338LM Chambering/Headspace

[madmax56]

Hi guys,
sitting in the shed going through my case preparation, and had a question for those who know such things:
How does the 338LM chamber? i.e. 9mm pistols chamber on the case neck. Does the 338LM chamber on the ends of the case in the neck, or on the shoulder or it is straight head space?

I ask this because after 3 firings of the Lapua cases I have I have noticed the rounds are a little long and need trimming, which I am doing now. The bolt was getting stiff to depress into the locked/Action condition. I have full length resized prior to trimming to length.

Any assist appreciated.



Max

 

[kgreylgrey]

Re: 338LM Chambering/Headspace

A stiff bolt when loading a round can be from excessive case body diameter, excesive headspace, excessive case length, excessive head diameter or excessive OGIVE length (too much bullet jam into the lands).

Can you chamber a fired round without any noticable bolt resistance/stiffness? Are you bumping the shoulder when you FL resize - what is the difference between the headspace of your fired rounds (that will chamber without any noticable bolt resistance/stiffness) and your reloaded rounds? Does your headspace lengthen when a case is resized? Sometimes the way you setup a die and lubricate the case and can cause the headspace to lengthen upon resizing.

Is the head diameter still within specs?

FWIW, I've noticed that after two firings with new brass, I need to trim. This is faster case lengthening than I've seen on other calibers and may be indicative of the .338LM or just my specific load. Anyway, the rest of my cartridge dimensions are within specs, so I'm not concerned.

As a rule, I have established maximums values for what I will accept for headspace, case length and head diameter and I check these values during the reloading process. If a case exceeds those maximums, I either correct the problem or trash the case. I can generally correct excessive headspace and case length, but I always trash any case with excessive head diameter.

Hope this helps.