Possible 20 rd Grendel Mags?

[Buster]

In no way am I trying to dispute SG4247 findings but merely validating, from my end, and satisfying my mechanical curiosity (BTW, he's absolutely correct in his findings):









I think I'm going to try what SG4247 did and put the blue Grendel follower in the 20 rd mag and see what happens..

[Buster]

After attempting to swap the followers I noticed the subtle differences between the two (Grendel mag on top):

Bigger deeper roll first roll (left-to-right) in the Grendel mag, second roll is wider and deeper on the 7.62x39 mag, third roll is about the same:

[Buster]

Followers:


Grendel on left, 7.62x39 on right:

[NugginFutz]

After attempting to swap the followers I noticed the subtle differences between the two (Grendel mag on top):

Bigger deeper roll first roll (left-to-right) in the Grendel mag, second roll is wider and deeper on the 7.62x39 mag, third roll is about the same:

Makes sense - 1st is deeper on the Grrr mag for the smaller caliber, second is deeper on the 7.62x39 due to more sharply tapered case. Both have similar case heads, so the third rib is similar.

Followers are likely contoured the same, so not likely interchangeable.

20-20 Hindsight! ℃ↂ_ↂↃ

Thanks for sharing your results.

[SG4247]

Thanks for posting Buster, just got home from work late. Haven't had time for pics or posts.

I observed that the followers are clearanced for different roll widths and depths as you noted. The 6.5 follower actually travels fine in the 7.62 mag body. The issue I had was that the 6.5 follower did not have the right spring seat for the new 7.62 flat wire spring. I made tweaks to the flat spring until it seated okay on the 6.5 follower. Then I assembled the mag.

The next step is to cut one coil at a time until my recoil spring will strip the first few rounds. I also noticed the brass neck is possibly catching the edge of the mag. This could be clearanced. Hopefully shortening the spring will not affect the last few rounds coming out of the mag.

I will have this done tomorrow.

[SG4247]

After many hours of work, I was able to make the 20 rnd 7.62 mag work perfectly in my Grendel rifle. I kept the silent spring installed, unmodified.

Basically the steps were:

1. Use a blue 6.5 follower, and cut 1/8" of both legs. The blue follower is longer than the black follower. A shorter follower gives more space in the mag for bullet cases.
2. Trim the small metal tabs that retain the mag floor plate with a dremel tool. So that the blue follower installs and removes in the mag body without issue.
3. Use the original flat 7.62 20 rnd mag spring without any modifications. Tweak it slightly if needed to keep it seated in the blue follower.
4. Just trim the right side opening (near the lips) of the mag with the dremel. Make it look just like the 6.5 grendel mag opening from ASC. If you skip this step, the Grendel case will drag and bind on the side of the opening when the bolt strips the round out.

That's it. Works like a champ. 20 full Grendel rounds in a short mag. Shot 60 rounds yesterday (3 full mags) with no issues.

I can post pics if anyone is interested.

[KentuckyBuddha]

I can say without fear of contradiction that at least one person is interested. : )

[LRRPF52]

I just noticed that ASC makes a 15rd curved mag that is available through 44mag.com:

http://www.44mag.com/product/1229/6_5_grendel_ar15_magazines

It just has a limiting dent peened into the mag body to prevent the follower from depressing any deeper into the magazine.

I like the idea of a hybrid magazine with a steel body and lips up in the upper portion of the magazine that inserts into the magwell, with a polymer lower body that is wider than current AR15 mags. Kinda like a Lancer, but wide enough to allow correct stacking of Grendel cartridges, along with more internal OAL allowance for those that want to push the COL out a little. PRI or HK type mag body construction would take care of that, rather than overlapping and spot welding.

We've discussed this several times over the years. That said, the current magazines have never given me trouble, as long as I don't load more than 10rds in the straight "17rd" mags from CProducts.

[Buster]

I can post pics if anyone is interested.

I think it would be a welcomed addition to your detailed instructions.
Good job!!

[SG4247]

In our local steel plate competition, we have one course of fire that is:

5 shots at 300m
5 shots at 200m
5 shots at 150m
5 shots at 100m

20 rounds total highest score in fastest time is the winner. One has to shoot 20x20 all four distances, in 47-55 seconds to win the course!

Cant compete if you have to change mags!

Hence my interest in a functional 20 rounder, that will not drag on the bench when the rifle is on a bi-pod or a sand bag.

I will work up some photos tonight.

[SG4247]

Basically the steps I used were:

1. Using a stock blue 6.5 follower, I cut 1/8" off of both legs of the follower. The blue 6.5 follower is much longer than the black 7.62 follower. A shorter follower gives more space in the mag for bullet cases. Cut the blue follower down to .920"-.950" as shown by the caliper.
IMG_2972.jpg
IMG_2969.jpg
2. Next trim and shape the two small metal tabs on the 7.62 mag that retain the mag floor plate with a dremel tool. This is so that the blue follower installs and removes in the mag body without issue. The two metal tabs just need to clear the follower for installation and removal. Do not bend any of the metal tabs, they will break.
IMG_2980.jpg
IMG_2985.jpg
3. Use the original flat 7.62 20 rnd mag spring without any modifications. Tweak it slightly if needed to keep it seated in the blue follower. Spring orientation is important, install the spring into the follower exactly as shown. If you reverse the spring orientation, it may bind on the mag interior.
IMG_2968.jpg
4. Just slightly grind the right side opening (near the lips) of the mag with the dremel tool. Make it look just like the 6.5 grendel mag opening from ASC. If you skip this step, the Grendel case will drag and bind on the side of the opening when the bolt strips the round out of the mag. The modified 7.62 mag is shown on the top and the 6.5 mag is on the bottom. Use the 6.5 mag as a reference when grinding the 7.62 mag.
IMG_2981.jpg
5. Lube the mag interior with your favorite oil. Put the follower and spring assembly in the housing and install the mag floor plate.
IMG_2988.jpg
6. Using a long tool (like a big screwdriver), and with the mag on the bench top, push the blue follower through its full range of travel making sure it travels freely, and that the spring does not bind anywhere in the mag housing. If it binds, correct that issue.
7. Load 20 (dummy) rounds, install the mag in your rifle, and manually exercise the action to see if the rifle will feed, chamber and extract all 20 rounds without issues.
IMG_2999.jpg

Seemed to work great for me!

[usmc1371]

Great info and pics.

[Buster]

I finally performed the magazine mod that SG4247 figured out (above) and it works like a champ!
Tried it in 2 different Grendels,,,worked reliably every time.

[KentuckyBuddha]

I guess I know what I will be doing with a significant amount of my free time! Thanks very much indeed for the info.

[SG4247]

Good to hear!

Since my post, I have performed this mod on a pile of 20 rnd 7.62 x 39 mags from ASC for several Grendel owners.

All have performed without issue.