Will I be over stabilized?

[Propbndr]

My 223 rem AR has a 16” barrel with a 1 in 8 twist. No matter what velocity I use, all the calculators I have used say that that I am over stabilized. I have never seen any evidence of one of my rounds disintegrating.

 

[dellet]

As I test this more, I'm not sure there is any such thing as "over stabilized." That is, as long as the bullet can hold up and make it to the target. Even in full blown BR rifles, I'm struggling to see an accuracy difference. YMMV

I don’t know if this is due to “over stabilization”, but it seems that tuning for the best load is more difficult, maybe better said that the window or node for best accuracy is smaller at higher spin.

Have you seen that?

 

[Mike Hightower]

I don’t know if this is due to “over stabilization”, but it seems that tuning for the best load is more difficult, maybe better said that the window or node for best accuracy is smaller at higher spin.

Have you seen that?

IMO. I do think nodes do get smaller with velocity for any given case. So what you're saying with the revs makes sense to me. I'm not smart enough to know if it's from the velocity or Rpm's but in my findings are the nodes do narrow as I go up in charge weight. Great Question.

 

[gunsandgunsmithing]

I don’t know if this is due to “over stabilization”, but it seems that tuning for the best load is more difficult, maybe better said that the window or node for best accuracy is smaller at higher spin.

Have you seen that?

Actually, I'd say just the opposite. But again, I think it's just harder to make long bullets shoot quite as tight as shorter bullets. So it's a little bit like apples and oranges. If anything, I think a more stable bullet shoots a tad better and easier...but we're splitting pretty fine hairs here. I can't figure how a faster spin would create a narrower tune window, looking at it from a practical standpoint. Anything's possible but I don't see a logical reason, on the surface at least.

Just for clarity, I'm not advocating taking twists to extremes but rather, "is a little faster spin good or bad" kinda thing. ie, my 12 twists using 68's is not a huge change but I actually think it's better than a marginally stable 14 twist...fwiw. Just gotta test these things to know for sure is all. Maybe most interesting about my testing so far is that it seems to hold up in a 10 twist bbl also... The best shooting bullets seem to be 68-80 grain bullets vs the longer, more "twist appropriate" bullets from several different makers. They're close but consistently, the lighter bullets are outperforming the heavier ones. Too little difference between the 68 and 80's to say either way on those.

 

[Larry Koch]

As I test this more, I'm not sure there is any such thing as "over stabilized." That is, as long as the bullet can hold up and make it to the target. Even in full blown BR rifles, I'm struggling to see an accuracy difference. YMMV

Even in short range bench rest competition? 100/200. Why are the best shooter playing small amounts of twist variations? like 13.85-13.75, 13.65-13.5 and 13.5-13.35. 13.25-13 just asking because I dont know?

 

[gunsandgunsmithing]

Even in short range bench rest competition? 100/200. Why are the best shooter playing small amounts of twist variations? like 13.85-13.75, 13.65-13.5 and 13.5-13.35. 13.25-13 just asking because I dont know?

Those are all gain twist numbers but as to what I think you're asking, all I can say is that testing and results are all that matters and I simply can't see a down side to using a 12 twist, so far and the 10 is very good as well. These are not gain twists. Lots of people do things because it's what everyone says and does. Some people test. That's what I'm doing and just posting what I'm seeing. I'm not saying it's what others should do but that I'm very satisfied with what I'm seeing and the results do back it up...fwiw. Yes, this is short range BR. Again, maybe jackets are better and that would explain why it would've been truer then than now, so to speak. All I know for sure is I'm not going back to the 13.5-14 twist bbls unless something changes that changes my results.

There probably is a break point where it can be too fast but I've not found it with 12 or 10 twists yet, with 68-80 grainers. The 12's are my go to twist now, for sr br. The 10 is just for testing this and maybe tough conditions, 200-300 match here and there and maybe the Tack Driver, if I can ever make that one.

I will add, I don't think sr is a bc contest at all and even to at least about 600, I think the accuracy difference might be enough to be of more significance than bc on decent days. Ya just have to run the numbers and do the testing but a 95 berger at 3100 vs a 105 berger at 2850 is a flat out wash in regard to drift at 600. So, I'd go with the one that shoots smallest there. That's kinda the point of all of this.

 

[dellet]

Actually, I'd say just the opposite. But again, I think it's just harder to make long bullets shoot quite as tight as shorter bullets. So it's a little bit like apples and oranges. If anything, I think a more stable bullet shoots a tad better and easier...but we're splitting pretty fine hairs here. I can't figure how a faster spin would create a narrower tune window, looking at it from a practical standpoint. Anything's possible but I don't see a logical reason, on the surface at least.

Just for clarity, I'm not advocating taking twists to extremes but rather, "is a little faster spin good or bad" kinda thing. ie, my 12 twists using 68's is not a huge change but I actually think it's better than a marginally stable 14 twist...fwiw. Just gotta test these things to know for sure is all. Maybe most interesting about my testing so far is that it seems to hold up in a 10 twist bbl also... The best shooting bullets seem to be 68-80 grain bullets vs the longer, more "twist appropriate" bullets from several different makers. They're close but consistently, the lighter bullets are outperforming the heavier ones. Too little difference between the 68 and 80's to say either way on those.

I wonder if the difference is at opposite ends of the extremes.

Smaller window at over stabilized, larger window at marginal stability.

This was part of the challenge finding a twist that would should shoot long, heavy bullets slow, and short light bullets fast from the same twist. It seemed to challenge a lot of accepted truths. Part of the problem is group size expectations, but often bullets that would not fly on paper, did exceptionally well on target out to 300 yards.

This showed in subsonic shooting a couple ways. Palma bullets as an example or those known to fly well through the trans-sonic range, when matched with a twist that would spin them at speeds they were designed for, became very accurate. The other variable that helped to duplicate was peak pressure. This insured the bullet would obturate as designed. This became very important using solids, where gas cutting from the bore not being sealed is an issue.

It seems that when a bullet spinning at the rate designed for and fired at the pressures also designed for, mattered just as much if not more than actual velocity.

Just some observations

 

[gunsandgunsmithing]

I wonder if the difference is at opposite ends of the extremes.

Smaller window at over stabilized, larger window at marginal stability.

This was part of the challenge finding a twist that would should shoot long, heavy bullets slow, and short light bullets fast from the same twist. It seemed to challenge a lot of accepted truths. Part of the problem is group size expectations, but often bullets that would not fly on paper, did exceptionally well on target out to 300 yards.

This showed in subsonic shooting a couple ways. Palma bullets as an example or those known to fly well through the trans-sonic range, when matched with a twist that would spin them at speeds they were designed for, became very accurate. The other variable that helped to duplicate was peak pressure. This insured the bullet would obturate as designed. This became very important using solids, where gas cutting from the bore not being sealed is an issue.

It seems that when a bullet spinning at the rate designed for and fired at the pressures also designed for, mattered just as much if not more than actual velocity.

Just some observations

No argument from me. My testing is pretty limited at this point so I'm only posting what I've seen to date with this test. Nothing written in stone, for sure. It does seem logical that it's easier to shoot small with a stable bullet and short bullets stabilize easier than long ones...which is why the need a faster twist in the first place. Long ones, that is.

I'm not sure that we're talking about exactly the same thing but either way, I wouldn't argue hard. The differences I'm seeing are not big but they are consistent. So, I would expect to need a very accurate rifle before it would matter. One barrel is not enough, IMHO, to form a solid opinion on what I'm seeing but being consistent does give me reason to believe there is more there to experiment around and with.

 

[AckAck]

I took a 1:8 twist 6 Hagar Match Rifle that had a seasoned barrel to Wyoming to hunt prairie dogs once. I used Nosler Varmagedons with a spicy load of 8208. Things would go fine until I would get the barrel hot, then the bullets would start “poofing” and flying apart. Once the barrel cool off I could go back to work.

 

[gunsandgunsmithing]

I took a 1:8 twist 6 Hagar Match Rifle that had a seasoned barrel to Wyoming to hunt prairie dogs once. I used Nosler Varmagedons with a spicy load of 8208. Things would go fine until I would get the barrel hot, then the bullets would start “poofing” and flying apart. Once the barrel cool off I could go back to work.

That's on the ragged edge there. Savage muzzle loaders are like that too, IME. The sabot strips out with a warm load if the temps get above a certain point and no telling where the bullet goes. Lol! Just back it down or go to a slower twist on the next one. Most cut rifle bbl makers can do whatever twist ya want, like 1/2 twists...9.5 for example. And keep it clean and smooth too. Lots of factors if you're that close to the cliff.

 

[AckAck]

That's on the ragged edge there. Savage muzzle loaders are like that too, IME. The sabot strips out with a warm load if the temps get above a certain point and no telling where the bullet goes. Lol! Just back it down or go to a slower twist on the next one. Most cut rifle bbl makers can do whatever twist ya want, like 1/2 twists...9.5 for example. And keep it clean and smooth too. Lots of factors if you're that close to the cliff.

Yup….I knew it was sketchy when I made the loads for it. As I said, I was originally using the rifle for Highpower and shooting 107’s out of it mostly. It was a lot of fun smacking prairie dogs with it though.

 

[gunsandgunsmithing]

Yup….I knew it was sketchy when I made the loads for it. As I said, I was originally using the rifle for Highpower and shooting 107’s out of it mostly. It was a lot of fun smacking prairie dogs with it though.

Never been prairie doggin but I have some friends that go pretty regularly. Most say the faster twists yield a more violent reaction. It's on my bucket list to do one day.

 

[SteveOak]

One thing spinning faster will do is to exacerbate any imbalance in the bullet.

 

[gunsandgunsmithing]

One thing spinning faster will do is to exacerbate any imbalance in the bullet.

Technically true but I honestly think either it was overblown to begin with or jackets have gotten better...or both. I've been working with this for a few years now and have not found a correlation. Might be there but I can't shoot the difference. In fact, I've gone to 12 twist bbls for everything from 68-80's but have been testing a 10 twist. The 10 still shoots the 68 and 80's better than the more "twist appropriate" weights. Hard to tell a difference between the 68 and 80's but both are "competitive." That's the best I can state it...from a 10 twist! When I step up to the longer projectiles is when the true accuracy goes away. Just is what it is and it's just one bbl but it all just calculates predictably. It would explain a lot. Like the long high bc bullets never being truly competitive at short range. Of course that works both ways. I'm only testing for all out accuracy from 100-300 yards. In every case so far, the lighter bullets have outperformed the more twist appropriate weights(lengths)

 

[SteveOak]

Not that I can contribute any concrete nor even anecdotal input to support my point but it would seem, given the differance in mass and volume, that lead, the content/purity, and evenness of dispersion and/or lack of voids (even microscopic) of which, would be the significant contributer to any impalance.

 

[gunsandgunsmithing]

Not that I can contribute any concrete nor even anecdotal input to support my point but it would seem, given the differance in mass and volume, that lead, the content/purity, and evenness of dispersion and/or lack of voids (even microscopic) of which, would be the significant contributer to any impalance.

I'm sure I'm misspelling his name but there used to be a man by the name of Vern Junke(sp) that made a machine to test these very things. The Junke Machine. Maybe Boyd or one of the others will remember it and be able to offer more insight. I just know what works for me and yes, I did subscribe to the same logic as you for a lot of years. Not trying to change any minds. It took a few years for me convince myself! Lol! @BoydAllen

 

[Laurie]

Technically true but I honestly think either it was overblown to begin with or jackets have gotten better...or both.

[exacerbating imbalance in the bullet]

For many decades the British and British Commonwealth 'Target Rifle' (fullbore/Palma/sling type prone) shooting saw organiser issued 7.62 arsenal ammunition mandatory in major competitions, a hangover from the days of .303 Enfield 'Service Rifle'.

The mainstay for many years was the Royal Ordnance Radway Green arsenal 'Green Spot' 146gn FMJBT so-called sniper round. Some batches of this stuff were really dire, much down to poor bullets.

As a result GB TR evolved in three ways after its 1968 adoption to deal with ammunition shortcomings:

• 'tight' barrels as bullets were usually undersize compared to match quality 308s.
• 
  
• the four-lug SWING / Paramount / RPA action design - four equally spaced lugs giving better support and results with ammunition with out of square case-heads.
• 
  
• finally, and vitally, a 1 in 14" rifling pitch to cope with out of balance bullets due to inconsistent jacket thickness. This rate was trialled against faster twists many times, and it definitely gave superior long-range results compared to 12 or 13 rates with these bullets.

This ammunition policy did real harm to the discipline. As a separate development the RORG sniper round was improved after the 1983 Falklands War. The inquest into our army's performance after the war included the finding that the then WW2 No.4 rifle based Lee-Enfield L42A1 sniper rifle was now entirely obsolete and that the issued ammunition was poor so that 800m shots had a very low hit probability. The Accuracy International rifle replaced the former and RORG produced an 'improved' 155gn FMJBT sniper round which was sold to the GB NRA as the 'RG Bisley Match'. Again, lot to lot variability was excessive, the worst lots being very poor. Eventually BAe, RORG's owner, decided it would no longer sell ammunition to civilian organisations and the GB NRA had to go commercial with first RWS, now Lithuanian GGG cartridges, in both cases loading the original 155gn Sierra MK (#2155). Naturally, twist rates were changed with 13 becoming the norm, and some using 12 or faster to allow heavier bullets in handloads for regional and club matches.

 

[gunsandgunsmithing]

[exacerbating imbalance in the bullet]

For many decades the British and British Commonwealth 'Target Rifle' (fullbore/Palma/sling type prone) shooting saw organiser issued 7.62 arsenal ammunition mandatory in major competitions, a hangover from the days of .303 Enfield 'Service Rifle'.

The mainstay for many years was the Royal Ordnance Radway Green arsenal 'Green Spot' 146gn FMJBT so-called sniper round. Some batches of this stuff were really dire, much down to poor bullets.

As a result GB TR evolved in three ways after its 1968 adoption to deal with ammunition shortcomings:

• 'tight' barrels as bullets were usually undersize compared to match quality 308s.
• 
  
• the four-lug SWING / Paramount / RPA action design - four equally spaced lugs giving better support and results with ammunition with out of square case-heads.
• 
  
• finally, and vitally, a 1 in 14" rifling pitch to cope with out of balance bullets due to inconsistent jacket thickness. This rate was trialled against faster twists many times, and it definitely gave superior long-range results compared to 12 or 13 rates with these bullets.

This ammunition policy did real harm to the discipline. As a separate development the RORG sniper round was improved after the 1983 Falklands War. The inquest into our army's performance after the war included the finding that the then WW2 No.4 rifle based Lee-Enfield L42A1 sniper rifle was now entirely obsolete and that the issued ammunition was poor so that 800m shots had a very low hit probability. The Accuracy International rifle replaced the former and RORG produced an 'improved' 155gn FMJBT sniper round which was sold to the GB NRA as the 'RG Bisley Match'. Again, lot to lot variability was excessive, the worst lots being very poor. Eventually BAe, RORG's owner, decided it would no longer sell ammunition to civilian organisations and the GB NRA had to go commercial with first RWS, now Lithuanian GGG cartridges, in both cases loading the original 155gn Sierra MK (#2155). Naturally, twist rates were changed with 13 becoming the norm, and some using 12 or faster to allow heavier bullets in handloads for regional and club matches.

Thank you Laurie! As always, your input is valuable. I'm not sure if your post agrees or is counter to my findings, honestly. It seems that bad bullets improved with slower twists, to which I'd agree, but good bullets, not so much if at all. To which, I'd also agree.

In the end we have a couple of things, both small. Lets say that, while extremely good, even the best bullet is not perfect, so in theory, the slower twist would be good. But the other point is related because if the quality of the bullet is very good, the improvement may then be less consequential than an increase in BC from a more stable bullet. Point of diminishing returns on slow twist vs improved bullet flight, not being on the ragged edge.

I've spoken with a couple of sharp guys about this. One is Randy Robinett. Randy seems to feel that the rate of "really good" bbls goes up with a little faster twist. I hope I'm quoting him right and that he will elaborate on that a bit. @RGRobinett

I'm going with results. I like the ability to shoot 80's in a 12 twist but I can't see a difference with 68's from a 12 to a 13.5 or 14. I never won a nats with a 13.5 or 14 but I have a grand and 200 national agg wins shooting 12's...fwiw. At worst, it ain't bad! Lol! I will say these are the two best rifles I've ever owned. Both have had several bbls of mostly 12 but also 13.5s on them to compare. IOW, not a one bbl or rifle test, but several bbls on two different rifles.

 

[Murray Brook]

I'm sure I'm misspelling his name but there used to be a man by the name of Vern Junke(sp) that made a machine to test these very things. The Junke Machine. Maybe Boyd or one of the others will remember it and be able to offer more insight. I just know what works for me and yes, I did subscribe to the same logic as you for a lot of years. Not trying to change any minds. It took a few years for me convince myself! Lol! @BoydAllen

I believe this is what you are refering to.

 

[Idaho-Lefty]

One thing spinning faster will do is to exacerbate any imbalance in the bullet.

AGREE with,.. this ^^^
I've had Grouping problems with NOT getting, "Repeatable" Accuracy from, Hornady 87 V-Maxes, in a 1-7.5 twist barrel, in my 6 xc @ 3,200 - 3,300 FPS +-
But, they Shoot FINE, in my grandsons .243 win. Tikka, 10 Twist @ 3,150+ FPS
I finally gave Up on THIS Bullet ( After MANY, Tries ! ) and gave them ALL, to my grandson for,.. Steel Practice.
He uses, the super accurate, 87 gr. Berger, H-VLD'S, "DRT, Killer Bullets" to Hunt, Deer / Antelope with.
I'm stuck using, the extremely accurate, 95 gr. Classic Hunters for, LR Varmints but, they AREN'T as, "Explosive" !
The 80 gr F B Berger, Var / Targ bullets, also work Great, to 300+ Yds on Sage Rats ( Both Bullets, Cut them in 1/2 ).
But, . NO,.. "Splody" !!!