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Old December 5, 2017, 07:56 PM   #1
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Almost a Fatal Error

With advanced age my eyesight is not what it used to be, causing me to almost have a big problem. I inadvertently shot .270 Weatherby Magnum shells in my .300 Weatherby Magnum. While I didn't realize it at the time, other than not hitting my target of a coyote while Whitetail hunting, how do I determine if I damaged the barrel? I shot the correct caliber after realizing what the mistake I had made and it seemed to still be zeroed in. In looking in the barrell, I cannot see any inconsistency in it, but can someone help me with what I should do to be sure everything is ok to continue to use the rifle.
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Old December 5, 2017, 08:03 PM   #2
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Scary indeed however chance are while nothing catastrophic happened you may have damages the throat or even the rifling as that .270 slug pinballed down the tube. Then again it may have done nothing luckily you didn't get over pressure as most the gasses had plenty of room to escape. Had it been the other way around it could have went kaboom. Shoot a 5 shot group if the accuracy is what it always was you gut lucky.
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Old December 5, 2017, 08:07 PM   #3
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Glad you’re okay

I’m no expert but I wouldn’t think one 277 bullet bouncing down your barrel would hurt it to any appreciable extent.

I believe both these rounds are loaded at the same pressure and as long as your 270 brass held up for that one shot I think you dodged the bullet.
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Old December 5, 2017, 08:14 PM   #4
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No damage done. Bullet is softer that barrel steel. Pressure was lower than normal.
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Old December 5, 2017, 08:15 PM   #5
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No harm done LongTime.
As was said above the 270 bullet will not make a gas seal so the pressure is far lower when you do that then firing a regular round. It just ratteled down the bore. I am just glad you "zigged when you needed to zig" instead of "zagging when you needed to zig".

Better to run a 270 through a 30 cal hole than to try to run 30 through a 270 hole. THAT is where you get HIGH pressures.

Glad you are OK.
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Old December 5, 2017, 09:49 PM   #6
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Thanks guys!

I greatly appreciate the advice. I will see how it groups, as it sounds as if I will most likely not have any issues with it.
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Old December 6, 2017, 10:17 AM   #7
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I have a shooting bud who accidentally fired a 270 Winchester round in a 300 Win Mag M70 claw extractor rifle.

Case head ruptured on the 270 Win cartridge. Entire left side of his face was bloody from brass and gunpowder particles, his left eyelid was closed so he did not loose sight in that eye. He was fortunate that he did not lose his right eye, his right eye was protected from debris by the scope bell. Scope was bent/deformed. The Mc Millian fiberglas stock came out of it without splitting. Floorplate was not blown open. The action was headspaced and found to be OK. The rifle is back in use.

Now the primary differences between his bo bo and yours was cartridge diameter. The case head of a 270 Win is less than that of a belted magnum. Brass case sidewalls will rupture when they stretch too much. In your rifle, the sidewall difference was not enough to burst the case, so, lucky you.

If you had chambered a 338 or 35 belted magnum in your 300 Weatherby, that would have created a bore obstruction and the end result is unpredictable.

I shot about 100 6.5 Swede cartridges down a 7.5 French MAS to fire form the cases. The 6.5 Swede shoots a smaller diameter bullet and the neck is a little longer. All I had to do after firing the rounds was trim the case necks. The rifle was not damaged in any sort of way. Accuracy was horrible, but, I wanted fire formed brass.

Don't worry about your rifle. Pressures were way below that of a 270 Weatherby or a 300 Weatherby because you fired a bullet smaller than the bore.

Now if you had fired a bullet larger than 30 caliber..............
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Old December 6, 2017, 05:37 PM   #8
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I am not advocating this, but with a larger caliber and the same case, I don't think the shell would chamber.

I might play with 30-06 shell into a 270 (dummy round)

I have shot the wrong cartridge in a gun twice (well the first one my brother shot, ergh, as I had loaded up the magazines)

First was a 223 through an AK. I have no idea how that happened, while I need glasses, my eyes are good with them.

I would not have though it would even fire with the setup, it sure did.

It did not sound right and I stopped him, figured it out and egg on my face.

The second was 45 GAP in a 45ACP. And yes the extract provide a nice hold on one of those and the headpiece on the case mouth is not needed to go bang!
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Old December 6, 2017, 05:52 PM   #9
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Old December 6, 2017, 08:41 PM   #10
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This stuff happens more often than many of us realize. I've heard of several times when 308's were fired in 7mm magnums with no apparent damage. 9mm through a 40 S&W pistol isn't uncommon. I've heard 308 through 30-06 is possible. I know they will chamber and I can close the bolt with my rifles. Maybe not all.

In this case I doubt if there is any damage. I'd be concerned about a 7mm barrel after a 308 went through it.

he second was 45 GAP in a 45ACP.
There are lots of folks who fire 40 S&W through 10mm pistols by design. I've run a couple of boxes through mine just to see how well it works and can say very well. I know some guys do it a lot. It isn't something I plan to do, but it is nice to know it would work in an emergency if 10mm ammo were not available and 40 was.
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Old December 7, 2017, 05:16 PM   #11
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Quote: unsafe ammo combinations.
I wished they would separate not advised as opposed to dangerous .

Again I don't begin to advocate but I had 2 or 3 round of the 45GAP fired before I figured it out.

I had not clue at the time that anyone had come out with an almost identical and SHORTER! round in 45.

It seems not to be dangerous as much as non functioning

Dangerous would be one that blew up on your or damaged the barrel.
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Old December 8, 2017, 06:22 PM   #12
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seen it, sort of

I've seen .270 Win fired in a 7mm mag rifle, and the RP brass held.....thankfully. I also picked up a handful of .300 Win mag cases at the local public range that had obviously been fired in a .300 Weatherby rifle.....creating a new cartridge BTW, the .300 Weatherby Shortneck!!!!!
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