300 Win Mag Lapua brass neck thickness

[flyfisherman246]

I have been shooting and building .300 win mags for years with the same reamer. I seated bullets in winchester, federal, hornady, norma, and remington brass and they were all around .336 loaded neck diameter. I was excited to see that Lapua came out with win mag brass so I picked up a box. Loaded some test rounds up starting very light and some of the rounds would barely fit into the chamber or not at all. I took some measurements and compared it to my .340 neck reamer. The loaded neck diameter of a new lapua 300 win mag brass was .339 which would give .0005 neck clearance on each side. This wasn't going to work. I turned the necks on the brass and now all is well, but the problem came when prior customers called me up saying their lapua brass doesn't fit in the chamber. I just assumed maybe I ordered my reamer with too tight of a neck. I called Manson reamers to get a new reamer ordered up. After talking with Ray for a while, he went through looking at multiple "match" style .300 win mag reamers out there and they were all in that .339-.340 range. Even SAAMI spec chamber has a neck that tapers from .3421 to .3407. Even for a factory chamber that Lapua brass would be too tight. I reached out to Lapua about this to see what I should do moving forward and this was their response:

Zack,
Since LAPUA brass has to be made to the European CIP specifications. There can be differences between the specification ranges between them. Because of that LAPUA brass can be to the thick side. When they came out with the 6BR brass you had skim cut the necks to fix this same issue. You may want to try a reamer that has a neck diameter .002-.0025 larger than the measurement across the neck of a loaded round as a possible solution here that won't have as much effect on the other manufacturers brass.
Hope this helps.

So now I have to make the choice of ordering a reamer specifically for Lapua brass with a neck of about .343, but then that would be .009 oversized of all other brass out there.

I'm not at all complaining, just want to hear other peoples experiences and potential solutions to this.

Thanks,

Zack

 

[rustyinbend]

Maybe I'm not understanding the issue correctly, but have you thought about using a FL Bushing Die to down-size the neck on the cases with the larger necks? Is that something that could work?

 

[Evintos]

Put a disclaimer that tells your customers that neck turning would or might be a requirement for some brass like Lapua and the Manson 300wm Match reamer; let them know what neck wall thickness they should turn their necks to.

Also offer an option for a 300wm Match Manson reamer specifically for Lapua brass but have a disclaimer that you don't guarantee performance (if you offer any to begin with) if they use non-Lapua or thin neck wall brass in that chamber. Call it like the 300WM Match thick neck/no turn reamer option.

Have the disclaimer font in bold and larger font size near the selection/options section (drop down menu, form, etc.) that the customer would have to agree to before adding to cart or something.

 

[FredHammer]

Maybe I'm not understanding the issue correctly, but have you thought about using a FL Bushing Die to down-size the neck on the cases with the larger necks? Is that something that could work?

No it wouldn't help. Only reducing the thickness of the neck will grant more chamber clearance for bullet release. So, neck turning would be mandatory.

 

[FredHammer]

@flyfisherman246, I see .342 neck chamber dimension for .308 reamers considered, "No turn" for Lapua brass.
There is debate as to what is the optimal clearance, but looks like the competition crowd is going with more total clearance lately with min .004.

 

[918v]

Can you open up the neck using a boring bar?