03-01-2025, 04:09 AM
Welcome to the forum. New rigs can have various issues, I'll confess I don't know them all.
Others may chime in too.
But start from the basics. You say the barrel, upper and lower receiver, what other parts?
Many rigs when new, the parts need to wear into each other.
How clean are the internals? Are you running it wet or dry?
Get some hornady 108 or 105 factory ammo, and shoot at least 50 rounds, even if you have to do it one at a time. Starting off with factory rounds will eliminate the ammo as an issue. Some of the fail-to-lock back issues have cleared up for me that way.
You talk about buffers, start with a mil spec spring and 3.0 oz buffer weight.
That reminds me, is this a rifle stock or carbine butt stock? Carbine stock is best, I've built several and the couple of rifle stock builds always had cycling problems. Sure you can "fix" it but start with carbine butt stock system first, carbine spring and 3.0 oz weight.
Once everything is running you can play with it further.
There could be excess leakage somewhere, it sounds to me like under gassed, probably from the start, what about the gas key - and gas tube, they are verified clear and seating correctly to each other?
Gas block is aligned, did you check? Some barrel journals/gas blocks are set to have the GB butt up against the rear edge/shelf at the back of the journal, others need that little gap. Also, as for gas blocks, put a stock, plain jane GB on there with no adjustments, until you have it running, then play with any others you want.
Is this rifle gas or mid-gas?
What kind of mags are you using, swap mags a bit to see if it is that mag or not.
Do you know for sure that the bolt head spaces correctly to this barrel. What about the bcg, can you swap it out for another.
Can you swap your bolt for another.
This is part swap out parts-- do them one at a time; and part analyze and diagnose, type of problem. So you'll need to work through the parts one at a time. Unless by observation you can spot where something is hanging up or not working correctly.
Others may chime in too.
But start from the basics. You say the barrel, upper and lower receiver, what other parts?
Many rigs when new, the parts need to wear into each other.
How clean are the internals? Are you running it wet or dry?
Get some hornady 108 or 105 factory ammo, and shoot at least 50 rounds, even if you have to do it one at a time. Starting off with factory rounds will eliminate the ammo as an issue. Some of the fail-to-lock back issues have cleared up for me that way.
You talk about buffers, start with a mil spec spring and 3.0 oz buffer weight.
That reminds me, is this a rifle stock or carbine butt stock? Carbine stock is best, I've built several and the couple of rifle stock builds always had cycling problems. Sure you can "fix" it but start with carbine butt stock system first, carbine spring and 3.0 oz weight.
Once everything is running you can play with it further.
There could be excess leakage somewhere, it sounds to me like under gassed, probably from the start, what about the gas key - and gas tube, they are verified clear and seating correctly to each other?
Gas block is aligned, did you check? Some barrel journals/gas blocks are set to have the GB butt up against the rear edge/shelf at the back of the journal, others need that little gap. Also, as for gas blocks, put a stock, plain jane GB on there with no adjustments, until you have it running, then play with any others you want.
Is this rifle gas or mid-gas?
What kind of mags are you using, swap mags a bit to see if it is that mag or not.
Do you know for sure that the bolt head spaces correctly to this barrel. What about the bcg, can you swap it out for another.
Can you swap your bolt for another.
This is part swap out parts-- do them one at a time; and part analyze and diagnose, type of problem. So you'll need to work through the parts one at a time. Unless by observation you can spot where something is hanging up or not working correctly.