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Posted: 12/9/2018 12:00:58 PM EDT
I was sighting in my PSA 10.5” pistol yesterday (1/7 556 barrel). I started out with some 223 Federal Power Shock 55gr to get on paper. Ultimately, I wanted to end up with the gun zeroed for Barnes Vor-TX 70gr.
The Federal was grouping ok at 50 so I switched over. The point of impact shifted about 3” higher. The Barnes was grouping really well so I switched to the 100 yard target. Shot three awesome groups with Barnes, and then thought I’d see what the 223 Federal would do this time. Again, 3-4 inches. The extra 50 yards didn’t seem to matter. To me, that shift seems dramatic even when going between brands, bummer size, caliber, etc. I have a 223 Wylde upper coming tomorrow and am curious if that will change the size of the shift at all because of the Wylde chamber. Any thoughts? Here are the 100 yard Barnes groups BTW. Very pleased. 
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Posted: 12/9/2018 12:18:44 PM EDT
[#1]
Am I seeing keyholes?
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Posted: 12/9/2018 12:25:48 PM EDT
[#2]
Quote HistoryQuoted:
Am I seeing keyholes? |
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Posted: 12/9/2018 12:34:32 PM EDT
[#3]
Is the barrel free floated ?
When I bought my 6920 Colt it would shoot nice little groups at 25 yds ,but about 4 inches apart from each other when using 55 gr. and 62 gr. bullets . Once I put on a free floated barrel the issue was solved . IF you are only shooting one bullet wieght then it wouldn't make any differance . |
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Posted: 12/9/2018 1:13:27 PM EDT
[#4]
This is the upper: PSA Upper
It’s funny some of you mentioned keyholing. When I first switched to the 70gr and was looking through the spotting scope, I thought it might have been doing that because the holes seemed slightly bigger. But then I thought maybe it was just a hotter round and that caused the target to react differently because the groups were so tight...idk. The target is stapled to a big piece of rubber basically. Those group pictures are all rounds from the same box of bullets. What are the odds that some rounds would key hole and others wouldn’t, plus the groups stayed tight? I usually associate keyholing with something like this: https://www.hkpro.com/forum/attachments/hk416-hk417-hq/193977d1524437089-my-new-mr556a1-has-bad-keyhole-issues-dsg_1594.jpg |
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Posted: 12/9/2018 2:09:53 PM EDT
[#5]
The poi shift is normal. It's caused by the greater recoil of the heavier bullet; the muzzle rises a tad higher, causing the bullet to release at a higher angle.
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Posted: 12/9/2018 2:29:56 PM EDT
[#6]
I'm not sure I fully understand this question. I'm going to assume it is a very fundamental question about bullet drop and not something else that I'm missing.
So you zero'd your rifle to a 55g out of a 10" barrel. You're zeroing at 50 yards with a ballistic co-efficient of .222. Since it's a shorter barrel, I'm going to guessimate that your FPS is going at 2700 (it's rated to go 3200 fps but that is probably out of a 20" barrel but I cannot find such info on their website. With the TX round, it is a 70g projectile loaded to 5.56mm spec so it is coming out a little hotter and with a co-efficient of .314. It's rated to 3200 fps but since it's out of a 10 inch barrel, I'm assuming it is going to go a little faster than the Federal .223, so I'll put it at about 2900 fps. Now with those data, you can easily see why it is shooting a little higher. This graph is assuming you zero'd both rifles at 50 yards with the load. Since you zero'd it only with a 55gr, you're going a little higher. 
So if you zeroed with a 55gr and want to shoot the 70gr, you'll need to aim a little lower at 50 yards, but a little higher under 50 yards. |
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Posted: 12/9/2018 2:57:57 PM EDT
[#7]
newp.
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Posted: 12/9/2018 3:37:04 PM EDT
[#8]
Quote HistoryQuoted:
The poi shift is normal. It's caused by the greater recoil of the heavier bullet; the muzzle rises a tad higher, causing the bullet to release at a higher angle. |
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Posted: 12/9/2018 3:52:59 PM EDT
[#9]
Quote HistoryQuoted:
I'm not sure I fully understand this question. I'm going to assume it is a very fundamental question about bullet drop and not something else that I'm missing. So you zero'd your rifle to a 55g out of a 10" barrel. You're zeroing at 50 yards with a ballistic co-efficient of .222. Since it's a shorter barrel, I'm going to guessimate that your FPS is going at 2700 (it's rated to go 3200 fps but that is probably out of a 20" barrel but I cannot find such info on their website. With the TX round, it is a 70g projectile loaded to 5.56mm spec so it is coming out a little hotter and with a co-efficient of .314. It's rated to 3200 fps but since it's out of a 10 inch barrel, I'm assuming it is going to go a little faster than the Federal .223, so I'll put it at about 2900 fps. Now with those data, you can easily see why it is shooting a little higher. This graph is assuming you zero'd both rifles at 50 yards with the load. Since you zero'd it only with a 55gr, you're going a little higher. https://i.imgur.com/fUXN3NH.png So if you zeroed with a 55gr and want to shoot the 70gr, you'll need to aim a little lower at 50 yards, but a little higher under 50 yards. |
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Posted: 12/9/2018 4:09:48 PM EDT
[#10]
Quote HistoryQuoted: I appreciate the info but that chart shows the two rounds intersecting at 50yards and a total difference at a 100 of less than an inch. I was seeing 3-4 inch differences with the 55gr shooting LOWER than the 70gr. ...though there is pressure differences to account for. The graph shows if you zero'd BOTH at 50 yards. You did not. The graph is to illustrate the 70gr is going at a higher POI than your 55gr so it would explain why you were off. Hope that helps. My thought: don't zero with a different round. Try to zero with a similar round if possible to get "on target" then you use fewer rounds of the more expensive stuff to fine tune it. You're shooting two wildly different rounds. |
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Posted: 12/9/2018 6:48:58 PM EDT
[#11]
Quote HistoryQuoted:
What? Please explain. David Quote HistoryQuoted:
Quoted:
The poi shift is normal. It's caused by the greater recoil of the heavier bullet; the muzzle rises a tad higher, causing the bullet to release at a higher angle. |
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Posted: 12/9/2018 7:20:06 PM EDT
[#12]
POI shift between ammo is completely normal, and is caused by both velocity/weight differences (something that would be reflected in the graph above), as well as differences in the individual harmonics of the barrel (something not reflected in the graph above). Also, it seems like the copper composition of Barnes bullets, and the density differences therein, can often compound the problem. It’s not a big deal, but it’s why you’ll want to zero with a specific load and/or know the different POI with different loads.
More importantly, are those rounds keyholing? Or are those impacts just very coincidentally in the shape of keyholes? |
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Posted: 12/9/2018 9:40:33 PM EDT
[#13]
Quote HistoryQuoted:
POI shift between ammo is completely normal, and is caused by both velocity/weight differences (something that would be reflected in the graph above), as well as differences in the individual harmonics of the barrel (something not reflected in the graph above). Also, it seems like the copper composition of Barnes bullets, and the density differences therein, can often compound the problem. It’s not a big deal, but it’s why you’ll want to zero with a specific load and/or know the different POI with different loads. More importantly, are those rounds keyholing? Or are those impacts just very coincidentally in the shape of keyholes? I wouldn’t think the bullet weight would be an issue with a 1/7 barrel, even if it is only 10.5”. 25-30 55gr Wolf and Power Shoks were all clean holes (different target). Think it is the ammo or barrel? It’s brand new btw. |
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Posted: 12/9/2018 10:09:48 PM EDT
[#14]
I see a keyhole at 4:00 on 1st target, and 11:00 on 3rd target. I wonder what the twist actually is: https://www.ar15.com/forums/ar-15/How-much-tolerance-in-twist-rate-Measure-yours-please-/12-720559/
What is your benchrest setup? |
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Posted: 12/9/2018 10:31:06 PM EDT
[#15]
Quote HistoryQuoted:
I see a keyhole at 4:00 on 1st target, and 11:00 on 3rd target. I wonder what the twist actually is: https://www.ar15.com/forums/ar-15/How-much-tolerance-in-twist-rate-Measure-yours-please-/12-720559/ What is your benchrest setup? I use Caldwell shooting bags set on a concrete table. Not the absolute best setup available but it is very stable. |
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Posted: 12/9/2018 10:51:25 PM EDT
[#16]
It's the difference in bullet weight and velocity combined with the short barrel, is my guess.
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Posted: 12/9/2018 10:58:11 PM EDT
[#17]
Quote HistoryQuoted:
1/7 10.5 barrel. Here's the link: PSA Upper I use Caldwell shooting bags set on a concrete table. Not the absolute best setup available but it is very stable. I'll agree with Aero on the recoil impulse. Relevant visual demonstration:  Why Do Revolver Barrels Point Downwards? Keep in mind, 1 MOA is about 0.005" movement at the rifle. |
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Posted: 12/9/2018 11:19:21 PM EDT
[#18]
Stability is a function primarily of bullet length, velocity, and bullet twist. Longer bullets need tighter twist and higher velocity to stabilize.
The Barnes 70 TSX bullet is solid copper. That makes it much longer than a comparable lead core bullet. It's as long as a 77 grain OTM. It takes at least a 1:8 twist in 16" barrel to avoid keyholing. 70 TSX loaded to full power 5.56 keyhole badly in my 1:9 barrel, but shoot close to MOA in 1:8. Whacking off 6" from the barrel will reduce velocity significantly. Enough drop in velocity will eventually destabilize the bullet, even in 1:7, and many 1:7 barrels are not true 1:7. Often they check out on the slow side. Even so, with a BC of .314, length 1.036", Berger's twist calculator suggests that 1:7 can stabilize it in that pistol barrel even at as low as only 2,000 fps. I doubt twist is a problem if the barrel is actually 1:7. http://www.bergerbullets.com/twist-rate-calculator/ Stability aside, barrel harmonics will be significantly different with those different loads. Harmonics, alone, can cause that much POI shift. |
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Posted: 12/10/2018 12:44:02 AM EDT
[#19]
Quote HistoryQuoted:
The poi shift is normal. It's caused by the greater recoil of the heavier bullet; the muzzle rises a tad higher, causing the bullet to release at a higher angle. |
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Posted: 12/10/2018 9:25:00 AM EDT
[#20]
Quote HistoryQuoted:
Stability is a function primarily of bullet length, velocity, and bullet twist. Longer bullets need tighter twist and higher velocity to stabilize. The Barnes 70 TSX bullet is solid copper. That makes it much longer than a comparable lead core bullet. It's as long as a 77 grain OTM. It takes at least a 1:8 twist in 16" barrel to avoid keyholing. 70 TSX loaded to full power 5.56 keyhole badly in my 1:9 barrel, but shoot close to MOA in 1:8. Whacking off 6" from the barrel will reduce velocity significantly. Enough drop in velocity will eventually destabilize the bullet, even in 1:7, and many 1:7 barrels are not true 1:7. Often they check out on the slow side. Even so, with a BC of .314, length 1.036", Berger's twist calculator suggests that 1:7 can stabilize it in that pistol barrel even at as low as only 2,000 fps. I doubt twist is a problem if the barrel is actually 1:7. http://www.bergerbullets.com/twist-rate-calculator/ Stability aside, barrel harmonics will be significantly different with those different loads. Harmonics, alone, can cause that much POI shift. I ordered some more traditional lead core bullets yesterday in the 75gr range and TSX in 62gr. Will see if that makes a difference. I also have an 18” upper coming tomorrow so I will see what that does with these 70gr TSXs. It kinda sucks how few 556 hunting rounds there are without reloading. Everything is 223. Seems like almost everything is tipped with match rounds like the matchking that aren’t for hunting...at least not medium sized game. |
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Posted: 12/10/2018 9:57:42 AM EDT
[#21]
Quote HistoryQuoted:
Stability is a function primarily of bullet length, velocity, and bullet twist. Longer bullets need tighter twist and higher velocity to stabilize. The Barnes 70 TSX bullet is solid copper. That makes it much longer than a comparable lead core bullet. It's as long as a 77 grain OTM. It takes at least a 1:8 twist in 16" barrel to avoid keyholing. 70 TSX loaded to full power 5.56 keyhole badly in my 1:9 barrel, but shoot close to MOA in 1:8. Whacking off 6" from the barrel will reduce velocity significantly. Enough drop in velocity will eventually destabilize the bullet, even in 1:7, and many 1:7 barrels are not true 1:7. Often they check out on the slow side. Even so, with a BC of .314, length 1.036", Berger's twist calculator suggests that 1:7 can stabilize it in that pistol barrel even at as low as only 2,000 fps. I doubt twist is a problem if the barrel is actually 1:7. http://www.bergerbullets.com/twist-rate-calculator/ Stability aside, barrel harmonics will be significantly different with those different loads. Harmonics, alone, can cause that much POI shift. |
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Posted: 12/10/2018 10:51:57 AM EDT
[#22]
Quote HistoryQuoted: Is it correct to assume that shorter barrels will put less spin on the bullet because they have less time in contact with it or does it not matter? For example, a 10” 1/7 barrel cannot spin as much as a 16” 1/7? Bullet leaves a 16 inch barrel at 2000 fps will have less spin than a bullet leaving the same barrel at 3000 fps. Ergo those heavy loads may not have enough barrel to stabilize. MS556 may have hit the nail on the head. Furthermore, the barrel harmonics are also an issue. Barrels flex due to the immense pressure contained in the bore. This pressure gradiant (from 50k psi to atmosphere) plus the twist rate and bullet weight all contribute to this flex (harmonics) which would explain why load 1 hits high and right while load 2 is zero'd. |
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Posted: 12/10/2018 11:30:59 AM EDT
[#23]
Quote HistoryQuoted:
Is it correct to assume that shorter barrels will put less spin on the bullet because they have less time in contact with it or does it not matter? For example, a 10” 1/7 barrel cannot spin as much as a 16” 1/7? I ordered some more traditional lead core bullets yesterday in the 75gr range and TSX in 62gr. Will see if that makes a difference. I also have an 18” upper coming tomorrow so I will see what that does with these 70gr TSXs. It kinda sucks how few 556 hunting rounds there are without reloading. Everything is 223. Seems like almost everything is tipped with match rounds like the matchking that aren’t for hunting...at least not medium sized game. Quote HistoryQuoted:
Quoted:
Stability is a function primarily of bullet length, velocity, and bullet twist. Longer bullets need tighter twist and higher velocity to stabilize. The Barnes 70 TSX bullet is solid copper. That makes it much longer than a comparable lead core bullet. It's as long as a 77 grain OTM. It takes at least a 1:8 twist in 16" barrel to avoid keyholing. 70 TSX loaded to full power 5.56 keyhole badly in my 1:9 barrel, but shoot close to MOA in 1:8. Whacking off 6" from the barrel will reduce velocity significantly. Enough drop in velocity will eventually destabilize the bullet, even in 1:7, and many 1:7 barrels are not true 1:7. Often they check out on the slow side. Even so, with a BC of .314, length 1.036", Berger's twist calculator suggests that 1:7 can stabilize it in that pistol barrel even at as low as only 2,000 fps. I doubt twist is a problem if the barrel is actually 1:7. http://www.bergerbullets.com/twist-rate-calculator/ Stability aside, barrel harmonics will be significantly different with those different loads. Harmonics, alone, can cause that much POI shift. I ordered some more traditional lead core bullets yesterday in the 75gr range and TSX in 62gr. Will see if that makes a difference. I also have an 18” upper coming tomorrow so I will see what that does with these 70gr TSXs. It kinda sucks how few 556 hunting rounds there are without reloading. Everything is 223. Seems like almost everything is tipped with match rounds like the matchking that aren’t for hunting...at least not medium sized game. Barrel vibration is not caused by pressure, it's caused by the impulse of the gunpowder burning plus the impact of the bullet into the rifling. Pressure is the motivating force. |
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Posted: 12/10/2018 11:42:31 AM EDT
[#24]
Quote HistoryQuoted:
The poi shift is normal. It's caused by the greater recoil of the heavier bullet; the muzzle rises a tad higher, causing the bullet to release at a higher angle. happen to me yesterday when checking my zeros with 55 & 69s 
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Posted: 12/10/2018 11:44:50 AM EDT
[#25]
Quote HistoryQuoted:
This is the answer. Completely normal. I first learned about it many years ago when I got my first rifle. Mine was a 16". Quote HistoryQuoted:
Quoted:
The poi shift is normal. It's caused by the greater recoil of the heavier bullet; the muzzle rises a tad higher, causing the bullet to release at a higher angle. Accept it and zero with the ammo you intend to use. |
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Posted: 12/10/2018 11:51:17 AM EDT
[#26]
I've had 2"+/- POI change on some rifles between two different brands of ammo, same weight bullet.
It's why I reload, and generally for a given rifle. Although I've got one reload that seems to have been generally accepted in about 80% of the AR's I've use it in. |
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Posted: 12/10/2018 1:30:22 PM EDT
[#27]
Quote HistoryQuoted:
For most of us, it's a waste of time to wonder "why?" Each barrel shoots different ammo differently. Differences in ammo, bullet weight or even different bullet styles of the same weight, may have different points of impact. Accept it and zero with the ammo you intend to use. |
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Posted: 12/10/2018 4:14:15 PM EDT
[#28]
I like barrels that do not show much of a shift between ammo. But it happens. Strangely enough, the two Colt barrels I had showed more shift than other makers I've had. There are so many variables and ammo being one of them. One time I was shooting some 75 grain, 55 grain and 45 grain ammo out of my Colt A2 at 25 meters and I think the 45 grainers showed at least a 3-4" shift from the others. But the 75 and 55 showed quite a bit too. At 25 meters only.
My Dad's M4gery and my Recce with heavier barrels show way less shift between any ammo I've put through them. I like that. One of the factors COULD be profile. My Colt A2 is a govt' profile and the other one I saw big shifts on was a LW 16" carbine barrel. Either way, it happens. People can argue about all the science behind why and lengths' and this and that and the kitchen sink, but any gun may show some shift. If you have one that shows no shift or little, you might want to keep that one. Especially if it shows good precision. |
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Posted: 12/10/2018 6:35:22 PM EDT
[#29]
Quote HistoryQuoted:
I like barrels that do not show much of a shift between ammo. But it happens. Strangely enough, the two Colt barrels I had showed more shift than other makers I've had. There are so many variables and ammo being one of them. One time I was shooting some 75 grain, 55 grain and 45 grain ammo out of my Colt A2 at 25 meters and I think the 45 grainers showed at least a 3-4" shift from the others. But the 75 and 55 showed quite a bit too. At 25 meters only. My Dad's M4gery and my Recce with heavier barrels show way less shift between any ammo I've put through them. I like that. One of the factors COULD be profile. My Colt A2 is a govt' profile and the other one I saw big shifts on was a LW 16" carbine barrel. Either way, it happens. People can argue about all the science behind why and lengths' and this and that and the kitchen sink, but any gun may show some shift. If you have one that shows no shift or little, you might want to keep that one. Especially if it shows good precision. edit, I'm gonna take my brake off and recheck(next month  ).
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Posted: 12/10/2018 9:31:46 PM EDT
[#30]
Quote HistoryQuoted:
… It kinda sucks how few 556 hunting rounds there are without reloading. Everything is 223. Seems like almost everything is tipped with match rounds like the matchking that aren’t for hunting...at least not medium sized game. You need to read and understand the differences in 5.56X45 and .223 Remington ammunition. The Ammo Oracle is the best place to start: Ammo Oracle In any case, if you believe that you have a chamber suitable for 5.56 ammunition, you can confidently shoot .223 Rem ammunition in the same barrel. If you are chasing 5.56X45 speed, stop, you're wasting your time hunting for a unicorn of "improvement". If you believe 100 to 200 fps of speed makes a Real World difference, you wouldn't be shooting tiny barrels and you should spend some time working through trajectory problems in a ballistics program. Hornady has a great program on line: https://www.hornady.com/team-hornady/ballistic-calculators/# |
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Posted: 12/10/2018 10:03:18 PM EDT
[#31]
Quote HistoryQuoted: I missed this earlier. You need to read and understand the differences in 5.56X45 and .223 Remington ammunition. The Ammo Oracle is the best place to start: Ammo Oracle In any case, if you believe that you have a chamber suitable for 5.56 ammunition, you can confidently shoot .223 Rem ammunition in the same barrel. If you are chasing 5.56X45 speed, stop, you're wasting your time hunting for a unicorn of "improvement". If you believe 100 to 200 fps of speed makes a Real World difference, you wouldn't be shooting tiny barrels and you should spend some time working through trajectory problems in a ballistics program. Hornady has a great program on line: https://www.hornady.com/team-hornady/ballistic-calculators/# However, my reason behind it is that where I live I can use an AR pistol for certain deer seasons and an extra 100-200 FPS, I believe, does make a difference in that application. Now, I know that AR pistols can have barrels longer than 10.5” and I actually have an 18” upper for that. However, that law is very poorly understood so when I hunt public land, I plan to use the short barrel so I don’t have to get in an arguement with a game warden, or worse, end up with a fat ticket I have to fight in court. I’ll be using the 18” on my own land and will probably stick with FUSION or the TSX assuming both shoot well out of that rifle. |
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Posted: 12/11/2018 10:41:40 AM EDT
[#32]
I zeroed in two of my 10.5’s and a 16 yesterday. Started out with 75 grain gold dots and then tried 55gr AE cheap shit and then metal case wolf.
Wasn’t anywhere near that much of a difference between bullets. Maybe half of what you’re seeing. |
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Posted: 12/12/2018 10:40:25 AM EDT
[#33]
Quote HistoryQuoted:
Unpossible. Many experts here have repeatedly assured me that there is no connection whatsoever between barrel length and accuracy. Quote HistoryQuoted:
Quoted:
Stability is a function primarily of bullet length, velocity, and bullet twist. Longer bullets need tighter twist and higher velocity to stabilize. The Barnes 70 TSX bullet is solid copper. That makes it much longer than a comparable lead core bullet. It's as long as a 77 grain OTM. It takes at least a 1:8 twist in 16" barrel to avoid keyholing. 70 TSX loaded to full power 5.56 keyhole badly in my 1:9 barrel, but shoot close to MOA in 1:8. Whacking off 6" from the barrel will reduce velocity significantly. Enough drop in velocity will eventually destabilize the bullet, even in 1:7, and many 1:7 barrels are not true 1:7. Often they check out on the slow side. Even so, with a BC of .314, length 1.036", Berger's twist calculator suggests that 1:7 can stabilize it in that pistol barrel even at as low as only 2,000 fps. I doubt twist is a problem if the barrel is actually 1:7. http://www.bergerbullets.com/twist-rate-calculator/ Stability aside, barrel harmonics will be significantly different with those different loads. Harmonics, alone, can cause that much POI shift. If OP's barrel is truly 1:7 he should have enough velocity in that short barrel to not keyhole. But, many barrels have slower twist than stamped on the barrel. A few tenths, like rounding down from 1:7.5 and calling it 1:7, can sometimes make a difference. It's easy to check twist yourself and is a good data point to know. Here is a common method using a cleaning rod and tape: https://m.youtube.com/watch?v=cdoCNZBlRGQ . |
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Posted: 12/12/2018 3:03:48 PM EDT
[#34]
Quote HistoryQuoted: Apples and monkeys comparison. I agree that shorter barrel length does not degrade inherent accuracy. That's inherent accuracy. Here we are talking about something different, velocity as a factor in stabilizing long bullets. Dropping velocity several hundred fps reduces bullet rpm, as that is related to both twist rate and velocity. You can see the effect in the Berger twist calculator when you reduce velocity while keeping all other variables the same. At some point, if the velocity is low enough the bullet will destabilize and keyhole. If OP's barrel is truly 1:7 he should have enough velocity in that short barrel to not keyhole. But, many barrels have slower twist than stamped on the barrel. A few tenths, like rounding down from 1:7.5 and calling it 1:7, can sometimes make a difference. It's easy to check twist yourself and is a good data point to know. Here is a common method using a cleaning rod and tape: https://m.youtube.com/watch?v=cdoCNZBlRGQ . Several have commented that many 1/7 barrels are not truly 1/7. Is that due to fluctuations in the manufacturing process or does the manufacturer know - whether they admit or not - that what they are putting out is not really 1/7 For example, it’s the difference between if I bought ten barrels, some would be true 1/7s and some wouldn’t because manufacturing variances vs if I buy ten matching barrels, all ten will have the same twist rate of let’s say, 1/7.5 despite being adversities as 1/7. |
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Posted: 12/12/2018 3:33:48 PM EDT
[#35]
Quote HistoryQuoted: Thanks for that link. I'm going to check tonight. Several have commented that many 1/7 barrels are not truly 1/7. Is that due to fluctuations in the manufacturing process or does the manufacturer know - whether they admit or not - that what they are putting out is not really 1/7 For example, it's the difference between if I bought ten barrels, some would be true 1/7s and some wouldn't because manufacturing variances vs if I buy ten matching barrels, all ten will have the same twist rate of let's say, 1/7.5 despite being adversities as 1/7. The blank maker knows. The company contracting them probably doesn't care beyond what is stamped. (Reminds me of German Salazar ordering a .30 cal blank from Krieger 1:11.25, but getting a 1:15) The former. Small sample: https://www.ar15.com/forums/ar-15/How-much-tolerance-in-twist-rate-Measure-yours-please-/12-720559/ |
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Posted: 12/12/2018 3:59:33 PM EDT
[#36]
Also, bullets don't come out of the barrel perfectly stabilized and flying in a perfect arch. It usually takes a little distance for them to settle. I've heard that heavier/longer bullets like the 77gr smk don't settle until about 200yds
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Posted: 12/12/2018 5:54:38 PM EDT
[#37]
Quote HistoryQuoted:
Also, bullets don't come out of the barrel perfectly stabilized and flying in a perfect arch. It usually takes a little distance for them to settle. I've heard that heavier/longer bullets like the 77gr smk don't settle until about 200yds https://s14-eu5.startpage.com/cgi-bin/serveimage?url=http:%2F%2Ftwolftfeet.com%2Fpdf%2Fshooting%2Findex_files%2FFleetYaw1.jpg&sp=824eede1201a94f5d0cf913fb7ced0b9  Inside 70, and not enough to matter. OP is certainly getting more angle. His bullets are woke. 
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