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Posted: 2/7/2009 5:25:20 PM EDT
[#1]
What rear sight are you using?
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Posted: 2/7/2009 5:26:08 PM EDT
[#2]
You need a .040" taller front sight post.
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Posted: 2/7/2009 5:28:32 PM EDT
[#3]
Don't smoke so many joints on the way to the range.
Oh sorry, didn't read the rest of the post. Never mind.
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Posted: 2/7/2009 5:32:34 PM EDT
[#4]
Quoted:
You need a .040" taller front sight post. This. Still don't understand why Bushy has never addressed the FSB when the rest of the rifle is not set up for it. |
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Posted: 2/7/2009 5:34:00 PM EDT
[#5]
Quoted:
You need a .040" taller front sight post. This most likely. If the FSB doesn't have an "F" stamp it will be out of spec with a mil-spec rear BUIS. For some absurd reason BM doesn't use FSBs on their flat-tops that are in spec with most rear BUIS. My issue was with an A.R.M.S. 40L rear sight. The fix is as cheap and easy getting the slightly taller post. -JC |
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Posted: 2/7/2009 5:34:32 PM EDT
[#6]
Is it worth calling bushmaster and asking for a different front sight post? Is that really going to correct being a FOOT high?
Today: Aiming a Foot low for the 100yd target. 
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Posted: 2/7/2009 5:37:27 PM EDT
[#7]
Here is the easiest way I know to show you.
This is how a USGI carry handle is made. See how much of the carry handle material is left under the sight? 
Here is a Bushmaster carry handle. It is one milimeter lower. 
If you use a USGI spec rear sight on a Bushmaster then the front sight will be too low and you will shoot high. You will need a taller front sight post. If you use a Bushmaster carry handle on a F front sight base or one of equal height, then you will shoot low and need to crank the front sight post down or shorten it with a file. |
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Posted: 2/7/2009 5:42:49 PM EDT
[#8]
If you use a USGI spec rear sight on a Bushmaster then the front sight will be too low and you will shoot high. You will need a taller front sight post. If you use a Bushmaster carry handle on a F front sight base or one of equal height, then you will shoot low and need to crank the front sight post down or shorten it with a file. I am using all genuine bushmaster parts. The carry handle came with the flat top from bushmaster. What does the "F" designate in the above quote or is that a typo. Thanks for all the input guys, |
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Posted: 2/7/2009 5:44:21 PM EDT
[#9]
Here is another shot. This is as steady as I could get it since they won't sit flat on a counter top.
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Posted: 2/7/2009 5:46:47 PM EDT
[#10]
Bushmaster 0.040" taller front sight post. 
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Posted: 2/7/2009 5:47:16 PM EDT
[#11]
You are allready shooting high at 25 yards, you need to be shooting 2 inches low if memory serves me correct, this will be multiplied at 100 yards. What king of rear sight are you using? If it is the factory carry handle I would just resight in for 2 inches low at 25 -50 yard and give it another try. If you feel the front post is up too far or is wobbly go ahead and order the .040 taller front post. If you have a rear flip up installed you will need that taller post also. This should get you in the ball park.
Edit, I see you are using factory parts. |
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Posted: 2/7/2009 5:48:00 PM EDT
[#12]
The F front fight base if made for flat top carbines. It is a little higher than a regular rifle FSB. Since Bushmaster didn't want to use the taller FSB and have to stock two items, they decided to just mill their carry handles lower instead. It sounds like you got a USGI carry handle.
I bet Bushmaster was running low and outsourced some without thinking. Get a tape measure and see which of my carry handles yours matches. |
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Posted: 2/7/2009 5:53:49 PM EDT
[#13]
Look at the difference at the arrows. Look at the difference in the gap. The USGI has a bigger gap.
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Posted: 2/7/2009 5:53:54 PM EDT
[#14]
My Carry handle looks different than the ones you guys posted. Does this help? |
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Posted: 2/7/2009 5:56:30 PM EDT
[#15]
Quoted:
Is it worth calling bushmaster and asking for a different front sight post? Is that really going to correct being a FOOT high? Today: Aiming a Foot low for the 100yd target. <a href="http://outdoors.webshots.com/photo/2447801090103476461ZUUgOl" target="_blank">http://inlinethumb54.webshots.com/43957/2447801090103476461S600x600Q85.jpg</a> Yup |
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Posted: 2/7/2009 5:58:07 PM EDT
[#16]
My carry handle has the bigger gap of the USGI one buy is milled shorter like the bushmaster.
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Posted: 2/7/2009 6:05:00 PM EDT
[#17]
Weird, all your Bushmaster carry handles have the square forge mark by the knob and mine has a B and a splintered A on the opposite side. That probably also contributes to the difference in space below the elevation drum.
Edit: Yeah, yours looks like a normal low Bushmaster carry handle. I guess you need the taller front sight post anyway. Sometimes things are just a little off here, a little off there, and when combined make the whole thing a long way off. I wonder if your barrel extension is seated in your upper at a very slight angle? I guess that could cause it, but as long as it shoots straight I would just get the taller front sight post. |
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Posted: 2/7/2009 7:02:51 PM EDT
[#18]
Thanks for the input guys,
I will call Bushmaster and ask about a taller front sight post and ask about it shooting slightly left. |
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Posted: 2/8/2009 3:13:00 PM EDT
[#19]
Recently purchased BM XM15 E2S... Reading this article, I compared rear sight units and found that the one fitted to my XM15 is of the Bushmaster type. But I find no "F" stamp on FSB. I am confused as to whether the "F" stamped FSB means the unit is Mil-spec or not. If I understand correctly, BM parts (which are both not mil-spec) should work together and two parts mil-spec will be fine.
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Posted: 2/8/2009 4:06:07 PM EDT
[#20]
Quoted:
Quoted:
You need a .040" taller front sight post. This. Still don't understand why Bushy has never addressed the FSB when the rest of the rifle is not set up for it. Bushie, and DPMS, and Rock River, and Lord knows how many other aftermarket makers don't use the F base or the .040 higher front sight blade because they build their clamp on rear sights .040 inch LOWER.than milspec  So, if you use a milspec height rear sight, the durn thing will shoot high. This doesn't apply just to flat tops. It's also needed on A1 type, and A2 type uppers with a milspec sight assy, and a carbine length barrel.. Sorry, it dopesn't have anything to do witht he aluminum base. The extrra height is in the thickness of the steel sight unit base..
I learned this the hard way a few years back, so now if I'm orderting a carbine length barrel from them I specify the higher blade. F you got a Bushie sight, either they inadvertantly used some milspec sight bases on a batch of sights, or you got a rifle w/a tilted barrel/recie4ver joint (and yes, I've seen that too. 
ETA: Your pics just came up on my ancient computer. Nope, you've got a standard height Bushie commercial sight unit, which is .040 lower than milspec. I'm going to assume the barrel mounting is OK, since that's a fairly rare occurance, so your problem remains a puzzle to me. |
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Posted: 2/8/2009 4:15:01 PM EDT
[#21]
Quoted:
Quoted:
Quoted:
You need a .040" taller front sight post. This. Still don't understand why Bushy has never addressed the FSB when the rest of the rifle is not set up for it. Bushie, and DPMS, and Rock River, and Lord knows how many other aftermarket makers don't use the F base or the .040 higher front sight blade because they build their clamp on rear sights .040 inch LOWER.than milspec So, if you use a milspec height rear sight, the durn thing will shoot high. This doesn't apply just to flat tops. It's also needed on A1 type, and A2 type uppers with a milspec sight assy, and a carbine length barrel.. Sorry, it dopesn't have anything to do witht he aluminum base. The extrra height is in the thickness of the steel sight unit base..
I learned this the hard way a few years back, so now if I'm orderting a carbine length barrel from them I specify the higher blade. F you got a Bushie sight, either they inadvertantly used some milspec sight bases on a batch of sights, or you got a rifle w/a tilted barrel/recie4ver joint (and yes, I've seen that too.
Don't know about Bushy or DPMS, but RRA flat tops get an F marked FSB. One thing that makes it even more fun is that LMT FSBs are F height but not marked 
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Posted: 2/8/2009 4:23:18 PM EDT
[#22]
Quoted:
Don't know about Bushy or DPMS, but RRA flat tops get an F marked FSB. One thing that makes it even more fun is that LMT FSBs are F height but not marked That may be a result of the govt contract awhile back. The RR barrel I got about 4 years sgo didn't have it. 
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Posted: 2/8/2009 4:39:49 PM EDT
[#23]
Is there another source for the taller front sight post? I'm a little leery of paying $$ to ship a tiny part that could be sent with a first-class stamp...
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Posted: 2/8/2009 5:09:32 PM EDT
[#24]
DPMS makes and sells a tall one. Brownells and Midway stock DPMS parts depending on which of the three have it in stock and can get it to you the quickest and cheapest way.
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Posted: 2/8/2009 5:37:07 PM EDT
[#25]
Thanks.
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Posted: 2/8/2009 5:51:42 PM EDT
[#26]
I didn't understand the carry handles being lower thing till the picks were posted in this thread. I went and measured mine and one of my DPMS is lower and the other is milspec. This is a good thing because I had thought them to be both milspec. I had one on a carbine with a Bushy barrel which needed a taller front post and the other on a BCM which needed to have to post screwed down a lot. I switched them and took them to the range today and the BCM zeroed without the post being screwed in so low and the Bushy without a taller post. You learn something new every day!
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Posted: 2/8/2009 6:18:38 PM EDT
[#27]
Re-zero at a different range on top of getting the correct sight post.
That 25 yard zero (essentially a 300 yard zero) you're using will put the round over 5'' high at 100 yards Take a look at this trajectory table for the M4 and you'll see. trajectories Thats why many people use the 50/200 yard zero because it only varies around 2'' from muzzle to 200 yards. |
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Posted: 2/8/2009 9:08:45 PM EDT
[#28]
Quoted:
Rifle: Bushmaster M4A3 Patrolman's carbine. Using PMC .223 ammo. Story: I sent my bushmaster back to the factory shortly after taking delivery because it had excessive windage problems (14+ clicks shooting too far left @25yds. Bushmaster said 8+ clicks left/right is acceptable). I had also adjusted my front sight a few turns up, because it was also shooting very high. I got the rifle back from bushmaster and the repair order said (Reindexed to laser). I noticed that the front sight was in the same position as when I had sent it. I took the rifle to the range today and followed the bushmaster sighting in guide. The rifle shoots 3/4" left and high at 25yards. My problem is this: At 100yds I have to aim a FOOT low to get the rounds into the upper third of a 10.5" square target! (I had a buddy with me who had the same results) I do not want to screw my front sight out any more than it currently sits. Questions: 1. Should I just return it to bushmaster again? 2. Should I just get a taller front sight post?to 3. Am I the problem? 4. I read another post in the archives complaining that bushmaster doesn't use the correct FSB on their flattops. Can someone elaborate? 5. I can post pictures if it will help. I just need to know what you guys need to see. Thanks for any help, -Ben You need to re BZO. or Battle Sight Zero. 25 yd zero is good for 250 to 300 yards. So it would be shooting high at 100 yd target due to trajectory. |
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Posted: 2/9/2009 6:46:35 PM EDT
[#29]
I called Bushmaster today and told them my rifle was shooting a foot high at 100yds. I then said I had been reading online that I needed a taller front sight post. The guy was nice and chatted about the city I live in then said he would have a new taller post shipped out this afternoon. I am happy with the customer service from Bushmaster. When I get the new post I will post my findings at the range.
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Posted: 2/9/2009 6:49:04 PM EDT
[#30]
I think I will do the 50yd battle zero as well.
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Posted: 2/14/2009 2:19:46 PM EDT
[#31]
Quoted:
Quoted:
You need a .040" taller front sight post. This most likely. If the FSB doesn't have an "F" stamp it will be out of spec with a mil-spec rear BUIS. For some absurd reason BM doesn't use FSBs on their flat-tops that are in spec with most rear BUIS. It's cheaper for them to keep two different height front sight posts in stock than two different height FSBs. Could be an oversight on original assembly at BM, but they should have checked this. The good news: it's probably a really easy fix. As long as he's piddling with the front sight, click here for a mod to the stock sight to keep it stable. FWIW; AFAIK; IMHO; YMMV; yadda, yadda, yadda. Regards, Ed Mann Bobby Bowden is doing a fine job - just leave him alone. Albert says, "Click here for free Gator wallpaper." 
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Posted: 2/17/2009 3:53:47 PM EDT
[#32]
I THINK SOMEONE TOOK MY FRONT SIGHT POST!!!
I get home today and find this sitting on the table:  </a>" />
I will have to sort this out with either Bushmaster or the USPS. |
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Posted: 2/17/2009 5:38:55 PM EDT
[#33]
Quoted:
I THINK SOMEONE TOOK MY FRONT SIGHT POST!!! I get home today and find this sitting on the table: http://<a href=http://inlinethumb15.webshots.com/5582/2486827920103476461S600x600Q85.jpg</a>" /> <a href="http://pets.webshots.com/photo/2464192650103476461cLbOCX" target="_blank">http://inlinethumb23.webshots.com/44118/2464192650103476461S600x600Q85.jpg</a> <a href="http://pets.webshots.com/photo/2140201530103476461drtXZW" target="_blank">http://inlinethumb05.webshots.com/6084/2140201530103476461S600x600Q85.jpg</a> I will have to sort this out with either Bushmaster or the USPS. That has to be irritating. 
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Posted: 2/17/2009 8:46:24 PM EDT
[#34]
BASTARDS!!!! Its the help themselves out guys at the post office that stole your post!!!! Call BM and talk to the same guy and explain situation to him. That sux.
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Posted: 2/17/2009 8:51:34 PM EDT
[#35]
You can get a hex head screw I think its 4x8 mm it will thread right in from the bottom you dont need to drill it out and it will tighten and stabilize the post.
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Posted: 2/17/2009 9:19:25 PM EDT
[#36]
What??
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Posted: 2/18/2009 8:13:23 AM EDT
[#37]
Quoted:
You can get a hex head screw I think its 4x8 mm it will thread right in from the bottom you dont need to drill it out and it will tighten and stabilize the post. WHAT? |
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