Ar gas block leaking

[300 RUM]

I have battling an accuracy issue for a month or so now. I have remedied some other issues but would like to hear what others have to say about gas block leakage and accuracy. So lets hear what you have to say about accuracy when your gas block leaks.

I cant tell you how much it leaks but it diffidently leaks and maybe not all the time.

 

[firearmdoc1]

I may be wrong, but I don't think a leaking gas block will affect accuracy. On the other hand it will definately affect function. I would recommend replacing your gas block just because it is leaking. You can get a good adjustable block and tune it to allow the action to cycle the way you want.

 

[300 RUM]

I may be wrong, but I don't think a leaking gas block will affect accuracy. On the other hand it will definately affect function. I would recommend replacing your gas block just because it is leaking. You can get a good adjustable block and tune it to allow the action to cycle the way you want.

What about a lower pressure being generated by the leaking gas block? Or lets say it leaks a little all the time and then it leaks a lot and then it leaks just a bit?

 

[firearmdoc1]

Once the bullet has passed the gas block the gas left in the barrel is bled off through the port,through the gas tube and into the carrier key. This is what allows the action to function. Low or high port pressure will cause numerous problems but in my opinion will not cause accuracy issues.
If you are having port pressure which varies from one round to the next, it is a good chance that it is an ammo issue, not a gun issue.
I have used cheap ammo in the past and had function trouble in the past because of port pressure problems. Switched to good ammo and the problems went away.

 

[300 RUM]

Once the bullet has passed the gas block the gas left in the barrel is bled off through the port,through the gas tube and into the carrier key. This is what allows the action to function. Low or high port pressure will cause numerous problems but in my opinion will not cause accuracy issues.
If you are having port pressure which varies from one round to the next, it is a good chance that it is an ammo issue, not a gun issue.
I have used cheap ammo in the past and had function trouble in the past because of port pressure problems. Switched to good ammo and the problems went away.

Good description but not bad ammo in this case.

FYI this is a custom AR-10 (Armalite) 308, the rifle is capable of 1/4 min groups. What I am getting at is one or two flyers out of 5 that will hit high and low exactly 2.5 min of of original POA. At 200 yards three will touch, 2 will fly to the like I said exact 2.5 min off POA . Oh not always the first round also.

Keep thinking for me, I'm listing lol

 

[jonbearman]

If the barrel is freefloated then I would look at the torque of the barrel nut.What ammo are you using and bullets etc? How much do you let it cool between a string of fire.How ccoppered is the barrel? Just simple ideas but soemtimes we overlook the obvious.Is it an armalite or dpms configuration.How tight sdo the recivers mate up?

 

[firearmdoc1]

Take a look at the gas tube where it goes through the barrel nut. If it is touching either side ofthe barrel nut this can cause accuracy issues.
I would also look at what jonbearman suggested. Loose barrel nut is not out of the question.
Try folding a piece of tape over a few times and put it under the rear lug that the takedown pin passes through. This will tighten the upper/lower fit and give it a try.

 

[ar15topgun]

I would also suggest touching up the crown. Are you hand weighing each round to a .10 of a grain or less in your powder loads The off call shots, are the vertical or random out of the group?

 

[mac86951]

Gas block leaking shouldn't cause an accuracy issue, but then if the gas block is loose, or moving, or the gas tube is bumped onto the barrel nut, that can cause a change in harmonics as temperatures rise thereby changing accuracy.

What kind of gas block is it? Is it retained by setscrew against a dimple in the barrel (or several) or is it a clamp on style? Again, a leak shouldn't be causing an accuracy issue, but if it is wobbling that certainly will.

Don't worry too much about barrel nut torque. 30-90ft-lbs is the spec, mostly just to get a hole lined up for the gas tube (don't let it touch the sides).

Also, check your sights. Scope? Are all the mounts tight? Is it shifting backward under recoil?
Open Sights? Does the Rear sight have the indexing springs, and/or does it bind up on recoil?

Barrel free-floated? If not it should be! (ha well, that can be a source of issue).

Break installed? Is it torqued, or is it coming loose?

Finally, try some powder variations (0.1gr, or so) to see if you have a shift in accuracy from use/temperature/conditions?

Then look at crown/throat wear, or other barrel issues.

-Mac

 

[300 RUM]

This is what the target looks like, I simply copied the impact points.

 

[mac86951]

Interesting. I'd look at an optics issue or loose mount, but let me guess, the last rounds are the fliers?

Is it possible your neck tension is letting the bullet slip around, or a mag feeding issue? Try single loading a group and see if you get similar results. Look to change the leaking gas block, it could be getting sloppy when the barrel heats up which would shift your barrel harmonics.

-Mac

 

[rcw3]

FYI this is a custom AR-10 (Armalite) 308, the rifle is capable of 1/4 min groups. What I am getting at is one or two flyers out of 5 that will hit high and low exactly 2.5 min of of original POA. At 200 yards three will touch, 2 will fly to the like I said exact 2.5 min off POA . Oh not always the first round also.

Keep thinking for me, I'm listing lol

1/4 MOA capability but only getting 2.5 MOA groups.

How do you know it's capable of 1/4 MOA groups if all you're getting is 2.5 MOA groups? I don't understand that. It would be a very very rare AR-10 indeed that would be capable of 1/4 MOA groups on a consistent basis.

 

[300 RUM]

Interesting. I'd look at an optics issue or loose mount, but let me guess, the last rounds are the fliers?

Is it possible your neck tension is letting the bullet slip around, or a mag feeding issue? Try single loading a group and see if you get similar results. Look to change the leaking gas block, it could be getting sloppy when the barrel heats up which would shift your barrel harmonics.

-Mac

Made a new gas block today

This is on a mid 600yrd / long 1000yrd range gun that would shoot 1/2 min groups all day long, single feed all the time 22 rounds per match set normal for me 15 min at times.


At first I thought a loose barrel, so i TOOK THE RIFLE COMPLETELY APART. Re torqued the barrel ext, barrel nut checked the load against the original all is fine. the only thing left is the OPTICS

 

[300 RUM]

FYI this is a custom AR-10 (Armalite) 308, the rifle is capable of 1/4 min groups. What I am getting at is one or two flyers out of 5 that will hit high and low exactly 2.5 min of of original POA. At 200 yards three will touch, 2 will fly to the like I said exact 2.5 min off POA . Oh not always the first round also.

Keep thinking for me, I'm listing lol

1/4 MOA capability but only getting 2.5 MOA groups.



How do you know it's capable of 1/4 MOA groups if all you're getting is 2.5 MOA groups? I don't understand that. It would be a very very rare AR-10 indeed that would be capable of 1/4 MOA groups on a consistent basis.

This is a new problem for the rifle it was shooting 1/4min groups now shoots 3 rounds at 1/4 min and sticks some exactly 2.5min to the lower left and upper left. read the all posts before you commit

 

[rcw3]

A consistent .5 MOA is a workable number with an AR-10 with everything just right and done up right with the right parts, barrel and loads but 1/4 MOA groups on a consistent basis is not realistic.

 

[300 RUM]

A consistent .5 MOA is a workable number with an AR-10 with everything just right and done up right with the right parts, barrel and loads but 1/4 MOA groups on a consistent basis is not realistic.

In the photo you will see two groups, 1 is high left of center, the other is just left of center. You will also see two holes to the left 3/4min away these are not as bad as some and what I am trying to figure out. They happened on the second group of three. the lower right hole in the ten ring don't worry about it it was from a scope adjustment.

The reason there are two groups is because of scope adjustment

Target was shot at 200yards

 

[300 RUM]

You can see here the elevation changes without moving the POA. I made a 3 min adjustment up and down with no luck the scope is the problem

 

[PRECISIONWELDING01]

I have had several ar-10 shot in 1/4 MOA no problem .everyone I sold though why do I do that ?building one right now not for sale. One help with gas leakage would be go with a high quality clamp on gas block Robert Whitley makes a great one.hope you get issue fixed