8.6 Blackout? Need help with feeding

[tammons]

4.27" stagger feed short action.
I bought a Shaw 8.6 BO barrel when they were on sale and finally got around to setting it up.
However, I am having problems getting it to feed. Before this barrel, it was a 6.5 creedmor or 7mm-08 and both of those fed fine.
At first the magazine feed lips were too straight and the bullet nose was jamming and not hitting the ramp.
So I bent the lips up slightly mostly towards the front and kept the lips as straight as possible.
That helped and it will feed the 1st cartridge of 4, but it wont feed the 2nd cartridge.

The 8.6 BO shoulder is so far back, that when I try to cycle the 2nd round, it tilts on corner of the shoulder pinned between the cartridge underneath and the feed lips and never fully seats on the lips. So the bolt rides over it. I can push the nose down so that the bolt will catch it, but then it nose dives. If I push the back down the bolt will miss the case head and ride over it.

Any suggestions?
All are welcome.

[Dave Hoback]

Well, the 6.5CR & 7mm-08 were meant to be fired through the standard mag box/follower/spring setup. The 8.6BLK was not. You’ve zeroed in on the cause of the condition. The issue now is simply getting the mag to work.

Let me ask, what are you using to adjust the feed lips? If you are prying the lips with a screwdriver or bending them with standard pliers, this is part of the problem. It’s not very good adjusting the feed lips evenly that way. I recommend you have one of these tools below first. Also, it may be possible that more spring is needed. Or the follower may need to be shaped a bit different. Magazine adjustment & modification is an art form. LOL!

This is the correct tool. Magazine Feed Lip Adjusting Tool. There are many different available but this is a simple inexpensive option.
https://masterpiecearms.com/shop/mpa-mag-feed-lip-adjustment-tool/

These also work. They are Sheet Metal Pliers.
https://www.amazon.com/IRWIN-VISE-GRIP-Original-Locking-23/dp/B0000TFGFU/ref=sr_1_2?crid=N5ELXD1O11BR&keywords=Flat+Sheet+Metal+pliers&qid=1699396099&s=industrial&sprefix=flat+sheet+metal+pliers%2Cindustrial%2C109&sr=1-2

[tammons]

If Shaw had a faster than 10 twist 338 barrel I would have bought a 338 federal barrel instead.
All these years and I didnt know they made a tool for adjusting feed lips, LOL. Never had a problem before doing a minor tweak.
No screwdriver and no pliars.
I have it cycling 2-3 shells now, but I dont think simply bending the feed lips more will fix the problem. But maybe it will, who knows.
Anyway, the issue seems to be the way the shells stack in the magazine when more than two.
I think they need to stack perfectly square, but then the bullet will hit below the ramp.

Thanks for the help.

[Dave Hoback]

No, I didn’t say simply bending the feed lips would do it. I expounded on possibly needing more spring tension and/or modification to the shape of the follower. As I said, modifying magazines to feed different cartridges is an Art Form.

Don’t feel bad. Even the AR guys are having problems getting the 8.6BLK to feed properly from the magazines. Just look at some pictures of different Cartridges magazines. The differences in length & height of the feed lips as well as the shapes of the followers. There’s a reason they are different.

[tammons]

The 1st cartridge seats correctly.
The 2nd is close to seating correctly, but rocks only very slightly.
The 3rd cartridge rocks more.
The 4th even more.
If I remember correctly, I had similar feeding problems with a 338-284 I built and eventually was able to get that corrected but it was a real PIA.
Now I think the follower is just as much of a problem.
However, last time I tried to modify a follower, it was a huge fail.
Thanks for the help.

[sharpshooter]

You need a .223 magazine.

[Dave Hoback]

You need a .223 magazine.


8.6mm BLK on the right, 223 on the left. 223 magazine? No, I don’t believe so. Perhaps confusing with 300AAC, or blackout?
https://i.ibb.co/S7jJ54F/108-F8-CB3-4862-4307-8-D33-FC8-D7173-E94-E.jpg (https://imgbb.com/)

[tammons]

My opinion now after looking at some 6mmBR magazine modifications is the center of the spring is too far forward.

[sharpshooter]

My bad....I thought that it was based on a 6.8 Rem case.

[Dave Hoback]

Actually many people call it 8.6mm Creedmoor because the 6.5 Creedmoor is a popular parent case for it. And it’s basically the same COAL once those huge 338 pills are added.

[tammons]

I gave up on the savage internal magazine and switched to a stock that takes AICS magazines.
The 308 MDT/AICS magazine feeds the 8.6 BO fine.
Also going to try a Pmag.

[Dave Hoback]

Nice! Always the best option IMO. I use the Magpul AICS mags. They work flawless. I did have to sand the polymer locking tab on the mag a bit, for correct mag lock seating. Perfect since. I also sanded the inside edges some to accept 2.900” COAL.

[tammons]

Expensive solution to fix a $20 problem - LOL.

Actually after checking the shells in the AICS magazine alone, to me this looks like a bad cartridge design.
The Shoulder needs to be about 1/4-1/3" farther out and that would probably fix all of the feeding problems.
As is, the case from base to shoulder is roughly half the length of the round, and when stripping out of the magazine the base rides over the shoulder of the cartridge underneath and tips the nose down before it clears the feed lips.
In a factory Savage SF magazine I think the riding over the shoulder before reaching the ramp was the main issue.
Now mounted in an Oryx chassis, the nose of the bullet hits the feed ramp before the base rides over the shoulder so it works.

If this Oryx/AICS attempt would have failed, I planned to sell this barrel and ammo and have a 338 federal fast twist barrel made.

But since it is working well enough, I think I will keep it.

[Dave Hoback]

Well, that was a choice on your part. Just as was getting into this new cartridge. But going AICS was a necessity. The stock setup could have worked with the proper adjustments/modifications. However, yes, going AICS is easiest and best in the long run. There is a reason the AICS is so widely used…because it just works.But these problems should be contemplated when getting into these Fan Boy cartridges. Next we’ll likely have 9mm cases with heavy 30cal pills & 45ACP cases with high BC 416 bullets!

OH, Oh, I know…. I’m going to make a Wildcat that uses a just a PRIMER…., stuck on the back of a 220gr 7mm Bronze solid bullet! Oh… and the Primer will have a 30 degree shoulder. LOL!

[Nor Cal Mikie]

Go "single shot/feed". Problem solved!! If you can't hit your target with the first shot.........?

[tammons]

Well, that was a choice on your part. Just as was getting into this new cartridge. But going AICS was a necessity. The stock setup could have worked with the proper adjustments/modifications. However, yes, going AICS is easiest and best in the long run. There is a reason the AICS is so widely used…because it just works.But these problems should be contemplated when getting into these Fan Boy cartridges. Next we’ll likely have 9mm cases with heavy 30cal pills & 45ACP cases with high BC 416 bullets!

OH, Oh, I know…. I’m going to make a Wildcat that uses a just a PRIMER…., stuck on the back of a 220gr 7mm Bronze solid bullet! Oh… and the Primer will have a 30 degree shoulder. LOL!

I seriously doubt that the stagger feed mag would ever feed more than 2-3 8.6bo shells without modification.

I had a short barreled 338-284 and it was one the best hardest hitting hunting round with moderate recoil I have ever used.

Years ago, at first was a 338 Federal barrel soon to be reamed out to a 338-284 (338-284 reamer will completely clean up a 338 fed barrel without setting the barrel back). So I ended up with a 338-284, 19" barrel, savage short action. Great truck gun and a sledge hammer. Used it for a couple of years and sold the barrel when I set up a 9.3x62 Mauser. Bought it back again and used it for a while and got tired of the make your own brass thing. Really not that difficult, but I sold it again.

And since then I have wanted another 338. And looking for a bit more punch over a 300 BO for subsonic (which I also have), I thought the 8.6bo might be worth a try since I got a barrel pretty darn cheap from Shaw.
You can buy 8.6 ammo, and you can buy 8.6 brass so it all sounded good, except the 3 twist. I wish it was a 7 or 8 twist. Three twist is too fast for supersonic loads.
I also have a 277 wolverine and ammo for it is harder to find than 8.6 not that it matters.

Anyway, in the future I may dump the 8.6 and go with a fast twist 338 fed or maybe a fast twist 338-284 barrel and make up a snot load of brass if I go 338-284.

[tammons]

Go "single shot/feed". Problem solved!! If you can't hit your target with the first shot.........?

Single shot is okay until you need a rapid followup shot.
Anyway, it is running fine.