I'm interested in doing a 264-300wmi, but was thinking on going 264-338nmi? I used ql for unimproved on both and both show very similar results. I can save powder by going 300wm case over 338nm. The only + on the 338nm case is it being shorter. What would be a good choice and how to proceed? With a 32" barrel using 156's velocity is around 3,400. That's giving me around 4k muzzle energy. I'm not a nosler fan or want a bee case ir even a 300prc converted, but wouldn't mind it being non-belted!
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Best possible reamer
- Thread starter ARlife4me
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MagnumManiac
Well-Known Member
I have done many 6.5mm wildcats, none have been larger than a RUM case.
I understand you don't want a Weatherby case, but it's hard to beat the 6.5-300 Weatherby for what you want…
The efficiency of the 300WM case is second to none, it is an excellent choice for 6.5/7mm, but, you are much better off using the dimensions of the A191 chamber when designing your reamer. I did this on my custom 264WM, it is magnificent at keeping the brass tight in the chamber after fireforming the shoulder.
What I found with both the 6.5mm and 7mm using a 7RUM as the basis, was extreme throat erosion, barrels lasted 600 rounds with excellent accuracy, beyond this, fliers got worse and worse and at 800 rounds, the barrels were toast. Both Stainless 416R barrels.
When I developed my wildcats on 416 Rigby Improved cases, the thought of doing a 6.5mm or 7mm had me wondering how many rounds I would get running 120g+ loads, my guess was 400 with good accuracy and done at 500.
The NMI is probably going to burn barrels like the RUM case does, albeit slower with a 40° shoulder, it will still be a 600 round venture.
Cheers.
I understand you don't want a Weatherby case, but it's hard to beat the 6.5-300 Weatherby for what you want…
The efficiency of the 300WM case is second to none, it is an excellent choice for 6.5/7mm, but, you are much better off using the dimensions of the A191 chamber when designing your reamer. I did this on my custom 264WM, it is magnificent at keeping the brass tight in the chamber after fireforming the shoulder.
What I found with both the 6.5mm and 7mm using a 7RUM as the basis, was extreme throat erosion, barrels lasted 600 rounds with excellent accuracy, beyond this, fliers got worse and worse and at 800 rounds, the barrels were toast. Both Stainless 416R barrels.
When I developed my wildcats on 416 Rigby Improved cases, the thought of doing a 6.5mm or 7mm had me wondering how many rounds I would get running 120g+ loads, my guess was 400 with good accuracy and done at 500.
The NMI is probably going to burn barrels like the RUM case does, albeit slower with a 40° shoulder, it will still be a 600 round venture.
Cheers.
Just another reason for asking! Getting responses from people with experience. Thanks!
Ideas can look good on paper, but not worth it in the longer run. Fun trying tho.
had a 6.5-300win mag just for fun and a learning experience and it is everything the 26 Nosler is and just as tough on barrels.
if you're designing your own reamer I would suggest having a .330 neck on your reamer and a 35 or 40 degree shoulder. the win mag neck is too short to chase lands and longer neck and steeper shoulder will help extend usable life. find yourself a takeoff barrel to rechamber for fireforming and basic load development.
i was just short of 3500fps with the 147eld-m in a 26" barrel and the explosive impacts were more of what you would expect from a varmint bullet. it was definitely a learning experience but not one i will repeat.
if you're designing your own reamer I would suggest having a .330 neck on your reamer and a 35 or 40 degree shoulder. the win mag neck is too short to chase lands and longer neck and steeper shoulder will help extend usable life. find yourself a takeoff barrel to rechamber for fireforming and basic load development.
i was just short of 3500fps with the 147eld-m in a 26" barrel and the explosive impacts were more of what you would expect from a varmint bullet. it was definitely a learning experience but not one i will repeat.
This would be a 140 and up class bullet cartridge. That's what I'm hoping for is a 35° shoulder w/longer neck than the 264wm.
you can push the shoulder back and angle down to get neck length, will have to turn necks and watch for doughnuts, blow the shoulder dia. out .010-.012 to get most of your original case capacity back and still have good extraction. this might be a good one for fast twist barrel and mono bullets.
MagnumManiac
Well-Known Member
I let my necks grow within .010" of chamber end, this gives you ample extra neck length, normally .040" more length.
I do this on everything, no chance of a carbon ring!
Cheers.
I do this on everything, no chance of a carbon ring!
Cheers.
IMO a Norma case would be so overbore you would be burning a lot of extra powder for little to no gain.
My 26 Nosler throated to 3.700" runs the 156 EOL comfortably at 3350 and have run it as high as 3450 with a 28" barrel.
I was trying to keep the brass shorter than what the nosler and wm are to have oal no more than 3.600"? Using n100 powders as to keep temps down yo save throat.
MagnumManiac
Well-Known Member
Not necessarily, the abrasive aspect of the powder if allowed to follow the bullet and 'funnel' into the throat is just as bad as the heat from a hotter powder.
This is why my large wildcats have 40° and 45° shoulders, it holds the powder in the case longer.
Ball powders also reduce this abrasive affect on throats.
Cheers.
I'm running H50BMG powder in my Nosler which is an Extreme powder. Not sure where it sits on the burn temp scale. Which N100 series powder will get the kind of velocities your are trying to achieve?
Why are you wanting to stay at 3.600"?
165 & 170 for a good case fill and still not 100% iirc.
