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Posted: 6/10/2018 11:40:04 AM EDT
Does anyone have any personal experience working with an SBR Gas Gun in 308 as an intermediate range weapon?

Can anyone direct me to any resources that might be able to give me some constructive feedback on this topic.

Long story short, I'm putting a program together possibly utilizing this setup and i'm just trying to do some research.

tks in advance for any direction or input.
Link Posted: 6/10/2018 12:38:17 PM EDT
Depending how short your barrel is and your definition of intermediate I'm not sure if 500yds is accurately achievable. I haven't ran my 12.5" through a chrono yet but I'm thinking 2300fps with 168Amax.
Link Posted: 6/10/2018 1:48:45 PM EDT
Link Posted: 6/10/2018 2:26:00 PM EDT
closest I got was a 16" recce style .308. with pp2000mr shooting 168 amax's at 2600. I took that out to 800 on a 36" gong a few times with a 1.5-5 MK4.

I would like to revisit the idea one day with a gen 2 dpms pattern rifle with like a 13.7" pinned and welded or something of the sort. but I may be just as intrugued by doing a 6.5 creedmoor this go around than a .308.
Link Posted: 6/10/2018 4:36:46 PM EDT
I appreciate the replies.

Distances will max at 500. Platform will be a DI gun with a 1-8. This is a DMR role, engaging threats at both distance and close range.

I've also reached out to Hornady but haven't heard from them yet. Their 110 Amax is pushing about 3 times the energy as some of their 5.56 TAP but in the .30 cal bullet.
Link Posted: 6/10/2018 8:04:12 PM EDT
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Originally Posted By tbd1966:
I appreciate the replies.

Distances will max at 500. Platform will be a DI gun with a 1-8. This is a DMR role, engaging threats at both distance and close range.

I've also reached out to Hornady but haven't heard from them yet. Their 110 Amax is pushing about 3 times the energy as some of their 5.56 TAP but in the .30 cal bullet.
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I would shy away from that load personally. one thing i've learned over the years is when running short barrels BC is your friend. Velocity is a depreciating asset (to a great deal with sbr's) and BC like diamonds is forever. so in short with sbr's the velocity to BC relationship becomes very noteable as light for caliber loadings will lose velocity at a greater ratio than heavy for caliber. Secondly the lighter loads actually have more powder so when you have less time (ie. barrel length) to burn powder the excess and it becomes a fireball and greater concussion. also heavier for caliber bullets have higher sectional densities(aids in penetration), more mass (again aids in penetration and more bullet to potentially expand or if it yaws greater damage potential)

now I will say the lesser velocity may be a favorable thing with the 110gr in regards to terminal performance. it will be less likely to under penetrate with the lower velocities, however at distance the heavier loading's will excell in drop, drift ,and energy.
Link Posted: 6/10/2018 11:03:58 PM EDT
Am getting 2407 fps with 168 A-Max and 8208 with my 12.5 inch 308 AR.
Link Posted: 6/11/2018 1:46:11 AM EDT
What length barrel are we talking?

I’m in the process of either sbr’ing my 14.5 sr25 upper or pinning a mams ( pinning such an expensive upper kinda erks me) curious as well on good loadings from shorter 12.5-14.5 load data
Link Posted: 6/11/2018 7:22:41 PM EDT
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Originally Posted By Bearcat24:
Am getting 2407 fps with 168 A-Max and 8208 with my 12.5 inch 308 AR.
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That's plenty of velocity.

Biggest problem I've seen with these types of builds is that they are squirrely, and really want to get away from you.

This makes maintaining a sight picture very difficult.

168gr AMAX 2407fps

500yds 1600fps 955ft-lbs 4.8 mils drop 1.4 mils drift

These are best suppressed and tuned. If you tune them, you can reduce BCG reciprocating mass effect a little.

The suppressor helps eliminate muzzle blast and also weighs down the front to fight muzzle climb.

The will have more effective range if you have a very tight twist rate, like a 1:9 or tighter for a .308 Winchester.
Link Posted: 6/12/2018 3:45:34 PM EDT
My sandman-s should be here next month or so. Will find out if your right.
Link Posted: 6/12/2018 5:24:04 PM EDT
I have a 12.5 inch and 14.5” 7.62 from Adams Arms. Both are very easy to get hits with to 500.

Adams Can give you a lot of details.

The 14.5 is their new barrel config and a couple weeks ago I fired 3 of 4 groups (5shots) of 118LR at a measured sub (barely) MOA. 118LR is not known for that level of accuracy. But the rifle did it.

The light Amax are stompers under 100, past that the heavier bullets are better.
Link Posted: 6/24/2018 10:35:28 PM EDT
I have a 10.5" Craddock Precision .308 upper waiting on my stamp. If I can get hits on steel at 500 I will be very pleased. I plan to reasonably keep it within 300y.
Link Posted: 6/27/2018 8:47:07 AM EDT
[Last Edit: 6/27/2018 9:07:10 AM EDT by Pneumagger]
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Originally Posted By Bearcat24:
My sandman-s should be here next month or so. Will find out if your right.
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You're going to get MORE recoil with the suppressor versus an efficient brake mount. Both my 14.5" 308s have had noticeably more recoil with my 762SDN6 (a BEEFY can) versus just the brake mount alone. I learned this because ACOGs have very short eye relief... and well...

I'm putting together a 12.5 upper right now, and I'm not even sure I'm going to suppress it. Maybe just put a cookie cutter brake on it to see how flat & quick I can get it to shoot 110gr Amax and 155gr Amax.

Stick with 110gr Amax, Nato Ball, and 155gr Amax, or 155gr OTM/Palma. Anything else heavier is unnecessarily slow for the ranges you should be shooting a short 308 (<500yds). I don't think you need to really capitalize on the higher BCs the 165-180gr bullets offer if you're staying inside 500ish yards. Plus 155gr and 110gr will still be frag-nasty at CQB distances.
Link Posted: 6/27/2018 9:36:12 PM EDT
That sucks if recoil is going to be worst. Currently have a surefire SOCOM flash hider on it that I got fairly cheap. Nice thing about the 168 A-Max is you can buy it in bulk. So I shoot these along with 150 fmj that can also be purchased in bulk. I reload so have both with same POI @100 yards. Would be nice if Hornady sold the lighter bullets in bulk. Does get squirly trying a mag dump. Was going to share the can with my 10 inch 300 BO pistol. You wouldn’t happen to have any video shooting with and without the can?
Link Posted: 6/28/2018 12:01:44 AM EDT
[Last Edit: 6/28/2018 12:11:45 AM EDT by Pneumagger]
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Originally Posted By Bearcat24:
That sucks if recoil is going to be worst. Currently have a surefire SOCOM flash hider on it that I got fairly cheap. Nice thing about the 168 A-Max is you can buy it in bulk. So I shoot these along with 150 fmj that can also be purchased in bulk. I reload so have both with same POI @100 yards. Would be nice if Hornady sold the lighter bullets in bulk. Does get squirly trying a mag dump. Was going to share the can with my 10 inch 300 BO pistol. You wouldn’t happen to have any video shooting with and without the can?
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If you have a FH (not a brake), you don't need to worry. The recoil will still be slightly less WITH the silencer. But probably not too noticable unless doing back to back for comparison.

The high velocity gas is a significant contributor to the overall momentum transfer (recoil). Think about it; in a 5.56mm you've got a 55-75gr bullet propelled to nearly 3kfps BUT 20-something grains of powder that's travelling probably hypersonic. In a 308 it's 125-175gr projectile and 40-something grains of powder. That gas has alot of momentum in it's own right relative to the projectile! With a brake, most of that gas is thrown to the sides and cancels itself out. With a hider, most of the gas still goes straight ahead just like a bare muzzle. And with a silencer (regardless of the mount type inside of it) most all of the gas is ultimately getting thrown straight out the front meaning the reaction forces are still inline straight back. Sure, a silencer delays the release of gas, but it mostly all still goes out the front meaning the net momentum transfer is almost the same. So it will change the recoil impulse a little bit due to the delay... but the silencer isn't going to be WAY different from a hider or bare muzzle other than the added weight soaking up some recoil velocity. A silencer is generally much worse at recoil reduction than a good brake.

Like I said, I learned the hard way. I had a 51T AAC muzzle brake (a quite efficient brake) and an ACOG that I was shooting NTCH on a lightweight short 308. Those ACOGs only have but an inch or two of eye relief. I put the can on the first time and shot the gun NTCH with a relaxed grip in my hands and shoulder like normal... and I got intimate with the ACOG and charging handle real quick It confused me until I thought about it and it made sense from a physics standpoint. Now when shooting with the can on I pull back my face a half in ch more and hold on more tightly. On my 5.56mm AR15s have blackout hiders instead and I don't notice a difference in recoil other than the gun cycling harder due to more pressure.

Not my video:

Link Posted: 8/28/2018 9:32:26 AM EDT
I disagree that suppressors do little to mitigate recoil. I’m able to comfortably shoot my 8.5lb scoped bolt action 338 WM from the prone position with an F1 suppressor. I can’t say the same for unsuppressed. To me, my suppressed 338 feels like an unsuppressed 308.

Shooting my DPMS G2 308 16” with a suppressor keeps me on target significantly better vs non suppressed.

Also, keep in mind that using an effective brake in long shooting strings will effect the shooter on a short barrel. If we’re talking a 20” barrel or longer, then a brake is very effective. But in my experience, brakes on shorter barrels can induce a flinch or effect the shooter because of the large concussion being directed back at the shooter.

The gasses still exit the suppressor as stated, but at a delayed rate, thus changing the recoil pulse. You still get that initial sharp recoil pulse which wants to raise the muzzle, but it is significantly reduced.

After running brakes for many years, I just started into suppressors a couple of years ago. Given the choice, I will take the suppressor every time over a brake.
Link Posted: 8/29/2018 8:38:45 AM EDT
It’s not Opinion that cans don’t mitigate recoil impulse...there are multiple tests that show they don’t. Now, if you are going from a bare muzzle to a can, you will notice a difference. But a good brake to a can is working backwards recoil wise.

I don’t agree with your assertion about developing a flinch, but what do I know?
Link Posted: 8/29/2018 8:43:03 AM EDT
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Originally Posted By Bearcat24:
That sucks if recoil is going to be worst. Currently have a surefire SOCOM flash hider on it that I got fairly cheap. Nice thing about the 168 A-Max is you can buy it in bulk. So I shoot these along with 150 fmj that can also be purchased in bulk. I reload so have both with same POI @100 yards. Would be nice if Hornady sold the lighter bullets in bulk. Does get squirly trying a mag dump. Was going to share the can with my 10 inch 300 BO pistol. You wouldn’t happen to have any video shooting with and without the can?
View Quote
Bearcat, in good tests online the Surefire Comps have performed poorly compared to all others tested. Muzzle rise in particular is weak for them. A better brake at some point will help you a lot. I have at least three of them in my parts drawer now, they look good but don’t work.
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