Retumbo or H50BMG in 32" 300 RUM?

[Tumbleweed]

Mighty fine shooting for a 10 power scope.

I'm sure it has something to do with mighty fine gunsmithing!

 

[Tumbleweed]

Well, I took her out this morning to verify my zero at 100 yards and ran 6 more through the chronograph just for a little more peace of mind and confirmation. Punched out the center of my dot at 100 and got an average on the chrono of 3225fps. The conditions were very favorable for chronographing too.
Shot to 727, 1000 and 1369 yards in pairs to get my drop confirmation on paper. 1369 is about as far as I can safely shoot out here. I am very pleased with the pairs and their vertical spread. Just a little tweaking with my Shooter program and I do believe I'm finally ready to go hunting with this rig!

The 727 yard pair measures 1.875" and the 1,369 yard pair measures 2.687"

 

[trebark]

The 727 yard pair measures 1.875" and the 1,369 yard pair measures 2.687"

Holy crap! that is awesome!

 

[MontanaRifleman]

That looks awesome! What temps are you shooting in?

 

[Tumbleweed]

That looks awesome! What temps are you shooting in?

My zero confirmation shots first thing this morning were around 45 degrees. It warmed up to about 65 degrees by the time I was shooting the longest shots. It's hard to tell if this powder is very temp sensitive as the ES numbers are really wide with the load. But, when I look at what it's doing on the target, who really cares?! I'm just using an average velocity of 3225, 45 degrees and 30.04 absolute for my zero and working off of that.

 

[MontanaRifleman]

I would say your chrony is a little flaky based on those groups. Time for a Magnetospeed

 

[Chopaka81]

I have had trouble with muzzle blast causing erratic chronograph readings when shooting my rummy. I had to move mine out to 20 ft from the muzzle. I have been shooting us869 in my rifle with 208gr amax. The ES is 8 to 10 fps. I have been unable to find powder(s) here in WA. Glad I'm sitting on a 8lb keg of 869. Wish I had the same for some other powders. Looks like your load is working out wonderfully for you at LR.

 

[Chopaka81]

Tumbleweed, do you mind saying who it was that built your rifle? Obviously he is a excellent gunsmith.

 

[Tumbleweed]

I have had trouble with muzzle blast causing erratic chronograph readings when shooting my rummy. I had to move mine out to 20 ft from the muzzle. I have been shooting us869 in my rifle with 208gr amax. The ES is 8 to 10 fps. I have been unable to find powder(s) here in WA. Glad I'm sitting on a 8lb keg of 869. Wish I had the same for some other powders. Looks like your load is working out wonderfully for you at LR.

I have been placing my chronograph out at 18-20 feet as well. Burning 101.5 grains of powder produces a nice muzzle blast.

 

[Tumbleweed]

Tumbleweed, do you mind saying who it was that built your rifle? Obviously he is a excellent gunsmith.

Don, I would be happy to. I have been planning this build in the back of my mind for over a year so I pretty well knew what I wanted to do when my other barrel finally gave up. We have a couple of local gunsmiths who are not qualified for this kind of build and the precision I wanted out of the weapon. I am a very anal person and I was looking for someone at least an anal as me when it came to the machining I hunted around for a while and went with Straight Shooter Supply out of North Bend, Oregon. I talked with Shawn several times over the phone and by email and it didn't take long to figure out that their level of precision, pride in their work and knowledge about LR rifles was higher than any I had experienced before. They have the finest in modern precision machinery to get the job done perfectly concentric and true. What I really appreciated was that Shawn was willing to do what I wanted to do and did not try to talk me out of what I had in mind. Shawn's son Brady did the work on my rifle as Shawn was away with some health challenges. I could not be more happy with the machining, attention to detail and overall performance of the weapon. I would recommend them to anyone without hesitation! You can find some pictures of the rifle here:

http://www.longrangehunting.com/forums/f19/full-custom-300-rum-completed-120045/

 

[Chopaka81]

Looking over your pics, You must be absolutely thrilled with your rifle and investment.
gun)

 

[Chris comer]

I just got my new full custom 300 Rum back from the gunsmith a few days ago. The barrel is a 9 twist Broughton 5C 32" finished length. I have a custom match diameter, very long throat. I am in the process of barrel break in and speed/pressure testing with Retumbo. I will start tuning for a load in the next several days. What I have discovered so far is that max load at a seating depth of 3.820" (to fit in my mag) is right at 94 grains of Retumbo. This produces 3130fps. I get the infamous Retumbo pressure spike at 95 grains. I am curious if I should steer towards H50BMG with this long barrel and throat. Does anyone have experience with this combo in extra long barrels? My gunsmith did comment that I may need H50BMG for the best velocity potential from 32". 3100fps with the 230 is very respectable but if H50BMG seems a better option I am willing to pick some up and try it. I did load two rounds up tonight with 93.5 grains of Retumbo at a seating depth of 3.950" to see what the pressure and velocity does compared to the deeper seating depth. Thanks

 

[Chris comer]

Don, I would be happy to. I have been planning this build in the back of my mind for over a year so I pretty well knew what I wanted to do when my other barrel finally gave up. We have a couple of local gunsmiths who are not qualified for this kind of build and the precision I wanted out of the weapon. I am a very anal person and I was looking for someone at least an anal as me when it came to the machining I hunted around for a while and went with Straight Shooter Supply out of North Bend, Oregon. I talked with Shawn several times over the phone and by email and it didn't take long to figure out that their level of precision, pride in their work and knowledge about LR rifles was higher than any I had experienced before. They have the finest in modern precision machinery to get the job done perfectly concentric and true. What I really appreciated was that Shawn was willing to do what I wanted to do and did not try to talk me out of what I had in mind. Shawn's son Brady did the work on my rifle as Shawn was away with some health challenges. I could not be more happy with the machining, attention to detail and overall performance of the weapon. I would recommend them to anyone without hesitation! You can find some pictures of the rifle here:

http://www.longrangehunting.com/forums/f19/full-custom-300-rum-completed-120045/

I shoot bmg 96 or 97 grains with 240 matchking

 

[Chris comer]

Velocity spreads right now are my main concern. I have not had time to dive into serious load development yet. I just know where pressure starts. If it likes 93-93.5 grains of Retumbo then I'll be running somewhere around 3065-3100fps. As the barrel wears in I'm sure this will increase as someone previously posted. My goal is low ES and no more than .25MOA vertical spread. I should be able to get this weapon to shoot sub .5MOA. I'll keep posting updates as development continues.