.308WIN Load development for long range *QUESTION*

Evil_Dark said:
I was told by a experienced shooter on this forum that when the bullet travels inside a barrel, the barrel will mark/scratch the bullets (the riflings, the chamber etc...) an then affect the bullet shape / aerodynamics. Not very much, but enough to make a difference from rifle to rifle. I have a 5R barrel, so it must engrave/mark the bullet differently than a standard one...

I tought that it was a good theory, plausible. And it also explain the little difference I had when I compared my results VS a ballistic program results, I had more drop that what was supposed, knowing all the environment variables, and fired through a chronograph. When I played around (lowering) the BC to fit the ballistic program results, I began to match every time my results with the ballistics program, even with different shooting conditions (different wind, temperature, velocity and angle of fire) now the program results where pretty dead-on. That's why I adopted this theory...

Dark
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Truing the dope on a ballistic program in that order is normal. I do the chrono, actual drops, true the MV vs drops, adjust the BC last if it warrants.(usually it's just a G1,2,3,4,5,6,7 error wrt bullet form.)

No doubt disfiguring a bullet, even slightly would have a degree of affect on bullet drag. I just have no good way to quantify that but I have witnessed twist rates, air density and velocity make observable differences in stability even at short distances.

Plus, I always take bullet OEM data with a grain of salt. especially advertised MVs and BCs.
 
Evil_Dark said:
It's also a question of availability. I've switched to Sierra (with the 168gr BTHP) because large qtys were hard to find with Hornady. I shoot more and more, so box of 100 are quickly spent... And sometimes box of 100 are also out of stock... Upsetting!

Dark
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If you can find the 168 I'm sure the 175 isn't far away either and it doesn't have the same problem. ANY of the other 168 class bullets from ANY other manufacturers work fine. Again if you are stuck on 168s try the Berger hybrid. Best to order a bunch and do it online that way you don't have to piss around being stuck to what the local shop has in stock. Were it means you wanted to stay with a lighter bullet it would either be the 168 hybrid or the new Sierra 175 Tipped matchking.
 
rugbydave said:
Depends what you want it for... The further you're planning on shooting, the more you benefit from a faster (stable) load in that your round will stay supersonic (hence predictable) further. By my understanding, the 168s aren't great past 600m anyways.
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168 grain sucks for 1000 yards or more , you will get lots of keyholing
 
Ruthless said:
I second that and they are very consistent on weight and shape. If you want to save a little go with Amax 155 they are very stable past 1000 as I've shot them to 1km
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Well i don't think the amax will be in the same league as the scenar's they are not as consistent as the scenar's . I will show you the theory behind it , this is by master ballistician bryan litz . Look at the photos below , the spectrum of the G7 form factor will determine the better 1000 yards or more bullets . The best 1000 yards bullets will have a G7 form factor of less then 1.0 , look at the scenar's G7 form factor vs the amax form factor . The scenar is clearly the better out of the two .the scenar's form factor is .988 vs the amax 1.099





 
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Ok so I loaded multiples loads with the 178gr A-Max, then 208gr Hornady ELD's.

Very good results with pretty much all the loads of the 178gr @ 200y, all the groups were tight. Tested the IMR-4895, from 39.9gr to 42gr in 0.3gr increments. Found a large node from 41.1 to 41.7gr, so I will fine tune a load in this area. All bullets fired with 41.1 - 41.4 - 41.7gr was between 2609fps - 2641fps, which is good and will be variation tolerant. Promising to 850 yards, regarding my ballistic calculator. To be tested! :)


The 208gr ELD was'nt that promising...
I've started at 39.5gr of IMR-4895, to 41.6gr in 0.3gr increments. I've got interestings velocities and no overpressure signs at 41.6gr, between 2590 - 2601fps.

BUT all the groups were'nt tight at 200 yards. So i'm suspecting that my barrel's rifling had difficulties to stabilize the bullets. I have a 5R 1:10 twist barrel, but with regular lighter bullets I have to clean it (copper removal) every 350 shots, and i'm at 250 shots from the last cleaning, meaning roughly 2/3 of the way until cleaning. Can it be that heavier bullet requires cleanier barrel to help?

Dark
 
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Experiences with Berger 185 Juggernaught match bullet??

Anyone use these for long range shooting? Would seem to be a good choice in theory.
 
Also big thing to note and I'm speaking from my own experience is that 1/4 MOA at 200-300 yards can be horrible at anything higher than 600. And some that were 1/2 MOA at that distance 200-300 were 1/3 or better at longer range

I think Jerry Mystic can chip in on this further
 
Evil_Dark said:
Ok so I loaded multiples loads with the 178gr A-Max, then 208gr Hornady ELD's.

Very good results with pretty much all the loads of the 178gr @ 200y, all the groups were tight. Tested the IMR-4895, from 39.9gr to 42gr in 0.3gr increments. Found a large node from 41.1 to 41.7gr, so I will fine tune a load in this area. All bullets fired with 41.1 - 41.4 - 41.7gr was between 2609fps - 2641fps, which is good and will be variation tolerant. Promising to 850 yards, regarding my ballistic calculator. To be tested! :)


The 208gr ELD was'nt that promising...
I've started at 39.5gr of IMR-4895, to 41.6gr in 0.3gr increments. I've got interestings velocities and no overpressure signs at 41.6gr, between 2590 - 2601fps.

BUT all the groups were'nt tight at 200 yards. So i'm suspecting that my barrel's rifling had difficulties to stabilize the bullets. I have a 5R 1:10 twist barrel, but with regular lighter bullets I have to clean it (copper removal) every 350 shots, and i'm at 250 shots from the last cleaning, meaning roughly 2/3 of the way until cleaning. Can it be that heavier bullet requires cleanier barrel to help?

Dark
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Your 1-10 twist is plenty to stabilize the 208. It likely just needs more tuning.

Try shooting the 208's further out and see what results you get.
 
Just fine tuned more the 178 A-MAX, nice results! Just not good enough to be comfortable and over the sound barrier at 1000Y, despite that some had good experience with it over 1000's.

IMR-4895 41.6gr, COAL of 2.825", neck turned Lapua Brass, Win. Primer. 3/4 MOA at 200Y, avg of 2665 fps and SD of 10, spread 26. So it looks promising! Still have to work on the ELD 208gr.

Dark
 
My "go to" mid range (300-800y) is a 168 SMK. I push them slow, with 40.5gr of H4895. I don't seem to have any problem hitting @800 with that load. 850.... no dice!

I also use the 168 A-max. It's a really good performer out to 1050. At 250fps faster than the SMK, it's not a mystery why I can reach out further!

It doesn't seem to matter what load or projectile I have tried in the 308. I have never made a hit past 1100.....

I have since moved to 6mm 105's at 3100, and the next will likely be a 6.5...

My $.02
Cheers!
 
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