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Old September 26, 2011, 09:38 AM   #1
Clark
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Big screw up.. 270 ammo in 7mmRemMag

The 270 ammo will fit in a 7mmRemMag chamber, and seems to headpsace on the bullet [the bullet is what resists the cartridge moving from the forward push of the firing pin].

I have made this mistake twice.
Chambering a number of 7mmRemMag rifles and mixing them and 270 rifles on the same bench, and reloading at the same time, got confusing more than once.

The first time was a 10kpsi load, and I did not learn my lesson.
The second time was a 70kpsi load and the case ruptured.

I would like to say I will never fall for this again, but I am about to put a number of 270s and 7mmRM rifles in my vehicle and drive 1000 miles.
I probably WON'T make that mistake again, as I always seem on hunting trips to find new mistakes to make, like getting stuck on a mountain in the dark, and falling in a hole.
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Old September 26, 2011, 09:48 AM   #2
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Thank God you are all right.

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Old September 26, 2011, 10:17 AM   #3
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Clark,

You're not the first one to try a virtual caliber conversion (one lacking only the physical changes needed). Though I can't recall seeing a quite such a dramatically split case result. I hope the escaping gas didn't get to do any other damage.

.308's fired in .30-06's is the more common variant I've seen both in other peoples pictures on the web, and even witnessed opne myself. It fireforms the .308 to a wildcat I call the .308 Mob Enforcer; the world's only cartridge with no neck.

When I'm coding test loads I use a Sharpie to put rings on the bullets half way up the ogive. If you did that just to the .270's or just to the 7*mm's, each time you pulled a round out, you'd get a reminder to double-check it's the right size.

Stay safe.
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Last edited by Unclenick; September 27, 2011 at 11:35 PM.
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Old September 26, 2011, 10:43 AM   #4
Jim Watson
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That seems a common mistake.
Although I fail to see how a .277" bullet is going to get any purchase to "headspace" in a .284" barrel.
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Old September 26, 2011, 12:07 PM   #5
Jimro
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The bullet doesn't headspace, the cartridge shoulder headspaces. If the shoulder for the 270 win has any purchase at all against the 7mm chamber face this can result. Conversely the 270 would have been swallowed in a 7mm STW chamber or 300 H&H chamber.

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Old September 26, 2011, 01:14 PM   #6
Slamfire
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A guy at the Gun Club stuck the wrong cartridge in his M70 classic, and I think it was the exact cartridge combination you are talking about. He had a 270 Win rolling on the table and inserted it, and fired it in a controlled feed M70 in 7mm Rem Mag.

The case head blew.

I think the action was useable though I am sure parts came off. It made a big impression to the shooter, he wanted everyone to know what happened so they would not make the same error.
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Old September 26, 2011, 03:31 PM   #7
HiBC
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Extractor will often hold the cartridge enough to get it lit.
I think,on account of I could probably remember a time or maybe even two when I committed an indiscretion,I'll end with a "Glad nobody got hurt".
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Old September 26, 2011, 04:43 PM   #8
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Accidents happen, hope i am not at the next bench when it does.
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Old September 26, 2011, 05:49 PM   #9
Doodlebugger45
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My business partner did the exact same thing as Clark did a number of years ago. This guy doesn't handload, he doesn't even shoot very much, but he's a sensible guy. For many yearas, he only owned a .270 for hunting. Then he finally went out and bought a 7mm mag. He bought about 3 boxes of ammo for the new rifle, shot about 40 rounds through it and felt good to go. Elk season came around and his first day he got ready to go early in the morning while it was still dark. He put his brand new ammo into his hunting coat and then set out to find his spot. Arriving at a likely spot, he then proceeded to load his new miracle rifle.

Except... he forgot that in the OTHER pocket of his old hunting coat were about 5 rounds of .270 ammo, which he inadvertantely loaded into the 7 mm mag.

Daylight came around and he saw a big old bull just 50 yards away. He said the sound was extremely loud. He felt something wet on his face and it was blood. The elk calmly walked away.

I'm not sure what caused the blood on his face. Nothing serious though. I guess it was gas escaping through the vent due to the ruptured case.

Later that day he tried the proper ammo and the rifle still functioned fine, so he shot an elk the next day. I guess he was rather lucky and there were no serious consequences, but he pays a lot more attention to those things these days.
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Old September 26, 2011, 07:25 PM   #10
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Quote:
That seems a common mistake.

No resizing 30-06 cases in 270 dies is more common for me.

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Old September 27, 2011, 12:59 PM   #11
Doodlebugger45
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Yep.

While I haven't actually put the wrong case/cartridge into my rifle, I did have a screw up involving .277 and .284 projectiles. One time I bought 2 new boxes of Combined Technology Ballistic Silvertip bullets from my neighborhood bullet pusher. They were both 150 gr bullets, but one box was .277 bullets for my .270 WSM and the other was 7 mm bullets for my 7 mm mag. They looked identical in appearance.

So I researched and cyphered and came up with the perfect load development I wanted to try for the .270 WSM. I powdered the cases and had seated about 8 bullets. Then I got curious as to the tolerances that Combined Technology/Nosler had for those bullets. I weighed a couple of them and sure enough, they were spot on 150.0 gr. Very good. But then for some reason, I actually measured one with a caliper to see the diameter and did a double take. It measured precisely .284". I had mistakenly set both boxes of bullets on the bench and had opened the wrong one. Yeah, I had noticed that the bullets seated maybe slightly harder than normal, but it didn't ring an alarm to me because they were boattail bullets and my cases were chamfered extensively so they slid in fairly well.

I often wonder what would have happened if I had tried to fire that .284" bullet down a .277" bore. Maybe nothing catastrophic but I'm glad I didn't find out.

Oh yeah, and that's when I found out that my handy dandy kinetic bullet puller will NOT work for WSM cases. They are too fat to fit into it. I pulled those 8 bullets using a pair of pliers on the top of the press. The good news is that even using such a crude pulling technique, which left some marks on the ogive, when I later loaded them into a proper 7 mm case, they shot just as well as the unmarred bullets.
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Old September 27, 2011, 04:45 PM   #12
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I always bought .280's and went out west with a buddy that shot .270, Both of our guns were Remingtons with the old steel mags.One year when I was getting ready to go out west I climbed up on the roof where I shoot from to get 400yrd practice,my brother was down below and I grabbed my mag and thought dang I forgot to unload it from last year,so I decided to shoot those first.The first shot I didn't really think it sounded bad and the bolt opened up ok,the empty rolled off the roof and my brother picked it up while I shot one more.After the shot I heard my brother yelling to stop because my brass was falling apart in two pieces.Well that mag was my buddy's .270 and the cases were stretching and breaking about 1/2" from the base.I couldn't get less than 6-7inch group at 200yrds after that with the correct rounds. I tossed all my .280 brass and bought only nickle plated from then on for my other .280s.
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Old September 27, 2011, 06:32 PM   #13
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"That seems a common mistake."

IF that's true, it's incredible.

In some 46 years of reloading and a lot of shooting around a lot of guys and with a lot of rifles, pistols and shotguns, and often with reformed rifle cases with a single headstamp, I've never mis-chambered anything nor do I know of anyone else who has done so. Loading a standard size case in a belted cartridge rifle really isn't a 'small' thing. Nor have I ever skipped or doubled a charge, used the wrong powder or primer, etc. After all, reloading and shooting are not complicated but they are detailed activites, best done by careful people.

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Old September 27, 2011, 06:51 PM   #14
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Duplicate, deleted.
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