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+--- Thread: help (/showthread.php?tid=3344)
help - Jessek - 03-01-2025
hey I have a problem I have a odin works 18 inch barrel diamondback upper and lower diamond back bolt I can not get it to cycle I have tried heavier and lighter buffer multiple different gas blocks the rifle was a 6.5 Grendel before I changed barrels can anyone think of anything that I could try to get it to cycle the farthest the bolt comes back after firing is the back of the bolt is even with the back of the mag will not lock back on last round rifle shoots like a dream I am running Hornady 103 eldx over 28gr of varget for a load thank you
RE: help - grayfox - 03-01-2025
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.
RE: help - StoneHendge - 03-01-2025
28 grains of Varget is a pretty stout load depending on how much energy your lot of Varget has (I've found it to be very inconsistent lot to lot, along with everthing else over the last few years). I'd give a box of factory ammo a try. Sounds like you could be overgassed and the bolt is coming back across the mag before the next round (or follower) has a chance to come all of the way up
RE: help - Jessek - 03-02-2025
(03-01-2025, 09:10 PM)StoneHendge Wrote: 28 grains of Varget is a pretty stout load depending on how much energy your lot of Varget has (I've found it to be very inconsistent lot to lot, along with everthing else over the last few years). I'd give a box of factory ammo a try. Sounds like you could be overgassed and the bolt is coming back across the mag before the next round (or follower) has a chance to come all of the way up
it is stout about 100 fps faster than hornady 103 eldx I have tired different lowers different gas blocks all the buffer weights from 3-6oz carbine tube and spring it has the +1 gas system have had adjustable and fixed gas blocks on it have had 200 rounds threw this barrel trying to get to to work have tried factory and no luck there today I pulled the barrel and can not see anything wrong with it first pic is where the bolt stops the second it with it locked back
[attachment=1030 Wrote:Jessek pid='10159' dateline='1740879721']
(03-01-2025, 09:10 PM)StoneHendge Wrote: 28 grains of Varget is a pretty stout load depending on how much energy your lot of Varget has (I've found it to be very inconsistent lot to lot, along with everthing else over the last few years). I'd give a box of factory ammo a try. Sounds like you could be overgassed and the bolt is coming back across the mag before the next round (or follower) has a chance to come all of the way up
it is stout about 100 fps faster than hornady 103 eldx I have tired different lowers different gas blocks all the buffer weights from 3-6oz carbine tube and spring it has the +1 gas system have had adjustable and fixed gas blocks on it have had 200 rounds threw this barrel trying to get to to work have tried factory and no luck there today I pulled the barrel and can not see anything wrong with it first pic is where the bolt stops the second it with it locked back well it dont look like the pics worked I will see if I can figure it out
RE: help - Jessek - 03-02-2025
may work for pics
RE: help - 300BLK - 03-03-2025
Does the bolt come back and stop with no magazine in place? If so, you have some sort of interference issue between the BCG and receiver or buffer and tube.
If its just hanging up with the magazine in place, try another magazine, preferably a recommended brand magazine (Duramag maybe?)
Rifle +1 gas system on an 18" barrel doesn't leave much barrel length beyond the gas port for dwell time. If it is a lack of gas problem, it could be the gas port doesn't line up with the gas block, or too small of gas port. A lightweight BCG is another option to try.