.040 Higher front sight post?

[daengmei]

How much will the POI change at 100yds if I use a front sight post that is .040 higher? AR-10 that I've put together shoots about 12" high...got rather poor eyes too but the group is around 4".

[NC_JEFF]

The front sight post is adjustable, would that not solve everything

[country gent]

Error X sight radious divided by range in inches will tell you how much to add or remove from the front sight. Error is how much you off on target, Sight radious is distance between sights and range in inches is the distance being shot in inches. so yours would be close to this 12" X 18" / 3600, 12x18=216 / 3600= .060 needed to correct.
If its one of the blade fronts instead of a round post clean it good and you can build it up .060 with epoxy.

[daengmei]

The front sight post is adjustable, would that not solve everything

I'm sure you thought I had no idea what I'm doing.....the sight WAS screwed out till it nearly wobbled, had to turn it back down a touch to stop the movement.
I could have found the formula and worked it out....
I just happened to be a bit lazy today and asked for someone who knew.
I almost always search (no one seems to know how to do that anymore) but this time not.
Even if I had described everything at the beginning, not many read it.
Some just seem to jump in with woulda shoulda coulda.
Sorry for being a jerk.

[daengmei]

Thank you for that formula country.

[BUCKEYE BANDIT]

Might also want to look at if the handgaurd is centered on the barrel,ask me how I know :groner: .
How much will the POI change at 100yds if I use a front sight post that is .040 higher? AR-10 that I've put together shoots about 12" high...got rather poor eyes too but the group is around 4".

[country gent]

Your welcome. Its a lot more work to turn up a new one with the off threads locating detants and small dia pin on top. Another quick way to do this would be to cut the sight pin off at the boss and drill it .040 and press a new pin in long and cut to length. I always set my service rifles up for a 1/2-1 click 200yd zero if possible for several reasons. 1) it kept as much of the sight in the slide as possible for better alighnment, 2) It gave lower zeros for all the different ranges, and 3) it helped maintain a better cheek weld to the stock. What caliber is your AR 10? They have been made in several. What length barrel? Mine is set up as a NRA match rifle with 26" Krieger barrels one upper is 243 win 1-7 twist for the long heavy VLD bullets and the other upper is 22-250 with 26" 1-7 twist for 80 grn sierras and the old JLKs. Gas ports were moved 4" farther forward also.

[daengmei]

.308 and I can't remember the length...18 I think. I never considered drilling and pressing another. That can be done. I am also working with a rather cheap rear sight. I am happy to get things to work, then go for fine tuning. Too many projects.

[daengmei]

I also want to apologize to anyone I may have offended by the above comments. Specifically jedomejd.

[daengmei]

Might also want to look at if the handgaurd is centered on the barrel,ask me how I know :groner: .
I have no problem with deflection right or left, just too high with this rifle. Now that I think about what you said, it certainly could be if the sight was on a hand guard.

The front sight post is in a normal pinned gas block, old style.

I did put together a Colt package and the rear sight (old style handle upper) has to be all the way to one side to nearly get center hits. I suspect the front of the receiver might not be square. I do have a tool that is supposed to correct that. Has grinding compound and fits to a hand drill. Like I said above, too many projects. I keep thinkin I will have plenty to do when I can quit workin....2 1/2 years to go.

[No Blue]

Well as that front post gets longer and longer, you gotta drop the barrel to make all the bits line up. This is where a mini-lathe off CL comes in handy to drill the end of the sight and glue a pin into that.

Here comes the nonsense about 'F' marked FSB's. You got a flat top receiver and a 16" barrel, you need an F. You got a 20", don't make much difference.

[daengmei]

as that front post gets longer and longer you gotta drop the barrel to make all the bits line up
Somehow I'm confused on what your getting at. Of course a taller front sight brings the barrel down when using the same sight picture. I've got a .040 taller front sight post and will see what that does for the impact.

I just read the info on what your referring to concerning the different height blocks and I don't see much worry. Taller pin does it most often.
Thanks
Jim

One more thing, glue is for wood and paper in my opinion. Drilling and pressing is my preference. Everybody rails about JB Weld, I have never had much luck with that stuff in a critical use. I know, mixture ratio....not worth the rework to me and it seems too easy to not have the right amounts.

[NC_JEFF]

Daengmei sir I am certainly not offended, we never know knowledge the poster possesses right away. I hope I haven't offended you with my short answer. I hope you get the sight you need.
Jeff

[country gent]

Pressing is good a rough surface with clearance for JB weld works also My perfered would be to thread it into place and locktite then turn to dia.

[daengmei]

I just checked, I'm using a 16" barrel. Front to rear sight measures 15 3/4". The rear is a NcStar that has a small amount of side to side movement. If I'm lucky I might have time soon to see if the .040 makes enough difference.

[44man]

I glue ramp sights on with Steel Bed when the barrel is too thin for a screw. You can't knock it loose with a hammer. Gluing a pin in will hold.

[44man]

My calculations show you need to raise the front sight .0525 to .054 for 12" at 100 yards. Depends on the formula used.

[daengmei]

Thank you 44, going to see what I get tomorrow or Sunday.

[cub45]

Are you using a A1 or A2 post that will make a difference.

[daengmei]

I'm not sure and honestly didn't know it mattered. This one is .040 taller than issue, according to the vendor. https://dsgarms.com/knssq072ext

Is there an A1 and A2 post for the AR10 in 308? I realize they all fit but I bought initially one described for an AR10. Don't remember having to figure out A1 or A2.

[Three44s]

You may need more than the calculated amount since your sight was loosely screwed in when you observed the amount your hits were low. I.e. Your sight needs added height so you have threaded portion to hold it and that would likely require more height.


Also another load could require yet even more sight height and retaining the ability to change between pins. Gluing or loc tighting things together has it place but I like to run things a while and let critical adjustments sink in before to make sure I won't regret it down the road.

Gluing something on top of a front sight would be exempt from that premise as it is very easy to go back to original dimensions.

Three44s

[daengmei]

I did not use a loose sight pin. I said that I could not raise it more because it became unstable (wobble I said). I did take it back down to lock it in before the reported group.


the sight WAS screwed out till it nearly wobbled, had to turn it back down a touch to stop the movement.

You have misread what my reply was about, an answer to the other post.

[David2011]

You can find the Brownell's sight height calculator using your favorite search engine. Woulda posted the link if I wasn't using the danged iPad.

From a real computer:

http://www.brownells.com/.aspx/lid=13186/GunTechdetail/Sight_Height_Calculator

[daengmei]

I did find that, and using something similar to an eye-pal (homemade, thin black vinyl with sticky back) I will get to shooting sometime this week or so. Thanks

[daengmei]

Shot the AR-10 today. Using a different ammo (I know, shouldn't) and the eyepatch, I shot a group that was now at the lower end of my panel, nearly as far off center the other way from the previous shooting. I know it had a lot to do with using the patch, I now can clearly see the rear peep, not like before where I was seeing a large blur and having to guess each time if I had the same sight picture. The Monarch ammo, steel case, was acceptable for what I was doing. I changed the rear sight for a Wilson Combat I got at Knob Creek and was able to get a group about 6" high. I know I still have quite a bit that I can screw the front sight in for future adjustments. Then I fired the Winchester 7.62x51 target ammo (white box) and now I have hits all over the place. Done with this one, I shot the Winchester from a BM-59. Previously I used ADI surplus ammo and was very pleased with the groups, blur and all. Now the Winchester just doesn't like me. Same as the AR, large group.

I have a bit of LC primed to load and figure the best load for each rifle.

If anybody is on the fence about an Eye-Pal and you are seeing a bad blur on the rear sight, they will help.