AK front sight / gas block question

[nothinghere2c]

So I decided to finally try and fix the cant on my front sight of my Krink. I drove out the pins, and hammered on the front sight / gas block till it turned a bit to where i believe i want it.

my question is this, what will happened if I fire it without the pins in there holding the block onto the barrel? Is there enough pressure to blow the block right off the front of the gun or will it take the lesser resistance path and cycle the weapon normally?

[hermosabeach]

You need to verify the sight is straight
Drill out the holes
Repin the fsb


If not it will move and if you bump it - well back to step one

[nicoroshi]

Front sight by itself can be left unpinned for test fire to determine cant (or lack there of).
Gas block can not.
In the case of the Krink that has a one piece front sight/gas block I STRONGLY recommend not firing the gun if it's not pinned.
The pressure of the gas will move the gas block on the barrel (forward) even if it's a good press fit.
How do I know this?
I saw an IO inc gun that did not have the gas block pinned fire at my home range. Even though the GB was a good press fit the pressure pushed the gas block forward on the barrel almost 1/2" with one shot.

Pin it. Then fire.

[nothinghere2c]

it took a lot to move it. seemed pretty stuck on there. i was just wondering if i shot it without pins if it would blow off the front or stay where its at?

[nothinghere2c]

Front sight by itself can be left unpinned for test fire to determine cant (or lack there of).
Gas block can not.
In the case of the Krink that has a one piece front sight/gas block I STRONGLY recommend not firing the gun if it's not pinned.
The pressure of the gas will move the gas block on the barrel (forward) even if it's a good press fit.
How do I know this?
I saw an IO inc gun that did not have the gas block pinned fire at my home range. Even though the GB was a good press fit the pressure pushed the gas block forward on the barrel almost 1/2" with one shot.

Pin it. Then fire.

ah ok. thats exactly what i was looking for. thank you much!

[Carsgunsandchics]

I used two angle finders to match the front sight to the rear. I placed one angle finder across the flats of the rear sight base, and one across the ears of the front sight, while the front was held in a vice. Then spun the rest of the rifle to match the same angle as the front sight. Basically zeroing the angle difference between the two. Re-pinned and all set.

[ar15barrels]

There are equal forces pushing forward on the gas block that there are pushing rearward on the gas piston.
If you realize how violently a gas piston operated gun functions, you will realize how much force there is on the gas block.

[kcstott]

There are equal forces pushing forward on the gas block that there are pushing rearward on the gas piston.
If you realize how violently a gas piston operated gun functions, you will realize how much force there is on the gas block.

Yep.
Rough math.
35,000PSI .547" diameter gas piston. = 8224 pounds of force exerted.

So yeah pin it.

[Fate]

I used two angle finders to match the front sight to the rear. I placed one angle finder across the flats of the rear sight base, and one across the ears of the front sight, while the front was held in a vice. Then spun the rest of the rifle to match the same angle as the front sight. Basically zeroing the angle difference between the two. Re-pinned and all set.

Were you using digital angle finders or the cheaper dial ones with magnetic bases like this?

[nicoroshi]

I used to do them like this (with good success)>>>



Now I cheat with a laser line >>>

[Dan FS71]

Yep.
Rough math.
35,000PSI .547" diameter gas piston. = 8224 pounds of force exerted.

So yeah pin it.

Yes, ruff indeed. 8k pounds of force on the end of the gas piston would put the b/c threw your shoulder.

Surficive to say there is pressure and it bleeds to some degree between the gas block and barrel and has a tendancy to float the gb like an air hockey puck. It does depend on many factors including if the gb/fsb is 90 or 45 degree.

Get it straight, ream to the next size and pin. If you just pound the pins back into the canted grooves the block my seek equilibrium.

[savagemann]

I used to do them like this (with good success)>>>



Now I cheat with a laser line >>>

I like it Nico.
This reminds me......i need to do a population soon.

Sent from my SCH-I510 using Tapatalk 2

[Carsgunsandchics]

Were you using digital angle finders or the cheaper dial ones with magnetic bases like this?

Yuppers. Works good as long as you can do the simple math of subtraction.

[ar15barrels]

Yep.
Rough math.
35,000PSI .547" diameter gas piston. = 8224 pounds of force exerted.

So yeah pin it.

In reality, the chamber where the the gas piston sits will never reach the full pressure that exists at the gas port because of the short duration of pressure (~300 microseconds) between when the bullet passes the gas port and leaves the muzzle and the restriction of the gas port size in relation to the bore size and the gas piston head chamber volume.

Also, the gas port pressure is around 10,000 psi averaged through the duration of the dwell time.
I would bet on perhaps 5000psi effectively reaching the gas piston head so the operating force is more like 1200lbs.

[nothinghere2c]

Thanks for the hard data. Looks like i've got some pinning to do.