Red Dot/Holographic Site discussion

[Former11B]

Man, there are so many variables at work i think it'd be difficult to definitively say a 10.5" will run better suppressed than an 11.5 or vice versa. The additional dwell time of the 11.5 allows chamber pressure to drop a bit more before the round is extracted, allowing for more reliable extraction. But increased dwell time is only good to a certain point. Excessive dwell time can effectively over-gas the gun (this is why mid length gas systems are favored on 16" barrels as opposed to carbine length, not to say that a carbine gas system on a 16" barrel can't be made to function reliably). Adding a can to either a 10.5" or 11.5" barrel will likely result in the gun being overgassed, as the back pressure of the suppressor effectively increases the dwell time (although actual dwell time remains the same in each respective barrel, since the bullet still leaves the bore at the same time it would if shot unsuppressed). Specifics of gas port size, how much back pressure a specific can will add, etc. all play a part. The 11.5 has a higher dwell time than a 10.5, so on paper, with the same can and same relatively sized gas port (i.e. the smallest sized gas port for each barrel that would allow reliable function with nato pressure ammo) in both barrels, the 10.5 would probably be less overgassed than the 11.5. That said, both barrel lengths can be run quite reliably suppressed by running an adjustable gas block, and/or different buffer/spring combos. I don't recall the numbers, but i remember reading that the 10.3" barrels Daniel Defense sells to the general public have a larger gas port than the ones they sell to the military, the logic being that the .mil will always run nato pressure ammo (and frequently run suppressed), where John Q. Public will run everything from Tula .223 to quality 5.56x45 nato. With the smaller gas port of the .mil 10.3, the guy running Tula would find his gun undergassed and have cycling issues. Throw a can on that same gun with the same ammo, and it'd probably cycle fine. Conversely, the commercial spec 10.3" DD barrel will cycle fine with all types of ammo (i've found mine runs best with an H2 buffer using nato pressure ammo), but add a can and you'll probably find you need to run a heavier buffer/spring combo to compensate for the extra pressure in the gas system. Now, on the 11.5" barrel, the gas port could probably be made larger to allow the end user to shoot a variety of different pressure ammo, and the increased dwell time wouldn't make the gun as sensitive to extraction issues associated with an over gassed gun.

I'm no expert, and it's been a while since i stayed in a Holiday Inn Express, so please correct me if my thinking is completely wrong.

I would rather add an adjustable gas block than add a heavier buffer and spring, even though that is the cost effective way. The heavier buffer will slow the carrier speed but you still have a lot of gas dumping out of the ejection port/in your face and you'll have an increased recoil impulse. Having the ability to tune the gas so it runs properly despite the gas port size in the barrel is the way to go.

You are right, the heavier buffer will help compensate for the suppressor, but it causes some other side effects that aren't ideal.

[DutyUse]

I'm running a syrac adj on my 10.5 ballistic advantage barreled upper & a regular BCM gas block on my 11.5 BCM BFH upper. Both run an H buffer and both have run well thus far unsuppressed.

However neither has more then 200 rounds, as I'm not a huge fan of "pistol" kits and I'm still waiting on stamp return.

[Deadwing]

I would rather add an adjustable gas block than add a heavier buffer and spring, even though that is the cost effective way. The heavier buffer will slow the carrier speed but you still have a lot of gas dumping out of the ejection port/in your face and you'll have an increased recoil impulse. Having the ability to tune the gas so it runs properly despite the gas port size in the barrel is the way to go.

You are right, the heavier buffer will help compensate for the suppressor, but it causes some other side effects that aren't ideal.

I agree. The only SBR I own that gets run suppressed regularly is my Noveske 10.5" with their Switchblock. It'll run suppressed in normal, but with way more gas to the face than on the suppressed setting. This gun also came from the factory with an H2 buffer. Heavier buffers also help with things such as bolt bounce. An H2 buffer weighs 5.3oz if memory serves, and a rifle buffer weighs what, 5.9oz or something?. With that in mind, I like to run as heavy a buffer as I can without short stroking the gun and still getting the bolt to hold open on an empty mag.

[tact]

I think people overthink this crap way too much, and add unnecessary accessories/parts trying to mitigate a problem that doesn't or shouldn't exist in the first place.

[UWone77]

I think people overthink this crap way too much, and add unnecessary accessories/parts trying to mitigate a problem that doesn't or shouldn't exist in the first place.

I'm pretty much right there with you on this one.

I have a lot of SBR uppers. 99% of them run well with an H2 buffer, nothing else. I have switchblocks on several, but those are basically the only adjustable gas blocks I run.

[DutyUse]

I wish I woulda held out for a Noveske switchblock barrel. They endorse syrac but it's kind of a pita

[SINNER]

I much rather tune a rifle with buffers than an adjustable gas block. They all pretty much suck. If you reduce the port size they foul faster. Some so fast it will cause issues in a days shooting.

[alamo5000]

Lively debate going on here.

At what point do these 'issues' sort of no longer become 'issues'? Obviously it has an effect on shorter barrels more than anything...seemingly the shorter you go the more potential for problems.

Based on the discussion here I could say that it sounds like once you go sub-11 inches that's where it might get complicated.

That said with an 11.5 or a 12.5 what are the odds of having a problem?

[gatordev]

Lively debate going on here.

At what point do these 'issues' sort of no longer become 'issues'? Obviously it has an effect on shorter barrels more than anything...seemingly the shorter you go the more potential for problems.

Based on the discussion here I could say that it sounds like once you go sub-11 inches that's where it might get complicated.

That said with an 11.5 or a 12.5 what are the odds of having a problem?

It's not an issue if you buy a barrel with the correct port size for that length. BCM has a track record of having the correct port size. If you want to "make" your own barrel, I've found that ADCO's track record is also very good when they cut a barrel (for example, when the cut a barrel to 10.3, they cut it to the TDP port size). Centurion Arms is another known quantity for 12.5" barrels.

Personally I'd skip DD. While their barrels are good at many things, they've been documented to be over-gassed.

[DutyUse]

Speaking of ADCO cutting down barrels... I have a Rainer 16" middy CHF barrel. What's the shortest I can cut it down and still be reliable?

[UWone77]

Speaking of ADCO cutting down barrels... I have a Rainer 16" middy CHF barrel. What's the shortest I can cut it down and still be reliable?

I would say 14.5

I also have cut down RA CHF 14.5 barrels cut down to 10.3

[Former11B]

I much rather tune a rifle with buffers than an adjustable gas block. They all pretty much suck. If you reduce the port size they foul faster. Some so fast it will cause issues in a days shooting.

I wouldn't quite say throwing in a heavier buffer is tuning a rifle. Adjusting it so it gets just the right amount of gas to run properly is.

In my experience, reducing the amount of gas into the upper makes it foul slower; It's actually the opposite, and it's a big selling point of an adjustable gas system for suppressed shooting which is why I use them. My factory gas guns get dirty real quick versus my adjustable gas rifles

[DutyUse]

I would say 14.5

I also have cut down RA CHF 14.5 barrels cut down to 10.3

Thanks!

I'm guessing the 14.5 to 10.3 conversion was a carbine gas?

Throwing a heavier buffer in is not "tuning" a rifle. Adjusting it so it gets just the right amount of gas to run properly is.

Explain how reducing the amount of gas into the upper makes it foul faster? It's actually the opposite, and it's a big selling point of an adjustable gas system for suppressed shooting

I'm not sure but I think he means fouling as in the gas regulator on a multiple gas system adjustable gets extremely dirty and can be a pain to change settings once you've used it awhile and could malfunction. I haven't experienced it personally, but have read syrac style GB's can experience this. Only thing I can think of for "more fouling"?

[Former11B]

I would say 14.5

I also have cut down RA CHF 14.5 barrels cut down to 10.3

I'd say 14.5 also. Some companies make middy 13.7" barrels but they probably have gas ports made for it. Safe side would be 14.5

[Former11B]

Thanks!

I'm guessing the 14.5 to 10.3 conversion was a carbine gas?



I'm not sure but I think he means fouling as in the gas regulator on a multiple gas system adjustable gets extremely dirty and can be a pain to change settings once you've used it awhile and could malfunction. I haven't experienced it personally, but have read syrac style GB's can experience this. Only thing I can think of for "more fouling"?

I edited my post; reread it and it sounded asshole-y which wasn't intentional. That's odd and sounds like a design flaw. I haven't had that issue in mine