New T91 12.5

[Cole Dedhand]

Random observations about the T91 12.5 upper.

First, it's heavy. 4.6lb as it comes out of the box.

310_Unboxing.jpg

The bolt looks like an AR bolt except for the lack of gas rings. Most of the dimensions are the same. Except the overall length of the T91 bolt is .010 shorter, and the boss in the back (where the gas rings are in an AR bolt) is the same diameter as the boss behind the extractor pin. (.530) The gas rings on the AR bolt are smaller (.505)

The T91 firing pin is .004" shorter than the AR firing pin from my FailZero bolt.

311_Exploded.jpg

After taking the upper apart and checking out the parts I put it back together and checked headspace. The T91 bolt will close on a no-go (1.4666) with a little force but will not close on a
5.56 field gauge (1.4736).

Out of curiousity I swapped in the FailZero AR bolt in the T91 and the results were the same. Closes on the no-go but does not close on the field. I am NOT saying it is safe to use an AR bolt in the T91. It might work, it might explode. Do so at your own risk.

Obviously the T91 bolt will not fit in the AR carrier.

A BCM Gunfighter charging handle fits and works in the T91.

The T91 optic rail is 0.14" taller than an AR so an absolute co-witness sight becomes a lower 1/3 and a lower 1/3 optic becomes a super-tall sight. This also means that AR rear sights are too tall for a T91 unless you install a super tall front sight post.

The front sight has slight play. Some people may be bothered by this. Me, not so much. I may just remove the front sight anyway depending on what I decide to do for a light.

Once I had given everything the once over and taken some pictures I started modding. First I installed a Holosun HS515GM. I swapped the lower 1/3 QD riser for a PA I had laying around. The QD is nice but just too tall on the T91.

312_Stock.jpg

Then a Strike Industries extended charging handle latch. Fits and works fine.

313_SI Latch.jpg

Next the new and improved M-LOK rail. The rail adds functionality I want but it does take away the personality of the T91 handguard. Some have asked about the play in the old rail design and let me say that is not an issue on this one. The retaining pin took quite a bit of force to install and the rail doesn't move AT ALL. The rail is lighter than the stock handguard which is a nice bonus.

314_Rail.jpg

I added a chopped Magpul MVG (my favorite handstop).

315_MVG Close.jpg

316_MVG.jpg

The rig is not a featherweight but balance is good. With a loaded PMAG the balance point is right at the center of the optic.

I'm undecided on what I'll do for a light. I think Streamlight TLR but haven't picked a mount yet. The ring on the side of the gas block complicates the issue. I wish I could switch it to the other side.

I'm excited to get it to the range.

[Cole Dedhand]

I have tried repeatedly to get my pictures to embed with no success. When I get home I will put them on a different host and just link them here.

[e292644]

Took me awhile to get it fixed. Not sure what's going on but I will report to webmaster.
Sorry about it.

BTW, thanks for the great detail post!

I have tried repeatedly to get my pictures to embed with no success. When I get home I will put them on a different host and just link them here.

[shaocaholica]

You sure that’s a compliant configuration with the VFG?

[Jking81]

You sure that’s a compliant configuration with the VFG?

Why do people keep asking this on the internet? Any AR that is over 26" from the end of the barrel to the end of the bare buffer tube is considered a "firearm" by the ATF when you attach a vertical fore grip. It goes back to being a pistol after you remove the vertical fore grip.

There have been multiple determination letters from our favorite alphabet bureau that clarify that. Also most buffer tubes are 7.25", so if you have a barrel length over 12" generally your over 26". Best to get out a tape measure just in case though.

[Cole Dedhand]

As stated above, this is a "firearm". The OAL is 29" with the brace fully collapsed. A vfg is only a problem if the OAL is less than 26".

Even with the shortest pistol tube the OAL with this upper is 28". Only if you remove the flash hider and use the shortest pistol tube can you get this upper down to 26".

To revise my previous post, it looks like the new uppers come with the tall front post so AR rear sights do work.

But I decided to just remove the front sight and use MBUS sights.

Also I weighed the firearm with a mag full of 75gr ammo and it comes in an oz or 2 under 8lb. As I said, not a featherweight.

Hopefully this picture is a little brighter than the others. When I edit pictures on my laptop and post them online they come out darker.

T91 MBUS.jpg

[Cole Dedhand]

And now for the range report.

I ran ~250 rounds of Wolf Gold (M193 spec), PPU 75gr, and Wolf steel case HP. I've had the steel case laying around for a few years and I decided to try it in the T91.

I used a standard H1 buffer and standard recoil spring.

I was surprised to find the upper is not overgassed. Most uppers and rifles are overgassed out of the box.

Ejection was 4-5 o-clock at 10 feet with the steel case and 15 feet for the brass. This is not an upper for a lefty. I would say a brass deflector would be a good idea.

T91 Ejection.jpg

The bolt reliably locks back on an empty mag.

There is no wear or damage to my buffer tube even though I'm not using an anti-tilt buffer.

I did not shoot groups off the bench so I can't give the accuracy in MOA. I'll just say it was hitting where I put the dot.

I had 2 failures. 1 fail to eject with the steel case and 1 fail to feed with the 75gr using an off-brand magazine.

The MLOK rail gives good heat protection. I fired 2 magazines in under a minute and the rail did not get uncomfortably warm even though the barrel and gas block were smoking.

I did notice slight play in the bottom half of the handguard. It fits in grooves in the upper half and the upper half is the part that's held by the retaining pin. The lower half is held by 2 screws at the back. So the lower half can move slightly within the grooves at the front. Maybe 2 more screws at the front wouldn't be a bad idea.

I checked headspace again when I got home. Not that I expected any problem. Still doesn't come close to closing on a field gauge.

I blame a crappy magazine and crap ammo for the failures I had. I'm not ready to stake my life on it yet but it was 100% reliable with brass cased ammo using PMAGs today. If that holds true for a few hundred more rounds I'll call it good.

[Cole Dedhand]

Another trip to the range. Using PMAGs and Wolf Gold M193 spec ammo function was flawless through 200 rounds.