powder blow back??

[jdl420]

Today while at the range I had 3 cartridges come out of the chamber with power markings clear back to the belt and one had powder markings in the extractor groove. This is my japanize 257 WBY Mag that I have been reloading for almost 30 years. I recently purchased 5 brand new unprimed boxes of Weatherby brass and have been trying to find a load with the 110gn AccuBond without much success. Today's load was 62gn of IMR 4831 and my OAL was 3.285" What causes something like this to happen and what should I do?? I'm going to call some gunsmiths in the morning but any ideas would be greatly appreciated as I haven't a clue as to what has gone wrong with my pet rifle

 

[JD338]

jdl420,

If I am not mistaken, Wby brass is made by Norma. This is tough brass!
Your load is on the mild side so I am thinking that you do not have enough pressure to compleatly seal the chamber with the brass case, creating blow by gas.
I would go up 1-2 grains and see if this is the problem. MAX load in the Nosler RG #6 is 65.0grs IMR 4831.

JD338

 

[jdl420]

JD338, How many times can my chamber take these hot gases before causing damage??

 

[hardpan]

Hi There,
JD is right, Norma makes weatherby brass. I load for 3 257 bees. The most fickle likes 69 gr of imr 7828 and a longer COAL. I also use Federal primers. 4831 worked ok for 120 Gr Partions, and for 100 gr BTs. But the 110 AB seems to prefer 7828.

I will look up the other loads for the AB with 4831,
Hardpan

 

[jdl420]

Thanks Hardpan, I'mmore concerned if I damaged the chamber?? I was also looking at 7828 and RL 22as an alternative powders

 

[DrMike]

It is not likely that you damaged the chamber, other than making it somewhat black. Swab it out good and as JD338 recommended, up your load to ensure a complete seal.

 

[FOTIS]

What happened is you fired an underpowered load. The brass did not fully expand and seal the chamber walls, causing the gases to come back and leave soot on the case. No damage done, no worries. Try upping your charge as suggested. Also try 67-70 gr of RL22 with the 110 AB. Start low work up slow.

 

[1Shot]

Like others have said, your load is too light to expand the case to seal the chamber. One thing I have found with NEW cases is they are way short in the shoulder area and the diameter is a bit small also a lot of the time. You don't get very good accuracy with this sloppy a round in the chamber. It pays to fire the case once then part size the case just barely bumping the shoulder so it will chamber good before trying to get accuracy. The first belted case I ever worked with years ago almost drove me crazy trying to get it to shoot accurately. It was a 7mm Rem mag in a Rem 700. I was shooting new Rem. cases. No matter what load or bullet I tried it shot patterns not groups. Then one day I decided to load some once fired cases that I part sized so they just fit the chamber without having a stiff bolt on closing it with the best load I had found so far. To make a long story short. With cases sized this way I could not find a load that would not shoot over 1 1/2 out of that rifle. That first load would put them all in the same hole at 100 yards if I did my part.
In your 257 W I would try some Retumbo powder. I have read great things about it with the 110 AB bullet. Retumbo really made my 264 Win mag shoot.

 

[jdl420]

Thanks everyone for the feedback!! It has been very helpful, however after considering that I have put about a 1000 rounds through this barrel; and by no means have they been hot ie 63gn of IMR4831 behind a 120gn Speer BT running about 3180fps, I maybe running into some throat erosion given that my pet load mentioned above is starting to open up when it used to shoot 1/4 to less than1/2'' groups. I'm going to have a gunsmith scope the bore and throat.

 

[Guest]

Before I went to the trouble of having it scoped, I'd clean the chamber really well with Hoppe's #9 (because you're trying to get the carbon out of there) and then go after the bore with some BoreTech Eliminator or one of the good bore foams - like Break-Free Foaming Bore Cleaner. I bet your barrel is copper-fouled pretty severely and that's where your accuracy has gone.

Oh, and check your crown for burrs.

 

[jdl420]

After thorough cleaning, increasing the charge by 1 and 2 grains and seating the bullet as far out as 3.395 I'm stillgetting powder gases as far back as the ejector groove and the bolt face itself and it seems to be more frequent; it started out about every third round and now is 3 out of 4 rounds. some have said this is not to concerning and don't worry about it. But this is a gun i've shot with confidence for almost 30 years and it has never performed like this. Nor have any of my other rifles shown signs of powder gases past the neck area.

 

[JD338]

jdl420

Did these problems start with the new brass you bought?
What happens with fire formed brass?
Are you having the same problem with older brass?

JD338

 

[1Shot]

Have you reloaded some of the cases that you have already fired once? If it does the same thing with them then it probably is not the cases fault. I would try another powder.

My buddy had a 257 Weatherby that only would shoot well with H-870 which is now not made. Retumbo is about as close to filling it's notch. Retumbo really makes my 264 Win Mag perform.

 

[jdl420]

Yes they did start with the new brass but I have since used the fire formed brass and the same problem. I'm switching powders to 7828 starting with 68-70.5 in .5 increments.

 

[jdl420]

So with old cartridges(now down to 24 rounds left)no blow back and decent group under .5''(.386'') and this was with 2 necks splitting. The box of 2nd fired brass with 64gr ofimr 4831 continued to blow powder gases back I stopped after 3 rounds and began shooting the imr7828 starting at 68gr-70.5gr. None of these rounds had any blow back and the groups (3 shots) averaged less than an inch with each group having one round acting like a flyer but the other 2 rounds getting in there at a range of .04, .235, .469, .489 and .567'' I'll settle for 70.5grs and fiddle with the seating depth as these were all fired from 3.340''. I quess the old girl just didn't like new brass and imr 4831. I think I will anneal these casing after I run them through the tumbler

 

[caribouhunter]

i have the same thing happen on the neck of my 300 rum cases, they're all black after firing. i noticed that the bolt is harder to close when loading on these than say factory ammo. something wrong with my case prep?

 

[JD338]

i have the same thing happen on the neck of my 300 rum cases, they're all black after firing. i noticed that the bolt is harder to close when loading on these than say factory ammo. something wrong with my case prep?

Try bumping the shoulder.

JD338