Just picked up a new Bushmaster Modular Carbine, brought it home and grabbed several boxes of ammo to sight in and check out. I set up at 25 meters and opened fire. Damn I thought, 8" low??
   
   By the time I got the weapon to shoot point of aim, the front sight post base was 20 clicks below flush! This is the rifle with the folding Bushmaster front and rear sights. I tried a several different brands and bullet weights, all with the same effect.

   I wondered if it could just be me, so I grabbed my retired Army drill instructor brother in law. He had the same trouble as I did. Anyone one have any ideas? I know I can send it back to Bushmaster and get it fixed, but dang, I just got it and want to play [>(]  

I can not think of a reason that is a quick fix. Bushmaster will send a pick up for the gun so it does not cost you return shipping. I say send it back.

STS

Wll I sent it off to Bushmaster. I'll se what they have to say, when it comes back.

Before you go sending it back, remember, Bushy makes 5 different front sight posts.  Two are standard height NM sights that vary in width, one is the original A1 style round post, one is the standard height A2 square post and one is a .040 higher A2 post to help match-up the Bushy front sight tower to after market rear sights designed for the M4.

Your front flip-up may have come with the .040 higher sight.  I don't have the spec for the standard post height, nor the means to measure one, but if someone else does, check the height of your front post.  If it turns out you have the .040 higher sight, I will send you a standard height out of my parts box to try.  If it works, you can trade me your .040 post straight up.

BBossman Out

OK, I just made my feeble attempt at measuring a standard Bushy front sight post.  Best I can figure it's about .280 high from the top of the flat to the tip, so the +.040 would be, duh, .320 high.  Let me know what you got.

When I had Ron from Bushmaster on the phone, I measured the sight. I used the "depth probe" on my dial calipers and came up with about .269". Ron said "that's a few thousandths out of spec" but added that souldn't make the kind of difference I was seeing. Ron implied that he wasn't really interested in troubleshooting it, so if I sent it back, he'd just replace the whole upper. That's fine with me, because I kind of buggered up the top of the folding front sight assembly.

Mike

Anyway it went out UPS Monday and I've been following the tracking number to the poin tof obsession [%|] my wife thinks I'm nuts.

Very interesting Michael,I also have a new bushmaster that is shooting to the right and have the back sight cranked almost all the way to the left. At the range I was thinking it was possibly me, my hold or somthing weird. When I finally got it cranked in  my son shot at the same point. One thing I did notice though is a build up of copper in two of the rifling grooves on the right hand side for about 1/4" at the muzzle. bad crown ???? I am asumming you took it back to the dealer to have it picked-up ? let me know how long it takes to get it back. [8] p.s. I have the 20" n.m.

I hadn't noticed any copper in the barrel. But I really hadn't considered the possibility of a bad barrel either. Bushmaster talked about a 1 or 2 day turn around and it's 3 days in transit. I'm in South Bend which is north central Indiana. I'm hoping to have it back by the end of the week. I plan on calling tomorrow to see if they have a status update for me. It's really depressing just sitting here with only my lower.

Mike

Hooray! I finally got my upper back! Apparently the gas block was milled out of spec, causing the flip up front sight to not fully seat. So everything is all better now. It's off to do some shooting.

Mike

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8" inches low sounds about right for the carbine off mechnical zero at 25 yards.

But 20 clicks up elevation on the front site? That's not right, should be more like 5 or 6.

Glad you got it fixed.

James_Gang,

Check fire.

Perhaps you are confused with the 100 yd values.

At 25 yards, an A1 (5 pos post) carbine has a El come up of 0.34" and the A2 (4 pos post) carbine has an El come up of 0.42".

8"/0.42"=19.05 clicks and 8"/0.34"=23.53 clicks.

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Perhaps Tweak.

I just zeroed a new Bushy carbine the other day at 25 meters, per the instructions with the A-2 sight on the Bushmaster 25 meter zero target.

1st shots were low 8 squares, and left 4 squares(oh the squares on the Bushy target are half an inch right?). So that's actually an impact of 4" low and 2" left of center at mechanical zero. So I wonder if the guy is talking inches or blocks.

So, my first string was low 8 squares, and left 4 squares, so I cranked 8 clicks up front sight elevation and 4 clicks right windage per the instructions. No joy.

Therefore, after 19 rounds, from mechanical zero my final sight adjustment was 5 clicks up elevation and 8 clicks right windage to get in the center of the target. Go figure.

BTW, I was using LC M-193.

I figured the difference was caused by the length difference of the carbine barrel, normal variation, etc....

I'll tell ya, I'm glad it wasn't 20 clicks, that damn front sight post was stiff as hell trying to turn it with a round.

Real happy with the quality of the Bushmaster though. Very similar to the old A-1 I used to carry in the Marines, but better. I especially like the A-2's sights and the new handguards.

You got a ballistics chart or copy of a range card for battle sight zero on this rifle?

BFI has a long history of mis aligned barrels. Send it back. On a NM barrel no less.

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I read on the Bushmaster site that they were now boresighting the sights and barrels of all rifles leaving the factory.

What I understand is they do this to ensure the sights will print with a given barrel irregardless of the variations one gets with barrel threads, etc...

In other words you wont have a rifle that shoots point of aim at mechanical zero, but you will have a rifle who's sights can be adjusted to get the impact of the rounds at point of aim.

You know anything about this Tweak?

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M-16 A-2, '25 meter' sight in target. 1/2 inch squares. Bushmaster is shipping these with new rifles. The instructions are to use small peep with one click up range adjustment(400 yards). Then one click front sight elevation for each block, or one click windage for each 1/2 inch block to obtain battle sight zero and the center of the target. Which I assume is approximately dead on at 300 meters, a little high at 100, etc.....

Yes of course sight radius. I understand the barrel thread variance also effects the sights to a higher degree on shorter barrels.

Yes for trajectory at various ranges. I know this varies depending upon the ammunition, but I shoot 55 grain M193 equivalent.

Thanks for the info.

I know better than to trust anything BFI says.

What do barrel threads have to do with sight alignment?

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Pressure on the barrel from the barrel nut/receiver threads.

Dependent upon which side the pressure is on when one headspaces and torques the barrel, the gun will naturally shoot to that side or up or down.

As the front sight is mounted to the barrel, and the rear sight is mounted to the receiver.

The effect is slight, but at range it has an effect.

It's similar to the effect of free floating a rifle barrel on a precision rifle vs. one that is not.

In some rifles this pressure can alter the barrels alignment to the point of the rounds printing outside the sights ability to correct. My understanding is that is why Bushmaster is now laser bore sighting all barrel receiver assemblies to make sure the sights have enough adjustment prior to the rifle leaving the factory.

You'd better break out your ruler bud, the squares are 0.35" by 0.35" on the M16A2 target. Even says that in the USMC -10 I have here by my desk.



One click up on the 3/8 wheel gives you 3/8+1, not 400.



Read the numbers along the top and bottom of the graph. It's 3 clicks of wind per square.



With a 20" barrel it will. There's a lot more variation with the M4 series, most recommend a 50 yd initial intersection that most often equates to a 250 yd terminal intersection.



What barrel thread?



[url=http://www.eskimo.com/~jbm/]JBM Ballistics[/url]

Or, you can zero at the terminal range and check your POI at the intermediate distances.

That is some funny shit James_Gang, you should take it on tour, give Robin Williams a run for his money.

I tried to zero my A2S, my way, without reading the owners manual, and got the same results as above.(my wind knob was all the way to the right)
Like James_Gang  mention  in his reply, I did that, it did the trick.
Windidge know sits dead center now, another things is, I was using the large peep  hole at first, instead of the small peep hole.
Got it all worked out, but was disapointed at first.
Front sight, had to lower in a few clicks.

TG
 

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Yes you're correct, I rechecked. It's 3 clicks windage for each box, 1 click elevation. No matter I had to do it fast and got it in the center of the bullseye at 25 meters.

You're right, it's 3/8 +1, not 400, and 3/8's not 1/2 inch. I'm new to this A-2 drill. But I got the idea, get the point of impact at point of aim at 25 meters with 1 click up range elevation and small peep.

No barrel thread, the barrel nut and receiver threads. The threads can cock barrels slightly to one side or another, or up and down. That's why each rifle needs to be zeroed independently from mechanical zero. As well the difference between shooters sight picture.

No room here to check POI at the range. I currently have no access to an approprite 300 meter range.

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It's a fact.

Think about it.

[url]http://www.bushmaster.com/faqnew/content_by_cat.asp?contentid=154&catid=96[/url]

Tweak I don't have a chrono. So I can't use a ballistics program accurately.

I thought some of you guys may have developed a ballistics trajectory chart based on your own research and time at the range for the M-193 out of the 14.5 inch barrel.

There's a handy quote function available to members. What did James_Gang mention in his reply that did the trick?

James_Gang,

It has been obvious to the members of the board that you have been talking out your ass since your first post. Please desist, this isn't the GD. We don't take kindly to poseurs.

Sight misalignment is caused by many things. None of them are related to the threads on the barrel, the upper receiver, or the barrel nut.

Probable causes of front sight misalignment or, "Why in Hel is my rear sight all the way over?"

[b]1. Barrel installed crooked in the upper.[/b] This is is usually caused by too wide of an alignment notch in the upper receiver. This is the top reason and often a result of kitchen table 'smithing.  Simple fix involves a rawhide mallet applied to the FSB above the barrel and below the "wings" at the top of the FSB. More complex fix involves reinstalling the barrel the military way.

[b]2. FSB installed misaligned with alignment pin on barrel.[/b] Most often seen on bottom feeder barrels and barrels with "indexable" FSBs.

[b]3. Alignment notch in upper mislocated radially.[/b] Harder to detect, this will also cause problems with the bolt due to the timing of the extension's locking lugs.

POI shift caused by sight misalignment will be exaggerated on short sight radius barrels.

Sight misalignment can also be caused by the above three factors, in small degrees, combined. This is the true cause of most misaligment but it can often be corrected by rotating the barrel in the upper as detailed in #1 above.


James_Gang,

Since you seem to want to read about the AR, I suggest that you start [url=http://www.ar15.com/content/books/TM9-1005-319-10.pdf]here[/url] and [url=http://www.ar15.com/content/books/TM9-1005-319-23.pdf]here.[/url] Until that time, read more and post less. It is apparent that you are new to the rifle as well as to the forum.

3064 fps is a good velocity for M193 out of a 14.5" barrel.



[url=http://groups.msn.com/TheMarylandAR15ShootersSite/zeroingmethods.msnw]MD-AR zeroing[/url]

I use a lazer boresighter which comes with a setup target which will let you 0 your sights at 50 or 100 yards. Its real easy to use, you place the lazer into the barrel with an adapter and set up the sighting in target at 25 feet from the front of the barrel, the gun must be securly held in some sort of cradle.You make your adjustments on your sights and thats it.Go to the range and the most you will have to do is minor tweaking. Works with open sights and scopes.If you use one you will know how much of a help they are, if not you will love it when you try one.The kits are about $60 or so.

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Thanks for the disrespectful tone Tweak. Poseurs? Talking out of my ass? I have no messages in my in box.

I didn't mean to rain on your parade.

I started using the the M-16 A-1 rifle in 1979, as an 18 year old boot in the Marines. Although, I certainly wasn't an armorer. As well, as I stated I'm new to the A-2. But certainly not in the area of semi-automatic, etc....firearms in general.

But I will gladly comply with your request, considering I know you have a difficult job here. I see you prefer to do it alone.

In that respect we are more alike than different. Perhaps trying to cultivate a little mutual respect with others here is a good strategy. Or does being a part of the moderation team relieve you of this responsibility?

BTW your preference for Colts over other brands is apparent. That's fine, we all have our preferences. But, sometimes the answer's a little simpler than just sending it back to Bushmaster because of poor quality.

BTW, great forum. It's been very helpful.

S!

You're welcome, thanks for a slew of posts filled with incorrect info that I then had to correct.



Yes, those describe your behaviour perfectly.



And I have no duty to IM you. Just like I told you in my reply to your IM, "You vomit on this board, I call you on it [b]on[/b] this board." You want some consideration on here? Contribute factual, timely, and helpful advice when asked.  



You're not doing anything but wasting the member's time.



I could care less if you're Gene Stoner's third cousin, having Uncle Sugar loan you an M16 doesn't lend you any credibility.



Well the A2 is not new and underneath the furniture it's all the same rifle. So any knowledge you may have is transferable.



This isn't the semi-automatic, etc....firearms in general forum.



More proof you can't, or won't read. Look at my post count genius. I've been on ARF since '98. If I did all this alone dontcha think my post count would be just a little higher? Dano, royce, and many other plank owners here catch quite a few of the questions before I do. Do a little reading, check for yourself.



You'll get my respect when you pull your head out and do some research before you post.



Nope, I simply refuse to nod in agreement with idiotic posts thereby allowing the serious members of this forum to be sidetracked by erroneous information.



If they paid for warranty repair they should use it or it's money wasted. We still give advice on fixing factory and frankenguns if they don't wish to return them.



It is that way bc of the members and their commitment to learning more about the AR.

You're a class act Tweak.

Didn't take long to figure that one out.

I wont be needin' anymore of your help. I'm not sure I needed any in the first place.

BTW, you put many precision rifles together? Accuracy is accuracy. I been working on and shooting precision bolt guns for the past couple o' years, 'till I decided to aquire this M-4 clone. Nice little gun.

No different here, except the sheer number of moving parts, lockup and group sizes. That's why rifles come equipped with adjustable sights in the first place. No manufacturer has found a way to put them all together exactly alike. I call 'em quirks. Like people they all got 'em.

Too bad you decided to turn it into a personal matter. It's your problem entirely.

Keep up the good work, and good luck bro. And remember, be careful out there.

Thank you James_Gang, I'm thrilled you noticed.



It usually doesn't when one pays attention.



Really? What a shame, let me get the door for you. Happy to be of service, tell all your friends.



A couple hundred OAI UM-1/PCR-1 and assorted other "precision" pieces while I worked there. But they weren't really that precise.



Neat.



That's why the milspec calls out the acceptable POI error.



Your posts made it my business and you're absolutely correct, you're posts are now my problem since you refuse to accept responsibility for fact checking them.



Same to you James_Gang, you be extra careful out there, I so wouldn't want anything to happen to you.

BTW, I'm not Rambo but I do know a rambo if that helps.

[ed. for speeling]

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I'm just glad I was able to help somebody.

I didn't mean to offend you. I hope you'll accept my apologies.

But thanks for pointing out my error in measurement. It happens to us all from time to time.

Class act.