User Panel
User Panel
User Panel
|
Posted: 11/4/2020 11:03:36 PM EDT
I built an 8.5 upper with suppressor that has a few hundred factory rounds through it and about a hundred handloads, all subsonic. No issues.
It won't cycle factory Sub X rounds for some reason. It always locks back on an empty magazine. Often, it won't chamber Sub X when I hit the bolt catch release. The bolt overrides the case. I've tried different mags and BCG. I checked the mag release and even rotated the mag release button. Today, I loaded a couple mags with a round of Sub X on top followed by a Gemtech and both rounds fired. Switched the rounds and the Sub X jammed again. I have tried about 30 rounds of Sub X in two different boxes with the same results. My case gauge is currently loaned out but I can't think of a reason the bolt won't catch the rounds. I don't think it's a gas, buffer, or magazine issue but I've been wrong before. Anyone have any thoughts?  Attached File Attached File |
|
|
|
Posted: 11/5/2020 3:44:01 AM EDT
[#1]
Check the spent case rims on the Sub X ammo.
If spent rims are bent back, then ammo is producing too much port pressure, and if the rims are not bend back from the extractor pull, then ammo is not producing enough port pressure instead. Hence all boils down to the burn rate of the gun powder being produced, since the faster it's burn rate, the lower the gas port pressure will be. |
|
|
|
Posted: 11/5/2020 5:01:11 AM EDT
[#2]
What mags are you using?
|
|
|
|
Posted: 11/5/2020 5:33:22 PM EDT
[#3]
Bolt lug over case jam, so bolt is not cycling far enough back to get behind the case rim to drive it out of the mag cleanly.
 So either not enough port gas to cycle the B/C all the way back (bolt unlocking too late). Or, too much port gas with the spent case still over pressurized to the chamber walls from the bore residual pressure not bleed down yet from the bolt unlocking too soon to cause the short stroking instead. As for factory loads, should not be so long that the rounds are binding up in the mags from to back, to cause a feeding problem. Also, since other ammo's are running fine in the rig and mag, its the ammo that is causing the short stroking in the rig from either bolt unlocking to slow, or too fast. Hence the reason that the spent case rim will tell the tale of what is going on with the bolt unlock timing. |
|
|
|
Posted: 11/5/2020 5:36:52 PM EDT
[#4]
I've had the sub x be a bit weird in some pmags I think gen 2 30s. Flawless through the 10s. I think the center rib makes them align funny
|
|
|
|
Posted: 11/5/2020 8:39:00 PM EDT
[#5]
Quote HistoryQuoted: I've had the sub x be a bit weird in some pmags I think gen 2 30s. Flawless through the 10s. I think the center rib makes them align funny If your running 30oblk in 223 mags, that is a problem right there. Hence front sections of the 223 mags both sides are ribbed designed to hold the 223 round even with the side of the mag body, and with 300blk mag with 30cal bullet, front section of the round is going to be shoved to the inner middle of the mag from the side ribs instead. So if running 300blk, make sure you are using 300blk mag, and not 223/5.56nato mags isntead. |
|
|
|
Posted: 11/5/2020 8:49:38 PM EDT
[#6]
Quote HistoryQuoted: If your running 30oblk in 223 mags, that is a problem right there. Hence front sections of the 223 mags both sides are ribbed designed to hold the 223 round even with the side of the mag body, and with 300blk mag with 30cal bullet, front section of the round is going to be shoved to the inner middle of the mag from the side ribs instead. So if running 300blk, make sure you are using 300blk mag, and not 223/5.56nato mags isntead. I bet this is the issue then. I am also using regular 5.56 magazines (10, 20, and 30 rounders). This would explain why the bolt won't catch the round manually at times. I will get some dedicated blackout mags and go from there. Also, the case rim on fired Sub X cases look the same as the Gemtec. Thanks for the replies! |
|
|
|
Posted: 1/5/2021 8:26:01 PM EDT
[#7]
@Dano523
Update: You were right, the mags made a difference. Switched to dedicated .300 Lancer mag and it cycled 9 out of the 10 rounds. Much better than a jamming after one shot.  Thanks for the information, I never would have thought the regular mag would cause the issue. |
|
|
Win a FREE Membership!
Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!
You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.
AR15.COM is the world's largest firearm community and is a gathering place for firearm enthusiasts of all types.
From hunters and military members, to competition shooters and general firearm enthusiasts, we welcome anyone who values and respects the way of the firearm.
Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more.
Copyright © 1996-2024 AR15.COM LLC. All Rights Reserved.
Any use of this content without express written consent is prohibited.
AR15.Com reserves the right to overwrite or replace any affiliate, commercial, or monetizable links, posted by users, with our own.
