Weird stuff going on, Sudden over pressure signs after a few shots

[ShootnMathews]

If that was my rifle/situation I would be sending the next test rounds through a chronograph to see what my velocity is doing.

I'll second that. I can't imagine it's a hot batch of powder as you've repeatedly stated that the pressure increases with each shot.

On a side note. My 6.5-284 did a similar thing a while back. A load I'd been shooting with no pressure signs all at once one day just spiked to high pressures. With 4831sc. Temp stable powder also. I never did figure out what caused it. The load also went from shooting great to not worth a hoot. Charges and seating depth were both right on. I ended up switching to a different bullet and worked up a new load with the same powder and brass. The gun is shooting great again. The only thing I can think of that may have caused it ( and I didn't think to check at the time) is perhaps I got a lot of bullets that were slightly fat on the diameter which increased the pressure.

 

[Corey Schwanz]

Same lot of powder? Varget is notorious for having potentially different burn rates from lot to lot. I'd certainly want to chrono the rounds no matter what to see if its in the norm you expect.

 

[ShootnMathews]

Same lot of powder? Varget is notorious for having potentially different burn rates from lot to lot. I'd certainly want to chrono the rounds no matter what to see if its in the norm you expect.

Really? That's he first I've heard of that. I use varget in several of my guns and usually buy it a pound at a time. Mostly because that's all I can ever find of it. I've had no issues with any changes in it over several years of use. Can after can all from different lots all shoot the same for me with no pressure signs or group changes. Drops out to 800 yards are always right on. I'll keep an eye out for trouble but I've never experienced any with Varget.

 

[AKdan]

I usually buy it by the pound so I am sure it is different lots. The only thing that made me think that it was a possibility was that I had used up one and started another when I loaded these. When the event first initially occurred I was shooting an 18" square plate at 870 yrds. The winds were all over the place, but I was able to hit the plate 6 out of 9 shots. Elevation impacts seemed consistent (vapor trail, impacts on plate) all misses were windage related. I haven't had a chance to inspect the plate, It is sitting way up on a mountain behind the house and its quite the hike to retrieve it and I haven't had time to go get it. Maybe this afternoon. Next week when I have time to load up some more loads I will get out and Chrono a bunch to test powders and charges.

 

[Michael Eichele]

I'll second that. I can't imagine it's a hot batch of powder as you've repeatedly stated that the pressure increases with each shot.

On a side note. My 6.5-284 did a similar thing a while back. A load I'd been shooting with no pressure signs all at once one day just spiked to high pressures. With 4831sc. Temp stable powder also. I never did figure out what caused it. The load also went from shooting great to not worth a hoot. Charges and seating depth were both right on. I ended up switching to a different bullet and worked up a new load with the same powder and brass. The gun is shooting great again. The only thing I can think of that may have caused it ( and I didn't think to check at the time) is perhaps I got a lot of bullets that were slightly fat on the diameter which increased the pressure.

Carbon ring. Carbon ring...Carbon ring......

 

[NW Hunter]

Carbon ring. Carbon ring...Carbon ring......

That's my thought also. Have you remeasured your base to ogive on your rifle?
I found a carbon ring in one of my rifles had shortened my base to ogive measurement.

 

[cowboy]

Carbon ring. Carbon ring...Carbon ring......

Bingo - best keyboard response/guess as of yet - you get the gold star for the day.

 

[ShootnMathews]

Carbon ring. Carbon ring...Carbon ring......

Yes I checked the 'jump' to lands. No change.

And I've been told that the 6.5-284 is notorious for developing a carbon ring so I have used a carbon cleaner since I bought the gun. Giving it a good scrub approx every 100 shots or so. With a clean nylon brush you could feel no change in resistance while gently pushing the brush through.

 

[Michael Eichele]

Yes I checked the 'jump' to lands. No change.

And I've been told that the 6.5-284 is notorious for developing a carbon ring so I have used a carbon cleaner since I bought the gun. Giving it a good scrub approx every 100 shots or so. With a clean nylon brush you could feel no change in resistance while gently pushing the brush through.

What kind of carbon cleaner? It's also important to feel for resistance while gently pulling the brush back towards the breech. Very slow and gentle. If there is any change whatsoever, it needs help. Never underestimate the value of a bore scope. You'll know for sure if you look through a scope.

Most 'carbon cleaners' don't clean the hard fouling in the throat. One of the only real ways to get rid of stubborn carbon in the throat area is JB or Iosso which I normally hate to use but with the 6.5-284 is pretty much mandatory from time to time. Especially in the first 1/2 inch but also the first 6". It would be worth a try. Use sparringly. You don't want to polish your barrel, just lap off a layer of hardend carbon. Try that, I cannot imagine it not settling down to normal.

 

[ShootnMathews]

What kind of carbon cleaner? It's also important to feel for resistance while gently pulling the brush back towards the breech. Very slow and gentle. If there is any change whatsoever, it needs help. Never underestimate the value of a bore scope. You'll know for sure if you look through a scope.

Most 'carbon cleaners' don't clean the hard fouling in the throat. One of the only real ways to get rid of stubborn carbon in the throat area is JB or Iosso which I normally hate to use but with the 6.5-284 is pretty much mandatory from time to time. Especially in the first 1/2 inch but also the first 6". It would be worth a try. Use sparringly. You don't want to polish your barrel, just lap off a layer of hardend carbon. Try that, I cannot imagine it not settling down to normal.

I use boretech. It's supposed to be a copper and carbon cleaner. Works incredible for copper fouling. Bore tech eliminator. I don't have any access to a bore scope. Season will be over next week. I may see if I can find someone to check it out. I'd hate to damage it by using too much of an abrasive compound to scrub it out.

 

[Michael Eichele]

If you do get a chance to look, let us know what you find. Or don't find.

A few thoughts on JB. The original grey compound cuts and polishes very quickly. Too much too often defiantly polishes the lands. I have found over the past few years that the red compound buffs off the really hard carbon just as quickly but takes much more time to polish the steel. I quit using the original altogether because of this. I use it on every cleaning (sparringly) and I have not seen any polishing effects.

After using powder/carbon cleaners and then copper cleaner, I'll run the red JB through 3-6 times depending on how stubborn the carbon is. I'll make a few extra short strokes at the throat. So far so good.

With the gray, you can just about watch the polishing happen. With the red, it's a very slow process.

 

[ShootnMathews]

Thanks for the info. And I apologize to the OP for mildly hijacking his thread.

On a side note. The Boretech Eliminator is the best copper cleaner I have ever seen. I don't like to completely strip the copper out, but I like to remove the heavy deposits. The with the boretech I can do that in less than 5 minutes. I was telling a buddy of mine about it that said his 300 WM stopped grouping well. He said he cleaned copper fouling out for hours and said he got it all. With the boretech the first patch thru came out almost royal blue. 3-4 patches later they were barely showing copper. Next group the gun tightened right back up to 3/8" groups. Sendero 300WM with factory barrel. After his cleaning the groups improved but after the bore tech cleaning it shot like it was new again.