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Old September 13, 2019, 07:56 AM   #1
SKULLANDCROSSBONES65
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What variation in velocities do you get on your hand loads?

G'day
What is your standard deviation on your hand loads?
I chronographed some .223 loads yesterday and had +- 30 f/s.
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Old September 13, 2019, 09:09 AM   #2
hounddawg
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the smaller the case volume the harder it is to get low SD's in my experience. Unless you want to do long range I would not sweat the SD's with that .223 as long as your groups are satisfactory to you. I had one load for .223 that would give 20 shot groups of a MOA or less at 300 that had triple digit SD's. If it works for you then just shoot it
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Old September 13, 2019, 09:36 AM   #3
Unclenick
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SKULLANDCROSSBONES65,

I don't know what number of rounds you put through the chronograph to get that number. If it was 10, then your standard deviation will be about 1/3 the extreme spread of 60 fps, or about 20 fps. That's neither remarkable nor terrible.

The first trick for consistent velocity is to always have the powder in the same position in the case at firing. If the load is compressed, it will stay put, but if it isn't, always handle the gun and cartridge to place the powder over the flash hole. That will provide maximum pressure and the most consistent ignition. If your range's rules allow it, chamber the round, tip the muzzle up and tap the butt of the stock to set the powder back and then lower the gun slowly to level to shoot.

If you want to do better than that gets you, pay extra attention to ignition. Debur the flash holes and prime carefully to compress the primer between 0.002-0.004 inches (.05-0.10 mm) beyond the point where you just feel the primer's anvil making contact with the bottom of the primer pocket. This is called Setting The Bridge (of priming mix between the nose of the anvil and the bottom of the primer cup) or Reconsolidation of the primer. It is seating them pretty hard, but that specific range was found best for ignition reliability and consistency by U.S. Naval Ordnance at Indian Head back around 1980, and it still seems to be best today.

You can also do this by the brute force feel with some success:
"There is some debate about how deeply primers should be seated. I don’t pretend to have all the answers about this, but I have experimented with seating primers to different depths and seeing what happens on the chronograph and target paper, and so far I’ve obtained my best results seating them hard, pushing them in past the point where the anvil can be felt hitting the bottom of the pocket. Doing this, I can almost always get velocity standard deviations of less than 10 feet per second, even with magnum cartridges and long-bodied standards on the ’06 case, and I haven’t been able to accomplish that seating primers to lesser depths."

Dan Hackett
Precision Shooting Reloading Guide, Precision Shooting Inc., Pub. (R.I.P.), Manchester, CT, 1995, p. 271.
Figure you are going for a percentage of Muzzle Velocity (MV). Hackett's '06 10 fps SD is just over 0.36% of MV at 2750 fps, a typical velocity for that gun. If your 223 Rems have an MV of 3200 fps, then an SD of 11.6 fps is equivalent and you are looking for an extreme spread of about 35 fps.
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Old September 13, 2019, 10:25 AM   #4
hounddawg
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Here at USAMU, we ensure our rifle primers generally run -0.003” to -0.005” below the case head. Maximum primer seating depth is -0.006”, and minimum is -0.002”. Upon inspection, any cases with excessively high primers will be corrected before loading. (Quick & inexpensive ways to checking primer seating depth will be covered below.)
https://www.facebook.com/USAMU1956/p...54324527184734

I have found my primer choice will affect SD's more than the seating depth. Some powders like CCI, some Federal etc. But then it seems there are about a million factors, or at least a couple of dozen, that affect velocity consistency including recoil management, powder choice, case fill etc
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Old September 13, 2019, 10:45 AM   #5
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I find that consistency in reloading technique has the biggest effect after I have found a recipe that works. Changing primers, powders, bullets, and brass can all change results until you get the new combination stabilized and stick with the components until you get them right.

When I have a good shooting load and have taken the time with case preparation and have measured powder, seating depth and cartridge base to ogive for every round so I have gotten each of the rounds close to identical, I find that my SD generally is below 10 fps - my best SD results are 3 to 5 fps. That happens occasionally especially but that is for about 25 to 25 rounds. Factory match round SD results run about 15-17 fps with my Oehler 35P so I expect my hand loads should do better than factory and they do, unless something has gone amok.
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Old September 13, 2019, 04:02 PM   #6
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I agree 100% percent Rimfire. My reloading technique is simple but every round is identical to the last one right down to case length and primer depth and the velocities are always consistent when I settle on a load. Building ammo is the easiest part of the precision rifle hobby in my opinion. It's that nasty wind and mirage that makes me cry myself to sleep
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Old September 13, 2019, 04:02 PM   #7
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Quote:
Here at USAMU, we ensure our rifle primers generally run -0.003” to -0.005” below the case head.
That's about right on average for primer pockets that have not been uniformed for depth. It's what the Forster Co-ax press's seating ram is designed to produce. Most primer pockets as-produced are deep enough to put the primer below flush with the head even when the anvil feet are just kissing the floor of the pocket, and that's before NIOH's recommended reconsolidating is done.

There are a couple of ways you can measure exact reconsolidation. One is to use this tool.
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Old September 13, 2019, 04:18 PM   #8
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I use a ancient Starrett dial indicator model 25-141 and the spindle is about .015 smaller than a small primer pocket. I zero the indicator when the spindle is flush with the bottom of the stem. Great for checking primer pocket depth using a slightly different technique or checking primer seating depth. I can check 50 cases for primer seating depth in less than 5 minutes with practice

If you don't have a dial indicator on the shelf that works you can find that Starrett on Ebay for 75 new or and sometimes less than half that used. Mine is old the dial is yellow but it still works great
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Old September 16, 2019, 09:16 AM   #9
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If I'm getting an extreme spread of 20fps or less, accuracy is excellent.
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Old September 16, 2019, 01:43 PM   #10
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Impressive in 10-shot strings; 20 fps ES will result from about 7 fps SD. For 3-shot strings, 20 fps ES indicates more like 12 fps SD, so, good but not extraordinary. For 5-shot strings, it indicates about 9 fps SD, so back toward impressive.
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Old September 16, 2019, 04:45 PM   #11
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If the objective is only the ammo's velocity numbers, don't bag or shoulder the rifle.

Instead, bolt the barreled action to a board clamped to a bench top so it doesn't recoil.

Yes, boresight it to chronograph sensors center. Then do the SAAMI twist with each round chambering it.

SAAMI Twist

A. Cartridges to be tested should be placed in a vertical position with primer-end down in a recessed holding block.

B. When the appropriate test barrel has been properly serviced and the chronograph reset, a cartridge should be lifted vertically from the block. It should be rotated slowly, end over end, in a vertical plane through 360° pausing momentarily when the powder is at the bullet end and again when the powder is at the primer end.

C. The cartridge is then rotated slowly, a minimum amount to enter the chamber, keeping the primer end in the lowest possible position until inserted gently and carefully into the chamber.

D. The cartridge should be seated in the chamber as far as practicable with the fingers. The bolt or breech mechanism should be closed gently in order not to disturb the position of the powder in the cartridge case. The object of this method of handling cartridges is to position the propellant powder at the primer end of the cartridge case by permitting it to fall gently against the primer while rotating the case.

E. The rate of fire should not be rapid enough to cause excessive heating of the barrel. The time between rounds depends on the equipment, as the barrel may be cooled by a constant stream of air on the outside or by directing air through the bore after each ten rounds.

F. Ammunition conditioning should be between 60° - 80°F (15.6° - 26.7°C).

G. A minimum of one and up to three warming shots should be fired before firing each series for record. The velocity and/or pressure of these shots may be recorded, but should not be included in the record of the sample.

Last edited by Bart B.; September 16, 2019 at 05:18 PM.
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Old September 16, 2019, 07:44 PM   #12
hounddawg
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was thinking on this earlier and remember a pair of .260 barrels made by the same barrel maker and both were the same length same twist. One would not shoot any combination except 140 gn bullets with H4350 and Federal primers. The other would shoot anything from 120 - 140 gn bullets and was not powder picky. Put Varget, H4350. IMR 4350 whatever with CCI or Federals and it would shoot .5 MOA groups all day long

Anyway I forgot to answer the question but on 5 shot groups for long range I expect single digits for a 5 shot group. Not to say a low SD equals a good grouping load but I have never seen a distance load with a bad high SD. The best grouping always has a low SD, maybe not the lowest of the test but nothing above ten

Part of your SD is your hold also. A inconsistent shoulder pressure will affect your velocity. So will shifts in your posture
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Old Yesterday, 04:33 PM   #13
GeauxTide
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Quote:
Impressive in 10-shot strings; 20 fps ES will result from about 7 fps SD.
Correct, Unclenick. It was a 10 shot string and the SD was 7 from a 308 load of 42.0 H-4895, Remington Brass, Rem Primer, Rem 150 Corelokt.
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Old Yesterday, 08:39 PM   #14
pete2
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I've never chrono'd a rifle. I just shot for accuracy with the rifle. I have done handguns, .38, 9 and 45. Lowest extreme spread was using brass with the same head stamp. In 45 there is a major difference in .45
acp if mixed brass is used. It really surprised me.
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