SBR Build questions

[Sebrock]

Thank you all for the ammo suggestion now here is my next question. I am taking a Giselle Super Duty and throwing an 11.5 inch proof barrel and an adjustable carbine length gas system. I am running a Socom Mini 2. I also bought an H2 buffer just in case. Im thinking that I will install the heavier buffer and then tune the gas system until it works with my defense ammo and plinking ammo. I’m more of a bolt action guy and have never modded an AR. I called Surefire and this was their suggestion. What is everyone else’s experience with getting these to cycle properly?

 

[bfoosh006]

Since you can regulate the barrels gas flow.... you should be able to tune it to your setup / parts choices, via the Adj. GB.

Bear in mind.... ammo choices can vary in "power" by quite a bit. PMC Bronze and Remington 55gr tend to be at the low end of the cycling scale, and the various high dollar 5.56 SD rounds tend to be max'd out.

BTW, what chamber is the Proof research barrel cut with ?

 

[Sebrock]

Since you can regulate the barrels gas flow.... you should be able to tune it to your setup / parts choices, via the Adj. GB.

Bear in mind.... ammo choices can vary in "power" by quite a bit. PMC Bronze and Remington 55gr tend to be at the low end of the cycling scale, and the various high dollar 5.56 SD rounds tend to be max'd out.

BTW, what chamber is the Proof research barrel cut with ?

Yeah that’s my fear with the ammo. Plinking ammo is just standard but the stuff that I need to never fail is self defense SBR ammo built for that purpose which, from what I gather, is a heavy grain frangible projectile with a slow burning high velocity powder. It’s a 223 Wylde chamber too which I’ve never had. I’ve always run a 5.56 chamber. Also thoughts on running the heavier buffer?

 

[bfoosh006]

Yeah that’s my fear with the ammo. Plinking ammo is just standard but the stuff that I need to never fail is self defense SBR ammo built for that purpose which, from what I gather, is a heavy grain frangible projectile with a slow burning high velocity powder. It’s a 223 Wylde chamber too which I’ve never had. I’ve always run a 5.56 chamber. Also thoughts on running the heavier buffer?

The reason I asked about the chamber is, some of the full power 5.56 ammo recommendations ( from your other thread ) when run in a .223 or .223 Wylde chamber, can exhibit pressure signs. Those rounds are intended for a longer throat 5.56 chamber. ( The longer throat allows the bullet to scoot forward slightly prior to building a full head of pressure at the rifle lands, "kinda of increasing" the chamber volume ... short answer, but effective.... Weatherby rifles do the same thing, with their ammo )
They might be fine in your .223 Wylde chamber. You will be able see typical pressure signs on the fired case head.
In a .223 chamber ... no thank you.

Ammo weights or specific choices, also depend on your ( IMHO ) how accurate they are, or how accurate you are comfortable with.
Honestly, all sorts of bullet weights can work quite well... Speer 75gr Gold Dot-55gr Gold Dot as an example.

It depends on bullet designs as much as velocity... and the various manufacturers do a danged good job of finding a combo that works for the task at hand.

Given your shorter effective range and barrel length choice... ( again kind of... ) you "need" a bullet that will expand / function at slower velocities.
This thread... is packed with valuable velocity info for 10.5" , 11.5" , 12.5" and 14.5" barrels. ( Join AR15.com to view the info.. it is worth it. )
https://www.ar15.com/forums/ar-15/S...-10-5-11-5-12-5-and-14-5-ALL-DONE-/16-714088/


I have different ammo in various mags depending on what I intend it to be used for. ( 11.5" barrels )... hard barriers ( glass, cars ) , soft barriers... etc .
The 5.56 has improved dramatically over the years.... but it is still hard to find ( IMHO ) a does it all bullet for every scenario.

I prefer the 5.56 chamber. But don't let the .223 Wylde chamber comments intimidate you , it is just something reasonably important to be aware of.
Solid bullets, like the 50gr TSX Optimized, the Mk318, do not compress as readily in a barrel bore ( like lead core bullets do ) combine that with a full power 5.56 powder charge , and it is kinda like you maxing out your RPM's on your car , it can handle it... it just accelerates wear on various parts.

As for the buffer weight, after you get the firearm assembled... you'll be able to tune it.
It is hard to predict what buffer weight will work in your firearm....way to many variables.

1. Gas port size matters a lot... I have seen massive gas ports and tiny gas ports.... that alone would alter any recommendations I would give.
2. Gas port position... different operating pressures from the various positions.
3. Suppressed ? lots of back pressure...
4. Intended use .... fast shooting run n' gun, or a intended SD firearm, or a long range varmint firearm ?
5. Caliber ?
6. Barrels dwell time ?

So while it seems easy... it really depends on your specific use and the above info .

That or you just go USGI and accept a what it is. ( Not trying to sound flippant.. )

Its kind of like asking what tire for your vehicle. Lots of answers, dependent on the intended use..

 

[clcustom1911]

Thank you all for the ammo suggestion now here is my next question. I am taking a Giselle Super Duty and throwing an 11.5 inch proof barrel and an adjustable carbine length gas system. I am running a Socom Mini 2. I also bought an H2 buffer just in case. Im thinking that I will install the heavier buffer and then tune the gas system until it works with my defense ammo and plinking ammo. I’m more of a bolt action guy and have never modded an AR. I called Surefire and this was their suggestion. What is everyone else’s experience with getting these to cycle properly?

Easy cheesy, lemon squeezy.

If your gas port is 0.070-0.076" you should be good to go with a H2 and no need to do gas block adjustments. That size gas port will allow for reliable cycling with most ammo in majority of weather conditions/temperatures.

Ive been shooting 10.3-11.5" carbine gas platforms for years unsuppressed, RC2 mini, and full dong RC2. H2 and standard buffer spring. If your gas port is larger, you'll need to adjust gas down. I always opt for slightly overgassing instead of "perfectly gassed" so all my ammo will work in assorted weather conditions, and when dirty (i clean only every 800-1000 rounds, lube often-ish)

 

[Sebrock]

Thank you all for the advise. On the 223 Wylde - it’s the only offering proof has so I think it’s probably well designed - that being said - will 100 percent check for pressure signs on the case head. Will also check out the ar-15 forum.

On the last comment set up advice 10-4. Will start with original buffer and gas block in the default position and then take it from there. Hopefully there isn’t much tuning needed.

 

[clcustom1911]

Before I knew better, I used standard "carbine" weight buffer instead if H1, H2, etc. No bueno. Bolt speed was way too fast and was ripping case rims off, causing failure to extract, double feeds, etc.

On carbine gas with 14.5-16", H1.
Carbine gas with 10.3-12, H2.

Gas port size is critical. A 5/64 drill bit is 0.078" that what I use as my go/no go for my carbine length gas barrels as I dont want to deal with adjustable gas blocks... because i have in the past and sometimes they're more trouble than what theyre worth. Better to have a proper sized gas port so you dont have to "fix" something to get it into the proper spec it should have been. I've heard of some barrels (including Proof) shipping with 0.100" (or larger, 0.125" 1/8") gas ports. Thats malarkey.

I have a custom Bartlein mid-gas 14.5 with a 0.076" and it cycles mid-loaded 55gr 223 ammo and a H1 just stupid smooth.

 

[Sebrock]

Before I knew better, I used standard "carbine" weight buffer instead if H1, H2, etc. No bueno. Bolt speed was way too fast and was ripping case rims off, causing failure to extract, double feeds, etc.

On carbine gas with 14.5-16", H1.
Carbine gas with 10.3-12, H2.

Gas port size is critical. A 5/64 drill bit is 0.078" that what I use as my go/no go for my carbine length gas barrels as I dont want to deal with adjustable gas blocks... because i have in the past and sometimes they're more trouble than what theyre worth. Better to have a proper sized gas port so you dont have to "fix" something to get it into the proper spec it should have been. I've heard of some barrels (including Proof) shipping with 0.100" (or larger, 0.125" 1/8") gas ports. Thats malarkey.

I have a custom Bartlein mid-gas 14.5 with a 0.076" and it cycles mid-loaded 55gr 223 ammo and a H1 just stupid smooth.

Thats the buffer I got for the Carbine but it looks like mine already came with an H2 so will just return it. Will take a look at gas port when the barrel gets here. Giving it to my gunsmith to put together so he should be getting it right.

 

[r.tenorio671]

...a Wylde chamber will handle 556 NATO pressure rounds with no problem. The design of the Wylde was to "hybridize" the freebore dimension to give improved accuracy while still being fully capable of the 62K psi of NATO ammo. Remember, all the commercial ammo is loaded to the magazines limitation of 2.260", in many cases less than that maximum. The signs of "overpressure" on fired brass are not always indicative of overpressure, but a timing issue, early unlocking and extraction. Timing issues can be mitigated by multiple methods, singly or combined, i.e., buffer weights, buffer springs and adjustable gas blocks. The key contributing factor is the size of the gas port that the barrel maker puts in the barrel. Barrel makers have pretty much figured out port sizes, but again, they usually size them to work with a majority of the commonly available ammo choices in the market. If the barrel came standard with an H2 buffer, then the port most likely is slightly "oversized" and the H2 buffer will accommodate most 55gn FMJ thru 77gn commercial ammo reliably. Lighter bullets/loads may encounter cycling issues with the H2 installed, even if you have an adjustable gas block installed. AGB's typically "restrict" the amount of gas on oversized gas ports, but do nothing to increase amount of gas of an undersized gas port. On smaller sized gas ports, the AGB adjustment will typically be minimal, if not wide open if the gas port size is minimal. In this scenario, buffer weight and/or buffer spring adjustment is the proper mitigation process.

Regardless, whatever HD ammo you finally decide on, that is the ammo you want to test/train with and make sure you have absolute reliability with.

 

[Sebrock]

...a Wylde chamber will handle 556 NATO pressure rounds with no problem. The design of the Wylde was to "hybridize" the freebore dimension to give improved accuracy while still being fully capable of the 62K psi of NATO ammo. Remember, all the commercial ammo is loaded to the magazines limitation of 2.260", in many cases less than that maximum. The signs of "overpressure" on fired brass are not always indicative of overpressure, but a timing issue, early unlocking and extraction. Timing issues can be mitigated by multiple methods, singly or combined, i.e., buffer weights, buffer springs and adjustable gas blocks. The key contributing factor is the size of the gas port that the barrel maker puts in the barrel. Barrel makers have pretty much figured out port sizes, but again, they usually size them to work with a majority of the commonly available ammo choices in the market. If the barrel came standard with an H2 buffer, then the port most likely is slightly "oversized" and the H2 buffer will accommodate most 55gn FMJ thru 77gn commercial ammo reliably. Lighter bullets/loads may encounter cycling issues with the H2 installed, even if you have an adjustable gas block installed. AGB's typically "restrict" the amount of gas on oversized gas ports, but do nothing to increase amount of gas of an undersized gas port. On smaller sized gas ports, the AGB adjustment will typically be minimal, if not wide open if the gas port size is minimal. In this scenario, buffer weight and/or buffer spring adjustment is the proper mitigation process.

Regardless, whatever HD ammo you finally decide on, that is the ammo you want to test/train with and make sure you have absolute reliability with.

Thank you for this explanation. Makes perfect sense. I have to imagine that this Proof barrel I got is sized correctly - but guess will then move to the buffer side of things if wide open it doesn’t cycle. Additionally, will test with all ammo I use but most important is the HD ammo. Sounds like I should stay away from the sub 50 grain varmint loads.

 

[Paradox]

Thank you all for the ammo suggestion now here is my next question. I am taking a Giselle Super Duty and throwing an 11.5 inch proof barrel and an adjustable carbine length gas system. I am running a Socom Mini 2. I also bought an H2 buffer just in case. Im thinking that I will install the heavier buffer and then tune the gas system until it works with my defense ammo and plinking ammo. I’m more of a bolt action guy and have never modded an AR. I called Surefire and this was their suggestion. What is everyone else’s experience with getting these to cycle properly?

11.5" and shorter MK18 10.3 had spec's to balance buffer to ammo requirements. H for the M193, and may or may not with M855s, but H2 is the recommended solution for 62gr M855, and 77 gr MK262 with 77gr offering the best performance in government tests. I have an 11.5" but never ran any 55gr in it, and have only shot it with 77s. This info is not my opinion but what i researched and the government designated specs for proper function and performance.

 

[the monk]

Any idea on the port size of the proof?

For your use case, I would not use the adjustable gas block. With that suppressor I think you will be fine.

 

[r.tenorio671]

....FWIW, and I expect to get flamed for this, but....

I always wonder why folks start their builds out with various "upgrades" from multiple manufacturers. Over the years in many forums I've seen folks reporting/asking for help when they finally assemble their cornucopia of parts and it doesn't work. I get it, "customizing" or "accessorizing" is a real thing, but IMHO, it should not come at the expense of a fully functional and reliable platform.

I would bet many folks have a "standard" MILSPEC buffer system (tube, spring, & buffer), gas block and BCG in their parts bins. IMHO, starting with those parts for the testing of the build reveals what if any weaknesses exist and where. I do acknowledge that an AGB in its fully opened mode is the same as a non-adjustable so this can be considered an exception. As the platform is "broken in", the persistent issues become more evident and in some cases the amount of issues decrease as a result of the breaking in period. This is when "swapping/upgrading" of parts should be done, and a single component at a time as combinations can worsen the original issue and make debugging less clear.

My PERSONAL experience over the years with multiple AR15/10 carbines using "standard MILSPEC" recoil systems & BCG's coupled with my preferred AGB to moderate my gas have produced reliable platforms with commercial and my handloaded ammo. I always validate my builds with commercial ammo and if needed, adjust my AGB to accommodate BOTH so switching between requires no further adjustments.

...ok, rant over.... YMMV