Powder thrower tolerance for rifle

[ibdecent]

I'm relatively new to reloading and i'm addicted. i absolutley love it. I mainly load for my deer rifle right now due to lack of funds to load all my guns. Anyway, I bought an rcbs uniflow. I've done extensive "testing" and I get about +/- 0.4 grains. the gun I load for is .325 wsm in a win m70 (got it for $300 brand new) I don't have the load data in front of me but IF I remember right the barnes manual calls a minimum load of 56.5 grns and max load of 62.5 grns. i can't remember what powder right now.....SO WHATEVER YOU DO, DO NOT USE THIS INFORMATION TO LOAD. It is an extruded powder, but it doesn't cut very often. In my "testing" I made note of the charges that it did cut, and they still fell within the +/-.4 grains range. I do use a trickler right now, since I am new to the hobby and I am working with explosives, and I believe that I will continue to do so, unless I'm working with loads for different calibers. I'm not overly worried about the extra time to measure each individual round when I'm only loading 1-20 rounds and I do like consistency.....

To get to my question...

1) Would anyone out there consider this +/- 0.4 gr variance to be acceptable, and why?

2) What causes it?

3) Would a powder baffle help this problem?

any other little interesting tidbits would be appreciated too.

P.S. I'm not really interested in getting harrassed for the large caliber for deer hunting. It's all about shot placement and I can put them 1 moa no problem. I bought it cheap as I said and with this rifle I can hunt nearly anything in the world, should I choose to do so.

[DaveInPA]

.4 is way too much variance. I use a Uniflow and don't get anywhere near that type of spread. I use a powder baffle, and it may very well help you. It's also important to use the same technique/motion every time you throw a charge.

[mkl]

A powder baffle will help, as will using the "double tap" technique.

Handle down smartly, raise about an inch and down smartly again. Tap,tap.

Handle up smartly, down about an inch and then up again. Tap, tap.

I use the word "smartly" to indicate the measure should hit the stops rather hard (twice) on each up/down stroke.

The firm strikes against the measure stops done twice each direction seems to really help settle the powder in both the hopper and the volumetric chamber of your measure.

I'd think +/- 0.2 grains for extruded and +/- 0.1 grain for ball powders would be reasonable objectives with the RCBS Uniflow measure.

[PCJim]

IB, here's what I do for all my .243 rounds (don't belittle me for being on the opposite end of the hunting calibers ). I use either a dipper or the powder throw to get "close" to the charge I'm loading, then trickle finish so that the charge is exact. Kind of the best of both worlds - powder throw to speed up the process, trickle finish for accuracy.

[Brian Pfleuger]

I'm sorry, I can't resist....

I am new to the hobby and I am working with explosives,

Technically, smokeless gun powder is not an explosive.

[Archie]

=/- .4 grains may or may not mean anything.

What percentage of the total charge weight does .4 grains represent?

In a .32 ACP, .4 grains is about a 50% variation. In a .30-06 load, it's less than 1%. In your .325 anything with a charge between 56 and 63 grains, that's a negligible amount.

Frankly, minor powder weight variations are the least important component of accuracy. Trim length, case weight and concentricity of bullet and case are far more important. However, charge weight is the easiest to get right, so most people concentrate on that aspect.

Chronograph five or ten rounds of a load and then chronograph another five or ten rounds of the same load but one grain more (or less). I'm willing to bet the range between the highest and lowest round from one string will be more than the difference in average velocity between the two groups.

Then check a drop table and see how much difference in drop the differences in averages causes at any realistic range.

You'll probably find the difference in drop is a good deal less than the average group size of your load at that range.

Your questions:

1. It IS acceptable in this cartridge.

2. It is caused by stick powder not filling up the chamber in the measure uniformly from throw to throw. Ball or spherical powder is smaller and fits into a space better.

3. Powder baffle can't hurt.

However, it's not worth getting all twisted over. Load some ammo, test it for accuracy and see how it shoots. Unless you are on the upper raggedy end of the charge weight, a little variation is not going to cause any problems with pressure, either. If you are running loads where .4 grains more will be dangerous, the load is already dangerous.

Stand by to have others tell you I am wrong.

[Hydraulicman]

+1 load and shoot.

What is this batch for? Target , hunting?

[Hook686]

+/- .4 grains might be a bunch, but if that is what you are dealing with, then that is the situation. I can get that variance with Unique powder in my Lee Classic Turret.

In you situation with low of 56.5 and high of 62.5 grains, I'd shoot (pardon the pun) for mid point, say 59.5 grains. Then load 10 rounds, pausing after the powder drop to weigh each charge. I would place each round in the ammo box carefully marked with powder weight.

Then to the range to shoot them. I shoot light to heavy and record the fps, using my chronograph. I would keep track of bullet velocity and point of impact on the target.

Since this is not bullseye shooting, I seriously doubt that the shot placement is going to be significantly more severe than my usual shot placement, a couple inches at 100 yards.

Will my rifle angerly respond to a round with 59.1 grains, or 59.9 grains ? I do not think so, as this range is well within the load range.

I simply do not have a problem with this kind of variance, less than 1%, but then I load mid range.

[ibdecent]

Thanks all. really appreciate it. I haven't heard of the double tap method and will definetley give it a shot. and i will also get a baffle. I may aslo try different powders, just because I haven't yet.

they are hunting loads, so i'm not concerned about them being outstandingly accurate, but I do expect at least 1.5 moa. I get 1 moa from factory loads so, it'd be nice to beat that or at least match it.

I wasn't overly worried about the variance, I didn't feel it was acceptable, but I mainly wanted to know why.

Thanks again, I'll see what happens.

[30Cal]

I'm guessing you'd have a hard time seeing a difference on paper if you loaded up a batch with +/-0.4grs and +/- 0.1grs and shot them at ranges inside 600yds.


The key to getting good consistant drop is smooth, consistant operation.

[farmall]

I'm kind of a collector of powder measures, and have begun to form the opinion that the only people who have powder measures (mechanical that is) capable of +/- .1-.2gn accuracy are: Santa Claus, Tooth Fairy, and the Easter Bunny.
I have found the Lee Perfect Powder Measure to do better with extruded powders than anything else I've tried.

I'd weigh 10 thrown charges, and if none exceded max, run with them. Most benchresters use powder thrown by volume, not weight.

Andy

[Shoney]

Unclennick has a wonderful web site where you can download (free) the patterns for baffles.
http://drop.io/unclenick

I have double baffled all my PM's with these cut from pop cans, and they work well!

[darkgael]

Four tenths of a grain in just about any rifle cartridge is not worth worrying about. You are better off spending the time and energy shooting.
Pete

[Ruger4570]

As long as you aren't at the very edge of sanity, .4 gr ain't the end of the world in a rifle. Personally, I weigh each throw whenever I get to the "upper" limits. If my loads are something less, I weigh a charge or two and then go for it.
I'm still here so the method has worked so far. Generally, unless I get anal about it, I try for a tenth of a grain loading accuracy. But if I am REALLY serious, I can weigh even closer with my balance scale by splitting the lines and spaces. Best of luck to you and learn to enjoy reloading.

[Shoney]

I don't meanto go against the grain here, but +/-0.4 gr is significant. That means you will have cartridges with a variance of 0.8 grains.

In the smaller cases that is enough variance to spray your pattern. An 0.3 grain variation will result in a 1" group difference. In larger cartridges 0.3 grains will result in 1/2 to 3/4 inch group size differences.

If the variation is +/-0.2 grs would be more acceptable. If you are willing to spend over $250 on a Harrel PM then you can throw and not worry about variations of less thab +/-0.1 gr.

If you never want to worry, get a Promethius. It will throw within +/- 0.03 gr. Yes that is correct, +/- 0.03 gr. They are only a mere $1200+.
http://www.6mmbr.com/prometheus.html

[Bart B.]

I'll bet a completely worn out barrel and 2 ruptured cases that there's more muzzle velocity spread caused by variance in primer detonation than a .1-grain spread in a 40-gr. powder charge weight. Especially if the rifle's firing pin spring is over 3 years old.

Considering the fact that some .308 Win. match ammo loaded with a .35-gr. spread in powder charge weight shot about 1/2 MOA in several different rifles at 600 yards (it would have to be under 1/4th inch at 100 yards to do that), I'm convinced there's more important issues for best accuracy than powder charge weight tolerances.

In the article shown in this link: http://www.angelfire.com/ma3/max357/houston.html

...note the paragraph that says:

Powder charges, as long as they were fairly consistent and bracketed within a couple of grains, were not important, he said. On one occasion, as an experiment Virgil shot one group with his 6PPC barrel on the Cooper action using a 53 Culver setting of Winchester 748, the next 52 and the third 51. All three groups were identical.

[sourdough44]

For low volume hunting rounds just weigh every charge, not that .4 gr of 65 is a big deal anyway.

[GeauxTide]

When I used a Uniflow and any stick powder, I'd set the handle so that it loaded the chamber by pulling down. I'd pull down sharply, also. I'd typically be off .2-.4 grains, so I'd trickle up to correct weight. One other thing I've done is forget to install the large cylinder in the Uniflow.

[wncchester]

A baffle is easily made of sheet metal or plastic. Baffles do help with consistancy but they aren't magic, the dropped charges will still vary.

Volume measuring of a coarse material can never be totally consistant. Good technique with the measure can help but only you can find if you do better with two taps, one or none. Just a single tap at top and bottom of the stroke works best for me and my old Redding.

No hunting load, properly developed and used, will see much effect from a couple-three tenths difference, +/-, in your charges inside 400 yards of so. If you keep track of the results of changing charges by two or three tenths when developing loads you will likely note that there is a sort of "window", or charge range where accuracy will be pretty much identical. (Ditto with bullet seating depth.)

If you load in the middle of those windows, small variations later will mean nothing to your accuracy. But, if you load at the ragged edge of the windows, tryng to achieve highest volocity perhaps, even small variations in charge, seating, primer, or cases themselves can blow your groups.

[freakshow10mm]

I would not tolerate a variance of .4gr ever for any application.