Polish piston binding

[Max Sirena]

So I have a polish kit I'm building on a childers polish she'll and I'm at the finish line with the build, the bolt carrier fit great and cycled fine until I pushed the barrel on. The piston seems to bind in the gas tube with a lot if resistance and without the gas tube on it it bumps the gas-block on the top edge enough that it doesn't seat correctly. Piston is a #s matching set with some wobble.

[tujungatoes]

Hmm...hard to say. assuming your front trunnion isn't riveted in crooked it shouldn't bind unless the barrel is bent. Did you have any trouble pressing the barrel in?

[Max Sirena]

No problems pressing in the barrel, went in like butter, barrel looks straight, trunion looks good and properly align with the receiver, I've been racking the hell out if it in hopes that it "wears" in smoother and it locks into battery with a forceful pull on the charging handle but if I do a short pull like one for a chamber check, it binds. Would it be acceptable to take some material off the piston tip? FYI tried another polish carrier and same woes. 😔

[Alex$]

If I understand what you are describing:

On the left you see a sectional view of a properly fitted piston inside the gas block. On the right is an improperly fitted piston hitting the top of gas block. Is that what you have going on?

[Alex$]

Use some parallels and check if your rails are parallel with the barrel axis. Sounds like your front trunnion is not riveted in true.

Take a picture of your front trunnion, the front where it meets the receiver and post it.

[Max Sirena]

The pic of the piston bumping the top of the gas block is accurate to my dilemma, I will snap some pics and post tomorrow morning so I can confirm my alignment (night shifter). Thanks for the responses guys!

[ar15barrels]

So I have a polish kit I'm building on a childers polish she'll and I'm at the finish line with the build, the bolt carrier fit great and cycled fine until I pushed the barrel on. The piston seems to bind in the gas tube with a lot if resistance and without the gas tube on it it bumps the gas-block on the top edge enough that it doesn't seat correctly. Piston is a #s matching set with some wobble.

Did you trim the ejector?
A carrier will often slide past the long ejector when there is no gas tube to properly align the piston.
Once you install the barrel and gas tube, the piston is now aligned correctly and the bolt is not going to slide past a long ejector anymore.

Did you install a new piston to the carrier for 922r
Is your piston installed tight into the carrier?
Most pistons will PURPOSELY be left loose by 1/2 a turn before the rivet is installed.

[Max Sirena]

My ejector was trimmed down and if I measure it from the outside wall to the tip of the ejector I'm getting .57" . The piston was not replace but it seems to have enough loose wobble like my other aks...
Here's some pics to show what I'm working with.'

[Max Sirena]

[ar15barrels]

My ejector was trimmed down and if I measure it from the outside wall to the tip of the ejector I'm getting .57" .

I don't know that I would trust working to a measurement.
Check if the ejector is BINDING the bolt.
If it is, relieve until the binding is gone.

The easy test for binding of the ejector is to simply install the carrier WITHOUT the bolt.
The ejector will bind against the bolt, not the carrier.
See if you still have the problem without the bolt present in the carrier.

If the carrier moves freely without the bolt and tight with the bolt, the ejector binding against the bolt is a likely cause.
Another cause of binding could be rails that are so high that the bolt won't slide freely.
You can check for that with ONLY the bolt (no carrier) in the receiver.

[Max Sirena]

Thank you gentlemen for all your input and advice, after some shortening of the ejector, adjusting of rails I got this puppy cycling well, checked my headspace now I just need some time to get her to the range!

[tujungatoes]

Glad to hear you got it worked out.