JRoss

Anyone have experience with bushing the barrel gas port hole to a smaller size? Looking for and adjustable .936 steel gas block also.

Fired 3 rounds and block screws loosened. Tightened and 3 more rounds. Screw closest to gas port hole slightly loose and other screw negligible. Signs of slight gas leak at port end of block. Cycling is not working with stove pipes. Will need some more test time to get it right I guess.

Thanks for the welcome....... missed your post and yes a minor malfunction, back together now

I just put it back together with the replacement block and longer screws. I bought some Permatex high temperature thread sealant and applied a thin layer between the barrel and the gas block where the 2 ports meet then tightened the screws. It may or may not help, if it blows out or not at this point an adjustable block is next on the list. Might get a chance to test fire this weekend and will have an allen wrench in my pocket!

Found this link about the AR gas system http://ar15barrels.com/prod/operation.shtml Lots of tech info

I don't want the morons out there to touch it. And yes it is nutz what I am going to do but I really don't trust them after what they sold me. I will put it back together with the replacement block and longer screws they sent me, if that doesn't fix the problem I will proceed from there. I am going to keep this thread going best I can with the progress of the repair as it goes along. And thanks to everyone for all the help and input!

The gas system uses the rifle length 15 1/4" tube on a 24" barrel. The pressure at the large hole in the barrel is not really any higher then a barrel with a smaller hole, the difference is the surface area of the hole is greater with a larger hole. With the larger surface pressure area (.155" compared to say.090) more lifting or spreading power is produced at the contact area of the gas block and barrel. So a more distortion free gas block is going to help seal the gas block to barrel contact area. Of course the original AR10 was designed with a 16" barrel and with optimum hole sizes for proper operation without an adjustable gas system. Here we are 60 years later and people are selling whatever they decide will work.

I have never played with gas port sizes on a .308 ar It will be an interesting opportunity to repair and experiment with different combinations of methods. Hope buying a new barrel does not turn into one of the options.

No Idea

Measured them with drill bit then measured the drill bit with a 0"to 1" outside micrometer.

Transfer hole in barrel to measures .155". Transfer hole in gas block measures .150". Transfer hole in gas tube measures .125". Very different from a standard AR15 configuration.

Longer screws means more clamping force. Looking closely at the original screws there was only 4 threads into the block, that is not much for an 8/32 screw to grip into aluminum. The new longer screws will double the clamping force. I also noticed that the area where the block deformed was at the thinnest area of the block and closest to the gas port hole, not the greatest design on the engineers part

The threads in the aluminum gas block were

I received the replacement part in the mail today. Took a better picture of what happened, original part had the short screws (2) and the replacement has the longer screws. I did mention to them longer screws would help. So it could be possible the original had the wrong screws installed and explains why the block did not hold.

Thanks!

Thanks!

Thanks!

Yes good idea !

Ok you mean to use them as a lock nut to keep the screws from lossening? Thanks for the welcome. If the one they send messes up I will reconsider the option of steel and a set screw type then. Just don't want to stray from original configuration for the time being.

The company sent the block USPS and the tracking number shows it could be here tomorrow. I was able to tap the block and tube off and the tube looks straight but might just replace it if is loose in the block when I reinstall it to the new block. Good info to know about the erosion factor of the aluminum. I will keep the factory part configuration and see if it works properly before I do any changes (easier to diagnose any problems with the tech people at the factory). If I can I like to do my own work so that's why I am not shipping it back. Do you know if there is a specified torque on the 8-32 screws? I think its like 90 inch pounds?

Thanks for the welcome. The company I bought it from assembled it.

Only pic I took. It is a clamp style block and the two 8-32 screws came loose and the block spread open to a gap of about 3/4". Its a single shot charge handle action now.

Hi , just joined and have a new dpms style ar308. 10 rounds fired and gas block failed. It had not functioned properly from the 2nd round fired. Thinking it was a short cycle problem from a leaking gas block. I attached a pic of the end result after the 10 rounds I fired. It is a .936 aluminum block. I am new to the ar 308 so hoping to learn from you all here. Waiting for replacement gas block from the company that assembled the complete upper. Any tips on installation would be fantastic.