Will very high polished finish on brass cause Excessive stress on bolt face?

[T3-OleMan]

I developed 1 load for my 338WM. I wanted the 225gr MRX to go 3,000fps and I got it. That's over the books and must be a MAX load in my rifle.
Did not have standard signs of excessive pressure..the primers look just like the stock WW 200gr cheap'os I used as brake-in ammo...but, a few cases showed slight marks below the belt. Took 9 of them by the gun store and asked couple of the old timers to give me opinions on how close to the edge I was. They agreed with each other that I was most likely getting too much slide of polished case toward rear of chamber and into the bolt face. Seems logical that when ignition occurs the brass is slamed against the walls of the chamber and then is ramed back against bolt face more than normal cause the brass can't get a grip on the walls of chamber cause it's to slick! Just from a physics stand point it sounds correct. That 0000 steel wool made'em look like gold!

I am not looking to go any higher than that load but would like to feel that I'm not
.00001grs of H4350 away from blowing my self up. The most respected reloader said he would reload them 3 more times and then cut one top to bottom to see how much stretch the lower wall had done at the belt.

Also, the Temp was 90 deg. = worse case scenario.

What say you? Did lack of normal friction of case on chamber wall increase the smacking the bolt face took?

 

[Loner]

Brass is not slippery on steel. Especially when hot and under pressure. Oil, water or
other lubricants would decrease the friction but not a polished surface. Steel wool does have a little
oil in it to prevent rust so wiping them down with a solvent might help.

 

[fj40mojo]

You may want to swab the oil out of your chamber too as long as you are trying to minimize surface slip.

 

[BigSkyGP]

90% Iso-Propyl (rubbing alcohol) is an amazing grease/oil remover! Maybe too dry after you use it.

 

[woods]

With steel wool polishing you are not even close to the Friction Coefficient range that will cause problems.

Rifle Chamber Finish & Friction Effects on Bolt Load and Case Head Thinning Calculations done with LS-DYNA

 

[padd54]

Are these new brass or have they been fire-formed? If they have been fire-formed, did you full length re-size or neck only?

 

[T3-OleMan]

These were New WW fired once in load development and I only do neck sizing, which had been done to true up the dings of bag shipping.
My "C" drive crashed last month and I lost my master Load file but I have the EXL sheets (somewhere) that I printed to use at the range for data collection but, I am going from memory now, and they all occured from 72gns to 73.5grs of ladder testing and with .0005 to .0020 off the land testing. I remember finding no absolut cause....it just showed up at different times.
When I fired one shot I took it out and used the Mag.Glass on it to see if any thing was going on. I know it is a hot load. I will not fire alot of these hot rounds and eat up my throat but I wanted 3k and I got it.

I hunt with "The First Shot" as the long hot load and the ones in the clip are all std mfg length. Like Grandad told me 60 years ago - The first shot is the important one - the others just make him run faster, as I was emptying his new 22 nylon Rem at a rabbit. He was right, at least for me.

 

[royinidaho]

I maybe the odd ball out. Never the less I'll come at this one from the opposite direction.

First thing I'd do is get a very fine crocheting needle or dental pick and reach into the case to see if an indented ring can be detected ahead of the belt.

If such a ring exists the head is just a shot or two from separation. Which is not a good thing. Been there done that and have the soiled tee shirt........

Lastly and pure speculation on my part is that the brass may well be clinging to the chamber wall when ignition occurs. Otherwise there would be no "ring" in side the case.

If there is a 'bulge' ahead of the belt it may be that pressures are simply too high for that specific chamber.r You may wish to have the head space checked.

Either way you may be a bit too close to a surprising personal experience.lightbulb

 

[T3-OleMan]

Roy, you done done it now!!!!!! I have the NEED FOR SPEED!
And, You done made me chicken out and I'll saw one of them puppies top to bottom and SEE if it is stretching enough to snap in a couple more firings (no bulge ahead of belt). If it is, I'll just Load up a box of New Brass and use 1 or 2 each year and throw away after fired-cost only $1.50/2.
That will do me till the time comes when I can Not climb the Mt. Anymore!

I hit a silver dollar at 100 yds and 98% of my ELK shots would be under 250 yrds. So, I'm good to go.
Thanks to you all and I'll do those oil removal tricks and see if it stops the marks below the belt.
And Roy, I respect your opinion enough, to just go to plan "B" and may never get around to finding a ban saw to slice and dice that puppy!
However I still remember the KEYWORDS "Supppppper Glue!!!
Thanks ALL

 

[woods]

Well a "bulge" below the belt can be caused by the size of your chamber in relation to your brass and not cause any problem at all. For instance my 30-06 cases look like this when they come out of my Steyr rifle

this is an expansion of the brass where the case goes from being solid at the head to thinning out for the powder column

factories buy reamers at the largest size and still within SAAMI specs and use them until they are on the smallest size and still within SAAMI. Mine was reamed with a new reamer and has a large chamber. Not a big deal. Easier to have a large chamber and your die will size the pressure ring area than to have a small chamber and the die will not size it like in my 280AI. In that gun the Redding Body Die will not size the case body because the chamber is so tight it doesn't allow the case to expand enough. Or the die is too large. 6 of one 1/2 dozen of the other.

Now a visible ring around the case at that spot or a groove on the inside of the case down there is a problem, not a bulge.

 

[SBruce]

I had case separation once, many years ago. Problem was slightly large chamber, and too much FL sizing. After the smoke cleared, I used the bent paper clip trick to "feel" inside the cases..........sure enough, alot more of them were about to cause me the same headache. They were stretching/thinning right above the web. Some didn't have a ring on the outside, but there was a detectable groove on the inside.

I bought a RCBS precision mic tool, then a neck die. Set up the FL die to just barely size the brass. Threw those cases away and started over............no more problems, avg of 8 fireings on the new cases (all 500 of them) before the barrel started to go south. This was a 220 Swift, which is kinda famous for case stretch.

Don't know if this helps any or not, just offering some points to ponder.

The first shot is the important one - the others just make him run faster

I like that, and nothing is more true than with coyotes! I swear, they have as many gears as we have bullets in the gun!!

 

[T3-OleMan]

Dang Woods, that 06 looks like it has belt envy, and you robbed death one more time! LOL Or, are my old eyes playing tricks on me? Thanks for the link to al. I had forgotten about him – HE has saved more lives than we will ever know by his work in providing the true poop! Love those "amplified deformations"- Ray Charles could see his point with those examples.


SBruce, You are the 2nd person to mention the "bent paper clip trick" and when two people tell me something, I record it on my "B" drive. Thanks.


I had no Idea that "factories buy reamers at the largest size and still within SAAMI specs and use them until they are on the smallest size and still within SAAMI". Had never thought about it cause I would have bet they were EXACT size Specs. Don't think mine is over size at all.


I have learned a lot of VALUABLE info in this post. If any one wants to add something close or tangent to the subject, but don't cause some one might think they are highjacking my thread, bring it on. We need all the knowledge we can get on the deep subjects, and these hidden litttle abscesses can make you use all your cat lives, And that is bad for all of us.

 

[woods]

Dang Woods, that 06 looks like it has belt envy, and you robbed death one more time! LOL Or, are my old eyes playing tricks on me? Thanks for the link to al. I had forgotten about him – HE has saved more lives than we will ever know by his work in providing the true poop! Love those "amplified deformations"- Ray Charles could see his point with those examples.

Hey T3, actually there is nothing wrong with the '06. Those cases have been reloaded over 10 times and still holding primer pockets. My point was that just because you have a bulge does not mean you are overloading or have a pressure situation. It is purely a function of the size of your chamber in relation to the size of the brass.

I wouldn't change a thing about that '06

as it is shooting just fine, bulge and all.

 

[T3-OleMan]

Woods, 10-4 Lock-n-Load. My bad.
Thanks again for the Info. That's what it is all about!
lightbulb[of my 1 load]: Think I will just fire a couple, day before ELK season to ck Alignment / fouling and one during the season and trash them just to be idiot proof- meaning so I can't screw it up!

Safe hunting.