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Discussion Starter · #1 · (Edited)
My BAR10 with the TDC hop adjuster and shimmed chamber is curving right. This is kinda strange, since the TDC mod should be fixing all problems with curving. This problem is recent, the rifle used to shooting perfectly, and I don't remember anything I could have done to cause the problem.

The weird thing is, I can see that the bucking nub (the part that contacts the BB) is very even/symmetrical when pressure is applied to the hopup arm with the TDC adjuster screw. The fangs on the hopup arm are also even and symmetrical. Also, my barrel looks pristine and I have cleaned it already.

I also suspected the bucking, but it did not look torn at all when I inspected it. I've already tried washing the bucking in soap + warm water. This problem is really stumping me, any ideas?
 

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So it started curving after you did the TDC mod? Make sure you have the hole centered over the hop arm. It shouldn't matter too much if the screw is at an angle but if it is off center it might not be keeping even pressure on your bucking. It shouldn't mAtter if you use really heavy bbs. I use .3s and it shoots fine for me.
 

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Discussion Starter · #6 ·
So it started curving after you did the TDC mod? Make sure you have the hole centered over the hop arm. It shouldn't matter too much if the screw is at an angle but if it is off center it might not be keeping even pressure on your bucking. It shouldn't mAtter if you use really heavy bbs. I use .3s and it shoots fine for me.
After I did the TDC mod it shot very straight for a good while and then started curving, so TDC alone isn't the problem. Whats confusing me is that the hop up arm seems to be applying even pressure to the bucking.
 

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What hop up unit do you have? If its a PDI then you have to make sure your pressure is even. I'm tempted to JB weld the arms together.. getting sick of adjusting three screws.
 

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Discussion Starter · #9 · (Edited)
I have a stock BAR10 chamber, and my bucking is aligned. I just found out that the dental floss mod had something to do with this, so I undid the floss and it shoots somewhat better, but still not as good as before. I'll try to find out a bit more, although my compression is really bad now because of blowby (no more floss to keep the bucking tight around the cylinder head nozzle).

The pressure exerted on the bucking contact nub stil looks even.
 

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Yeah, that's what I was thinking, or maybe the knot is applying more pressure to a certain point of the bucking. :/

Could always try wrapping it in something else, like PTFE (teflon) tape?

Another suggestion would be copper rings (like Noobie's ABB rings) that secure the bucking. I don't know if this user is still selling them, but you could give him a try: http://www.airsoftsniperforum.com/showthread.php?t=5040
 

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Discussion Starter · #13 ·
I want those ABB rings so bad. Teflon tape is a bit too wide, but I guess it could work if I cut them into thin strips. Another thing I could do is sand away the nub of the bucking and re-apply dental floss. Oh yea, after I un-did the dental floss the rifle started to curve LEFT instead of right, so I sanded down the right hopup arm fang and now it's shooting straight, although the BB's don't go quite as far because of the big loss in compression. It's only a slight difference though. I used to be able to hit 250' but now it's more like 230'.
 

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Could always try making the rings out of shell casings! I don't know what size you need but I know that many people have made them out of cutting shell casings.

You have good range, but it would be good to get that extra 20 feet!
 

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Discussion Starter · #15 ·
Could always try making the rings out of shell casings! I don't know what size you need but I know that many people have made them out of cutting shell casings.

You have good range, but it would be good to get that extra 20 feet!
Haha, I just found out that 9mm shell casings fit PERFECTLY around the bucking!!!! My attempt to cut the casing with a pair of scissors failed miserably though :O Noobie probably goes to the shooting range, burns through some 9mm ammo, then picks the shells off the ground, cuts them up and sells them :p
 

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Discussion Starter · #17 · (Edited)
I wish I had a hacksaw... Anyways, I'm angry again because my BAR10 is shooting really inconsistently again right now, the BB's are going anywhere but straight. I'm a bit puzzled, but I think it has to do with the bucking.

Edit: Fixed. My shims were incorrectly aligning the arm.
 

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Discussion Starter · #18 ·
Ugh... it turns out that I didn't actually fix the problem!!! Today I found out that when first put the rifle back together after aligning the shims, the rifle shot very straight. However, after a few shots, the BBs started to curve LEFT! This is really mystifying me because whenever I align the hopup and put the rifle back together, it will shoot perfect for a few shots and will then start to curve again after a few rounds. I've repeated this phenomenon more than once.
 

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Discussion Starter · #20 ·
Could it possibly be caused from a slight bend or a scratch in your barrel? :S
I cleaned my barrel, and it doesn't seem to be bent or scratched. The part that really confuses me is that my rifle fires perfectly straight for the first few shots (after I put my gun back together) and then starts to curve after 6-7 shots, and the curving gets worse as I fire more shots.
 
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