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Difference between early and later m1 forends? Will later models fir HK m1S90?


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I have a new-to-me hk marked m1, it's got the very old style Surefire on it (before they were called surefire even!) and I'm not crazy about it, seems heavy for what it is.


I'm considering a factory fore end for it, but I'm having trouble figuring out if it'll fit or not. My serial is m090something iirc. Surefire has a note on their site saying their new weapon lights for that model only fit m1's that are M104800 and above.


I found a guy selling a couple fore ends for a (imo) too high a price but I think they are late model m1.


Do I need to watch for anything or can I buy one of these and make it work? Iirc, there is a note about some models needing two washers or just one.


Thoughts? Anyone have one in a box somewhere?

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There are at least 3 forend versions for the M1 that I am aware of.

Two versions have a longer cutout for the barrel ring lug. Earliest version barrels have a short lug relative to the later versions. The cut-out in the forend is different to accomodate the different length lug. Different lugs:

Short early version on top-



Also, the earliest versions are made to fit a narrower magazine tube at the point where the tube meets the receiver. The magazine is approximately .010" wider at that point on newer guns so if you tried to put a newer forend on your older gun, it would wobble around at the rear. The difference in the cut-out for the newer longer lug shouldn't matter with the older shorter lugged barrel.


All mine have two washers; 1 flat and one "bent".

Edited by truckcop
Brain-fade. Faulty memory.
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Truckcop, thanks for that!


A couple of questions if you don't mind...


By wider you mean the diameter? What is the diameter on the larger or smaller magazine tube? I have no idea if this is an early HK or earliest :)


My barrel has the shorter of the two lugs.


Wait, I'm confused, if the older mag tube is smaller diameter, and you tried to put an old surefire on a new gun, wouldn't the surefire have been too tight vs too loose?


I pulled my surefire forend off, one washer, one wave washer. And ofcourse a round aluminum tube on the end of the surefire with a tapered notch cut out of it that matches up to the barrel.



I'm really thinking of selling the old surefire forend on this and going to a stock one, but I'm not sure what will work yet. I see what you mean about the lug being short not mattering, that's good it seems.

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Yeah, I mis-remembered why I had to do a little fitting to put it on the second gun. I was thinking it was a newer gun but it was an older one as well but the configuration at the point where the tube meets the receiver was a little different causing the aluminum sleeve of the surefire light to wobble around a bit. Forget that part above about the surefire. Suffice it to say, the older guns have the slightly smaller diameter portion of the tube that the forend fits over.

Here's a pic of three different versions of the receivers/tubes. The top is the oldest (probably the same one you have with the full length magazine tube-7 rounds), and the bottom is the newest. The widest part (diameter) of the top two tubes are 1.085". The widest part of the bottom tube is 1.095". A newer forend will not fit your older gun without some sort of spacer to take up that slack. Sorry for the confusion above. I'll edit the Surefire reference out. You can see what I was talking about in the difference between the top tube and the middle tube. They're the same diameter, just a slightly different configuration.



Edited by truckcop
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Those are great pics, thanks! So it seems if I have the top in both examples, I'll need the forearm that will fit the short or long lug (seeing as I have the short, I should be ok) but will be better with the top or middle style mag tube as the diameter on those should be the same?


Does the forearm use that lug on the barrel as a mounting surface? If that's the case I wonder if miss matching a short lug with a long cut forearm will allow wobble?

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I'm having a very difficult time finding an m1 forearm. Ideally I want a low serial and/or HK marked one, I can't seem to find anything.


I have this surefire/LPC forearm, not sure if I should look to trade someone or sell it outright then buy an m1 factory handguard.


It looks simple enough that another shotgun's handguard could be easily modified to make it work, using a piece of alumium like the surefire uses... maybe like an 1100 part, but I don't have the time for that! :)


I'll keep searching around I guess, although what I need is someone that has one in their closet they won't ever use.

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Here's most of what I've got. The two on the left are for a smaller diameter magazine tube. The two on the right are for the larger diameter mag tube. The one on the far right has been modified in the area of the barrel lug to take a later version, longer lugged barrel. Since they were all made for a short barrel lug, the difference you can see is the rear cut-out and the size and spacing of the round holes. The one I referenced on GunBroker looks like the ones on the right so it probably won't fit your gun since it's probably made for a larger diameter mag tube.


Based on your description of your shotgun, you want a forearm that looks like the two on the left. Short lug, smaller diameter mag tube.


That's all I got. Good luck.



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