45 gns Varget & Nosler J4: 2750 fps average w/ 3% deviation

44 gns IMR 4064 & Sierra MK: 2640 fps average with 6.45% deviation

My question is this: what is a "good" deviation spread...and does velocity consistency translate directly into accuracy.

p.s. had to put my chronying off for another couple weeks after putting a round directly through the LCD display...now that's an expensive day at the range.

Barrel harmonics are what counts...

It is highly possible to have three velocities 500 fps or more apart from each other, but if the bullet leaves the barrel when the barrel is in the same position, you will have accuracy. Terminal performance will suck, but all shots will hit the same hole.

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http://stevespages.com/page8.htm

DWM

Accuracy is putting the bullet in the same place with each shot, regardless of range or drop! (geesh!)

When working up a load for my 220 Swift, I had three loads that shot a tight 5-shot group of less than 1/2" at 200 yards. The velocities were in the neighborhood of 4300 fps, 3900 and 3400 fps. (All loads used the same cases, same powder, same bullet and same primer. The only variable was the charge of powder.)

They were, for all practical purposes, equally accurate. I selected the 3900 fps considering barrel wear.

Now, if I had sighted that rifle for 500 yards, the accuracy of the loads would have been the same, but the point of impact would have been different.

You remind me of a person I took shooting one time. I put 15 shots in one hole a little larger than bullet diameter at 100 yards. I was pleased, but the person who was with me said that the accuracy stunk, since that hole was 2-1/2" above the center of the bull.....

Cheers!
DWM

My money is on dave!

PaulS

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stay safe and live long!

For most hunting, ranges are limited 300 yards, where velocity variation is not too critical, but my 308s regularly get exercised out to 600 yards and every once in a while to 1000 yards.

Speed, drop at 1000 yards(175 gr.SMK):

2600 456.6
2626 446.4

So 1% variation is ballistically 1 MOA at 1000, not good enough for targets, but plenty good for hunting.

Barrel vibration can make this better or worse, depending on the rifle.

Don

quote:

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Originally posted by ricciardelli:
Accuracy is putting the bullet in the same place with each shot, regardless of range or drop! (geesh!)

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And how would you suggest one does that without knowing how much to raise or lower the crosshair with each different velocity? If accuracy doesn't involve drop then benchrest groups would be measured horizontally only.
Accuracy is %50 cartridge %50 gun, if you could get every round you shoot to be the exact same velocity with the exact same bullet, than you would have one of the most accurate guns in the world.

Instead of pounding on your keyboards and making all sorts of assinine wagers...read what I friggin' typed!

The key word was "harmonics"!

I never stated that a bullets launched at different velocities would hit the same spot! geesh....learn to read, and then try to comprehend!

I stated that there could be (and I gave an example of an actuality) 2, 3 or even 4 different velocities at which a group of bullets could be launched from a rifle and have the same level of accuracy! I said nothing about drop...I said nothing about the 3900 fps bullets striking the same spot as the 4300 fps loads!

As for the invite to Texas...hell, been there and have no desire to go back. I like it where the people speak English!

My question is this: what is a "good" deviation spread...and does velocity consistency translate directly into accuracy.

Generally speaking, the smaller the Deviation the better. That is true for ALL segments of reloading. Putting an actual numerical value on the acceptable Deviation creates the "opportunity" for Blood Pressure raising discussions, so it is questionable if any real good comes from it. That said, Deviations smaller than 5% are not uncommon with "many" good Loads.

Now, lets see if I can make some suggestions that "might" help you reduce that Deviation:

One of the little discussed "benefits(?)" of a Chronograph is that they often induce more questions into the overall shooting process than they are worth. If you have it a bit too close to the muzzle or if the ambient light conditions aren't exactly right, "occasionally" some of them will skew the data slightly. Now, that does not mean that all of them are worthless or inaccurate. Just be aware that some of the problem you saw "could" be "Pre-Blowed Away Chronograph" related.

But, chances are that either your actual Load needs a bit of fine tuning concerning the amount of Powder, the internal volume of the cases, a change of Primer, or perhaps you need to clean the entire firing mechanism(trigger assembly and bolt).

Both of the bullets you are using are excellent, so it is a SAFE bet to eliminate them from the investigation.

Did you "develop" the two Loads you mentioned by slowly increasing the Powder and watching the group size fluctuate, or are they randomly selected? If randomly selected, you may not be reaching enough Pressure to "stabalize" the Load. Of course, determining where the Peak amount of Pressure is, is best done with measuring the "average" Pressure Ring Expansion(PRE) on a factory cartridge and then developing your Loads in those same cases - STOPPING when you reach the same average PRE. Then backing down the Load until you get the most consistent groups.

Are you using 7.62NATO cases that you scrounged off the Range? If so, the internal volume variance could be the problem.

Have you done a full case prep routine and did you segregate the cases by weight? This gets back to insuring the same "Internal Volume" from case to case. Good consistency there means the "available chamber area" is more consistent from shot-to-shot.

Are you using an M14, or some kind of Bolt Action? If you are using a semi-auto, stick with the two Powders you are using or try WW-748 and H4895. If using a Bolt Action try the H380 with MINIMUM listed Powder Loads and those exact same bullets immediately, but don't use it with Target Loads in a semi-auto.

If any portion of the Firing Mechanism is dirty, it can possibly alter the Firing Pin impact strength from shot to shot. So, make sure the Trigger Assembly has been spray cleaned and disassemble the Bolt to give it a thorough cleaning and a VERY LIGHT re-lube.

As a final thought(if you are a Swabjockey), aim slightly higher when using the Chronograph in the future and don't stand in front of the Blast Fence! ;^)

Good luck to you and SEMPER FI!!!

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Good hunting and clean 1-shot kills, Hot Core

[This message has been edited by Hot Core (edited 02-06-2002).]

And, I do believe these other folks can give you some "great, useful info" if we can get their focus slightly readjusted. Maybe even better scoop than what I can give you.

But, let me take another run at it too.

fa18hooker: .....I'm using (or was using) a Shooting Chrony F-1. I got this because I heard that chronys are chronys, and all essentially the same accuracy. Do environmental effects (height of bullet over chrony, light level, etc) affect the reading (i.e. I thought if you got a reading, it was accurate).

HC: I really think the other folks can help you better on this question than I can. That said, the chronographs "I've messed with" all worked on the shadow of the bullet crossing the sensors. So, if the sun was at a wierd angle or in some cases directly overhead without the diffusers in place, the readings would "occasionally" be suspect.

The biggest mistake I've seen people make is having the distance between the screens wrong, having them too close to the muzzle blast or when using the "fold-up" chronographs not getting them open to the alignment mark.

I've worked with an Oehler 35 more than the rest because it is owned by a Gun Club that one of my buddies belongs to. It seemed to be less sensitive to "hitting the window" above the sensor, but don't put a lot of value on "my" assessment of chronographs.

Hopefully the other folks will jump back in and share their knowledgeable experience concerning them.

fa18hooker: Some background on my case prep. I used once fired, same brand commercial brass, full length sized, primer pocket reamed, trimmed to length, primed with cci large rifle, and the powder/bullets listed.

HC: Good start. I would recommend you chamfer the case mouth with a Lyman VLD tool and then "Polish" the mouth. Wrap some "0000 Steel Wool" around a Bore Brush and put the brush into that Lyman VLD wooden handle. After Chamfering and Deburring, run the case onto the brush(into the Steel Wool) and give a couple of twists. This will totally remove all burrs on the case mouth and make them as slick as Clinton Lies(Well... almost that slick!).

Removing the burrs helps "eliminate" another opportunity to put a nick in the base of the bullet when you seat it. And, you want those bullet bases pristine.

"Same brand"(of cases) helps, but same "Lot" is even better. I would recommend that you "weight sort" the cases after you do the Full Case Prep. I normally buy 200-500(same Lot) cases for a new rifle, do the Full Case Prep and then weight sort them. There are some folks who believe Weight Sorting is a waste of time, but that is what I do to "my" cases. And (unless you intend to shoot against me for a BBQ supper), I'd encourage you to do the same. If you do elect to do this, let me know and I'll detail the way I do my weight sorts.

Use those cases and get some Match Grade Primers. They may or may not help tighten the groups and reduce the velocity variance. Changing Primers is kind of a "Fine Tuning" step, but can have a significant effect on the Pressure "IF" you are working near MAX.

fa18hooker: I'm shooting a Remington 700 in .308, which I think has a 1:12 twist (haven't checked it). It can drive tacks at 100 yards, but I now want to do some long-range target shooting.

HC: Sounds like a Plan to me. Since that is the rifle, I'd recommend either of those bullets, Nosler or Sierra, but I do like the Sierras the best. I even shot a couple of boxes of 168gr Hornady Match Part# 30501, last year and was able to cut some 3s. It amazed me, cause about the best I'm capable of any more is the 4s when my concentration is up.

Anyway, pick one of the 168gr Match quality bullets and fuel it with the "Minimum" loads shown for H380 in your Component Manufacturers Manuals. Develop up in 0.2gr increments "only if needed" to hit a good harmonic, but don't try to turn it into a 300WinMag.

Seat those same bullets so they are "into" the Lands 0.005". When you put the bullet into the case mouth, do it with care. EASE the ram up so the bullet EASES up against the Seating Stem. "Lightly pat" the handle to ensure proper bullet alignment and then seat the bullet smoothly and slowly. Some folks say to rotate the case 180deg and re-seat which helps with "Run-Out". I don't, but if it helps them, then I'm all for it.

This is out-of-sequence, but I'm an advocate of Partial-Full Length Resizing(P-FLR) for the utmost accuracy. I know a lot of folks get bent out of shape when I mention that "for me" P-FLR is more accurate than Neck Sizing. Once you understand that the case CenterLine is closer to the Chamber CenterLine when P-FLRing than with Neck Sizing, it becomes technically clear why it works better for "me".

To P-FLR a case, start with about a "Nickles" worth of gap between the bottom of your Full Length Die and the top of the Shell Holder. Lube and resize the case. Wipe it off and try to close the Bolt ALL THE WAY DOWN with that case in the chamber. If you can close the bolt, screw the Full Length Die into the press 1/8th turn and do it all again. At some point, you will feel the effort needed to close the Bolt "Increase". Now you are real close. Barely screw the Die in a bit more and resize it again. Go until the bolt closes with just a bit of effort and set the Full Length Die Lock Ring so when you unscrew this Die from the press you can get it back in to this exact same position.

Now your cases are P-FLRed. The Bolt Face will be pushing against the Case Head and the Chamber Shoulder will be pushing against the Case Shoulder. This slight stress on the case causes the CenterLines of the Case and Chamber to be in a very close alignment.

As a next to final thought, depending on your scope, you can possibly run out of adjustment for w-a-y out yonder. If that happens to you, get some of the Burris Signature rings to fit your current base and get a set of their "Eccentric Inserts" to go with them. Then you can readjust the scope to work up close as well as way out there.

And as a final thought, have your trigger adjusted so it breaks like a piece of glass. Any "competent" Gun Smith can make a Remington trigger work very well.

Good luck to you. The actual groups shot at the longer distances will "probably" tell you more about the Load than anything else.

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Good hunting and clean 1-shot kills, Hot Core

I noticed you're using the F1 Chrony and I used to have one also. I'm not just saying this because they are inexpensive, but if your serious about SD's get rid of it and buy an Oehler 35P period. I had two, one was an Alpha the other the F1 Master, and set them one in front of each other they would always give velocities as far apart as 150fps and routinely switch which one was faster. I would say they were on average 75fps off. The screens aren't spaced far enough apart is one problem.

I now have a model 35p and a model 43 both which laugh at the Crony brand and DARE them to even try to come close to the accuracy needed to measure SD. If you want anything more than a rough estimate of velocity, your wasting your time with a Crony brand crony. If you ever check it against an Oehler you'll demand your money back.

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Brent

quote:

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Originally posted by ricciardelli:

You remind me of a person I took shooting one time. I put 15 shots in one hole a little larger than bullet diameter at 100 yards. I was pleased, but the person who was with me said that the accuracy stunk, since that hole was 2-1/2" above the center of the bull.....

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Hrmm you took my neighbor shooting i think. He never could understand why i sight all my guns in at 2" high @100yards.

He is also the same moron who sighted a gun in at 2" low. "I rarely shoot 100yards at deer and i dont feel like messing with the scope."

I have a match 308 I was trying to find a load for the past 2 months---I started out using 150 match Sierras---once I found that one Imoved up to the 168 match------couldn't group worth a hoot----I changed primers & eventually dialed it in-----I then loaded 12 rounds exact same powder & charges----ONLY used 4 different primers------the primers by themselves moved groups 3"
CCI magnum----Win. LR---Fed. match--Rem. 9 1/2--------had I not done this myself or watched it I would never beleive the amount of spread--------I did not use a chrony but just observing groups I would say there was an extreme spread in velocity---accuracy with 150-s Rem. 9 1/2 accuracy with 168-s Fed. match