Dasher case length delimma !

[rsbhunter]

Ok, I know this has been beat to death, but..... If the max case length is 1.560 ( cartridge dimensions, Accurate Shooter site) and Alpha brass runs, 1.539-1.541 new, 1.545 fired 3 times, and Lapua measures 1.544-1.545 fire formed and sized , .002 bump. Does the cartridge ever grow in length to be close to the end of chamber so you don't get carbon build up/carbon ring? And if I trim to shortest case oal, im even further back from the chamber "end'"? Maybe over thinking it, but with the Dasher being a top accuracy cartridge, I would think you would want the longest neck and have maybe .005 trim length , or distance to chamber length. Thanks for straightening me out, rsbhunter

 

[rsbhunter]

pics of case mouth in chamber, shiny chamfer is Lapua brass, dull is Alpha multi fired...rsbhunter

 

[G Liles]

A lot of room for that damn carbon ring!!

 

[rsbhunter]

I'm not a top notch shooter in national competition, I still like to make sure I'm not making simple mistakes.....I do watch for carbon build up. This is why I don't understand why (other than the Dasher isn't a SAMMI cartridge) the cases aren't at 1.550 or closer to "most" chamber dimensions??? So, do I just shoot the cases at mixed lengths til they either wear out, or hopefully grow to a better length? rsbhunter

 

[6bra1k]

buy the correct tool from sinclair and measure YOUR chamber neck length, 1.560 is a SPEC and may have little to do with the reamer used to cut your chamber. you are mixing apples and oranges. do what's right for YOUR CHAMBER.
the pics seem to indicate the wrong reamer for your brass. lots of room to grow a carbon ring.....

 

[60723]

I have Dasher brass shot 20 times that never reached 1.550. They were trimmed when new for neck turning. I just keep the carbon ring down as much as possible. I now “trim” every firing with a Giraud. Only issue now are donuts.

 

[rsbhunter]

The reamer is a JGS with "standard" specs other than a .142 freebore. The gap between the case mouth and chamber is because the brass varies between 1.542-1.548. With .018-.012 , alot of gap!!! rsbhunter

 

[expiper]

if using Lapua 6mmBR brass ---inch 555 is perfect

 

[rsbhunter]

I am using Lapua 6br using the false shoulder forming method. The base to shoulder datum measurement was exactly the same as the Alpha 3 time fired, so they are forming perfectly. If I could get 1.555, I'd be perfectly happy....we'll see what happens after a couple firings... rsbhunter

 

[LRPV]

Shoot your rifle, clean your barrel and your chamber and don’t worry about it. You obviously have a borescope so just check every now and then. Brass growth with a Dasher is going to depend a lot on how much your die oversizes the diameter of the case. Overall case length won’t keep you out of the winners circle.

 

[rsbhunter]

True, but, being OCD , I like to have all the numbers the same....but like I said, I'll shoot it and see...rsbhunter

 

[LRPV]

True, but, being OCD , I like to have all the numbers the same....but like I said, I'll shoot it and see...rsbhunter

I feel your pain but unless they’re TOO long, it’s not an issue. Trim them to the short one if it makes you feel better. Just keep the chamber clean and you won’t have an issue. Good luck.

 

[Mulligan]

Shoot your rifle, clean your barrel and your chamber and don’t worry about it. You obviously have a borescope so just check every now and then. Brass growth with a Dasher is going to depend a lot on how much your die oversizes the diameter of the case. Overall case length won’t keep you out of the winners circle.

This^^^^^^^^^^^
Jason is 100% correct
CW

 

[rsbhunter]

True, its shooting good, so it's something ill keep an eye on...rsbhunter

 

[MTlager]

I fire formed 100 Lapua cases last month with cow , 14 grains bullseye and false shoulder and they were 1.555 to 1.560. After first bullet firing they grew some and then I trimmed them. My chambers all run 1.565 for oal on the brass.

 

[rsbhunter]

It amazes me how one method of fire forming can result in such different measurements.... Maybe next time I'll try the cow method....will be firing 50 rounds fire forming this next Saturday at a match, we'll see how they come out....rsbhunter

 

[Dave M.]

It amazes me how one method of fire forming can result in such different measurements.... Maybe next time I'll try the cow method....will be firing 50 rounds fire forming this next Saturday at a match, we'll see how they come out....rsbhunter

Also makes a huge difference how you fire form. I like to put a light oil lube on the outside of all cases I’m forming. This lets them “flow” so to speak.