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Posted: 3/30/2010 6:25:30 AM EDT
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Yesterday while shooting my rifle I noticed that switching from 55 gr ammo to 62 and also some matchking serrias the POI changed drasticly .
We were only shooting at 35 yards and the differance between the 55 gr groups and the heavier bullets was about two inches . Nice groups in all cases but the heavies land 2 inches to the right of the 55 gr . 
Any suggestions ? I have access to a free float tube and new barrel . I heard that the Colt barrels have been suspect ,but since the groups are ok , abeit differantly . Thanks Rocklock |
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Different ammo's, different POI's.
It's normal and barrel harmonics at work, hence as the shot is moving down the bore, the barrel/muzzle whips in a oblong circle and the bullet leaves the muzzle at some point in the muzzle movement. Power type, bullet type, and even primer type will change the exit point of the bullet, and the reason that you are seeing changes in impact between the two ammos. As for hand loading and fine turning the loads for such, you want to the bullet to leave the muzzle at either one of the end points of the oblong circle (when the muzzle is the stillest), so not only are you trying to have the bullet leave during such, but the devation of the loads as close to zero as well so the all leave the muzzle in the same muzzle whip placement. And yes, even on bull barrels, you still have barrel whip (just to less of a degree), but you are still hand load tuning for such as well. |
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Your barrel nut may be a tad loose and the barrel reacting a bit more out of the norm, but yes with the different POI for different ammo's.
I get about 3" @100 yards on a few of my thick barrel rigs by just going from M-193 to 62gr poly wolf, and the funny thing, and on one, it's the 62 grain that is printing higher and to the left. It all comes down to how much area the muzzle is covering when it going into whip/harmonics, and at what point the muzzle is in the whip that the bullet leaves the muzzle. |
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well it bugged me enough that I put on a heavy flutted Bushy barrel 1/9 and a free floated handgaurd . I'll let you know .
I have a question for you ? as the M4 that the goverment uses has a 14" tube and heavier profile than the 16" civy versions . it could be the odd taperings do 'something to it ? Thanks Gary |
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I finaly got out to test my new barrel and free float handgaurd .
It made all the differance ! With the fluted buchmaster tube and free float hand gaurd all bullet weights went to the same POI (55 fmj , Wolf 55 , and Wolf 62 grains Hp . ) Plus a 1" group for bragging 
I'm a believer ....Colt barrels......suck . 
Thanks Gary |
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Quoted:
I finaly got out to test my new barrel and free float handgaurd . It made all the differance ! With the fluted buchmaster tube and free float hand gaurd all bullet weights went to the same POI (55 fmj , Wolf 55 , and Wolf 62 grains Hp . ) Plus a 1" group for bragging
I'm a believer ....Colt barrels......suck .
Thanks Gary Slow down there big guy... I bet if you put a free float tube and checked the torque with the original barrel, you'd get the same result. You can't change multiple variables and then whole-heartedly blame it on just one of those variables. As stated above, POI has mostly to do with harmonics. Free float a barrel, and harmonics change drastically. IM me if you want to get rid of that crappy barrel  ...
- AG |
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Nah I hang onto the crappy ol m-4 tube .
That Colt remark was mostly an inside joke , as my freinds have been after me to switch it for a year or so ,they are diehard Colt haters . I was throwing them a bone .
That would have made for an interesting experiment free float the M4 tube then switch and try the new tube ...? Its been hard for me to warm up to the M4 , The old A1 fits well , feels right , something about Parris Island can do that to a man . 
Gary |
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I thought both the Bushmaster and Colt barrels are made by ER Shaw. |
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Quoted:
I thought both the Bushmaster and Colt barrels are made by ER Shaw. Use only as a reference for profile of a barrel. |
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