Twist rate Doppler measured
I use a 9 twist in a 30-375R with 230 hybrids at 2940 fps. Does well for ELR, though I haven't shot past 2356Y with it. Going to try Hornady's 225 soon.
Frank, I am throwing this out for "general consumption", most of this is not news to you, so please don't take it that I am trying to question or insult your intelligence. As always, I am hoping people will not just take the easy answer and they will question what is being posted in the hopes of everyone gaining a better understanding on any given topic.
Couple of different issues at play:
Bullet Stability - this could apply to a couple of different performance variables, primarily Supersonic, Transonic, and Subsonic flight characteristics. For typical shooters limited on range, the only thing they generally need to worry about is Supersonic flight characteristics. Where ELR shooters who are going way out there, Transonic & Subsonic performance becomes a major factor. Many "marginally stable bullets" will do fine in Supersonic flight, however they have a much greater chance of losing stability once they enter the Transonic range. This has been documented by Litz in a number of his papers/books, and to the best of my knowledge, backed up by real world shooting results. Once I get home, I can drag out my material from Litz if anyone would like the references. I am not a Ballistician/Rocket Scientist, so I would have to defer to someone who has a much higher level of understanding on the subject than me. I have chucked plenty of bullets at ranges where they were well into Transonic/Subsonic flight, however I can't say with any degree of authority what the results were based on? If there was a miss, was it due strictly to a stability issue, or some other issue like a bad wind call or DOPE calculation?
Bullet BC - to get optimal BC, the bullet needs to be at optimal stability (and speed). If a bullet is not truly stable, it will fly with an off axis orientation that will result in drag. If you use a good stability calculator, it should also reference the loss in BC as the bullet falls below optimal stability. In the case above, a 10 twist with a stability factor of 1.38 is going to have a 4%-5% loss in BC performance. With a stability factor above 1.5, which you would achieve with the 1:9, you could achieve both optimal stability and BC performance (yes BC is also velocity dependent).
Bullet Structural Integrity - this is the one that IMHO there needs to be a lot more research conducted on. If you go back to my posts in the threads on the new Hornady Ballistics Program, their Doppler Radar Tracking, and the resulting Custom Drag Models, you will note that I stated that damage caused to the bullet as it moves through the barrel can have an impact on a number of factors like Stability and BC. Yes, if you twist a bullet fast & hard enough, you can potentially cause change/damage to both the core and jacket. This resulting damage can obviously be anywhere from very minor and inconsequential, to complete failure of the bullet. The million dollar question, what point will a twist rate, and given velocity, result in damage to a given bullet? I specifically brought this topic up at the Fall AB Seminar, and was told that a "properly designed bullet" should have no issues being fired out of a "typical twist rate" fast enough to produce an optimal stability factor of 1.5.
In terms of the issues with using a 1:8:
- It is well over optimal stability, and may well be "overkill" for what is "really needed". NOTE - I referenced a 1:9 as being optimal in terms of stability and BC. Is the additional stability gained with the 1:8, worth the potential consequences, not in my book, but I am not an ELR shooter who relies on transonic/subsonic flight characteristics for success or failure.
- It may well be twisting fast & hard enough to damage certain bullet designs, and that would have obviously be an issue in those cases. Per the comments above, not all bullet designs are equal, and thinner jacket and softer core bullets may well have significant issues, where others would not.
- Like the bullet designs, not all barrel designs are created equal. The Rifling design could have a major impact on the changes/damage done to a bullet. A 1:8 barrel that has 4 grooves which are shallow/short with a angled edge may work perfectly fine, where a 1:8 barrel with 5 grooves which are tall with a 90 degree edge could result in damage.
- In addition to the twist rate and barrel design, the pressure/velocity could also be a significant factor. Firing a bullet at close to 65,000 PSI and 3,000 FPS could result in damage, where firing the same bullet at below 60,000 PSI and 2,850 FPS, may not result in any significant damage. The chance of bullet damage, is obviously proportional to the forces being applied against it.
- Barrel Length could also be a "contributing factor", in that a bullet may be fired "harder" with a faster burning powder out of a shorter barrel, or "easier" with a slower burning powder out of a longer barrel. Not sure that dwell time, or distance traveled, would be a major contributing factor by themselves?
IMHO, there is not a simple short answer as to whether a 1:8 will, or will not, work?
As far as any results the Army is experiencing, it is the Army, and having been there and done that, I wouldn't put it past them to be doing somethings they shouldn't, which may actually explain their results. Per my comments above, you would have to look at more than just the barrel twist rate to try and figure out why they are, or are not, succeeding?
As far as King of the 2 Mile, Fitzpatrick was actually shooting a Solid Bullet, so the issue of bullet change/damage was most likely not going to be a significant factor. However he was shooting well into the transonic/subsonic range, so stability was a major factor. Fitzpatrick had first (& second) round hits at 1,454 / 1,556 / 1,724 / 2,011 / 2,480. Litz was shooting a .338 with jacketed bullets, and he also had first round hits at 1,454 / 1,724 / 2,480. I will have to look when I get home to see if I can find the rifle specs, specifically the twist rates. My point in the King of 2 Mile reference, you don't make 1st round hits at those ranges if you don't have a very stable and predictable bullet flight path (among a lot of other things!) into the transonic/subsonic range. This was what was stressed at the Fall AB seminar, and it sounds like it is also being stressed to others.
Once again, I am just trying to put things out there, so when someone asks, "do I need a 1:10, 1:9, or 1:8", they hopefully know everything they need to be looking at to make that decision.
Couple of different issues at play:
Bullet Stability - this could apply to a couple of different performance variables, primarily Supersonic, Transonic, and Subsonic flight characteristics. For typical shooters limited on range, the only thing they generally need to worry about is Supersonic flight characteristics. Where ELR shooters who are going way out there, Transonic & Subsonic performance becomes a major factor. Many "marginally stable bullets" will do fine in Supersonic flight, however they have a much greater chance of losing stability once they enter the Transonic range. This has been documented by Litz in a number of his papers/books, and to the best of my knowledge, backed up by real world shooting results. Once I get home, I can drag out my material from Litz if anyone would like the references. I am not a Ballistician/Rocket Scientist, so I would have to defer to someone who has a much higher level of understanding on the subject than me. I have chucked plenty of bullets at ranges where they were well into Transonic/Subsonic flight, however I can't say with any degree of authority what the results were based on? If there was a miss, was it due strictly to a stability issue, or some other issue like a bad wind call or DOPE calculation?
Bullet BC - to get optimal BC, the bullet needs to be at optimal stability (and speed). If a bullet is not truly stable, it will fly with an off axis orientation that will result in drag. If you use a good stability calculator, it should also reference the loss in BC as the bullet falls below optimal stability. In the case above, a 10 twist with a stability factor of 1.38 is going to have a 4%-5% loss in BC performance. With a stability factor above 1.5, which you would achieve with the 1:9, you could achieve both optimal stability and BC performance (yes BC is also velocity dependent).
Bullet Structural Integrity - this is the one that IMHO there needs to be a lot more research conducted on. If you go back to my posts in the threads on the new Hornady Ballistics Program, their Doppler Radar Tracking, and the resulting Custom Drag Models, you will note that I stated that damage caused to the bullet as it moves through the barrel can have an impact on a number of factors like Stability and BC. Yes, if you twist a bullet fast & hard enough, you can potentially cause change/damage to both the core and jacket. This resulting damage can obviously be anywhere from very minor and inconsequential, to complete failure of the bullet. The million dollar question, what point will a twist rate, and given velocity, result in damage to a given bullet? I specifically brought this topic up at the Fall AB Seminar, and was told that a "properly designed bullet" should have no issues being fired out of a "typical twist rate" fast enough to produce an optimal stability factor of 1.5.
In terms of the issues with using a 1:8:
- It is well over optimal stability, and may well be "overkill" for what is "really needed". NOTE - I referenced a 1:9 as being optimal in terms of stability and BC. Is the additional stability gained with the 1:8, worth the potential consequences, not in my book, but I am not an ELR shooter who relies on transonic/subsonic flight characteristics for success or failure.
- It may well be twisting fast & hard enough to damage certain bullet designs, and that would have obviously be an issue in those cases. Per the comments above, not all bullet designs are equal, and thinner jacket and softer core bullets may well have significant issues, where others would not.
- Like the bullet designs, not all barrel designs are created equal. The Rifling design could have a major impact on the changes/damage done to a bullet. A 1:8 barrel that has 4 grooves which are shallow/short with a angled edge may work perfectly fine, where a 1:8 barrel with 5 grooves which are tall with a 90 degree edge could result in damage.
- In addition to the twist rate and barrel design, the pressure/velocity could also be a significant factor. Firing a bullet at close to 65,000 PSI and 3,000 FPS could result in damage, where firing the same bullet at below 60,000 PSI and 2,850 FPS, may not result in any significant damage. The chance of bullet damage, is obviously proportional to the forces being applied against it.
- Barrel Length could also be a "contributing factor", in that a bullet may be fired "harder" with a faster burning powder out of a shorter barrel, or "easier" with a slower burning powder out of a longer barrel. Not sure that dwell time, or distance traveled, would be a major contributing factor by themselves?
IMHO, there is not a simple short answer as to whether a 1:8 will, or will not, work?
As far as any results the Army is experiencing, it is the Army, and having been there and done that, I wouldn't put it past them to be doing somethings they shouldn't, which may actually explain their results. Per my comments above, you would have to look at more than just the barrel twist rate to try and figure out why they are, or are not, succeeding?
As far as King of the 2 Mile, Fitzpatrick was actually shooting a Solid Bullet, so the issue of bullet change/damage was most likely not going to be a significant factor. However he was shooting well into the transonic/subsonic range, so stability was a major factor. Fitzpatrick had first (& second) round hits at 1,454 / 1,556 / 1,724 / 2,011 / 2,480. Litz was shooting a .338 with jacketed bullets, and he also had first round hits at 1,454 / 1,724 / 2,480. I will have to look when I get home to see if I can find the rifle specs, specifically the twist rates. My point in the King of 2 Mile reference, you don't make 1st round hits at those ranges if you don't have a very stable and predictable bullet flight path (among a lot of other things!) into the transonic/subsonic range. This was what was stressed at the Fall AB seminar, and it sounds like it is also being stressed to others.
Once again, I am just trying to put things out there, so when someone asks, "do I need a 1:10, 1:9, or 1:8", they hopefully know everything they need to be looking at to make that decision.
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GAP recently finished up my 300NM hunting build. This cartridge is freakishly accurate. This is a 5-shot group at 102y I shot this afternoon during load work up. 88gr of N570 under a 215. The wind was howling today - 25-30mph - so a little bit of horizontal. Time to stretch her legs!
Attachments
Those are some pretty good ES and SD numbers. How clean is the N570 for you? I saw someone else said it was dirty. How long is your barrel and I assume you are using 230 gr Bergers?
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N570 is a pretty dirty powder, but the added velocity is the trade off. Barrel is a 27" Bartlein 1-10 twist. I'm shooting 215gr Bergers.
I can't speak for the 300, but I shoot the 338 NM, which uses the same brass except for the neck-down. I'm on 6th loading with no evidence of any stress. I've really only had to trim a very few so far, but they're all going to need it soon.
Here's my 300 Norma MHSA just put together for me.
Bartlein 1:10, 28"
Defiance deviant
Kmw sentinel
Premier 5-25
This group was during load development on Sunday.
84.5 gr h1000
Berger 230 hybrid
. 025 off lands
3030 Avg fps (the five shot string from the picture)
SD: 9.6
Can't wait to get it out 2k+...
Bartlein 1:10, 28"
Defiance deviant
Kmw sentinel
Premier 5-25
This group was during load development on Sunday.
84.5 gr h1000
Berger 230 hybrid
. 025 off lands
3030 Avg fps (the five shot string from the picture)
SD: 9.6
Can't wait to get it out 2k+...
Attachments
anybody have the bullet length of the Hornady 225? shorter or longer than the 230OTM?
thank you sir, FWIW I am shooting 10.92 Rock Creek bbl with 230 @1100-2400ft with no problem. I have to remove the donot that developes as my throat isn't long enough to put out farther. 2900fps
Very interesting discussion on barrel twist rate for 300NM.
For what it's worth, before deciding final specs for my rifle, I knew I was going to give ABM 230gr Hybrid ammunition a try. Not knowing what barrel twist I should go with, I gave ABM a call.
To my surprise, their suggestion was a 1:10 twist.
I have 40 rounds through my Bartlien 26'' med palma and I'm seeing the same accuracy of .25moa at 100 yards as Lowlight is seeing. Trued velocity is 2940.
This spring the wind's have been very unfavorable for +700 yard accuracy testing here in the Texas Panhandle, but to 700 yard's, accuracy has been sub .4moa.
I don't plan to shoot ELR competion. My intentions with the rifle is some steel to 1200 yards to stay tuned up for long range hunting and the occasional shot to a mile for fun.
For my needs, 1:10 twist decision is working for me but I have no doubt a 1:9 would fit my program as well.
Sean
For what it's worth, before deciding final specs for my rifle, I knew I was going to give ABM 230gr Hybrid ammunition a try. Not knowing what barrel twist I should go with, I gave ABM a call.
To my surprise, their suggestion was a 1:10 twist.
I have 40 rounds through my Bartlien 26'' med palma and I'm seeing the same accuracy of .25moa at 100 yards as Lowlight is seeing. Trued velocity is 2940.
This spring the wind's have been very unfavorable for +700 yard accuracy testing here in the Texas Panhandle, but to 700 yard's, accuracy has been sub .4moa.
I don't plan to shoot ELR competion. My intentions with the rifle is some steel to 1200 yards to stay tuned up for long range hunting and the occasional shot to a mile for fun.
For my needs, 1:10 twist decision is working for me but I have no doubt a 1:9 would fit my program as well.
Sean
Well, i kept reading about the optimum twist. I got 2 nm both are 35* improved one is 30" shooting 3015fps with 230s barrel aint cheap so i dont do HYREV on load. If theres high and low node for every barrel i much prefer low node. Anyway this barrel is Broughton 1.9twist 5c ive shot her to a mile no prob. My other nm is 26" proof carbon and its a lighter version use for 75% hunting target here n there pus 215hybrida and 212 edl-x only becoz its what my other reamer intended for.. 8.4twist..i pre ordered another barrel as a spare after reading about the twist here.. I decided to do Broughton 5c 9.5" twist. Now i can go on and dnt need to wrry if i should keep reading the debate between 10 and 9*twist 
I took my 300 NM out to 1931 yards today for a test run. Its performance far exceeded my expectations! Unbelievably accurate at that range. I was able to achieve consistent impact strings with only wind effecting the hits (conditions were a little erratic 8-20+ mph) . Next outing I plan on going to 2500!
I also researched the barrel twist before my build. I found alot of contradictory results and was undecided on the result. I'm lucky enough to have a pretty good relationship with Mark Chanlynn so I picked his brain on the matter. His answer was similar to Lowlights. He advised me not to buy into the hype and go with the proven twist rate that would not change or damage the jacket at those velocities. He did recommend going 28" or more as well. In the end I'm very happy with the results!
I also researched the barrel twist before my build. I found alot of contradictory results and was undecided on the result. I'm lucky enough to have a pretty good relationship with Mark Chanlynn so I picked his brain on the matter. His answer was similar to Lowlights. He advised me not to buy into the hype and go with the proven twist rate that would not change or damage the jacket at those velocities. He did recommend going 28" or more as well. In the end I'm very happy with the results!
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DanHaley, I'm excited to watch your 300nm results. I have spent the last 3 years developing my skills with a custom 308 win. My son and I will be in the Black Rock desert next weekend shooting to 1200 hopefully. I feel that I have taken this caliber to the maximum potential so I have made a deposit on a 300nm build. My goal has been a mile since I started this project but maybe I have been thinking small. There is an ULR 2050 yard shoot in Lake County Ca that I planned on playing with but your results confirm this to be totally do-able. I look forward to watching your further results.
I have started accumulating the parts and pieces needed, including reloading stuff. Elk Meadows Performance is doing the build.
McMillan A5 with KMW cheek piece
Proof 26 or 28"
Timney Calvin Elite 2 lb
Elk Meadows Brake
Kahles 624i SKMR
230gr Berger
Rifles Only Sling
Undecided on bipod, dies (Redding Competition is what I currently use), and powder and primers. I would like to use Federal 215M but they seem impossible to get.
I picked up some of Litz ABM 230 and 215 to get started and for a source of brass. Midway is selling the 215s for $3.00 a round and with brass going $2.20 this seemed a no brainer. Any suggestions from the group is greatly appreciated.
I have started accumulating the parts and pieces needed, including reloading stuff. Elk Meadows Performance is doing the build.
McMillan A5 with KMW cheek piece
Proof 26 or 28"
Timney Calvin Elite 2 lb
Elk Meadows Brake
Kahles 624i SKMR
230gr Berger
Rifles Only Sling
Undecided on bipod, dies (Redding Competition is what I currently use), and powder and primers. I would like to use Federal 215M but they seem impossible to get.
I picked up some of Litz ABM 230 and 215 to get started and for a source of brass. Midway is selling the 215s for $3.00 a round and with brass going $2.20 this seemed a no brainer. Any suggestions from the group is greatly appreciated.
Just got mine late last year and haven't had much time for load development or fine tuning. I am loading the 208 gr ELD and getting 3150 fps over a charge of R33. Its not a hot load but the accuracy isn't fantastic yet either. Its just under MOA but it should get better with some tuning. New barrel and all I assume it should actually get a little faster. I wanted a load without too much pressure to try to make the barrel last a little longer and the ballistics on the 208 looked great with the BC of the new bullets. Almost everybody is running the 230 grain bullets so I thought I would add my two cents because you were asking specifically about the 208.
210 Berger performed way better for me than the 208Amax, FWIW...
I just had a 300 NM built. West Texas Ordnance completed the build and load work up yesterday. I have a 28" Krieger 1-10. I will use the 225 ELD Match with it. 
225gr Hornady ELD-M, 3.619" OAL
2.850" base to ogive
84.5grs Hodgdon H1000 Lot#5569
CCI 250 Primer
Norma brass(new)
3013FPS/4SD
The builder also provided an alternate load using 215 Berger
215 Berger Hybrid, 3.623" approx. OAL
2.847" Base to ogive
85.5grs H1000, lot #5569
CCI250 primer
3072FPS/5.7SD
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225gr Hornady ELD-M, 3.619" OAL
2.850" base to ogive
84.5grs Hodgdon H1000 Lot#5569
CCI 250 Primer
Norma brass(new)
3013FPS/4SD
The builder also provided an alternate load using 215 Berger
215 Berger Hybrid, 3.623" approx. OAL
2.847" Base to ogive
85.5grs H1000, lot #5569
CCI250 primer
3072FPS/5.7SD
Sent from my iPhone using Tapatalk
That's 2000 yards of fun right there! Make sure and report back after you've shot her.
I will let you know how it goes. I won't be able to shoot it for another couple months. I am out of town for work but plan to get it from the FFL as soon as I get back and probably straight to the range from there
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I just had a 300 NM built. West Texas Ordnance completed the build and load work up yesterday. I have a 28" Krieger 1-10. I will use the 225 ELD Match with it.
225gr Hornady ELD-M, 3.619" OAL
2.850" base to ogive
84.5grs Hodgdon H1000 Lot#5569
CCI 250 Primer
Norma brass(new)
3013FPS/4SD
The builder also provided an alternate load using 215 Berger
215 Berger Hybrid, 3.623" approx. OAL
2.847" Base to ogive
85.5grs H1000, lot #5569
CCI250 primer
3072FPS/5.7SD
Sent from my iPhone using Tapatalk
VERY Nice! The 300NM is an awesome round - you'll love it.
Is there a thread I can read referencing guys that went with 8 twist .30 cals and are having problems shooting them (accuracy)? Or, army info per Franks reference? Thanks in advance.
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230 grain?
Update to my post: After a trip to Colorado the barrel has settled in and this load is averaging 3120fps with an SD of 9.
What are the specs and weight on your 300 NM hunting rifle?
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McM A3 non-adjustable stock, GAP camo
Templar V2 long action, lefty (cause left hand is the right hand!)
Bartlien sendero contour 1-10" twist finished at 27" w/ Badger thruster MB
Badger M5 DBM - CIP length
Finished in GAP OD green
S&B 3-20 Ultra Short w/ H2CMR sitting in NF 6-screw rings
Rifle and scope: 12lbs
Otm 230 or hybrids? How far are you jumping them.. Whats your barrel length
Hybrid targets mate, jumping 0.02" and the rifle has a 28" barrel.
OK, I'm coming back to this thread as Manners mailed out my new stock on Friday! I can post a pic when I mate them this week, (PRE Cerakote) but I am settling back to the 210 Berger for Hunting
and looking for favorite loads and powder choices and speed at which the 210 Likes to sail at in 300NM of course..
26: rock 10.92 tw
guessing @ 3100fps or so?
any pet loads and speeds for the 210 Berger ?
and looking for favorite loads and powder choices and speed at which the 210 Likes to sail at in 300NM of course..
26: rock 10.92 tw
guessing @ 3100fps or so?
any pet loads and speeds for the 210 Berger ?
Are yall running standard mags or CIP mags?
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You can run a standard LA mag, but you will have more room to play with seating depth in a CIP. I run a standard LA with CIP mags.
Coming from a fellow lefty, please share some pics! A .300 Norma is my current project and finding left hand info for it is extremely difficult.
My gunsmith has been working on the 210 hunting VLD's for me for the upcoming hunting season.
I think his best accuracy load has been 86 grains of Retumbo and im guessing seating depth very close to lands. Our velocity is around 3100.
I'm running standard length mags. Had the barrel cut for Berger 230 hybrids and can load them to where the boat tail sits right at the bottom of the neck and have no issues fitting them in the mag.
I'll double check and get back to you on that.
On another note, took 'er out to 2331 yards today. Holy shit I love this round...
On another note, took 'er out to 2331 yards today. Holy shit I love this round...
I'm slow on posting a pic as I had to send the barreled action to Manners for its fitting in the mini chassis. Kind of like sending your wife off for her wedding gown lol !
Any word on savage or Remington making a 300 nm?
First two shots of the day was at 1250y. Can’t complain too much about that. Pushed out every 100y from there out to 1950, but mirage washed out the trace at about 1400y. Time to invest in a target camera.
Defiance action
Bix n Andy TacSport trigger
26” Proof research CF barrel
Fat bastard brake
Manners T4
Leupold MK8
230gr BHT
86gr retumbo
.02” jump
2954fps
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230 work best so for me too, nice shooting.
Nothing has changed about twist rate has it? Barrel inbound was supposed to be 1-9. Received 1-8. Figured Id check on the latest intel before sending it back.
Sounds like a good barrel to shoot the new 245 Bergers. I would keep it.
I think you are better off with the 8 twist using the heaviest bullets and solid projectiles, especially for ELR. Wish I had one.
Thanks for the info.
would there be any issues building a 300nm on a Rem 700 LA action?
Allready have a barreled(300wsm) rem 700 LA action(bluprinted) with a PT&G bolt, and it's time to test something new. the 300nm and 7mm practical is what interests me the most at the moment.
would save a few bucks, if i could reuse the action i allready have. planing a custom 6.5cm build this fall too, so saving some cash would be really nice.
Allready have a barreled(300wsm) rem 700 LA action(bluprinted) with a PT&G bolt, and it's time to test something new. the 300nm and 7mm practical is what interests me the most at the moment.
would save a few bucks, if i could reuse the action i allready have. planing a custom 6.5cm build this fall too, so saving some cash would be really nice.
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would there be any issues building a 300nm on a Rem 700 LA action?
Allready have a barreled(300wsm) rem 700 LA action(bluprinted) with a PT&G bolt, and it's time to test something new. the 300nm and 7mm practical is what interests me the most at the moment.
would save a few bucks, if i could reuse the action i allready have. planing a custom 6.5cm build this fall too, so saving some cash would be really nice.
Bolt face needs to be the same size as 338 LM
