Home Forums Hunting & Shooting Custom Rifles & Wildcats 6mm Weatherby RPM 3600fps, 115gr Berger (pic)

I finally got a chance to toss some 6 RPM rounds over the chrono tonight. Best powder tested so far was VV 24N41. 72 grains tossed the 115 Berger out at 3600+fps.
Krieger 1:7 twist, 26.5" long.

Here are a few other powders I tried.

68gr H50BMG 3250fps
71.5gr US869 3500fps
73gr VV 20N29 3350fps

So lets get the "Barrel Burner" comments out of the way now. No need for that. Barrel burner, chamber 3 barrels at a time, the barrel will be worn out before you develop a load, throat eater, horribly inefficient, what can that do that my 6mm Creedmoor can't, solution looking for a problem......and the Campfire knuckle dragging drivel will go on and on. If that is all you have to say, just move along.

Tony Rumore
Tromix

pic left to right, .243, 240 Weatherby, 243 Catbird, 6mm Weatherby RPM

Edited to add - no accuracy testing. I was firing it on the 50 foot Tromix indoor range.

Nice. How fast you think it would push an 80 grain TTSX? That could be fun

Unfortunately, those bullets are at my other shop. The lightest I have on hand at the moment are 90gr ELD-X. They flew 3720fps with that same 72gr 24N41 load.
I imagine, I would need to go to US869 for the lighter bullets. There is more capacity with that powder than 24N41 which is about maxed out at 72gr.

I currently shoot the 85gr TSX from the Catbird at 3850fps with a 27" barrel (Sako AIII). My ranch is mostly timber, so the shots are not very long. That 85gr Barnes knocks the chit out of whatever it hits at that speed.

Tony

Might take a look at the 115gr nose ring dtac. I find this to be the most interesting Weatherby cartridge. A 108 or 109eldm would be nice too.

If only they made a 120gr eldm or tmk.

I tried the 108 ELD-M, but that bullet needs to be seated quite a bit deeper than the Bergers, at least with the current lead/throat in my barrel.
72gr of 24N41 launched it at 3590fps. No faster than the 115 Berger....but who really cares? It's going fast enough. I will probably throttle all the loads back for hunting anyway. No need to shorten brass life for a hundred fps.

Tony

Ross Seyfried and I did the 6mm Mach IV back in the late 80s.

A bit more powder capacity.

Would not recomend shooting game with the Berger at those speeds.

Have fun.

Are you necking down the 6.5 rpm brass in one step? Or incremental?

I can do it in one step, but I don't. I made a neck sizing die that brings it down to about 25 caliber first, then I made another die to go to 6mm. You can't use a .243 WSSM die to neck it down. The shoulder angle is wrong, so you only end up sizing the neck about half way down before the shoulder bottoms out. Ask me how I know. lol.

If anyone wants to make up a 6 RPM, you can get the reamer from JGS. Any .473" bolt face long action can run it and you will have plenty of head room to dangle the bullet WAY out off the case neck like the cool kids.

Tony Rumore
Tromix

I'd be curious what kind of accuracy that thing will produce once you get it figured out.
What kind of groups are you getting with the catbird with the 85g TTX?
As stated previously I'd avoid any projectile with lead in it for deer at those speeds......
Interesting project


dave

About an inch at 100 yards. The twist in the barrel is really too slow (1:12) to stabilize it past about 100 yards.
I need to make another barrel for that gun, but the 1:12 Hart blank happened to be on hand at the time.

Tony Rumore
Tromix

Welp cut that barrel down to 18.5” put a suppressor on it, stuff it in a hard case with a foam cut out for the rifle, scope, box of 20 and a flat brimmer hat with your choice of optics patch on the hat and call yourself ready. What else you got in the works?

Honestly that’s cool though. Always like seeing peoples projects.
S.

What action are you using and what scope do you have mounted on it?

Man, now that is a screamer. Cool project.

Your chronograph readings are suspect.

If it's truly stable at 100 yards then stability will increase farther out.

Isn't the catbird a Kenny Jarrett creation?
dave

I think you’re correct. Isn’t it the 280 Ackley necked to 6mm?

I had to read up on the RPM.
Interesting.
Does your reamer have the weatherby freebore?
Or did you shorten it?
dave

Kenny Jarrett's site says the Catbird is a 270 parent case with a 35 degree shoulder. So not a great deal of case capacity difference than a necked down 280 Ackley.

I did not shorten the lead or throat. With the Berger 115 seated to the base of the neck, it is just off the lands.
With the 108 ELD-M, I have to seat the bullet down below the base of the neck or the bullet gets jammed in the throat.

Tony