Cartridge design help please

[Hired Gun]

In a Weatherby where they top out is usually about where they like to run. With factory ammo the 300 Wby would do 3300 with 180's. The 270 would get 3500 with 140's. The 257 with my loads was able to get 3700 with 100 grain Barnes X bullets. All in 26" barrels showing a pretty good extractor mark on the soft Weatherby brass. I ended up shooting 110 AB's at 3450 for my final load. I think you would stick the bolt on a WSM trying to duplicate anything a Weatherby can do.

 

[Hired Gun]

I doubt a full 100 with 165's but certainly over 50fps using 7828.

I had two 300 Wby's, using 180 Partitions the 26" one was a solid 150 fps over the 24" with less powder.

In a 257 Wby the 24" Vanguard is a almost 200 fps slower with 100 grain bullets than the 26" Mark 5.

 

[cummin_un_glued]

I doubt a full 100 with 165's but certainly over 50fps using 7828.

I had two 300 Wby's, using 180 Partitions the 26" one was a solid 150 fps over the 24" with less powder.

In a 257 Wby the 24" Vanguard is a almost 200 fps slower with 100 grain bullets than the 26" Mark 5.

powder to bore to projectile weight and bearing surface I would think would be a much larger factor then simply the barrel length. sure if you are using a very slow powder in a short barrel then you can set up such a scenario but I belief your examples to be more the exception then the rule.

i'm not building a 30 cal or a quarter bore and the barrel length is decided so the main question here is how much of what powder is it going to take to push the 165gr .277 bullet to 3200fps. if we could figure that out that would tell us what case capacity is needed therefor what parent case to use.

 

[mitch260]

According to Quickloads, you would be lucky to get 3000 FPS out of a 270 wby in a 26in barrel loaded to mag length 3.340" with any suitable powder. Not saying this is 100% accurate, that's just what quickloads is saying.

Now, a 270-300 wby loaded to mag length (3.640") can get about 3150 FPS out of the same barrel length. 85.3 grains of RL-33.

Back to the 270-375 Ruger. This loaded to 3.340" in the same 26in barrel is also getting the same 3150 FPS with the same 85.3 grains of RL-33. To me this seems like the best choice due to the shorter length.

Any of these could be improved by lengthening the throat, plus these aren't real world numbers. Take it for what its worth.

 

[cummin_un_glued]

According to Quickloads, you would be lucky to get 3000 FPS out of a 270 wby in a 26in barrel loaded to mag length 3.340" with any suitable powder. Not saying this is 100% accurate, that's just what quickloads is saying.

Now, a 270-300 wby loaded to mag length (3.640") can get about 3150 FPS out of the same barrel length. 85.3 grains of RL-33.

Back to the 270-375 Ruger. This loaded to 3.340" in the same 26in barrel is also getting the same 3150 FPS with the same 85.3 grains of RL-33. To me this seems like the best choice due to the shorter length.

Any of these could be improved by lengthening the throat, plus these aren't real world numbers. Take it for what its worth.

Mitch thank you sir, that is exactly the kind of info that I was looking for. I am using RL33 in my 7x300win with 180gr bergers. 80gr is getting me 3150fps I did run up to 82gr getting 3200fps but pressure was on the upper end with the short throat that I have.

Is there any way you could run the numbers on the 270 wby improved that I mentioned? I've never used quickload so i'm not sure what all it can do.

 

[BountyHunter]

As for dies, Neil Jones custom dies. Not cheap, but the best. He makes them based off your reamer print with a seater and initially a NS only die.

Shoot them 3x and send him the cases and then he makes a body insert and converts the die to FL bushing to perfectly match your chamber.

 

[MontanaRifleman]

Guess I'll throw my 2 pennies in... The Howa/Vanguard actions are a little on the short side compared to the 700 (I like the Howa's better) so, if you want to efficiently seat thse bullets to maximize case capacity that rules out cases like the 300 WM, 300 WBY, STW, etc.

The 257, 270 and 7mm WBY's have about 3 gr more powder capacity than the 270 WSM. Not a lot of gain in performance there, and IMO the WSM is a more desirable and efficient case.

I'm guessing here, but I think the hoped for velocity is possible with the WSM and Reloader 33. What you are asking for is an overbore case in which you want to shoot heavies out of, which means you need a slow burning powder like 33. Using a relatively short barrel less than 26" is going to cause a good loss of efficiency in that scenario. A 26" barrel including brake is going to be about 24 1/2" long.

My vote goes to the 7 LRM and there should be no problem reaching the desired velocity in that case. The down side is more expensive brass (but good brass), a new custom reamer and custom dies. I don't really consider custom dies to be a downside when it comes to precision shooting.

With the WSM, you might need a custom reamer for the 165 bullets but off the shelf dies are plentiful and Norma makes brass for the WSM. The downside to the WSM is you might fall a little short of the desired velocity (maybe not) but over all you will have less cost. A full 26" barrel would help.

 

[bigngreen]

I don't know what the 7 LRM dies are exactly, I was assuming they'd be the custom bushing dies that Hornady makes which would only need a bushing change.

One thing I don't know about is if there is a higher velocity accuracy node with the 165's everyone I know shooting them now even in chambering that should drive them faster are running them in the 3050fps range.

 

[Edd]

I want to build a rifle to drive the Matrix 165gr .277 bullets 3100-3200fps. I cant decide what brass to put behind this bullet to get the results I want. I am open to having a reamer made. I would like to use some combination of dies that are already out there like I do with my 7/300win using a redding s type bushing die. I would be open to having dies made or modified if I had to though.

Kirby Allen has what you want, a 270 Allen Express.

Allen Magnum Wildcats

 

[Frank7mm]

If going with a custom Whidden makes some very nice dies. Much much better turn around times and cheaper.

 

[mitch260]

Sure can, would be glad to help. Just give me some rough dimensions of what your thinking and I need to know the weight of an empty 270 wby case.

 

[IdahoCTD]

You already have a 7-300wm why not build a .270-.300wm? It will surpass a .270Wby and should beat a WSM by at least 100fps. It not that I would do a .270-300 Dakota or a .270-7LRM. Both would be near the same as a .270-300wm.

 

[MontanaRifleman]

The 300 Dakota has about 9% more capacity than the 300 WM.

The LRM is almost identical to the WM in capacity with a shorter case and slightly less capacity than the 7 Dakota.

The Dakotas and LRM have better but more expensive brass.

 

[cummin_un_glued]

Well i'd rather not use the Dakota brass just because the brass isn't always readily available. I don't want to build another off of the 300win either. I know I know all I would have to do for dies is get 1 more bushing and i'd be done. However I don't think that I need that much case with the 165 and I've already done one off of the 300win case and just dont want to do another. My dad has a 270 Win and a 270 WSM...I want a true magnum 270 of some kind.

Right now its looking like the Ruger case or the improved weatherby case, leaning toward the wby case since its looking like they would be a wash and it would be a lot less work.

Anybody got any other suggestions that we have over looked maybe?