My 80% build w/ BCA upper and its woes.

[britx303]

So here goes...........hopefully I do this right for yall. So just did my first 308. Ive milled and built 10 or so 556 lowers, and complete upper builds a couple times. Ive both pinned on complete uppers and full assemble some. But mil-spec being what it is.......these were easy peasy,cut and dry by comparison to a 308.......I knew this going into it and i'm fine with the learning curve. So specs on lower: Originally used a 3.8oz buffer that was sold as what to use for a 308. No idea on spring rate, as it was a set with the buffer, so at this point im assuming its wrong since now reading here 3.8oz is WRONG. Ive replaced that buffer with one from KAK @ 2.5" length and 5.1oz on my digital scale. Ordered a springco orange spring last night, so I know whats actually in there for the future, and Ive seen it mentioned here a good bit. The extension is the 7" internal dimension. The upper is a rear charging 16" mid-length heavy barrel from Bear Creek Arsenal. I did last night after a few weeks of lurking this site come across the "gas tubes,barrel gas port" thread, and that led me to check the location of where my gas tube ends inside the upper. It does NOT meet in the middle of the cam recess/cutout, and stops quite short by appx 3/16"(visual) from center. Therefore after some more reading and measuring what I have, it appears BCA used a DPMS mid-length tube @ 11.75", but it should have a Armalite spec'd 308 carbine tube @ 12.0625" and that will bring it up to center. This is going by the charts some of yall posted up here, so if I missed something, correct me please.

[britx303]

My symptoms trying to fire the rifle: FTF, FTE and double feeding. I can fire between 2-4 rounds tops then it fails. Bolt scrapes deep into the sides of the cases or bolt mashes the cartridge side to the point its trash and not worth the risk. I have only been able to source 1-20 round pmag, but did use my brother in laws pmag, and both failed. Ive since ordered an ASC 10 round and a hexmag 10 round to try those once I do the spring and gas tube swap and get back to a range. Those were the only mags I could find last night that would ship to MD, and my local shop only has the pmags. 

[britx303]

Sorry, bouncing back and forth waterboarding myself to give all my info that I can............BCA lists the gas hole diameter at .086 and when I was checking that with my micro drill bits it was pretty near damn spot on as I stepped the bits til the last one that was closest to that dimension, but the first over it,  would not go into the hole. That was a few weeks ago, so to get the exact hole size for yall, I'd have to check again since I stepped away from it til now. So for now i feel safe to say the hole is as sold.......086

[britx303]

And im going to apologize in advance........im not the best author, but im doing my best to be as clear as I can for yall.

[edgecrusher]

Welcome aboard and great job. You’re well on you’re way to getting this fixed. May have to open the gas port up some but your parts that you’re replacing are spot on! 

[shooterrex]

So far so good. The KAK buffer and orange springco spring should fix your recoil system. The gas tube is a bit short and the Armalite carbine 308 gas tube should fix you up.

Your feeding problems are not probably the magazines.

[DustBuster]

I am curious, what gas block are you using?  I ask this because my first build with a rifle gas system and same buffer and equivalent spring worked perfectly.  One jam using a lancer mag but about 500 other perfect cycles with that mag and pmags.  I’ve since changed to a new barrel for accuracy reasons( same exact model of barrel), but I decided to use a different gas block.  A KaK non-adjustable block.  Now I have better accuracy with the new barrel but for the first time ever, I have about 25% failure for bolt to stay open on empty mag.  This tells me I’m getting less Gas than I was before.  My gas port is the same size as the perfect cycling port was.  Gas Problem I have with this different gas block.  

What kind is yours?

By the way, my gas tube even goes farther than the halfway point with both blocks.  That isn’t my issue.

Edited January 25, 2022 by DustBuster

[britx303]

8 hours ago, shooterrex said:

So far so good. The KAK buffer and orange springco spring should fix your recoil system. The gas tube is a bit short and the Armalite carbine 308 gas tube should fix you up.

Your feeding problems are not probably the magazines.

I wasnt sure on the magazines. I thought I had read it can be a finnicky issue with various 308's. Best case here is I end up with a couple more mags for it, and would be great if they all work  :)

[britx303]

6 hours ago, DustBuster said:

I am curious, what gas block are you using?  I ask this because my first build with a rifle gas system and same buffer and equivalent spring worked perfectly.  One jam using a lancer mag but about 500 other perfect cycles with that mag and pmags.  I’ve since changed to a new barrel for accuracy reasons( same exact model of barrel), but I decided to use a different gas block.  A KaK non-adjustable block.  Now I have better accuracy with the new barrel but for the first time ever, I have about 25% failure for bolt to stay open on empty mag.  This tells me I’m getting less Gas than I was before.  My gas port is the same size as the perfect cycling port was.  Gas Problem I have with this different gas block.  

What kind is yours?

By the way, my gas tube even goes farther than the halfway point with both blocks.  That isn’t my issue.

My gas block is whatever BCA uses......so will have to check and see if thats an item they say they produce or not. It doesnt say from what im seeing they produce those..............so its anybodies guess where its actually from. 

[britx303]

So I dont want to get too far ahead of myself and change alot before ive even tested the new buffer, the spring, and gas tube. But is an adjustable gas block a good idea just to go ahead and put on? For all I know the things im about to swap could be the fix. And for what its worth, I do not reload and likely will only ever shoot factory ammo, but this is where im not sure whether or not an AGB is worth it for shooting different weights/loads.?? In the beginning of my roadracing hobby, I learned early on to stop throwing parts and potential fixes to a problem before each potential remedy has even been tested...........seems like me doing an AGB may be a premature attempt (perhaps even a bandaid instead of remedy) and should first test my new parts......but im the newbie to 308 here, hence asking.

[DustBuster]

1 hour ago, britx303 said:

So I dont want to get too far ahead of myself and change alot before ive even tested the new buffer, the spring, and gas tube . ........seems like me doing an AGB may be a premature attempt (perhaps even a bandaid instead of remedy) and should first test my new parts......but im the newbie to 308 here, hence asking.

Yeah.... I wasn’t suggesting your gas block was to blame... 50% chance it’s a gas related, and I’d bet your longer gas tube is going to help the situation.

I was just using you sort of to find about my sudden “under gas” problem.  If you would have told me 

“ I’m using the KaK non-adjustable gas block”, I would have been a tad closer to diagnosing my new sort of related problem.  I’m sure your block is ok.  I bet my gas block is either clogged, smaller gas tunnel size, or is not centered on the gas port very good.  

Good luck on tests of your one at a time changes.  Good Day Sir

[britx303]

18 minutes ago, DustBuster said:

Yeah.... I wasn’t suggesting your gas block was to blame... 50% chance it’s a gas related, and I’d bet your longer gas tube is going to help the situation.

I was just using you sort of to find about my sudden “under gas” problem.  If you would have told me 

“ I’m using the KaK non-adjustable gas block”, I would have been a tad closer to diagnosing my new sort of related problem.  I’m sure your block is ok.  I bet my gas block is either clogged, smaller gas tunnel size, or is not centered on the gas port very good.  

Good luck on tests of your one at a time changes.  Good Day Sir

All good man :) Best of luck to you too!! 

[edgecrusher]

No need. Standard gas block for the win. If you shoot suppressed then I’d say different story

[britx303]

19 minutes ago, edgecrusher said:

No need. Standard gas block for the win. If you shoot suppressed then I’d say different story

Good deal! All my parts are now in delivery mode, so hopefully I can get it sorted and test ready within a week or so. As of right now I have not gone the suppressor route, but beginning to look into that.

[Unamed_]

 I had a similar issue caused by the lower holding the mag too low. Pushing up on the mag I could get it to run. Also was with a BCA side charger. Lower was a billet 80%. I got the lower replaced and while sorting it out bought an Aero M5 upper and lower. Can’t have too many.

[98Z5V]

I might have missed it here, but I've seen no specifics on barrel dimensions, at all.  What's the barrel length, what's the gas port diameter (we have that part), what's the gas system length (kind have info on that). 

What's the gas block journal size?

I can tell you what your gas port diameter needs to be, if you give me that information, very specifically.

 

[britx303]

6 hours ago, 98Z5V said:

I might have missed it here, but I've seen no specifics on barrel dimensions, at all.  What's the barrel length, what's the gas port diameter (we have that part), what's the gas system length (kind have info on that). 

What's the gas block journal size?

I can tell you what your gas port diameter needs to be, if you give me that information, very specifically.

 

16” mid length. 3/4” gas block journal 

[britx303]

The various magazines arrived yesterday........tracking shows the springco orange spring comes today........but the replacement gas tube showing it comes tomorrow. Was hoping the tube would have arrived today too, so It could be test ready for tomorrow AM, since thats the best time to go to the public range and im off work anyways. Such is life, but I guess i'll have to schedule another sick day after its done Weekends are a nightmare at the public range..........its packed with idiots smoking weed while shooting and will even start shooting when the range is cold and people are down range setting up targets, so during the week first thing in the morning is always best. Fingers crossed she behaves herself.........

[jtallen83]

1 hour ago, britx303 said:

its packed with idiots smoking weed while shooting and will even start shooting when the range is cold and people are down range setting up targets,

What, no sense of adventure? 

[britx303]

4 minutes ago, jtallen83 said:

What, no sense of adventure? 

Pfffft I grew up around the DC area, then lived in Baltimore for a few years................flying bullets were normal if you ever had to drive through certain sections😱...................

[jtallen83]

17 minutes ago, britx303 said:

if you ever had to drive through certain sections

I have had to travel and stay there for work a few times over these last years, I honestly had an oppressed feeling there, otherworldly schit, even dystopian, but then I'm an Iowa Hillbilly............. I don't think I would want to be around there if the money stops, those like you and @Rsquared that worked there should be thanked for your service.

Edited January 27, 2022 by jtallen83

[britx303]

14 minutes ago, jtallen83 said:

I have had to travel and stay there for work a few times over these last years, I honestly had an oppressed feeling there, otherworldly schit, even dystopian, but then I'm an Iowa Hillbilly............. I don't think I would want to be around there if the money stops, those like you and @Rsquared that worked there should be thanked for your service.

You're welcome😁  I had a friend that moved from the area out to Denison Iowa. He came back to visit and brought a buddy from out there with him to check out DC etc. Yeah, he was floored at how cruddy our nations capitol is 

[jtallen83]

19 minutes ago, britx303 said:

I had a friend that moved from the area out to Denison Iowa.

Commerce or FDA? 

[britx303]

2 minutes ago, jtallen83 said:

Commerce or FDA? 

His Mother was originally from there, but moved to the DC area for a gubment job back in the 70's. When She retired from that she wanted to move back, and he moved with his parents to work with his Father as he started a small plumbing business. 

[98Z5V]

On 1/26/2022 at 5:19 AM, britx303 said:

16” mid length. 3/4” gas block journal 

Somewhere between a gas port size of 0.083" to 0.087" for that .308 Win chambered barrel.  I'd go more to the higher side of that range, if it was mine, and I've done that in the past, and it works. Go big, and it won't disappoint you.  Check what you have, and punch it up.

Edited January 28, 2022 by 98Z5V