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Discussion Starter #1
Sometimes the biggest problems looking at Hk parts is the slight differences in an item that seperate it from another similar one. Such might be the case with the M13 version of the 21E. The boltheads may be marked Hk21E - M13 but they may not be so marked. If they are not marked how would one tell if it is an M13 bolthead. Well, looking at the bottom of the bolthead where "the rubber meets the road" so to speak is the key.

In the picture below the bolthead on the right is the M13 one. The other 21E bolthead is made for German non-disintigrating linked ammo belts.



The other M13 difference can be forund in the feed mechanism specifically the sprocket. The distance between the points of the sprocket is smaller than the non-M13 to accomodate the smaller spacing of the M13 links. The sprocket also looks like its tines are "swirled" for want of a better term.



Will post a pic of the other sprocket tomorrow.

There is no difference in the bolt carriers between the two except that some are marked Hk21E - M13

 

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Chuck, will help you out with a few pics

here is a pic of the M13 sprocket in a feed mech



here is a pic of a NON M13 sprocket designed for DM1 belts
 

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Discussion Starter #4
Paul123

I was going to IM you today to see if it would be ok if I used your pics but you beat me to it! Thanks for the addition.
 

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P123 that is a "tweener" sprocket between the DM1 and the M-13.
The first 21E sprocket for DM-1 belts is different.
MM
 

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HKchuck your DM-1 bolt head is a tweener also.
First gen DM-1 bolt heads were flat sharp 90 degree on the "tooth".
See the slight chamfer which later became the large mill cut in the M13.
Some sprocket/bolthead combos will work for both links and some won't at all.
MM
 

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Thank you Chuck, being new to the belt-fed group here everything is a learning process, the passing on of information is one of the very special qualities to be found here on this forum.
 

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P123 that is a "tweener" sprocket between the DM1 and the M-13.
The first 21E sprocket for DM-1 belts is different.
MM
Mike thanks for the clarification, i remember you stateing at one time that there were actually 3 different bolt head / sprocket configureations. i could never figure out what the 3rd type was. i thought it was the change from HK21A1 to HK21E. I have never found anything in HK literature about all 3 types. just the two seperate part numbers for the different feed mechanisams / bolt heads and in the parts that i have had the fortune to have cross my hands i have only seen the M13 marking to indicate a difference, other wise it just said HK21E or HK21a3

would you happen to know at what approxamate date code they started makeing the "tweener" parts??? I imagine the HK21A3 feed mech is prob. for DM1 belts only.

thanks!
 

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OK, went looking at my feed mechs. I noticed a difference with one of them, my newest one. The first pair of pics are what clearly appear to be an M13 sprocket. The second pair of pics, my newest feed mech, I don't know, other than the spokes don't curl to the right, and there appears to be a much larger bevel to the tip of the spoke, on the inside. And, the bevel appears to be different between the left spoke, and the right spoke. Any ideas?






Newest feed mech:



 

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Discussion Starter #11 (Edited)
SudS

I have one that looks like the second set of pics, too. I believe it is the one for the DM belts. If you get your calipers out and measure the outside distance between two consecutive tines you will see that the M13 has a greater difference than the German belt one. I was going to get all my 308 feed mechs together and have a little party and take some pics of them this weekend, been out of town the last few days.
 

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Discussion Starter #12
I have attached a pic of two of the feed mechs below, the one on the left is an Hk 21E feed mech and the one on the right is from the Hk 21A1. Both sprockets are the same but if you look closely at the two mechs you will notice subtle differences between the A1 and the E. The sprocket sits higher in the E feed mech than it does in the A1 and the roller to the left of it is also different.

 
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