Help me with my velocities [Archive]

ubet

11-04-21, 11:32

So I went and ran two different loads through a carbine this morning. 14.5” barrel, 16.1” including muzzle break. The 77gr smk load when I did load development was 3/4 moa at 700 in a ladder/ocw test, the loads were 23.9, 24.1, 24.3 I settled on the 24.1. The other load is a 62gr hpbt Hornady at 23.9. I know the sd and es is high, I loaded these on a 650. My question I guess is, are these fast enough? I was fairly happy with the 62s but the 77s seemed slow. They were 10 shot tests https://uploads.tapatalk-cdn.com/20211104/d2c81f2c6f15147d4b80a0c1962e62e4.jpg
https://uploads.tapatalk-cdn.com/20211104/e3cc3982434d04864f6aba28cf517037.jpg

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mRad

11-04-21, 12:24

If you’re shooting 3/4 MOA at 700 yards with a 14.5”, you don’t need to worry about it.

My 14.5” gets 2550 with my 77 gr load, my 16 gets 2750with it.

ES and SD would indicate out of tune load and it’s time to adjust there; usually it’s seating depth…but I had a hard time believing it’s worth chasing if you’re 3/4 MOA at 700.

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JimmyB62

11-04-21, 16:36

If you were able to shoot 3/4 moa at 700 yards then there is likely something wrong with your chrono. A 122 es would mean about an 18” vertical spread at 700 yards which is well outside of 3/4 moa. Can you borrow another chronograph and confirm results? Maybe I’m just not understanding which isn’t uncommon for me these days.

ubet

11-04-21, 19:44

I’m not getting it either. My chrono is a fairly new magnetospeed v3. For my bolt gun I show this screenshot. I haven’t taken this ar out too 700 since I built the load. But might have the target somewhere. https://uploads.tapatalk-cdn.com/20211105/c246246aa166c538fce6e8a0c6e828bc.jpg

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mRad

11-04-21, 22:28

ubet

11-05-21, 18:36

If you haven’t taken it to 700 yet, why did you say it was shooting 3/4 at 700?

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Since I built the load. I shot it at 700 when I built it.

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mRad

11-05-21, 18:37

Since I built the load. I shot it at 700 when I built it.

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And what’s wrong with the load you were using then? That’s great accuracy for an AR at 700.

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ubet

11-07-21, 11:03

And what’s wrong with the load you were using then? That’s great accuracy for an AR at 700.

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The 77s are the same load. I don’t know why my velocity is so wanky I guess. What’s a normal es and sd for an ar with 77s? I just loaded those I didn’t weigh every load. Dumped the cases out of a jug, the 1000 top brass jug and went to loading.

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mRad

11-07-21, 11:11

ES and SD can be a result of poor processes, inconsistencies in components, being on the edge of a node, or even chronograph equipment failure.

Believe it or not, even a weakening hammer spring can cause inconsistent velocity.

With 100 FPS ES, it would be really hard to attain 3/4 MOA vertical at 700 yards.

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ubet

11-08-21, 01:52

It’s all cci 41, cfe223 powder, crimped, seated just below mag length with a Redding comp seating die. The cases for the 77s were lc brass from top brass.

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Bimmer

11-09-21, 10:46

The 77gr smk load when I did load development was 3/4 moa at 700 in a ladder/ocw test, the loads were 23.9, 24.1, 24.3 I settled on the 24.1.

If you haven’t taken it to 700 yet, why did you say it was shooting 3/4 at 700?

Since I built the load. I shot it at 700 when I built it.

We're trying to help you, but you're not making sense...

If this load shoots 3/4moa @ 700yds, then don't change a damned thing.

If that's not the case, then you're right that your velocities are all over the place...

It’s all cci 41, cfe223 powder, crimped, seated just below mag length with a Redding comp seating die. The cases for the 77s were lc brass from top brass.

Any number of factors could give you inconsistent velocities...

How sure are you about your powder charges?

Did you trim the cases? (Don't trust that they came trimmed to a consistent length.)

Why are you crimping?

ubet

11-09-21, 17:19

We're trying to help you, but you're not making sense...

If this load shoots 3/4moa @ 700yds, then don't change a damned thing.

If that's not the case, then you're right that your velocities are all over the place...

Any number of factors could give you inconsistent velocities...

How sure are you about your powder charges?

Did you trim the cases? (Don't trust that they came trimmed to a consistent length.)

Why are you crimping?

I’m confused as well, trust me.
No, I didn’t trim. That in there is probably the culprit too.
I’ll measure some tonight and see what the lengths are.
I crimped because in my original load development, the crimped shot more accurate than non crimped.

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Bimmer

11-09-21, 17:24

No, I didn’t trim. That in there is probably the culprit too.
I’ll measure some tonight and see what the lengths are.

I crimped because in my original load development, the crimped shot more accurate than non crimped.

Assuming that wherever you bought your brass didn't trim it, then it needs trimming, especially if you're hoping for something consistent and accurate.

Hopefully somebody smarter than me will chime in to confirm or correct me, but if you're not trimming your brass, and they're all different lengths (even slightly), and then you crimp the case necks, then the different length case necks will be crimped more/less based on how long they are, which will give you wildly varying neck tension, which will give you wildly varying velocities (like you're seeing).

mRad

11-09-21, 17:43

Depends on the type of crimp. Roll crimp must be exactly the same length.

Taper crimp it’s better if it is all the same but it doesn’t have to be exact.

If it’s “factory crimp” a little variance doesn’t seem to make much difference.

Anything I’m shooting for precision, I’m trimming every firing regardless.

I’ve found crimping does make better ammo for an AR. I’ve more than once had erratic fliers. I figure out it was from rounds sometimes growing as they were slammed into the chamber. Crimping solved fliers.

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ubet

11-09-21, 17:57

It’s all top brass. I’ll measure and report back, I have a few hundred empty cases still. Thanks for the help. I didn’t even think of the trimming being an issue.

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ubet

11-10-21, 23:12

So I measured case lengths, the 12 I measured varied +/- 12 thousandths

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Bullz

12-02-21, 10:08

I'd like to help you out, but I'm a bit confused by what I'm reading here. For long range precision and accuracy, you need to be concerned with consistency from round to round. It doesn't matter what your muzzle velocity is as much as whether it's the same velocity from shot to shot. Check this blog and it will help tremendously:

https://precisionrifleblog.com/2020/12/05/muzzle-velocity-statistics-for-shooters/

HKGuns

12-02-21, 10:56

Based on the numbers you provided, you're asking the wrong question. The question is why is your ES >100 and the answer is inconsistencies in your loading process. Get your ES below 10 then start looking at velocities. This assumes your magneto-speed is producing reliable results, a sanity check of that is probably warranted.

Bullz

12-02-21, 12:36

Get your ES below 10 then start looking at velocities

I'm assuming he meant below 100 - I'm not trying to contentious here... but an ES below 10fps is really low. like REALLY LOW and really hard to achieve on a progressive press in my experience. An SD of around 10fps will probably give you about 1 moa of vertical stringing/dispersion at 700 yards. You should be able to get an SD of around 15fps without getting too fancy with handloading. I just wanted to throw that out there if you're going to set goals for yourself.

Also, if you shoot at various ranges, you can calculate your MV to corroborate your chronograph. If you're consistently getting 1 moa at 700 yards, you know your approximate SD. Then if you observe your drop at 200, 300, 600, 700, you should be able to calculate a fairly accurate MV.

HKGuns

12-02-21, 13:30

I'm assuming he meant below 100 - I'm not trying to contentious here... but an ES below 10fps is really low. like REALLY LOW and really hard to achieve on a progressive press in my experience. An SD of around 10fps will probably give you about 1 moa of vertical stringing/dispersion at 700 yards. You should be able to get an SD of around 15fps without getting too fancy with handloading. I just wanted to throw that out there if you're going to set goals for yourself.

Also, if you shoot at various ranges, you can calculate your MV to corroborate your chronograph. If you're consistently getting 1 moa at 700 yards, you know your approximate SD. Then if you observe your drop at 200, 300, 600, 700, you should be able to calculate a fairly accurate MV.

I didn't see he was using a progressive press. I only load rifle rounds on a SS press as there is just too much variability when using a progressive to load accurate rifle rounds. My progressive is strictly for pistol cartridges.

But that too is a place to start at refining his process.

mRad

12-02-21, 14:48

Bullshit on not getting low ES on a progressive. You first have to have an in-tune load. Then you have to have your process down. You can just read instruction on the dies, rather learn to set them appropriately, learning tweaks, etc.

Believe it or not, many top F-Class competitions use a Dillon 750.

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1168

12-02-21, 17:11

I get around 14-15 sd on a Dillon 750 using 62s and an unsuitable surplus powder, taking turns pulling the handle as fast as we can with no consideration whatsoever for precision. Its a 0-300 blasting load.