.308 14.5" Mega Arms cycle issues

[ravensch51]

I have just finished a 14.5" .308 Mega Arms build and am having some issues. The barrel I used is a Red X Arms Stainless 1:10 RH twist 16", diamond fluted bull barrel. We crowned the barrel and reamed it out (professionally done) to 14.5" actual barrel length and ported the barrel. The barrel is chambered in .308 and I am shooting 168 gr Hornady Tap and I am using a .308 carbine buffer and spring. But I am having issues with stove piping. The spent casing is not ejecting completely from the chamber before the next round is fed forward. So I immediately thought it was a gas issue and we drilled out the gas port 1/1000th larger and it is still doing it.

How large/small should my gas port be?

Could I fix the issue with a lighter buffer? Or remove weight from the buffer I am currently using...

Ideas? Insight?

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[IronMonster]

Personally unless you where sure the gas port was undersized I would think the last thing you want to do is drill it out, at least until you actually knew what the issue was. Over gassing might mask the real issue but its creating a problem to solve another.

What bolt/carrier did you use? How does it lock up? How wet are you running the bolt? Before doing anything else I would run a few other types of ammo through it and try some other magazines to get a better feel for whats going on. .308 AR's are more picky about whats parts you put in them. There are a number of known issues mixing bits so whose upper/bolt/spring/buffer you use can make a difference.

 

[ravensch51]

Wet gun, nickle boron bcg and gun locks up tight and shoots accurate when on first shot.

 

[IronMonster]

How much overstroke is there on the bolt? Do you have any sort of booster on the extractor spring?

 

[ravensch51]

No booster. Running a 5.4 oz 3.260" .308 carbine buffer. What do you mean by overstroke on the bolt?

 

[IronMonster]

How much distance there is between the bolt face and the bolt catch when the bolt is all the way retracted with the charging handle. There are some variations in the length of carbine receiver extensions. My Aero M5 guns would not run with a standard buffer tube and the standard DPMS .308 buffer and spring. Actually they would run but the carrier crashed into the receiver because of over-travel. My issues where solved by going to parts made/sold by Slash @ Heavybuffer.com. My issue was too much travel though, you may not have enough depending on the receiver and extension. .308 stuff is not like 5.56 parts in that there is a military standard/spec. SR25/LR308/DPMS stuff should all work together in theory but in practice it simply does not.

will the bolt stay back on the last round? I still say before you do much else you should shoot some other ammo and try a different brand mag. Most feeding problems are mag related.

 

[ravensch51]

Gotcha, I will check that when I get home from work. Yes the bolt locks back perfectly with the last round. I will try another mag and ammo, but I don't think that is the issue. I have a matching upper and bcg and lower that I run a 20" Mega Arms 1:10 RH on with no issues whatsoever. The only difference is the barrel. I run the same buffer and spring as well.

This has been very helpful so far, thank you for your help here...

 

[IronMonster]

I have had ARs that simply wouldn't run until they had 100 rounds or so through them as well. Just enough friction in the system to give you problems but they broke in relatively quickly

 

[FA9]

I have had ARs that simply wouldn't run until they had 100 rounds or so through them as well. Just enough friction in the system to give you problems but they broke in relatively quickly

Same here, I had problems with a recent blkout build until I rapid fired the sheit out of it then it worked out pretty good after that.

 

[U8395279]

Gotcha, I will check that when I get home from work. Yes the bolt locks back perfectly with the last round. I will try another mag and ammo, but I don't think that is the issue. I have a matching upper and bcg and lower that I run a 20" Mega Arms 1:10 RH on with no issues whatsoever. The only difference is the barrel. I run the same buffer and spring as well.

This has been very helpful so far, thank you for your help here...

Perhaps try a lighter buffer spring. Maybe that would help. I've never seen a ported 14.5 inch barrel before on any AR rifle. That seems like an unusual configuration. I don't think that I have seen an arrangement of ports quite like what you have before either.

The barrel must somehow be part of the equation as to why this is happening.


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