Modern Sporter UPDATE stock compatibility Oct 31 UPDATE NOV 12th

alberta tactical rifle

alberta tactical rifle

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We just today discovered that buffer tubes for the A2 fixed stock and Magpul UBR do not protrude far enough into the lower to engage the buffer retainer on lowers with serial numbers 000001 to 000224.
On lowers with a higher serial number (2nd production run) this has been corrected and not an issue.

For those who are intending to install a butt stock that employs an A2 or any fixed stock style buffer tube, we have 4 options to correct this problem.
1) Run the rifle without the buffer retainer altogether. Given that the upper slides forward to disconnect from the lower the buffer and spring are not going to cause any problem for takedown like it does on an AR15.

2) Send us your buffer tube and we will modify it for you at no cost. The modification requires taking off about .050" from the ring that locks up against the lower. This WILL leave a very tiny gap between the stock and the lock ring but will not effect the performance of the assembly at all. We will be posting photos as soon as possible so you can see the small cosmetic issue.

3) We will provide a JP Silent Capture System to you at a considerable cost saving. This is likely the best option as it is a far better system than the conventional buffer and spring.

4) Return the lower and we will exchange it for a lower from production run #2 where this issue will not exist. This will mean not having your lower until mid summer of 2019 however, but for those who want to avoid the backdoor registry we can still accommodate this up until C-71 becomes law.

Please contact us at the shop directly should this discovery effect you and you wish to know more about the options.

Sorry guys we thought we had all the bases covered.

November 12th update
We FINALLY got pricing from JP this morning.
Everyone with a lower will receive an email with the information. We need to know how many of these kits we need to get ordered no later than NOON Friday Nov. 23rd 2018
 
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Kornerupine said:
Is that how much the buffer retainer holes are drilled off?
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I'm just taking a wild guess here because I don't have my lowers yet to see what the issue is but perhaps the buffer retainer pin hole was drilled straight down from the edge of the receiver instead of angled back in by the standard 6°?

That alone would be enough to account for the .050" of difference.

I'm only speculating of course, but I've had one other firearm that was drilled straight instead of angled and it caused the exact same issue when I switched to an A2 stock. Still works fine but I have to remember that the spring is going to come out when I take it apart.
 
jiffx2781 said:
I'm just taking a wild guess here because I don't have my lowers yet to see what the issue is but perhaps the buffer retainer pin hole was drilled straight down from the edge of the receiver instead of angled back in by the standard 6°?

That alone would be enough to account for the .050" of difference.

I'm only speculating of course, but I've had one other firearm that was drilled straight instead of angled and it caused the exact same issue when I switched to an A2 stock. Still works fine but I have to remember that the spring is going to come out when I take it apart.
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Being as the Sporter is a direct variant of our Modern Varmint, we employed many of the same dimensions. One of which is the thickness of the rear of the lower where the buffer tube threads in. This area is thicker than a standard AR15 and as a result buffer tubes with a "collar" on them for butting up to the lower do not have enough tube to protrude and retain the buffer retainer. The Modern Varmint has always run the JP buffer system and we missed the fact that we needed to change this dimension when we started the Sporter project.

I am going to delete many of the posts in this thread in an effort to keep this thread for information only.
We are working with JP at the moment on pricing and should have it available later today.

An order for JP will be going into them VERY SOON so we will need numbers as well as payment for the system of your choice, there are 4 options from JP.

PLEASE NOTE THIS OFFER IS ONLY FOR THOSE WHO HAVE PURCHASED EFFECTED LOWERS AND IS LIMITED TO 1 KIT PER LOWER
 
Do you recommend the standard version or the heavy H2 version? Thinking standard version will be perfect for rifle length gas system shooting 223. Please advise.

Also, what are you thoughts on the Alternative Spring Kit? It is worth the $20-30 extra dollars? I have no experience with the JP silent captured spring kit. Thank you.
 
GUNNZ said:
Do you recommend the standard version or the heavy H2 version? Thinking standard version will be perfect for rifle length gas system shooting 223. Please advise.

Also, what are you thoughts on the Alternative Spring Kit? It is worth the $20-30 extra dollars? I have no experience with the JP silent captured spring kit. Thank you.
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I have been running their standard version is rifle length 223 applications for years, and it works just fine. Our MV comes standard with the JP standard system and only a few guys wanting to run truly weird stuff have had any issue and I suspect if they had standard AR buffer and spring would have exactly the same issues.
Avoid weird stuff and you avoid problems it seems.
 
alberta tactical rifle said:
Being as the Sporter is a direct variant of our Modern Varmint, we employed many of the same dimensions. One of which is the thickness of the rear of the lower where the buffer tube threads in. This area is thicker than a standard AR15 and as a result buffer tubes with a "collar" on them for butting up to the lower do not have enough tube to protrude and retain the buffer retainer. The Modern Varmint has always run the JP buffer system and we missed the fact that we needed to change this dimension when we started the Sporter project.

I am going to delete many of the posts in this thread in an effort to keep this thread for information only.
We are working with JP at the moment on pricing and should have it available later today.

An order for JP will be going into them VERY SOON so we will need numbers as well as payment for the system of your choice, there are 4 options from JP.

PLEASE NOTE THIS OFFER IS ONLY FOR THOSE WHO HAVE PURCHASED EFFECTED LOWERS AND IS LIMITED TO 1 KIT PER LOWER
Click to expand...

Is the rear of the lower exactly .050" thicker? If so, some carbine stocks that almost touch the castle nut when collapsed will need to have some plastic filed-off from the face otherwise they won't fully collapse.
 
I will probably be running the JP SCS in mine, but being as it's only .050 thicker, couldn't a person just have that much milled off the back end of the receiver. I realize this would screw up the anodizing, but if a person wanted a permanent solution, would this be viable.
 
KePet said:
I will probably be running the JP SCS in mine, but being as it's only .050 thicker, couldn't a person just have that much milled off the back end of the receiver. I realize this would screw up the anodizing, but if a person wanted a permanent solution, would this be viable.
Click to expand...

Technically yes it would be feasible. It is something we entertained, but there are quite a few lowers out in the world now, there is a high probability that the lowers would get marked slightly in the fixtures and the anodizing would be removed with the material.
The other option we looked at was to mill a pocket in the rear of the lower but then the butt stock would need to be modified.

Given the take down manner of the upper and lower is quite different than an AR, there is no down side to not using the buffer retainer other than the very minor inconvenience of having to push the buffer and spring back inside the tube when you push the upper back to engage the takedown pin.
 
Thanks for the reply Rick. Like I said, I’ll be running a JP SCS in mine anyway - I prefer them, so it’s not a big deal to me. I am in complete agreement with jiffx2781’s comments above.

I’m waiting to see pricing on the JP’s. I’ve got one in my AR right now, and was just going to pull it out for my build (let’s face it, once I’ve got the Modern Sporter the AR isn’t going to get much use). But I might just pick up another one, depending on price
 
jiffx2781 said:
Is this not exactly how the Modern Varmint Factory version works? And I don't recall hearing anyone complaining about it.

I personally don't see this as a big deal but I have to say the fact that you openly admit to making an oversight (read mistake) AND most importantly offer real world solutions to your customers is why the "other" guys aren't even close to being in the same league.
Click to expand...

This. So much this.
 
We had a client bring in a Gen 2 UBR stock today so we could modify the buffer tube to make the tube engage the buffer retainer. I had to take .085" off of the shoulder of the tube to get engagement. Interesting that A2 tubes have more protruding ahead of the threads than these do but nonetheless the UBR tube with the modification worked out charmingly.
Shaun will post some pictures either over the weekend or early next week.
 
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