Things did not go as planned - Newbie needs advice

[Im4Rights]

Project 2 Update:  Last I reported, this project was cycling, but not locking back on an empty mag.  Parameters were 16" mid-length with 11.75" gas tube, .750 journal, .093 gas port (up from the original .063 port size), with 6 7/16 dwell time, and Armalite carbine buffer/spring.  This morning I opened up the gas port to .096 and took it to the range.  It cycled fine and locked back on empty mags, but it kicked like a mule.  I believe I have gone from slightly under-gassed to pretty much over-gassed.  In hindsight, I probably should have tried an H2 buffer first (Armalite buffer is H3).  I'm thinking an adjustible gas block is now in order to dial this puppy back a bit.  Any suggestions for such a gas block?

Here are a couple pictures of my "personal use only" .308 carbine.

 

 

[98Z5V]

8 hours ago, Im4Rights said:

I believe I have gone from slightly under-gassed to pretty much over-gassed.  In hindsight, I probably should have tried an H2 buffer first (Armalite buffer is H3).  I'm thinking an adjustible gas block is now in order to dial this puppy back a bit.  Any suggestions for such a gas block?

What's the details on the recoil system on this one?  Is it all Armalite AR-10 Carbine recoil system parts?  Get this buffer from Clint @ heavybuffers.com, if that's the case, and it'll solve what's going on right now.  Guaranteed.

Scroll down on this page, and look for this one:

https://heavybuffers.com/ar10carbine.html

For .308 ARs with Extended Receiver Extensions:

XH Carbine Buffer (8.5 oz) w/.308R Buffer Spring - $140

XH Carbine Buffer + .308 Rifle Spring

Quantity:

 

If you have an extended (7-5/8" deep) receiver extension on your gun I recommend an XH carbine buffer and a .308 rifle buffer spring. This includes VLTOR A5 tubes and the Magpul UBR Gen2 stock. Many .308 rifles come from the factory in this configuration - LMT, S&W, LaRue, POF, etc.

 

My note - this is next up on my .358 Win AR, to control that heavy-kicking bastard.  It'll happen before November, for sure, be test fired and solved, and be ready to go by Vet's Day weekend.

[Im4Rights]

7 hours ago, 98Z5V said:

What's the details on the recoil system on this one?  Is it all Armalite AR-10 Carbine recoil system parts?  Get this buffer from Clint @ heavybuffers.com, if that's the case, and it'll solve what's going on right now.  Guaranteed.

Scroll down on this page, and look for this one:

https://heavybuffers.com/ar10carbine.html

Yes, this is what's currently installed https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01.  This is gun is a budget build, and I'm not sure I want to spend what they want for that heavy buffer kit.  I think the advantage of an adjustable gas block is that I can tune the gas to match the ammo in use, and if the rules ever change to remove suppressors from the NFA, I'd be ready for that too.  At this point, I may try a stiffer buffer spring and adjust the buffer weight if needed, or put on an adjustable gas block.  If none of those less expensive options work, then I can always try the heavybuffers.com kit.  Thanks for your continued assistance!  I'll keep you updated.

[98Z5V]

On 8/21/2022 at 1:08 PM, Im4Rights said:

Parameters were 16" mid-length with 11.75" gas tube, .750 journal,

For the record, 16" midlength gas (.308 Win gun) with a 0.750" journal should have a gas port diameter that's 0.085".  My range it 0.080"~0.085", but 0.085" works on every gun with that barrel config, with all the ammo, all the time. 

You did go big on that gas port. 

[Im4Rights]

On 7/16/2022 at 9:45 PM, 98Z5V said:

Did you use headspace gauges and check this chamber before firing it?  What ammo are you using?  Headspace check is the NUMBER ONE THING that needs to be done on any large-frame AR build.  Numero Uno.

Second statement - an 18" midlenth gas gun with your barrel specifics needs 0.080"~0.085" gas port diameter, and I recommend the 0.085" end of that spectrum, to make it function correctly.  That's WITH a proper recoil system.  For a 16" barrel, 2" less dwell time, you will need 0.090"~0.095"  - and I recommend the higher side of that range.  Start smaller, try 0.090".  Don't be surprised if it has to go up a little bit.  0.63" is nowhere close to what it needs to be, nowhere.

Fix your recoil system first.  Play with the barrel gas port later - or at the same time.  Start 0.090" after you have the correct recoil system parts installed.

I installed the Armalite buffer kit as recommended, and at .093 it was cycling, but not locking back, so I took it to .096, not imagining that .003 increase would have such a drastic effect.  Live and learn...

[Im4Rights]

Project 2 Update:  On last report, after installing the Armalite carbine buffer kit and opening the gas port to .093, the rifle cycled, but did not lock back on empty mag, so I opened up the gas port to .096 and the rifle cycled properly, locked back, but was over-gassed and kicking like a mule.  As this is a budget build, I did some research and decided on a David Tubb 42-coil flatwire buffer spring ($40 all in w/shipping).   The 42-coil spring is a little tough to cram in the carbine buffer tube, but it seemed to smooth things out a bit.  That,combined with an Adaptive Tactical EX Performance Stock with a vented rubber recoil pad from another of my rifles, has made the shooting experience much more enjoyable.  That concludes my build issues, now on to improving my shooting with both rifles.  Thanks all!

[jtallen83]

1 hour ago, Im4Rights said:

The 42-coil spring is a little tough to cram in the carbine buffer tube,

Coming out is a way bigger pain than the round springs as well but worth the extra oomph in my book. Always liked the idea of being able to stick the spring in any recoil system I want, tend to only use it in the short tubes since the gold standard Armalite spring covers the other two lengths and comes in almost a fifth the price most times.