6.5 PRC

[orkan]

To further this, I typically find that among bullets in roughly the same weight, and roughly equal BC... are much better in a smaller caliber than they are in the larger caliber. Though most often that same weight in the smaller caliber, will be accompanied by a BC improvement. This would seem obvious at this point in the discussion, but it's a fairly important distinction.



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[BrentM]

I can give you one example of the difference. I wish I had this target still. Now I dont know what "scientific data" is published but at one time Litz argued this was not true. That BC was it and weight was factored in. I also dont wear a double mask to drive in my car alone . So Im not too worried about the "science" just because its in a book. It was argued tune has no effect on bc too, but we know it does. Some guys use it as part of the tuning process.

The target Im talking about was a good example of how much it matters. A friend of mine had his light and heavy br rifles at our range. Our range doesnt switch much, its usually a l to r push that varies in intensity. His 6mm is possibly the best 6mm theres ever been, 8 records fell last year to it. It shot a 5 shot group about 12" wide, a "weather report" we call it. Vertical was good but the wind killed it. Same condition his 30 shot a 3.7" round 10 shot group. You would have guessed there was no wind at all by looking at the group. It also took 1 moa less to center up on the target. The 6mm is a custom bullet, about .550bc at 3030 fps. The 30 was a 185 Berger .555 bc closer to 3000 fps.

Now your typical heavy gun is more likely a 300 wsm running a 210 vld at 2800-2850. Thats a 620 bc and it will eat that 550 bc at 3030 fps lunch at 1k when its windy. Not just less drift by a good margin but the groups stay together much better.

Interesting intel for sure. That deviation in result seems extreme to me. Almost triple the affect for the similar BC which goes against the science. If it is repeated over multiple sessions with the same deviation I'd buy off on it. Me being the pessimist I am, I'd have to look at all the data (sd, es, wind deviation, etc) to be convinced that some how the mere weight of a bullet had almost 3x the effect at a 1k. I do understand your passion for the result since you were the one looking at it and I would be no different. I will have to play with this process this summer as I have a 1550 target going up on the range. It will be quite tricky as that location experiences 3 wind changes and 2 draft changes. I think it will be a good 300 norma vs a 6.5 PRC test. That is if I can stand to shoot that norma that much. Ha ha

 

[BrentM]

To further this, I typically find that among bullets in roughly the same weight, and roughly equal BC... are much better in a smaller caliber than they are in the larger caliber. Though most often that same weight in the smaller caliber, will be accompanied by a BC improvement. This would seem obvious at this point in the discussion, but it's a fairly important distinction.



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Generally in the smaller caliber that equal weight bullet is longer. I cannot remember the term but the length helps stabilize the bullet. I can't remember if it yaw repose or something like that.

 

[Greyfox]

Thats interesting, that must be something relatively new. It used to get argued. Got a link to it or is it in one of the ab books? But one thing I would say is its more than slight. Well, I guess it depends on the definition of slight.

It's in the same book as the wez section I believe. It is not nearly as big of a deal as some people make it to be, but there is an advantage no doubt. ELR is an example. But we're talking 1000, which is not really that far. The bigger issue is whether people are fully understanding the 3 principles of ballistics well enough to separate out the effects. In the end accredited and published scientific data are hard to argue against. However we all want to believe what we want to believe. I believe atmospheric conditions have a similar affect on bullets of equal bc regardless of weight.

Alex- Bryan published a few books on LR Shooting/ Ballistics back about a dozen years ago. Well worth a read. IMO…He does a decent job at trying to verify or bust some of the conventional wisdoms by actual shooting and analyzing objective data. Photo of one if his publications below.

Brent- I agree. For game hunting out to 1000 yards or a bit more, I'm passing or attempting to move in closer if I'm not fully confident in my wind determination. If the wind speed gets to much above 5MPH, and I'm suspecting compound effects, the red flag goes up. On the occasions when I had a heavier/larger caliber bullet it really didn't influence my go/no-go decisions for the distances and vital areas I'm dealing with. For targets/steel, anything goes, and while I may seen less effects with the larger, comparable or higher BC calibers, they are not material enough to split my decision on the long shots at the medium sized game I predominately hunt. Perhaps my skill level needs some more work……

 

[orkan]

Generally in the smaller caliber that equal weight bullet is longer. I cannot remember the term but the length helps stabilize the bullet. I can't remember if it yaw repose or something like that.

Case in point, I run a ton of 55gr berger in a .20-223AI. The hit percentage on that vs a 55gr bullet in .223AI is astonishing. The .224 55gr bullet has a massively lower BC. So to get the BC of the 55gr in .20cal, but in .22cal... I would have to go to a 73gr berger. The launch velocity of the 55gr .20cal is WAY higher than I can push that 73gr .22cal in an equally sized case.

What I think is being discussed here, is if the 55gr berger and 73gr berger with near equal BC's were pushed to the same speed, then the 73gr would enjoy some benefit due to its sheer weight advantage. On this point I would agree, marginally. However, if the thought exercise continues... why wouldn't I choose an even heavier bullet with intrinsically higher BC in the larger caliber and enjoy an even better result... which is almost always going to be available? The only reason I can think of would be some very specific square range disciplines.

So I hope no one reading this thread thinks all they need to do is go up in caliber and experience benefit. You can accomplish literally the same thing by pushing a heavy-per-caliber bullet in a smaller caliber, faster. Obviously the 55gr berger .20cal is somewhat of an anomaly, as you typically won't see as huge of a performance swing... but it is possible. Especially with the prevalence of the 156EOL in 6.5mm. Generally speaking, moving up in caliber, will bring a massive BC jump as well. So it is a given that weight will tend to come along with that. While you can select lower BC options in that next higher caliber, it's generally advisable to choose the heaviest bullet with the highest BC that your particular case size can accommodate to reach the performance you're after.


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[BrentM]

Alex- Bryan published a few books on LR Shooting/ Ballistics back about a dozen years ago. Well worth a read. IMO…He does a decent job at trying to verify or bust some of the conventional wisdoms by actual shooting and analyzing objective data. Photo of one if his publications below.

Brent- I agree. For game hunting out to 1000 yards or a bit more, I'm passing or attempting to move in closer if I'm not fully confident in my wind determination. If the wind speed gets to much above 5MPH, and I'm suspecting compound effects, the red flag goes up. On the occasions when I had a heavier/larger caliber bullet it really didn't influence my go/no-go decisions for the distances and vital areas I'm dealing with. For targets/steel, anything goes, and while I may seen less effects with the larger, comparable or higher BC calibers, they are not material enough to split my decision on the long shots at the medium sized game I predominately hunt. Perhaps my skill level needs some more work……
View attachment 352472

Yepper, mountain terrain wind is about the only thing holding back a shot op on game. I've been chasing a couple different packs of wolves in some weird open mountain terrain lately and I see a lot of coyotes out there as well. They range 1100-1400 and my hit ratio is not nearly where I need it to be. The misses are incredibly close but misses nonetheless. I know dang well those misses have nothing to do with that rifle or caliber choice. I am the weak link for sure and dialing in that aj and vertical wind component at those ranges is my current focus. It helps me with the sub 1k coyotes as I am not discounting anything as a give me shot. Account for it all or get closer. I am not going to grab a bigger caliber thinking it's going to make up for my lack of skill.

 

[WildRose]

... and aerodynamic jump affects the lower BC bullets significantly more than those with higher BC's.



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That's one of the more frustrating aspects of high desert or high plains hunting.

We have LOTS of wind year round and a lot of big wind anytime a front is approaching or receding.

I don't notice much of an effect under 300yds, but when shooting directly into the wind bullets tend to want to ride high despite all your data.

 

[WildRose]

Yepper, mountain terrain wind is about the only thing holding back a shot op on game. I've been chasing a couple different packs of wolves in some weird open mountain terrain lately and I see a lot of coyotes out there as well. They range 1100-1400 and my hit ratio is not nearly where I need it to be. The misses are incredibly close but misses nonetheless. I know dang well those misses have nothing to do with that rifle or caliber choice. I am the weak link for sure and dialing in that aj and vertical wind component at those ranges is my current focus. It helps me with the sub 1k coyotes as I am not discounting anything as a give me shot. Account for it all or get closer. I am not going to grab a bigger caliber thinking it's going to make up for my lack of skill.

If you're shooting coyotes a those ranges successfully my hat is off to you.

I've gotten a few kills with the STW an Rum between 800-1,000yds on coyotes so I know how hard it is.

Even with good glass a coyote past a thousand looks about the size of a cotton tail at 200.

 

[BrentM]

That's one of the more frustrating aspects of high desert or high plains hunting.

We have LOTS of wind year round and a lot of big wind anytime a front is approaching or receding.

I don't notice much of an effect under 300yds, but when shooting directly into the wind bullets tend to want to ride high despite all your data.

AJ section of the litz book addresses this as well as strelock and AB solutions. Head wind increases drag slightly as the bullet has to push into it. What I believe to be happening is bullet angle to the wind tends to give rise. If you think about the issue via an illustration the bullet is actually launched in upward angle to arch back down to the target. The longer the distance the more initial angle and therefore the more influence the wind has on the underside of the bullet. Ground affect is another potential issue with plains shooting. Heat rising, mirage, and vertical effect can influence of impact point. Any rise at all in the terrain will have a vertical affect. I have this issue at our range. There a small rise at 550-600 and that **** thing will push a bullet a full MOA high at 1k with 7-10 mph winds.

 

[BrentM]

If you're shooting coyotes a those ranges successfully my hat is off to you.

I've gotten a few kills with the STW an Rum between 800-1,000yds on coyotes so I know how hard it is.

Even with good glass a coyote past a thousand looks about the size of a cotton tail at 200.

I've killed 9-10 from 850-1300 in the past 2 seasons. I killed 3 2 weekends ago at the same area at 850, 925, 999. I missed the 850 on the first shot and then spined it the 2nd. I had to finish it when rolled off the mountain into the bottom at 650. Not very proud of all that. The others were clean kills since I then was aware the updraft on that side of the mountain was greater than I believed it to be. Same area the weekend before I took off .7 moa for a 1399 wolf which was a mistake and wish I had it on film. Sprayed that thing with snow and ice and maybe bullet shrapnel. I took off too much as once again I misread the updraft read This area is kicking my *** for wind calls. Its very humbling and intimidating as I believe it should be easy to understand. Monday I was hunting with a highly successful LR competitor in a different area and shot 850 and 1145 for first round impacts. Moved to another area and thought the wind here is weird, time to shoot and train, impact was a little high at 990, didn't account for the vertical like I should. After that we discussed what he would have done etc. Good lesson.

 

[WildRose]

I've killed 9-10 from 850-1300 in the past 2 seasons. I killed 3 2 weekends ago at the same area at 850, 925, 999. I missed the 850 on the first shot and then spined it the 2nd. I had to finish it when rolled off the mountain into the bottom at 650. Not very proud of all that. The others were clean kills since I then was aware the updraft on that side of the mountain was greater than I believed it to be. Same area the weekend before I took off .7 moa for a 1399 wolf which was a mistake and wish I had it on film. Sprayed that thing with snow and ice and maybe bullet shrapnel. I took off too much as once again I misread the updraft read This area is kicking my *** for wind calls. Its very humbling and intimidating as I believe it should be easy to understand. Monday I was hunting with a highly successful LR competitor in a different area and shot 850 and 1145 for first round impacts. Moved to another area and thought the wind here is weird, time to shoot and train, impact was a little high at 990, didn't account for the vertical like I should. After that we discussed what he would have done etc. Good lesson.

My mentor Homer Johnson is without the most talented shooter I've ever known. I routinely watched him make shots anyone would have called impossible at ridiculous ranges.

One day I asked him how he could do that.

His answer was in the simplest terms a man can use, "By missing a lot and learning from them".

For the rest of my life that princple has been burned into my brain and proven to be 100% true.

You're not going to make those shots until you've missed a lot of them and learned from them.

You should be very proud of what you've been able to accomplish.

 

[Alex Wheeler]

Alex- Bryan published a few books on LR Shooting/ Ballistics back about a dozen years ago. Well worth a read. IMO…He does a decent job at trying to verify or bust some of the conventional wisdoms by actual shooting and analyzing objective data. Photo of one if his publications below.

Brent- I agree. For game hunting out to 1000 yards or a bit more, I'm passing or attempting to move in closer if I'm not fully confident in my wind determination. If the wind speed gets to much above 5MPH, and I'm suspecting compound effects, the red flag goes up. On the occasions when I had a heavier/larger caliber bullet it really didn't influence my go/no-go decisions for the distances and vital areas I'm dealing with. For targets/steel, anything goes, and while I may seen less effects with the larger, comparable or higher BC calibers, they are not material enough to split my decision on the long shots at the medium sized game I predominately hunt. Perhaps my skill level needs some more work……
View attachment 352472

I have one of his early books, but none of the recent stuff.

 

[Alex Wheeler]

Interesting intel for sure. That deviation in result seems extreme to me. Almost triple the affect for the similar BC which goes against the science. If it is repeated over multiple sessions with the same deviation I'd buy off on it. Me being the pessimist I am, I'd have to look at all the data (sd, es, wind deviation, etc) to be convinced that some how the mere weight of a bullet had almost 3x the effect at a 1k. I do understand your passion for the result since you were the one looking at it and I would be no different. I will have to play with this process this summer as I have a 1550 target going up on the range. It will be quite tricky as that location experiences 3 wind changes and 2 draft changes. I think it will be a good 300 norma vs a 6.5 PRC test. That is if I can stand to shoot that norma that much. Ha ha

Thats one example, and it only took one more minute to center up. So it didnt get blown that much more maybe a 1/4 to 1/3 more but that bullet got beat up more in the turbulence. This 2 fold, the heavies will move less all else equal. And some bullet designs will still group in bad conditions while other shoot a blob. Id guess youd call them fair weather bullets.
We see this all the time and have for years. I also score the 1k BR targets at the deep creek matches. I will get 8 targets shot in the same conditions and many times you will see a tiny group with strung out groups on both sides of him. Most BR shooters in this game will shoot when the commence fire is given and will run the group as quick as possible. Your never going to see what I am talking about unless your in an environment where thats happening. Multiple bullets fired at the same time and on paper targets from well tuned rifles.
Probably have gotten far enough off topic and I do not expect anyone to believe this, nor do I care. But I still dont think 6.5 and 1k elk belong in the same sentence.

 

[orkan]

But I still dont think 6.5 and 1k elk belong in the same sentence.

I agree. … but I don't agree that applies to 7mm.