Neck wall thickness variation w/Lapua 6.5-284

[smike308]

What is the typical range of neck wall thickness on Lapua 6.5-284 brass? What would be considered acceptable and what would not be acceptable if sorting the brass? These questions pertain to new unturned brass. I will be turning these for a .294 chamber. TIA

 

[22Mag]

I had my reamer cut with a "no turn" 0.298 neck. All of my cases I have loaded have mic'ed in at 0.295 to 0.296. I have loaded about 400 rounds so far, none less than 0.295 and none more than 0.296 so far. I think the lot I have shows very good neck thickness variation. This is with Lapua brass.

22 Mag

 

[smike308]

22Mag--
Thanks for your help. Have you done a clean up cut on your case necks? Have you measured the neck wall thickness on your brass? Just curious. Thanks again for your help.
Mike

 

[Rust]

The last two batches of Lapua brass were extremely uniform with barely .001" variation in a representative sample from both batches. Basicvally it all measured .015", after neck sizing with a Redding die with bushing and carbide expander ball and after chamfering the mouth. Unchamfered the cases will give more variation as the factory chamfer leaves a little burr here and there.

The one thing I do recommend is get the brass first, measure it and get a reamer to match the loaded rounds with about .003"-.004" of clearance. Going any tighter can cause extra work for little or no additional gain. At least IMO. My theory is that with the bullet seated into the lands the case neck should not be in contact with the chamber anyhow, at least if the loaded round has no runout, and then the benefits of the tighter clearance are better sealing,the case expands less to seal the chamber), less work hardening of the neck due once again to less expansion required by the brass, and increased case life.

The only drawback to the 6.5 X 284 is that there isn't a perfectly matched powder in my experience, H4350 works best for me giving by a tough better accuracy and better ES/SD numbers but as it is a touch fast at the expense of a slightly decreased barrel life. RL-22 has worked nearly as well in the two lot numbers I've tried although I had some very stubborn fouling that worried me.

But for pretty much off the shelf cartridge, the 6.5 is possibly the best compromise for 1,000 yard for most folks.

 

[smike308]

Rust--
Thanks for responding and helping to clarify some of the areas I had questions about. I received my brass the other day. It appears to have greater inconsistencies than what you experienced with yours. So far, the samples I have checked have run from .0155 to .0135. My rifle, which is being built presently, is to have a .294 neck. It looks like I wouldn't want it any thinner than it is on the thin side.

 

[Rust]

Unfurtunately, brass tolerances are always an issue. The 6.5 X 284 in particular is difficult to manufacture given the great difference in the diameters of the case body compared to the neck and the sharper than average shoulder. I am kind of surprised that you had that much variation. I check mine with a Sinclair tool with the Sinclair neck inserts,vice the less expensive inserts) and a Starrett dial indicator. Feel and touch affect the consistancy of the results too.

The reason I say I'm surprised is that I picked up a large quantity of Lapua .308 brass and it's all very nice too, virtually no neck thickness variations.

One thing I will recommend is that when turning brass that does not have a shoulder angle matching the two commonly available cutter blades, find a tool and die place and have them grind to match the shoulder angle, it helps prevent notching the bras around the neck to shoulder junction. Makes life a little simpler and can save you from little mistakes.

I ain't the sharpest tool in the shed all of the time so little things like that help keep down the embarrassment level.

 

[smike308]

Rust--
Thanks again for the info. I was disappointed in the variations I found, that is why I posted the original question. I am measuring with a tubing micrometer. The results I'm getting are repeatable when I recheck my measurements. I think they will all clean up OK when turned,I hope). Thanks for the tip on the cutter. I am going to order a 40 degree cutter from K&M tomorrow. I know it won't match perfectly, but at least it won't be cutting into the shoulder. Thanks again for your assistance.

 

[rstreich]

I know it won't match perfectly, but at least it won't be cutting into the shoulder.

Just remember, when turning necks, you need to cut into the shoulder some. Well, you need to take a solid bite into the neck/shoulder junction anyway. If you don't have shiny brass out on the shoulder after you fireform, you'll have donuts.

 

[smike308]

rstreich-
How far down onto the shoulder do I need to go with the cut?
Thanks-

 

[rstreich]

With the standard K&M cutter, you feel a good bit of resistance when you get to the neck/shoulder junction. When I hit that, I just give it a little extra until I see a solid sliver come out of that corner.

If possible, try one, fireform it and see where the edge of the neck turned area comes out, before you move on to the rest of them.

It's trickier with the shoulder angle on the 6.5-284 brass 'cause you can peel off some of the shoulder on some cases. I haven't had any problems with a case that's happened to, but it's a little disconcerting.

 

[Rust]

When I first turned brass for the 6.5 X 284,had to because of bad neck thickness variations) I noted that the cutter hit the shoulder before it got to the neck/shoulder junction by just a hair. Took it to the local tool and die and had them regrind the angled part of the cutter to 35 degrees to match the case.

Now I'm set up with a large amount of Lapua brass that doesn't need to be turned but IMO if you need to turn, match the cutter angle to the shoulder of whatever case you are using. I do notice that Sinclair does have a 40 degree Ackely angle cutter.