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  #21  
Old 03-03-2021, 02:40 PM
smoothy8500 smoothy8500 is offline
 
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Quote:
Originally Posted by Jpolham1 View Post
If I can hold my ES around 30 like my 49.5Gr load above but with more groups I will call it good and be happy.
The ES 30fps will only affect (enlarge) the group vertical dispersion by 1.5" (1/4 MOA) at 600yds and is basically nil at 300. You're good to go.

Since AA2520 meters quite consistently, you should be able to efficiently bulk load accurate ammo with this.

My goal, ES of low to mid 30's with a high BC projectile (such as your 155's) in bulk loading, is fairly forgiving as to vertical dispersion for NRA Highpower. F-class with the 1/2MOA rings is not as forgiving.
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  #22  
Old 10-16-2021, 06:22 PM
Exiledviking Exiledviking is offline
 
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Loaded up some 150 gr SST with AA2520 in PMC once-fired brass. Started at 45 gr and worked up to 47.5 in 0.5 increments.

I need some advice as I appear to be chasing my tail. When we chrono'd the first batch of loads, the 46.0 gr load of AA2520 was the standout at 2664 fps and a SD of 22 and an ES of 77. The next best was 47.0 at 2757 with a SD of 43 and an ES of 131.

I put together another batch to verify what we'd seen with the 46.0 load and added a 46.2 load for comparison.
Shot those yesterday and the temperature was a good 15 degrees warmer than last time. The 46.0 load opened up to a SD of 52 and an ES of 153 and the average velocity was down a little at 2628.
The 46.2 load ran at 2669 with a SD of 44 and an ES 139.

So, being new to this; I should be looking for accuracy first, right? Then followed by ES and then last SD?

Is the velocity about right at 2669 fps for non-match use and reliability? Or do I need to move closer to the 2740 fps Federal American Eagle runs with a 150 gr bullet?

I'm limited to a 100 yard range and with my eyes I'm good for a sub 8 inch group at 100 on a good day.

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  #23  
Old 10-16-2021, 06:53 PM
Jpolham1 Jpolham1 is online now
 
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With only 100 yards, ES/SD doesn’t matter. It starts to matter to help “predict” a good load at longer range. Find a good accurate load at 100, ES/SD will be what they be and you won’t tell a difference.
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  #24  
Old 10-17-2021, 08:36 AM
JimF JimF is offline
 
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Originally Posted by Exiledviking View Post
. . . . . .I need some advice as I appear to be chasing my tail. . . . . .
Most of us here . . . .if we care to admit it . . . .have been where you are now.

“Chasing my tail” in putting too much emphasis on the “numbers” was proving too expensive . . . .given the cost of components . . . so I opted to focus on “accuracy” in 10-shot group size.

Running my loads through a chrono was interesting, but in the long run, “accuracy” triumphed over the “numbers.”
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  #25  
Old 10-22-2021, 02:20 AM
Exiledviking Exiledviking is offline
 
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Thank you for helping me figure where to go from here. I'll be looking for the loads that group the best.

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  #26  
Old 10-22-2021, 07:02 AM
rcolarco rcolarco is offline
 
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Quote:
Originally Posted by Exiledviking View Post
So, being new to this; I should be looking for accuracy first, right? Then followed by ES and then last SD?

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If you have accuracy, who cares about ES and SD? These statistics for small batches are meaningless anyway. It's too bad chronos display them, they are just confusing.

As you have discovered, temperature changes wreak havoc on your statistics.

I teach statistics for a living. I do not own a chrono. All I care about is group size.

I went to the range yesterday. Fellow had one of those slick chronos that looks like a bayonet. He was fretting about his numbers. I trained my scope on his target. 6" groups at 100. He has better things to worry about.
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Last edited by rcolarco; 10-22-2021 at 07:05 AM.
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  #27  
Old 10-30-2021, 08:42 AM
britrifles britrifles is offline
 
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I fell into the chrono data trap some years ago. All it did was consume reloading components and powder, and burn up barrel life. I also spent way too much time shooting off the bench.

If you are loading for the M1, it will shoot just fine with a broad range of powders and charge weights. I’ve been shooting the 125 TNTs for a number of years now and the amount of powder has little effect on accuracy. Shooting skill has a very large effect on accuracy.
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  #28  
Old 11-06-2021, 08:32 AM
Unclenick Unclenick is offline
 
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Chronos have their valid uses, but a lot of people expect them to tell something they don't. The group-size difference velocity consistency makes to POI at 100 yards, is something most people just can't discern. Long-range is different but isn't always affected the way you expect. SD tells you something about how consistent your powder ignition is and shrinking it generally means improved ignition consistency which can shrink groups for non-trajectory-related mechanical reasons (closer to duplicating the same barrel time, hitting the same phase of muzzle vibration, or some other disturbance). But how much difference turns out to depend on the gun, and can be anything from zero to significant.

Velocity consistency can't directly predict actual target POI's just as the exterior ballistics tables don't give you exact POI differences with velocity. This is because they assume a perfectly rigid gun and don't allow for the fact that when a bullet takes longer to get down a barrel, there is more time for barrel vibration to shift the phase of muzzle rise and other motions that cause the exact angle and direction of departure to change. The bottom line is you always have to test for actual effects with your gun, and whether a chronograph will save you any time with that or not also depends on the gun and your load workup method. From this standpoint, I would suggest priority goes to finding a load that groups well, but if you have a chronograph anyway, leave it running to see if you can spot a pattern of velocities that corresponds to your good groups as that might give you a shortcut in future load development for that gun. The exception here would be the bayonet type Magnetospeed chronographs, as those affect barrel movement just as stock contact can, so I wouldn't trust a group optimized with one on the gun to be the same with it off.

What I have used a chronograph for is matching the performance of a new lot of powder to an old one by keeping just enough of the old lot back so I can compare the velocity of loads of the old and new on the same day, under the same conditions.

In that same vein, you can compare SDs to see how consistent your ignition is with a different primer or to see the effect of using mixed brass or from making a change in how far you size your necks down or from using a crimp, or deburring flash holes, etc. How much of this stuff you want to do depends on how precisely you can shoot with your gun in the first place. If the answer is 2 moa, you are probably wasting time and money doing much of this. But if you are shooting sub-moa, you may be able to make an improvement. Also, if you are just curious it may be worth it to you. It is a hobby, after all.

Another chronograph use is determining ballistic coefficients for bullets lacking published BCs.

Another use is getting muzzle velocity for a ballistics program so you can double-check that your hunting bullet's impact velocity will be as close to the middle of the manufacturer's recommended range as you can manage.

A common handloader's use for the chronograph is to run a small sample (10) just to check that velocity is not substantially exceeding what a load manual says it should be for your bullet weight and barrel length, as that means you have higher pressure with your components. This is especially useful when you aren't using the exact same bullet, brass, or primer the data was developed with. Knowing in which direction your pressure differs from the published data in conjunction with an interior ballistics program can inform how far you want to try to take charge weight increments.
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  #29  
Old 11-06-2021, 04:56 PM
britrifles britrifles is offline
 
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Having a chrono has been beneficial in some comparisons I made between service ammunition and my handloads. In this case, I wanted to compare .303 Mk 7z ball ammo to my 174 gr SMK match loads. Bullets are the same weight, but the Mk 7 bullet is a flat base. I found that subbing the SMK for the service bullet (I pulled the bullets from Mk 7 ball ammo, resized the neck, and seated a SMK) gave about a 50 fps velocity increase, presumably because of the lower bearing surface area of the boattail bullet.
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  #30  
Old 11-08-2021, 03:33 PM
Unclenick Unclenick is offline
 
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It's mostly just the boattail taking up extra powder space and the difference in ogive radius changing how much gas bypass occurs before the bullet gets to the lands. Higher bore friction, counterintuitively, often leads to higher velocity by giving the powder more resistance to build pressure against. This is why, when moly-coating bullets was a craze, people would often report losing 20 to 50 fps off their favorite load and having to up the charge to get it back. If the bullet has too little friction, it gets out ahead of the powder's gas generating rate, causing faster expansion of the powder space earlier in its travel.
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