6x45 velocity per inch/ barrel length questions

D

Deadeye260

New member
Hi ,
I have a 20"AR Stoner rifle gas 6x45, I want to cut down to 16" and have it threaded 5/8 for my can. It's a shooter for sure but has been benched the last couple of years due to the length and being 9/16x24 threaded. I have a good load worked up for it using the 85gr SGK. So my questions are. Will this barrel run ok at 16in suppressed with the rifle length gas system? How much velocity will I lose by dropping back 4in? I'm thinking around 80/100fps. And my last question is how fast are you guys running the 70gr Nosler Ballistic Tips in 16in 6x45 AR15s?
I would like to use this 16in 6x45 for Mostly coyotes and probably some hogs as well.
 
I currently use a suppressed 16 inch 6x45 ar15 for coyotes. i was using 70 grain ballistic tips before, but was unable to find a good powder to get me the velocity i wanted. I am now using 55 grain ballistic tips with AA2200 and the velocity is great (i got up to 3300 fps, but accuracy was best at 3220). You may have better luck with the 70s than i did, but if you are open to trying lighter weight bullets, AA2200 produces very good velocity.
 
What length gas system are you using?
What's the twist on your barrel?
I like the adjustable gas block idea!
My barrel is a 5r with 1-8 twist. I was wanting to run a heavier bullet. But if all else fails I'll give the 55-60gr bullets a try. I'd like to run my current load with the 85gr SGK but I'm not sure itll open up at the lower speed. Currently its exiting the muzzle around 2830-2850 fps.
 
I had a 24" with a rifle length. When i cut it down i went to 18" just to be safe. Personally i would do that length again. So my recommendation is to go 18. Btw, imo, if ur dead set on doing a 16" personally i would just buy a 16 and use it. If you don't like it you could always sell it and go back to the 20 in but personally I don't think I would cut down that short to 16" with a rifle length gas system. I think it's just risking it too much
 
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I wasnt dead set on 16 but it would look better and maneuver a lil better with the can on it than the 18 or 20. But I dont want to give up alot of velocity either. I was looking at the dissipator style rifles and I was thinking it might be similar shooting if knocked down to 16in. What kind of velocity did you lose when you cut yours back 20/25 fps per inch?
 
my barrel is a mid length gas system with a 1:10 twist rate (from x-caliber barrels). I haven't ever had a rifle length gas system on a 16 inch barrel but with an adjustable gas block you could probably tune it in and make it work just fine.
 
Originally Posted By: JDF_GSPmy barrel is a mid length gas system with a 1:10 twist rate (from x-caliber barrels). I haven't ever had a rifle length gas system on a 16 inch barrel but with an adjustable gas block you could probably tune it in and make it work just fine.

I'm not familiar with 6x45 really but I suspect that 16" RLGS would work ok as long as you only plan to shoot suppressed, the suppressor will add plenty of back pressure to make things work. Shooting unsuppressed sucks anyway. A buddy and I have 11.5" midlength gas systems and they run just fine suppressed with an adj gas block. Extremely soft shooting also, softest rifle I own.
You will also appreciate the handling of the shorter rifle with a can hanging off of it.
 
I'm running a 6x45 in a 16" barrel. Currently I'm getting 2850fps with 58 vmaxes. I would imagine a little heavier bullet wouldn't lose too much as long as you get full burn in the barrel.
 
I shoot 70 gr Speer TNTs out of my two 6x45s (18” and a 12.5” SBR). Same exact load of 26.8gr Benchmark shoots 2944 FPS
out of the 18” BHW barrel and 2700 FPS out of the 12.5” BHW barrel in about 40* weather at approx 1880 ft above sea level.

The 70 gr Nosler BT out of the 18” with 27gr Benchmark was 2950fps.

Agree with the above, if you want rifle length gas system in a 16” barrel you better get an adjustable gas block.
 
Wouldn't the adjustable gas block only help in dialing down the gas? 16" with rifle gas would already lean to under gassed but can be overcome with a larger gas port in the barrel if needed.
 
Pharmer Jon that's pretty encouraging to hear I was hoping to run the 70gr NBT at 2800 out of the 16in tube.
Have any of you guys shooting 16in 6x45 chrony'd some 85gr SGK or similar?
 
I was getting 2975 FPS out of my 20” with 70 grain SBKs and H335. I had it chopped to 18” for ease of carry and haven’t shot through a chrony yet. It has a rifle length gas system with adjustable gas block and functions perfectly at 18”. Check out the sticky with the 6x45 load data for some good information.
 
Originally Posted By: desertcjWouldn't the adjustable gas block only help in dialing down the gas? 16" with rifle gas would already lean to under gassed but can be overcome with a larger gas port in the barrel if needed.

Yes, the adj block only helps with overgassed guns but almost all AR's are overgassed to avoid reliablity issues with weak ammo. Add a can to it and it only gets worse because they all increase back pressure to some degree. You can certainly try it without the adj block to see how it runs. Cutting the gas down will slow the bolt velocity (softer shooting) and cut down some of the port noise which will make it quieter to the shooter in my experience. In some cases it can make a pretty noticable difference.
 
Ok guys so I got the barrel cut back to 17.5" and threaded 5x8!
Tried out some of my old go to loads looks like I lost around 54fps. Which I'm not going to lose any sleep over! 85gr SGK @2800fps should work fine for what I do.
The rifle runs like a champ suppressed and throws all the brass in a nice consistent pile! The stick is a lil longer than I'd like it to be but I'm shooting off of a tripod so it's really not that big of a deal.
 
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