Headspace

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Srt4ever
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Headspace

Post by Srt4ever »

Does subsonic loads have enough pressure to fire form ? when trying to set up my FL die, I don't need much need to bump the shoulder back because it has not bumped forward much. The brass fits into my LE Wilson case gauge just fine, but when measuring with an indicator it falls less then the minimum of 0.005 even before FL resizing it.
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bangbangping
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Re: Headspace

Post by bangbangping »

Depends on the powder and bullet weight. Generally speaking, the faster the powder the higher the pressure. It's possible to exceed SAAMI pressure while remaining subsonic.
BJK
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Re: Headspace

Post by BJK »

Depending on what firearm you're loading for you might want to set your die up for a slight "crush fit" in the chamber for best accuracy. I do that for single shot and bolt action rifles in other calibers since I haven't spent any significant time with .300BLK yet. But I can't imagine having a "loose" cartridge in the chamber would be to advantage with .300BLK. But that's only for actions that possess camming action. If loading for a semi-auto you'd want to make sure the action will close on the round being chambered of course.

For actions that have camming action I think of headspace as being not so important because even if it's out of spec' I can adjust for it. Of course what I just wrote is meaningless and possibly dangerous if using "in spec' " ammo. With ammo in spec' you definitely want headspace to be in spec' also.
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dellet
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Re: Headspace

Post by dellet »

Most sub loads will not properly fore form brass.

If the brass is already too short, you do not want to bump it back at all. It won't grow as fast as a full power load, but it will grow in time.

If your die is set to bump the shoulder back below minimum spec, it is either not set correctly, or a bad die.
300 Blackout, not just for sub-sonics.
Srt4ever
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Re: Headspace

Post by Srt4ever »

My die is set up as the instructions say to. I can’t judge if it’s bumping the shoulder back since the brass when measured in my LE Wilson gauge with indicator gauge is already reading below SAMMI spec of 0.005. Average is 0.007
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dellet
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Re: Headspace

Post by dellet »

Will you’re fired brass fit in your gage?
300 Blackout, not just for sub-sonics.
rlandry6
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Re: Headspace

Post by rlandry6 »

The measurement from a fully fire formed case would be a really good place to start.
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Re: Headspace

Post by rlandry6 »

The measurement from a fully fire formed case would be a really good place to start.
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Re: Headspace

Post by Srt4ever »

The measurement from a fire formed case is still below minimum at 0.007
rlandry6
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Re: Headspace

Post by rlandry6 »

Srt4ever wrote: Mon Jan 11, 2021 4:37 pm The measurement from a fire formed case is still below minimum at 0.007
I'm not sure what that measurement means or how you even got it.
If you take a measurement with the Hornady Comparator, that will give you a measurement from the case head to the datum. That is not headspace. It merely gives you a reference to compare sized cases to so you know how much if any to bump the shoulder. If you want to bump the shoulder .004" in the case of a semi-auto, you would adjust the die to give you a measurement that is .004" shorter than the reference measurement.
BTW, the Wilson gauge will tell you if headspace is within SAAMI specs, but it does not tell if the case body is sized correctly.
At this point, a Sheridan slotted gauge would be a very wise investment.
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