18-20" 300 RUM: change my mind..

[7.62 Gunner]

Negligible, nothing that trying multiple powders can't overcome. It's a huge case and full capacity isn't actually used by most powders. Retumbo, 7828SSC, Magnum, H1000, RL33 and LRT all book at less than 100% load density in SAAMI COL of 3.600" using bullets from 180gns and up, meaning you won't be using the case volume you're losing to seating the bullet at 3.840 vs 3.940.

My 300 RUM shoots certain things fine stuffed down, specifically 210 AccuBond LRs. Worst case if the 225 ELD sucks change the bullet out.

Yeah its a huge friggin case!
That was my thought as well, 3.840 with the 225 is actually seated out decently in my opinion I'm just used to guys saying a 4" box is needed with the RUM

 

[QuietTexan]

I was all ready to get a Wyatt's box for mine because Berger 210 VLDs got close to 4" seating at the lands, but there were other bullets that shot fine sat deeper.

I'm shooting a factory barrel so "fine" might should read "acceptable" because it's not what I would accept from a good barrel and chamber job, but definitely capable of schwacking animals.

 

[comfisherman]

I'm running a 24" 30 Nos that I'm head over heals for, except that it's stupid frigging long with my Nomad LT suppressor.
The suppression and recoil reduction is amazing to the point that I refuse to ever put the brake back on.
Soo I'm looking to go with a short barrel and continue the suppressed goodness with 225 eldms around 2800 fps.
I don't buy into the "Efficiency" crap, and 700-1000 rounds will take me 4-5 years of shooting.
I have a 3.850 mag box
What do you all think?

And please for the love of Jesus don't recommend a 30 Sherman Mag...

I've built a 20 inch 300 as well as a 21 inch 7 rum. There is definitely loss from a 26" but I'm still way ahead on fps. I've chopped a lot of overbore cartridges down over the years, there is usually a threshold on the non linear progression of velocity loss. A 7-08 may loose 15-20 fps less per inch than a 7 rum.... but that 500 fps start means you need a - barrel lenghts for them to catch each other.

It's like commuting in a sports car, it's loud expensive and a bit uncomfortable... but if you don't mind the $$$ the performance is fun.

 

[laker]

I cut a 6.5 prc from 22" down to 17". Lost 24'/inch

 

[simmonzz]

I cut a 6.5 prc from 22" down to 17". Lost 24'/inch

So you got a creedmoor now? Lol. I had a 16.5" 6.5 saum and it was identical as far as velocity to my 18" creedmoor. Tried a ton of powders and it was the same thing. Learned my lesson on that one lol

 

[laker]

So you got a creedmoor now? Lol. I had a 16.5" 6.5 saum and it was identical as far as velocity to my 18" creedmoor. Tried a ton of powders and it was the same thing. Learned my lesson on that one lol

2850fps with a 140 Berger. Show me a creedmoor that will do that with a 17" barrel. The barrel actually did start life as a creedmoor and I swapped bolts and had barrel reamed. As a 24" creedmoor it wouldn't break 2800fps The point was to have a handier rifle suppressed.

 

[simmonzz]

2850fps with a 140 Berger. Show me a creedmoor that will do that with a 17" barrel. The barrel actually did start life as a creedmoor and I swapped bolts and had barrel reamed. As a 24" creedmoor it wouldn't break 2800fps The point was to have a handier rifle suppressed.

My 18" creed shoots 143s at 2680 but yea that is faster. Idk why that 16.5" 6.5 saum didn't outpace my creedmoor but it was what it was.

 

[laker]

My 18" creed shoots 143s at 2680 but yea that is faster. Idk why that 16.5" 6.5 saum didn't outpace my creedmoor but it was what it was.

I was thinking about punching the prc out to Sherman max but I don't know if it's worth it or not

 

[codyadams]

My 18" creed shoots 143s at 2680 but yea that is faster. Idk why that 16.5" 6.5 saum didn't outpace my creedmoor but it was what it was.

What type of barrel was your 16.5" 6.5 saum?

 

[Harry Knutz]

Please carry a "Fire Extinguisher"

 

[Ernie]

My 6.5 PRC, which is an 18 inch barrel with factory ammo 143's, runs at 2875 to 2850 ft./s I need to check. My 6.5 300 WSM or the leopard runs faster than that. If I reload my 6.5 PRC my muzzle velocity is somewhere between 2875 to 2890 ft./s. My 17 inch 6.5 284 runs 140 Accubonds at 2780ish

 

[Ernie]

Please carry a "Fire Extinguisher"

Laughing
338 Lapua Improved 300 grain SMK


7mm Dakota 83 grains of RL33 175 grain at 2900 fps


6.5-300 WSM (Leopard) 3020ish with a 130 Berger. More powder and a faster velocity than you would get with the 6.6 PRC

 

[Harry Knutz]

Laughing
338 Lapua Improved 300 grain SMK


7mm Dakota 83 grains of RL33 175 grain at 2900 fps


6.5-300 WSM (Leopard) 3020ish with a 130 Berger. More powder and a faster velocity than you would get with the 6.6 PRC

It was a Joke!

 

[QuietTexan]

What brake is that, I need that brake

I'm working on a 30-338 reamer currently, I didn't think about putting it into a 14" pistol barrel also.