Pennsylvania Firearm Owners Association
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  1. #11
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    Default Re: Groups going from 1/4" to 3"

    Quote Originally Posted by bamboomaster View Post
    Your 1x9 twist is too fast for the 50 gr bullet.

    If you shoot at 300 yds or more, your groups will start to resemble shotgun patterns. While it may be accurate at 100 yds, at greater distance, it's start to spin out of control, causing greater shot dispersion.

    Take a look at this chart under the heading ".224", to the right of the yellow highlighted column - which is the diameter of your 50 gr. bullet. It shows the suggested twist rate you should be using:

    Attachment 97067
    This chart can not be accurate, IMHO.

    How is it that MIL shoots 62 and 77gr, both out of 1:7 barrels, when by this chart 62 gr is best suited fo 1:12?

    Wasn't M855 (62gr.) developed at the transition of the M16a1 to A2 (1:12 twist to 1:7)?

    http://www.rimfirecentral.com/forums...d.php?t=557097

    Theres even a guy with the same rifle as OP shooting 50gr with excellent results.

    Similar results here: http://www.ifish.net/board/showthread.php?t=445775

    And here: http://forum.accurateshooter.com/thr...llets.3881234/

    These were my first three results from googling the question.
    Last edited by ianb1116; May 16th, 2017 at 02:49 PM.
    I'm only here for the wood c-rings.

  2. #12
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    Default Re: Groups going from 1/4" to 3"

    Quote Originally Posted by ianb1116 View Post
    This chart can not be accurate, IMHO.

    How is it that MIL shoots 62 and 77gr, both out of 1:7 barrels, when by this chart 62 gr is best suited fo 1:12?

    Wasn't M855 (62gr.) developed at the transition of the M16a1 to A2 (1:12 twist to 1:7)?

    http://www.rimfirecentral.com/forums...d.php?t=557097

    Theres even a guy with the same rifle as OP shooting 50gr with excellent results.

    Similar results here: http://www.ifish.net/board/showthread.php?t=445775

    And here: http://forum.accurateshooter.com/thr...llets.3881234/

    These were my first three results from googling the question.
    Just read those threads, and they pretty much all talk about 100 yard accuracy. My 100 yard accuracy is not the problem. If I was only shooting the gun from the bench at 100 yards I would be more than happy with the 1/4" groups I was getting. The problem is that when I take shots further, my accuracy suffers dramatically. Hell, if I wouldn't have shot this thing at 200 yesterday I wouldn't have any reason to complain (not that I'm actually complaining, just looking for answers to a perplexing question). All I know is that SOMETHING is happening between 100 yards and 200 yards that is causing bullets to string. I'm gonna buy a box of factory 62 and 69 gr bullets and see if accuracy is any better at distance with those. Don't want to get into throwing this load away completely yet. Who knows, maybe I just plain old was having a bad range session at 200 yards.

  3. #13
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    Default Re: Groups going from 1/4" to 3"

    I live in the camp that says you can't spin a bullet too fast (within reason). Try again another day before you reengineer your ammo. I shoot 55's out of my cheap PSA ar with a 1:7 twist, I can attain 1-2 moa. ( Usually 2) with iron sights from a bench.I am not a great shot. I use cfe, so I can't comment on your load. Maybe too much coffee or your scope is loose ?

  4. #14
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    Default Re: Groups going from 1/4" to 3"

    Quote Originally Posted by DukeConnor View Post
    I live in the camp that says you can't spin a bullet too fast (within reason). Try again another day before you reengineer your ammo. I shoot 55's out of my cheap PSA ar with a 1:7 twist, I can attain 1-2 moa. ( Usually 2) with iron sights from a bench.I am not a great shot. I use cfe, so I can't comment on your load. Maybe too much coffee or your scope is loose ?
    Literally just took her back out. Same results as before. Will post pics when I get back to the house. Too dumb to post pics from my phone.

  5. #15
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    Default Re: Groups going from 1/4" to 3"

    I wrote a lengthy reply, but got timed out and it went "POOF!". Hey, it's probably for the better...

    But kudos to everyone who has posted here for we are all attempting to address the OP's accuracy problem in his rifle, in his 1x9 barrel twist, with his 50gr V-Max bullet, with 21.9 grains of IMR 4198 (yeah, I know, OP said IMR 2198).

    The issue is rotational speed. When fired at 3200 fps in a 1x7" twist barrel, the bullet is rotating at 330,000 rpms when it leaves the muzzle. Although a fast twist works well with military ammo (heavier jacketing), varmit bullets with their conventional light construction are usually ripped apart as they leave the muzzle, especially if a fast barrel twist rate is involved.

    Military grade bullets work in faster twist rate barrels because of the way they are constructed.

    And compared to 1x12, 1x9 is a fast twist rate....

    Speer tests all of its varmit 223 Rem bullets (not the same as 5.56 NATO) in a 1x12 barrel. They do that for a reason - it's the correct twist rate to use for these lighter bullets and produces significant less roational speed.

    The OP worked up this load in a 1x12 twist barrel and it shot fabulously. When he shot it in a 1x9 twist barrel, it held together fine at 100 yds. But he had a problem at 200 yds when the rotational speed started to overcome the forward velocity of the bullet. At a 100 yds still further, just hitting the paper would be challenging.

    And certainly not gratifying...

    So, after consulting three reloading manuals (Speer #14, Hornady #9, and Modern Reloading #2), I'm still in the crowd of ONE that believes the bullet weight of 50 grains, a velocity of about 3200 fps, and the barrel twist rate of 1x9 are improperly matched.

    It's totally OK if your views are different. The OP will eventually figure it out at the range

    General Rule: "Longer, heavier bullets do better with a faster twist"

    Corollary 1: "Shorter, lighter bullets do better with a slower "twist"



    As far as calculation your bullet rotation, here's the general formula:

    Bullet RPM = MV x (12/barrel twist rate) x 60


    Here's a hypothetical example for your 1x9 twist barrel:

    Bullet RPM = 3200 x (12/9) x 60 = 256,000 RPM


    Here's a hypothetical example for your old 1x12 twist barrel:

    Bullet RPM = 3200 x (12/12) x 60 =192,000 RPM



    Now note the 64,000 RPM difference in rotational speed (256,000 - 192,000). I really think this is the issue...
    Last edited by bamboomaster; May 16th, 2017 at 07:07 PM. Reason: Corrected spelling and added formula
    - bamboomaster

  6. #16
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    Default Re: Groups going from 1/4" to 3"

    Quote Originally Posted by bamboomaster View Post
    I wrote a lengthy reply, but got timed out and it went "POOF!". Hey, it's probably for the better...

    But kudos to everyone who has posted here for we are all attempting to address the OP's accuracy problem in his rifle, in is 1x9 barrel twist, with his 50gr V-Max bullet, with 21.9 grains of IMR 4198 (yeah, I know, OP said IMR 2198).

    The issue is rotational speed. When fired at 3200 fps in a 1x7" twist barrel, the bullet is rotating at 330,000 rpms when it leaves the muzzle. Although a fast twist works well with military ammo (heavier jacketing), varmit bullets with their conventional light construction are usually ripped apart as they leave the muzzle, especially if a fast barrel twist rate is involved.

    Military grade bullets work in faster twist rate barrels because of the way they are constructed.

    And compared to 1x12, 1x9 is a fast twist rate....

    Speer tests all of its varmit 223 Rem bullets (not the same as 5.56 NATO) in a 1x12 barrel. They do that for a reason - it's the correct twist rate to use for these lighter bullets and produces significant less roational speed.

    The OP worked up this load in a 1x12 twist barrel and it shot fabulously. When he shot it in a 1x9 twist barrel, it held together fine at 100 yds. But he had a problem at 200 yds when the rotational speed started to overcome the forward velocity of the bullet. At a 100 yds still further, just hitting the paper would be challenging.

    And certainly not gratifying...

    So, after consulting three reloading manuals (Speer #14, Hornady #9, and Modern Reloading #2), I'm still in the crowd of ONE that believes the bullet weight of 50 grains, a velocity of about 3200 fps, and the barrel twist rate of 1x9 are improperly matched.

    It's totally OK if your views are different. The OP will eventually figure it out at the range

    General Rule: "Longer, heavier bullets do better with a faster twist"

    Corollary 1: "Shorter, lighter bullets do better with a slower "twist"
    Not much arguing with that.

    Consider me educated.

    Definitely didn't know that about the jacketing. You learn something new everyday!

    If the above is true, I can believe OP might have issues.
    I'm only here for the wood c-rings.

  7. #17
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    Default Re: Groups going from 1/4" to 3"

    Alright, here are some pics of groups from the rifle. The group from the yellow target was shot a few weeks ago and measured right at 3/8 of an inch, and is what I normally get at 100 yards with this rifle. Group on white target is today at 200 yards, shooting off bags, with no noticeable wind (I had flags up). 1st shot, far right; 2nd shot, 2nd from left; 3rd shot, center; 4th shot, 2nd from right' 5th shot far left. That group was right at 3 inches horizontal, about 3/4 inch vertical.Grp100.jpg200 Grp.jpg

    I found a good deal on some 65gr Sierras, gonna play with them and see what happens.

  8. #18
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    Default Re: Groups going from 1/4" to 3"

    Quote Originally Posted by yeahbuck36 View Post
    Alright, here are some pics of groups from the rifle. The group from the yellow target was shot a few weeks ago and measured right at 3/8 of an inch, and is what I normally get at 100 yards with this rifle. Group on white target is today at 200 yards, shooting off bags, with no noticeable wind (I had flags up). 1st shot, far right; 2nd shot, 2nd from left; 3rd shot, center; 4th shot, 2nd from right' 5th shot far left. That group was right at 3 inches horizontal, about 3/4 inch vertical.Grp100.jpg200 Grp.jpg

    I found a good deal on some 65gr Sierras, gonna play with them and see what happens.

    Horizontal stringing sounds unlike overstabilization though. If the bullets were truly overstabilized, wouldn't they be all over? I ask because I don't know.

    Here are some other forum posts about the subject. Seating depth and bipod preload jumped off the page at me.

    http://www.sniperforums.com/forum/so...stringing.html

    http://forum.accurateshooter.com/thr...pment.3787603/
    I'm only here for the wood c-rings.

  9. #19
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    Default Re: Groups going from 1/4" to 3"

    Quote Originally Posted by ianb1116 View Post
    Horizontal stringing sounds unlike overstabilization though. If the bullets were truly overstabilized, wouldn't they be all over? I ask because I don't know.

    Here are some other forum posts about the subject. Seating depth and bipod preload jumped off the page at me.

    http://www.sniperforums.com/forum/so...stringing.html

    http://forum.accurateshooter.com/thr...pment.3787603/
    That was pretty much only that group, the other ones were pretty much all over. Wish I had pictures of all of them.

  10. #20
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    Default Re: Groups going from 1/4" to 3"

    What bullets have you used for general plinking and how many? Have you hunted with soft points or hardcast?

    Also, doesn't the 527 come with polygonal rifling in some cases?

    Polygonal rifled barrels are prone to lead fouling. Just thinkin...

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