24hourcampfire.com
24hourcampfire.com
Previous Thread
Next Thread
Print Thread
Hop To
Page 1 of 3 1 2 3
Joined: Apr 2010
Posts: 14,634
S
Campfire Outfitter
OP Offline
Campfire Outfitter
S
Joined: Apr 2010
Posts: 14,634
Oft times we read articles whereby the author of whatever talks about a particular bullet or cartridge not being accurate because it can't remain supersonic throughout the distance to the target as it goes into the transonic stage...the bullet gets 'squirrelly' and accuracy suffers! One example of this is in years past when working the pits we could always tell who the Service Rifle shooters were when shooting 1000 yards because oft times the 168 gr. Sierra bullet being used would keyhole into the target paper! That bullet was NEVER designed as a long range bullet in the first place, however it set world records over many years in 300 meter matches! It had a 13 degree boat-tail and any bullet with that design has the same drag function as a flat-based bullet.

Now...here's some food for thought! The below photo is of a metal Creedmoor Target I had made a few years ago when I was heavy into shooting Sharps rifles using paper patched all lead bullets that I cast. There is a smaller plate inside the larger. Small plate is 20" diameter...larger bull is 44" diameter...same size as the Palma target. Ten ring is the 20" plate. I had this target made because when shooting from 1000 yards the bullet impacts stood out like a five carat diamond in a Billy goats ass in my spotting scope. I was testing a new load in my 50/90 Sharps using a 720 gr. paper patch bullet ahead of 116 grs. KIK 2F blackpowder using Russian primers. I wanted to see how the load held up for possibly giving a low vertical dispersion. Muzzle velocity of this load was around 1380 fps so it shouldn't take a rocket scientist to figure that this bullet was already below super-sonic at around 250 yards...or less! After a first round hit on the ten ring plate I made no adjustment for windage correction as the conditions were good with only slight wind and since I was testing for vertical....not a problem! Had I made a correction probably all ten rounds would have been within the ten ring plate. A measurement showed a 7.5" total vertical for all ten rounds!

So....in the final analysis...the question is why was the accuracy this good using a 125 year old bullet design using an out-dated propellent, moving at this below supersonic speed??? Another question is.....is all the talk about 'going into the transonic stage causing inaccuracy' just so much BS??

[Linked Image]1000 yards 50/90 PP by .com/photos/61286670N08/]Sharps Man, on [bleep]


Even birds know not to land downwind!
BP-B2

Joined: Mar 2007
Posts: 2,461
D
Campfire Regular
Offline
Campfire Regular
D
Joined: Mar 2007
Posts: 2,461
I don't have near as much experience as you do, but I'm going to say it depends. The 175 SMK seems to transition through that velocity range pretty well. We shot quite a bit at extended ranges with M24's and 118LR before I retired.

On the other hand I was shooting at ground squirrels one afternoon with 6.5 139 gr Lapua Scenars and after barely missing one a couple of time at about 1350 I saw one a ways out further.

Long story made short my shots hit all over the place. I went back to where the closer one had been sitting on a rock and was able to hit the rock repeatedly.

Rifle is a Surgeon Action with a Krieger 1 and 8 twist Heavy Varmint Taper. I've killed a bunch of prairie dogs between 800 and 1150 yards with that rifle.

Joined: Apr 2010
Posts: 14,634
S
Campfire Outfitter
OP Offline
Campfire Outfitter
S
Joined: Apr 2010
Posts: 14,634
Originally Posted by dodgefan
I don't have near as much experience as you do, but I'm going to say it depends. The 175 SMK seems to transition through that velocity range pretty well. We shot quite a bit at extended ranges with M24's and 118LR before I retired.

On the other hand I was shooting at ground squirrels one afternoon with 6.5 139 gr Lapua Scenars and after barely missing one a couple of time at about 1350 I saw one a ways out further.

Long story made short my shots hit all over the place. I went back to where the closer one had been sitting on a rock and was able to hit the rock repeatedly.

Rifle is a Surgeon Action with a Krieger 1 and 8 twist Heavy Varmint Taper. I've killed a bunch of prairie dogs between 800 and 1150 yards with that rifle.


OUTSTANDING!!

grin grin grin


Even birds know not to land downwind!
Joined: Mar 2007
Posts: 2,461
D
Campfire Regular
Offline
Campfire Regular
D
Joined: Mar 2007
Posts: 2,461
Not Centerfire, but I'm almost positive I remember reading that the reason 22LR match ammo is subsonic is because the transition through the sound barrier made the high velocity stuff slightly less accurate. I can't remember when or where I read that. Probably some gun rag in the early 90's.

Joined: Jul 2003
Posts: 1,444
Campfire Regular
Offline
Campfire Regular
Joined: Jul 2003
Posts: 1,444
Quote
So....in the final analysis...the question is why was the accuracy this good using a 125 year old bullet design using an out-dated propellent, moving at this below supersonic speed??? Another question is.....is all the talk about 'going into the transonic stage causing inaccuracy' just so much BS??


I don't have an answer to your question, but I have more questions for you;

We know about the 308, 168 Sierra 1000 yard trans sonic situation because of the M14 being used in Long Range Rifle competition. There was a convergence of different factors that made the transition observable. A) a rifle/cartridge/bullet combination that had a bullet going subsonic over B) pits with human observers to capture the phenomenon. How would us mere mortals know when a bullet was going subsonic without target pullers beneath the subsonic bullet or the resources of BRL Aberdeen to track these bullets going downrange? Could it be that other bullets are having similar instability issues, but it is going unnoticed because it is so far downrange beyond the benefit of a target with pits? Could dodgefan's 6.5mm anecdote be one such example?

With that said, I have heard that the 30 cal 173 M1 design bullets and it's offspring 175 Match King make the transition with stability as well as Berger's juggies. I've also heard that BPCR rounds do it without problem (those projectiles probably have a tremendous Stability Factor by virtue of their lack of zoot form factors). BTW, I've been in the pits with 405gr 45-70 bullets being fired at the 600 yard line. The steep downhill trajectory had us hugging the pit wall as they rained down on the pit roof. I don't care to do that again.


Last edited by ChrisF; 02/08/19.
IC B2

Joined: Apr 2004
Posts: 3,450
C
Campfire Tracker
Offline
Campfire Tracker
C
Joined: Apr 2004
Posts: 3,450
I quess one of the folks I`d like to talk to about the accuracy issue going from SS to sub-sonic would be Mark, from MarkandSam after work here on u-tube. He talks a lot about bullet design and it`s efficency at ELR. tho does not go into exact detail, but has found bullet designs that work extreamly well.
Brian Luts should also be a great source.
I`ve also thought of the problems Yeager and the Bell engineers faced in breaking the sound barrier,..going SS right, as simular The buffiting Yeager experienced in the plane...could suggest a bullet may do the same...at that point in it`s flight...causing inaccuracy beyond? They fixed it by a slight change in design.
Interesting topic tho...maybe someone with answers will chim in.

Wonder if there is a wind tunnel for testing bullet design?

Joined: Jul 2003
Posts: 1,444
Campfire Regular
Offline
Campfire Regular
Joined: Jul 2003
Posts: 1,444

Last edited by ChrisF; 02/08/19.
Joined: Apr 2010
Posts: 14,634
S
Campfire Outfitter
OP Offline
Campfire Outfitter
S
Joined: Apr 2010
Posts: 14,634


Even birds know not to land downwind!
Joined: Mar 2007
Posts: 2,461
D
Campfire Regular
Offline
Campfire Regular
D
Joined: Mar 2007
Posts: 2,461
ChrisF and Sharpsman thanks for those articles they were all well worth reading IMO.

Joined: Apr 2004
Posts: 3,450
C
Campfire Tracker
Offline
Campfire Tracker
C
Joined: Apr 2004
Posts: 3,450
Yea....found the same ones..

IC B3

Joined: Jul 2003
Posts: 1,444
Campfire Regular
Offline
Campfire Regular
Joined: Jul 2003
Posts: 1,444
Nice find! I was a member of ASME around that time! (Even got the t-shirt) ...and I don’t remember that newsletter.
FWIW, Bob McCoy did his work on documenting the flight characteristics of the 168 SMK at BRL. His book “Modern Exterior Ballistics” contained some good 168 specific research complete with spark shadow graphs...and my recollection was that he dissected the 168 transonic instability in detail there.

Last edited by ChrisF; 02/08/19.
Joined: Apr 2010
Posts: 14,634
S
Campfire Outfitter
OP Offline
Campfire Outfitter
S
Joined: Apr 2010
Posts: 14,634
I was 'gifted' with the situation to have had several conversations with Bob McCoy over a ten year period. The first occasion was when I talked with him about what profile/design I should have my bullet making dies made? Bob advised that I should have them made with a rebated boat-tail and when I asked him why?? that design he told me that everything he had fired through the spark graph range with a rebated boat-tail had shown a minimum of a 5% increase in performance over the standard boat-tail configuration! That doesn't sound like much but in the case of having to make a 'shoot off'....a 5% increase in X count wins the pot!! I had Bob Simonson up in Michigan make my dies and I wore myself out over a ten year period making bullets of a specific design for shooting in the M14 as no manufacturer at that time was making a good match bullet for Service Rife shooters competing in NRA High-power events. Most shooters in the Service Rifle Class were tied to the Sierra 168 gr. HPBT which oft times, due to lack of adequate BC and muzzle velocity at 1000 yards would 'key-hole' into the target paper. The Sierra 168 bullet has a 13 degree tapered BT and Bob advised that any bullet with that degree of boat-tail had the same drag function as a flat-based bullet.

We lost a good guy when Bob was called home!! frown shocked


Even birds know not to land downwind!
Joined: Nov 2006
Posts: 3,640
B
Campfire Tracker
Offline
Campfire Tracker
B
Joined: Nov 2006
Posts: 3,640
Several years ago I built a rifle to see how far away I could shoot a Varmint and how far away I could shoot a target, I won't go into all the details but the bullet was a .338 Sierra 300gr Match King. It was very accurate out to 2144 yards on a rock chuck (my longest kill ever) but this bullet went transonic at 2300 yards...........at 2400 yards all accuracy was lost and would not hit a target of any size except the side of a mountain.

Joined: Apr 2005
Posts: 30,811
J
Campfire 'Bwana
Online Sleepy
Campfire 'Bwana
J
Joined: Apr 2005
Posts: 30,811
Originally Posted by boatanchor
Several years ago I built a rifle to see how far away I could shoot a Varmint and how far away I could shoot a target, I won't go into all the details but the bullet was a .338 Sierra 300gr Match King. It was very accurate out to 2144 yards on a rock chuck (my longest kill ever) but this bullet went transonic at 2300 yards...........at 2400 yards all accuracy was lost and would not hit a target of any size except the side of a mountain.


I’d be willing to wager that a faster twist would have transitioned the change from Super sonic to subsonic.



I got banned on another web site for a debate that happened on this site. That's a first
Joined: Nov 2006
Posts: 3,640
B
Campfire Tracker
Offline
Campfire Tracker
B
Joined: Nov 2006
Posts: 3,640
That could possibly be a valid point, it could also be possible that going to a faster twist could negatively effect accuracy. At this point it's not worth the price of a new barrel to find out. but interesting to ponder confused

Last edited by boatanchor; 02/09/19.
Joined: Jul 2003
Posts: 1,444
Campfire Regular
Offline
Campfire Regular
Joined: Jul 2003
Posts: 1,444
Quote
Bob advised that I should have them made with a rebated boat-tail and when I asked him why?? that design he told me that everything he had fired through the spark graph range with a rebated boat-tail had shown a minimum of a 5% increase in performance over the standard boat-tail configuration! That doesn't sound like much but in the case of having to make a 'shoot off'....a 5% increase in X count wins the pot!!

Sharpsman, I've seen you recount this story several times on various sites. Can you help me understand this statement. What metric was McCoy referring to in that 5% increase in performance?
Do you have any samples of your 176 Delta's that you can share a photo of? I'm curious what they look like.

On a different note, I am pretty sure that your 176's did not drive Sierra to produce their 175's. It was actually PWS wanting an analog to the 173 FMJ for what ultimately became M118LR.

Joined: Apr 2005
Posts: 30,811
J
Campfire 'Bwana
Online Sleepy
Campfire 'Bwana
J
Joined: Apr 2005
Posts: 30,811
Originally Posted by boatanchor
That could possibly be a valid point, it could also be possible that going to a faster twist could negatively effect accuracy. At this point it's not worth the price of a new barrel to find out. but interesting to ponder confused


Brian Lietz shoots a 9 twist 308 at 1000yards with 210;grain bullets. Brian says that a faster twist gives a tighter spin to the bullet and a higher BC and at long range produces better accuracy.



I got banned on another web site for a debate that happened on this site. That's a first
Joined: Nov 2006
Posts: 3,640
B
Campfire Tracker
Offline
Campfire Tracker
B
Joined: Nov 2006
Posts: 3,640
Originally Posted by jwp475
Originally Posted by boatanchor
That could possibly be a valid point, it could also be possible that going to a faster twist could negatively effect accuracy. At this point it's not worth the price of a new barrel to find out. but interesting to ponder confused


Brian Lietz shoots a 9 twist 308 at 1000yards with 210;grain bullets. Brian says that a faster twist gives a tighter spin to the bullet and a higher BC and at long range produces better accuracy.


That is interesting, Bryan Litz has also stated that the correct twist rate for a given bullet is optimal for accuracy and that unnecessarily high rpm can be detrimental.
This was in the pre-Berger bullet days...he might have changed his mind or the Brian Lietz you mention could be a different person entirely.

Last edited by boatanchor; 02/10/19.
Joined: Mar 2006
Posts: 14,435
Campfire Outfitter
Online Content
Campfire Outfitter
Joined: Mar 2006
Posts: 14,435
Bullets are better these days. Accuracy issues from over-stabilizing imbalanced bullets is not much of a problem anymore, unless you’re competing in SR BR, and 0.020” added to your group size can make or break you.

Bryan has given a more current statement of the effects of twist on accuracy, with experimental support, in his book “Modern Advancements in Long Range Shooting”, Vol 1.

Joined: Nov 2006
Posts: 5,796
Campfire Tracker
Offline
Campfire Tracker
Joined: Nov 2006
Posts: 5,796
Let's look at this idea closer. If you shoot a 300 gr bullet at 10/1 rifling ratio or at 9/1 ratio. It only gains 2 rpm over the length of a rifle. You really think that one extra rpm is gonna change much? Enlighten me on this? Once an rpm is reached to stabilize a bullet its done its job,yes no?

Last edited by 378Canuck; 02/10/19.

It is better to be judged by 12 than to be carried by 6.
Page 1 of 3 1 2 3

Moderated by  RickBin 

Link Copied to Clipboard
YB23

Who's Online Now
677 members (16Racing, 1234, 163bc, 06hunter59, 09wingates, 77 invisible), 2,658 guests, and 1,220 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums81
Topics1,187,608
Posts18,398,386
Members73,817
Most Online11,491
Jul 7th, 2023


 







Fish & Game Departments | Solunar Tables | Mission Statement | Privacy Policy | Contact Us | DMCA
Hunting | Fishing | Camping | Backpacking | Reloading | Campfire Forums | Gear Shop
Copyright © 2000-2024 24hourcampfire.com, Inc. All Rights Reserved.
Powered by UBB.threads™ PHP Forum Software 7.7.5
(Release build 20201027)
Responsive Width:

PHP: 7.3.33 Page Time: 0.355s Queries: 14 (0.004s) Memory: 0.9037 MB (Peak: 1.0714 MB) Data Comp: Zlib Server Time: 2024-03-28 14:07:52 UTC
Valid HTML 5 and Valid CSS