[pvtsnowball82]

I couldn't find anything about this question in the previous posts, so I'll ask:

I'm about to re-torque the gas block screws on my 580 mini 14 tactical, and I'm wondering how I'll be able to align the gas block once I go to put it back on the barrel. Are there indexing marks or some sort of predetermined fit that will keep the gas block from being canted to one side?

 

[kwg020]

The gas bushing will hold the bottom half of the block in place. You don't have to take the entire gas block apart. Loosen the screws enough for the barrel to move then retighten the screws. Do your best to keep the top half and the bottom half even by checking the gap on either side and retighten. kwg

 

[Drifter]

From Tips & Tricks section:

http://www.perfectunion.com/vb/showthread.php?t=43577

 

[pvtsnowball82]

Thanks for the info, guys. I'm not too worried about re-torquing, as I was able to borrow an in-lb torque screwdriver from a friend. I'm going to go for 35 in-lbs torque with blue loctite. While you're here, let me show you what I'm working with:

This is at 50 yds with irons off a rest (I'm still practicing my breathing and trigger control, hence the spread.). I'm pleased to announce that my new 580 tactical groups pretty well (I think the flyers and the general spread are all my fault), throws brass a couple of feet in a nice little pile, and barely kicks (with the help of fore and aft 1911 shok-buffs).

So I'm thinking the huge disparity in point of aim and point of impact is due to a poorly torqued gas block. Inspecting the block, I can see an obvious difference in the gap on each side. I've heard that adjusting the irons won't quite compensate for the huge difference between POA and POI on some un-re-torqued minis, so I'm thinking I won't touch the sights until I re-torque.

Any thoughts on this plan?

 

[67rschev]

I would say that your rear sight is way off . I never fired my 581 tach before torquing the gas block screws , but my sights were WAY off from the factory . You can eyeball the ghost ring aperture , and mine was set far to the left . Its an easy adjustment , just use the supplied L wrench and adjust one side , then bring the other side screw in or out on the opposite side to match to ove the peep left or right . The rear peep can be adjusted by backing off one or other side screws , and then can be adjusted up or down in 1/2 turn (180* in or out) increments , then re-tighten .

 

[tri70]

Adjust the rear site the same way the groups are stringing to get in line. I also took my gas block and fine sandpaper with round rod and lapped the gas block halves for a little more accuracy gain.

 

[pvtsnowball82]

I guess I was thinking it would be better to wait until after the re-torque since I'd read on PU about other minis that didn't have enough travel in the sights to compensate for the POA/POI disparity until after the gas block had been re-torqued.

I won't have a chance to go shooting anytime soon anyway, so I'll re-torque and then go sight it in at the range (or hopefully the bro-in-law's ranch).

Thanks again for the insight, folks.

 

[Drifter]

Gas block retorque can indeed change POI. You can even purposely torque one side more than the other to shift POI if you're out of sight adjustment. A strut or barrel clamp (such as a bayonet lug) can change POI too.

There can be insufficient windage adjustment on the rear sight if the front sight is slightly canted. The rear sight slot can be successfully dremmeled out slightly if necessary to gain more windage.

 

[pvtsnowball82]

Are minis known for having canted front sights? I've never heard that that was a common problem.

 

[Drifter]

Are minis known for having canted front sights? I've never heard that that was a common problem.

I wouldn't say that it's common, but it happens...

 

[pvtsnowball82]

I also took my gas block and fine sandpaper with round rod and lapped the gas block halves for a little more accuracy gain.

Are you talking about lapping where the gas block halves touch the barrel?

 

[Marlin 45 carbine]

I've yet to see the 189 series M30 that the front sight wasn't way too high and needed careful fileing down to bring the bullet impact up to point of aim.

 

[kwg020]

Snowball
I don't know of anyone lapping the gas blocks but maybe someone has. (tri70) When the gas block is attached at the factory, a gas bushing is inserted into the bottom half and this same bushing fits into a hole that is drilled into the barrel. Inside of the hole that fits the gas bushing is another small hole that lets the gas escape from the barrel, through the bushing and into the lower half of the block and thats when the op rod is pushed to the rear ejecting the spent round and loading the new one.

The problem as I see it, when the two gas block halves are attached and screwed together, the bottom half of the gas block is NOT centered over the hole in the barrel and the hole in the bottom half of the gas block. Or, when the screws are tightened at the factory, they are torqued un evenly causing stress on the gas bushing on one side or the other. When the rifle is fired, this stress causes the bullet impact to stray from the point of sight.

To fix this stress all you need to do is loosen the gas block enough to make sure there is no side load (pressure) on the gas bushing and then torque down the screws evenly. If you do one side first and then the other side, this may cause the gas block to move left or right causing more pressure on the side of the gas bushing. The bottom line is:

Make sure you have the right tool. I think it's a 9/64 hex head wrench.
Be patient.
Tighten the screws evenly.
Leave an even gap on each side of the gas block. You don't have to measure it. It can be "eye balled".

Torque it so it won't come loose. Do NOT "farmer tighten" the screws. You don't need it. If you want, put some lock tight on the screws. I suggest you do it after you shoot the rifle to see if your POI is good to go. Keep in mind, not every Mini has a gas block issue that requires the gas block to be checked.

I don't have a torque wrench but after working on helicopters in the National Guard I have an idea what 35 inch pounds of torque is. Do not over torque the screws as they will break off. I suggest you have 4 new screws available. I also suggest you keep the screws the same. If you break one replace all 4 and keep the others for spares. But, that's just me.

Don't over think this and turn it into a chore. You may not have to touch your gas block. I would only do it if you run out of left or right rear sight. If you are pretty much centered and your brass is not going 30 feet, I'd leave it alone. If you are shooting low and your rear sight is all the way to the top, I'd start filing off the front sight a small amount at a time. Here again, do not over do this. If POI is all over the target, get a strut, better ammo and maybe a trigger job. Start small and work up. kwg

 

[pvtsnowball82]

Short update:

I removed the gas block, gave everything a good cleaning and reinstalled the block with 35 in-lb torque on the screws. Once I took it apart, it was pretty obvious how it all should fit back together. But thanks all the same for the info; I tend to be overcautious when messing with tech I don't yet fully understand.

The gap between the gas block halves is even all around now. I'm taking the mini out to the range tomorrow to (hopefully) zero it in at 50 yds with iron sights. I'm looking forward to tinkering with this gun some more. Thinking about bedding the stock and floating the gas block next.

 

[Marlin 45 carbine]

'over cautious' is good.
check the muzzle crown with a magnifying glass too. any roughness (likely from ruger) then polish it.
if there is any perciptible shake in the stock-receiver fit then shim/bed it.
use good ammunition. cheap wolf won't cut it.

 

[pvtsnowball82]

The cheapest I've fed my mini is Remington UMC. Usually I shoot PMC Bronze, which is always in ready supply at my local gunshop.

 

[tri70]

Are you talking about lapping where the gas block halves touch the barrel?

I sanded both halves were they touch the barrel and gave the barrel a light sanding to get the best mated surface.

 

[pvtsnowball82]

Range Report

Took the mini to the range today. If I could figure out how to get photos off my stupid phone, I'd show the resulting targets...but I guess you'll just have to take my word for it.

Before the gas block retorque, groups were about 4 inches right and 6 inches low (relative to point of aim, at 50 yds with irons). After the retorque, the first four rounds I fired were dead center and about 6 inches low. So I would say retorquing helped tremendously. I simply adjusted the elevation on the rear sight and now my POA and POI match.

Thanks to the people on this forum, my mini shoots great. I would have been so disgusted with it if I didn't have PU users to explain everything! I'm looking forward to further accurizing my tactical; I'll keep everyone updated on my progress.

Thanks again!

 

[tri70]

If you are using a laptop you can use the blue tooth from phone to transfer pics.