Preban PWA with 20" heavy barrel.  Changed out the stock to a collapsible 4 position to accommodate the wife and kids.  After the swap it started short stroking.  My assumption is the stiffer spring in the new stock created a situation where the previous gas pressure is now insufficient.  I have cleaned the gas tube and made sure there were no binds.  I am thinking the gas port in the barrel may be a little fouled.  I plan on checking that tonight.  I was also thinking an ammo issue.  I have some new S&B and some surplus soft point.  It had no problem with the surplus prior to the change so it is unlikely.

I plan to change the stock back out and test to be certain another issue did not come in to play.

Any other suggestions?

The receiver extension entry lip cleaned of burs, and nicely taper to allow the carrier to enter without binding.

Buffer roll pin flush with outer buffer surface.

Buffer spring coil ends cleaned (filed) to prevent the ends from scraping the tube on the way back.

Carrier key tight, and not leaking.

Receiver extension, spring, and buffer lubed with a light coat of CLP.

Correct short buffer and short spring installed for Car stock.

There is a difference in the springs from the stock A2 buttstock and the collapsble buttstock. The spring is shorter and not a stiff. The difference is the A2 spring is like 12 pounds and the collapsible stock is 8 pounds, something like that. Dont forget you have to change the buffer also it is also shorter and thinner.