Lapua vs PMC

[1johnlb]

I've recently picked up a 30/06 slow twist barrel and have been in preparation mode and picked up some brass, Lapua and some of the recent Pmc that's recently come avaliable. I've never done any weight sorting but decided to with this rifle. I was very surprised and somewhat disappointed with the lapua.
The PMC came out with approximately 80% being within .1grs of each other and the other 20% being about .7grs varied. But the Lapua which I paid a premium for was all scattered in weight, in about a 1.8gr varence with no more than 10% falling within a .1gr weight.

I'm happy the PMC was so close but I'll never buy anymore lapua at that price, unless it shows some kind of superior trait over time.

[EDG]

Put the brass weights into .2 grn or .5 grain bins and graph the results.
PMC in one graph and Lapua in the other.

The resulting curves will tell you a lot about the 2 sets of brass

[1johnlb]

Ok, how do I graph the brass?
Write the results of each piece?
Distance and position of each shot?

[CHeatermk3]

30-06 brass weighs about 200 grains so a 2.0 grain variance would be 1%. If the heaviest weighs 198.0 grains and the lightest 196.0, that's + or - 1.0 grains, just as an example.

I use a sharpie to write the weight on each piece as I weigh them. If you're going to use them for match shooting just number them from the lightest to the heaviest and then shoot them in order this will insure that each round will be as close as possible to the next shot fired, assuming all other factors are equal. If your boolits vary too(don't they all?) I would sort them and then load them in the reverse order, lightest-boolits matched to heaviest-cases. Shoot them that way then judge by the results. You'll want to fireform them after match prep anyway.

I'd think that the variation you're seeing will not make as much difference as controlling the major factors like concentricity/alignment boolit-to-bore and case wall variation.

[1johnlb]

Thanks, I didn't write the weight on them but did sort them in the case from lightest to heaviest. Not match shooting, just looking for the best possible results or at least better for me.

[Mike H]

I've recently picked up a 30/06 slow twist barrel and have been in preparation mode and picked up some brass, Lapua and some of the recent Pmc that's recently come avaliable. I've never done any weight sorting but decided to with this rifle. I was very surprised and somewhat disappointed with the lapua.
The PMC came out with approximately 80% being within .1grs of each other and the other 20% being about .7grs varied. But the Lapua which I paid a premium for was all scattered in weight, in about a 1.8gr varence with no more than 10% falling within a .1gr weight.

I'm happy the PMC was so close but I'll never buy anymore lapua at that price, unless it shows some kind of superior trait over time.
Why don't you shoot a number of groups with both lots unsorted and see what the result is.You will want to be good to show that the PMC is better than the Lapua.
Mike.

[GabbyM]

I think you are placing to much value on case weight deviation.

[Hickory]

I think you are placing to much value on case weight deviation.

This is my thinking also.
With a "slow twist" in a 30-06 the bullet will be on the light side for best shooting, 150 grs or less.
Ranges will be on the close side 250 yards or less. A gun like this is best suited for paper or varmints. But you never mentioned what you intend to do with it, or how accurate it needs to be.

[joesig]

Lapua is known for flash hole uniformity.

[GabbyM]

For cast boolit shooting. Uniform neck tension is king. Then all the other things. Plain and simple. If your shot to shot bullet pull varies your E.S. will be high.

[fryboy]

c.c. aka cubic centimeter ( capacity ) sadly can mean more than actual weight , and i agree with the neck tension but ... it also applies to j-words as well

[Harter66]

I had a fast twist 06' when I found the load that was the load . Just .3 of a gr of 4350 moved groups for 5 touching to 1.5" . 1.0 gr went to 4" .

When I first started with it I had about 150 LC loaded factory m2 . It would shoot generally 2 within an in and 1 over there some place . Being irritated with it I sat myself down with the last 80 and worked on trigger control and breathing. When I was done I went to see what it looked like fully expecting to see an 18-24 inch pattern. What I found was 3 very clear 3" groups and a few flyers. The groups were at 12 ,5,8:00 . So I went home and tried to figure it all out. I came up with case volume/weight it was all LC 43 so it should have been close . What I ended up with was 3 lots of 1gr or less and a few way over/ under the lots matched up exactly to the group counts and flyers . 195.5 to 199.3 with and abortion of 187 and 203. More than that the water volume was off 4 gr gross (the 187 holding 4 gr more than the 203.). There was 8" between group edges . All at 100 yd . I took the biggest lot and worked a load in just 5 cases while using the smallest lot for a practice load . When I hit the load I used 5 more 1x to prove the load for 3 cycles of 10 rd. Satisfied with it I loaded all for the hunting load ,all 35 ,carefully scaled and sealed.

Most rifles aren't so fussy but that 1 was. I don't know how much difference 1gr of brass or.7 gr of water makes in any given rifle but in that 1 it made a 5 holes touching 2 touching 3 touching 8" apart 10 shot group when mixed . I have had several that didn't care about 2 gr of case weight . That 1 taught me volumes about nearly invisible differences in cases,you know after the bleeding from my forehead stopped from the wall banging.

[CHeatermk3]

John, if you have your cases weighed you could just number them 1-100.

It would be nice to know what level of accuracy you need and what purpose the rifle will be used for.

If you have a ball or tubing mic. or a case gauging fixture, you could find the thin or thickest side of the case wall and mark it--I do this for match cases by filing a small notch on the "rim" of the case on the small side (indexing mark). This way I can set the case in my rifle's chamber the same orientation for each shot.

HTH

[Hawks Feather]

I think you will find that the Lapua have flash holes that are drilled and the PMC will be punched. If you look inside the flash hole of the PMC you will probably see the small pieces of brass that remain. For most shooting you won't notice it. If you are looking to get the most out of the PMC I would work the flash hole.

Shooting and group size will be your best way to judge the two lots of brass.

[1johnlb]

The rifle is strickly bench target, punching holes, unless a deaf dumb deer just happens to walk out on my range while I'm shooting, then it's a lunch rifle. I built the rifle for HV following after the xcb threads with the intent to stay with factory chambers and associated tools.

Only recently, have I really, with the xcb threads, began to modify my reloading and casting techniques. Trying to get out of a plinking mindset. Now trying to look at every aspect and perfect my techniques to abtain repeatable accuracy or at least increasing my consistency in the reload room and, on the target. I've been a shooter all my life since dad put that 22 in my hand at 8, but only reloading and casting about 7 years and since coming here to the CB's forum a year ago, I've surely have learned how little I know. So, trying to put the best foot forward with this new barrel and cover all the areas within reason, for a backyard plinker, without having to hire a pit crew.

[M-Tecs]

Take your five lightest and your five heaviest Lapua brass and load. Do the same for your best 10 PMC. Shoot a 10 shot comparison group for each. See how they compare on the only truly important inspection criteria – group size.

Weight is only one component of what makes some brass more accurate than others. Do your own testing and draw your own conclusions.