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Posted: 12/24/2023 9:16:07 PM EDT
I found a stripped upper that some how magically appeared.
I have a 12 inch complete upper. I do not need a 7.5 upper. ( I sound like my wife). Fuck it! I am getting one. (Now I sound like me). All the barrels that I have found are 1/7twist. Will 55 grain work in a short barrel with that twist? Other bullets are not an option since I am sitting on roughly 8,000 bullets and 3000 rounds of ammo. It will be for fun not precision. However I do like to hit what I shoot at. |
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NC, USA
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Posted: 12/24/2023 10:10:34 PM EDT
[#1]
I saw a gel test on YouTube a couple weeks back with 55 gr Gold Dot and a 7.5 and it did well.
Ball ammo not so much. |
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Posted: 12/24/2023 11:18:34 PM EDT
[#2]
Here's a twist rate chart but take it with a grain of salt.
It's not the end of the world if your bullets end up in the yellow spectrum. My 10.3 will stabilize 55 gr bullets just fine and is dead as accurate. Not sure on the 7.5" but try it at different distances and check your paper targets for keyholing bullets.  Attached File |
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MN, USA
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Posted: 12/25/2023 1:12:36 AM EDT
[#3]
Will 55 grain work in a short barrel with that twist? Yes, but distance will be limited due to the reduced velocity. |
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Posted: 12/25/2023 8:27:19 PM EDT
[#4]
Thanks for the replies. Ended up ordering a complete upper from Right to Bear Arms.
7.5 with a free float in burnt bronze. With there sale I could not put it together as cheap. Still have a problem. What to do with the stripped upper. |
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MN, USA
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Posted: 12/25/2023 10:46:20 PM EDT
[#5]
Still have a problem. What to do with the stripped upper. I think you meant "opportunity" 
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PA, USA
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Posted: 1/2/2024 1:07:23 PM EDT
[Last Edit: EDL]
[#6]
Barrel length makes no difference on twist. A 2" at 1:7 will spin the bullet the same as a 16". The only way it won't is if the bullet strips in the rifling. Velocity, on the other hand, will be different, of course. 1:7 isn't needed to stabilize a 55 grainer, but the extra spin won't hurt anything too much either (although you can over spin a bullet to the point it will fly arpart, or it will affect accuracy at longer ranges due to spin drift). And that is a combination of spin and velocity. I've turned bullets in my 22-250 to powder puffs by driving them in excess of 4300 FPS with light, frangible/varmint type bullets. You'll be fine at 1:7 with the 55 grainers and that 1:7 will give you the head room for longer/heavier ones later if you want.
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Posted: 2/11/2024 6:42:49 PM EDT
[#7]
Quote HistoryOriginally Posted By EDL: Barrel length makes no difference on twist. A 2" at 1:7 will spin the bullet the same as a 16". The only way it won't is if the bullet strips in the rifling. Velocity, on the other hand, will be different, of course. 1:7 isn't needed to stabilize a 55 grainer, but the extra spin won't hurt anything too much either (although you can over spin a bullet to the point it will fly arpart, or it will affect accuracy at longer ranges due to spin drift). And that is a combination of spin and velocity. I've turned bullets in my 22-250 to powder puffs by driving them in excess of 4300 FPS with light, frangible/varmint type bullets. You'll be fine at 1:7 with the 55 grainers and that 1:7 will give you the head room for longer/heavier ones later if you want. Finally someone who gets it. |
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Posted: 2/11/2024 8:37:51 PM EDT
[#8]
Quote HistoryOriginally Posted By Big-Bore: Finally someone who gets it. Quote HistoryOriginally Posted By Big-Bore: Originally Posted By EDL: Barrel length makes no difference on twist. A 2" at 1:7 will spin the bullet the same as a 16". The only way it won't is if the bullet strips in the rifling. Velocity, on the other hand, will be different, of course. 1:7 isn't needed to stabilize a 55 grainer, but the extra spin won't hurt anything too much either (although you can over spin a bullet to the point it will fly arpart, or it will affect accuracy at longer ranges due to spin drift). And that is a combination of spin and velocity. I've turned bullets in my 22-250 to powder puffs by driving them in excess of 4300 FPS with light, frangible/varmint type bullets. You'll be fine at 1:7 with the 55 grainers and that 1:7 will give you the head room for longer/heavier ones later if you want. Finally someone who gets it. So far so good. A faster twist will cause higher chamber pressure which will limit velocity. A twist faster than you need limits velocity and wastes capability. |
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Posted: 2/11/2024 8:38:14 PM EDT
[Last Edit: SteveOak]
[#9]
Double tap
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Posted: 2/12/2024 12:08:57 AM EDT
[#10]
Quote HistoryOriginally Posted By EDL: Barrel length makes no difference on twist. A 2" at 1:7 will spin the bullet the same as a 16". The only way it won't is if the bullet strips in the rifling. Velocity, on the other hand, will be different, of course. 1:7 isn't needed to stabilize a 55 grainer, but the extra spin won't hurt anything too much either (although you can over spin a bullet to the point it will fly arpart, or it will affect accuracy at longer ranges due to spin drift). And that is a combination of spin and velocity. I've turned bullets in my 22-250 to powder puffs by driving them in excess of 4300 FPS with light, frangible/varmint type bullets. You'll be fine at 1:7 with the 55 grainers and that 1:7 will give you the head room for longer/heavier ones later if you want. Um - it can't. The velocities achieved btwn 2" and 16" bbls in 5.56 are wildly different, so the rpm of the bullets thus launched from two wildly different barrels will be wildly different. |
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USA
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Posted: 2/12/2024 3:36:53 AM EDT
[#11]
My 7" 1-9 shoot 55 and 62gr fine
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MI, USA
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Posted: 2/12/2024 3:40:50 PM EDT
[#12]
Quote HistoryOriginally Posted By backbencher: Um - it can't. The velocities achieved btwn 2" and 16" bbls in 5.56 are wildly different, so the rpm of the bullets thus launched from two wildly different barrels will be wildly different. Quote HistoryOriginally Posted By backbencher: Originally Posted By EDL: Barrel length makes no difference on twist. A 2" at 1:7 will spin the bullet the same as a 16". The only way it won't is if the bullet strips in the rifling. Velocity, on the other hand, will be different, of course. 1:7 isn't needed to stabilize a 55 grainer, but the extra spin won't hurt anything too much either (although you can over spin a bullet to the point it will fly arpart, or it will affect accuracy at longer ranges due to spin drift). And that is a combination of spin and velocity. I've turned bullets in my 22-250 to powder puffs by driving them in excess of 4300 FPS with light, frangible/varmint type bullets. You'll be fine at 1:7 with the 55 grainers and that 1:7 will give you the head room for longer/heavier ones later if you want. Um - it can't. The velocities achieved btwn 2" and 16" bbls in 5.56 are wildly different, so the rpm of the bullets thus launched from two wildly different barrels will be wildly different. I for one, would be very interested in seeing this discussed further. Maybe I'm misreading this, but it doesn't sound like you guys are actually disagreeing with each other. |
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Posted: 2/12/2024 4:03:19 PM EDT
[#13]
Quote HistoryOriginally Posted By Tiribulus: I for one, would be very interested in seeing this discussed further. Maybe I'm misreading this, but it doesn't sound like you guys are actually disagreeing with each other. Quote HistoryOriginally Posted By Tiribulus: Originally Posted By backbencher: Originally Posted By EDL: Barrel length makes no difference on twist. A 2" at 1:7 will spin the bullet the same as a 16". The only way it won't is if the bullet strips in the rifling. Velocity, on the other hand, will be different, of course. 1:7 isn't needed to stabilize a 55 grainer, but the extra spin won't hurt anything too much either (although you can over spin a bullet to the point it will fly arpart, or it will affect accuracy at longer ranges due to spin drift). And that is a combination of spin and velocity. I've turned bullets in my 22-250 to powder puffs by driving them in excess of 4300 FPS with light, frangible/varmint type bullets. You'll be fine at 1:7 with the 55 grainers and that 1:7 will give you the head room for longer/heavier ones later if you want. Um - it can't. The velocities achieved btwn 2" and 16" bbls in 5.56 are wildly different, so the rpm of the bullets thus launched from two wildly different barrels will be wildly different. I for one, would be very interested in seeing this discussed further. Maybe I'm misreading this, but it doesn't sound like you guys are actually disagreeing with each other. Bullet stability is dependent on rpm and length of bullet. Twist and velocity affect rpm. Length of bbl affects velocity. |
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Posted: 2/12/2024 5:44:07 PM EDT
[#14]
Quote HistoryOriginally Posted By backbencher: Bullet stability is dependent on rpm and length of bullet. Quote HistoryOriginally Posted By backbencher: Bullet stability is dependent on rpm and length of bullet. 100% correct Originally Posted By backbencher: Twist and velocity affect rpm. 100% correct Originally Posted By backbencher: Length of bbl affects velocity. Correct to varying degrees, but mostly correct. There may be some barrel length variances that do not produce a statistically significant change in velocity, that is, the change in velocity may be overshadowed by other effects or by measurement uncertantity, but this is essentially correct. |
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PA, USA
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Posted: 2/14/2024 1:04:24 PM EDT
[#15]
Backbencher is correct, when it comes to velocity vs twist and how it relates to RPM, and is true regardless of twist. My point was that 1:7 means the bullet rotates 1 time per 7" of barrel length, regardless of barrel length. My wording wasn't clear on that.
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Posted: 2/14/2024 4:35:58 PM EDT
[#16]
Quote HistoryOriginally Posted By EDL: Backbencher is correct, when it comes to velocity vs twist and how it relates to RPM, and is true regardless of twist. My point was that 1:7 means the bullet rotates 1 time per 7" of barrel length, regardless of barrel length. My wording wasn't clear on that. Gotcha - almost always true unless you've got state secret Italian progressive rifling. 
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