Need help with my 257 wby and pressure issues.

[BEEMAN]

He did try factory ammo and brass was toast after one firing.

 

[243winxb]

The weatherby freebore is needed to reduce pressure.

The barrel may also have a tight bore. A little as .001" under, makes a difference.

Reloads- Very slow powders & longer then normal COL may allow the bullets to move to soon, causing a 2nd pressure spike.

 

[jarnold37]

I know no details on the barrel other than it's a 26" 10 twist and the shop I bought it from are the ones who built the rifle for original owner and they said it could be a pacnor barrel but were not sure.
I do have retumbo though I could try it and see what that does.

I have chambered several weatherby cartridges for my own use. In each one I ordered the reamer with no freebore. I never shoot factory loaded cartridges and I compensate for having the bullet at or just off the rifling no more than 10 thousands by reducing the powder a few grains. Still achieve same safe pressure and velocity and accuracy is good compared to a bullet that has a 1/4" jump to the rifling which is a detriment to accuracy

 

[Bob Wright]

Can you drop a new bullet into the spent brass?
Second, you can check the spent brass neck diameter to approximate the chamber neck inside diameter. If it is within .001-.002 inch of loaded ammo, I would be concerned you don't have much clearance in the chambers neck.
It certainly gave me fits before I measured a chamber casting of my "tight neck" reamed chamber and turned all my brass for about .004 clearance. Problem went away.
Your primers are not flattened but you're losing brass you say. So it's possible.

 

[Trm82]

Can you drop a new bullet into the spent brass?
Second, you can check the spent brass neck diameter to approximate the chamber neck inside diameter. If it is within .001-.002 inch of loaded ammo, I would be concerned you don't have much clearance in the chambers neck.
It certainly gave me fits before I measured a chamber casting of my "tight neck" reamed chamber and turned all my brass for about .004 clearance. Problem went away.
Your primers are not flattened but you're losing brass you say. So it's possible.

I will see if I can drop a bullet in the fired brass this evening when I get home.

I tried the factory ammo again yesterday and had very heavy bolt lift on all 3 shots.
It's strange that 70 gr of RL 26 is close to 3700 fps and I dropped right back to 66 gr and I'm still 3620 fps.
Can a barrel actually be that tight ?
I could try to get a warranty replacement barrel on it since I can't even shot factory ammo from the shop that put it together
Or I could just get rid of it and upgrade my 300 ultra with a premium barrel and some other goodies.

 

[Bob Wright]

I will see if I can drop a bullet in the fired brass this evening when I get home.

I tried the factory ammo again yesterday and had very heavy bolt lift on all 3 shots.
It's strange that 70 gr of RL 26 is close to 3700 fps and I dropped right back to 66 gr and I'm still 3620 fps.
Can a barrel actually be that tight ?
I could try to get a warranty replacement barrel on it since I can't even shot factory ammo from the shop that put it together
Or I could just get rid of it and upgrade my 300 ultra with a premium barrel and some other goodies.

I had sporadic pressure issues which resulted in primer pockets going over sized. A gunsmith friend had me check neck clearances and that was the problem with velocity spikes. I run my brass wall thicknesses thinner to accommodate. That may be the fix, cheaper than a new barrel, if that is your issue.

 

[Joe6pack]

Buying someone else's custom is a risk. Whoever built it may have had it chambered for a specific bullet, thus the short throat. Tight necks and Min spec chambers usually get sold once the owner doesn't want to do the needed work on brass prep anymore. Can you get some cerro-safe and cast it? or perhaps the shop can give you the specs on the reamer/finished reamer? Don't quit on it, they are wonderful round/caliber.

 

[Trm82]

I might be onto something with slower powder
I didn't have much time tonight after work to mess around but I threw 6 rounds together just to try while I was shooting other guns and I used IMR 8133. Had no idea where to start but I started with 70 gr and 71 gr. Also I seated deeper but didn't measure I just seated the 100 ttsx just so the last groove was showing. I had no pressure with either charge but I need more powder to bring speed up. If I can get up to 3500-3550 fps with no pressure I will just call that good I guess. Would love to be 3600 + but might not be possible with this barrel.
I will keep adding powder and see where it goes.

70 gr IMR 8133

group from 70 gr. Not sure what to think of the 3179 fps with a group like that. I'd say a bad reading.

this is 71 gr

group from 71 gr