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Posted: 12/10/2013 12:12:10 PM EDT
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First post here, so go easy on me please...
Was out shooting a little with my AR the other day, and tested some different .223 ammo. The target below was shot at 50 yards. The rifle is a POF P415 with 14.5" barrel; I am shooting on a bench with a GPS-02 grip-pod, and optics are Elcan SpecterDR 1.5-6x. So it should be good equipment. With Winchester MatchKing BTHP 69 grain match ammo, I got OK groupings. However, with Federal Lake City ammo, every single hit was to the left, spread out up and down within the area indicated with the black oval in the picture below. Now, I can understand why the bulk ammo would not give me as tight groups as match ammo, and that bulk ammo would be higher or lower than the better ammo. What I don't understand is why the bulk ammo is always to the left. Always. Not a single time did the bulk ammo go to the right. No other rifle I have ever shot has displayed such big difference in behavior between ammo types. Any ideas why? Why is the bulk ammo so left-wing?? http://www.pbase.com/w220/image/153711541/original.jpg |
| i'd be more concerned that match ammo is well outside 1 moa...at 50 yard you SHOULD be within the 1 inch circle, also, i do beleive that much deviation(~8 inchs left at 50 yards) should NOT be possible even when changing from bulk to match ammo, my guess it doesn't look like a stabiliation issue since theirs no keyholes...what type of chamber is it? (5.56, .223, or .223 wylde) are youpossibly shooting 223 out of a 5.56 chamber? |
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Changing ammo will change POI left to right. A firing gun is a dynamically moving machine, the key to accuracy is that it moves exactly the same way each time. Benchrest guys tune their loads so that they find where the gun is least sensitive to changes since practically, you can't make ammo exactly the same. Still, change the ammo, and it will behave differently.
That said, that seems like a pretty big shift. I would expect it to be in the 2-3 MOA range. If you switch back and forth does each ammo group consistently in the same spot for each type? |
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OP: what is the barrel twist? What weight was the LC ammo -- was it XM855 (green tip) or XM193 or something else? Different weight bullets, different ammo charges, different velocities between your match ammo and the LC stuff would easily account for the variation.
BTW: I shoot Lake City XM855 green tip with 1 MOA accuracy from a 16 inch carbine profile barrel with 1:9 twist. Your 50 yard groups seem too big for match grade ammo. I'm wondering if your twist is correct for the bullets you are shooting. 69 grain bullets ought to be ok with 1:9 (just barely) but you'd do better with 1:8 or maybe 1:7. |
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You shoot 855 moa out of a 16" barrel? At what distance? ...moa changes based on range...meaning 1 moa at 100 yards is 1 inch, while 1 moa at 200 yards is now 2 inches etc etc...so askign what distance someone is shooting moa is ...kinda silly dontcha think? |
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...moa changes based on range...meaning 1 moa at 100 yards is 1 inch, while 1 moa at 200 yards is now 2 inches etc etc...so askign what distance someone is shooting moa is ...kinda silly dontcha think? Quoted:
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You shoot 855 moa out of a 16" barrel? At what distance? ...moa changes based on range...meaning 1 moa at 100 yards is 1 inch, while 1 moa at 200 yards is now 2 inches etc etc...so askign what distance someone is shooting moa is ...kinda silly dontcha think? It is silly. I was not thinking but I know enough to know m855 does not shoot 1" groups at 100"s out of 16" barrels. |
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It is silly. I was not thinking but I know enough to know m855 does not shoot 1" groups at 100"s out of 16" barrels. Quoted:
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You shoot 855 moa out of a 16" barrel? At what distance? ...moa changes based on range...meaning 1 moa at 100 yards is 1 inch, while 1 moa at 200 yards is now 2 inches etc etc...so askign what distance someone is shooting moa is ...kinda silly dontcha think? It is silly. I was not thinking but I know enough to know m855 does not shoot 1" groups at 100"s out of 16" barrels. Length of barrel has much to do with velocity... Not so much related to accuracy. |
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Length of barrel has much to do with velocity... Not so much related to accuracy. Quoted:
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You shoot 855 moa out of a 16" barrel? At what distance? ...moa changes based on range...meaning 1 moa at 100 yards is 1 inch, while 1 moa at 200 yards is now 2 inches etc etc...so askign what distance someone is shooting moa is ...kinda silly dontcha think? It is silly. I was not thinking but I know enough to know m855 does not shoot 1" groups at 100"s out of 16" barrels. Length of barrel has much to do with velocity... Not so much related to accuracy. I understand that as well but have seen 855 group better out of longer barrels at shorter distances. The problems is in the fact that 855 is not moa ammo out of a 16 inch barrel at 100 yards no matter how good the barrel. Also im not trying to be a dick . When people post shit like that it leads to false hope and misguided buying by other members of the forum. Its not fair to anyone here to spread false information. |
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I understand that as well but have seen 855 group better out of longer barrels at shorter distances. The problems is in the fact that 855 is not moa ammo out of a 16 inch barrel at 100 yards no matter how good the barrel. Also im not trying to be a dick . When people post shit like that it leads to false hope and misguided buying by other members of the forum. Its not fair to anyone here to spread false information. Quoted:
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You shoot 855 moa out of a 16" barrel? At what distance? ...moa changes based on range...meaning 1 moa at 100 yards is 1 inch, while 1 moa at 200 yards is now 2 inches etc etc...so askign what distance someone is shooting moa is ...kinda silly dontcha think? It is silly. I was not thinking but I know enough to know m855 does not shoot 1" groups at 100"s out of 16" barrels. Length of barrel has much to do with velocity... Not so much related to accuracy. I understand that as well but have seen 855 group better out of longer barrels at shorter distances. The problems is in the fact that 855 is not moa ammo out of a 16 inch barrel at 100 yards no matter how good the barrel. Also im not trying to be a dick . When people post shit like that it leads to false hope and misguided buying by other members of the forum. Its not fair to anyone here to spread false information. i've seen winchester m855 get 2 moa accuracy out of a 16 inch hammer forged barrel(this was at 100 yards btw), and lake city m855 .8 moa out of a 16 inch bull barrel from a custom rifle i had the chance to shoot(again 100 yards), so i don't think the barrel length really affect accuracy that much rather the qaulity of the barrel, profile of the barrel, and qaulity of the m855 it's shooting. |
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Your question has nothing to do with accuracy.
To answer your question….It’s pretty simple. When you shoot, the barrel rises (recoil) and shifts to right or left (depending on your twist that can be a right or left twist). Different bullets (with different weight and velocity) will spend more or less time in your barrel. So it will shoot higher/lower/to left/to right. For example a heavy bullet will spend more time in the barrel before exiting. So the POI will be higher (because the muzzle has risen more when the bullet exits compared to a ligher, higher velocity round). I know it’s counter intuitive that a heavier and slower bullet would strike higher at 100 yard, but that’s the way it is. Same thing for the poi to the right or to the left (has to do with the twist) |
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You shoot 855 moa out of a 16" barrel? At what distance? I do. 16" carbine barrel. 1:9 twist. CMMG WASP (melonite). 1 MOA. Surprised me. Yes 1" at 100 yards. Regularly. Here's a recent one sighting in a new scope. Last shot was called wide right and opened up a 3/4" five shot group to 1.185". My bad, not the rifle or ammo. M855 group 16 inch carbine 1:9 |
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There are too many variables here.
1. What optic? What reticle and what power was it set on? 2. M855 isn't match nor is it normally 1moa I.e 1/2" at 50yards. 3. Does the 55 gr stuff sow sets shoot left at 50 yards? Every time? 4. Was the barrel hot? 5. Plane shooter? Same position? What position? |
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Thanks for the feedback so far. The match ammo is 69 grains, while the bulk ammo is 55 grains. Barrel twist is 1:8. Well, twist is not the issue. Your LC is XM193 which should shoot fine from that barrel. If the group is tight, it's fine. Just don't expect 55 grain bullets to shoot anywhere close to the same point of impact as the 69 grain loads. As to accuracy, you should be making ragged holes with the match grade loads at 50 yards. Maybe you need to clean the barrel and try again. Maybe you need to practice cheek weld and trigger pull. Or if you have a gritty, long, heavy trigger you might shrink the groups with a good, smooth 2 stage trigger. My Geissele SSA-E cut my bench rest group size in half. |
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AAARRRGGGHH..... Bullet weight, twist rate, load... all of this makes no difference at all while the bullet is still in the bore. For those little micro seconds, the bullet is still integral to the gun, and the only movement going on is a bit of twisting or "whipping" of the barrel as the bullet is forced to spin.
Only at the point of the bullet leaving the muzzle does the rifle move appreciably, from recoil, and from the barrel "unwinding". You shouldn't be seeing that much shift in POI. I was curious about this with my own loads. I use a 55 gr. bulk PSP, a 60 gr. Hornady PSP, and the 65 gr. Sierra Game King. A 15 round group with 5 rounds each of these loads goes into 7" @ 200 yards, or 3.5 MOA. You shouldn't be far off from that. |
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I do. 16" carbine barrel. 1:9 twist. CMMG WASP (melonite). 1 MOA. Surprised me. Yes 1" at 100 yards. Regularly. Here's a recent one sighting in a new scope. Last shot was called wide right and opened up a 3/4" five shot group to 1.185". My bad, not the rifle or ammo. M855 group 16 inch carbine 1:9 Quoted:
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You shoot 855 moa out of a 16" barrel? At what distance? I do. 16" carbine barrel. 1:9 twist. CMMG WASP (melonite). 1 MOA. Surprised me. Yes 1" at 100 yards. Regularly. Here's a recent one sighting in a new scope. Last shot was called wide right and opened up a 3/4" five shot group to 1.185". My bad, not the rifle or ammo. M855 group 16 inch carbine 1:9 Why a link to Mazdaspeed Forum? No one is going to register just to see your prowess with 855 ammo. What groups do you get with match ammo? |
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Why a link to Mazdaspeed Forum? No one is going to register just to see your prowess with 855 ammo. What groups do you get with match ammo? Quoted:
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You shoot 855 moa out of a 16" barrel? At what distance? I do. 16" carbine barrel. 1:9 twist. CMMG WASP (melonite). 1 MOA. Surprised me. Yes 1" at 100 yards. Regularly. Here's a recent one sighting in a new scope. Last shot was called wide right and opened up a 3/4" five shot group to 1.185". My bad, not the rifle or ammo. M855 group 16 inch carbine 1:9 Why a link to Mazdaspeed Forum? No one is going to register just to see your prowess with 855 ammo. What groups do you get with match ammo? Do you have to register to see the pix? If so, my apology. Didn't realize that. I'll try to find another host site, since we can't directly post here. Performance Mazdas are also an interest of mine, and a lot of the guys there are currently deployed or recently deployed military and love both hot cars and weapons, so there is a section there for gun nuts. As to match ammo, I have a 1:9 barrel and can't shoot the heavy, higher BC stuff. I hand load and am working up some loads now based on the Sierra MatchKing 53 grain hollow point. I have a very small supply and finding it in stock anywhere is a bit of a challenge. My load development is a work in progress, but shows good potential with .90" groups at 100 yards using match primers and 25.5 grains of H4895 in LC cases and no crimp. Case overall length is 2.190". I think I can get the groups down to 3/4 MOA with a slight reduction in charge weight and more exacting case prep and maybe increasing COL a bit. But, I'm not trying to make a 16" carbine into a target rifle. I am curious as to where the limits of the barrel may be. Consistent 3/4 MOA may be it. I'm finding that I can do almost as good as the stunning and unexpected groups with "green tip" when using a pure hunting bullet - the Barnes TSX 53 grain hollow point, which is what this load development is really all about - coyotes and small deer out to 300 yards. I'm seeing just over I MOA with the same powder charge and those Barnes bullets. My M193 Clone loads using Hornady 55 grain FMB-BT bullets are, so far, not as accurate as the XM855, typically averaging 1.5" at 100 yards.. Go figure. |
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Did you go back n' forth with ammo, or shoot the 69 gr then the LC and stop? Almost looks like your scope shifted. This ^ is a plausible explanation of both the larger than expected match groups and then a worsening with the LC ammo, if the match groups were shot first, then followed by the LC. Maybe ring screws loosening or mount moving? OP: can you now shoot the match ammo in the same general group size, or have those groups exploded out to the same size as the LC group? |
| For free image hosting, I use photobucket. Works pretty well and no hassle.On the original poster's accuracy problem. I have to ask, how much time do you have using a scope? Did you keep a consistent cheek weld and fire a group of 2 or 3 shots before changing the cheek weld? Are you focusing on the crosshair or target? These can all cause wandering groups. The focus point one is the most vexing. You think everything is on target and you break your shot. The find the impact was not in the expected area. In fact, the rounds usually circle the bullseye when you focus on the target. We used to call it "Chasing the bull" Scopes seem self evident. But are a learned skill. |
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