6.5 PRC Retumbo

[Hondo1]

Looking for some first hand experience and data from those of you who have us Retumbo in the 6.5prc with 140-147’s. I know it’s not the streamline ideal powder for the prc but I have a lot of it and got tired of using RL26 on hot days.
Thanks in advance.

 

[straightshooter1]

Looking for some first hand experience and data from those of you who have us Retumbo in the 6.5prc with 140-147’s. I know it’s not the streamline ideal powder for the prc but I have a lot of it and got tired of using RL26 on hot days.
Thanks in advance.

Down here is AZ, I do a lot of "hot" day shooting, though I go out early enough to not shoot above 95°F (I just don't enjoy shooting in hotter temperatures ). I find that Retumbo works really well for me out of my PRC.

Berger 140 Hyb, COAL: 3.045; Powder: 58.0 grs Retumbo, Primer: CCI 200, MV: 3009 fps, Groups in 2's & 3's. (temperatures: 80-90°)

Sierra 142 SMK's, COAL: 2.957; Powder: 56.9 grs Retumbo, Primer: Fed 210, MV: 3019 fps, Groups in 2's & 3's. (temperatures: @80°)

Berger 153.5 Hyb, COAL: 2.969; Powder: 56.3 grs Retumbo, Primer: CCI 200, MV: 2906 fps, Groups in 2's (temperatures: Low 70°'s)

. . . all shot through 26" Preferred Barrel Blanks heavy barrel.

 

[Greenmoustache]

Looking for some first hand experience and data from those of you who have us Retumbo in the 6.5prc with 140-147’s. I know it’s not the streamline ideal powder for the prc but I have a lot of it and got tired of using RL26 on hot days.
Thanks in advance.

I use Retumbo with 147s, Nosler 150s, and Berger 153s. 26” Proof prefit on my TL3 and I push 147s about 3,050 with 57.5gr. If I’m running anything lighter than 147 I typically use RL 2X powders or IMR 7828. I’ve had some luck with H4350 as well but typically try to keep that for my CM.

 

[wade2big]

I have a tikka with a 24” factory 6.5 PRC barrel with roughly 120 rounds through it. Using Hornady brass, I can’t get enough Retumbo in the case with the bullet seated long to get any kind of velocity out of the thing. 61grs of Retumbo (over hornady max) with a 147gr eldm seated with the boat tail at the shoulder junction and I’m under 2900fps. Powder crunches when seating the bullet. The same charge with a 140gr seated the same way and I’m not any better. I couldn’t fit anymore if I wanted to.

Today I played with H1000 that I picked up and with a 140gr eldm I am nearing 3100fps with the bullet seated out as far as possible (end of bearing surface even with neck shoulder junction). Now I’m shooting a Tikka so I am loading above Hornady book but nowhere near what Berger lists for a 140gr bullet in 6.5 prc.

Retumbo will not work with Hornady brass and a factory Tikka barrel for some reason.

 

[straightshooter1]

I have a tikka with a 24” factory 6.5 PRC barrel with roughly 120 rounds through it. Using Hornady brass, I can’t get enough Retumbo in the case with the bullet seated long to get any kind of velocity out of the thing. 61grs of Retumbo (over hornady max) with a 147gr eldm seated with the boat tail at the shoulder junction and I’m under 2900fps. Powder crunches when seating the bullet. The same charge with a 140gr seated the same way and I’m not any better. I couldn’t fit anymore if I wanted to.

Today I played with H1000 that I picked up and with a 140gr eldm I am nearing 3100fps with the bullet seated out as far as possible (end of bearing surface even with neck shoulder junction). Now I’m shooting a Tikka so I am loading above Hornady book but nowhere near what Berger lists for a 140gr bullet in 6.5 prc.

Retumbo will not work with Hornady brass and a factory Tikka barrel for some reason.

What's your cartridge's COAL (like 2.995?) and how far are you off your lands?

With a COAL of 2.995 and 58.3 grs of Retumbo, it seems to me you should be able to get over 2900 fps. But that's getting some high pressure.

 

[wade2big]

What's your cartridge's COAL (like 2.995?) and how far are you off your lands?

With a COAL of 2.995 and 58.3 grs of Retumbo, it seems to me you should be able to get over 2900 fps. But that's getting some high pressure.

View attachment 8042365

Hornady shows 3050 out of a 26” with 58.5gr (max) at 2.950 coal so your data shows similar considering it’s for a 24”.

My COAL was 3.1 and some change. I don’t know exactly how far off the lands. I jam a round and back off .03” from that measurement then double check by chambering a dummy round to make sure I have no marks on the bullet after that. That’s where I start.

I’m thinking it’s a Tikka thing. Seems like it takes more powder to reach similar pressure and velocity as it would with other barrels. Factory ammunition is slower (lower pressure) by a decent margin as well in these barrels which adds credibility to this point. Every other cartridge I load for I am within book recommendations.

 

[Hondo1]

I ended up at 3030fps with Retumbo, pretty slow considering the 30” barrel. However it is very accurate. I saw 140fps more with RL26.

 

[Cascade Hemi]

Retumbo is generally too bulky for 6.5 PRC.

 

[Cascade Hemi]

I ended up at 3030fps with Retumbo, pretty slow considering the 30” barrel. However it is very accurate. I saw 140fps more with RL26.

This was my experience too. I had pressure signs with RL26 over 3200fps with 150 SMK. Retumbo was sub 3050 at 105% case capacity. 30" barrel.

 

[straightshooter1]

Hornady shows 3050 out of a 26” with 58.5gr (max) at 2.950 coal so your data shows similar considering it’s for a 24”.

My COAL was 3.1 and some change. I don’t know exactly how far off the lands. I jam a round and back off .03” from that measurement then double check by chambering a dummy round to make sure I have no marks on the bullet after that. That’s where I start.

I’m thinking it’s a Tikka thing. Seems like it takes more powder to reach similar pressure and velocity as it would with other barrels. Factory ammunition is slower (lower pressure) by a decent margin as well in these barrels which adds credibility to this point. Every other cartridge I load for I am within book recommendations.

I only asked about your jump to get an idea of how much room you might have to lengthen your COAL. Looks like you're loading pretty long at 3.100". For my Berger 140's I'm now loading at 3.085 COAL at .011 off my lands. For my Berger 153.5's they're at 3.057 COAL at .039 off the lands and I get 2944 fps with 57.2 grs of Retumbo out of a 26" barrel.

Keep in mind that different lot of powder will have different burn rates, so one is bound to see differences from what Hodgdon has on their load data. Based on my adjusted burn rate for Retumbo, you load configuration might look like this at a COAL of 3.100 (just to give you some perspective):

 

[straightshooter1]

Retumbo is generally too bulky for 6.5 PRC.

Hmmm??? It's been working really well for me with a number of the heavy 6.5 bullets.

 

[Cascade Hemi]

Hmmm??? It's been working really well for me with a number of the heavy 6.5 bullets.

Why is that surprising? H1000 is the standard for 6.5 PRC for 140gr to 150gr. Retumbo is the outlier and generally considered sub optimal.

 

[Hondo1]

Why is that surprising? H1000 is the standard for 6.5 PRC for 140gr to 150gr. Retumbo is the outlier and generally considered sub optimal.

Oddly enough Hornady shows it running faster than H1000 and on par with RL26

 

[Hondo1]

Retumbo that is.

 

[Cascade Hemi]

Oddly enough Hornady shows it running faster than H1000 and on par with RL26

It gets even less optimal as you reduce capacity, either with thicker brass or shorter COAL.

 

[Buckskin]

I've been running at just under mag length (2.960") and 56 gr H1000 with Hornady 153 A-Tips on a new 6.5 PRC (24") for brake in, going out at 2775, for kicks and since I have 8lbs of Retumbo vs 1 lb of H1000 ran same grains with Retumbo and same set up. Retumbo ran 24 ft/sec slower but touch more accurate. No pressure signs so plenty more if I want to go up, we will see but unless it's going to get me <.2 moa I doubt I will. Only have 80 rounds through it with new brass and haven't played with seating depth yet so very pleased so far.

Going to try 153.5 Bergers LRHTs as well since I just found +700 of them, hopefully they perform as well as the A-Tips.