High BC but slow FPS vs. faster, lower BC bullet question

[Basic user]

Having to choose between say, Bergers 153 and their 140 in the 6.5cm; The heavier bullets have a higher bc but the 140 will get to the target sooner. I know shot group size kind of trumps most every other attribute but which attribute here helps with bucking the wind at a 1000 better, the BC advantage of the 153 or the shorter time of flight of the 140?
Anyone try both at a grand?

 

[BobinNC]

Perhaps this can help:

Form Factors: A Useful Analysis Tool

Looking over Berger's BC Form Factors the lowest BC Form Factor is held by the 6.5 mm 144 gr LR Hybrid Target @ 0.879. From that theoretical standpoint, that would the one I'd choose if I was looking for the "best" 6.5 CM bullet for long range.

The 144 gr LR Hybrid should deliver the best combination of both wind bucking and velocity of all Berger's 6.5mm lineup.

 

[Doom]

You can use a ballistic calculator yourself to see what the difference will be. Try JBM own the internet.

 

[Basic user]

Will do.

 

[CK1.0]

JMHO but if this is for long-range I wouldn't worry about which one will buck the wind better...

Of course, we all want first-round impacts. But the real name of the game is making good corrections, and for most of us, more feedback downrange (more splash, and/or being able to tell which way a plate rocked) makes that easier. So, in general, bigger is better for that. Not to mention the benefits that more time of flight and/or being able to use a smaller powder charge may add to the equation.

Speed means nothing IMO. A rifle can be just as accurate at 2550fps as it can be at 2750fps, it's almost always the monkey pulling the trigger that matters the most and makes the biggest difference.

 

[supercorndogs]

Speed makes a diffrence when choosing a bullet. There is a reason most shoot 155-178 range in the 308, and thats because it's tough to get a 215 or 220 bullet going fast enough to take advantage of the extra BC. A lot times the lighter bullets will out perform the heavier ones for 600y or so due to the extra velocity.

put them in a Calc, look at the wind at the distances you plan to shoot. If you are worried about how hard they hit the target look at energy too. Most calcs will list enegery.

I know have seen lowlight post "light is right." I think a lot of guys are finding the advantages of a lighter bullet going faster.

 

[Basic user]

Yea I hear that; I'm guessing that's why Palma guys push a 155 grainer as fast as possible. Is that because theres more advantage ballistically? Or was that because that's just the mandated weight and that's the rule?

 

[Basic user]

Perhaps this can help:

Form Factors: A Useful Analysis Tool

Looking over Berger's BC Form Factors the lowest BC Form Factor is held by the 6.5 mm 144 gr LR Hybrid Target @ 0.879. From that theoretical standpoint, that would the one I'd choose if I was looking for the "best" 6.5 CM bullet for long range.

The 144 gr LR Hybrid should deliver the best combination of both wind bucking and velocity of all Berger's 6.5mm lineup.

I actually just shot a batch of those, and they dont group as wel, though I just loaded one ladder. I should keep experimenting with those then eh?

 

[spife7980]

Yea I hear that; I'm guessing that's why Palma guys push a 155 grainer as fast as possible. Is that because theres more advantage ballistically? Or was that because that's just the mandated weight and that's the rule?

US palma can use whatever, international palma rule is <156

 

[Basic user]

I see. What does the US Palma team shoot then? If we want to compete internationally, do we practice with the 155s?

 

[Guns&WhiteWater]

I know have seen lowlight post "light is right." I think a lot of guys are finding the advantages of a lighter bullet going faster.

Greater speed is always better than a lesser speed for reducing time of flight (within reasonable BC's), but there is a speed threshold where a higher BC bullet starting off slower will trump a lower BC bullet starting out with more velocity at distance. This threshold will also change as distance changes.

 

[TheOE800]

Greater speed is always better than a lesser speed for reducing time of flight (within reasonable BC's), but there is a speed threshold where a higher BC bullet starting off slower will trump a lower BC bullet starting out with more velocity at distance. This threshold will also change as distance changes.

I believe the current trend is shoot heavier bullets at slower nodes.

 

[secondofangle2]

Taking as an example 162 ELD vs 180 ELD, you need just a 100 fps advantage for the 162, and you have to get to 1500+ yards for the 180 to take over

And the recoil is higher. But the retained energy is significantly better for the heavies much sooner than the drop/wind

 

[Guns&WhiteWater]

Yeah the retained energy is fun when shooting heavier plates, too. Was just shooting some 210 VLDH’s with my 308 and had the IPSC at 365 rocking back and forth. 2740 fps per the Xero. Definitely challenges my recoil management off the tripod though.

 

[secondofangle2]

Whoa! What are you using to launch 210s from a 308 at 2700+

!?!?

 

[Guns&WhiteWater]

Whoa! What are you using to launch 210s from a 308 at 2700+

!?!?

47.7 grains of RL17 at 2.935”, Lapua Brass, GM210M, 26” Bartlein. Only get them to 2450 in my 16”.

 

[Doom]

47.7 grains of RL17 at 2.935”, Lapua Brass, GM210M, 26” Bartlein. Only get them to 2450 in my 16”.

I'll pass on that load. You are pushing the bullet with ~3500 ft-lb of energy and looking at GRT you are somewhere near 70KSI.

 

[Guns&WhiteWater]

I'll pass on that load. You are pushing the bullet with ~3500 ft-lb of energy and looking at GRT you are somewhere near 70KSI.

I know it is a warm load. I set them aside for hunting, figuring the brass would be abused or more likely lost. Just ran a few across the Garmin yesterday to get a more accurate velocity over my old chrony numbers. The primers, bolt lift, and case head expansion are in line with other warm loads I have tested, which is to say I back them down when the pressure signs are there.

 

[CK1.0]

I don't think .308 is the best cartridge to use when discussing this subject. IDK if it's completely irrelevant and I'm not saying .308 is obsolete, but a .308 is already sort of ballistically hobbled compared to some of the other newer options on the scene, and most projectiles one would use in a .308 are already on the heavy side of things.

I tend to see this subject as far more relevant when talking about applying this to a 6mm or 6.5...

For example, with a 6CM, and a faster 105 versus a slower 115, things will look/feel like basically a wash until ~500 yards as far as retained energy, hit or miss, impact/splash. But at 600 and past that... out to 750-1000+ the 115 is going to yield more signature downrange due to more retained energy (and since you can use nearly the same charge for either, there isn't much of any real penalty in so far as having to deal with more recoil using the heavier 115).

6CM, 105 .280BC, 2900fps, 41gn charge:



6CM, 115 .305BC, 2800fps, 41gn charge:

 

[DeathBeforeDismount]

I'm not a huge fan of the 150+ class bullets out of a creed. I used to compete with the 153 berger and it's a very accurate and predictable bullet. When shooting KD with a good solver the bullet elevation drop matters less and even wind to a certain degree.

I like the 130 class bullets specifically the Berger 130 AR/hybrid out of a creed. You have similar BC to a 105 berger hybrid with more energy on target. You can get it fast enough that inside 500 yards it shoots flatter. You can also run them out of an AR unlike the other 140+ class getting into OAL/mag length issues.

You also need to run a 7.5 tw with the heavies or you pay a BC penalty due to marginal stability. You can't get the 150s+ fast enough in a creed without trashing brass/barrel life.

The berger 144 is the option I would run if you want a 140+ class. It's a slick pill.

I think the 150+ class is much better suited to the prc and sherman shorts where you can get them fast enough to take advantage of the increase in BC. The 130s are also cheaper and when you shoot thousands of bullets a year...it does add up.

 

[Guns&WhiteWater]

I have found the 144’s to be optimal in my 6.5x47 as well, but I still like messing around with the 123’s when I’m not shooting past 500 because they’re cheaper and hang pretty well in the wind.

 

[Basic user]

I'm not a huge fan of the 150+ class bullets out of a creed. I used to compete with the 153 berger and it's a very accurate and predictable bullet. When shooting KD with a good solver the bullet elevation drop matters less and even wind to a certain degree.

I like the 130 class bullets specifically the Berger 130 AR/hybrid out of a creed. You have similar BC to a 105 berger hybrid with more energy on target. You can get it fast enough that inside 500 yards it shoots flatter. You can also run them out of an AR unlike the other 140+ class getting into OAL/mag length issues.

You also need to run a 7.5 tw with the heavies or you pay a BC penalty due to marginal stability. You can't get the 150s+ fast enough in a creed without trashing brass/barrel life.

The berger 144 is the option I would run if you want a 140+ class. It's a slick pill.

I think the 150+ class is much better suited to the prc and sherman shorts where you can get them fast enough to take advantage of the increase in BC. The 130s are also cheaper and when you shoot thousands of bullets a year...it does add up.

Are you saying that the 140s may be too heavy out of an ar?

 

[357Max]

Are you saying that the 140s may be too heavy out of an ar?

Depends on barrel length & purpose. Lighter pills such as 130 otm work very well with a slightly faster powder. That is an advantage with shorter barrels & a can.

I’m working with an 18” 6.5 AR & the 130 otms are shooting great with RL 15.5. Complete burn & 2700.
Just shot a ladder of 135 A-tips using RL16 & found a good shooting load at 2650.

Recoil between them is indistinguishable, but 135’s will pay off with ability to spot & better bc beyond 800-900.

 

[Basic user]

I see. I am also building a 6.5cm ar; 20" though. I was wondering about that. Initially this thread was about heavy 6.5 bullets in a full size bolt gun, the help with a shorter barrelled gas gun will help me as well. So since I'm at 20", you think I should shoot the berger 130 ar hybrids as fast as I can?

 

[357Max]

I see. I am also building a 6.5cm ar; 20" though. I was wondering about that. Initially this thread was about heavy 6.5 bullets in a full size bolt gun, the help with a shorter barrelled gas gun will help me as well. So since I'm at 20", you think I should shoot the berger 130 ar hybrids as fast as I can?

For me the 130otm is tue ticket to 1000 & in. Same for bolt gun. My barrel is really happy with the 130’s and that’s a big factor. The only reason I was exploring heavier is that I’m going to shoot the AR in a match that goes to 1500+ on the long end.

I shot this match 2 years ago with a 6.5 bolt gun using 130otm at 2950. Could see trace no problem when weather conditions were favorable. I only had dope to 1000 & still got first round impacts at 1260y. At 1560 not so much.

I got 2600 with 156 eol, but that required RL26, load is hard on brass, and added recoil is noticable on the AR.
Similar story with 147 eldm + RL26 @2680

The 135 A-tip + RL16 worked up to 2685, but shot well at 2650 & brass looks good. I’m rolling with that for tue match.