6.5 PRC

BrentM said:
Yeah I see a min of 1k and 1500 on the 2 schools of thought. 1250 hits the middle. I also agree with it and believe high sectional density bullets have a better chance with deep penetration. A 6.5 prc running a 156 at 3000 hits 1372 at 1000 in my neck of the woods. That's not high elevation either. Step into high country and it's 1425. My prc's run short barrels so I'm not getting those speeds. 2920 in a 22" Puts it at 1337. My 18 at 2820 is 1213. I run 135's for wolf and they hit 1143. On paper it looks ok, but I'd not poke an elk at 1k with a 135 and likely not a 156 either. 999 maybe.
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If I'm going to shoot an Elk or moose beyond 600 yds, I'm going to use at least a 7mm or .30 Cal.

I want all the benefits of the heavier more energetic bullets.
 
BrentM said:
Hitting your target? So, why is that even a conversation. It's kind of a no sh!t Sherlock comment. Lots of calibers plenty capable of excellent accuracy at long range and it's well proven in many disciplines of shooting. I assume everyone knows that. It's all about terminal performance. Caliber can be included in that but shooting a .3 has nothing to do it being better or worse. Given of course you actually hit the target correctly .308 Cartridge is way under gunned for 1k and significantly less lethal than 6.5 PRC. The .3 arguement may have creditabilty if qualified with the proper data to show bullet weight, velocity, and design. Of course that is all related to terminal ballistics but I guess science doesn't count as long as it's .3 or bigger.
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When you shoot a lot at long range you will start to notice something. The BC number on the box does not tell the whole story. Heavier bullets get moved less in the wind and also have less vertical changes due to conditions. Take a bunch of rifles out to 1k or farther, shoot them on paper and get them zerod up. Take them back on multiple days without touching the scopes and just see how different days move the bullets around. Not just wind. The 300 grain 338 bullets are so solid you could go back to using a paper chart on your stock out to 1k. They dont get moved up and down on the target. Even the big 30s wont hang with that 300 grain bullet, even when I push them hard enough to theoretically be superior ballisticly. What Im saying is I dont care what the calculator says, a 6.5 is going to get moved too much at 1k and farther. Yes guys do it. But I shoot a ton at 1k and I wont. I wont even try it with a 7. If I HAD to do it, it would be a big 30 minimum or preferable a 338. Why? Because when you shoot enough you will learn that you cant do it every time at 1k, period. You just cant see all of the conditions and you WILL miss by a large enough margin to be bad. And you wont know why, you just could not see the condition.
 
The vertical you're seeing is likely aerodynamic jump... and it can be accounted for. If the wind switches from right to left, to left to right, by any margin at all, it will pull a vertical change. Once I understood that, making first round hits at distances beyond 1000yds became much easier with everything, but significantly so with smaller cals. When I compare the capabilities of my 338LM based cases to that of my 7mm Norma Mag Improved shooting 195EOL's at 3100+... not just on a calculator, but in the real world, I don't miss taking my .30cal or 338's out at all. I would feel MUCH more confident in my 7mm than 30 or 338cal in a 1000yd shot.

Most bullets in 6.5 just don't seem to handle conditions well compared to good bullets in other cals. Case in point, yesterday I had a customer here and we were forced to zero his rifle in some pretty rough conditions. 20mph 9:00-10:00 winds. At 100yds, I had to build in .2 mils of vertical and .3 mils of wind to counter the aerodynamic jump and crosswind. Once that was done, walking MOA targets out to 700 was no problem. This morning the wind is dead at 3mph... so we are going to confirm. I expect it to be very centered up.


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Yes if there is a wind shift you will have a vertical component to account for. But its not much if the changes are small. Im talking about daily conditions, like pressure. You can have very little wind out there and still see large vertical poi changes day to day. But the bullet with more mass, so long as its in the ball park of BC will handle it better. And if we could see every condition out to 1k none of it would matter. We could account for it all. So when you go out on that day with zero mirage and its dead calm at the shooting position but you miss by 2 moa because of the wind you had no way of knowing was there, that big 300 grain bullet is going to help you more. Your seeing it in the 6.5 because those bullets are light enough its more obvious I suspect. Then you can get on the topic of bullets. We shoot 1000s of 6mm bullets in 1k BR. They are mostly 103-108 grain bullets and are all splitting hairs when it comes to BC. But there are some that will cut the wind and there are others that will shoot big when its windy. Some designs handle the wind far better that others and the only way to know which ones they are is to shoot them against everything else at the same time. It does take hundreds of targets and some years to see the pattern but its undeniable. The same would apply to other bullets it would just be hard to pick them out without them being shot side by side on paper on a regular basis like we have done with the 6mms.
 
Aj and tail whip are common issues with smaller calibers and many get their info from match shooters who use 6mm and light 6.5 bullets. Most use a 140 6.5 for match for example. Also many are comparing a much higher bc bullet in a 30 or 338 cal. Tail whip etc are not nearly as big of an issue with the heavier 6.5's but there is a significant jump in bc to a 195 7 or 300 grain 338. As far as vertical in mountain terrain, there are not that many shooters who understand vertical wind component effect on dispersion as much as they should. Those bad shots are almost always vertical wind. Aj is part of that but most of it just knowing how the wind travels in the terrain and account for it. It is very common to pull .5-1 moa of vertical in mountain terrain simply due to the the direction of flow. The higher the bc the less affect it has. So shooting a massive bullet with a much higher bc is definitely going to decrease shooter error factor and partially make up for bad wind guessing.
 
Then we get into how much more difficult those big bullets are to handle in the NPA/recoil department. For most uninitiated shooters, that will be a big factor.
 
I was on the other side of this argument for a long time. The old 1k br shooters that shot the old school low bc 30 cal bullets would tell you that those heavy bullets would just move less and group better in the conditions than the lighter bullets of equal bc. I called BS, the weight of the bullet is part of the bc equation. So all that matters is bc and velocity. Well, as the years go on and I see more and more bullets shot side by side in the same conditions, I have seen it myself. They were right, I guess those guys that shot 1000s of targets learned a few things. Its just not something you will believe until you see it and even then maybe you wont believe your own eyes. But its kind of like vertical in your tune cutting the wind. Doesnt make sense either but it does.
 
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Alex Wheeler said:
I was on the other side of this argument for a long time. The old 1k br shooter that shot the old school low bc 30 cal bullets would tell you that those heavy bullets would just move less and group better in the conditions than the lighter bullets of equal bc. I called BS, the weight of the bullet is part of the bc equation. So all that matters is bc and velocity. Well, as the years go on and I see more and more bullets shot side by side in the same conditions, I have seen it myself. They were right, I guess those guys that shot 1000s of target learned a few things. Its just not something you will believe until you see it and even then maybe you wont believe your own eyes. But its kind of like vertical in your tune cutting the wind. Doesnt make sense either but it does.
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Bryan Litz has discussed, and conducted tests in this area that covers this topic in his publications with that prove out that heavier bullets of equal BC carry an advantage. He states the difference is slight, and only realized by what he classes as "elite" shooters. This is consistent with those "old school" bench-rest shooters observations that you describe, as well as your own observations.
 
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.
 
Greyfox said:
Bryan Litz has discussed, and conducted tests in this area that covers this topic in his publications with that prove out that heavier bullets of equal BC carry an advantage. He states the difference is slight, and only realized by what he classes as "elite" shooters. This is consistent with those "old school" bench-rest shooters observations that you describe, as well as your own observations.
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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.
 
BrentM said:
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.
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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 for lunch at 1k when its windy. Not just less drift by a good margin but the groups stay together much better.
 

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