12.5 308 Aero?

KCode · Nov 11, 2024

Finishing up my 16 inch 308 build ans I already want a 12.5 for fun. From what I can see it would still send a 30cal projectile weighing 135gr around 2500fps. Would also probably do ok with subs.

What say you for SHTF type all purpose inside 200 yards?

hlee · Nov 11, 2024

I have a 16” 308 that I really like. But, I also have a 12” 6.5 Grendel that is pretty awesome. I think the weight/size savings of a small frame Grendel outweighs the potential performance gains of a 12” 308win- inside of 200 yards…

KCode · Nov 11, 2024

hlee said:
I have a 16” 308 that I really like. But, I also have a 12” 6.5 Grendel that is pretty awesome. I think the weight/size savings of a small frame Grendel outweighs the potential performance gains of a 12” 308win- inside of 200 yards…

The older I get the more I want to simplify my reloading. I thought about Grendel but decided to stick to 30cal and .223

Cascade Hemi · Nov 12, 2024

KCode said:
Finishing up my 16 inch 308 build ans I already want a 12.5 for fun. From what I can see it would still send a 30cal projectile weighing 135gr around 2500fps. Would also probably do ok with subs.

What say you for SHTF type all purpose inside 200 yards?

I'm loading 155gr and they go 2400fps. 135gr should get close to 2500 but I have not actually tried it myself.

Here is a post I made about a 12.5" 308 Win: https://www.snipershide.com/shootin...ild-info-picture-thread.6252642/post-11774240

Honestly, it's a toy. Even with a silencer it is super loud. Without a silencer you'll probably get hearing damage without doubling up hearing protection. With that said, there is no doubt a 12.5" 308 is lethal inside 200 yards.

LRRPF52 · Nov 12, 2024

If you shoot 125gr from the 12.5” .308, you’ll be doing 2700fps pretty easily. 125gr .308 bullets have really low BCs, but they are great for fast kills within 300yds. You have 125gr SST, 125gr TGK, 125gr TMK, 125gr Nosler BT, and 125gr Nosler Accubond options too.

135gr should do 2610fps.

147gr 2512fps

155gr 2450fps

KCode · Nov 13, 2024

So it really sounds like a 12.5 308 isn't THAT big of a dumb idea.

Only downside I can see is it would be loud. Also how hard would it be on a suppressor?

Overwatch260 · Nov 13, 2024

KCode said:
So it really sounds like a 12.5 308 isn't THAT big of a dumb idea.

Only downside I can see is it would be loud. Also how hard would it be on a suppressor?

I'm building a 13" 308 & been looking at suppressors for it... A few companies I've seen recommend for SBRs to run a HUB mount with a muzzle brake as a sort of "sacrificial baffle" so it isn't as hard on the actual blast baffle of the can itself. Makes sense to me so that's the way I'm planning to go.

Cascade Hemi · Nov 13, 2024

KCode said:
So it really sounds like a 12.5 308 isn't THAT big of a dumb idea.

Only downside I can see is it would be loud. Also how hard would it be on a suppressor?

50:50 mix of rad and dumb. Don't go shorter than MLGS. It's pretty handy compared to full size AR10s. It was a fun project.

The Recce7 handles it fine. The fireball without the can is 3' long.

KCode · Nov 13, 2024

Cascade Hemi said:
50:50 mix of rad and dumb. Don't go shorter than MLGS. It's pretty handy compared to full size AR10s. It was a fun project.

The Recce7 handles it fine. The fireball without the can is 3' long.

MLGS?

Edit: Medium length gas system. That took a minute

thedude824 · Nov 14, 2024

I’ve got a 13” SCAR 17. Fired it once without a can with double ear pro. There was nothing fun about it. Given I’ve done a few search warrants it’s definitely not what I would want. IMO it needs a can. If you are DI you’ll not only need a can rated for a short barrel, but the action will foul pretty quickly… unless you use a flow through can. IMO the only time a SBR 308 makes sense FOR ME is piston driven and flow through can. I use the HUXWRX Flow 762. I train with 147 grain handloads, but have stockpiles of handloads with 125 Controlled Chaos I bought on clearance and loads of 125 SST. I actually use that rifle on run and gun rifle nights. With the DiSCARder, HUXWRX, and Geissele trigger it’s really not much more cumbersome than the 556 rifles, but with superior ballistics… and no concerns or stoppages from fouling. It’s really an impressive system IMO. That’s my story

Cascade Hemi · Nov 14, 2024

thedude824 said:
If you are DI you’ll not only need a can rated for a short barrel, but the action will foul pretty quickly… unless you use a flow through can.

There is no practical difference between a 16" MLGS 308 Win and a 12.5" MLGS 308 Win with regards to operating system fouling. My experience actually says the lower dwell is easier on the operating system and stays locked longer.

As far as Di vs Piston with silencers. DI is simply more forgiving which is why flow through makes more sense with a large frame piston gun. It's been years but I've built SBR FAL's and they never really worked right transitioning between suppressed and unsupressed without custom drilled gas plugs and static ammunition selection. If OP were building a FAL or SCAR you'd be right on the money but with an AR10 you really just need an adjustable gas block or gas block drilled to size (.063 to .070 depending on silencer selection).

Dogtown · Nov 14, 2024

My favorite shorty .308...

KCode · Nov 14, 2024

Dogtown said:
My favorite shorty .308...

$2,000 for AN UPPER?! Gosh dang

Dogtown · Nov 14, 2024

Don't worry, prices will go down, just have faith...

thedude824 · Nov 14, 2024

Cascade Hemi said:
There is no practical difference between a 16" MLGS 308 Win and a 12.5" MLGS 308 Win with regards to operating system fouling. My experience actually says the lower dwell is easier on the operating system and stays locked longer.

As far as Di vs Piston with silencers. DI is simply more forgiving which is why flow through makes more sense with a large frame piston gun. It's been years but I've built SBR FAL's and they never really worked right transitioning between suppressed and unsupressed without custom drilled gas plugs and static ammunition selection. If OP were building a FAL or SCAR you'd be right on the money but with an AR10 you really just need an adjustable gas block or gas block drilled to size (.063 to .070 depending on silencer selection).

I have not shot an AR10 with a traditional baffle suppressor. Seeing the accumulation of fouling from AR15s with DI systems was all I needed to see. DI AR10s are notoriously difficult to get to function correctly (compared to small frame builds). A flow through can would likely mitigate a large portion of the issues, but a DI system will have more fouling regardless.
All I’m saying if you want a SHTF gun AND you plan on using a suppressor I would only grab a piston system

JR1200W3 · Nov 14, 2024

thedude824 said:
I have not shot an AR10 with a traditional baffle suppressor. Seeing the accumulation of fouling from AR15s with DI systems was all I needed to see. DI AR10s are notoriously difficult to get to function correctly (compared to small frame builds). A flow through can would likely mitigate a large portion of the issues, but a DI system will have more fouling regardless.
All I’m saying if you want a SHTF gun AND you plan on using a suppressor I would only grab a piston system

100% disagree. I've built 3 LFARs. Each one has been easy to build, gas, and shoot. Suppressed. Each rifle was gassed and running in 5 RDS.

hlee · Nov 15, 2024

JR1200W3 said:
100% disagree. I've built 3 LFARs. Each one has been easy to build, gas, and shoot. Suppressed. Each rifle was gassed and running in 5 RDS.

I’ve only built 2. One was built from parts that missed the boat to the Island of Misfit Toys. Both run (mostly) without issue. That second gun will choke if you monopod the magazine. But, there is no equivalent milspec for “AR10s” and guys think you have to be some gunsmith Yoda to produce a functional firearm.

Cascade Hemi · Nov 15, 2024

thedude824 said:
I have not shot an AR10 with a traditional baffle suppressor. Seeing the accumulation of fouling from AR15s with DI systems was all I needed to see. DI AR10s are notoriously difficult to get to function correctly (compared to small frame builds). A flow through can would likely mitigate a large portion of the issues, but a DI system will have more fouling regardless.
All I’m saying if you want a SHTF gun AND you plan on using a suppressor I would only grab a piston system

It seams like you're mixing two issues together. AR10's, assembled with correct parts, are not any more difficult to get running than AR15's. They are not AR15's though, and some of the AR15 rules of thumb do not necessarily hold true for AR10s (gas lengths for example). An AR10 doesn't need a flow through silencer any more, or less, than an AR15. I've shot suppressed AR15s well past 10k rounds without cleaning. AR15's and AR10's with retrofit pistons are a step backwards in terms of reliability, accuracy, and sound signature with silencers. As I mentioned earlier, DI guns are much more forgiving than piston systems.

If you care to look, I posted a link of a SBR AR10 I finished above. It is the actual receiver set and barrel length the OP is asking about. I included some notes about the operating system weight and gas port diameter. The barrel I used was a cut down barrel I had already fired well over 500 rounds through. All rounds were fired suppressed with a traditional silencer. There is no difference in the fouling between the 12.5" length and the 16" length. I used the same silencer in the picture for both lengths. Additionally, I have other LFAR's I have fired many thousands of rounds through. The fouling is not an issue, long or short. Frankly, modern surface treatments make cleaning the BCG effortless.

higginsworksforme · Nov 15, 2024

I have parts to build a 12.5" and I have no desire to shoot it without a silencer.

JR1200W3 · Nov 15, 2024

higginsworksforme said:
I have parts to build a 12.5" and I have no desire to shoot it without a silencer.

Would you settle for a suppressor?

higginsworksforme · Nov 15, 2024

It depends how autistic I'm feeling.

JR1200W3 · Nov 15, 2024

higginsworksforme said:
It depends how autistic I'm feeling.

Sorry to nitpick. I was afraid that a CNN reporter was trying to describe a suppressor.

higginsworksforme · Nov 15, 2024

I could probably become one. They have some openings lately.

hlee · Nov 15, 2024

Hiram Maxim’s original patent for a firearm muffler calls it a silencer. Silencer v suppressor is beyond pedantic. From that vantage point you can’t even see the clip v magazine debate.

JR1200W3 · Nov 15, 2024

hlee said:
Hiram Maxim’s original patent for a firearm muffler calls it a silencer. Silencer v suppressor is beyond pedantic. From that vantage point you can’t even see the clip v magazine debate.

Say clip MF'r. I dare you!

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