Finally got my hands on a chrono... .308 load continued...

[kis2]

so a gracious THR member let me borrow his chrono, and today I got out and put my loads to the test. here are the details:

168gr AMAX
41.7gr of varget
Wolf primers

After ten shots, throwing out the two extremes, my mean velocity was 2528fps.

After 17 rounds with a fairly hot barrel on my stock 700p, I shot the below group with a bipod as front rest, my hand as rear, in prone and it's a good example of the average. running those numbers through hornadys ballistic calculator, I should be supersonic out to 1k yards (my ultimate shooting goal), but only by about 25-50fps.

good enough? good enough for 8-900 yds if not 1k? sorry to keep on about this, but I want to learn from you experienced folks.

 

[USSR]

good enough? good enough for 8-900 yds if not 1k? sorry to keep on about this, but I want to learn from you experienced folks.

Good enough for short range shooting, but definately about 200fps shy of a LR load.

Don

 

[kis2]

I believe you because of your experience obviously, but could you please explain why? I mean is there more to consider than the transonic process?

also, the first two shots over the chrono measured at 2650ish, with the followers being the above mv. whats up with that? chrono anomaly? no way I was that far off on my powder.

 

[gun guy]

Velocity changes are called standard deviation, with handguns 100 fps isn't too bad. with rifles, +- 300fps isnt too much unless you are serious about match grade performance. There are alot of minute physics involved in weapons. Every bullet has a tolerance, they are not all exact. Most powder scales only measure to the tenth, that leaves .00-.09 varience even if you measure each charge. Commercial charges are thrown, often handloads are too, more error. Barrel changes with each round as heat increases. Bullets actually speed up after leaving the barrel due to slipstreaming the gas charge, mild winds break that up. Once you start to chrono loads you see that advertised fps are only an aproximation, not the last word. It's just the way it is.

 

[MCMXI]

After ten shots, throwing out the two extremes, my mean velocity was 2528fps.

also, the first two shots over the chrono measured at 2650ish, with the followers being the above mv. whats up with that? chrono anomaly? no way I was that far off on my powder.

Velocity is your friend when shooting over long distances. The faster your bullet gets to the target, the less your bullet is affected by all the bad stuff. I mean no disrespect but it takes a lot of work to find a good load, so once you have one, you may not have the motivation to find another. I've been through this before too. However, if you stay with this load and don't try to find an accurate load with at least 100 fps more velocity, and ideally more, I think you'll regret it.

As for your velocity data, I typically find that my first shot out of a clean barrel is the slowest of the day (see below). I put it down to trace oil in the barrel which may reduce friction thereby lowering the pressure (just a theory). I shoot 178gr A-MAX bullets at around 2,650 fps without any pressure issues so you're definitley on the low end of the velocity scale and that's with a lighter bullet. Here's some velocity data comparing my reloads to FGMM and AE ammunition. I use a CED M2 chronograph. The Shooting Chrony Beta Master that I was using last year reported the velocities quite a bit higher. I trust the CED M2 more than the SC.

 

[MCMXI]

with rifles, +- 300fps isnt too much unless you are serious about match grade performance.

An extreme spread of 600 fps ... that's HUGE!! That crappy AE ammunition above only had an ES of 30 fps. I expect SD numbers in the single digits for ALL rifle ammunition that I load. For match rifles, I'd like to be as low as humanly possible.

 

[kis2]

hhmmmm, ok, well maybe what I'll do is work up six rounds of a few different increases in powder, group them in 3's, and the ones that group well get clocked in 3's for an average.

so velocity is a friend, but group size is too. where do you guys call the compromise? fast as you can go and be submoa at 100yds? hopefully I can find a faster round that'll keep this group. I don't want to see that single hole go away

thanks all

 

[MCMXI]

so velocity is a friend, but group size is too. where do you guys call the compromise? fast as you can go and be submoa at 100yds? hopefully I can find a faster round that'll keep this group. I don't want to see that single hole go away

I don't believe that velocity, accuracy and precision are mutually exclusive. You can have all three. As for compromising, it all depends on what your objectives are. Your objective is 1000 yards and I very much doubt you'll be happy with that load. To be honest, I wouldn't recommend that bullet either for long range. Better choices would be the 155gr Lapua Scenar, 175gr SMK or 178gr A-MAX. Compare your current load to what I'm shooting at 1000 yards with a 10 mph full value wind, 200 yard zero and a DA of 1,800 feet. If you can bump up the velocity it'll be a whole lot better.

168gr A-MAX at 2,528 fps
Drop > 39.00 MOA
Wind drift > 9.75 MOA
Velocity > 1,183 fps

178gr A-MAX at 2,650 fps
Drop > 32.50 MOA
Wind drift > 8.00 MOA
Velocity > 1,341 fps

Another thing to think about is that it's errors in wind drift that are the problem, not wind drift itself. What I mean is, if the wind is blowing 10 mph and you know it's blowing 10 mph, you can correct for it. However, what if it's blowing 8 mph but you call it at 10 mph, or the wind suddenly drops or picks up by 4 mph? Look at the difference at each wind value to see how this will affect your hits on target. I hope that makes sense.

 

[ArchAngelCD]

168gr AMAX
41.7gr of varget
Wolf primers

I don't know how much a difference between the Sierra 168gr bullet and the 168gr A-MAX bullet has but according to Hodgdon your charge weight is below the minimum. Using Varget they list a starting charge of 42.0gr and a Max charge of 46.0gr with a 168gr SIE HPBT bullet. You have a lot of room to increase the charge and velocity and still be well within the pressure limits.

I looked it up and both bullets have a Sectional Density 0.253 and the Sierra bullet has a BC of .462 while the Hornady bullet has a BC of .475. According to those numbers the charge data should be correct for the A-MAX bullet as well as the listed Sierra bullet. Your charge is too light and below Hodgdon's recommended minimum...

 

[Walkalong]

Since you are below minimum, you can continue to work up your load using more powder. You will hit another "sweet spot" at a higher velocity along the way.

so once you have one, you may not have the motivation to find another.

Yea, ya hate to leave a spot that works, but for his purpose, long distance, he needs to find a good load at a higher velocity.

 

[kis2]

thanks guys, I'll give it all a try.

as far as the load being below mins, in the hornady book this is actually their last increment before a max of 44 grains. don't know where the discrepancy is, but I've gone up to 43.x and haven't seen any signs of stress, so maybe my book is full of it. I'll still work up with caution. so somewhere closer to 2700 then.

thanks again

 

[USSR]

kis2,

Your situation (finding an accurate but slow load), is exactly why the first thing I do with load development is work my way up to a full power load over my chronograph, and not even concern myself with the accuracy, only the amount of powder that gets me up to where I feel it should be while looking for pressure signs. Once I find out how much powder it takes to reach my reasonable velocity level, I start playing around with charge weights at that level and slightly below and am now looking for that full power sweet spot in regards to accuracy. Finding an accurate but slow load does not interest me, unless I am looking for a mid-range load.

Don

 

[kis2]

I think that is definately the way I'll go about it next time USSR. make sure your safe up to a maxish load, and then tune the accuracy from there. sounds right to me. I did take out some 43.2gr today and it got a .4moa (see pic), so based off some good advice I'm going to develop around there. that should put me between 26-2700.

in other news, the 41.7 grain made 2 out of 3 hits on a torso sized target today at 900yds. I was thrilled having not shot past 300 before! gives me high hopes for the hotter loads.

Thanks again all