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shooting 6.5 Creedmoor out of a .308 barrel

WC_Harris

We accidentally shot 6.5 Creedmoor out of a .308 this morning. It was my oversight letting a box of 6.5cm get mixed into my .308, the boxes look identical without my reading glasses on. Anyway, my partner took a shot and said something's not right, it didn't kick right. Then he looks at the cartridge and says "this is 6.5 Creedmoor!".

I didn't even know that was possible, to chamber the wrong cartridge. The shot was good at 600 yards, it was on steel but I wasn't spotting so I don't know how far off aimpoint. Could this damage the rifle? They didn't think so. I don't reload so I don't know the issues involved with the misfit of the cartridge. Rifle is a Steyr SSG 08 A1.
 
WC_Harris said:
We accidentally shot 6.5 Creedmoor out of a .308 this morning. It was my oversight letting a box of 6.5cm get mixed into my .308, the boxes look identical without my reading glasses on. Anyway, my partner took a shot and said something's not right, it didn't kick right. Then he looks at the cartridge and says "this is 6.5 Creedmoor!".

I didn't even know that was possible, to chamber the wrong cartridge. The shot was good at 600 yards, it was on steel but I wasn't spotting so I don't know how far off aimpoint. Could this damage the rifle? They didn't think so. I don't reload so I don't know the issues involved with the misfit of the cartridge. Rifle is a Steyr SSG 08 A1.
Click to expand...
I doubt you hurt anything. Can you post a picture of the fired brass? I would like to see what it looks like.
 
Edd said:
I doubt you hurt anything. Can you post a picture of the fired brass? I would like to see what it looks like.
Click to expand...
I didn't take a picture and I didn't keep the brass. Sorry. Yes, now I wish I had kept it. I'll ask my partners if they kept it but I doubt it.
 
What happened in your case is basically what we do when we are fire forming brass during the wildcatting process. This is also what is basically being done when fire forming improved cartridges (ie .243 A.I). Some to save money don't even load a bullet into the brass. I used wax and paper towels on top of a mild powder charge (LOL). Why waste good bullets ;-) Some I've heard use say a .224 bullet in a .243 barrel (.22 bullets are cheaper than 6mm or 6.5mm bullets). The smaller bullet rattling down the barrel doesn't really hurt anything. Many of the bench rest guys have barrels just for forming brass. They don't want to shoot out their hummer match barrels. They save their hummer barrels for fire formed brass and competitions.

It is surprising how accurate the rounds shoot when forming the brass. My bench rest gun shoots pretty good when forming my brass. The brass and bullet are close to the actual chamber so this makes a big difference. Some guys shoot matches while forming their brass as the gun shoots that good (F-Class).

PO Ackley did experiments on what was possible with the wrong cartridge and chamber combo. I can' t remember what he shot I think it was a 308 out of a 30 06 chamber. In any case it didn't blow up the gun.
As mentioned earlier you're fine. Just be more mindful with your process and clean your rifle well after an event like this.

-Cheers
-R&B
 
WC_Harris said:
We accidentally shot 6.5 Creedmoor out of a .308 this morning. It was my oversight letting a box of 6.5cm get mixed into my .308, the boxes look identical without my reading glasses on. Anyway, my partner took a shot and said something's not right, it didn't kick right. Then he looks at the cartridge and says "this is 6.5 Creedmoor!".

I didn't even know that was possible, to chamber the wrong cartridge. The shot was good at 600 yards, it was on steel but I wasn't spotting so I don't know how far off aimpoint. Could this damage the rifle? They didn't think so. I don't reload so I don't know the issues involved with the misfit of the cartridge. Rifle is a Steyr SSG 08 A1.
Click to expand...
Wow! A pretty good story. I have two Creedmoor's
And a bunch of 308s .... so let's test this theory... shall we?
First test ...2 new Lapua cases one 308 one 6 5 Creedmoor ...the datum line at the 30 degree shoulder drops exactly. 072" deeper for the Creedmoor...IF the 6.5 would chamber in the 308 ...it would be hard for the firing pin to reach it.
Test #2 prime the new Lapua brass ...in anticipation,.. chamber it.. and see if it sets off the primer ...right? But the 6.5 Creedmoor won't chamber in 308 rifle #1, or rifle #2, or rifle #3..had to tap the case out with a cleaning rod...it was about .250" from closing the bolt on one as I tried too hard to close the bolt. Had a Remington extractor pop over the case head but couldn't come close to chambering the 6.5, and pounded on the bolt handle to extract it. Wow, thats a problem...wonder why?

So let us measure...shall we? The 6.5 Creedmoor is .010 wider at the shoulder than the .308 Win Lapua cases....so a 6.5 Creedmoor can not chamber in.. a in print .308 standard chamber.
Wow, kind of a problem...

I have shot 7 mag in 338 mag on purpose. The velocity is really low like 1900 fps maybe and bullets missed a big tree at 30 yards.
Just recently shot a 45-90 with .451 pistol bullets instead of .458 rifle bullets ...results at 30 yards all the pistol bullets went sideways, in an 8" group, with a bullet only .007" smaller in diameter. So .264" in a .308" is an extreme difference and muzzle velocity would likely be msybe 1500 fps with all the powder gas blasting by the .264" bullet and the bullet start to tumble instantly, so no accuracy would begin at the muzzle.
If it was possible to chamber it... in an out of spec chamber and shoot it, it would likely strike 200 yards short 80 yards to one side and skip off the ground and into "the steel".

Don't worry I didn't give up yet! How about that trusty 308 body die ...let's set it up for 308 and check it to be sure it's dead on ...then body size down the 6.5 Creedmoor shoulder, with our new primed Lapua case...insert our full 308 body resized 6.5 case into the 308 chamber...Wow it fits...the bolt closed...but will it fire? Pull the trigger...bang! Yes it does...but open the bolt the 6.5 case is still way down in the chamber...tap it out with a cleaning rod...the primer is set out of the case head about .070".

So in conclusion the only way to get a 6.5 Creedmoor round into a 308 chamber is to body size the 6.5 Creedmoor in a 308 body die ...or take empty 6.5 Creedmoor cases and try to load them in 308 dies without noticing the problems you'd have, with that...like expanding the necks in one pass without collapsing the shoulder, splitting the necks, etc, not very likely.
I'm an experimenter with lots of tools at my disposal...guns are a hobbie... sometimes I'll take the time to consider and check out the possibilities...it has to be ....reasonable, and plausible. And if your 308 gun chambers 6.5 Creedmoor the chamber is out of spec at the shoulder...or shooting a 308 improved...but I'm not gonna check that as a possibility.
...And that concludes my experiment on that.
Also...I'd save the 308 and discard the 6.5 Creedmoor...I own and shoot both...but I'm not, because the 6.5 won't chamber in any of my 308s so the experiment wasn't a waste of time.
As always have fun...and don't you just love analytical thoughts and experinents?...Yeah, I'm outside the box, sometimes I can't find the door, and many times it's no fun in there...to boring.
 
Mix ups can be disastrous. A friend in the heat of the moment fired a .308 in a .270. Blew most of the center out of the stock. Plenty of wood splinters in the face and left and arm. No permanent injuries to the shooter.
No mater how long we've been doing this sometimes we can use a stiff dose of "slow down and be careful"!
 
6.5mm bullet bore is smaller than .308" bore so no harm done.
SAAMI mostly makes sure you cant chamber a bigger diameter caliber bullet down a a smaller bore.
 
If that hit steel, it was almost 100% likely to be tumbling. .264 is obviously smaller diameter than 308.... There would be no rifling to grab onto.

Where you get hurt is if you did that in reverse and the bullet had jump. Boom.


Glad you lived to learn from your mistake.
 
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