Help... Tuning Syric Ord gas block with AAC 7.62-SD

[Kikn]

I had just got my new gas block in from Midway USA http://www.midwayusa.com/product/321768/...ubv1363956

I had it installed by the gunsmith yesterday and got to the range today to check it out and tune it.

Previously had my ZERO set at 100 Yards with my new reloads 123 SST (27.9Gr. TAC, 2.245 COAL, WSR primers, temp 70*) and my previous results were more than satisfactory with that load.


Gas block set all the way down and backed off 3 clicks.

Come today at the range i fire my first shots (temp 40*) with that same load and it shot about 6" high at the same 100 yard distance. (Unsupressed)

I dail in my scope and adjust the gas block a little bit, check everything and it is now zeroed in and grouped nicely at about 2 holes touching 1 about 1/2" away.(Unsuprressed). I put the supressor on and now the shots are about 5" low and sparadic, I take the suprressor off and its back to where it was prior, right on the money.

So i back off the gas block (Counter-clockwise) 3 more clicks opening up the port

once again my zero is off and i adjust and rezero the gun. (unsupressed) i get good groups and suppressed it is grouping nice only problem is its 1.5 MIL's low. and now i'm getting a lot of gas face where i wasn't before with my stock COLT gas block with fixed front sight.

I only took 35 rounds with me and didn't get a chance to readjust I did burn some rounds earlier when it was so dark I couldn't see my bullet holes up at the top of the target without the light on at that target so I had to move

Aparently i need to figure out how many turns to move my adjustment when shooting suppressed so that my zero is the same.

Any tips out there for getting this right or should i just get used to having to deal with two different zero's?

[mongoosesnipe]

your zero will more than likely change with the mounting of an end mount suppressor your adding over a pound to the end of the barrel that tends to affect the pitch of the barrel in relation to the sight as for the gas face it should improve if you close the gas port up a little bit

[Kikn]

Before I changed gas blocks the zero was almost identical. When adding a suppressor prior it would move my shot location higher about half an inch. Now its almost 5" lower with the new block.

[Lead Chucker]

HUMMM... Im using a JP adjustable with a AAC cyclone. I just adjust the block to where the bolt will lock black. Mine shoots the same with or without the suppressor. Must be a gas issue.

[mongoosesnipe]

I would say your over gasing then, you have to set it such that the bolt locks back on an empty mag

[Lead Chucker]

I would say your over gasing then, you have to set it such that the bolt locks back on an empty mag

Yep.. thats what i ment when i said "i adjust it to where the bolt will lock back" on a empty mag. I turn the gas almost all the way off, then open it 1/4 turn at a time til the bolt locks back on empty mag, then a 1/4 turn more.

[Kikn]

Well, i went back to the range yesterday and turned the gas block all the way off. (tested it by firing a round without the bolt opening)

opened it up about 1 full turn where it was barely locking back with an empty mag. (proceeded to make another half turn for reliability)

got it sighted back in again everything is grouping nicely without the suppressor. I put the suppressor back on and find it is still shooting nearly 6" low and off to the side 1.5" @ 100 Yards.

I'm about ready to pull this gas block off and sell it and put back on the factory block (After I modify the front post off of it via the bandsaw)

At least with the old gas block I didn't have any issues with the suppressor effecting my zero.

So in my mind I have one of two issues.

1. The gas block isn't working with the grendel and is the cause of all my problems

2. The flash hider being removed got torqued and is out of time or warded causing my shots to go off target with a suppressor and I am risking a serious baffle strike at any given moment.

[Kikn]

Also I should probably note that prior to having put on this gas block I was shooting the 123 SST with 27.9 Gr. of TAC without any signs of pressure.

Now with this new gas block i am starting to see my primers flatten, with the same load.

[montana]

I have used three Syrac gas blocks and one is on a 11.5 inch barrel with a suppressor and have had zero problems with it. But I am stumped why the gas block would be the cause of the different points of impact or gas pressure problems unless your having a problem with the way you mounted it and it is some how shifting with the extra weight of the suppressor. If the internals were gunking up or the adjustable screw was broke you should see the same problem with the suppressor off. Let us know what you find out if you would please. I had problems with the JP adjustable gas block when the adjust. screw came loose during a multi gun match and my rifle stopped cycling. Murphy's curse must be toying with both of us.

I was wondering if the adjustment screw feels any different when you first put it on ? If the adjustment spring and stop pin is broke perhaps the extra pressure from the suppressor is opening the gas port and cycling different.

[Kikn]

Well it looks like I may have figured it out. I really won't find out for sure until tomorrow.

I haven't really dedicated that much time to working on this issue as I was hoping that it was an ammo issue and I finally finished off whatever left over ammo I had made up today.

I went to the range today to work up a new load using IMR 8208. Hoping that a different load would yield different results. I really didn't think it would change anything but hey what the heck anything is worth a shot right...

So anyway. I got to the range today and about 5 miles from the range it starts to pour down rain on a 10% chance of Precipitation day....so after pulling 3 people out of the mud and cleaning up a bit. The range owner gave me free reign of the range (Everyone else left, including the owner/range officer)

I had cleaned the gun and removed my scope Quick Detatch BoBro mount so I decided to use some of my left over ammo for a control and to make sure it was still somewhat zero'd. I fire 3 rounds at 100 have a nice little group about an 1" and then proceed to shoot a steel 4" hanger at 200. I record a hit and proceed out to 400. I fire 3 rounds at a metal target and make good hits. And move up to 500 and fire 5 shots at the metal plate and afterwards I get off my table and go walk out and take a look. All is well everything is shooting as expected.

So I do my testing on my reloads 27.7, 27.9, 28.1, 28.3, and 28.5 of IMR 8208

I fire 3 rounds of 27.7 zoom in to see how it went. Hmmm.... all misses. So I dial back down my scope from 3.5 mils back to zero where it belongs and move on to 27.9, 28.1 and so on firing 3 rounds each per load.

BTW: 27.9 and 28.1 were the best and very similar. I did take my chrony but decided not to use it.

After getting a base for what a 3 shot group looked like for each round. I pull out my suppressor. (I finally get to what this topic is about)... so I fire all remaining rounds on the same targets as the loads were. And as it moved up in power loads so did the spread of my groups (If you can call it that as it looked more like a shotgun blast). 27.9 was about 5" low 28.1 was about 7" low, 28.3 was about 14" low..... I'm like WT Heck!

Dumbfounded with my results I load up some old load that I had from what I did with barnes 120 TSX I fire two rounds at 100 which are side by side and fire a 3rd round at 200 and hit the steel hanger just for kicks before I put the suppressor back on. I fire two rounds with the suppressor and its about 2" low seems acceptable to me.

So after I leave the range. (I swear the story is coming to an end soon....I think) I decide to go back to the shop I had the install of my gas block done. I speak with the gunsmith and his apprentice. After going over the gun and the suppressor they can't find anything wrong, bring out the bore scope and yada yada yada do this and that. At a certain point I thought he was going to try and blow me off and BS me. But I think he stayed with it and we talked it out. What I thought what changed and whatnot.

Anyway, to bring this to an end. It appears that it really may be the gas block that is the issue. Not really a failure of the gas block but more of an issue of a node change due to the previous gas block being pinned.

So I have a hole where my gas block was prior to me changing it. And it is believed that it is causing a harmonic imbalance when adding the suppressor causing my rounds to deflect low and be sporadic in the shot location.

It actually makes sense to me. So I'm going to cut down my old A2 gas block and put it back on the gun tomorrow. To clean it up i'm going to put a YHM free float hand guard over it. Then I'm going to take it to the range with some new loads I made when I got home of 123 SST ,IMR 8208, 28.0 @ 2.23 COAL and hope for the best.

[Kikn]

Well I can't say its perfectly back to normal; but its closer. Instead of being 10-14" low its only about 2-3" low @ 100yards with factory hornady 123sst. My reloads although with this gas block it didn't group well, same as with the hornady, groups weren't very good with or without the suppressor. Maybe copper fouling from those Barnes rounds,as I didn't clean the barrelyet.

I did get a longer YHM handguard to hide the ugly after chopping up my A2 colt gas block