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Posted: 9/10/2014 8:25:23 PM EDT
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My rifle is a 16" cmmg, I had an old bushnell 3-9x40 scope, and the factory collapsable stock, and at 75 yards it would cut a ragged 1/2" hole, with all different types of ammo and consistently ring a 2" steel target at 130 yards. I changed the scope to a nikon prostaff mildot 3.5-14x40, and a magpul fixed rifle stock, and accuracy went to crap. Now at 75 it may have 3 holes touching, then the rest will be all over the place, then it will go back to shooting good, then to crap again. Do you think I'm looking at probably a bad scope, or would the stock have anything to do with it? I've tried different ammo with the same results. My buddy suggested getting some match ammo, and shooting some, if it's all over the place, swap scopes and see what happens, and then the stock if it still doesn't straighten up. Just trying to get some info before I start swapping parts.
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Did you change ammo or buy a new batch? Ammo is the bottom line regarding accuracy, especially at longer ranges. Standard production rifles will usually shoot impressively well with Sierra Match Kings of any weight provided they have a fast enough twist.
I spend a lot of time shooting from a bench. It's much harder and more complicated to shoot consistently well than most people realize. Everything you do must be repeated precisely with each shot or you'll get fliers. The rifle must sit in the bags in perfect alignment with the target and this can't change from shot to shot. If you have to apply pressure or steer the rifle in the bags to align the crosshairs you'll throw shots from the group. The trigger must be squeezed the same way each shot and held to the rear throughout the recoil process. I shot a tournament early this year and had a horrible outing. It was fired at 200 meters rather than 200 yards and the sun was rising directly behind the targets making it hard to see anything. On the way home I had to drive past my home club so I stopped to confirm zeroes. With a couple of clicks I re-zeroed at 200 yards and shot a 1.2" five shot group threw the center of the X ring. Conditions can make things go south. It was probably 40 degrees that morning which didn't help. Practice sessions that aren't hurried will help immensely, take your time to get it right. Double check to insure every scope ring and mount is tight. |
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Quoted:
My rifle is a 16" cmmg, I had an old bushnell 3-9x40 scope, and the factory collapsable stock, and at 75 yards it would cut a ragged 1/2" hole, with all different types of ammo and consistently ring a 2" steel target at 130 yards. I changed the scope to a nikon prostaff mildot 3.5-14x40, and a magpul fixed rifle stock, and accuracy went to crap. Now at 75 it may have 3 holes touching, then the rest will be all over the place, then it will go back to shooting good, then to crap again. Do you think I'm looking at probably a bad scope, or would the stock have anything to do with it? I've tried different ammo with the same results. My buddy suggested getting some match ammo, and shooting some, if it's all over the place, swap scopes and see what happens, and then the stock if it still doesn't straighten up. Just trying to get some info before I start swapping parts. If all you have changed is the scope................................ May not be mounted properly. May be a faulty optic. Stock won't make one bit of difference provided you can still get a good and consistent cheek weld. |
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Check the mount first.
Second, have you adjusted the focus on the optic to your eyes? Do you have a consistent cheek weld shot to shot, or are you having to move your head about as you are shooting? I would be looking at my eye ball position behind the scope. The eye box of the scope might be smaller then your previous scope. This would explain the inconsistent groups. |
| Your cheek weld may have changed due to the new stock and/or you have a defective sight. Try it with your previous stock and see what happens. In the future, I would suggest changing one thing at a time to reduce the number of variables so that when these issues occure you can quickly and simply identify them. |
| It's the same mounts as I was using before, nikon p-223 mounts, they're tight on the upper, and my buddy lapped them today, that didn't help either. I'll try the other stock to see if it's a cheek weld issue, but as far as the ammo goes, I'm shooting the same stuff as I was before with the other scope when it was shooting great. |
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Quoted: Had a similar problem with a red dot on an AK...rounds were going everywhere and finally figured out the dot was moving internally with each shot. Good luck! There's your problem.  OP, like others said, check the mounting. Is the 3-shot - then elsewhere repeatable and does it follow the same direction? The stock shouldn't affect anything unless it has a wiggle to it. Edit: perhaps you fired a different lot of ammo? |
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1. Clean the barrel. Then fire one fouling shot. Then shoot for groups from good rifle rest or sandbags using uniform technique.
2. If problem persists check for scope creep in the rings. Mark the tube against the rings with a lead pencil. Shoot and check to see if the marks have moved. Make sure you push each ring forward in the Picatinney rail slot before tightening it down. That provides a secure shoulder against the cross bolt. 3. If scope is secure in the mounts, you have a bad scope. I seriously doubt the stock switch has anything to do with this. |
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Had a similar problem twice on 2 different rifles. On the first when tightening the clamp onto the rail I had somehow allowed the moving part to slip slightly off the rail. This allowed the front mount to shift ever so slightly, thus mobing my poi a few inches with each shot. I chased that damned last hole for 45 min before finally having the bulb go on and think "sumpin ain't raiiitt!" When I loosened that front mount the faux pas became obvious. Retightened it and holes started touching just like a custom built bolt gun should.
The second incident occurred after the first. Because it acted almost exactly the same I treated it the same. Reloosened the rings and retightened them... several times. Problem never changed. POI would move after every shot and there was no pattern to it. I was beginning to think I'd had way too much coffee that morning. Weeks later I mounted a different scope I'd had for a while (and knew to be good) and it's shooting 1.25" patterns, just like an original Brit .303 Sniper should. Come forward over a year and I run into the manufacturer of that scope, and proceed to tell him of my troubles. He then asks "was that the such and such model with the blah blah blah features?" I was like, "yeah, exactly." He responds with "That thing was a POS. Our plant had some major QC probs with that model so we fired the guy running the plant and went over the QC, only to find out there had been none." He handed me a catalog and said "pick a few things out, I want to make this right for you." I did, and he came through. Stuff I got from him was just fine. |
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Quoted:
My rifle is a 16" cmmg, I had an old bushnell 3-9x40 scope, and the factory collapsable stock, and at 75 yards it would cut a ragged 1/2" hole, with all different types of ammo and consistently ring a 2" steel target at 130 yards. I changed the scope to a nikon prostaff mildot 3.5-14x40, and a magpul fixed rifle stock, and accuracy went to crap. Now at 75 it may have 3 holes touching, then the rest will be all over the place, then it will go back to shooting good, then to crap again. Do you think I'm looking at probably a bad scope, or would the stock have anything to do with it? I've tried different ammo with the same results. My buddy suggested getting some match ammo, and shooting some, if it's all over the place, swap scopes and see what happens, and then the stock if it still doesn't straighten up. Just trying to get some info before I start swapping parts. + another on scope mount, have seen it often...sometimes the scope can get bound up in the mount...even if is looks good and straight, it might be bound. First thing I would do is completely loosen the scope attachments that attach to the tube of the scope, and then retighten screws in a pattern of opposing screws. Get the screws tight, but don't over torque....they are typically small screws with tight threads...so its easy to apply more torque than you realize (if you have access to torque screw devise all the better) Resist the urge to grab hex key or screw driver with both hands to give it that little extra...it doesn't need it. Tighten but don't over tighten. Then I would do the same thing on the mounts that attach to the rifle, and see that fixes it. If that doesn't clear it up...then go back to old scope and see if the problem corrects itself. It's not the stock imo. Should also add ....use the same ammo while diagnosing to take that variable out. shoot at least 10 shots and measure to compare before/after. |
| Went back and changed everything to the way it was when it was shooting great, still the same results, I'll have a few holes touching, then flyers, I'm at the end of my patience with this thing.I'm going to check the barrel nut tomorrow, I don't have a tool, but I can't move it by hand at all, so it's not real loose if it's loose, besides the gas tube would keep it from backing off anyway. |
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Forgot to mention also, it wasn't the scope. I put it on a remington 700 aac-sd I picked up friday, and it's shooting one hole groups at 100 yards. Off topic but, what ammo and how many shots for this one ragged hole group with the Rem700 AAC? I had one but, sold it because I could not get better groups than I could with my OBR and SR25 using facotry match ammo. I have two friends that own AAC's and could use some suggestions for ammo since they're both faily new to precision shooting. |
| OP if you say it isn't the scope look at the crown/muzzle area for damage, flash hider to ensure it is tight and barrel nut to ensure all is good to go. If the aforementioned are good to go I would then look to ensure you are mounting the optic in the same slot on the receiver, ensuring it is secure and take it from there. I hope this helps bro. |
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Quoted:
Off topic but, what ammo and how many shots for this one ragged hole group with the Rem700 AAC? I had one but, sold it because I could not get better groups than I could with my OBR and SR25 using facotry match ammo. I have two friends that own AAC's and could use some suggestions for ammo since they're both faily new to precision shooting. Quoted:
Quoted:
Forgot to mention also, it wasn't the scope. I put it on a remington 700 aac-sd I picked up friday, and it's shooting one hole groups at 100 yards. Off topic but, what ammo and how many shots for this one ragged hole group with the Rem700 AAC? I had one but, sold it because I could not get better groups than I could with my OBR and SR25 using facotry match ammo. I have two friends that own AAC's and could use some suggestions for ammo since they're both faily new to precision shooting. 168gr gold medal match, mag full, 4 shots. |
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OP if you say it isn't the scope look at the crown/muzzle area for damage, flash hider to ensure it is tight and barrel nut to ensure all is good to go. If the aforementioned are good to go I would then look to ensure you are mounting the optic in the same slot on the receiver, ensuring it is secure and take it from there. I hope this helps bro. The flash hider is tight, smith vortex eliminator, instructions said to tighten hand tight, and it tightens as you shoot, which it does, can't break it loose by hand. I'm going to hit the barrel nut tomorrow, my buddy has a wrench at his shop, but wouldn't the gas tube keep the nut from backing off? Or would it just let it loosen just enough to affect it |
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Quoted:
The flash hider is tight, smith vortex eliminator, instructions said to tighten hand tight, and it tightens as you shoot, which it does, can't break it loose by hand. I'm going to hit the barrel nut tomorrow, my buddy has a wrench at his shop, but wouldn't the gas tube keep the nut from backing off? Or would it just let it loosen just enough to affect it Quoted:
Quoted:
OP if you say it isn't the scope look at the crown/muzzle area for damage, flash hider to ensure it is tight and barrel nut to ensure all is good to go. If the aforementioned are good to go I would then look to ensure you are mounting the optic in the same slot on the receiver, ensuring it is secure and take it from there. I hope this helps bro. The flash hider is tight, smith vortex eliminator, instructions said to tighten hand tight, and it tightens as you shoot, which it does, can't break it loose by hand. I'm going to hit the barrel nut tomorrow, my buddy has a wrench at his shop, but wouldn't the gas tube keep the nut from backing off? Or would it just let it loosen just enough to affect it I don't think the barrel nut can back off enough due to the gas tube to effect accuracy. Hopefully someone here more knowledgeable than I can chime in on this. |
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Quoted: I don't think the barrel nut can back off enough due to the gas tube to effect accuracy. Hopefully someone here more knowledgeable than I can chime in on this. Quoted: Quoted: Quoted: OP if you say it isn't the scope look at the crown/muzzle area for damage, flash hider to ensure it is tight and barrel nut to ensure all is good to go. If the aforementioned are good to go I would then look to ensure you are mounting the optic in the same slot on the receiver, ensuring it is secure and take it from there. I hope this helps bro. The flash hider is tight, smith vortex eliminator, instructions said to tighten hand tight, and it tightens as you shoot, which it does, can't break it loose by hand. I'm going to hit the barrel nut tomorrow, my buddy has a wrench at his shop, but wouldn't the gas tube keep the nut from backing off? Or would it just let it loosen just enough to affect it I don't think the barrel nut can back off enough due to the gas tube to effect accuracy. Hopefully someone here more knowledgeable than I can chime in on this. Last year, one of our SR Junior girls started getting erratic scores. Turned out to be a loose barrel nut. If you only need the minimum lbs/ft to line up the tube, the nut doesn't need to move much to be loose. |
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