case length 6mmar T40 IMP

[semo97]

Need some case lengths at different stages.
1st time sizing the 6.5 lapua down to 6mm preparing for fire forming?
Case length after fire forming?
Case length after resizing the fire formed case?
I know not all chambers will be the same but need some figures to see if I am in the ball park.
Thanks
Jr.

 

[rminut]

the case length doesn't change. it's the same 1.515 trim length and 1.525 max. look on his website.

 

[fcorbin]

Were at on Roberts website? Thanks Frank

 

[rminut]

http://www.6mmar.com/6mm_AR_Loading_Info.html

if there was a difference between the 6AR and 6ART40, Robert would have listed it. There is only length for all three variations.

 

[semo97]

the case length doesn't change. it's the same 1.515 trim length and 1.525 max. look on his website.

Why is the modified case you use in the oal gauge at 1.503?

 

[rminut]

ask Robert directly.

 

[c.k.93]

Semo97,
I have a turbo 40 and I just measured 25 of the AA brass that have been fired four times. They all have been re-sized. 23 of the 25 measured 1.503 to 1.505. One measured 1.501 and one at 1.500.

I looked on Robert's website and didn't find a trim length for the turbo 40, either. I don't believe the max and trim length for the turbo 40 are 1.525 and 1.515.

If you contact Robert, could you post what he recommends? Or ask him to update his website with the max and trim lengths.

c.k

 

[semo97]

C.K. 93
Thank you for the lengths. Sizing the first time from 6.5 to 6mm I get 1.518 with the false shoulder. Robert said that was about right. My Fire formed cases are at 1.514 to 1.520 the false shoulder is gone the case body is the same length of the three fire formed cases Robert sent me but the necks are longer. The three cases from Robert are 1.501,1.502,1.503. Did you trim your fire formed cases down to your lengths or did they fire form that way or a little longer before you resized? I have had email contact with him but the last one did not go well so there is no more comunications wont, say any more. My fire formed cases look just like the 6mm ar turbo case.

Jr.

 

[c.k.93]

Semo97,
No these 25 pieces were not trimmed ever. The brass were re sized and their shoulders push back .004 to .005. The first one hundred pieces of brass were all over the place with respect to overall length. They were used for load development and some of the loads were "too hot" for the brass. The hot loads stretched the brass more. These 25 were not abused, so after the fourth firing the brass settled down and measured around that 1.503 to 1.505 mark.

My method of fire-forming takes three firings to obtain sharp shoulders. I decided after the fourth firing is when I would trim everything to the same length. Since, I decided to trim after the fourth firing I didn't keep track of the measurements. Don't quote me, but if I recall right the cases started at 1.516, after the first fire they shrunk to 1.508, second firing they shrunk to 1.506, and the third firing the brass settled in at 1.504, and the same length for the fourth firing. The middle two lengths are a guess, but I'm sure on the ending length.

Couple of things to consider: I wouldn't trim until the brass settles down (3 or 4 firings). Google "Sinclair chamber length gage" and check out this tool. I used one of this on my 7mm reg mag bolt action, but I'm not sure it would work on a semi-auto.

Hope this helps
c.k.

 

[semo97]

CK
Thank you that helps a lot. Now I know what to expect and this advice will help several others that are reloading this for the first time.

Jr

 

[spclark]

) Google "Sinclair chamber length gage" and check out this tool. I used one of this on my 7mm reg mag bolt action, but I'm not sure it would work on a semi-auto.

Yes, Sinclair's chamber length gauge products work very nicely with semi-autos. In fact I highly recommend anyone doing this kind of case forming operation purchase & use one to determine the exact length case their chamber will accommodate safely. Usual practice once that dimension is known is to trim brass to at least 0.010" less, 0.015" - 0.020" is even better & won't affect accuracy the least bit.

With AR's it's a good idea when using this tool to perform the chamber-measuring operation after removing the bolt's ejector and spring. You need a specific tool to do this (AR bolt disassembly jig & 1/16" pin drift) with ease. Leave the extractor in otherwise getting the modified (neck-shortened) case out's a real PITA without disturbing the gauge plug.

This way you know for certain what the maximum safe case length is for your rifle & can trim according to your needs.

 

[c.k.93]

spclark,
Thanks for the confirmation and proper way to use the gage with a semi-auto. I give your method a try when it cools down this fall and I start shooting more.

Thanks for the advice
c.k.