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Posted: 9/23/2002 2:14:06 PM EDT
Just got back from the range attempting to sight in my new flattop RRA M4 upper with an ARMS #40 flip up sight I bought from Pete_in_NH. Anybody else have to back the front sight post almost all the way out to get a 30 meter zero?

Something I'm doing wrong?
Link Posted: 9/23/2002 2:23:16 PM EDT
[Last Edit: 9/23/2002 2:24:32 PM EDT by Rickus]
I bought a flat top from pete along with an arms 40. I just had it barreled by bushmaster but i have not taken out to the range yet. i asked bushmaster to zero the barrel to the sight. i hope they did.
I am going to the range this weekend and i will give you a report. what barrel did you put on it and who installed it?

Link Posted: 9/23/2002 2:46:33 PM EDT
im guessing the barrel is an RRA, I bought the whole thing from Pete.
Link Posted: 9/23/2002 3:19:17 PM EDT

Originally Posted By jsinz:
Anybody else have to back the front sight post almost all the way out...

Yes. We had exactly that problem yesterday.

Bushmaster 16" Flat top with ARMS #40. Trying to zero the more precise (small) aperature at 200Yards. Was hitting a few feet high. Had to back the front sight almost all the way out to get on paper.

May have to go with a taller aftermarket front sight post if you want to use the #40.

Aparently the ARMS #40 designers dont understand the large ghost ring type aperature is used only at night and at extrememly close range. The more precise small aperture is used at all other ranges.
Link Posted: 9/23/2002 5:13:32 PM EDT
The problem isn't with the #40 as they function perfectly on our M4's, but if you compare a std. gov't M4 front sight to some non Gov't front sight towers, the Bushmasters are sometimes a little lower for some reason. Some of the after market rear sight folders even are too high for the Bushmaster and some of the others makers front sight towers.
Good Shootin, Jack
Link Posted: 9/24/2002 9:09:41 AM EDT

Originally Posted By 3rdtk:
The problem isn't with the #40 as they function perfectly on our M4's

Okay, so Bushmasters front sights are out of spec.

So what is the ARMS recommended zero for the #40, Which aperature at which range?
Link Posted: 9/24/2002 11:39:49 AM EDT

Originally Posted By AR15fan:
Aparently the ARMS #40 designers dont understand the large ghost ring type aperature is used only at night and at extrememly close range. The more precise small aperture is used at all other ranges.

The large app is designed to be used out to 250 meters, the small one from 250 on. In the Army we used the large app out to 300, with great success.
Link Posted: 9/25/2002 10:53:24 AM EDT
[Last Edit: 9/25/2002 10:54:47 AM EDT by FrontSightAR15]
This is confusing. I had asked Bushmaster in the Industry topic section if the ARMS #40 OR the DPMS Det. BUIS would be compatible with the Bushmaster standard front sight on my 16" M4 Pre-Ban. THEY SAID YES! I asked about the same problem the original poster here is experiencing and AGAIN Bushmaster (as well as two posters) said the problem would not happen. WHAT'S THE DEAL FOLKS? Will my front sight post be poking above the sight tower ears if I use a ARMS #40 BUIS on my Bushy M4 or not?
Link Posted: 9/26/2002 7:34:19 AM EDT
I've got an ARMS #40 on my RRA 16" LEGP rifle. I'm not all that happy with it because after flipup, the default aperature is the large aperature.  

After spending about 30 minutes, I couldn't zero at 50 yards using this aperature.  Switched to the small aperature and sighted it in without any problems.  

It appears to me that the large aperature is next to worthless and to deploy the sight, the sight must be flipped up once then flipped again to select the small aperature.  

Why wasn't the small aperature the first selection?  This is a severe limitation IMHO.

Referring to the front sight post, on my gun, it is very high, approximately even with the guards.  It does not appear to be a problem.

Link Posted: 9/26/2002 8:04:38 AM EDT
I like the fact that the big apreture is the default.  If I am using my BUIS it is because the optic has failed.  If there are targets at close range that need to be engaged quickly, I want the big apreture.  It is quite a bit faster at close range.  If the targets are farther away, I will have the time to switch apertures.
Link Posted: 9/26/2002 12:20:32 PM EDT
Alot of people really like the #40. But I think alot of those people have never used it at the range.

So far nobody has said they were able to get a proper battle sight zero using the #40.

One person was able to zero the small aperture for a 50M near zero a which gives around a 250M far zero. Not bad a bad BZO, but his front sight post is backed way out.
Link Posted: 9/26/2002 12:29:18 PM EDT
So is what I'm hearing correct, that only a Colt flattop, barrel and front sight will allow a proper zero with the arms 40? I do know that Colt front sights are not the same heights as others because only a Colt carry handle will work with an all Colt upper. So are arms 40's only intended to be used with Colt M4's???

Anyone know what the heck is going on here???

Hopefully someone can straighten this out...
Link Posted: 9/26/2002 1:05:28 PM EDT

Originally Posted By AR15fan:
So far nobody has said they were able to get a proper battle sight zero using the #40.

One person was able to zero the small aperture for a 50M near zero a which gives around a 250M far zero. Not bad a bad BZO, but his front sight post is backed way out.

I zero at 50 yards with the big (0-200) apreture.  It shoots really flat, with a far zero of like 240 yards.  This is the aperture I would use most of the time.

The small aperture then has a near zero of like 35-40 yards, which should give you a 300 meter far zero.  Just like the the M16A2.  It is not so flat (6" high at 200), but you can make torso shots out to almost 500 yards.

I use this zero with my A2 rifles too.  It works great.  With the ARMS, the post does have to be a little higher than the A2s, but no higher than with a detachable carry handle.
Link Posted: 9/26/2002 6:52:29 PM EDT
Ok not to throw this into a tail spin here BUT... I just bought an ARMS 40 (monday) from Mounting Solutions Plus in Florida and was asked if I wanted to try the BRAND NEW #40 that is shorter... "Shorter?" I asked "yes shorter as in the small aperture is to be used at 250 meters not 500..." Which makes since to me since this is going on my M-4. So I believe the problem is with everyone having to run their front sight post up so high is your trying to line up your sights as if you had an A2 sight set on 500 and were trying to shoot 250. Is that about it? Can someone with a set of calibers measure the height of their sight from the flat top to the bottom of the Small aperture and post it? Also I noticed that my small aperture is not cut off and notched.

IPSC_GUY (causing trouble) sends

Link Posted: 9/27/2002 11:51:21 PM EDT
I'd like to see if we can get anymore people to chime in on this one....BTT....
Link Posted: 9/28/2002 12:56:45 PM EDT
Recently sighted in a #40 with a bushmaster flattop w/ 14.5" + phantom flash suppressor.  I did not even have to adjust the front sight!  Elevation was right on at 50 yrds following the Improved Battlesight Zero at http://groups.msn.com/TheMarylandAR15ShootersSite/improvedbattlesightzero.msnw.
Only had to adjust about 12 clicks to the left.  I have the #40 which has the flat top open aperture above the small aperture.
Link Posted: 9/30/2002 3:20:00 PM EDT
I have a BM bought around 98-99.  I have the same problem with the GGG flip up sight. I end up replacing the front site post with a Cdn army one, which is longer than the one it came with.  Of course, BM and GGG both blamed each otehr for the problem.......,.
Link Posted: 9/30/2002 4:27:57 PM EDT
I just sighted in an ARMS 40 yesterday on a flat top 20" w/ Colt A2 profile barrel.  Bothe the barrel and the sight were bought used on EE.  

I used the large aperture at 50 yds.  Took about 10 shots, once I remembered the windage knob was backwards...

The aperture is very close to centered, and I only moved the front post 3/4 turn.

Maybe the #40 works better on a 20" barrel?

Link Posted: 9/30/2002 6:11:45 PM EDT
Let me have some opinions and give you my experience as well. I have had my bushmaster m-4 for less than 10 mths. I added a cemore float tube like knights. I added a fulton gas block. a bushmaster front flip up site and a arms 340 rear. my gunsmith set it up. It was closr to hitting center for me shooting cans from 25 to 40 yards. Gas block has alan screws and is hard to get perfect to factory sight in. I had to go on look center wise for from site. But no matter what i cant get rear site close to center but once and it was still not centered. If i move front sight it looks canted. If i move little impact does not harley move. i also tried moving my cheak spot weld and that helps but not enough. Today i shot it and got it sighted in again after about third time. I got my 300yd peep centered on 25yrd target perfectly. But when i use gost ring its to the left some. shoots consistantly. at 100 both are alittle to left too. But the arms 40 gost is all the way over to left to do this. I'm temted on putting my original front site back on and take gas block off. i had this set up for about 5 months. I had a pwa with 16" disapater with colaspable stock and shot it very accuratly at 200yrds. Is everyone having problems sighting in sights other than factory? I'm left handed and arms 40 looks like its made for righty. I got my clamp on bm battle/carry handle sight and mounted it on in front of arms 40 and centered each sight with the mark in sight and mark on sight mount. I can tell neither the arms40 or the handle battle sight  sights line up!!!!!!  Look and tell me if yours looks this way.
Link Posted: 10/3/2002 12:23:14 PM EDT
Well that didnt seem to clear much up. Is there anyone from ARMS on the board who can officially clear things up?
Link Posted: 10/3/2002 1:59:52 PM EDT
[Last Edit: 10/3/2002 2:03:33 PM EDT by mrcr0603]
I zeroed my 14.5" Bushmaster with #40 at 25m, which is the longest distance I have access to.  I had replaced the ARMS aperture with the standard A2, and zeroed with the unmarked (small) aperture.

The final position of the front sight post is flush, as in its initial sight setting per the FM/TM.

Link Posted: 10/11/2002 8:45:58 PM EDT
Link Posted: 1/1/2003 11:40:55 PM EDT
[Last Edit: 1/1/2003 11:42:34 PM EDT by NYPatriot]
Question answered once & for all...

Bushmaster's reply to the BUIS compatibility issue...

When Colt came out with the A3 design with the detachable carry handle they made the front and rear sights .040" higher than the sights used on A1 and A2 rifles. The front sight forging is the same but the front sight post when set for mechanical zero is even with the top of the sight ears instead of below them as the plane for the sight post is milled higher. You will notice on 20" A3 barrels there are two raised bands on the barrel under the handguards. This designates that the barrel has the front sight base with the front sight that is milled high for the front sight post. Colt parts lists have a different part number for the higher front sight base barrels and sight bases for A3 and M4 barrels. 

        We decided when we began to build the A3 models with detachable carry handles that we would keep the sight heights the same for all models. Our A3 handle, Flat-top Rear Sight and Rear Flip Up Sight has the same rear sight aperture height as on the A1 and A2 receivers so that all barrels with standard height front sight bases will interchange. The Mark Brown Flat Top Mount also uses this same rear sight height.

        The A.R.M.S. Swan Sleeve and # 40 Flip Up Rear Sights have the higher rear sight aperture height. When used with standard height front sight bases the front sight post must be turned out to the .040" higher position where it is even with the top of the sight base ears for mechanical zero.

        We now carry a .040" taller front sight post, part number 9349056-M for $4.95, to correct this difference.

        The taller front sight post should not stick up any further above the ears than the sight posts used on the Colt barrels.

        Thank you.
View Quote

Link Posted: 1/2/2003 1:40:59 PM EDT
I've found something like this to happen with just the regular Bushmaster A2 sights using a detachable carry handle.

Never did much close in shooting with my AR15s so I never checked the zero with the large aperature.    I had a great zero established for the smaller precision aperature though and knew how it shot at most all ranges.

The way I found out that the large aperature was hopelessly off?   Was shooting an action rifle match and when we had a stage with the targets moved in closer, I flipped up the large aperature sight thinking that "close range calls for close range aperature".    I found that at a distance of like 15 yards I would get impacts about 6-8 inches higher than my point of aim.

After that course of fire I shifted over to an unused range to double check POI to POA, the small aperature was within the realm of "realistic" while the large aperature was just about downright hopeless.

Not really what the deal is, there shouldn't be that dramatic a change in POI between the aperatures unless they have different center axis heights with respect to how they are drilled/reamed.

Link Posted: 1/2/2003 9:57:49 PM EDT
NYPatriot, thanks for the great info from Bushmaster.

I had no problems sighting in my ARMS #40 on a Colt M4 flattop upper with 16" HBAR barrel (AR6721 upper) using the Improved BZO at 50 yards.  Must have had the taller front post.

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