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Posted: 1/17/2017 7:52:54 PM EDT
[#1]
never heard that. too many variables with different manufacturers..........
i ALWAYS measure. it's the only surefire way to know for sure IMO. |
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Posted: 1/17/2017 8:15:35 PM EDT
[#2]
Might be if you were installing the gas block after removing the handguard cap.
If barrel was cut (gas block shoulder) for use with std. handguard, and you were to switch it to a free floating HG.......then the "spacer"/HG cap, would be absent and distance would need to accounted for. |
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Posted: 1/17/2017 8:36:41 PM EDT
[#3]
Guess I should add this is a new Ballistic Advantage 18" barrel with a rifle length gas system and their .750" gas block.
The credit card "shim" worked on a Bushmaster and then a Mega/Ranier build several years back. At least I think that's the way I did it. I'll be measuring tomorrow. |
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Posted: 1/17/2017 8:53:09 PM EDT
[#4]
If it's a set screw type block just take the appropriate screw out and take a peek into the vacated hole to line it up.
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Posted: 1/17/2017 8:57:19 PM EDT
[#5]
ISO standard for credit cards (all bank cards) are .030 +/- 10%.
Yes, you are OK using them to space the gas block. I have set many gas blocks using a credit card. All function correctly. |
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Posted: 1/17/2017 9:10:08 PM EDT
[#6]
Quote HistoryQuoted:
never heard that. too many variables with different manufacturers.......... i ALWAYS measure. it's the only surefire way to know for sure IMO. |
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Posted: 1/17/2017 9:38:13 PM EDT
[#7]
Quoted:
I haven't installed a gas block in a couple years and I recall you can space the gas block forward from the barrel shoulder using a credit card so that the two ports line up. Am I remembering correctly? Thanks! The credit card trick works because in most cases it does not matter since the hole on the gas block is substantially larger than the gas port hole in the barrel. There is a ton of room for error. Don't believe me? Take your barrel and your gas block, put the gas block on like you were installing it correctly except seat it all the way up against the shoulder. Now, with the set screws removed from the gas block, rotate it 180 degrees so that it is now oriented upside down. Now, look through the set screw hole at the barrel and you will see the gas port. It will be favoring one side of the hole, but it will also be shooting plenty of gas through that hole. The hole on the other side of the gas block, which mates with the gas port, is just as big as the set screw hole. The only way to get it "perfect" is to get it dimpled using a jig that indexes off the gas port. Also, dimpling without a jig that indexes off the gas port hole is pointless and does not increase the ruggedness of the setup, only a pinned gas block will do that. |
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Posted: 1/17/2017 10:24:41 PM EDT
[#8]
Reputable gas blocks have oversized port holes. I shove mine up against the shoulder. I have never had an issue. I don't use ebay parts, no accusations, just saying YMMV if you do.
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Posted: 1/18/2017 7:28:53 AM EDT
[#9]
Why not use a shim available form Fulton?
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Posted: 1/18/2017 7:44:51 AM EDT
[#10]
Quote HistoryQuoted:
Why not use a shim available form Fulton? Because the credit card method works fine and it is free. |
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Posted: 1/18/2017 7:56:11 AM EDT
[#11]
I use an .025 feeler gauge.
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Posted: 1/18/2017 9:47:28 AM EDT
[#12]
Why would you even assume that the gas block needs to be spaced from the shoulder...?
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Posted: 1/18/2017 9:50:14 AM EDT
[#13]
I measure then space accordingly if needed. I HAVE seen rifles that would not function at all when the builder slammed the gas block all the way up against the shoulder, so there is not always enough room. Measure, calculate, space, then you know it's correct.
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Posted: 1/18/2017 9:51:31 AM EDT
[#14]
I noticed the set screw hole was directly under the gas tube port in the gas block so figured that would be my reference.
All the parts I'm working with are from Ballistic Advantage, not ebay. Too many reputable and reasonable dealers to buy much on ebay. And roger, the gas ports look plenty large to still function even with some unintentional offset. Thanks for all the replies. |
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Posted: 1/18/2017 9:53:12 AM EDT
[#15]
Quote HistoryQuoted:
Why would you even assume that the gas block needs to be spaced from the shoulder...? Because the shoulder is set to allow for the hardware to mount a stock plastic hand guard cap. |
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Posted: 1/18/2017 10:39:33 AM EDT
[#16]
Quote HistoryQuoted:
Because the shoulder is set to allow for the hardware to mount a stock plastic hand guard cap. That's a dangerously broad assumption to make about EVERY SINGLE BARREL in existence. Perhaps the better way to state it would be "Many barrels could possibly have the shoulder set for a handguard retaining cap, so it's best to measure the actual gas port distance to the shoulder and set the block accordingly" rather than the way you said it. I personally have at least 3 barrels (that I know of) that are intended for the gas block to sit flush against the shoulder, being intended for free-floated handguards that don't require an end cap. But generalizing a standard from 30 years ago is certainly easier I suppose. 
The proper answer is to measure, at least by removing a screw from set screw blocks as mentioned above. In practical application, unless it's a truly custom barrel with custom gas port size, it'll be overgassed enough that butting the block against the shoulder isn't very likely to have any adverse effects. Still best to measure just to ensure proper placement the first time, though, just in case. 
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Posted: 1/18/2017 1:23:04 PM EDT
[#17]
Quote HistoryQuoted:
I use an .025 feeler gauge. This is what I use too and it has always worked well for Me |
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Posted: 1/18/2017 5:19:55 PM EDT
[#18]
Don't be lazy.
Just measure. |
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Posted: 1/18/2017 7:20:31 PM EDT
[#19]
Measured it and the credit card shim still worked fine.
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Posted: 1/19/2017 1:09:01 AM EDT
[#20]
For Low pro they can vary (block to shoulder distance). Always simply flip the block upside down and match the screw hole to the gas port (many do not realize the block port hole IS the same hole used for set screw hole). Then just look/measure how far off the block is from the shoulder. That's the most accurate/consistent way to get it dead on every time.
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Posted: 1/19/2017 1:16:48 AM EDT
[#21]
Quote HistoryQuoted:
I noticed the set screw hole was directly under the gas tube port in the gas block so figured that would be my reference. All the parts I'm working with are from Ballistic Advantage, not ebay. Too many reputable and reasonable dealers to buy much on ebay. And roger, the gas ports look plenty large to still function even with some unintentional offset. Thanks for all the replies. That's because they use the rearmost set screw hole to drill the gas port on the GB. I always use this method to determine if it needs any spacing (I've only ever had one barrel/GB combo that absolutely needed a gap) and then go from there. |
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Posted: 1/19/2017 1:18:04 AM EDT
[#22]
Quote HistoryQuoted:
Because the shoulder is set to allow for the hardware to mount a stock plastic hand guard cap. Not on all barrels and some LPGBs are built to take up that space since most people don't use LPGBs with handguard caps. |
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Posted: 1/19/2017 7:53:35 AM EDT
[#23]
I used a barrel dimpler on my low pro gas block. It completely takes any guessing out of the equation plus giving you block extra grip.
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Posted: 1/19/2017 10:28:13 AM EDT
[#24]
Quote HistoryQuoted:
I used a barrel dimpler on my low pro gas block. It completely takes any guessing out of the equation plus giving you block extra grip. all that effort, might as well just pin it instead.
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Posted: 1/19/2017 11:55:10 AM EDT
[#25]
All the barrels I have bought over the years have had the standard spacing between the port and the shoulder.
Things change so it is not surprising that there would be barrels that don’t allow for caps. There are gas blocks out there meant to go against the shoulder w/o a cap. However all the ones I have used allow the use of a cap and have to be spaced when a cap is not used. I checked one years ago and the block slightly encroached on the port hole. In reality it probably was not enough to significantly affect anything, but it would have offended my sensibilities and a spacer is just too easy. |
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Posted: 1/23/2017 11:08:28 PM EDT
[#26]
If you want to be sure just use a Gas block Alignment tool.
http://www.brownells.com/gunsmith-tools-supplies/rifle-tools/gas-system-tools/ar-15-gas-block-aligner-prod68371.aspx |
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Posted: 1/24/2017 8:18:09 AM EDT
[#27]
Quote HistoryQuoted:
all that effort, might as well just pin it instead. Effort? either one takes the guess work out. Dimpling is quicker, pinning is overkill IMO for a low pro. With the pinning jig you spend more time in the jig with a small drill bit and they snap really easy, so for just an alignment tool the dimple seemed quicker easiest.Low effort. |
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Posted: 1/24/2017 10:57:10 AM EDT
[#28]
Quote HistoryQuoted:
Effort? either one takes the guess work out. Dimpling is quicker, pinning is overkill IMO for a low pro. Quote HistoryQuoted:
Effort? either one takes the guess work out. Dimpling is quicker, pinning is overkill IMO for a low pro. Tell that to the guys I've seen at the range whose dimpled, loctited, set-screw low-pros got hammered so far forward on the barrel from the action cycling they became single-shot guns.
With the pinning jig you spend more time in the jig with a small drill bit and they snap really easy, so for just an alignment tool the dimple seemed quicker easiest.Low effort. 1. It takes no more time to set up the pinning jig than it does a dimpling jig. 2. I've been using the same drill bit for over 40 gas blocks and not only is it still sharp and cutting well, it has managed to not snap even once. Maybe your problem with your pinning jig was using shit drills or poor technique? 3. Low effort doesn't necessarily equate to "the proper way". But of course this being an internet forum, all manner of lazy folks abound, so if that's your thing so be it. I'll just keep doing it the right way and you do it however you want. 
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Posted: 1/24/2017 11:06:43 AM EDT
[#29]
I just measured every card, DL,CHL in my wallet. They were all between .029" and .033".
Personally, I use a .025" feeler gage. |
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Posted: 1/24/2017 12:36:26 PM EDT
[#30]
Quote HistoryQuoted:
Tell that to the guys I've seen at the range whose dimpled, loctited, set-screw low-pros got hammered so far forward on the barrel from the action cycling they became single-shot guns.
1. It takes no more time to set up the pinning jig than it does a dimpling jig. 2. I've been using the same drill bit for over 40 gas blocks and not only is it still sharp and cutting well, it has managed to not snap even once. Maybe your problem with your pinning jig was using shit drills or poor technique? 3. Low effort doesn't necessarily equate to "the proper way". But of course this being an internet forum, all manner of lazy folks abound, so if that's your thing so be it. I'll just keep doing it the right way and you do it however you want. We are talking about pinning or dimpling a block where the majority of all are just stuck on with set screws with no issue. I dimple just for port hole placement. If I pinned I would still dimple because it is without a doubt the best way to center port hole. The right way to put on a low pro is to simply tighten set screws, not pin or dimple. Its curious that in your area dimpling makes them less reliable than just the standard set screws. Lol |
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Posted: 1/25/2017 12:44:39 AM EDT
[#31]
Subbed for the build I'm doing.
The gas block flows freely when back against the shoulder of the barrel, so I'm a bit surprised spacing it out is needed. |
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Posted: 1/28/2017 2:16:38 PM EDT
[#32]
I used an old spark plug gapper to find the spacing. Lots of different ways to get the same result.
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Posted: 1/28/2017 3:04:37 PM EDT
[#33]
Quote HistoryQuoted:
Reputable gas blocks have oversized port holes. I shove mine up against the shoulder. I have never had an issue. I don't use ebay parts, no accusations, just saying YMMV if you do. "Reputable manufacturers deviate from specifications." 
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Posted: 1/28/2017 3:06:08 PM EDT
[#34]
Quote HistoryQuoted:
Effort? either one takes the guess work out. Dimpling is quicker, pinning is overkill IMO for a low pro. With the pinning jig you spend more time in the jig with a small drill bit and they snap really easy, so for just an alignment tool the dimple seemed quicker easiest.Low effort. Ford once did an internal study and found that 90% of all catastrophic failures were attributed to threaded fasteners. |
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Posted: 1/28/2017 10:10:54 PM EDT
[#35]
I went by the dealership, but they just looked at me funny when I tried to get a good deal on one of their ARs and a car that's assembled with taper pins.
I dimple then Rocksett the screws in my blocks. |
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