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Posted: 12/22/2003 12:33:26 PM EDT
Greetings and Merry Christmas,  It was just suggested to me that one way I may be able to shoot tighter groups (sub 1/4 moa)when I feel that my gas port is too big (.101 on a bull 24" ss Lothar Walther 1:8 twist )is to invest in and 'adjustable gas tube'.  I have tried all weights of ammo, 75gr shoots best and 69 just a little less favorable.  Problen is that out of every three shots there is at least one flyer stretching the group.  I've has 4 people shoot the rifle, same experience, so I feel vindicated that is not operator trouble.  Being a newbie, I'd like to know more about these adjustable tubes.  Any infoprmation would be greatly appreciated. Thank you, Gus
Link Posted: 12/22/2003 1:20:46 PM EDT
Adjustable gas tube -- did the person suggesting this elaborate on how this will help tighten groups? I have seen adjustable gas blocks for sale. They apparently use a regulating screw that restricts the flow from the block to the tube. Don't recall seeing any claims for improved accuracy from them, tho. I think that about .100 is the port size used on most AR's. Being able to adjust or cut the gas flow has it's uses, such as when hot reloads put out too much gas too soon,and the bolt tries to open before the pressure has dropped to operating level, sometimes causing the extractor to tear the case rim .      
Link Posted: 12/22/2003 3:35:01 PM EDT
Hi Rimfire,  No, he didn't elaborate, just stated that his groups tightened.  The one thing I have learned over the past week is that there are as many opinion as there are manufacturers of these fine rifles.  There is a huge segment of the gun community that have invested a substantial amount of time energy and money into AR's, etc.  And the community has a wealth of information available, you just have to ask in the right place, and the help starts arriving.  Thank you for your response, Gus
Link Posted: 12/22/2003 4:47:40 PM EDT
[Last Edit: 12/22/2003 4:49:46 PM EDT by stormbringer66]
It was me who suggested the adjustable gas tube, rimfire, look at all the posts in that past about problems with asa's and the gas ports being over size, this could cause the problems that gusiris stated in another post, I suggested that if asa did not fix his barrel to try the adjustable gas tube, I put one on mine because of oversize gas port to lower the amount of gas to the carrier so I get consistent action/lockup it seemed to smooth out my gun, I did not say it would tighten groups on it's own, only might help gusiris with his problem.
look at http://www.fulton-armory.com/AGT.htm
Link Posted: 12/23/2003 6:18:05 AM EDT
Stormbringer, his posts clearly say that he was told that the adj block would tighten his groups, whether you said that or not, and I don't doubt you. I think that an adjustable gas system would be one of the things that every competition grade AR should have, allowing the user to adjust to minimum gas required to operate the system. As a varminter, I cut the gas off completely, load singly, this helps save brass that I have prepped for this chamber. Mine is 6PPC, and cheap brass is about .50 a round.
Link Posted: 12/23/2003 2:29:53 PM EDT
Rimfier and Stormbringer,  In all fairness to Stormbringer he never stated that my groups would close.  He said that his rifle now shoots "as stated" after he put on the adjustable gas tube.  ASA guarantees sub moa with the rifle I had built.  I inferred from Stormbringers writing that it meant the groups would close (my wishful thinking).  I sincerely apologhize for any confusion I may have caused.  You guys are great and everything that you both have told me is being digested.  Thanks again and
Merry Christmas
Link Posted: 12/23/2003 2:58:56 PM EDT

What kind of accuracy are you getting now? With and without the flyers? If you're already shooting in the 1/4 moa area, you're into some pretty precise preparation, and I won't presume to give you advice because as you know there are only about 50 things that can keep you from getting to that level, especially with an AR platform. Shooting consistent 1/4 moa groups with ANY rifle is something not many people can do.

But back to your question: If your ammunition is truly loaded to match level it's consistent, so I would think your gas pressure would be consistent as well, therefore I don't know why an adjustable gas block would solve a problem with flyers. Not sure what you've already done to arrive at your diagnosis of the problem (gas pressure) but are you sure it is "on target"?


Link Posted: 12/23/2003 4:48:19 PM EDT
imcoltsguy,  I'm not shooting match ammo, I'm using Black Hills Blue Box, 75 gr, getting 1" to 1/2" consistently with 2 of three shots.  In every 3 shot group there is 1 flyer taking the group out to about 1" to 1 1/2".  On some occasions in a three shoot group there is one shot on top of the other, then a third spreading the group to about an inch.  I'm confident that this rifle is capable of 3 shot knots as a routine.  If you saw the targets, it is positively the rifle.  I've had a few people shoot the gun all with the same results.  The funny thing is, ya never know when the flyer is coming, it can the first second or third.  It's perplexing and downright annoying.  55 gr and 62 gr fodder spreads the groups to over 2", 68 closes it and 75 is ideal.  25 and 50 yards are knots, take it out to 100 yds and the trouble begins.  My goal is 3 shot knots at 100 yards and 1/4 to 1/2 inch at 300 yards.
Link Posted: 12/24/2003 2:26:12 PM EDT
1/4 to 1/2 at 300 ain't going to happen!! You would do well to get that from a custom bolt gun and good handloads. I shoot and custom barrel AR's, and have customers and friends that shoot AR platforms that are premium quality barreled (Lilja, Kreiger,etc) and handload match bullets for match chambers in .223, 6PPC and 6BR. They are doing good to get 1/4 to 1/2 MOA, and these guys use and can read wind flags. Since you are a self described "newbie", I would suggest that you research the capabilities of the AR before you waste a lot of time and money trying to get 1/4 MOA, much less 1/4 inch at 300!! That would be .083 at 100 yards, and I don't know of a factory AR and 'box' ammo that will do that. You will have those that tell you they can, I have yet to see one that will even come close to that consistently. I belong to two clubs with a combined membership of close to 3000, and I see a lot of AR shooters at the benches. I don't see any 1/4 inch groups!!
Link Posted: 12/24/2003 6:54:58 PM EDT
Just get the adjustable gas tube and try it, it locates on the tube just behind the front sight and is adjustable through one of the holes in the mil-spec. handguard.  If anything it is neat to have and won't hurt, especially with heavier bullets, you can adjust it down to the minimum required to cycle the action and that is always easier on the parts.  
Link Posted: 12/25/2003 6:52:51 AM EDT
asltrfl, I have been using an adjustable gas block (I drill and tap my own, I shoot a scoped flattop with clamp on irons)for a very long time, I am familiar with the benefits they give. In light of the post that started this discussion, are you advocating that the adjustable tube will tighten groups??
Link Posted: 12/25/2003 8:07:02 AM EDT
Originally Posted By rimfire50:
...are you advocating that the adjustable tube will tighten groups??
View Quote


Perhaps indirectly, by allowing the action to cycle with less "violence", and possibly even reducing recoil, if adjusted down to just-barely-cycle tune...

I believe I will give one of these a try...
Link Posted: 12/25/2003 8:36:04 AM EDT


Gusiris, do what you want, but if you really want top notch accuracy, I'd suggest you spend your money on match ammo or--better yet--learn to load it yourself, and then shoot a LOT. You are never going to get to that class without proper ammo and lots of practice, and no amount of adding this or that gadget, or fiddling with the rifle in some other way, is going to change that.

Link Posted: 12/28/2003 10:14:09 AM EDT
rimfire50: After seeing all the other 1/4" group posts with out of the box AR's and out of the box ammo it was comforting to see some reality injected into the forum. I have tried most of the gadgets all the high dollar reloading equipment and techniques and after thousands of rounds off the bench all the 1/4" groups I have had were ruined by the 3rd,4th, and 5th shot.
Link Posted: 12/28/2003 11:40:22 AM EDT
Thank you everyone for all of your help and guidance.  It sounds as if I've set my goals unrealistically high.  The gun is still at ASA, I hope to get it back this week.  If I can gather in 1/2 to 1/4 consistently at 100 yards, it sounds as if I should be a happy camper, especially if I'm not using match or even handload ammo.  I failed to mention that this was off a bench (Harris bipod).  I'll see what ASA says, then shoot about 60 rounds, and explore further the need/desire/want for an adjstable tube.  Thanks again for all of  the information and help.  Gus
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