H4831SC burn rate/completion vs barrel length

[Lucky]

I have read all the previously relative threads without getting an answer to my specific question so here goes. In a 1:8 twist barrel how long would it have to be to get a relatively complete burn of say up to 48.5 grains of 4831sc behind a 130 gr bullet? That powder choice due to me having it and 4350 or really any powder of benefit being likely unavailable in any quantity for the foreseeable future. I am building a 6.5 cal gas gun and am wondering if i can get away with a 20 or 22' barrel and not just be lighting up the night sky with a lot of my powder. Build will utilize either an extended length or rifle gas tube and superlative adjustable block. Dont know why those details would matter to my question but just in case. Also just in case, the cartridge is 260 Improved. I know some might try to tell me that cartridge wont feed but i already have one on an AR platform that feeds flawlessly from magpul mags and shoots lights out. I don't want to build a creedmor for the same reasons im shooting 4831, I already have the 260 brass. Any input is appreciated and if i sound like i think i already know everything, i dont. Just anticipating some questions and tried to address them ahead of time.

An after thought, would running a suppressor have any impact? Thanks for any insight or opinions.

 

[6ShotsOr5?]

Obviously which 6.5 cartridge and specific bullet matter. I have found some decent loads for my 260 Rem using H4831 or H4831SC and Berger 130 AR Hyb bullets. My starting load was around 41 gr. Please consult reputable reloading data, YMMV.

Edit: my barrel is an 8 twist, 22”.

 

[Lucky]

Obviously which 6.5 cartridge and specific bullet matter. I have found some decent loads for my 260 Rem using H4831 or H4831SC and Berger 130 AR Hyb bullets. My starting load was around 41 gr. Please consult reputable reloading data, YMMV.

Thanks but my question is not about reloading for that case but rather about barrel length, burn rate of 4831. Will a load of possibly up to 48.5 grains behind a130gr bullet in a 20 inch barrel be only 40% utilized or 90% How much difference will a couple inches of length either way have on how efficiently the charge is utilized. At what length is that charge example fully utilized or burned etc. I am try to determine what length barrel to use. I know that obviously longer equals more fps but i assume that a majority of the potential pressure potential is within a certain length and after that the increase in fps per increase in length diminishes. That is an assumption and a question.

 

[6ShotsOr5?]

I think it’s a good burn, no muzzle flash noticed, but I use a suppressor so I’m not 100%.

 

[JimSC]

I used it in one .260 Rem barrel 29 inches 8 twist, the load was 44.1 - 44.5 with 140 gn SMK's and I never noticed any muzzle flash but then I never shot it in low light conditions either

 

[Lucky]

My SIL runs that powder in a 24 in 270 WSM without spewing flames.

That's encouraging. If I had access to H4350 or something with a comparable burn rate i wouldn't even worry about it but im not sure when or what availability of those are going to be going forward. My reason for wanting a shorter barrel is weight and a couple inches of barrel doesnt weigh that much anyway. Thank you for your response, it was the most helpful so far. I was not very good at explaining my self. I think i have been accused of that previously by wife or kids or employee or all of the above. Thanks again

 

[Mikemci]

Quickload will give you a % of powder burned, with different loads/barrel lengths.

 

[mdbruce]

You’re probably 95% burn by 14”
You would be surprised at how quickly you get to 95%, and how long it takes for a complete burn.

 

[Lucky]

You’re probably 95% burn by 14”
You would be surprised at how quickly you get to 95%, and how long it takes for a complete burn.

Thanks, and sorry for the delayed response. Good info.