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 XM-607 Buttstock 30-day review and *100-day UPDATE*
uxb  [Team Member]
11/23/2008 11:50:56 AM EDT
I received a beta tester buttstock 30 days ago from TSI.

I've had the opportunity to evaluate the fit and function as well as the endurance and durability of the buttstock in the past month.

I've put more than 800 rounds through the 607 using the new buttstock, falling short of my 1000 round goal due to time and weather.

Overall the quality of parts and finish is exceptional. There are a few minor issues that I'll address further in the post with pics for detail. Synopsis to follow after photos and comments.

In addition to a review, this will also be a comparison to the first generation of TSI 607 buttstocks.

Photo 1:

First generation (FG) buttstock on the left, Current Generation (CG) on the right.

The FG buttstock was originally machined from a single billet of aluminum. The CG buttstock is cast from a mold. The type of aluminum in the FG was not compatible with anodizing and was coated with moly resin. The CG has all aluminum parts hardcoat anodized by US Anodizing. This provides a protective surface and also strengthens the aluminum and minimizes wear. A significant improvement IMHO.

You will notice on the CG, the contour of the butt plate at the bottom has a stronger radius below the O and L markings. This is patterned more closely to the original XM-607 buttstock. There are also changes to the washer and screw for the locking lever. This will be shown more in detail later.

Photo 2:

FG buttstock on top, CG buttstock on bottom.

The main difference here is in the profile and thickness of the receiver end plate. The FG receiver end plate was thicker and flattened on top for clearance of the charging handle. The CG receiver end plate is now the same thickness as an original CAR-15 receiver end plate and does not require the flattened area for clearance. I think this is more aesthetically pleasing.

Photo 3:

This is a shot of the left side of the CG buttstock end plate.

There is a minor surface flaw. It's a diagonal line-like indentation about mid-way down. One of the other beta-testers noticed the same mark on his receiver end plate, which leads me to think it was from the casting process.

Photo 4:

CG on left, FG on right. A known issue identified previously by Ed––shown here in both generations of buttstock––is that the sling swivel stud is not perpendicular to the axis of the buttstock. This is not an issue that bothers me, but I believe Ed will be addressing this in future.

Photos 5, 6 and 7:

CG on left, FG on right.

From the TSI website FAQ:

The Outer Locking Tube lip diameter was reduced so the Tube isn't visible from the outside.

Here you see pictures of this detail. I like the fact that the fiberglass shell is rebated to accept the outer locking tube lip. When closed this provides a very clean appearance because the lip is no longer visible.

I had some concerns about the fragility of the fiberglass surrounding the outer locking tube lip because it's so thin, but I believe this to be unwarranted. It hasn't cracked, split, chipped or shown any other type of defect. Granted I haven't given this buttstock serious abuse, but I don't intend to, and I doubt most retro builders will use this to knock down doors for CQB entry. The fiberglass on the CG is actually thicker than on the FG because the lip is smaller.

Photo 8:

CG locking lever:

This is the second minor casting flaw that I have noted with this buttstock. The part of the lever closest to us shows a defect that looks about the size of an eyelash that could have fallen into the mold. I have no idea what this is, but it also appears in 45bravo's photos of his lever.

Okay now for the good stuff:

The fit and operation of the lever is exceptional. An improvement IMO is the rebating of the washer and screw that allow them to fit flush with the surface of the locking lever, as shown in this photo, as compared with the FG in photo 9, below. Again, this is probably just an aesthetic issue, but to the retro purists, little things count.

Photo 9:

FG locking lever

Photos 10 and 11:

CG in center, FG at top.

This shows the outer locking tube and the new one-piece buffer tube in place on the receiver with the buttstock removed. In the first pic we see the outer locking tube extended as if opening the buttstock. As you will see, it is not fully open. This is the point at which, on the CG, the outer locking tube begins to bind on the locking pin when opening, making opening a little difficult. You have to apply quite a bit of force to get it to open fully.

In photo 11, this shows the same CG outer locking tube in the closed position. This also would bind when closing, about the same distance from the closed end. The binding on closing has resolved itself in the last 30 days from repeated opening and closing.

The binding on opening has improved, but not resolved as yet.

Both ends of the locking channel narrow a few thousandths of an inch before the 90 degree bend for the locked positions. I would prefer it be a few thousandths of an inch too narrow and wear into a fit than to be a few thousandths too wide and always be sloppy.

Photo 12:

FG TSI stock showing the two-piece welded buffer tube:

From the TSI website FAQ:

The Buffer Tube was changed to a one piece tube instead of a welded two piece to increase strength and reduce labor.

The new one-piece tube is one of the best improvements to this stock as far as strength and dependability. There were known instances of the FG buffer tube failing during auto-fire, requiring replacement. I don't expect this from the new one-piece tube in the CG.

Photo 13:

The CG buttstock in action:


This is a well-planned and well-executed offering. The engineering and construction is first-rate as well as the quality of the materials.

Parkerizing and anodizing are even and durable with minor wear shown on inner locking rod in the past month.

The cast locking lever and buttstock endplate are solid and the raised lettering for the "O" and "L" are both crisp and even and properly located. Minor casting flaws noted above are the only issue I have seen, and as said, are minor and neither affect the strength or function.

Given the variances in the widths of production fiberglass shells, I am impressed also by the fit off the buttstock endplate in relation to the buttstock. Smooth and even most of the way around with very little "overhang" of the fiberglass.

The stock is user-friendly in both installation and operation. The difficulty in fully extending and closing the buttstock was tough at first but seems to be resolving. It closes fine now with no resistance, and the resistance on opening has improved and I expect it to resolve as I continue to use it.

The locking lever is easily manipulated with one hand, even when wearing gloves. The operation is very precise, with no sloppiness, and locking in open or closed position is very positive and does not move even after extended periods of fire. When fully extended and locked the buttstock can be moved forward and back about 1/32 of an inch and is noticeable at first, but you get where you no longer notice it pretty quick. There is no rotational movement of the buttstock and in the closed position it is as solid as a rock.

For those wanting to pursue an XM-607 build I believe this is what you have been waiting for. Quality materials and workmanship that are as close to an original XM-607 build as you can get without modification of your receiver.

Stout, robust, durable, dependable and reliable. And, importantly, soon to be available.

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Dawg180  [Member]
11/23/2008 12:23:50 PM EDT
Did you try buttstroking a small man in black pajamas armed with an AK?

Looks fantastic, if only SBR were allow in Illinois I would be all over one of those!
MarkRSims  [Member]
11/23/2008 12:43:54 PM EDT
Originally Posted By Dawg180:

Looks fantastic, if only SBR were allow in Illinois I would be all over one of those!

Iowa too. Good comprehensive review. Thanks, uxb!

AR-Head  [Member]
11/23/2008 1:08:32 PM EDT
Do you know when they go on sale?
MACVSOG  [Team Member]
11/23/2008 1:35:21 PM EDT
I have one of the first generation stocks, and your review is just what I wanted to know, i.e. how does the currrent generation compare in quality fo the first generation. It sounds like the new stock is an improvement. Too bad about the casting flaws and the binding of the stock, but maybe these issues can be addressed as they move along in production. I really like that now the buttplates can be anodized. That will make the finish hold up better than the first generation stocks. Prices are still reasonable. Looks like I will have to get some more of the new stocks.

Charles Tatum
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MarkRSims  [Member]
11/23/2008 1:48:45 PM EDT

1) Do you think some dry lube or grease would help with the binding?

2) In Pic #8, it looks like you had to put a lot of torque to the latch bolt to remove it. Should this be a harder piece of steel? If you would need to lube the latch tube, you might need to remove this periodically for cleaning/reapplication.
WA-Tom  [Member]
11/23/2008 2:29:06 PM EDT

Thanks for the input! I too beleive that the newer stocks are better than the ones I did alone. But you may have to factor in some bias.....
postino  [Team Member]
11/23/2008 2:32:14 PM EDT
Just an off-the-wall question...I notice you have triangular changing handles on that correct for the XM607???
ranchhand  [Member]
11/23/2008 3:10:23 PM EDT
I had an original and loved it. The rear of the buffer tube blew out but it seems that that will no longer be an issue with the new tube
uxb  [Team Member]
11/23/2008 3:54:10 PM EDT
Originally Posted By MarkRSims:

1) Do you think some dry lube or grease would help with the binding?

2) In Pic #8, it looks like you had to put a lot of torque to the latch bolt to remove it. Should this be a harder piece of steel? If you would need to lube the latch tube, you might need to remove this periodically for cleaning/reapplication.

1) Actually a little work with a rat tail file and some emery cloth should cure it right up, but as a beta-tester I was reluctant to make any modifications on my own. Right now for the lube I am using LaRue Machinegun Lube and it is smooth right up to the point where it starts to bind. But again, it is probably 70% improved since I started with it a month ago. Considering the amount of trigger time I have put through it I actually haven't cycled it through open/closed as much as it probably needed.

2) I used steady pressure to remove the latch screw and didn't really force it. I also tried not to over-tighten it either. I do not know the hardness of that screw, but I may take it to Diamond Machine and Screw this week and see what they say. I may buy a few spares as needed.

uxb  [Team Member]
11/23/2008 3:55:06 PM EDT
Originally Posted By postino:
Just an off-the-wall question...I notice you have triangular changing handles on that correct for the XM607???

It is shown in The Black Rifle with both types of charging handles.
postino  [Team Member]
11/23/2008 4:43:19 PM EDT
Originally Posted By uxb:
Originally Posted By postino:
Just an off-the-wall question...I notice you have triangular changing handles on that correct for the XM607???

It is shown in The Black Rifle with both types of charging handles.

I hadn't noticed that, but looking, I see on pg 177 that it does indeed show two different CH's...and two different handguards, and different lower receivers...waffle mags, and sawed-off grips...

Do you know what that odd hole in the upper buttstock (in the pic) is for??? It looks like a metal rimmed hole of some kind...
coctailer  [Moderator]
11/23/2008 4:46:25 PM EDT
Great review UXB!!!

If this economy ever turns around I'm all over a 607 stock. I have everything else to build one.

Hopefully they arent $1,700 by then
edwin247  [Team Member]
11/23/2008 6:18:31 PM EDT
Great unbiased review.

Some of you may or may not know this, but I teamed up with Tom to get his Bolt On Version back on the Market, and this is an example of our venture.

Couple Notes that I would like to make about this review.

1. The tightness in the the slots on opening and closing of the stock is due to the heat treating of the slots. The entire tube was heat treated, and during the process you could visually see the slots deform during this process. As this is one of the first three that went to users, I was/am aware of this problem, and I hope to correct this problem with a more localized heat treat to the ends of the slots versus the whole tube. Tom has also instructed me that the tubes need to be hand fitted to insure smooth operation. I was hoping to eliminate as much "hand" finishing as possible to reduce labor costs.

2. Casting imperfections: This is an investment cast process, so there may be minor cast imperfections that I can do nothing about. I think the imperfections that UXB has highlighted will be a good example of what you will get with these castings. I was in hopes that a casting process would match the original Colt XM607 stock better than a CNC machined part. I will have to check with the other castings to see if the same imperfections are present. You can notice from the picture of an original stock that there are imperfections with Colts stock too. I am not sure why type of a casting process they used or if it was a forge (I doubt it was forged).

3. Sling Swivel: The swivels were drilled at an angle by acident. It was definately my mistake. Tom sent me a drilling jig to drill these holes at the appropriate depth, but unfortunately if the jig isn't properly parallel with the stock itself then it drills at an angle as shown by UXB. This problem was noticed in the first few stocks I assembled, and a correction is already in the works. So rest assured that the swivel will be square to the stock.

4. Accepting orders on Dec. 8th.

Thanks again UXB for your write is definately appreciated. P.S. if you have video I could host the files.
WA-Tom  [Member]
11/23/2008 9:24:37 PM EDT
I think to get 100% non distortion on the locking tube it would have to be heat treated prior to any machining and that would truly jack up the prices for the work significantly. I am honestly not sure what the original Colt 607 used for it's locking tube. It was probably steel but I am not sure anymore. In any case Ed has done a hell of a job on these. FYI I have heard a rumor that a freind is supposed to be able to wire up my lathe in about a week or two. If he doesn't I am going to go hire someone and get er done.
Tumerboy  [Member]
11/24/2008 6:23:20 AM EDT
Great work guys! Thanks UBX for the review.

My order is inbound.
uxb  [Team Member]
2/2/2009 11:35:12 AM EDT
100-day update:

Okay, Friday was Day 100 but with the ice storm I was not able to get on the internet at home (and probably won't have connection at home until Tuesday or Wednesday).

Day 100 impressions:

Round count now right at 1350 rounds

Initial binding issues upon receipt and at 30 days are completely resolved. Stock opens and closes with positive friction and no play.

Lock-up when opened and closed has not loosened over time and is still solid as the day it was received. No play in the lever and only minimal wear on the buffer tube from opening and closing the stock.

Anodizing on the buttplate has shown no appreciable wear.

No cracking or deformation of the stock shell which was exposed to extended periods of sub-zero cold and temps near 100 degrees.

Have been quite impressed with this endeavor and will update again at 6 months of use.

More info at TSI, Inc.

I would also like to add that I see a possible market for a "retro-fit" kit (no pun intended) that would allow owners of the original stocks to be able to purchase a current generation buttplate and lever only as replacement parts for their first generation TSI buttstocks.

Just a thought...

edwin247  [Team Member]
2/2/2009 2:47:38 PM EDT
Nice!!! I am glad everything is "jell - ing" together as I thought it would.

To get the older TSI stocks to work with the newer design you would have to change the Reciever End Plate and the Buffer Tube at a minimum. You could change the Inner Locking Rod so you wouldn't have to modify WA-Tom's Inner Locking Rod, but this isn't required. You will at least have to modify the Inner Locking Rod of Tom's version as it has a Pin versus a Flat spot on the new design. What I really need to do is....list all the parts seperately on the TSI website so people can pick and choose what parts they want to convert over. Give me some time to work on this.

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