retumbo vs n570 in 300 rum testing

[Benchrest Braxton]

I sold my retumbo stockpile and switched to to N570!!

backstory time.

I purchased my custom BAT 300 rum from Greg at SPR. It was one of his older personal rifles. It is a BAT model M, joel russo mbr clone from curly maple, rock creek 34" 10 twist 1.350" cylinder 238 freebore 340 neck. I had it threaded for a suppressor and put my NXS 12-42 on top.

WARNING: DO NOT USE MY LOAD DATA FOR ANYTHING BUT COMPARATIVE PURPOSES.

When I bought the rifle he included load data for his 230 berger hybrid load. It was 92 grains of retumbo with bullets 50 thou off the lands for 3,150 fps in remington brass.

Not long after the 230 hybrids became onobtanium. I decided to give the hornady 225 eld match a try loaded to the same specs (92 retumbo/50 thou jump). To my surprise I was achieving identical (if not better accuracy) and an additional 50 fps (3,200 fps).

As good as this load shot (1/4-1/2 moa precision with ease). This was a 100% max load, clickers on bolt lift and flattened primers.

After seeing some of the other users success with N570 on this forum, I decided to give it a shot. With my longer barrel running the heavier bullets, it made alot of sense. My goal was to achieve the same velocity, precision, and sd as the retumbo load, but without the pressure.

Finally got a chance today to get out and shoot a velocity ladder, 89.0 through 94.0 grains with the 225 eld match.

89.0 grains - 3,087 fps
90.0 grains - 3,115 fps
91.0 grains - 3,150 fps
92.0 grains - 3,189 fps
93.0 grains - 3,190 fps
94.0 grains - 3,233 fps

all bullets went into a sub 2" group at 310 yards.

even at the highest load of 94.0 grains, the difference from the retumbo load was astounding. Clicker was now gone, primer looks great, and the rifle seemed to recoil smoother.

There is no doubt in my mind I could achieve 3,300 fps with this powder if I wanted to. Please see the picture below of the 94.0 n570 load vs the 92.0 retumbo case.

Needless to say I am a happy camper and very glad I decided to give this powder a try. I'd suggest anyone running 220+ grain bullets in your 300 rum a hard look at this powder.

 

[Wedgy]

N570 is one of the hottest burning magnum powders and will erode the throat 30-40% faster than Retumbo or H1000, speed comes at a price. Man the is really smokin' !!
I run my RUMs closer to 3,000fps with a 28" tube and 230's RP brass. Might try some ADG if I ever run out of RP.

 

[Benchrest Braxton]

N570 is one of the hottest burning magnum powders and will erode the throat 30-40% faster than Retumbo or H1000, speed comes at a price. Man the is really smokin' !!
I run my RUMs closer to 3,000fps with a 28" tube and 230's RP brass. Might try some ADG if I ever run out of RP.

I bet the erosion figures are less when you are using less pressure for the velocity like in my case.

figure - i was running 70kpsi in my retumbo load and now 60 kpsi in my n570 load.

i might post some load data in a few days to find out what max is in this gun. i may also try some 24n41 as well just out of curiosity (as there is still a good bit of room in the case with n570).

i also have a bunch of peterson and adg to tap in to once this remington brass craps out.

 

[Veteran]

I bet the erosion figures are less when you are using less pressure for the velocity like in my case.

figure - i was running 70kpsi in my retumbo load and now 60 kpsi in my n570 load.

i might post some load data in a few days to find out what max is in this gun. i may also try some 24n41 as well just out of curiosity (as there is still a good bit of room in the case with n570).

i also have a bunch of peterson and adg to tap in to once this remington brass craps out.

It just makes sense that you got more velocity from N570 than Retumbo with less pressure. Its a slower burn rate powder than Retumbo.

My numerical burn rate chart shows this below. You might try RL33 for grins too.

H1000		0.366​
Ramshot Mag	0.345​
RL26		0.3397​
Acc Magpro	0.3342​
Retumbo		0.337​
N565		0.3109​
IMR8133		0.3​
N568		0.3​
Ramshot LRT	0.285​
N570		0.277​
RL33		0.267​
US 869		0.2735​
RL 50		0.217​

 

[Benchrest Braxton]

It just makes sense that you got more velocity from N570 than Retumbo with less pressure. Its a slower burn rate powder than Retumbo.

My numerical burn rate chart shows this below. You might try RL33 for grins too.

H1000		0.366​
Ramshot Mag	0.345​
RL26		0.3397​
Acc Magpro	0.3342​
Retumbo		0.337​
N565		0.3109​
IMR8133		0.3​
N568		0.3​
Ramshot LRT	0.285​
N570		0.277​
RL33		0.267​
US 869		0.2735​
RL 50		0.217​

i am swapping over to all viht powders, i am not happy with hodgdons price gouging/monopolizing tactics. alliant powders are just as bad as hodgdon and availability is even worse.

if anyone lives near central pa i got a bunch of hodgdon and ramshot powders i'll sell ya cheap lol

the next powder i may try and play with for grins is LRT or 24n41

 

[MagnumManiac]

It has been tested and proven that pressure is NOT what erodes throats, it is a 2 factor proposition, heat and time of burn and amount of scrubbing from unburned powder…so your theory regarding less pressure is going to save your barrel is moot.
I have a very high intensity wildcat cartridge that normally only works to it's best with powders like US 869, RL33 (bad on throats) H50BMG and 24n41. Retumbo works, but is slow in velocity. At 118-125g of powder per shot, at just under 900 rounds, the throat is done again, this was the third set-back and re-chamber, lost over an inch in barrel length. I also found double base powders of the ball type to be nicer on throats, but the supply of US869 dried up here.

Cheers.

 

[Benchrest Braxton]

It has been tested and proven that pressure is NOT what erodes throats, it is a 2 factor proposition, heat and time of burn and amount of scrubbing from unburned powder…so your theory regarding less pressure is going to save your barrel is moot.
I have a very high intensity wildcat cartridge that normally only works to it's best with powders like US 869, RL33 (bad on throats) H50BMG and 24n41. Retumbo works, but is slow in velocity. At 118-125g of powder per shot, at just under 900 rounds, the throat is done again, this was the third set-back and re-chamber, lost over an inch in barrel length. I also found double base powders of the ball type to be nicer on throats, but the supply of US869 dried up here.

Cheers.

is this mark? from mark and sam?

thanks for the input sir, your experience means alot!

 

[Blackdirt Cowboy]

I second veterans suggestion of re33. That's what I use in my factory sendero 300 rum. With 230 grain bergers, it's money. Fast and deadly accurate.

 

[Benchrest Braxton]

I second veterans suggestion of re33. That's what I use in my factory sendero 300 rum. With 230 grain bergers, it's money. Fast and deadly accurate.

as great as re33 might be, its non existent in bulk form unless you are already stocked up pre-covid.

I just picked up 2 8lb jugs of n570 and didn't have to rush to order it.

once i find max with n570 im going to see if 24n41 has anything to offer with the heavies.

i do have a friend sitting on a 1lb can of re-33 that i could probably persuade to let me buy to test with

 

[ARlife4me]

Pressure means nothing as barrel life goes under the standard max of 65k. Duration means a lot. Add flame temp to duration then it'll equal less barrel life. Hard to say how much less as no one can truly state. 570 will give you the highest velocity in most cartridges it's compatible for. LRT, 33, 7828ssc are all a close 2nd and 3rd's. Retumbo would be up there in the top 3, but the availability is less desirable. H1000 is around, but prices are horrible that I've seen. I bought some LRT for my 264wm, but will be trying it in 300wm and 338lm also along with 570, 568, 565, retumbo, h1000, 7828ssc, h4831sc, 33 and magpro.

 

[MagnumManiac]

is this mark? from mark and sam?

thanks for the input sir, your experience means alot!

No, sorry not me. I got into shooting and designing ELR cartridges about 18 years ago for 2,000 metre comps. I based my cartridges on the 416 Rigby case, improved with varying shoulder angles, this was before the 338 Lapua, 33XC and the like. The 505 Gibbs case was considered, but finding an action suitable at the time was just too hard.

Cheers.

 

[Benchrest Braxton]

No, sorry not me. I got into shooting and designing ELR cartridges about 18 years ago for 2,000 metre comps. I based my cartridges on the 416 Rigby case, improved with varying shoulder angles, this was before the 338 Lapua, 33XC and the like. The 505 Gibbs case was considered, but finding an action suitable at the time was just too hard.

Cheers.

you know who that is right? you and him seem to have alot in common (shooting, aus, engine building)

 

[MagnumManiac]

you know who that is right? you and him seem to have alot in common (shooting, aus, engine building)

Yes, I know Mark well enough, he's in WA, so a long way from me.

Cheers.

 

[Longtine88]

I sold my retumbo stockpile and switched to to N570!!

backstory time.

I purchased my custom BAT 300 rum from Greg at SPR. It was one of his older personal rifles. It is a BAT model M, joel russo mbr clone from curly maple, rock creek 34" 10 twist 1.350" cylinder 238 freebore 340 neck. I had it threaded for a suppressor and put my NXS 12-42 on top.

WARNING: DO NOT USE MY LOAD DATA FOR ANYTHING BUT COMPARATIVE PURPOSES.

When I bought the rifle he included load data for his 230 berger hybrid load. It was 92 grains of retumbo with bullets 50 thou off the lands for 3,150 fps in remington brass.

Not long after the 230 hybrids became onobtanium. I decided to give the hornady 225 eld match a try loaded to the same specs (92 retumbo/50 thou jump). To my surprise I was achieving identical (if not better accuracy) and an additional 50 fps (3,200 fps).

As good as this load shot (1/4-1/2 moa precision with ease). This was a 100% max load, clickers on bolt lift and flattened primers.

After seeing some of the other users success with N570 on this forum, I decided to give it a shot. With my longer barrel running the heavier bullets, it made alot of sense. My goal was to achieve the same velocity, precision, and sd as the retumbo load, but without the pressure.

Finally got a chance today to get out and shoot a velocity ladder, 89.0 through 94.0 grains with the 225 eld match.

89.0 grains - 3,087 fps
90.0 grains - 3,115 fps
91.0 grains - 3,150 fps
92.0 grains - 3,189 fps
93.0 grains - 3,190 fps
94.0 grains - 3,233 fps

all bullets went into a sub 2" group at 310 yards.

even at the highest load of 94.0 grains, the difference from the retumbo load was astounding. Clicker was now gone, primer looks great, and the rifle seemed to recoil smoother.

There is no doubt in my mind I could achieve 3,300 fps with this powder if I wanted to. Please see the picture below of the 94.0 n570 load vs the 92.0 retumbo case.

Needless to say I am a happy camper and very glad I decided to give this powder a try. I'd suggest anyone running 220+ grain bullets in your 300 rum a hard look at this powder.

I found the same thing. Until I got to the second firing. Pressure showed up and backed down a little over a grain.