Need Help - 6BRA & IMR4166 Fire Forming Load

[Kimber.204]

Hello,

I picked up my first 6BRA barrel a week ago or so. I've got Peterson 6BR brass. I've got CCI 450's and plenty of 105/107/109 bullets. The only powder I have in mass is IMR 4166 Enduron. I'm looking for a suggestion of where to start.

I see data for the 6BR and 4166 in the Sierra app, but it stops below where most people use Varget.

Thanks in advance!
Ross

 

[newbieshooter]

I just FF'ed some 6BR Peterson brass the other week to 6BRAI using 29.5gr IMR4166 in my action/chamber. You may want to start with a few lower powder charges to ensure all is well in your setup.

I don't use CCI 450s to FF. I use a softer primer like a Fed205 (or CCI400) to FF.
Even with the slight crush fit of the 6BR cases in the 6BRAI barrel - I seat the bullets jammed...

ymmv.

 

[Bc'z]

I just FF'ed some 6BR Peterson brass the other week to 6BRAI using 29.5gr IMR4166 in my action/chamber. You may want to start with a few lower powder charges to ensure all is well in your setup.

I don't use CCI 450s to FF. I use a softer primer like a Fed205 (or CCI400) to FF.
Even with the slight crush fit of the 6BR cases in the 6BRAI barrel - I seat the bullets jammed...

ymmv.

View attachment 1270928

Will you be moving forward in load development with IMR4166?

 

[Kimber.204]

@newbieshooter I've got a few thousand 205's that I don't currently load in anything else...fireforming would be perfect for them.

@Bc'z Yes, I'm going to load IMR4166 I've only got a few pounds of Varget, but I've got an entire case of 4166. And my RL15 is reserved for the service rifle.

Thanks,
Ross

 

[newbieshooter]

Will you be moving forward in load development with IMR4166?

Probably so. Won't be able to get out for a bit to get started on load development.
Will keep ya updated.

 

[dnellans]

My fireforming load is:

29.5gr IMR 4166, Berger 109, CCI 450, Loaded to 2.380 COAL in blue box lapua BR.
From a well worn 26 inch fire forming barrel that goes 2757FPS.
I haven't found a reason to push it faster than that for fireforming, if you were using 105's to fireform you might be able to go a little higher, but again - why?

My recent direct experience is that 4166 is faster than varget but not as fast as 4895. I can't shoot 29.5gr of 4895 without pressure, but I certainly can Varget. 4166 is ok for accuracy in my full BRA load (will throw fliers that I know aren't me) but not as good as Varget, and runs about 20fps hotter than same weight varget load. So I'm using it for practice and fireforming now since i've got a lot of it but will stick to Varget for matches.

Hope that helps.

 

[KMart]

Just this week I did some load development in a 22-250 using 4166. Outstanding velocity and grouping.
One thing I noticed was after about 4 shots, the barrel was extremely hot for only 4 rounds. You may want to test 4-5 rounds to see how hot your barrel gets.
If you have a dedicated fire forming barrel, you should be good.

 

[Kimber.204]

I loaded up 25rounds this evening with five each of 27.5, 28.0, 28.5, 29.0, 29.5gr of IMR4166.
I'll check for pressure and load accordingly. Thanks for the feedback everyone!
I'll follow up with my results.

 

[Kimber.204]

All my loads above fully formed the case. 29.0 and 29.5 showed some mild signs of pressure. All loads showed similar accuracy (5 shot sub-moa). I'll probably load up some more at 28.5.
I also need to check my .220 Thunderbolt load. Right now I'm using 29.0gr of IMR4166 to push 88gr ELD-M at 3100fps. I'll bet I can get decent accuracy and velocity of 28.5 in my 220 Thunderbolt and then use the same powder measure setting for 220 TB and my 6BRA fireforming loads.

 

[Kimber.204]

A quick update. I ran through all my moly coated bullets for fireforming, and when I tried the 28.5gr load with the bare bullets I was getting a little pressure. So I backed it off to 28.2gr of IMR-4166 and I'm getting great accuracy (5shot - .375moa).

I also checked velocity with fire-formed brass, CCI-450's, and Berger 109's. 30.9gr IMR4166 gave me some mild signs of pressure and about 2900fps. I'm going to drop down to 30.6 or 30.7 and check accuracy.

This is my first BR length cartridge - but it seems like 2900 is respectable. My 6XC is only doing 2900 with 9gr more powder.
Thanks,
Ross