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unexplained pressure

 
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  #1  
Old 05-09-2013, 09:38 PM
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Join Date: Mar 2012
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unexplained pressure

I have a 6.5-284 and have been shooting sierra game kings with 42.5 grains of H4350 at a depth of 3.020..I have shot over 150 rounds at this recipe and never had a problem but at the range tonight i was doing a ladder test in seating depths. 3 shots at each of 3.010, 3.020 and 3.030. The 3.020 shot the best but my third round had an excessive amount of pressure. Enough to stick the bolt and enlarge the primer pocket. All the manuals i have seen say that 42.0 is starting and 45.5 is max so im way under max. The 3.020 is my pet load and never caused a problem does any one have any idea on what could of happened.
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Old 05-10-2013, 09:37 AM
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Location: The rifle range, or archery range or behind the computer in Alaska
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Re: unexplained pressure

Quote:
Originally Posted by deaddog View Post
I have a 6.5-284 and have been shooting sierra game kings with 42.5 grains of H4350 at a depth of 3.020..I have shot over 150 rounds at this recipe and never had a problem but at the range tonight i was doing a ladder test in seating depths. 3 shots at each of 3.010, 3.020 and 3.030. The 3.020 shot the best but my third round had an excessive amount of pressure. Enough to stick the bolt and enlarge the primer pocket. All the manuals i have seen say that 42.0 is starting and 45.5 is max so im way under max. The 3.020 is my pet load and never caused a problem does any one have any idea on what could of happened.
What's the velocity?
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Old 05-10-2013, 10:19 AM
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Join Date: Jun 2012
Location: Bismarck, ND
Posts: 22
Re: unexplained pressure

Are you getting all the carbon out when your cleaning. Carbon ring could explain spike in pressures. Also how many times has your brass been fired? is it possible that piece of brass reached its end of life? some things to look at if you haven't already.

Good Luck

Mike
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Old 05-10-2013, 09:50 PM
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Join Date: Mar 2012
Posts: 11
Re: unexplained pressure

I havent shot it threw a chrony so im not sure what the velocity is for sure but i would guess between 2600 and 2700. Its a mild load. I had just cleaned the gun before the trip to the range and i use hoppes #9 copper fouling and run patches threw untill there is absolutely not residue. also Im pretty anal about my brass so i keep a track to make sure every brass has had the same amount of rounds threw it and they have had 5. The brass is nosler custom grade
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  #5  
Old 05-11-2013, 10:31 AM
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Join Date: Mar 2004
Location: Las Vegas, NV
Posts: 551
Re: unexplained pressure

+1 on looking for a carbon ring. Regular cleaning cannot remove it. One way to tell (assuming you do not have a bore scope) is to pay close attention to when you run a patch (or brush) down your barrel. There will be resistance as you pass the ring, then much smoother progress down the bore after you get past it. I developed one in a .308 and a 7WSM. After doing so, regular loads were showing up with overpressure.

Here are a few articles about the carbon ring and its removal.

Carbon Ring

Carbon ring ?
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  #6  
Old 05-11-2013, 12:44 PM
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Location: Leominster mass, originally Salisbury Maryland
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Re: unexplained pressure

Quote:
Originally Posted by JeffVN View Post
+1 on looking for a carbon ring. Regular cleaning cannot remove it. One way to tell (assuming you do not have a bore scope) is to pay close attention to when you run a patch (or brush) down your barrel. There will be resistance as you pass the ring, then much smoother progress down the bore after you get past it. I developed one in a .308 and a 7WSM. After doing so, regular loads were showing up with overpressure.

Here are a few articles about the carbon ring and its removal.

Carbon Ring

Carbon ring ?
Jeff, very interesting articles on the carbon removal methods. The GM top engine cleaner is incredible. I have been using it for years, and it really does work.
Another thing that works great is automatic transmission fluid. It works best when left in over nite. ATF fluid is very high in detergents, that attack carbon.
I have found that when using a lot of RL22' RL19, you have to keep an eye on the carbon. It builds up quick too. You get that roller coaster feel when you attempt to clean, and it is usually tighter at the breech end, then it smoothes out. Great thread!
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  #7  
Old 05-12-2013, 06:44 PM
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Location: Grantsville Utah
Posts: 3,473
Re: unexplained pressure

I'll give an amen to checking for a carbon ring. I have used a cloth soaked in Kroil and left it in the chamber for two or three days. I then take a stiff wire brush and rotate it in the neck/throat area. Check and see what comes out and repeat if necessary. Usually, if you have a carbon ring, your accuracy suddenly goes south as well as pressure spikes.......Rich
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