300 blackout loading subsonic and...

[TaylorS]

Ran into a little glitch. The olgave on the 200gr Speer hot-cor bullets when seated to prescribed depth of 2.250 is to long to chamber. If I seat it to 2.225 they cycle well and they start to stick at 2.230". So I guess I need to re formulate my powder charge I know seating the bullet deeper will increase pressure and I believe increase velocity. Is there a formula I can use to figure this mathematically? If not anyone have some cheap 200+gr 308 bullets for sale?


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[Dawico]

No formula that I am aware of. Ballistics is a very tricky science.

Your best bet would be a chronograph and hopefully you have a standard length barrel. Then you can work backwards to see what your pressure is doing, well, roughly anyways.

As long as you aren't compressing powder it shouldn't be too bad though.

 

[tmd11111]

Subsonic loads in the .300BO are substantially lower than supersonic chargers so seating the bullet .005 deeper wont make much of a difference. Not sure how much experience you have with the .300bo and subsonic loads but if you don't have a chronograph you will have no idea how fast the bullet is. Another thing is some loads that work with a suppressor will not cycle without one. And lastly barrel length and gas port length will make a difference as well.

 

[TaylorS]

My first run with 300 I figure the chrono will be the sound it makes with a suppressor and that it cycles the next round was just hoping to find q way to get it right without eating up a bunch of lead


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[Deavis]

Quick load can calculate pressure for you if you want it but tmd11111 hit the nail on the head

 

[TaylorS]

Yeah think I'm gonna have to do it the old fashioned way ow well another reason to go shoot . Thanks for the input yall


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[popper]

Load them short so they don't hit the lands. Slam fires aren't safe. Normal BO powders will take 10% compression without problems but you shouldn't be near that for sub

 

[Deavis]

What did loading to the lands have to do with slam fires?

 

[Younggun]

Was wondering the same thing.

 

[tmd11111]

Load them short so they don't hit the lands. Slam fires aren't safe.

Care to explain

 

[Younggun]

Do'H

 

[KiloKilo]

Ran into a little glitch. The olgave on the 200gr Speer hot-cor bullets when seated to prescribed depth of 2.250 is to long to chamber. If I seat it to 2.225 they cycle well and they start to stick at 2.230". So I guess I need to re formulate my powder charge I know seating the bullet deeper will increase pressure and I believe increase velocity. Is there a formula I can use to figure this mathematically? If not anyone have some cheap 200+gr 308 bullets for sale?


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What powder ya using...??
KK

 

[popper]

FP floats in AR - case stops short, firing pin goes forward & bang, even with safety ON. Not good! Case stops due to bad H.S., jamming the lands, neck not trimmed properly, etc. Firing out of battery is never fun. Plus pogo-ing to clear a live round isn't fun either.

 

[Deavis]

Sorry, slam fires are due to incorrect prime seating. How the case stops is irrelevant, your example is not one that I would consider illuminating. Headspace, seating to the lands, trimming, and slam fires are all different issues that you seem to be trying to wrap up in one package.

 

[popper]

Sorry Deavis, slam fire comes from the bolt SLAMMING home & result is 'slam fire' You mixed up the cause and result. The causes I mentioned are correct. A friend's 22 autoloader would go full auto until it jammed or he ran out of ammo. No high primer there. AK had a FP spring to solve the AK problem. I've had two, both HS issues and I use a case gauge. Resized MG 308 brass that stuck near the base & 300BO that jammed the nose. Always keep the barrel pointed in a safe direction when releasing the bolt. I let my GS fire the 40 with just a single round due to his limp wristing - until he got the hang of it. Different cause but same result - unintended bang. Don't mis-inform the noobies.

 

[Deavis]

Ok, let's step back for a second. Your example now is better, your friends 22, which seems to show a malfunctioning gun. In that case Headspace is set by the rim and I know he isn't loading 22 to the lands of it is LR. Your AK example, better since it is centerfire, is also an example of a malfunctioning gun with a bad spring. I'll give you slam fires on a bad gun, which again I reiterate had NOTHING to do with how the cartridge comes to a stop. Lands, shoulder, doesn't matter, which was my main point. The cartridge will stop on something, hopefully it's Headspace datum but it will stop and the pin will follow.

Now, in a gun in good condition, shot by a competent shooter, slam fires are a priming issue. Too soft, too high, they get set off of by the pin since it is not captured in an AR design, for instance.

They make service rifle primers specifically to address that issue when needed. They are able to take the hit from a pin without going off, even when seated above spec. Don't confuse the noobs either, most people assume that we are competent shooters with weapons that function as intended.

 

[Acera]

Never had or heard of an AR slamfire that did not have a mechanical issue with the firing pin being stuck forward, or the hammer falling unintentionally. Fire a round next time at the range, then cycle the action and look at the newly ejected live round, it will have a small dent on the primer from the firing pin hitting it during the normal loading cycle. The floating firing pin on an AR does not have the mass by itself to set off a primer.

I am with Deavis on this one, think you are way off base on that line of thought popper.

 

[Younggun]

Sorry Deavis, slam fire comes from the bolt SLAMMING home & result is 'slam fire' You mixed up the cause and result. The causes I mentioned are correct. A friend's 22 autoloader would go full auto until it jammed or he ran out of ammo. No high primer there. AK had a FP spring to solve the AK problem. I've had two, both HS issues and I use a case gauge. Resized MG 308 brass that stuck near the base & 300BO that jammed the nose. Always keep the barrel pointed in a safe direction when releasing the bolt. I let my GS fire the 40 with just a single round due to his limp wristing - until he got the hang of it. Different cause but same result - unintended bang. Don't mis-inform the noobies.

Did you just say that limp wristing causes slam fires also?

 

[Acera]

Did you just say that limp wristing causes slam fires also?

I think he may be getting bump fire and slam fire confused.

 

[popper]

The floating firing pin on an AR does not have the mass by itself to set off a primer.

Wrong, kinda! Look at the primer dent on an unfired, then a fired. Not much difference. AK didn't come with a spring loaded FP, add on to prevent full auto. Yes, the 22 had a FP problem, the owner finally shot a rabbit 50 ft away with a shotgun cause he couldn't hit it with the 22. No, limp wristing doesn't cause slam fires, but recoil will 'pull' the trigger for you. Even on a mark III. My point is that improper loading/brass prep can cause unintended boom. I don't really care what you want to call it.