338 Lapua & Crimping

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mdblough

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Hi All,
After about a month of getting all of the gear and information together I am ready to start reloading my 338 Lapue cartridges. The one last item I am uncertain about is crimping. I picked up the RCBS die set, which describes the procedure without crimping, with roll crimping, or taper crimping. From some store bought cartridges it doesn't look like 338 are normally crimped, but before I complete this final step I wanted to double check with people that would know far more than me. Also, I was hoping someone could briefly explain when/why crimping is necessary so I know for future reference.

Thanks in advance,
Mike
 
Crimping the bullet is done in order to keep the bullet from moving back or forth from the original seating depth it was seated at if the cartridge is jerked or bumped with force.
This is more of a concern for bullets that are placed in tubular magazines where one bullet is pushed against the one in front of it or in very heavy recoiling rifles where there is a concern that the cartridge would get bumped around in the magazine forward and backward and would push the bullet further into the case.
By not crimping you would increase the life of the brass.
Considering you are invested in the brass and would like to get as much life as you can out of it you may elect not to crimp. Document in your log if the cartridge is crimped or not.
Assuming accuracy is key factor for your reloading procedure keep things consistent and good record keeping helps.
You can try crimped Vs none crimped.
I do Like Kevin mentioned by keeping a reasonable and consistent amount of neck tension and I do not crimp.
I have tested in my 338 if neck tension alone without crimping will hold the bullet in place in the magazine which it does.
Had rounds in magazine and fired off some rounds (not from the magazine), Measured COAL prior and after shooting several rounds and no changes in the rounds in the magazine so im happy with the amount of neck tension that I have on the bullet without crimping for my needs which are shooting from a stationary position.
Hope this information helps.
 
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Thanks! So for my use I will not need crimping. My follow up question, and I apologize if this sounds naive: for someone just starting out in reloading how concerned should I be about neck tension? I have the basic RCBS reloading dies (Full-Length Sizer Die with an Expander-Decapping Unit, and a Seater Die). Neck tension isn't mentioned in the RCBS manual, so I am assuming with this die set it is not adjustable? Any feedback would be much appreciated!
 
If you are just getting started with the art of reloading I wouldn’t freak out about neck tension to much but here is a way to help you find out what is the current neck tension you may have on your bullet. Basically how much “squeeze” is applied to the bullet by the neck.

Step 1 Measure the neck OD of a resized brass without bullet seated. Write the number down.
Step 2 Seat the bullet and then measure the neck OD again and write the number down.
Subtract the step 2 from step1 and divide by 2.
For example:
Neck OD without seated bullet is 0.376
Neck OD with seated bullet is 0.382
So… 0.382 – 0.376 = 0.006 => 0.006/ 2 = 0.003 of neck tension.

NOTE: actual diameter numbers are random and are not actual measurements of 338 lapua brass

As a side note: You may consider investing down the road in a neck sizer die only in order to reduce work hardening the brass in order to prolong its life.
If you want to get picky with neck sizing dies and neck tension than redding does offer a neck sizing die that you can use different inserts for different neck tensions, like the die that kevin M mentioned.
 
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If you are seating mag depth crimping can be beneficial as long as you have consistent neck thickness and tension. Light/medium-medium crimp will give best results and I would only use the Lee Factory Crimp die. If you are going to hang closer to the lands forget crimping and go with .002" of neck tension your go to neck bushing for Lapua brass is .365" its also a good idea to have a .364, .366 and .368 for variances in neck thickness as well as sizing your neck down in increments of .003" this will give you more consistent neck tensions and keep from overworking your brass. Remember if you want your brass to last size it in small increments and remember dwell time of each OP should be a 5-10 sec count depending how large the cartridge is .50BMG is a good 10-15 count per operation. Most important on .338LM and larger cartridges annealing is a very important operation to have long brass life and consistancy.
 
mdblough

The average die over resizes the neck making it smaller in diameter than needed, then the neck is pulled over the expander to make it larger.
Without measuring tools the old thumb rule was to hold the case and push on the bullet on your reloading bench. If the bullet does not move you have enough neck tension, if the bullet moves "normally" this is caused by thin case necks and reducing the expander diameter will solve the problem.

We live in a plus and minus manufacturing world and dies can very is size, but in 47 years of reloading I have very seldom had a bullet grip/neck tension problem. And as I stated above the vast majority of dies have too much neck tension and you feel this when the expander is pulled through the case neck.

Once you have measuring tools neck tension can be more exact but right now pushing on the bullet is good enough.
 
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