7-300 NMI and 175 begers

[Chris Roland]

I gotta know, we just got a 7-300 NM improved together this past week and got a few shots down it with 175 Berger elites, no sings of pressure at 3411fps, my question is will these bullets stay together and tune at this speed befor i go much further with testing? This chamber is getting blistering speeds. Load is only produced vertical as of now, still early on in the break in process also, 12 shots down the gun so far and it’s fouling pretty heavy, 9tw Krieger with RL33.

 

[Capt. Oblivious]

Your spinning that bullet pretty hard in that 9 twist

 

[46and2]

I gotta know, we just got a 7-300 NM improved together this past week and got a few shots down it with 175 Berger elites, no sings of pressure at 3411fps, my question is will these bullets stay together and tune at this speed befor i go much further with testing? This chamber is getting blistering speeds. Load is only produced vertical as of now, still early on in the break in process also, 12 shots down the gun so far and it’s fouling pretty heavy, 9tw Krieger with RL33.

Is your new barrel powder fouling or copper fouling? Might do a "barrel break-in" session to ease the chambering Mark's in the throat.

Tubb's Dust can help copper fouling.

If your load density with RL33 is low you could try H50BMG or Rl50. Low case fill can cause sooty fouling.

 

[SKWERLZ]

Your spinning that bullet pretty hard in that 9 twist

About 272K.
Up there for sure but generally I have less problems with Berger bullets blowing up than another popular brand.

 

[DaveTooley]

At those speeds heat could contribute to bullet failures. Cores can and do become slightly molten. Probably more than we know.
Pre RUM we used the 404 Jefferies case. We shot the 7's around 3400 FPS, 9 twist, using custom 178's made on Sierra jackets. They stayed together for us.
I think you'll reach a point of diminishing returns when it comes to speed.

 

[Ranger188]

Your RPM's are not that high, as mentioned above (272,880)
But you are burning 90g + or - of powder.
I would really be careful of heat in that barrel (long strings of fire) and CLEAN it regularly.
RL33 is about in the middle of the "heat" range for powders.
With only 12 shots down the barrel, it will more than likely speed up a bit.
Are you using a reduced load for fire forming?

 

[Chris Roland]

Yeah I calculated rpm’s at at 272k + give or

At those speeds heat could contribute to bullet failures. Cores can and do become slightly molten. Probably more than we know.
Pre RUM we used the 404 Jefferies case. We shot the 7's around 3400 FPS, 9 twist, using custom 178's made on Sierra jackets. They stayed together for us.
I think you'll reach a point of diminishing returns when it comes to speed.

take, my main concern was and if anyone has had success with them at that speed, I’m a die hard short range br guy, never messed with big bore 7mm’s much. Iv shot and broke in a many Kriegers over the years and never seen one foul this much on one shot cleans lol, I’m assuming and hoping fouling right now is due to big HP so to speak with this case, hopefully in the next 12-15 shots 2 shots and clean it will quickly settle in like a good ppc would do
I’ll keep everyone posted on how things progress, thanks for the inputs guys

 

[SKWERLZ]

Yeah I calculated rpm’s at at 272k + give or

take, my main concern was and if anyone has had success with them at that speed, I’m a die hard short range br guy, never messed with big bore 7mm’s much. Iv shot and broke in a many Kriegers over the years and never seen one foul this much on one shot cleans lol, I’m assuming and hoping fouling right now is due to big HP so to speak with this case, hopefully in the next 12-15 shots 2 shots and clean it will quickly settle in like a good ppc would do
I’ll keep everyone posted on how things progress, thanks for the inputs guys

One thing I learned about bigger magnums is they need cleaning with less rounds than medium sized cases and shooting 50-100 rounds first of a moderate load before stepping on the gas seems to get the barrel settled in nicely.
I also use a cooler burning powder initially for those initial rounds.

 

[MTlager]

Are they for hunting ??? They will make a bowl of soup out of a critter at those speeds !!!

 

[SKWERLZ]

Are they for hunting ??? They will make a bowl of soup out of a critter at those speeds !!!

I’ve seen what 160-180 bullets in 28 nosler do to meat.
Can’t imagine another few 100’s of fps will do.

 

[Kurz]

hopefully in the next 12-15 shots 2 shots and clean it will quickly settle in like a good ppc would do

Just as an FYI with a little different idea about bullets and loads:

I built a 7mm-300 Norma Mag., not Improved, a few years ago. The 1:9" twist was and is still a standard twist rate generally for the 7mm. Currently the trend is for faster twist rates and the longer/heavier bullets for longer range shooting but the 1:9" still works well for most of the non-ELR hunting bullets.

Currently, I'm running the Badlands 140 gr. SBD2 bullets over Retumbo. At my elevation, these bullets as well as the 150 gr. remain stable and make use of the full BC.

Enjoy the process!

 

[Chris Roland]

Just as an FYI with a little different idea about bullets and loads:

I built a 7mm-300 Norma Mag., not Improved, a few years ago. The 1:9" twist was and is still a standard twist rate generally for the 7mm. Currently the trend is for faster twist rates and the longer/heavier bullets for longer range shooting but the 1:9" still works well for most of the non-ELR hunting bullets.

Currently, I'm running the Badlands 140 gr. SBD2 bullets over Retumbo. At my elevation, these bullets as well as the 150 gr. remain stable and make use of the full BC.

Enjoy the process!

Iv been trying the 175 elite hunters and RL33 with some decent results, not anything impressive with groups yet, gets good velocity, 92.2 gr is producing 3350fps in a 27” 9tw krieger, but I’m starting to think 3300+ is to much for this bullet. Maybe I need to try retumbo and go a bit faster in burn than Rl33, it seems like a really dirty burn also.