I've been load testing Sierra's 155 Palma bullet in my AR10t, using IMR 4064. I've run the cycle twice of starting at 40 grains working my way up to 44 grains, with basically the same results. Sierra says that 46.1 grains of IMR 4064 in commercial brass is max and to reduce the powder change by two grains for military brass. I'm using Lake City once fired. All of these LC cases were sized, trimmed, the primer pockets uniformed for depth.
In each of the tested loads, using five shot groups, I would get one stray. At 43 grains of IMR 4064, I would have four shots in a .50 by .75 group and one shot about an inch below the group.
I had assumed it was me being unused to the rifle and the trigger, which is pretty awful.
As I was loading up a batch of the 43 grs loads, all powder charges weighed,I noticed that a number of the cases had powder levels that were much higher up into the case neck. I set these aside.
Since I had 40 cases already filled after sorting out the unusually high powder levels. I weighed the next lot of cases, sorting these cases into. too heavy, those within one half to three quarters of a grain of each other and too light. Out of one hundred cases I had sixty three 'just right' twenty-eight too heavy and the remainder too light. [A note: I used a balance beam scale. My criteria was the case had to weigh from balanced to half way down to resting on the bottom, too light.]
I filled the 'just right' cases with powder and the powder depth was the same a the other cases, filled previously.
This gives me two ways of sorting the cases, weighing or looking into the case mouth and sorting by powder depth in the case neck.
Now I need to see if my one stray shot will now move into the group with the rest if his buddies.
Jim

arkypete,

My experience with military cases has lead me to believe that variations in case neck thickness is a major factoy in random fliers. It seems that the variation causes the bullet to be miss aligned with the axis of the bore, and the result is fliers. Once necks are turned on the outside so the variation is gone, the fliers are also gone. Sorting cases by weight should also be of some help. Next time you go to the range, keep the cases from the fliers seperate and measure the neck thickness when you get home. This is usually quite an education. Good luck.

BigBob
Thanks for your reply.
What I'm going to do is... Load the three different lots of weighed cases and see where they shoot relative to the other two weighed lots.
Do you think that cases used in a semi auto would last long enough to warrent neck turning?
Jim

Don't think the powder level in a case loaded w/4064 will be a reliable indication of case capacity (weight). 4064 is quite long grained and will fall into the case differently from one charge to the next resulting in different levels in the case. Powder can be settled in the case quite a bit by tapping side of case w/pencil, etc.
Height of powder would be fairly reliable indicator were you using a ball powder.

The best method of determining case capacity is to fill the case w/water and then weigh the water.
Weighing brass is easier, however.

As Bob stated, case neck variation is common with GI brass. Not sure how hard the AR10 is on brass, but neck turning can improve the quality of your ammo. You might find it useful to turn necks on your long range ammo even if brass life is not too good.

Regards,
hm

I doubt that you are having any ammo quality issues. Are you single loading each round? Or are you sticking 5 in the mag and shooting them that way? My guess is that the flier is your first shot. Try single loading each round and get back with us.
Very little else would cause the impact change you describe. Case capacity certainly wouldn't. I doubt that being off even 2 full grains of powder would cause that much of a shift at 100yds.

Yes. In any event, please let us know what you discover. This is the kind of stuff that is really interesting!!

[ 07-15-2003, 21:48: Message edited by: eldeguello ]

arkypete,

My experience with semiautos indicates they are not accurate enought to make use of turned necks. It would take a rifle that is the quality of a match rifle to make any difference. I limited use of semiautos to 150 yords max. Within that range, the accuracy was not a problem. Good luck. Let us know how it all works out.

"My experience with semiautos indicates they are not accurate enought to make use of turned necks."

Depends a lot on the semi-auto. Assuming Arkypete's groups were shot @ 100 yds, a 3/4 moa semi-auto is definately showing promise.

A good example of good SA accuracy is the sitting rapid fire record set in 1980 of 200-18X using an M14 which finally fell last year to a bolt gun. Sitting RF course is 10 shots, iron sights fired in 60 seconds and including a magazine change, shot at 200 yards. The X ring is 3" dia. and 10 ring is 7". Most of these match rifles are capable of 1/2 to moa accuracy.

Granted, the run of the mill "company klunker" will not care if ammo is precision or not, but many match grade M1's, M14/M1As and M16/AR15s are extremely accurate and can benefit from a little extra attention to reloading details, especially when stretching the ranges beyond 600 yards.

Regards,
hm

Edited to read: Bob, the above not meant to be argumentative in the least. Agree that most SA rifles would not know if it was being fed ball ammo or super-match, but wanted to point out that there are exceptions to all rules.

[ 07-17-2003, 23:43: Message edited by: hm1996 ]

I shot a 200-12x last weekend, and I ain't anybody special so it CAN be done! Semis are very accurate!

I'd doubt the flier is due to case weight, personally. I (mis)spent most of one winter weighing Lake City brass only to realize zero difference in my groups and scores. Zip. Nichts.

I'm very curious to hear about using 4064 in the AR-10T. Some years ago, I had one of the very first ones (ser #54) and every last load with 4064 would shed primers no matter how hot or light I loaded them. Best for me was WC 852M. It also liked 173's. Weird.

Cheers

Redial

Some semi's aren't as accurate as bolt guns. This definitely doesn't apply to the AR15 and AR10.

weighing brass will make a difference in group size when using a very accurate rifle. It is just one of many procedures in loading to get the best accuracy. As far as looking in to the case at the powder lever (IMR 4064)this is only good to tell if there is powder in the case, thats it. Shake the cases and they will all look different. The only time i know of a powder level difference(by looking) is a balloon head cast compared to a standard case. Maybe you have better eyes then me.