fit all the gear into that depth.  308AR buffers are 2.500" long.  Weights vary, greatly.  Sometimes by design,and sometimes because manufacturers have no idea what they're doing.

3. Armalite AR-10 Carbine Receiver Extension.  This one was developed by Armalite for use on the AR-10, with a collapsible stock.  It uses the AR15 Carbine buffer, in H3 weight, which is 5.4oz.  Notice that weight?  Same as a rifle buffer...  In order to run this weapon, with a longer BCG, and the longer AR15 buffer, they had to make the receiver extension longer (deeper, internally).  The internal depth is 7 5/8".

There is ONE recoil spring for Armalite AR-10 systems, no matter if you're running a rifle recoil system or a carbine recoil system. It's the EA1095 spring.  It works in both recoil systems.   You can run it in ANY rifle recoil system on any 308AR, no matter what brand.  You cannot run it in a 308AR using the shortened AR15 carbine recoil system (7.000" internal and short 2.500" buffers).  You WILL hit coil-bind on that spring, in the short recoil system. 

If you MUST run the short AR15 carbine receiver extension, find a heavy buffer.  You can buy buffers from HeavyBuffers.com.  They're made for this.  Clint @ HeavyBuffers recommends the Wolff XP spring in this setup.  Sprinco also makes a specific spring for this setup - the Sprinco Orange spring. 

If you're running the short RE, you will need one of those two springs, and you will need a heavier buffer than what you probably received. I gave details in that thread I linked on how to make a heavier 2.5" buffer.  Or you can buy from HeavyBuffers.com. 

I quite mixing and matching a long time ago. Shiit springs that nobody knew what they were doing when they made them, buffers that were too light, receiver extension that weren't made to spec (had one that was 7.100" internal depth,and it cause all kinds of operational problems with the weapon).  I stopped all the nonsense, and switched over to genuine Armalite AR-10 Carbine Recoil Systems a long time ago, on all Large Frames with collapsible stocks.  I don't have recoil system issues, ever.

My $0.02 on the matter... 

 

http://heavybuffers.com/reference.html

(click this pic below to make it bigger)

Edited October 3, 2018 by 98Z5V

[98Z5V]

There are THREE other carbine receiver extensions that are positively verified as 7 5/8" internal depth, and can be used in place of the Armalite AR-10 Carbine Receiver Extension, without issue.

VLTOR RE-10/A5SR

VLTOR RE-A5

MagPul Enhanced Receiver Extension - SR25/M110

[98Z5V]

13 minutes ago, 98Z5V said:

If you MUST run the short AR15 carbine receiver extension, find a heavy buffer.  You can buy buffers from HeavyBuffers.com.  They're made for this.  Clint @ HeavyBuffers recommends the Wolff XP spring in this setup.  Sprinco also makes a specific spring for this setup - the Sprinco Orange spring. 

If you're running the short RE, you will need one of those two springs, ...

Here's the reason I say this, specifically.  The Wollf XP spring and the Sprinco Orange spring are manufactured to a specific standard, for a purpose, by companies that make springs.  They both know what they're doing, and they did it on purpose, for a purpose.

All other companies are guessing. Sometimes they get it right, most times they fuk it up tragically.  But, hey, even a blind monkey finds a banana once in awhile, right?  It is not worth your time and money to keep experimenting with springs, hoping that they got it right - and maybe getting lucky. 

Your 9" spring is a perfect example.  That's not enough spring for any AR platform, no matter what caliber  - but it might work in a .22LR conversion, where the "BCG" never moves.

[survivalshop]

You can get a Tubb's flat wire spring for AR 308 & it also works for Carbine or Rifle length systems . Its not the Buffer systems fault , its the ( as 98 posted ) sellers fault , purchase components from those who actually sell DPMS parts & you won't go wrong , as you would if purchasing Armalite components , from someone that sells Armalite parts .

Brownells sells DPMS Parts & if you look at the reviews for the Springs it has answered what length & what they work in.

https://www.brownells.com/rifle-parts/receiver-parts/recoil-parts/recoil-springs/308-ar-buffer-springs-prod42988.aspx

 

Question

7/24/2017

What is the overall length and coil count of this spring?

zmeier from Michigan

Answer This Question

Answer

7/25/2017

 

The spring is 11.5" long. For the coil count, please give us a call. That's not a statistic I have notes on.

 

Customer Care from Brownells

Edited October 3, 2018 by survivalshop

[gravismaximus]

Does coil count mean anything or is length what really matters?   Obviously more coils should mean more length,.  However is there springs with the same length but different coil count (more) as in attempt to make a spring stronger/ more resilient?

[survivalshop]

Length & spring tension are both important & I'm no spring expert by a long shot , but the coil count will mean something because of the coil material diameter. Also I'm sure there is a mathematical equation for length/diameter/spring  material thickness to make proper spring tension . And Spring spec's are set for these AR's , & there individual Buffer systems .

 

[98Z5V]

8 hours ago, gravismaximus said:

Does coil count mean anything or is length what really matters?   Obviously more coils should mean more length,.  However is there springs with the same length but different coil count (more) as in attempt to make a spring stronger/ more resilient?

Coil count is important, as well as wire diameter - together, that's what determines your spring tension, over a given length. 

If you have a spring that's 12" long, and it has 5 coils, it's gonna be a bitch to compress.  If you have a spring that's the same length, and 30 coils - it'll be easier to compress, but not as stiff as that first example.  Coil count matters.

If you have a wire diameter in that 12" spring that's 0.010", that's tiny, like ink pen springs.  You have a wire diameter of 0.072", and that's a proper recoil spring size.  Smaller makes it weaker, larger makes it stronger.

This stuff really does matter - and there are SO MANY companies that don't even have a clue.

That's why I switched everything out to the Armalite parts.  One source, one manufacturer, and it's from a company that really understood what they were doing when it was all developed in the first place.