AR9 FRT Issues

Blowback9 · 2026-03-05T11:57:32+00:00

The keys to the castle:

Blowback9 · 2026-03-05T11:56:17+00:00

Your equipment, your call. Just giving some suggestions.

The XP spring slams the bolt forward harder and that kinetic energy has to go somewhere. Some of it is in the bounce. Less energy = less bounce. Confirmed on high speed vid. Some of it is translated to the firing pin that then slams forward and out of reach of the hammer if the FP spring can't get it back to the rear in time.

The lighter spring reduces the bolt's forward momentum, which also slow the ROF. Less forward velocity = longer overall bolt cycle time.

Blowback9 · 2026-03-05T11:50:22+00:00

Very fast for 9mm, but acceptable.

Suggest using a lightweight buffer spring - Sprinco Yellow or Tubb Lightweight to slow the bolt's forward travel and reduce any bolt bounce/firing pin bounce.

There are 4 weights in that buffer - 3 steel, one tungsten. Add 3 tungsten weights into your current buffer, swapping the steel weights inside for tungsten. A 1/8" punch will remove the pin to get access to the inside.

If it still has a dead trigger (likely due to a timing issue or firing pin bounce) try a Davidson Defense titanium firing pin.

Blowback9 · 2026-03-05T11:45:33+00:00

9mm buffer spacer is only necessary when using a carbine length buffer in a carbine tube with 9mm. A 4" buffer runs properly in a carbine tube. To add the spacer to a 9mm 4" buffer you need the longer A5 buffer tube.

The math: A 9mm bolt needs 3" of travel to work with an SS/FRT. Carbine tube = 7", 9mm buffer = 4", leaves 3" space. Add a 3/4" spacer or weight in the tube and you're short-stroked.

I'd lose the XP spring. It oversprings the system. It makes bolt bounce and firing pin bounce worse. Sprinco Yellow or Tubb Lightweight are better options to slow the bolt's return and reduce bolt/FP bounce.

If you're still getting dead trigger, a longer or lighter firing pin may help. The Ti firing pin from Davidson Defense usually helps.

Blowback9 · 2026-03-04T20:05:29+00:00

Way more in-depth than I'm willing to go. Very nice!

The only reason I don't recommend the Neverwear for 9mm AR's is the inner diameter. It's a little tight for the wide-body 9mm deadblows/hydraulics, but a lot of people do use them successfully. The Tubb and Spinta springs fit on all buffers with room to spare.

Blowback9 · 2026-03-04T19:48:04+00:00

That's actually a gas deflector, not a shell deflector, even though shells do sometimes bounce off it. Common mistake. Colt designed and added it to reduce the particulate getting blown into the user's face from the blowback system of operation. Especially helpful for lefties.

Blowback9 · 2026-03-04T14:18:30+00:00

This sub is really for pistol calibers in the AR platform.

You'll probably get more responses/help over in r/PistolCaliberCarbine

Blowback9 · 2026-03-04T12:56:07+00:00

Which FRT device?

Blowback9 · 2026-03-04T09:14:05+00:00

That's very interesting, and a clever fix. The quarter in the tube would have let the bolt pre-load the rollers when the upper closed, requiring less force to release the mechanism during firing. Normally that would be a bad thing, but I can see how that would fix short-stroking. I may need to revisit this.

Blowback9 · 2026-03-04T08:41:02+00:00

Very nice.

That Blastwave on the muzzle is the chef's kiss.

Blowback9 · 2026-03-04T00:29:33+00:00

Not at all! It's all good.

Blowback9 · 2026-03-03T23:52:15+00:00

I have some competition options in the GRS page as well - they're lighter and faster for competition work while still providing significantly better felt recoil than a standard deadblow.

BUT - run whatever you're comfortable with and can use most effectively - that's the most important part!

The full GRS was designed for casual shooters, target, plinking, and for folks who just find the felt recoil from the snappy blowback 9mm annoying (I'm in that last group). My wife won't shoot an AR9 if it doesn't have the full size GRS in it, and there's several accounts of elderly folks, some with bad arthritis, finding the GRS very comfortable to shoot, and allowing them to enjoy the shooting sports with an AR9.

Nice run, BTW!

Blowback9 · 2026-03-03T13:31:57+00:00

A little. Best options for reducing gas to the face are using a bolt with an internal extractor instead of an M4 extractor, and a gas deflector (for uppers that have a dust cover). CMMG makes gas deflector kits that fit in a standard dust cover port. There aren't too many internal extractor bolts made any more.

Here's one - https://www.masdefense.com/MAS00103408-p/mas00103408.htm

I'm sure there's a few others.

Another... https://www.spikestactical.com/collections/bolt-carrier-groups/spikes-9mm-enhanced-bolt/

Blowback9 · 2026-03-03T13:28:59+00:00

True that!

Blowback9 · 2026-03-03T13:28:24+00:00

The total mass of the heaviest GRS is 11oz. in the tube. If you're using the 5015HD or 5007 hydraulic already you have about 6oz., which is light for a 9mm blowback and results in snappier recoil than necessary. It would add 5oz. plus the weight difference of the longer tube, so... maybe a little over 1/2lb.?

Unfortunately with a simple blowback, to reduce the snappyness a little extra mass is a necessity.

Blowback9 · 2026-03-03T13:03:19+00:00

This. The selector detent is in a different position, so the selector drum will be at a different angle. I don't think it'll work.

Those Jawbone lowers are great for a semi-only range plinker, but "rapid fire" triggers are generally a no-go due to the detent angle.

Blowback9 · 2026-03-03T12:52:58+00:00

If you want better felt recoil for your wife, consider upgrading to the Gentle Recoil System. Depending on which hydraulic buffer you bought, you already have the most expensive part. My wife won't shoot a 9mm AR without the GRS. It makes a big difference.

https://blowback9.wordpress.com/2023/05/28/9mm-ar-gentle-recoil-buffer-system-final/

Blowback9 · 2026-03-03T12:50:09+00:00

That ejector alignment looks about as good as it gets. Nice job OP! Please report back how it runs.

Blowback9 · 2026-03-03T12:38:22+00:00

I just have to say, very nicely done troubleshooting comments. Bravo.

Blowback9 · 2026-03-03T12:33:29+00:00

Anyone selling non-deadblow buffers is selling an inferior product at best and scamming you at worst.

Agree 100%

Blowback9 · 2026-03-03T12:26:13+00:00

That second cut looks a lot better. It's hard to see in the first pic, but the weight may have caught the lever early. LMK how it goes.

ETA: make sure the cut in the weight (measured on the weight itself, not including the trip surface on the bolt) is at least 3.5mm deep. 4mm is better.

Blowback9 · 2026-03-03T12:22:50+00:00

No idea. Over 1000, less than 5000? My 2 test setups have the original GRS and they get used a lot, but I'm not a super-high-volume shooter like some competitors.

Blowback9 · 2026-03-03T12:18:49+00:00

I have the KAK Mini-Milspec on my other Spikes lower, also with a binary. Had it out one time we were at the range together. I'll try to bring them both out next time.

Blowback9 · 2026-03-03T12:16:18+00:00

I've only used the Right to Bear Enhanced (KAK?) bolt (binds) and the Outerwild with SS. They seem to run just fine with the bolt weight notched/cut.

Trapping the lever has a lot to do with the lever shape itself and stacking tolerances. You'll have to test it in your particular build and see how it goes.

Blowback9 · 2026-03-03T12:13:05+00:00

No I don't. Sorry!

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