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  #1  
Old 09-29-2010, 11:34 AM
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weird thing at the range today


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I took my Browning 1885 270win to the range today I had gone through about 20 rounds when I shot and the bullet hit about 2" lower on target than the rest. I thought wow I really pulled that one and never realized it. I ejected the case, and tried to load the next round but the round didn't want to go in the chamber. I looked through the bore and I could see what looked like gun powder inside. I turned the rifle muzzle side down and poured out a few grains of powder that didnt ignite. I continued on and it didn't happen again. I guess what I'm asking is, have any of you ever had this happen?
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  #2  
Old 09-29-2010, 01:59 PM
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Yes.

There can be different causes, including powder contamination, but the most common is the powder being used is too slow for the bullet weight. If a light-for-powder-bullet gets a good initial start down the tube, say, from a slightly warm primer, the portion of the powder that starts burning at first, near the primer, can fail to evolve gas fast enough to keep up with the bullet and maintain burning pressure. So instead, pressure drops rapidly and the bullet actually starts slowing down in the tube.

In a bottleneck case, typically about 50% of the powder is pushed down the tube with the bullet by the initial pressure and continues to light up as the pressure and heat reach their peak. But if the bullet gets going too fast for the powder, that peak is not reached before the 50% or so of the powder is spread out in the tube making it hard for one grain to light the next. And if the bullet the muzzle before it gets lit, it never does. Bottom line is a low pressure trip down the tube and much lower than normal muzzle velocity.

There are other problems with using a powder that is slow for the bullet weight, including having the bullet slow so the unburned powder mass rear-ends it further down the tube. That causes the bullet to upset and hammer the barrel radially. This can cause a barrel bulge and, in the worst case, actually blow the end of the barrel off. Texas gunsmith Charlie Sisk had some photos of this which he has been able to replicate on demand with some .338's (I forget if it was the Lapua Mag or some other?).

You can see those powder rear-end collisions with the bullet if you have a strain gauge instrument on your rifle chamber. They cause it to appear there is a secondary spike in pressure after main powder pressure peak, though it is actually just the traveling expansion wave from the radial impact. This is known because, even when the barrel is blown off by an extreme case, the case typically looks like it fired a low pressure load; nicely rounded primer, no brass expansion or sticky bolt events.

RSI has pressure traces showing these pretty clearly if you scroll down to the third from last and the last traces, here. I'd like to slug the barrel of a rifle that's been shooting those loads for a long time. It would be interesting to see if a loose spot has been formed in the bore.

So, bottom line, what is your load?
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Last edited by unclenick; 09-30-2010 at 09:16 AM. Reason: typo fix
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  #3  
Old 09-29-2010, 03:13 PM
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Fully worked winchester brass(except no neck turning)
140grain sierra game king boat tail hollow point
56.7grains H4831sc
CCI large rifle primer
COAL 3.254"(sounds short but hollow point. approx .030" off lands)
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  #4  
Old 09-29-2010, 05:50 PM
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Thats odd I had the very same thing happen last week in my son's 243 I was loading nosler 95gr Ballistic tips over Varget.I've been handloading for over 25 years and this is the only time I've had this happen.only one round but accuracy was bad changed to IMR-4350 much better.I think I may have had a "bad" primer.
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  #5  
Old 09-29-2010, 06:37 PM
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My vote is for a compromised primer...perhaps it had a little resizing lube on it, or something. A 140gr SGK, with that charge of 4831SC and a large rifle primer should not have any issues with ignition. About the only other thought that jumps to mind is if the neck tension was very light and/or the rifle has a lot of freebore, resulting in a situation where there is not enough pressure to sustain the combustion process.
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Old 09-29-2010, 07:21 PM
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I counldn't verify it was powder, one other thing I can think of is maybe it was tumbling media that got stuck in the brass. I am assuming it was powder. It was black and burned but not consumed. I really appreciate all of you guys input on this situation. Maybe it was a compromised primer. I will probably never know for sure. In the past I have not had this situation with this load. Its just weird having one do something totally different when everything in my control is as close as I can get it. Anyone else with input please chime in, I am willing to listen to all theories. thanks in advance

P.S. I really respect Uncle Nicks intuitive answers as with all of his well researched and knowledgeable input, but I truly hope this is not the situation with this load.

Last edited by smokinfz1; 09-29-2010 at 07:26 PM.
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Old 09-30-2010, 04:10 AM
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I hadn't considered the idea of a grain of cleaning media blocking most of the primer flash-hole...I can easily see that causing the problem, as well.
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Old 09-30-2010, 09:15 AM
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In addition to contamination and blocking is the possibility of the primer being high and not igniting normally. I've even seen pictures of burrs on flash holes so bad they diverted the flame to one side (time exposures of primer firing in cut-off case so the flame could be seen). Grip on the bullet could be a factor. Lube in the neck can affect that, as well as can a case that is in need of neck annealing.


Smokinfz1,

I ran your load in QuickLOAD's with its defaults, and the ballistic efficiency of the powder burn was 25.6%. Not awful but not impressive in what is not really an overbore cartridge. It shows the same velocity could be achieved from about 53.2 grains of H4350 and the ballistic efficiency then goes up to 27.4%r. 52.7 grains of Hybrid 100V fills the case about the same as H4831sc and gets the same velocity at the same barrel time in a 24" barrel, and brings the ballistic efficiency up to 29.9%, close to Hatcher's nominal value of around 30%. The difference in pressures among the loads is within a couple thousand psi, averaging around 57,000 psi in the calculator. QuickLOAD's default case capacity is likely smaller than your real case capacity, which is likely to be larger and have lower pressures. In your shoes, Hybrid 100V is what I would be experimenting with, then 4350 if that didn't work out for whatever reason.

I recall a post back four years or so ago with a photo of unburned powder and it was also one of the 4831's, IIRC. Perhaps this powder is more prone to the problem than some others.
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  #9  
Old 09-30-2010, 02:43 PM
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What would a 28" barrel do for it. I have tried 4350 on some 130gr bullets in this rifle but I couldn't get below 1" groups with it. this load is really working well on groupings but I have not run it through a chronograph yet. I'm getting 5/8" groups at 100(actual .629"), shot 200 yard with it but didn't measure it. It was below moa, and at 300 the only group I shot measured 2.5". I should have kept the powder and determined if it was gunpowder, or cleaning media.

There is a reason I am suspecting cleaning media. During trimming of the brass(brass reloaded approx. 10 times)(I trim everytime)there were two pieces that didnt trim any brass off, the first seemed normal as in the cutting head was just against the mouth, the second however the cutting head was a good quarter inch from the mouth. I kept trying to force the lee sizing rod through the case, and it was stuck on what seemed to be nothing, finally after several minutes of frustration some cleaning mediapoured out of the case that had been stuck. I got all the media out of that one but my mind went back to that big pile of brass and that one that didnt' trim. Maybe that was the same piece of brass, I have no way of knowing for sure.
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  #10  
Old 10-01-2010, 03:53 PM
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mostly to unclenick......

Your somewhat close to what is happening during the combustion process but I think just a little off in your explanation. First, the grains of powder probably don't "ignite the next one" as you indicate. The burning is more controlled by temperature and pressure than it is by proximity of the grains.

Second, The pressure would not "impact" the base of the bullet and cause it to "hammer"against the bore. What might happen is detonation occurring in the area of the bullet base which raises the peak pressure in this area. The high pressure would be in the gas and actually lower in the bullet metal itself. The pressure in the bullet is not what blows up a barrel - it's the pressure that exists in the gas.

Third, there is no real "traveling" of the pressure (gas) so as to cause "collisions" with the bullet base. The pressure changes at a constant rate in the bore which is related to the speed of sound. This really means it is rising or falling at a rate consistent with the speed of sound.

In the RSI link you referred to, the people conducting the tests were not certain what was causing the strange peaks they measured. I believe however it is a form of detonation. Not exactly the detonation usually referred to that happens in gasoline combustion in an auto engine. I think it is more related to the burning of powder grains as burning changes from reaction on the surface of the grain to a reaction that takes place through the whole grain. When ever, throughout the mass of powder grains, the temperature and pressure reaches the point it will cause the burning to occur through the entire solid grain in one instant then detonation will occur.
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