Gunsmithing Question on Chamber Pressures

flounderv2

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So heres the deal. I just had the chamber recut/setback from a factory Remington 700 308 chamber to a tighter match grade chamber. With the new chamber being tighter, If I used the same load as before would you expect to see higher, lower or similar chamber pressures. Example. All my previous fireformed loaded cases will not chamber due to being too large for the new chamber. If I were to pull the bullets, resize and reload with the same amount of powder, what would the outcome be. Obviously I will have to work up a new load but I want to see if anyone knew what the new chamber pressures would be from the same loads as before.

Please dont give any opinions as I am only looking for people with evidence to support what they are saying. Thanks in advance for your help.
 

300sniper

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Re: Question on Chamber Pressures

if your chamber is smaller (obviously since your old brass wont fit), the pressure will most likely be higher with the same charge. i would most certainly work my way back up to that charge on a new chamber.
 

bohem

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Re: Question on Chamber Pressures

1) You're correct that you should be treating it as a new rifle since it's a different chamber.

2) The smaller case capacity and smaller chamber with the same amount of powder will boost your chamber pressures. It may be insignificant, it might be HOT it might be dangerous. I can't tell you from the info you have.

3) Correct approach is to back it down and work back up. You can apply it to the same idea as using a thin commercial brass like Winchester and putting the same load in LC brass. I've done that and ended up with the same velocity 2gr lower out of a 30-06.
 

flounderv2

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Re: Question on Chamber Pressures

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">Bohem and 300 got it.


Just to throw an opinion in though, I'd toss the old brass and start with new. </div></div>

No need to trash the brass. Its no different then if you bought once fired brass from someone else, collected range brass and resized it, or just FL sized it every time which allot of people do.
 

K. Johns

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Re: Question on Chamber Pressures

Well what brand? How many times fired?

If I had 3x fired, neck sized only brass for one rifle, I wouldnt FL resize it for more use in a dif rifle. Brass is cheap.

Thats just me. I use Winy brass. If you get 3 firings from winy brass its the cheaper than dirt.

If it was twice fired Lapua, I *might* keep it
 

flounderv2

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Re: Question on Chamber Pressures

Depends on how you treat your brass. I anneal and trim every 2 firings.

I had 15 year old brass I was using at one point and it still shot just fine.

Feel free to send me any brass you have that you dont trust. I'll even pay for the shipping.
 

K. Johns

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Re: Question on Chamber Pressures

I guess Im a bit wasteful with brass. I use Winy brass 3x in my .243win, then toss. I FL size every time, and I trim every time. I've found split necks more than once after only 4 or 5 firings. So I backed off to 3 firings before tossing.
 

flounderv2

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Re: Question on Chamber Pressures

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">I guess Im a bit wasteful with brass. I use Winy brass 3x in my .243win, then toss. I FL size every time, and I trim every time. I've found split necks more than once after only 4 or 5 firings. So I backed off to 3 firings before tossing.
</div></div>

If youre not annealing then I could see how you could have been getting split necks with that number of firings. That makes more sense now.