7MM WSM vs 6.5/300 WSM

[BoatTail]

My original reason for building the 6.5/300 WSM was seeing the long-range potential of the 6.5 bullets and its successful use in all the other standard and wildcat cartridges. Although I have 2 tack driving custom 28 Nosler rifles that I have been using for Antelope, I wanted a smaller caliber, lighter rifle, with around a 140 gr bullet, that I could dedicate to antelope.

 

[L.Sherm]

There is more to consider with big overbores than simple MV.
3,200 ft/sec was mentioned with 140s from the WSM case. I can get the same from a WSSM case, using way less powder.
The difference is pressure of course.

Pressure creates force as pounds per square inch (PSI). So with a given pressure, the forces exhibited with a WSM case area are a lot higher than those from a WSSM case area. That's why I can run higher viable pressures with the 6.5WSSM.
And choosing a high pressure load -vs- low pressure load is easy for me. I choose higher, for advantages of it -with a good plan.
That's my basis for a notion that bigger is not better.

For an extreme analogy of this, consider the tiny little 6PPC for point blank BR competition. It's an underbore.
Why doesn't anybody compete against it using an overbore cartridge?
Well, they could try, and they'll lose for sure.
A competitive 6PPC load runs up around 75Kpsi. This is viable (somewhat) because the case area is so small.
It's competitive because pressures that high are deep into diminished returns, which results in diminished variance of returns.
A 243Win can match same & higher MV easier -while shooting like a dog compared to a 6PPC.

Since I see accuracy as the most powerful of all ballistic attributes, I am not out for biggest velocity numbers.
I prefer more disciplined, logical, designs.
I know somebody out there is shooting 1/4moa regular with giant overbores, but I could never rely on the luck it takes to find that.

O.k since you mentioned it. I hate posting groups but here it is 8.25lb all carbon 6.5x300wsm 871 yards 140 berger 4" wide 1" vertical off a bipod. 3" black circle

 

[L.Sherm]

Why doesn't anybody compete against it using an overbore cartridge?
Well, they could try, and they'll lose for sure

Thats in short range, alot of 1,000Br guys are migrating away from there 6mms to 30 cals its alot of talk on accurateshooter

 

[Mikecr]

My original reason for building the 6.5/300 WSM was seeing the long-range potential of the 6.5 bullets and its successful use in all the other standard and wildcat cartridges. Although I have 2 tack driving custom 28 Nosler rifles that I have been using for Antelope, I wanted a smaller caliber, lighter rifle, with around a 140 gr bullet, that I could dedicate to antelope.

They why choose a magnum cartridge? You could go 6.5x47L/130s, or 260AI/140s for antelope.
You wouldn't need longer barrels to keep your hat on, and burn em out with excess powder.

 

[BoatTail]

About my struggles with the 6.5/300 WSM. After I received the rifle I took it to the range to do a barrel break-in. I used a mixture of new and once fired 270 WSM brass resized and neck turned to my 6.5 WSM requirements. What I discovered was the new brass would fit into the chamber but resized brass would not. I've attached a pic of the once fired brass that has been resized and re-loaded. Yes there is a web mark but it's made brighter when attempting to chamber it in the 6.5 WSM. Let me explain.

That web area near the base of the case is where the once fired brass would hand up on loading and not completely seat. Also, some of the new brass had periodic extraction issues. Thinking it was an issue with my 6.5/300 WSM sizing die, I resized them with a 270 WSM die with the neck expander ball removed. This had no effect as the resized reloaded cases still would not seat/headspace right.

Last night I looked at the problem closer and I discovered an issue I missed. When I initially worked with my reamer manufacturer on this project, I asked for a SAAMI 270 WSM drawing to document my requested changes. I have done this many times in the past with them making the final adjustments and validations prior to reamer creation. I focused on the neck size, lead, throat and that forcing angle. Where I made the mistake was I did not check the rest of the reamer dimensions to ensure those matched the SAAMI 270 WSM.

This is what I found. On the SAAMI 270 WSM drawing, at 0.200" from the case face, the reamer diameter is supposed to be 0.5563". On the provided 270 WSM drawing for my changes, that same location shows 0.5545" or 0.0018" smaller than the SAAMI version it should have been based on.

This next part is where I get a little confused. After resizing/forming the 270 WSM once fired cases, the same location, or web area, measures around 0.55". That should not create an interference fit but somehow it does and it is evidenced by the shinny mark on the case web area after attempts to load it.

What's clear is I did not properly review the rest of the drawing to validate the reamer dimensions. In the past I had relied on the vendor to check me to help me avoid stupid mistakes, I now realize it is my responsibility to catch any issues and the mistake is on me.

This then gets us back to the initial question. Do I even need the 6.5/300 WSM with my new 7mm WSM? Should I have a new 6.5/300 WSM reamer made with the correct chamber size? Is it possible to run a new reamer back into the existing chamber to correct the dimensions, or would it be iffy or create a possible off center chamber issue? The other options are to re-barrel the rifle with a new 6.5 barrel or switch to a 270 WSM barrel.

Thoughts?

 

[nealm66]

Thoughts = aw crap

 

[L.Sherm]

There is absolutely nothing wrong with the 6.5x300wsm for a hunting rifle just as accurate as any other 6.5 out there. Having a reamer speced right for any wildcat is one of the keys. I've been playing around with one for 15 years and learned a few lessons along the way.
One is dont go larger than a .296 camber neck otherwise you will fight consistent neck tension one of my fits one the first go round. Second is you have to sort and prep 270wsm WW brass to get consistency, its why I'm a firm believer ADG 300wsm brass will help a ton.

 

[BoatTail]

There is absolutely nothing wrong with the 6.5x300wsm for a hunting rifle just as accurate as any other 6.5 out there. Having a reamer speced right for any wildcat is one of the keys. I've been playing around with one for 15 years and learned a few lessons along the way.
One is dont go larger than a .296 camber neck otherwise you will fight consistent neck tension one of my fits one the first go round. Second is you have to sort and prep 270wsm WW brass to get consistency, its why I'm a firm believer ADG 300wsm brass will help a ton.

So you are turning necks? Are you also annealing?

 

[L.Sherm]

So you are turning necks? Are you also annealing?

Yes and yes

 

[BoatTail]

They why choose a magnum cartridge? You could go 6.5x47L/130s, or 260AI/140s for antelope.
You wouldn't need longer barrels to keep your hat on, and burn em out with excess powder.

I guess I was looking for the performance of a magnum cartridge but in a smaller more efficient case (as compared with those like the 26 Nosler or 6.5/300 Weatherby)

 

[L.Sherm]

I can get the same from a WSSM case, using way less powder

So you can get 3200fps with a 6.5wssm in a 26" barrel and accurate with a 140 bullet im not talking just max velocity because I have no doudt it will go over 3300 but it will kill the WW brass PP in all likelihood and I spend alot of time preparing brass.

 

[Mikecr]

I've only run it over 3200 in testing for 'MyMax' pressure. This is a point where FL sizing would be required (for my chamber).
I use 28" barrels, and I did no accuracy testing up there, as FL sizing is not in my plan.
I chose a milder/mid node putting me at 3025fps, with 139Laps, ~47gr IMR4350. I don't know where mid node would be in 26" barrels, but I know the muzzle pressures would be higher than I want.
My accurate barrel life is 1850rnds,, on my 3rd barrel now,, same 50 cases.

My 26WSSM matches 260AI capacity (by design). While not the fastest, I believe it's the best capacity overall for ~140gr 26cal bullets.
Also pretty sure it could kill anything in the USA

 

[DJ Fergus]

I just had two custom rifles built, one in 6.5/300 WSM and 7MM WSM that I will discuss later. For now I want to introduce the the discussion and get your thoughts. If have a 7MM WSM that is able to shoot a 162 gr Hornady ELD-X's bullets at 3170 fps with 1/2" accuracy at 100 yrs, why would I want to do the load work for and keep a wildcat 6.5/300 WSM?

Both are built on a trued Remington 700 Short actions with 3-B (BAINEY) Extended Magazine Box & Followers. The inside length of these magazines is 3.110" and the bottom of the rifle and ejection port on both are opened up to allow for the larger Magazine box and proper ejection. This allows a longer throat/COAL from custom reamers. Both barrels are Hart #3's at finished at 25" with T1 Terminator muzzle brakes. Both have McMillian Remington Hunter stocks.

Thoughts on keeping both, just one or the other, or changing one to another caliber? I have 270 and 308 barrels I could change to.

I have several 7mm and 6.5 cartridges. I can tell you for a fact that a 162 @ 3050 fps is very lethal on white tail. I'm sure even more so @ 3170. I run a 6.5 saum @ 3150 with a 147gr. The ballistics of my 6.5 saum should be really close to your wsm with the 162. I would say your wsm has the advantage in terminal performance. I wouldn't change a thing about that 7mm wsm that you mention.

 

[338Rules]

Has anyone worked with the 6.5 x 6.8 Western ?
a little less case capacity, longer neck than the WSM.
A little more than the WSSM. Just right ?