6x45

[Varminterror]

Why mid length gas? Not AR smart...

Balance and port pressure.

My choice above between the SBR upper vs. a middy carbine is a trade between ultra-portability and improved operation and handling. If I’m carrying the length of a non-NFA upper, then I go all in and gain the forward balance improvement and improved gas system performance by loading towards the front.

 

[AJC1]

Balance and port pressure.

My choice above between the SBR upper vs. a middy carbine is a trade between ultra-portability and improved operation and handling. If I’m carrying the length of a non-NFA upper, then I go all in and gain the forward balance improvement and improved gas system performance by loading towards the front.

I get using pistol gas on sbrs and rifle gas on 24" but the middle ground is fuzzy. In a longer barrel a shorter gas length gives more pressure and with an adjustable gas block gives better tune ability????

 

[Varminterror]

I get using pistol gas on sbrs and rifle gas on 24" but the middle ground is fuzzy. In a longer barrel a shorter gas length gives more pressure and with an adjustable gas block gives better tune ability????

Gas port position along the bore dictates the bore-side pressure exposed to the port. We restrict pressure exposed on the tube side of the block by restricting the port diameter. Doing this at a higher pressure means we have to proportionately restrict the pressure MORE than we could at a lower bore pressure - in other words, this means the shorter gas systems behave in a way that they have more “reaction” to changes than longer systems.

Yes, in general, we can never “add pressure,” so we ensure a wider operable range if we have a big port at a short length with an AGB, but at the same time, we have the consequence of more reaction to variability. But for a 16-18” 6x45, I know I have all the gas I need with a large port diameter at midlength, and I can have wider operable range for a given AGB setting so I can run a faster powder under 50-60 class bullets and a slower powder under 80-90grn class bullets without as much fiddling with the block.

 

[KnightHawk]

For those playing the home game, remember, the 6x45 and 6x47 are VERY different rounds. The 6x45 is 2mm smaller in both directions - the 6x47 is based on the 6.5x47 case, nearly equivalent to a 6.5 Creedmoor, whereas 6x45 is a necked up 223rem. The larger will push a 100grn class bullet as fast or faster than the smaller can propel an 80grn class bullet.

The original 6x47 is a necked up 222 magnum case. The 6.5x47 was developed afterwards.
I’ve had a 6x47 built on a Sako mini action for over 40 years. The original 6x47 title may have been usurped, but…

 

[AJC1]

I'm still working on this project, xcaliber is the only barrel I've been able to locate. The 1:8 option r-5 rifling going 20" with a mid length gas with large port for adjustable gas block is the current plan. Pondering a medium heavy profile. Would a lighter profile longer barrel be better?

 

[AJC1]

I guess I better get this barrel thing figured out

 

[dfish1247]

Have an xp100 remage barrel in 6x45. And have a kimber super predator in 6x45. The xp has a 1:8 twist and handles 95gr hpbt no problem. I don’t know the twist on the kimber, but 90gr anything is its limit.

Velocity ain’t great due to low case capacity, but it’ll take pigs and deer just fine.

 

[AJC1]

Have an xp100 remage barrel in 6x45. And have a kimber super predator in 6x45. The xp has a 1:8 twist and handles 95gr hpbt no problem. I don’t know the twist on the kimber, but 90gr anything is its limit.

Velocity ain’t great due to low case capacity, but it’ll take pigs and deer just fine.

I was just looking at the 70 smk and 68 barts... should be quicker with 70 class....

 

[AJC1]

Tested the 75 grain Sierra varmitor and several groups were sub moa. Using aa-2015, and Remington br primers in pmc converted brass. 23.5 grains was gooder. Tried 68 grain match Burners today and every test was at or above moa. I'll run the same test again to be sure I wasn't having an off day, because honestly we have them. Sadly I want these to shoot because their so much cheaper, but that's not how things really work.....

 

[AJC1]

Put numbers to yesterday's targets and it was exactly as bad as I said. The only sub moa group was 23.5 grains which is a number that just keeps popping up in this loading, and shot the best with the 75 Sierra. Loaded up 40 at 23.5 and 10 testers at 24.3 because how could I not in 6mm.