I think these are 2 factors that are glossed over or just out right ignored.
Rate of spin RPM is what stabilizes the bullet and velocity can make a huge difference in RPM.
And length of bullet has a big effect on RPM required for stability.
AR-15 what’s the logic?
- Thread starter igotta40
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Rate of spin RPM is what stabilizes the bullet and velocity can make a huge difference in RPM.
And length of bullet has a big effect on RPM required for stability.
CoalTrain49
Member
Some will but why would you buy a 1:7 barrel if all you plan on shooting <70 grn bullets. I'll ask you a pointed question here. If you were building a rifle and the customer said he wanted it to shoot coyotes at 2-300 yds, or shoot paper at 2-300 yds and was planning on using <70 grn match bullets, would put a 1:7 on that rifle? If you say yes then you probably need to read this.
https://www.shilen.com/calibersAndTwists.html
Jump on down to .224 CF under Caliber Twist and tell me what they recommend. <70 grn bullets is probably about what 85% of AR shooters use, which is 1:9 like the OP suggests.
That's the point the OP was trying to make. 1:9 twist is probably more suitable for 85% of all AR shooters. The point was already made that most people don't have a range close enough to shoot beyond 300 yds. My range (30 minutes) is 220 yds and the one north of me an hour is 300 yds. I live between Seattle and the Canadian border.
You might be a long range shooter but I bet that most AR owners have never ventured past 300 yds. Most of them at my range (500+ members) shoot at 100 yds. In the 8 years I've been a member I've never seen an AR shooter set a target at 200 yds and everyone and his brother has an AR. They shoot steel at 220 but that isn't exactly precision shooting.
The fact is most people are going to buy a $750 AR. They don't load their own ammo and they buy the cheapest ammo they can find, which is going to be 55 grn bulk on sale,
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35 Whelen
Member
I'm not talking about performance on paper, I'm talking about performance on animals. You do understand the difference in reaction of a given bullet striking flesh and bone based on how fast it's spinning, don't you?
Hypothesis. And I'm sure you sport a chub while quoting BC's, but they have nothing to do with the subject at hand.
Watching competitors shoot on my 600 yd. range and commenting on the observed results is hardly anecdotal. Sitting at your electronic device (ALL DAY, it would appear) with calipers measuring bullets, "connecting" with shooters (aka trolling forums), and belittling people provides no real "information".
A year ago I picked up an el cheapo Savage Axis II in .223 to keep in the laundry room gun rack for coyotes prowling around the house looking for a chicken dinner. I set about lapping the 1-9" twist (remember that) barrel with a Tubb's Kit consisting of 50 ea. Sierra 77 gr. Matchkings (.994" in length, am I right??), the same bullets Sierra tells us require a minimum 1 x 8" twist (Their words, not mine). I found an ancient metal can of BL-C(2) behind the other powders on my shelf, set up a powder measure to drop a less-than-minimum charge of 22.0 grs., the goal being just to get the bullets out of the barrel, primed and charged 50 cases, seated 50 bullets and headed to my bench with the first five, fully expecting patterns at best. I had no need to chronograph the loads but my guess is they were running less than 2500 fps, probably much less. And yet-
I guess that information is anecdotal to you as well?
Sorry if this doesn't go along with your calipers, your calculator, and your hypothesis, but it is what it is. Sometimes actually shooting tells the whole story much more succinctly than just talking about it on forums.
35W
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Varminterror
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Can I call ‘em, or what?
Same same - the Hornady 75 BTHP and 77 SMK are stubby little short ogive bullets, designed for use in Service Rifle, hence their short lengths, low BC’s, and why they stabilize in 1:9” twists…
Not that shooting big groups at 100yrds really tells you anything about stabilization, though. But it’s another cute anecdote which - again - doesn’t support the claim being made, as you’re shooting stubby bullets and pretending they’re long… maybe a common theme?
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35 Whelen
Member
Dude, you are dense. You need to re-read your own posts. Remember? "Yeah but, but, but, longer 20" - 24" barrels.....175-200 added fps...16,000 rpm more....THAT'S why those bullets stabilize in a 1-9" twist". YOUR words.
The purpose of the two targets was to show to you that a long .22 caliber bullet (.994") at relatively low velocity CAN be stabilized in a 1-9" twist, but that too went right over your head.
35W
Varminterror
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Never did I say THOSE stubby bullets, two of the few service rifle 70’s class bullets in the market, needed faster twist to stabilize - they don’t, they’re short bullets.
I DID, and repeatedly HAVE on this forum point out that the stubby little bullets like the 77 SMK and 75 BTHP do not represent the LONG bullets for which faster twists are needed, despite being heavier than most.
I’ve read your posts here often, I’m quite certain I’m not the denser of our minds - especially when you’re trying to brag up 1 1/8” 100yrd groups as evidence of stabilization.
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Varminterror
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Circling back out of hillbilly hell here…
Here’s a reality - consumers wanted faster twist rifles, so companies stopped making slow twist AR’s and started making fast twist AR’s. Pretty simple.
Yes, there ARE a few 75/77 class bullets which were designed with short ogives to fit into STANAG mags for Service Rifle use, which are SHORT bullets for their weight. Much like round nose and flat point 170-200 class 30 cal bullets, these don’t take much spin to stabilize - hell, look at the spin rate on a 1:38” 44mag… short bullets are easy to stabilize.
Yes, some Varmint bullets do come apart in flight for spin over 230-250krpm, and sure, it’s more entertaining to watch prairie dogs popped with 300krpm than 220krpm, but they pop all the same. This isn’t typically an issue for the bullets and ammo anyone buying a cheap Ruger AR556 or S&W M&P Sport will be touching, so it rarely turns an ugly head.
It’s also false to talk about overspinning and destabilization, Litz published that mythbusting in a few places as well. Millions and millions of rounds of M193 clone ammo is fired out of 1:7” mil-spec-ish AR’s every year.
This topic gets hashed and rehashed, and the same dumb card stacking happens in every instance. Someone tags that same dumb red/yellow/green table, or worse, the older Venn diagram version, and someone talks about how well their rifle groups at short range, or someone posts 1 1/8” groups at 100yrds with stubby 75’s or 77’s and pretends their weight has anything to do with their stabilization demand… but at the end of the day, the real world data is out there. Guys shoot 50-55grn bullets from 1:7” twists every day without tearing bullets apart, or without destabilizing bullets - so there’s no downside to a 1:7”.
Here’s a reality - consumers wanted faster twist rifles, so companies stopped making slow twist AR’s and started making fast twist AR’s. Pretty simple.
Yes, there ARE a few 75/77 class bullets which were designed with short ogives to fit into STANAG mags for Service Rifle use, which are SHORT bullets for their weight. Much like round nose and flat point 170-200 class 30 cal bullets, these don’t take much spin to stabilize - hell, look at the spin rate on a 1:38” 44mag… short bullets are easy to stabilize.
Yes, some Varmint bullets do come apart in flight for spin over 230-250krpm, and sure, it’s more entertaining to watch prairie dogs popped with 300krpm than 220krpm, but they pop all the same. This isn’t typically an issue for the bullets and ammo anyone buying a cheap Ruger AR556 or S&W M&P Sport will be touching, so it rarely turns an ugly head.
It’s also false to talk about overspinning and destabilization, Litz published that mythbusting in a few places as well. Millions and millions of rounds of M193 clone ammo is fired out of 1:7” mil-spec-ish AR’s every year.
This topic gets hashed and rehashed, and the same dumb card stacking happens in every instance. Someone tags that same dumb red/yellow/green table, or worse, the older Venn diagram version, and someone talks about how well their rifle groups at short range, or someone posts 1 1/8” groups at 100yrds with stubby 75’s or 77’s and pretends their weight has anything to do with their stabilization demand… but at the end of the day, the real world data is out there. Guys shoot 50-55grn bullets from 1:7” twists every day without tearing bullets apart, or without destabilizing bullets - so there’s no downside to a 1:7”.
Shanghai McCoy
Member
Tumbling too....
InTheSwamp
Member
That's the reality. Most 223/556 you see on the shelves is 55gr - it's cheaper to shoot. And most AR-15 you see in gun ranges sport the NATO-style barrel.
Bcwitt
Member
The US militery went to 1/7 in 1985 w the M16a2. A 7 twist might work better in a super heated barrel, like an m249 after a long burst. Also, 7 twist allows for heavier bullets.
Take your own advice and go back and read it. Note that they only show up to X gr they don't say for a 1:7 twist only 62gr and heavier.
16" 1:7 twist AR with 50gr AE grey tip varmint @100
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A super heated barrel had nothing to do with the US Military going with the 1-7 twist rate. The reason for the 1-7 twist was to stabilize the long M856 tracer rounds. And yes this information comes straight from the Lt Col. Lutz who was in charge of the M16A2 development program at Aberdeen Proving Grounds. Je is a member here on this forum along with ARFCOM. And they did try a 1-9 twist which stabilized the NATO M855 just fine. It was the NATO 856 tracer bullet that needed the faster 1-7 twist to properly stabilize.
Back on topic.
Not all heavy bullets will be long, some will be closer in length to the 55 and 62 grain bullets. No matter what twist is marked on your barrel, you really need to verify what the twist actually is. I have seen 1-9 marked barrels be any where from 1-8 to 1-10. Granted this was back when most civilian rifles came with 1-9 twist barrels.
And as I have stated before. you really do need to try different weight and styles of bullet in your rifle to see what shoots the best. I have seen 1-7 twist barrels that prefer 55-64 grain bullets and also 1-9 twist barrels that do very well with long heavy bullets. You won't know until you shoot each from your barrel.
Turkeytider
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Ain`t it the truth! 100 yards is all I`ve got. Would love, say, just 300 yards to stretch my 110 .223. I`d get a little more serious with targets gun wise if I had even that. 100 yards doesn`t really justify a more target oriented purchase IMO, unfortunately.
CoalTrain49
Member
Correct. Twist for bullets up to x grns. But that doesn't mean that 1:7 is the optimal twist for 55-62 grn bullets. I to have some personal experience with a Daniel Defense AR with a 1:7 twist that won't shoot 55 grn handloads worth beans. It loves >70 grn however. That's just a sample of one so doesn't actually mean much. 1:7 is the one size fits all for AR barrels but you can do better if you're building a precision rifle. I suggest you talk to a custom barrel maker.
Well you have a flawed premise in your OP that's permeated thru the thread. Most guys shooting cheap mil spec carbines with cheap FMJ ammo at 100 yards or less wouldn't notice any difference because they ain't measuring groups with calipers.
35 Whelen
Member
Since a .22 caliber bullet is going to make a hole in paper that is roughly 1/4", that appears to be a 3" target spot.
I really enjoy it when people post targets on forums because I know that at least some people are actually shooting. But more important than the size of the target is the distance at which it was fired.
35W
CoalTrain49
Member
An MOA measurement works much better. If you are correct that looks to be about 2 MOA or a shade better. About average in the world of AR's.
Now that I've stopped to think about it, I'm not sure why I'm even giving any thought to this. An AR isn't a precision rifle to begin with and they all probably shoot just about anything 2-3 MOA, even the $750 variety with bulk 55 grn ammo. A rifle for the people or Volksgewehr.
From your barrel maker
"The basic principles just outlined apply to all the calibers below.
If you are still unsure or need a recommendation we recommend contacting a bullet maker, they do the testing to determine what twist rate will best stabalize their bullets."
Note that Berger doesn't show an upper limit.
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35 Whelen
Member
I think maybe you mean confirmation bias. None here, I assure you, just looking for a little perspective to help interpret your target. Surely you can see the folly in posting a target without any information for perspective. If I missed the "@100", my apologies but I did notice you edited your post.
Nice group, by the way.
How about this-
Oh well, someone is shooting ~1 1/2" groups, no big deal.
Now the perspective.
A $50 lower and a $350 DelTon 16" Dissipator Kit, bone stock, fired with issue sights and Serbian 55 gr. FMJ ammunition at 100 yds.
See what I mean? Information is key.
35W
35 Whelen
Member
CoalTrain49
Member
Getting back to the original post,
I'm pretty sure your average AR purchaser isn't going to do that much work before they buy a $750 AR. I think mostly they're looking for the cheap seats.
Sorry if I caused any discomposure amongst the crew.
I'm gone.
You understand how time works right?
So not only did you miss the @100 yards in my post an hour before you posted about me not putting in the distance you missed it in his quote of my post.
In order for what you're trying to accuse me of happening I would have had to edit my post AFTER he quoted it and you quoted him.
I'm still having fun.
