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AR Sponsor: bravocompany
Posted: 8/12/2007 12:53:13 AM EDT
I've got a DPMS M4 scoped. At 100 yards it's very accurate but as I go out to 300 yards it shoots to the left. I have to aim 10-12" to the right just to be on target. Same problem with a verity of ammo.

It's an M4 with a free float aluminum hand guard.

The scope on the flat-top A3 receiver is giving me a straight line of sight. It seems that the barrel is aimed to the left by just a little bit.

The rifle got a little damage during shipment. I'm wondering if enough force was applied to one side of the box it might have pushed on the barrel and bent the upper receiver where the barrel is seated. After all the upper is just aluminum. Does that make any sense?
Link Posted: 8/12/2007 5:51:06 AM EDT
[#1]
If your scope rifle shoots accurate at 100 yards, then I don't think is the rifle.  Winds has little or no affect at 100 yards, but at 300 yards, yes.  Was it windy that day.  Another thing about scope is that they are very sensitive and it might just be the scope.

I have never use scope on AR-15, but have on bolt action rifle.  I was taught how to shoot iron sight in the Marines and confidently hit human size object at 500 yards.
Link Posted: 8/12/2007 10:16:06 AM EDT
[#2]
So does it shoot this way with iron sights too, or jsut with the scope?  i think comparing the two sighting systems will rather quickly tell you if it is the rifle or the scope...
Link Posted: 8/12/2007 4:37:20 PM EDT
[#3]
Yea I did try it wil open sights at 200 yards and it was a bit to left as well. I just used 55 grainers for that first time.

It does feel like as the distance increases the more of a diviation I got. Most my other ARs (1:9" Right Hand Twist) shoot great and only at 450 yards the bullets start dropping down to the right not the left. This AR shoots up to 100 yards and then start pushing the bullets to the left of the target.
Link Posted: 8/13/2007 4:16:37 AM EDT
[#4]
If you are shooting left with both iron sight and scopre, then I think sighting in the the problem.
Link Posted: 8/13/2007 4:27:04 AM EDT
[#5]
Canted scope?

mike
Link Posted: 8/13/2007 5:43:34 AM EDT
[#6]
He has same problem with iron sight, so we don't know if is an external factor or canted  scope or iron sight.
Link Posted: 8/13/2007 5:55:55 AM EDT
[#7]

Quoted:
He has same problem with iron sight, so we don't know if is an external factor or canted  scope or iron sight.


I read his comments regarding that above, but as he did not bother to note whether he has actually zeroed the irons on this rifle I did not take that to mean that his FSB is canted too.

mike

eta - one can assume almost anything here, none of which will make up for the information not included in the OPs comments, (for instance his "Yea I did try it wil open sights at 200 yards and it was a bit to left as well. I just used 55 grainers for that first time".) comment does not instill alot of confidence that these irons were properly sighted in before the scope was mounted, so the "does it both with irons and scope" comments I assumed were taken out of context, which like your assumption - either of us could be right or wrong here......

Assumptions can never make up for the lack of proper information when making a diagnosis of a problem.

YMMV, but before mounting a scope, I zero my irons (BUIS rear & FSB). IF the rifle was damaged in transit - "this" is when the damage will be apparent and even one new to these rifles would know they have a problem, I see no indication of this in his thread

I suspect most know that a properly zeroed rifle (irons only no scope) with a non-tweaked/canted FSB shoots true no matter what the range, zeroed at 50 yards she'll be on at 200. We don't know whether this was actually done in this case. Not done, using the irons to check the scope is this case is just pissing into the wind.....
Link Posted: 8/13/2007 10:39:50 AM EDT
[#8]

Quoted:

Quoted:
He has same problem with iron sight, so we don't know if is an external factor or canted  scope or iron sight.


I read his comments regarding that above, but as he did not bother to note whether he has actually zeroed the irons on this rifle I did not take that to mean that his FSB is canted too.

mike


OK, Mike, this is not my first AR nor is it the first time I've ever sighted one in. I've built many ARs and it's safe to assume that I know just a little bit about them. Further to which I did have the rifle sighted in properly before the scope and now it still shoots left even with open sights. As well, I would never ship a scope still mounted on the rifle (I use a separate box). In this case the scope was not a part of the shipment. Mike, what do iron sights have to do with this issue?


Quoted:
eta - one can assume almost anything here, none of which will make up for the information not included in the OPs comments, (for instance his "Yea I did try it wil open sights at 200 yards and it was a bit to left as well. I just used 55 grainers for that first time".) comment does not instill alot of confidence that these irons were properly sighted in before the scope was mounted, so the "does it both with irons and scope" comments I assumed were taken out of context, which like your assumption - either of us could be right or wrong here......

Assumptions can never make up for the lack of proper information when making a diagnosis of a problem.

Mike, what I can't seem to figure out is what is that you are stating here. Is it that the rifle is shooting left because i didn't zero in my iron sights? or is it that my comment about the 55 grainers didn't instill confidence that the iron sights were zeroed?

Truth is I'm not sure why you are caught up on iron sights and stating that I didn't bother to mention all the information. Well let me make it clear for you:  WITH THE SCOPE THE RIFLE SHOOTS VERY WELL AT 100 YARDS AND TO THE LEFT TO 300 YARDS (Wind accounted for). If you see a connection to the iron sights here I'm willing to listen to you argument.



Quoted:
YMMV, but before mounting a scope, I zero my irons (BUIS rear & FSB). IF the rifle was damaged in transit - "this" is when the damage will be apparent and even one new to these rifles would know they have a problem, I see no indication of this in his thread

Q. How would you solve this problem if you had a flat top varmint rifle with no iron sights?

I’m not sure what you mean. You’re either stating that I didn’t indicate whether the iron sights were zeroed in or not, or you’re stating I didn’t indicate whether or not the rifle still shoots left with open sights and scope both. Well I’ll answer both:
1.) Its does not matter if the iron sights were zeroed in or not, assume it’s a flat top with a plain gas block. i.e. no front sight.
2.) I did indicate that out to 200 yards the rifle still shoots left with open sights
That is why I added that at 200 yards the rifle still shoots left with the 55 grainers. I can't see the target very well at 300 yards with open sights and that is why I stopped at 200. There is every indication in this thread that I've had the same problem with open sights.


Quoted:
I suspect most know that a properly zeroed rifle (irons only no scope) with a non-tweaked/canted FSB shoots true no matter what the range, zeroed at 50 yards she'll be on at 200.

Ya don't say!


Quoted:
We don't know whether this was actually done in this case. Not done, using the irons to check the scope is this case is just pissing into the wind.....

I still can't understand how my iron sights will effect or help resolve a problem with a scope being very accurate at 100 but off to the left at 300. What are stating here?

==========

Mike, please do me a favor and approach this problem as if there are NO SIGHTS on this rifle. You can assume that it’s a flat top with no front sight just a scope.

Here is the Problem: With the scope (ZEROED IN AT 100 YARDS) this rifle shoots very very accurately. However when I shoot out to 300 yards I have to aim 10" - 12" to the right to get a hit on a calm day without wind. This happens consistently.



Link Posted: 8/13/2007 11:12:05 AM EDT
[#9]
Okay, no irons at all.

IF this scope is mounted "square" with the rifle, (ymmv, but we use a string level - bench the rifle and level with string level setting perpendicular to the bore on the flat-top- then setting the little string level atop the elevation turret [cap removed] of the mounted scope - so that scope and rifle are square with each other - meaning there is NO canting of the scope; which is "one" reason a scope might shoot left or right depending on the cant direction, at "distance" after being on at 100)...

then you might indeed have a rifle that somehow in transit got damaged.

As to the irons, sorry I was unaware there were no irons at all on this rifle, as it seemed there were as you said they shot off at distance too....

Not knowing your experience level, I assumed that "IF" it had say a BUIS rear and standard FSB and you zeroed the irons at say 100 and "they" were off substantially in windage at 300 then "this" would have been the first good indicator that something weren't right with this rifle - even before the scope came into play.

Good call to send it back, and understandable that one would be confused over a rifle shooting in this manner. Hard to imagine, short of having the shipping box run over by a truck; that a shipped rifle or upper could become so outta whack. I know the shipping guys, UPS or USPS ain't the most gentle crowd but bending the barrel is mistreatment to the extreme in my book.

Hope this helps with making my point of possible scope canting above and my apologies for the confusion. Skill levels of posters are not aways apparent, so at times it's "best" guess.

mike

Link Posted: 8/13/2007 12:00:11 PM EDT
[#10]

Quoted:
Okay, no irons at all.

IF this scope is mounted "square" with the rifle, (ymmv, but we use a string level - bench the rifle and level with string level setting perpendicular to the bore on the flat-top- then setting the little string level atop the elevation turret [cap removed] of the mounted scope - so that scope and rifle are square with each other - meaning there is NO canting of the scope; which is "one" reason a scope might shoot left or right depending on the cant direction, at "distance" after being on at 100)...

Now that is a great point. I didn't consider the scope being 100% in-line with the bore. Following this advice I'm fixing to head out and change the mounting of the scope. So far it's been on 2 YHM risers. I'll change it to a one piece mount which has a lot more contact with the top of the flat-top. Any suggestions as far as a solid one piece scope mount would be a great help, Thanks.


Quoted:
then you might indeed have a rifle that somehow in transit got damaged.

That is what I'm afraid of. If enough force was applied to one side of the plastic box it might have been enough to (not bend the barrel) but bend the aluminum upper receiver at the point where the barrel is seated in it. This is why I posted here, I wanted to know if that is possible. If the A3 flat-top upper can bend at the point where the barrel is seated in it.


Quoted:
Hope this helps with making my point of possible scope canting above and my apologies for the confusion. Skill levels of posters are not aways apparent, so at times it's "best" guess.

mike

No apologies necessary Mike. I was just a little frustrated that the topic jumped to iron sights. Your advice is sound, refreshing and well appreciated. I will change out the mount and see if that was the cause.
Link Posted: 8/13/2007 12:47:04 PM EDT
[#11]
A buddy had a DPMS 24 bull delux that he could never seem to get zeroed with a scope.  He took it to a gunsmith and the barrel was not inline with the reciever.  

I don't know how you'd fix this problem.  If anyone does I'd be curious to hear about it.

Dad had the same prob with an A2 upper and figured out that the handle was bent.
Link Posted: 8/13/2007 7:01:14 PM EDT
[#12]

Quoted:
Canted scope?

mike

Yup, it sure turned out to be a problem with the YHM risers.

I just got back from the range and this little DPMS was a treat and pleasure to shoot. I replaced the two YHM risers with a one piece riser and mounted the scope on it. The rifle shot true out to 500 yards. I was hitting 6" steel dongs at 100yards, 200yards, 300yards and 500yards with minimal windage correction.

I'm about as pleased with this as I can be.

Many thanks to everyone who helped out and to Mike (mr_wilson) who solved the problem with that “Canted Scope” comment.

PROBLEM SOLVED!!!
Link Posted: 8/14/2007 4:47:54 AM EDT
[#13]
While there are several methods for "squaring" a scope to the rifle, those little string levels (I like the Stanley, aluminum ones) can be a real help when mounting scopes.

To be honest, given the amount you were off at 300, I had my doubts that this could be the problem here, but a canted "mount" can create far more deflection, (obviously) than a slightly canted scope.

Glad your problem is fixed.

mike
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