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Old 05-19-2018, 12:33 PM   #1
Cole Dedhand
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Default T91 12.5 Upper Review

Random observations about the T91 12.5 upper.

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

http://picpaste.novarata.net/pics/88...8f8269bcad.jpg

The upper fits and functions (hand cycling) on my Anderson pistol lower. Pins line up. Bolt locks back on an empty mag.

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.

http://picpaste.novarata.net/pics/98...5090c1db5e.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 curiosity 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. EDIT: Looks like the new uppers are coming with the tall front sight post so AR rear sights do work.

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. The front sight also has slight cant. Another reason to just remove it. EDIT: Yeah I removed it and put on some Magpul MBUS sights.

http://picpaste.novarata.net/pics/12...b61512215a.jpg

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. I got a really good deal on the HS515GM and so far I like
it. I'm not going to abuse it and try to break it deliberately but for me the added durability of the beefier housing and 7075 aluminum of
the "military" model is nice to have for only a few bucks more than the standard model.

Next the new and improved M-LOK rail (available from T91tactical.com when it's in stock). 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.

http://picpaste.novarata.net/pics/43...426d5ef986.jpg


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


http://picpaste.novarata.net/pics/bb...c69b348283.jpg


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


http://picpaste.novarata.net/pics/75...f9613c694e.jpg


http://picpaste.novarata.net/pics/9a...c9e93fcb50.jpg

The rig is not a featherweight (7lb 14oz with pmag full of 75gr) but balance is good. With loaded mag 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'll give more info once I've put some rounds through it.

EDIT: Removed the front sight and installed MBUS sights. This required removing the handguard since the MBUS sights slide on and both ends of the rail are blocked when installed.

http://picpaste.novarata.net/pics/3b...19700ebafc.jpg
.

Last edited by nalioth; 05-19-2018 at 07:56 PM. Reason: Fixed huge image(s)
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Old 05-19-2018, 07:53 PM   #2
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Nice review. Hopefully you won't get a bubba asking about the legality of a vertical grip like they do on the T91 forum.
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Old 05-19-2018, 07:55 PM   #3
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Have you had any play in your handguards? I have six hundred rounds on my T91 since I put in the Mlok handguard but I found they haven't moved at all.
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Old 05-20-2018, 08:29 PM   #4
Cole Dedhand
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And now for the range report.

I ran ~250 rounds of Wolf Gold (M193 spec), PPU 75gr, and Wolf steel case HP. I don't normally shoot steel 223 but I've had this stuff 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.



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 handguard 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.

http://picpaste.novarata.net/pics/4c...6c490ddb18.jpg

Last edited by nalioth; 05-20-2018 at 08:55 PM. Reason: Fixed huge image(s)
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Old 05-21-2018, 12:06 AM   #5
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You may be aware of this but,
Be advised these are notorious for malfunction with steel case until 300-500 rounds of brass have been fired through them.
OP try some Tulammo. Single shot, every round.
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Old 05-21-2018, 02:54 PM   #6
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So I just got done at the range now my 12" upper has 1500 rds through it with all but 230 of it m193. I figured I'd test the accuracy of the upper so I put on a Leupold mk4 on top of it to test the accuracy of the barrel.

Full disclosure I did not have a match trigger in it. Instead I had a BCM pnt trigger in the lower.

I had four different ammo brands and weights with me and I shot to a hundred meters. First was Hornady 75 gr steel match. My best group was 1.21" and my worst was 1.72".

Second ammo was Federal xm193 at 55 gr. My best group was 2.2" and my worst was 3.67".

Third ammo was PMC xtac 62 gr. My best group was 1.79" and my worst was 3.1".

Forth ammo was Tulla 55 gr. This ammo is the only the only ammo so far that has given me any failures. I had two FTF our of 20 rounds. My best group was 2.6" and my worst was 4.2".

I have run a H3 buffer in the lower that it's on since the first round and it runs like a champ. When running it hard and fast it feels as smooth as a full size rifle. As I said above have had only two failures but they were both from Tulla being underpowered ammo.

I swapped out the H3 buffer for a regular weight carbine buffer and it ran fine afterwards with the other twenty round box of Tulla I had with me.
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