Gas check shank lengths

LBD
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Gas check shank lengths

Postby LBD » Tue Aug 20, 2013 10:52 am

When selecting a gas check shank length, does the length parameter refer only to the cylindrical portion of the shank, or does it also include the bevel joining the cylinder to the trailing band?

Here's a more theoretical gas check shank issue:

What are the pros and cons of stepped gas check shanks with regard to .35 caliber bullet designs? Is the stepped shank less likely to retain a crimp-on type .35 caliber gas check in flight than a straight shank would?

LBD

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mtngun
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Re: Gas check shank lengths

Postby mtngun » Tue Aug 20, 2013 12:30 pm

The shank length includes the bevel.

What are the pros and cons of stepped gas check shanks with regard to .35 caliber bullet designs? Is the stepped shank less likely to retain a crimp-on type .35 caliber gas check in flight than a straight shank would?]

The stepped check helps the check hang on at the reloading bench.

Upon firing, the shank obturates (unless you are shooting a wimpy load) so there will be no difference between the different types of check shanks after obturation.

I've never experienced a problem with gas checks coming off in flight.

LBD
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Joined: Fri Aug 16, 2013 2:10 pm

Re: Gas check shank lengths

Postby LBD » Tue Aug 20, 2013 2:37 pm

Thanks for your quick reply.

The shank length includes the bevel.


I'm sorry, I should have asked you how long the bevel is just ahead of a .3425" diameter straight shank... is it < .010" (I'm referring to a bullet that has an As-Cast diameter of .361")?

Upon firing, the shank obturates (unless you are shooting a wimpy load) so there will be no difference between the different types of check shanks after obturation.


Other than the amount of lube held by the shank.

I've never experienced a problem with gas checks coming off in flight.


Wanna see pictures of my dented chronograph? :D

Thanks again,
LBD

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mtngun
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Re: Gas check shank lengths

Postby mtngun » Tue Aug 20, 2013 3:41 pm

LBD wrote: how long the bevel is just ahead of a .3425" diameter straight shank... is it < .010" (I'm referring to a bullet that has an As-Cast diameter of .361")?
That's calculated by the CNC software to produce the specified groove angle consistent with the groove depth of the particular bullet. Assuming a 45 degree groove angle, the length of the bevel should be equal to depth of the groove. In your case, (0.361" - 0.327") / 2 = 0.017". However, it is not a controlled dimension.

Wanna see pictures of my dented chronograph? :D
I was gonna say, if your gas checks do come off in flight, and if you're shooting over a chronograph as I usually do, then the errant gas checks will occasionally ding the chrongraph.

I can only guess that people who are having gas checks fall off in flight are shooting mild loads that don't obturate much ?

Also, cracks can develop in the shank if you cast waaaay too hot with antimonial alloys, causing the entire shank to part company with the bullet when fired..

A customer once complained that his checks were coming off in flight. I asked him to search the ground downrange and try to recover some of the checks. He did and lo and behold short chunks of the shanks were still attached to the check. :o The problem went away after he cast a little cooler.

I've yet to ding the chrono with normal gas checks, but I've had it happen with upside down gas checks, and with soft plastic checks.


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