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Old January 15, 2013, 08:25 AM   #1
318
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"Close enough for range ammo".....?

Ive been watching a lot of videos on youtube. (Not for loading data, just curious how some different equipment works). I see guys weighing out charges and saying, "its close enough for range ammo", or "thats close enough". Im bipolar and have OCD, so this wont come into play for me. . What do these guys mean by that? How close is close enough? Im sure they arent over the max, i just cant understand what close enough is when relating to gun powder. i cant see being that nonchalant about something that can blow up in your face. Ive thrown my share of hand grenades, and ive never uttered the famous cliche. Help me understand obe one.
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Old January 15, 2013, 09:26 AM   #2
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It all depends on the average value.

My experience pulling commercial and military loads is that you find some fairly wide charge weight variation. Larger than home loading equipment would make. The .30-06 M2 ball lot I pulled down 20 rounds of was loaded with WC852 and had a span of 0.8 grains. This is remarkable because I don't own even a cheap powder measure or hand scoops that can throw a spherical powder that inconsistently, but Lake City's high speed loading equipment managed to do it. The Federal Gold Medal Match .308 Winchester with 168 grain SMK I've pulled had a 0.4 grain span of IMR4064. I had one lots of foreign-made 7.62 NATO ammunition about twenty years ago (Portuguese, maybe; I don't recall clearly) years ago that had a charge weight span of 2.0 grains over 20 pulled rounds.

But here's the thing. If you have a load that is a sloppy ±1.0 grain precision, but your average load is at least 1.0 grain below maximum, that's not unsafe in any way. And sometimes it can still be pretty accurate. Hatcher Notebook includes his mention of having one year loaded National Match ammunition with a coarse grain powder that the arsenal's loading equipment could only dispense to a span precision of 1.7 grains. He'd compared it to a shorter grain candidate that the arsenal equipment could dispense with a span precision of 0.6 grains, but the wider span powder's loads were consistently more accurate in their testing. So that powder wound up loaded in that year's National Match ammunition and several records were set with it.

Hatcher attributed this performance to the coarse powder's ignition characteristics. Packed more tightly and with the grains closer together it lit up more slowly and acted like a slower burning powder, thus compensating for the greater weight of the charge. The result was apparently a sort of self-regulation of performance over the load range they were in.

You will see the above phenomena mentioned from time to time. It's usually in the form of an argument that it's better to dispense powder by volume, despite having to tolerate some weight variation, than to dispense by weight. This is precisely because only volume dispensing takes round-to-round differences in charge packing density into account.

In practice, though, most powders work pretty well when dispensed either way. What you want to do with accuracy loads is find one that's relatively insensitive to exact charge. That is, one that you can intentionally vary ± a third of a grain or more and not have the point of impact on the target change significantly. Then you can adjust your powder dispensing gear to average at the center of that range, and figure both weight and charge density can then vary a little without affecting the size of the groups you can shoot with. At that point you can dispense it by either method with equal performance expectations.

Board member Dan Newberry has a system for finding such tolerant loads intentionally.
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Old January 15, 2013, 10:05 AM   #3
Dave P
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"What you want to do with accuracy loads is find one that's relatively insensitive to exact charge. That is, one that you can intentionally vary ± a third of a grain or more and not have the point of impact on the target change significantly. "


This.

When you find your Optimum Charge Weight, minor variations in load are "corrected" by the direction the muzzle is pointing as the bullet exits. Barrel vibrations and modes.

A lower charge means slower velocity, and this gives the barrel more time to swing UP. As opposed to a fast bullet, the barrel should be pointing less UP as the bullet exits.

capisce?
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Old January 15, 2013, 10:51 AM   #4
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Wow. Talk about informative. Thank you so much. The more questions i ask, the more interesting this becomes. Im hooked. I will blame it all on you all when the ups guy keeps knockin at the door. Mrs 318 no likey. Neighbors probably think shes having affair with him. She isnt is she?
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Old January 15, 2013, 11:02 AM   #5
Bart B.
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318, some interesting info's in loading charts for a given bullet and cartridge vs. charge weights of powders and the muzzle velocity atained. With a bit of grade school math, one can calculate how much change in muzzle velocity a given powder has for a 1/10th grain in charge weight for the different powders used.

One will then easily see that some powders have a big change in muzzle velocity for a 1/10th grain change in charge weight. Other, not so much. Which helps one understand why metering some powders will produce excellent accuracy through 600 yards and others not so good and have to be weighed. It's my opinion that metered charges are good enough for ranges up to 300 yards; they don't need to be weighed to exact numbers. This is what benchresters have been doing for decades. And Federal's Gold Medal Match .308 Win. ammo's loaded with metered charges and it will shoot darned near 3 inches at 600 yards in a good rifle. It would shoot into 4 inches at 600 in Garands and M14NM service rifles rebuilt for competition.

More often than not, metered charges of stick/extruded powders give better accuracy than weighed charges of ball powder. Must be so as this is what Sierra Bullets does making reloads to test their bullets for accuracy with.
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Old January 15, 2013, 11:47 AM   #6
pre64win
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For some good information on extreme accuracy search--secrets of the Houston warehouse

It is an article called "Secrets of the Houston Warehouse". Dedicated benchrest shooters used the warehouse to test rifles and loads.

Last edited by Unclenick; January 15, 2013 at 03:11 PM. Reason: Inserted link
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Old January 15, 2013, 01:46 PM   #7
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You have some excellent answers. I can only say that I don't differentiate between "plinking", "range ammo" "hunting" or "my best precise target ammo" and I load them all the same. My 50 yr. old .38 Special shooting at paper at 30' to my 9mms and .45 ACP blasting silhottes, and even my .223 target stuff for 100 yd shooting all get the same care/techniques/precision. Mebb jes me, but I enjoy it...
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Old January 15, 2013, 02:01 PM   #8
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Quote:
Mrs 318 no likey. Neighbors probably think shes having affair with him. She isnt is she?
Wouldn't be complaining if so AMIRITE?
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Old January 15, 2013, 02:43 PM   #9
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If he would pay my hazmat and shipping chgs.... I would be ok with it.
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Old January 16, 2013, 05:49 AM   #10
Mike / Tx
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Many years ago when I was just learning how to throw powder into the scale I tried my best to settle the needle right on the line, my pop would say "thats close enough pour it". We were only loading 30-06 rounds at the time. As the years rolled on I found that depending on the case capacity there is a smidge of wiggle room in most any load but as mentioned the case capacity is the rule. With '06 sized cases it can be as much as a full grain as mentioned above, but in .223 sized csaes this might be only a few 10ths of a grain depending on the powder.

In most cases nowadays I throw all of my loads. I set the measure up to hit where I want and go for it. I haven't got any BR type rifles but have some that are VERY accurate, and haven't been able to distinguish the actual weighed charge groups over the thrown charges. When you can get groups from a load which are at or under an inch at 200yds with thrown charges that might hit just above or just under the line on the scale when weighed, IMO that's close enough.
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Old January 16, 2013, 12:26 PM   #11
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I used to weight each charge, but it you do ladder testing fro load development, you may find a load that is not as particular about slight variations in charge weight.

I shot this 5 round group this weekend, with my .243 Win, using thrown charges of IMR4064 from an RCBS Uniflow powder measure:



IMR4064 is a fairly long grain extruded powder, not exactly know for precise metering, but it doesn't seem to bother the rifle.
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Old January 16, 2013, 01:53 PM   #12
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Sierra Bullets has been shooting sub 1/4 inch groups at 100 yards with metered charges of IMR4064 since the late 1950's testing Sierra 168's in .308 Win. cases for accuracy. I've seen several 10-shot ones fired consecutively that were all well under 2/10ths inch center to center some at about 1/10th inch or better.
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