What is the most overbore cartridge YOU HAVE USED?

[Calvin45]

I feel a bit inadequate after reading through this thread. I'm currently shooting fairly efficient cartridges, but after reviewing the list Feenix provided some may be considered overbore. I can't imagine hunting with a 30+ inch bull barrel. I'm actually looking to build a shorter barreled 7SAUM. I do enjoy reading the responses and performance from the wildcat crowd.

I always find we learn a lot along the way when we push the envelope. Even if we learn what doesn't work, that's still learning. I'm glad I started this thread, it's been a fascinating read so far.

 

[Calvin45]

I feel a bit inadequate after reading through this thread. I'm currently shooting fairly efficient cartridges, but after reviewing the list Feenix provided some may be considered overbore. I can't imagine hunting with a 30+ inch bull barrel. I'm actually looking to build a shorter barreled 7SAUM. I do enjoy reading the responses and performance from the wildcat crowd.

I didn't read all the replies, so this may have been covered already. When I do the accuracy qualification of our 300 WM rifles I use a load of 80.5gr of H1000 under a 180gr NBT. This usually yields a speed of around 3100-3150 depending on barrel length. The load I use for the 30-378 WBY is 100gr of H1000 under the same 180gr NBT. The speeds usually hover around 3250-3275, again, depending on barrel length. That's a pretty meager 100-125fps gain considering the huge powder, recoil, and muzzle flash increase with the Weatherby. To each their own, I guess.

Agreed. If you buy a .30-378 just to shoot a 180 grain bullet out of a 26 inch barrel that's awfully inefficient.

Out of ordinary sized "hunting" rifles it's really hard to meaningfully improve upon the original .300 weatherby and newer .300 RUM in any worthwhile manner.

Run a 30+ inch pipe and shoot 220-250 grain bullets and I hear the big case starts to flex its muscle.

Sort of like trucks haha…my dad's former truck had was a Chevy/gmc with the big 454 big block v8. Horribly inefficient to just drive down the highway…didn't even have much more acceleration really than the older 305 v8 in the 80s truck before that one…but pulling a real heavy load up a hill that big 454 was just a beast getting warmed up and the smaller engine struggled a lot and couldn't possibly keep pace (if one was racing trucks with trailers up a hill like an idiot haha).

Getting a .30-378 to shoot 180s out of a standard length barrel is like having a 454 v8 3/4 ton to haul…groceries!

 

[Calvin45]

I didn't read all the replies, so this may have been covered already. When I do the accuracy qualification of our 300 WM rifles I use a load of 80.5gr of H1000 under a 180gr NBT. This usually yields a speed of around 3100-3150 depending on barrel length. The load I use for the 30-378 WBY is 100gr of H1000 under the same 180gr NBT. The speeds usually hover around 3250-3275, again, depending on barrel length. That's a pretty meager 100-125fps gain considering the huge powder, recoil, and muzzle flash increase with the Weatherby. To each their own, I guess.

And I'll add…out of my own ordinary-ish size and weight hunting rifles for all purpose all range all big game use the .300 win mag you mention is still my favourite cartridge, the king of practical horsepower with versatility.

 

[HRM Johnny]

If I was building a 257 Wby, I would use a barrel at least 36-in.
I think a simple 7RM needs a 32-in barrel, and the 257Wby is even more overbore.

Thank you very much. I appreciate it.

 

[Stokesrjsr]

I didn't read all the replies, so this may have been covered already. When I do the accuracy qualification of our 300 WM rifles I use a load of 80.5gr of H1000 under a 180gr NBT. This usually yields a speed of around 3100-3150 depending on barrel length. The load I use for the 30-378 WBY is 100gr of H1000 under the same 180gr NBT. The speeds usually hover around 3250-3275, again, depending on barrel length. That's a pretty meager 100-125fps gain considering the huge powder, recoil, and muzzle flash increase with the Weatherby. To each their own, I guess.

I think you are limiting the performance of the 30-378 with your load selection. I shoot that same bullet with 107.5 grains of retumbo at 3425 fps. Even the Weatherby factory load achieves this velocity or close enough, 3,420.

 

[.300 Dakota]

Don't know if this goes here or on reloading forum, but figured I'd ask…

What is the most overbore cartridge you ACTUALLY have experience with? The craziest hot rod, the biggest case to bore ratio, the most ridiculous magnum, this worst barrel burner….

What have you learned from it? Would you do it again?

I know everyone on these threads makes jokes about a .17-50bmg or references the .22-378 eargesplittenloudenboomer experiment by ackley…I don't care about those. I don't know of a single person who has ever done such a thing in any serious effort. I'm trying to avoid that and learn about people's experiences and learning from actual field rifles in very overbore factory chamberings or more so truly impractical but still useful wildcats. I'm entertaining the thought of one myself.

@ButterBean @Fiftydriver @MagnumManiac i know you folks off the top of my head have played with some big cases pushing small bullets….

I read the title of this thread without seeing your posted comments. How coincidental that I was going to report the same cartridge as you - the 6.5x300 Wby. However, now that I think of it, I believe the 7mm RUM may have been even more overbore - or at least about equal. While it's 2 calibers larger, it holds about 15 more grains of water. My current pet project is no slouch, either - a .257-.264 Win Mag. About equal to the .257 Wby in the overbore department.

 

[Lenny Foffa]

Mr. Cove, the Weatherby factory will take care of both your issues, switch out the barrel of your .257 to a 26 inch and add a Muzzle break. I just had a Muzzle break installed on my Weatherby Ultra-Light , in 270 Win, by the factory and it looks perfect . It works real good too. Just a suggestion.

 

[cape cove]

If I ever have a 257 again it will certainly have a 26" barrel. In fact I believe the new Vanguard's come with a 26" barrel As for a muzzle brake I don't believe one is needed on a 257. The recoil is very manageable.

 

[Mike Matteson]

Agreed. If you buy a .30-378 just to shoot a 180 grain bullet out of a 26 inch barrel that's awfully inefficient.

Out of ordinary sized "hunting" rifles it's really hard to meaningfully improve upon the original .300 weatherby and newer .300 RUM in any worthwhile manner.

Run a 30+ inch pipe and shoot 220-250 grain bullets and I hear the big case starts to flex its muscle.

Sort of like trucks haha…my dad's former truck had was a Chevy/gmc with the big 454 big block v8. Horribly inefficient to just drive down the highway…didn't even have much more acceleration really than the older 305 v8 in the 80s truck before that one…but pulling a real heavy load up a hill that big 454 was just a beast getting warmed up and the smaller engine struggled a lot and couldn't possibly keep pace (if one was racing trucks with trailers up a hill like an idiot haha).

Getting a .30-378 to shoot 180s out of a standard length barrel is like having a 454 v8 3/4 ton to haul…groceries!

More like an S-10.

 

[AZShooter]

Enjoyable thread everyone! With powder prices through the roof, I can't help but think some of us will not be experimenting with overbore cartridges as much as we once did.

I tried the 6-284 in a 30" barrel. It shot the 105 Bergers wonderfully for around 1100 rounds. It was extremely heavy, nothing I would take on a hunt.

I owned a 7 Rem mag reamer and had it reground to make a 6mm-7 Rem mag. I wanted to load it in a sporter weight package and try to duplicate the same velocity that of the longer barreled 6mm-284. Perhaps it was the choice of rechambering a 243 Remington takeoff, as it isn't the smoothest barrel to use. It seemed that I would begin to find a load only to have the powder fouling so severe that in just a few rounds the groups would open up. Thinking about it now it could have been carbon build up in the end of chamber and throat. I abandoned the idea.

Another overbore rifle is a 257 Weatherby now on its second barrel. I will be using this chambering for the rest of my life. It is perfect for coues wt hunting. The 9 1/2 lb rifle used a 28" 3 groove with a custom reamer with approx .100" freebore and a 1 1/2 degree throat angle. It was outstanding with RL-25. Moly coated 115 Bergers were close to 3700 fps. Second barrel is a 27 1/2" 3 groove using same bullet with RL-33, yields a very accurate 3675. FYI I do my own barrel work.

Had several 7 Rums. with one notable Rifle loaded 140 ballistic tips and got tiny clusters at 3665 fps. Got bored and sold it before I burned it out.

There is one chambering I am considering making in the future. I acquired a complete package for a 300 Win Mag Ackley Improved from a 1000 yd BR guy who quit the activity. Whidden custom dies, reamer used once, 100 pcs of once fired RWS brass. One of these days I'll find a buyer for this or build it. Have a 300 RUM reamer and all the components for it, so I often wonder why I would try it. Guess this stuff is in our blood.

 

[82nd Bill]

Don't know if this goes here or on reloading forum, but figured I'd ask…

What is the most overbore cartridge you ACTUALLY have experience with? The craziest hot rod, the biggest case to bore ratio, the most ridiculous magnum, this worst barrel burner….

What have you learned from it? Would you do it again?

I know everyone on these threads makes jokes about a .17-50bmg or references the .22-378 eargesplittenloudenboomer experiment by ackley…I don't care about those. I don't know of a single person who has ever done such a thing in any serious effort. I'm trying to avoid that and learn about people's experiences and learning from actual field rifles in very overbore factory chamberings or more so truly impractical but still useful wildcats. I'm entertaining the thought of one myself.

@ButterBean @Fiftydriver @MagnumManiac i know you folks off the top of my head have played with some big cases pushing small bullets….

I built a 25 WSM that was a seriously accurate and reliable speed demon. Berger 85g at 3850 fps. It was a challenge to find the right load but when I did it worked very, very well. Set it back around 50 off and the barrel now has around 350 rds and no erosion. It has dropped a lot of deer at close and long range. All of them were DRT.
Would I do it again, yes.

 

[QuietTexan]

17-223 AI is a nice little round. Pushed me to get a 17-250 AI reamer that I haven't used yet. They're just toys though, they really don't do anything that my 17WSM (rimfire) doesn't do well enough.

Also I just got my 6 WSM and 20 WSSM reamers in from PTG, can't wait to try those out.

 

[Calvin45]

17-223 AI is a nice little round. Pushed me to get a 17-250 AI reamer that I haven't used yet. They're just toys though, they really don't do anything that my 17WSM (rimfire) doesn't do well enough.

Also I just got my 6 WSM and 20 WSSM reamers in from PTG, can't wait to try those out.

20 WSSM would be one ridiculously extreme looking round….in a good way!

 

[6.5x300 WBY]

Just wanted to say one more thing about my beloved 6.5x300 weatherby.

I love it so much I purchased a custom ammo case just for my baby