Full speed rapid fire segments from the Foxtrot Mike Foldyboi YouTube video that dropped earlier today. Buffer: FM RMB, A5 buffer tube (required by the RMB).
ROF: 873 (7"), 805 (5"), 822 (7", mag loaded short), 842 (7"), per ROF-GUI.
https://www.youtube.com/watch?v=uiWl1-vXM08
(Picture was posted automatically by Reddit - sorry it's not clickable - not my fault)
Six minutes.
This is my FRT test with Foxtrot Mike "Foldyboi" w/RMB buffer system & A5 buffer tube and Atrius Forced Reset Selector. Tested with 7" Mike 9 upper and 5" VFM upper.
Both configurations worked well. Around 840 RPM with the 7" upper, around 800 RPM with the 5" upper (my favorite so far).
Had one DT/LS. All the details on potential fixes coming up in another video.
Sorry for the B/W Slow Mo, but YouTube's compliance policy is vague and I don't want to risk losing the channel, so I'm keeping it "artistic".
I'll try to post full speed runs on Reddit later. ETA: www.reddit.com/r/supersafety/comments/1tkjqlo/full_speed_fm_foldyboi_atrius/
2 pictures. Pictures show a Partisan Disruptor vs a MAS Defense 9mm bolt.
9MM AR "2-piece" bolts, with the separate weight that is part of the LENGTH of the rear of the bolt, may NOT work with some FRT triggers.
If the bottom channel in the bolt is wider just before it gets to the weight, the trigger trip may get overridden by the bolt and ride inside the channel instead of being tripped (pushed forward). A different bolt with a standard trip surface and narrow channel will probably be necessary.
Outdoor Sports USA is one example of a good 9mm bolt with proper trip surface for reference.
Unfortunately the OP who posted this problem deleted the post as soon as they had a solution. People, please, if you ask for troubleshooting help, don't delete the post once you have the answer! The record of the fixes help future visitors with the same problem!
2 pictures attached. 2nd picture is fully disassembled.
I just received this in today. Here's some details...
Testing/comparison will take place in the next few weeks. First will likely be in a standard semi-auto setup, then later in an FRT setup.
I'll do high speed video bolt bounce testing as well as felt recoil and FRT performance as time allows.
Original post: https://www.reddit.com/r/supersafety/comments/1sy7sds/9mm_ar_dtls_stronger_firing_pin_spring_source/
Quick Recap: One of the causes of Dead Trigger/Light Strike (DT/LS) SS/FRT failures in 9mm blowback AR's is believed to be "firing pin bounce". As the bolt slams forward and stops, the firing pin continues forward under inertia and it can't get back in place (rearward) in time for the next hammer strike = dead trigger w/ light strike. Using a stronger FP spring or a lighter weight titianium firing pin has fixed this problem for many people.
The problem is that there is no source for stronger firing pin springs for most 9mm bolts. The UXcell Amazon spring recommended only for older FM bolts with the very weak spring, is only slightly stronger and may not do the trick. The new FM FP spring is stronger than the UXcell.
I've been searching for a good replacement firing pin spring for SS/FRT use that would help prevent DT/LS without compromising reliability.
I have one older 9mm bolt with a FP spring that takes 100oz. for L2 compression (tip full protrusion) and it works perfectly, so I figure anything less than this should be fine.
I decided on the following springs, as these choices give about 2x-3x the L1 (resting) oz. force required to get the FP moving, while increasing the L2 (full compression/pin tip protrusion) by about 1.7-2x. In their respective bolts, they give about 30oz. L1, 50oz. L2. See chart for details.
Lee Spring LC 026BC 08S for FM bolts.
Lee Spring LC 026BC 09S for most others (Outerwild, IDL Industries, Palmetto verified fit).
Here's the update:
I tested both and they had no problem with ignition using a standard milspec trigger set in their respective bolts. I ran several mags through each with SS/FRT and there were no issues. I did have one DT/LS with the FM when using the current stock spring so if I can run a bunch of ammo though the same setup with the stronger spring and get no DT/LS, it may serve as confirmation. More testing is coming.
As I mentioned before, the cost from Lee Spring is very high for individual springs, so hopefully some enterprising individual/company will bulk order and offer them at a reasonable price if the testing all pans out.
Followed the details found on the sidebar for modifying the kit. Since it's an Atrius it doesn't need a SS cut, but I cut the right trigger arm angle like for a SS since it's not needed and gave me a better view of what was going on in the rig.
The front bottom underside of the cam hook disconnector needed to be trimmed per the sidebar link. I over trimmed it by accident, resulting in the disconnector barely holding the hammer even when the trigger was released. Carefully stoning back the cam side disconnector hook fixed the issue.
It was still resetting the trigger on the 3rd cam notch (constant FR mode instead of 3 round burst) when I remembered Atrius may have a slightly oversized cam and the trigger arm may need the height reduced per YouTuber Kurisutofer. Made his trigger arm mod with the belt sander and it started working as shown.
Due to a happy accident of scheduling I was able to get the FM/ARC out to test and it worked very well. No modifications necessary other than adding a timing shim to the Arc. The FM bolt is precut for FRT/SS, so this makes it an easy FRT setup. ROF around 830 RPM.
No bolt weight trim, no changing firing pins or FP springs. Just drop in.
Timing shim is added by removing the left selector, dropping 1 shim over the exposed shaft of the Arc, and reinstalling the left selector. That's it.
Next test is going to be with an Atrius FRS in the next few weeks.
ETA: I should said in the title "PROBLEM REPORTS" not "FAILURE REPORTS". My bad. Also understand that I'm not posting this with any ill will toward ASD. I have the Arc V1 and it runs great in an FM AR9 with a timing shim. That being said...
Is it just me or are there a LOT of reports of problems with the V2 coming up lately. I know new products have "growing pains" but this seems a little excessive considering they had the chance to work out all the bugs with V1.
The most common "fix" for the "obsolete" V1 seems to be to just ask AS Des. for a timing shim, provided the end user has followed all the standard FRT configuration steps.
Looking at the "complaints" for the V1, it seems most of them were pretty superficial, including the 180 deg throw to FRT, supposedly "limited" compatability, selector not feeling crisp, and grinding trigger "feel". [ From: www.artakedowntool.com/blogs/blogs/arc-fire-v2-release-frt-week\ ]
The 180 throw to (let's call it "rapid fire") being "clunky" was, I'm sure, intentional in the AR design. Being a military weapon, it was likely so inexperienced soldiers don't waste all their ammo by accident. The rapid firing mode has to be the result of conscious intent. Same reason the AK "rapid fire" setting is in the middle. In a panic, the soldier slaps off the safety and it goes past "rapid fire" to Semi.
As for "grinding sensation", or "not a crisp selector detent", I sure don't feel that at all.
Regarding "Limited to to AR-15, MCX, MP5, and a handful of others" - Jeez, that's not enough? That's some pretty wide compatability! I'd expect a totally different version JUST for HK MR556/MR762, B&T housings, etc. that are now supported.
I suspect that the attempt at wider compatability may be a big part of what has made it less reliable in the originally supported platforms?
I hope they figure it all out soon, but what do I know? I'm probably completely wrong.
[Chart included below in the first comment]
In my ongoing quest to find a replacement firing pin spring for 9mm bolts that would prevent firing pin bounce, without the need to purchase a titanium firing pin, I purchased 9 candidate springs from Lee Springs. I measured them all in a small selection of very popular bolts (FM, Outerwild, IDL, PSA) and I believe I found the best candidates.
I'll try to keep this brief (lol).
One of the causes of Dead Trigger/Light Strike (DT/LS) SS/FRT failures in 9mm blowback AR's is believed to be "firing pin bounce". As the bolt slams forward and stops, the firing pin continues forward under inertia and it can't get back in place (rearward) in time for the next hammer strike = dead trigger w/ light strike. Using a slightly stronger FP spring or a lighter weight titianium firing pin seems to fix this. The problem is that there is no source for stronger firing pin springs for most 9mm bolts. The UXcell Amazon spring recommended only for older FM bolts with the very weak spring, is only slightly stronger and may not do the trick.
Most FP springs provide about 10-15 oz. of resistance when the spring firing pin is at rest (rearward). We'll call that spring "L1" position. They also provide about 30oz. of resistance at the fully forward position or "L2" position when the firing pin tip is fully forward.
We need a spring that has increased L1 strength while not overdoing it with L2 strength.
For L1, I'm guessing that doubling the resistance at L1 should be more than enough to hold the firing pin in place against inertia to prevent FP bounce.
For L2, I have a bolt that has 100oz. of resistance at L2 position, and it works great, so anything under that should work fine for L2.
Foxtrot Mike has the most "SS/FRT" compatible bolt since the weight does not need to be trimmed, but it also has a slightly different depth firing pin channel, and so needed a different spring than the rest of the bolts.
As a result of my investigation, I think (this is purely a GUESS because I have not tested them live fire yet) the best candidates are the following:
For FM bolts: LC 026BC 08S316
www.leespring.com/product/compression-spring-lc026bc08s316-stainless-steel-type-316
For all others: LC 026BC 09S316
www.leespring.com/product/compression-spring-lc026bc09s316-stainless-steel-type-316
Most 9mm bolts seem to have about L1 = 11-15oz., L2 = 23-30oz. with their stock included springs.
LC 026BC 08S316 in an FM bolt gives about L1 = 30oz., L2 = 50oz. in their firing pin channel.
LC 026BC 09S316 gives about L1 = 30oz., L2 = 50oz. in the other bolts I tested, which seem to have more "classic" firing pin channel dimensions.
These springs would about double the L1 while only increasing L2 by about 60%.
Here's the rub.
Lee springs charges about $9 for these springs bought in small quantities AND charges $6.50 shipping AND $20 handling for anything under $50. One spring would cost about $35. Buying 3 springs costs as much as buying 6 springs (about $54). So this may not be cost effective for most people.
I'll get these springs out for live fire testing as soon as I can.
Once I can confirm that they function normally, we would need a guinea pig who is having DT/LS in a 9mm blowback AR to try the correct spring for their bolt and see if it fixes the problem. IF it does, some enterprising individual/website (not me) could buy them in bulk at very reduced cost and sell them for a profit.
None of this information is a recommendation or guaranteed to be accurate. Try at your own risk.
See OP's first comment below for build list and details.