Home Forums Hunting & Shooting Ask The Gunwriters RETUMBO: A VERY COOL BURN

OK, tonite was the first time I`ve tried this powder. Shot 77grns under a 162grn A-Max in the 7 Wby. 4 shots cronied:
3185
3198
3201
3183.....4 shot avge 3191..just over an inch at 100. Shot were fired slow, but with no attempt to allow barrel to cool. Air temp was 45". I placed my hand on the barrel just after the last shot, and the barrel was cool..I mean not hot or warm, just felt at ambient twmp..never had a powder do that.

Just to check, I fired three rounds, same bullet, 75grns RL-25. Shots cronied,
3099
3078
3089......for a 3088 average. The lower end of the barrel was, as expected from prior experience, very warm.

So, why did RETUMBO act as it did?? Anyone KNOW?

My first thought was that if heat is a factor in barrel erosion, I just may stick with RETUMBO.

But I would like to know why.

don't know about a cool burn. but retumbo and the the 300 rum are a match made in heaven

You might want to try rl22.

I have done 22. Did OK.

Lay your hand on the barrel next time you shoot it. How does it feel?

Haven't shot Retumbo, but there's certainly a very clear barrel heat difference between some powders. 748 vs. 4198 or N133 (or most others) in the .223 Rem is another example of what you've experienced. The difference can be quite dramatic. If I were you, and if it shot well, I'd stick w/Retumbo for that cart.

Don't know, but glad to see test results with explanation. I'm REALLY wanting to try some Retumbo in the 264 WinMag once it's built along side the IMR7828, and Magnum! Thanks for sharing!!!

I have some Reloader 25, but might just have to try some Retumbo in the 8mm Mag

Good Timing!!! I ran Retumbo over a chrony just this morning.

73.0 gr Retumbo gave me 3100 fps in a 7mm Rem Mag with the 160 Accubond. That same bullet with 70.0 RL25 clocked a 9 shot average of 3041.

68.0 gave me 3250 out of my 26" .264 Win Mag with 130 Accubonds while 68.0 Magnum gave me 3078 with the 140 Accubond.

What I would like you guys to do when shooting Retumbo is check your gun barrel by touching. Interesting to learn if the powder responds the same in your guns.

I have been running 73 grs of Retumbo and the 168 Berger for 3050 in the 7 mag with great accuracy, 3 inch average at 500, 3/4 at 100, been running it ever since all the temp sensitive hype on RL 19 and 22, although I havent found such results, but Reumbo is a great powder, 75.5 under the 140 TTSX shouts bug holes

Here it's good too in a 30-378. Will give it try in that one when I burn up my H870. My luck is I find something that works well and they quit making it.

CG:

Your post doesn't say, but is that the only rifle you shot during that session? And with only that powder?

- Tom

tjm....no, I also shot the three loads with RL-25, right after the Retumbo, so I could compair the heat generated by each, by touching the barrel after each string.

MZ5,

Of the powders that you mentioned (748, 4198, N133, most others) which were hot and which were "cold"?

I love RETUMBO, I shoot it in my 30-378. but havent noticed the "cool". 113 grains warms the barrel right up!

I need to try it in my 7 WBY..RL22 has been so good I havent bothered yet.

Wismon, 748 heats my 223 barrel significantly less than either 4198 or N133. 4198 and N133 are close enough that I wouldn't claim a heat difference between the two.

I've been useing Retumbo under 200's in my 300 RUM for a few years now, at 95.5 gr. a pop I burn through a pound pretty fast.
When ever I shoot from a bench i always set up the crony. I havent seen any variation from Temps. or lot to lot variations at all.

Interesting. Either 748 or BLC2 was advertised as burning cooler than ohter powders which is why they claimed the military used it for machine gun ammo. I just assumed it was marketing hype...but maybe there's something to it?

CG-

I modeled your loads with QuickLoad and assumed a 26 inch barrel.

Remember, in this case more pressure=heat higher temp (see Ken Howells discussions).

69179 psi!!!!


57891 psi


Sleep well.