gas port size

[ARlife4me]

These are not bad for the price point. I use a different brand, but much more expensive, but the same class.

Precise .061-.250" Plus, Class ZZ Steel Pin Gage Set - 303-503P

Achieve precision in your measurements with the Precise .061-.250" Plus Class ZZ Steel Pin Gage Set. Crafted to exacting standards, this set provides accurate measurements for metalworking and machining tasks, ensuring quality results in your workshop.

www.penntoolco.com

Order placed

 

[ntsqd]

I'm following along in the hopes of learning more. The comments about gas tube location in posts 6 & 7 likely warrant a separate thread as I'm intrigued by them.

I notice that those pins are "+" pins rather than "-" pins, are they the preferred type for this use?

 

[bamban]

I'm following along in the hopes of learning more. The comments about gas tube location in posts 6 & 7 likely warrant a separate thread as I'm intrigued by them.

I notice that those pins are "+" pins rather than "-" pins, are they the preferred type for this use?

I have both + and - , but not for this purpose. The gas port is not a critical dimension to a tight tolerance. Most likely the mass produced barrels are drilled, not reamed. Drilled holes may or may not be exactly round.

On the service rifle barrels I do, I drill with 2mm carbide, followed with 0.096 4 fluted carbide reamer. By CMP/NRA rulebook, service rifle legal barrels cannot have adjustable gas blocks.

I used to chamfer the inside hole. Not doing the chamferring any longer.

 

[ntsqd]

Thank you. I wasn't sure just how on-size and round they needed to be.

 

[kfreeze]

I want only experienced Smiths about gas port size, location and cartridge specific to help out this/these question/s please. Other people with 1st hand knowledge can/could help also IF they know their port size! Some of my barrels I know port size on only due to manufacturer list it and depends on gas system length thereof. While I have many 6.5creeds in AR's, not all function well with standard carbine/rifle buffers and springs. This also translates to other 308 based cartridges of .473 bolts (anything with that bolt face, but not necessarily 308 based). Aero Precision is THE only company I've bought from with 100% reliability in rifle length gas systems with barrels from 20-24" with standard weight buffers and springs. I also have "camgas" systems (+2) in 260rem and 6.5creed that DOESN'T function as well until other mods are done. Is there a good way to find out what the port size is without going to a Smith? The recoil is fine with the AP: barrels and gas length with standard weight recoil components. I have a CBI barrel that shoots bug holes, but is in need on mod work (I haven't had time to do it yet) that has a rifle gas system 22" barrel that's overgassed (for now) as it pops factory ammo's primers (Hornady 123a-max and sst's), but the AP barrels work 100% perfect. I might have the port opened up more or just increase buffer weight (in the works when I have time). I do have several buffers I can change out as not to mess with taking apart buffer in the field. Has anyone used a + gas with a 308win? Port size and location is EXTREMELY important on non-308win's is what I've come to learn the difficult way. Sure, throw in a h3/h2/h4 and call it good, but I'd rather have answers to the questions. This isn't a debate or p i s s i n g match, so keep it calm as some can't help themselves! If you have a factory complete gun or upper and know what specs are as far as port size, location and cartridge goes (non-308 type) feel free to chime in!

I've not dealt with tons of barrels by any means, but I've had to send a few new ones back to have gas ports drilled larger. The one thing that I have learned through all of the builds that I have done is to never mess with buffers, springs, and etc. Just use a good click adjustable gas block and be done with it. All of the other stuff is people hoping for a cheap fix and theirs never works perfect like when I get them to put a good adjustable gas block on. Just start with it almost closed and open it slowly until the bcg stays locked back after you shoot on an empty mag. Then if you really want to do yourself a favor for loading your own ammo, when you order a new barrel ask them to open the gas port an extra .010". X-caliber is happy to do it by tha way and thanked me for telling them that I was going to use an adjustable gas block so they could make it work perfect for me. (There is so many variables with powders and loads once you go away from the milspec stuff that they can't control, so they design their gas systems to work with certain things). The other best thing that I can tell you, besides the good adjustable gas block, is to call and talk to the people that will make the barrel that you want and talk about the specifics of what you want.

 

[DoneNOut]

I've not dealt with tons of barrels by any means, but I've had to send a few new ones back to have gas ports drilled larger. The one thing that I have learned through all of the builds that I have done is to never mess with buffers, springs, and etc. Just use a good click adjustable gas block and be done with it. All of the other stuff is people hoping for a cheap fix and theirs never works perfect like when I get them to put a good adjustable gas block on. Just start with it almost closed and open it slowly until the bcg stays locked back after you shoot on an empty mag. Then if you really want to do yourself a favor for loading your own ammo, when you order a new barrel ask them to open the gas port an extra .010". X-caliber is happy to do it by tha way and thanked me for telling them that I was going to use an adjustable gas block so they could make it work perfect for me. (There is so many variables with powders and loads once you go away from the milspec stuff that they can't control, so they design their gas systems to work with certain things). The other best thing that I can tell you, besides the good adjustable gas block, is to call and talk to the people that will make the barrel that you want and talk about the specifics of what you want.

I've pulled ejector swipes off brass going from carbine weight buffer to 5.3oz. Granted, this move makes up about 10% of the totality of the project.

 

[kfreeze]

I've pulled ejector swipes off brass going from carbine weight buffer to 5.3oz. Granted, this move makes up about 10% of the totality of the project.

I've pulled the ejector swipes away with an adjustable gas block too. Then I put in a jp silent captured recoil spring with the lightest spring and a low mass bcg. Then I tuned my adjustable gas block and I could magically watch my bullet inpacts in my scope on 24x at 300 yds. Point that I was making is that everything that all the screwing around gets you and more can be done with a simple gas block change. Then the adjustable block works for all situations, except too small of gas port. Then the manufacturer has always been eager to fix it for me.

 

[ARlife4me]

I've not dealt with tons of barrels by any means, but I've had to send a few new ones back to have gas ports drilled larger. The one thing that I have learned through all of the builds that I have done is to never mess with buffers, springs, and etc. Just use a good click adjustable gas block and be done with it. All of the other stuff is people hoping for a cheap fix and theirs never works perfect like when I get them to put a good adjustable gas block on. Just start with it almost closed and open it slowly until the bcg stays locked back after you shoot on an empty mag. Then if you really want to do yourself a favor for loading your own ammo, when you order a new barrel ask them to open the gas port an extra .010". X-caliber is happy to do it by tha way and thanked me for telling them that I was going to use an adjustable gas block so they could make it work perfect for me. (There is so many variables with powders and loads once you go away from the milspec stuff that they can't control, so they design their gas systems to work with certain things). The other best thing that I can tell you, besides the good adjustable gas block, is to call and talk to the people that will make the barrel that you want and talk about the specifics of what you want.

I've seen that option on their site along with other custom makers. If you have a proper sized port and location you will never need an adjustable gas block. I use in some AR's the jp-scs along with a lighter weight bcg (not always a lighter bcg).

 

[kfreeze]

I've seen that option on their site along with other custom makers. If you have a proper sized port and location you will never need an adjustable gas block. I use in some AR's the jp-scs along with a lighter weight bcg (not always a lighter bcg).

But if you order it that way, you get the option to load with different powders and not have a problem. When they figure out the gas port size, they use a specific load or a couple of popular options. I had a nice conversation about that with a gentleman at x-caliber years ago. For me, way easier to adjust it down with a block than send a barrel back to get the gas port opened up.

 

[budlight]

I have reload 308 for many years and have developed some nice rounds using modern powders. Nothing hot rodded near max. I've always found higher accuracy is generally achieved with somewhat less powder than the max listed in loading tables. My ar10's in 308 love them.

The my buddy buys this heavy expensive FN SCAR 20S. So he wanted a few hundred reloads for cheap shooting. So we went out shooting and on the 2-3 shot the SCAR jams. Like couldn't even get the bolt open. I had to pry it with a phillips screw driver. It had blown a primer. first though is did it get an overdose of powder on my Dillion 550. So he tried again and 3 shots later it did it again.

What I didn't understand is that it could only use lower powered service rifle loads or it would blow primers.

You said that your rifle blows primers. What would you have to do to fix that? My buddy sold the SCAR and we made a ar10 that runs fine.

 

[ARlife4me]

These are not bad for the price point. I use a different brand, but much more expensive, but the same class.

Precise .061-.250" Plus, Class ZZ Steel Pin Gage Set - 303-503P

Achieve precision in your measurements with the Precise .061-.250" Plus Class ZZ Steel Pin Gage Set. Crafted to exacting standards, this set provides accurate measurements for metalworking and machining tasks, ensuring quality results in your workshop.

www.penntoolco.com

Per your suggestion I received my order today. Thanks goes outta @bamban ! You da man!

 

[victor3ranger]

Wow that's fancy

 

[ARlife4me]

Wow that's fancy

Still has the oil and paper on the pins. All are marked next to the pins from .061-.250" (68 pins I think). Using them to find out what gas port size some barrels have that companies don't list in barrel info. Aero Precision list port size on each of their barrels which is nice.

 

[ARlife4me]

They did say (the place purchased from) about the box color might not be as shown on the site. Makes no difference too me as long as all of the pins are there the box could be pink.