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Pressure Signs...Question...

n/an/a Member Posts: 168,427
Let me precursor this with the fact that I'm using brass that is work hardened...it's probably been reloaded at least 6-8 times.

With that being said, I'm using some old .300 Win Mag loads to break in the barrel on my .300 Win Mag A.I. These are probably near max loads for the .300 Win Mag...Not the Ackley. I'm getting some very definitive pressure signs in the brass. The primers are extremely flattened and filled the pockets. I'm also getting a shiny ring with what looks like stress lines in it about 1/4" ahead of the belt. The cases showed pressure signs but there were no other pressure signs (IE: no sticky bolt, etc).

Do you think I'm seeing these signs b/c of excessive pressures, or b/c of old work hardened brass??? As I said above, this brass has most likely been reloaded around 8 times...and these would be under max loads for the .300 Win Mag...not the recommended Weatherby loads for the A.I. cartridge.

Thanks for any feedback I can get![:)]

Comments

  • bpostbpost Member Posts: 30,965 ✭✭✭✭
    edited November -1
    It sure sounds like a head space issue with incipient head separation. All the brass you have fired in that chamber should be scrapped. Flat primers are a real indicator of pressure issues to me. A very flat primer, filling the hole smooth takes a lot of pressure to happen.
  • FWAdditFWAddit Member Posts: 918 ✭✭✭✭
    edited November -1
    One possibility is that your AI chamber has excess headspace for standard-case loads. I can't be sure that's the case, but it sounds likely.

    As I understand the Ackley Improved design, the steeper shoulder is supposed to headspace the same as the regular chamber, but it's possible it is a little too far forward.

    The reason I think headspace might be the problem is, the symptoms are similar to ones in 8mm Mauser of mine. It has such a deep chamber that the firing pin doesn't always reach far enough on factory loads to detonate the primer. If it does, it pushes the case forward, and the discharge first pushes the primer back against the bolt face then jams the whole case back, pinching the primer and flattening it out so it looks like a high-pressure round--except that the primer dent has rounded edges.

    In my rifle I don't get the stretch marks in front of the base that you speak of, but that's because the 8mm is factory-loaded to mild pressures, and the whole case can slip backwards. With your 300 Mag loads, I suspect the case walls are gripping the chamber tightly and pressure is stretching the case to jam the base against against the bolt face. If that is so, your cases are weakened enough to be in danger of case head separation on the next firing. I get that in my .303 British just because the Enfield action is stretchy--but excess headspace has the same effect on cases.

    I no longer fire factory loads in that Mauser, but always handload either using cases specially formed to be a crush fit in that particular chamber or fireform new cases by loading to mild pressures, with the bullet seated far enough out to press against the origin of rifling and hold the cartridge base firmly against the bolt face. Those techniques will work just as well with your .300 AI.
  • perry shooterperry shooter Member Posts: 17,390
    edited November -1
    If you have a bright ring just ahead of the belt I would NEVER load this brass again it is bright in this area because it is stretched and could have head separation the next time you fire. Imho one needs to fire form brass with a fairly quick powder but loaded VERY LIGHT . I know most books state you head space on the belt but to get best accuracy many people head space on the shoulder. If you section one of these cases you will see the inside at this bright ring is very thin . Please don't fire again .We don't want to look for a new MODERATOR Work harden brass is prone to split at the neck NOT near the base. that is why just the neck and maybe the shoulder is annealed .
  • FWAdditFWAddit Member Posts: 918 ✭✭✭✭
    edited November -1
    One possibility is that your AI chamber has excess headspace for standard-case loads. I can't be sure that's the case, but it sounds likely.

    As I understand the Ackley Improved design, the steeper shoulder is supposed to headspace the same as the regular chamber, but it's possible it is a little too far forward.

    The reason I think headspace might be the problem is, the symptoms are similar to ones in 8mm Mauser of mine. It has such a deep chamber that the firing pin doesn't always reach far enough on factory loads to detonate the primer. If it does, it pushes the case forward, and the discharge first pushes the primer back against the bolt face then jams the whole case back, pinching the primer and flattening it out so it looks like a high-pressure round--except that the primer dent has rounded edges.

    In my rifle I don't get the stretch marks in front of the base that you speak of, but that's because the 8mm is factory-loaded to mild pressures, and the whole case can slip backwards. With your 300 Mag loads, I suspect the case walls are gripping the chamber tightly and pressure is stretching the case to jam the base against against the bolt face. If that is so, your cases are weakened enough to be in danger of case head separation on the next firing. I get that in my .303 British just because the Enfield action is stretchy--but excess headspace has the same effect on cases.

    I no longer fire factory loads in that Mauser, but always handload either using cases specially formed to be a crush fit in that particular chamber or (with new cases) loaded to mild pressures, with the bullet seated far enough out to press against the origin of rifling and hold the cartridge base firmly against the bolt face. Those techniques will work just as well with your .300 AI.
  • n/an/a Member Posts: 168,427
    edited November -1
    quote:Originally posted by perry shooter
    If you have a bright ring just ahead of the belt I would NEVER load this brass again it is bright in this area because it is stretched and could have head separation the next time you fire. Imho one needs to fire form brass with a fairly quick powder but loaded VERY LIGHT . I know most books state you head space on the belt but to get best accuracy many people head space on the shoulder. If you section one of these cases you will see the inside at this bright ring is very thin . Please don't fire again .We don't want to look for a new MODERATOR Work harden brass is prone to split at the neck NOT near the base. that is why just the neck and maybe the shoulder is annealed .



    Yep...the necks have several splits in them. Do you guys think it's safe to shoot my last 7 rounds that I already have loaded...again, I am not experiencing a sticky bolt or anything like that.

    Thanks!
  • cwi555cwi555 Member Posts: 1,132 ✭✭✭✭✭
    edited November -1
    I think you need to trash them. Perry Shooter gave you sound advice.

    quote:Originally posted by ECC
    quote:Originally posted by perry shooter
    If you have a bright ring just ahead of the belt I would NEVER load this brass again it is bright in this area because it is stretched and could have head separation the next time you fire. Imho one needs to fire form brass with a fairly quick powder but loaded VERY LIGHT . I know most books state you head space on the belt but to get best accuracy many people head space on the shoulder. If you section one of these cases you will see the inside at this bright ring is very thin . Please don't fire again .We don't want to look for a new MODERATOR Work harden brass is prone to split at the neck NOT near the base. that is why just the neck and maybe the shoulder is annealed .



    Yep...the necks have several splits in them. Do you guys think it's safe to shoot my last 7 rounds that I already have loaded...again, I am not experiencing a sticky bolt or anything like that.

    Thanks!
  • bpostbpost Member Posts: 30,965 ✭✭✭✭
    edited November -1
    You can anneal rifle cases to extend life. It is really quite simple to do once you get the hang of it. I routinely do mine every three firings. Brass failures are now a rare thing.
  • Emmett DunhamEmmett Dunham Member Posts: 1,418 ✭✭✭✭✭
    edited November -1
    I would buy a box of new ammo and give it a try, if you have the same problem its the rifle, if the new ammo comes out clean you have some crap brass. If you are using a full lenght sizing die the ring above the belt could be from sizingl.
  • JustCJustC Member, Moderator Posts: 16,036 ******
    edited November -1
    those shiny rings are a casehead seperation. Fire the rest, and throw them away before you get gasses in the face.
  • chiefrchiefr Member Posts: 10,970 ✭✭✭✭
    edited November -1
    quote:Originally posted by ECC
    Let me precursor this with the fact that I'm using brass that is work hardened...it's probably been reloaded at least 6-8 times.

    With that being said, I'm using some old .300 Win Mag loads to break in the barrel on my .300 Win Mag A.I. These are probably near max loads for the .300 Win Mag...Not the Ackley. I'm getting some very definitive pressure signs in the brass. The primers are extremely flattened and filled the pockets. I'm also getting a shiny ring with what looks like stress lines in it about 1/4" ahead of the belt. The cases showed pressure signs but there were no other pressure signs (IE: no sticky bolt, etc).

    Do you think I'm seeing these signs b/c of excessive pressures, or b/c of old work hardened brass??? As I said above, this brass has most likely been reloaded around 8 times...and these would be under max loads for the .300 Win Mag...not the recommended Weatherby loads for the A.I. cartridge.

    Thanks for any feedback I can get![:)]

    Agree with most. I too reload the 300. I have noticed that sometimes when approaching max loads, extremely flattened primers and bulge/shiny ring in front of the belt. The primers even cratered out around the firing pin. So I ceased firing and pulled the bullets.
    When working up some of my max loads, I have noticed after about 5 reloads, the shiny ring was more pronounced. This lit up my clue light that something aint right. I took a balled scribe (like those used to check bearings) and checked inside the case and could feel a valley that has developed forward of the base web. Thus I deep sixed the brass.
    I can't see inside my brass, but with the balled scribe, I could actually feel my brass was close to separation. I deduced that case stretch is much more with with belted magnums, especially when approaching max loads as frequent trimming is required. I always trim my brass to specs before I reload. I have reloaded my share of belted magnums of different calibers and with a goal of max performance. Afterall, thats what belted magnums are designed for. Problem is (for me anyway) max loads shorten case life. Thus it is a slippery slope between case life and performance. These are some of my experiances anyway. Hope this helps
  • JustCJustC Member, Moderator Posts: 16,036 ******
    edited November -1
    case stretch is the same with any round. The excessive stretch that damages or causes premature failure is due to over-sizing the case. If you only have a FL die, then do a search on "Partial Full Length" sizing. This only sizes the neck and a small portion of the expansion ring near the case head. The shoulders aren't pushed back causing excess headspacing.

    Neck sizing eliminates this all together.

    flattened primers are quite often a sign of excess headspace and not excess pressure.

    A chronograph is really the only way to tell max loads,...when MV reaches a point that you KNOW is too high, you are running too much pressure. Simply looking at cases is only a muddied estimate with other variables at play.

    The AI chambers are VERY hard to read by the eye,..a chrono is the only way to really know max with an Ackley chamber. I have destroyed primer pockets in 1 firing in a 6.5-06AI, with no stiff bolt lift, etc.
  • MobuckMobuck Member Posts: 11,480 ✭✭✭
    edited November -1
    Get some new brass, expand the necks with an 8mm expander, resize until the bolt will close hard, and load with a starting load of the fastest powder listed in your manual or data source. This would be my plan anyway. I use the breakin shots to form the brass saving lots of bore wear.
  • n/an/a Member Posts: 168,427
    edited November -1
    quote:Originally posted by JustC
    case stretch is the same with any round. The excessive stretch that damages or causes premature failure is due to over-sizing the case. If you only have a FL die, then do a search on "Partial Full Length" sizing. This only sizes the neck and a small portion of the expansion ring near the case head. The shoulders aren't pushed back causing excess headspacing.

    Neck sizing eliminates this all together.

    flattened primers are quite often a sign of excess headspace and not excess pressure.

    A chronograph is really the only way to tell max loads,...when MV reaches a point that you KNOW is too high, you are running too much pressure. Simply looking at cases is only a muddied estimate with other variables at play.

    The AI chambers are VERY hard to read by the eye,..a chrono is the only way to really know max with an Ackley chamber. I have destroyed primer pockets in 1 firing in a 6.5-06AI, with no stiff bolt lift, etc.



    Yeah...I need to buy a new Chrono...just tight on the funds right now.
  • RCrosbyRCrosby Member Posts: 3,702 ✭✭✭
    edited November -1
    One last vote for pulling the bullets and not firing those last loads. Whether the problem is headspace, tired brass, or whatever, you're close to edge and I'd rather not be the one pulling the trigger when the head separated and gases went looking for a new way to reach the atmosphere.
  • MIKE WISKEYMIKE WISKEY Member Posts: 9,255 ✭✭✭
    edited November -1
    "Get some new brass, expand the necks with an 8mm expander"......that is what I'd do also. the problem with the belted case is it headspaces on the belt, but the shoulder may be way loose (resulting in head/body separation like excessive headspace). get some new brass, fireform with moderate laods and set your dies to headspace on the shoulder (ignore the belt).
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