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Discussion Starter #1
I have a classic with a 1:7 twist rate. I understand that this rate is better suited for the M855/SS109 62gr round. The original Sigs were designed around the GP 90 round, and were optimized for barrels with a 1:10 twist rate.

Ive been shooting Winchester 5.56 55gr ammo lately and I get really great groupings at 50yards. But at 100yds things aren't always so great and i notice random scatterings.

What bullet weight should i be shooting out of this thing? And what kind of accuracy should I expect to be at for 100yds with open sights? I know i shouldn't expect quarter or even 50cent size groupings, just trying to figure out where I should be.

Im technically zeroed in at 100 yards. Just not happy with the groups and cant tell if its me, or the ammo.
 

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I would recommend you try some other ammo for comparison. The heavier grain bullets tend to work better at longer distances -- less affected by wind, and the 1:7" twist can stabilize the heavier bullet.

Every gun is different, and the only way to really know what will work best is to buy a box of each kind you can find (or alternatively, above 55 grains) and run them through the gun and take notes on the results.

For accuracy, my SIGs prefer Federal Premium Gold Medal Match Sierra Matchkings boat tail hollow points (BTHP on the box) 69 grains. 8) They also like the Hornady TAP FPD rounds in 55 and 75 grains (one gun shoots better with the 55 grain, which is why you need to experiment a little...), Hornady Match rounds (75 grains) 8) , and PRVI Partizan Match rounds (69 and 75 grain Match HP).

For general shooting, drills, and just having fun, XM193 55 grain is great, as is Winchester Q3131A1 55 gr. Pretty accurate, too. I also shoot Remington UMC 55 grain with similar results, and it is ubiquitous.

The SIGs really like Federal XM856 tracer rounds, 64 grain, if you can find them, and if your state laws and your range allows their usage. Don't shoot these near anything that can catch fire though.... :shock:

The XM855 is slightly less accurate, but even then, for combat accuracy purposes, more than adequate....

Then go experiment...find the right one for your rifle...and buy that ammo.
 

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Belt Fed said:
Im technically zeroed in at 100 yards. Just not happy with the groups and cant tell if its me, or the ammo.
No offense bud, but if you have to ask, I'd guess its you.

No idea about your level of skill or shooting history, so don't take this personally, but I'm going to rant a little...



Shooting rifles is HARD. Shooting rifles with iron sights is extra hard. The only people I have ever seen that were able to shoot precisely with iron sights at 100 yards or more were people that had been shooting for decades.

I am fairly new to the whole precision thing, I got a scoped .22 last summer which I have put about 8k rounds through, and I recently upgraded my 556 with a 10X scope, and have been able to hold about 1.5MOA or a bit better out past 300 yards. I have practiced a lot, learned a lot, and am starting to feel like I know what I'm doing a little bit.

I still don't think I can shoot precisely with iron sights. With a high power scope, I can look and see how much the cross hairs are jumping around and adjust accordingly. With iron sights, I can't see anything but a little while blob that is the target. To shoot precisely when you can barely see the target means that you aren't using visual ques, such as the cross hairs jumping around, to tell you that you need to focus more, instead, you have to know what you're doing well enough to do everything right without relying on any sort of visual indicator that you're holding it right on the center of the target. You have to have shot rifles enough that your muscle memory is set in with the proper technique without you having to think about it. Like I said I am starting to learn what I'm doing, but I DEFINITELY still rely on being able to see how much my crosshairs are jumping around to remind me if I'm doing anything incorrectly.


Since you say you're accurate at 50, but not at 100, I would also guess that its you, not the rifle. Some lighter ammo will destabilize relatively quickly, but just about anything should get to 100 yards before losing velocity and going squirlly.

You should try some different ammo though. You could try some heavier grain stuff at 100 yards and hope it helps, but it may be cheaper to just try some 55gr and lighter stuff at 50 yards. If you can shoot 40gr accurately at 50 yards, then I would say the 55gr bullets are probably still plenty stable at 100 and the error is definitely yours.



Also, get a good accurate 22 rifle. I have a cz 452. At 50 yards it is more accurate then my sig. It has been invaluable to practice and build skills with, but it is also a great tool to diagnose when i should blame lack of accuracy on my 556 and when the problem lies with me.
 

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Discussion Starter #4
Ive been shooting for years with open sights, and optics and have never had a problem getting a rifle zeroed until I got this thing. I compete in matches with my M1A.

Case in point, shooting American Eagle XM193 55gr at 50 yards looked like a shotgun, switching to the Winchester 55gr tightened everything up and made me happy. The Winchester 5.56 still remained acceptable at 100 yards, but it seems like it could be better, which is why im trying to find out what weight these things like and the whole purpose of this post.

I know you were trying to be helpful, so I'll ignore the part where you're basically telling me to just learn to shoot with a .22 first.
 

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Belt Fed said:
What bullet weight should i be shooting out of this thing? And what kind of accuracy should I expect to be at for 100yds with open sights? I know i shouldn't expect quarter or even 50cent size groupings, just trying to figure out where I should be.

Im technically zeroed in at 100 yards. Just not happy with the groups and cant tell if its me, or the ammo.
...for best accuracy...you should be using the longer bullets in the 68/69 to 75/77 grain range...

...there is a considerable difference in inherant accuracy of the ammunition between "generic" off the shelf plinking ammunition and the better quality ammunition available...the best accuracy is attained using match grade ammunition in the correct length for your exit velosity and barrels twist rate...what i suggested above......

...you say you're technically zeroed for 100yards ?...not sure what you mean here...i'm going to guess you're using the number "1" CQB setting ? ..using this setting as opposed to the apperatures...ie...the #2...#3...#4...will not give you the best possible accuracy but rather more rapid target aquisition...

...your accuracy is also somewhat affected by the width of the front sight blade...more so at longer ranges...and your eyesight...

...you should be able to shoot around 2 inch groups or "better" @ 100 yards with your irons using "good" ammunition in the correct bullet weight/length range...FYI...the sights are calibrated in meters...

...i suggest you use the number #2 apperature with your rifle rested upon a sandbag or something similar for starters until you get used to the sights...you'll "probably" print a little high @ 100 yards...depending on the ammunition you used and how you zeroed your carbine...but your groups should improve considerably...

...i suggest being sure there isn't any movement in your sights !...both the front and rear...
 

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...this is the correct sight picture when using a diopter system...notice the vertical and horizontal lines...the post should be centered as pictured...POI=POA...

 

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Belt Fed said:
What bullet weight should i be shooting out of this thing? And what kind of accuracy should I expect to be at for 100yds with open sights?
My favourite load for a SIG550-2 (7") 100m is:

Sierra 1410 52 grs HPBT-MK
Accurate 2460 - 25,3 gr
Thune Case (Switzerland) 44,5 mm
CCI BR-4
OAL 57,2 mm

On a good day I shoot sub 1 MOA with iron sights.
I use that "Centra Iris Aperture" in the original Stgw 90 Diopter and my trigger is tuned to 3 lbs. total pullweight.
Sometimes I use a special aperture front sight.
Onother thing is to make new and smaller holes (diam. 1,0 - 1,1 mm) into the gas valve to reduce recoil.







If you need more information, write to [email protected]
 

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Discussion Starter #8
ullie,

You're suggesting that instead of using the 100m setting for 100m, that I instead use it for 50m? And for the actual 100m zero setting should be set to 200m and so on? Is that how the Swiss military does it? In either case I see what you're saying.

I picked up a box of Black Hills 77gr match ammo today. This should tighten things up hopefully.

My sights are tight and not going anywhere =)

Fake edit:
scoromongo, thanks for the link
 

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Scoromongo,

Does that Centra iris just fit in, or do you need to drill a larger hole in the aperture drum?

Also, who sells these?

Thanks,

Art
 

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Belt Fed said:
ullie,

You're suggesting that instead of using the 100m setting for 100m, that I instead use it for 50m? And for the actual 100m zero setting should be set to 200m and so on? Is that how the Swiss military does it? In either case I see what you're saying.
...NO...the 200 meter "apperature" will allow you to shoot more accurately than the CQB setting...ie...the number one setting...you should zero as i explained in this reply/linky...when properly zeroed with the correct ammunition...and using the number two apperature @ 100 yards...you will print a little high @ 100 yards...but your groups "should" improve when using the apperature...

... http://www.sigarms556.com/viewtopic.php?t=9010

...the Swiss military zero their PE 90s to preserve the range mankings on the drum using 5.6mm Gw Pat 90 ammunition...and confirm @ 300 meters using the 300 meter apperature...
 

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What Ullie is pointing out is that when you look through a small aperture hole, it reduces the effective aperture of your eye, improving depth of field, and allowing you to focus on the sight and target better. If you shoot with an open notch, you do not get this focus benefit.

Thus, sighting your rifle with the notch will not be as accurate as sighting with the 100m aperture, regardless of the distance you sight it in at.

The notch is meant for Close Quarters Battle, where the speed of target acquisition and peripheral vision are more important than accuracy.

Art
 

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Discussion Starter #12
As you guys stated the groups tightened up considerably when using the 200m setting at 100 yards.

I understand the notch is CQB, but why bother to label it for 100m shooting if it sucks for that? I understand its for quick battlezero target acquisitions. But still. I guess its just being new to diopter type sights.

I didnt adjust the sights at all when using the 200m setting when shooting at 100m, and as stated things printed a little high, but were tight. Im happy with the groups but still feel dumb when trying to get how the Swiss sight in.

In either case, im center on paper for 100, was hitting the metal target at 200 first shot, was hitting the metal target at 300 first shot, and was able to hit the 400 yard gong on my second shot.

Im a little OCD about being bullseye, but i have to accept the fact im not going to hit a quarter size group with open sights, or be dead center every shot.
 
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