pressure signs

[pills]

Shooting a new rifle that only has about 40 rounds through it so far. Cooper in 6.5x284. Loaded rounds of reloader 22 at 50.5g-51.5 grains using a 140g accubond. these are not near max according to the data I looked at. Rounds were seated .005 off the lands. I fired 3 rounds at 50.5g and 3 rounds at 51g... case heads showed bright spots and has moderately stiff bolt pressure on opening chamber. after the first 6 these signs both disappeared. cases looked fine and bolt was easy. I eventually worked up and shot the 51.5g rounds with no pressure signs at all. also the groups got better as the day went on and the last 2 groups were under .500. only fired 7 groups of 3 today total so the gun now has about 60 through it.

I have never experienced this before, is this a sign of the rifle breaking in? any other ideas?

 

[bheadboy]

it is possible there was lub in the bbl, chamber, action area from the mfg, unless yu cleaned it, that can cause a lot of pressure.

Bob

 

[Raythemanroe]

Should of cleaned it first! not saying u didn't...I like to clean my barrels before firing them the first time! I couldn't imagine sending a bullet down a barrel with foreign material in there..

 

[pills]

It had been cleaned then had 40 rounds through it and cleaned again before today. Also ran a dry patch through today before shooting

 

[Raythemanroe]

maybe soft brass!

 

[pills]

Lapua

 

[Raythemanroe]

I have seen the same thing with Nosler brass in my .243! I know powder can very, but it would have to be something causing high pressure right?

 

[gotcha]

Establishing distance to lands can be very ticklish. With only .005" OTL clearance, slight variations in ogive shape could raise pressures significantly. After all, .005" is roughly the thickness of writing paper. Not much room for bullet shape variation. Did you measure ogive to base on all rounds fired?

 

[mikecr]

is this a sign of the rifle breaking in? any other ideas?

Sounds like a sign of load developing with NEW brass.

 

[pills]

I didn't measure base to ogive but did measure oal to ogive on most rounds. I guess I will shorten them slightly and keep checking for pressure signs.

 

[bigedp51]

It had been cleaned then had 40 rounds through it and cleaned again before today. Also ran a dry patch through today before shooting

What did you use to clean your barrel and was it 100% free of ANY residual bore cleaners.

Were the cases 100% free of all resizing lube?

If the cases did not grip the chamber walls for any reason your bolt thrust would increase and cause the stiff bolt pressure on opening.

Some people in forums don't like when I post this information in forums and think it doesn't apply to them.

 

[gotcha]

Sage advice! No complaints from me.

 

[pills]

I have no problem with any advice or tips, I'm always learning. Cases were all wiped down after sizing but it is possible there could have been some residual I guess. But it only happened on the first 6 and not after leading me to believe something in the rifle burned off....I did dry patch before shooting but possible residual remained in the rifle.

 

[TominSWNY]

Cleaning fluid or oil in the chamber will do just what you are experiencing.

 

[XTR]

Two thoughts

One is bolt thrust from lube still in the chamber or on the cases. Pretty amazing that even water will cause that. I saw some cases that you'd swear were hugely over loaded at a match a month or two ago where a relay got rained on.

-.005 is no mans land. My experience is shoot them in or out. Either +0.010 or -0.010 or more but never in between. Seating at -0.005 you there are a couple of potential issues. One is that you get a bullet that is slightly longer and end up in the lands, the other is that with only 0.005 jump the bullets momentum going into the lands when it starts may vary enough that hitting the lands effects pressure differently bullet to bullet and hurts accuracy accuracy, by the time it's moved 0.010 it's got enough pressure behind it that it's consistently on it's way. (It's my theory and I'm sticking with it)

 

[bigedp51]

I routinely have oil in my chamber - I put it on my cases on purpose (it drives Bigedp51 crazy - he is waiting for me to blow up ).

I have no problems with it, and I have no head separations - EVER.

I have done it for more than 35 years.

I don't care if you put whale snot on your cases CatShooter , what you and many others don't seem to understand is that some brain dead kid reads what you say here and takes it as gospel and then spreads it to every forum on earth. There are rifles that are severely effected by bolt thrust and I have seen them.

XTR just stated above he saw it happen with just a wet chamber, on top of this NATO proof testing requires one dry proof test cartridge to proof the barrel and one oiled proof test cartridge to proof check the bolt and receiver. If the headspace increases over .002 to .003 the rifle fails proof testing. Oiling the proof cartridge doubles the bolt thrust and simulates combat conditions like firing a rifle in the rain.

The No.4 Enfield rifle was made of modern steels and at the end of its life chambered in 7.62 NATO. Below are the standard bolt head wear over turn limits.



Below is a No.4 .303 Enfield damaged by excessive bolt thrust.



Even the U.S. Military tells you to not lube your ammo.



And even civilians who make the M1A tell you to not lube your ammo.







I stopped lubing cases over 40 years ago after damaging a rifle, and started doing my homework, I never lube my cases and I don't have case head separations.

The message above was brought to you by the "Society for the Prevention of Cruelty to Firearms".

 

[pills]

Thanks for all the help guys. I will try both making sure everything is dry and backing down to .010 off the lands. This is a hunting rifle so It will be used in a variety of different temps and conditions so I would rather not seat with a jam.

 

[Raythemanroe]

If you work up your loads it shouldn't matter!

 

[BoydAllen]

CatShooter,
If you had given the video your full attention, you would have understood that Jack was speaking of his practice when fire forming 6PPC cases from .220 Russian, in which case the disparity between the capacity of the .220 Russian case and the 6PPC chamber places a serious limit on the peak pressure that is attainable with normal 6PPC powders and bullets. You may be assured that he does not do this on his full pressure 6PPC loads. To my knowledge, no one does.

For all posters, I think that it is important that we keep in mind that shooter/reloaders of all levels of experience read these forums, and that for some strange reason, seem to be overly impressed with internet forums as a source of information.

To the readers, don't ever take a load from a post without consulting a reloading manual to see if it is safe, or some lone posters word for something that involves safety. Use multiple sources, and try to include some that are actually in print, and have therefore seen the attention of an editor, and possibly legal department.
Boyd

 

[Raythemanroe]

That is good advise Mr. BoydAllen, The difference between boom and bang!