Home Forums Hunting & Shooting AR and Tactical Rifles M4 feedramps and larger calibers?

Hmmm. Was messing with an AR15 in 7.62x39 and having issues with a particular cartridge loaded with a soft round nose bullet. Figured opening the feedramps up would help. BTW have since decided to avoid this particular load in the AR...

Fast forward, decided to ask here about considerations with feedramps and the larger diameter cartridges. What's the scoop? Have 6ARC, 6.5 Grendel, 7.62x39, and thinking of a 300 BO and maybe a 350 Legend.

Appreciate any input or cross discussion from you experienced folks.

The 7.62x39 can be challenging to make feed reliably.

I saw a photo of a feed ramp from a maker that use with great reliability. The ramp was not the divided type M-4 ramp, but a solid ramp leading up to the chamber.

Was having trouble with mine, and knew the feed ramps were where the failures were happening. I got my tools out an ground down the middle hump on the feed ramps, and mine has been 100% since. If need be, I can post a photo for you, but really can't recommend doing what I did unless you know what you are doing.

My ramp looks like this:



This was what it was before:

Great Dremel work!

Right on. Appreciate your posting!

What mags have you found 7.62x39 success with?

I'm using DuraMag SS's.

polishing and opening the feed ramps can help with bigger rounds, Polishing alone can help if 223 has issues.

thats a good job on removing the hump. Need to look at nephews x39 Its never given an issue with ballistic tips or barnes. But I should look in there just to learn.

They don’t work with Speer 130 gr FPs (#2007). I can tell you that. My 300 BLK was finnicky with that bullet. I’ve recently switched to the Horn 125 HP and the Sierra 135 HP and they’ve been fine. The 125 HP is better than the Sierra 135, but I’ve only had 1 FTF with it in 50 or so rounds.

2% is way too much, but considering it was 50% and I’m currently working through some major concentricity issues with rounds after bullet seating, I’d say it’s not the projectiles fault.

My 7.62x39 AR runs like a freaking top with Sierra, Hornady and Nosler Varmageddon (I think Hornady SST OEMs if I’m not mistaken). All these are plastic thin or SP variety, so no broad meplat projectiles. Even with S&B ammo with not very pointy SPs, it runs perfectly.

I’m pretty sure those two pics aren’t a before and after (and I don’t think rockinbbar was saying that they were). I believe they are representative of two different ramp styles. The bottom pic the ramps extend into the upper. The top pic they don’t. You can’t add back metal with a dremel.

Petro, if you can find 125 Sierra SP's, try them. They have been flawless in my BLK.

Correct. Just showing what works from a particular manufacturer in the top picture.

More images of opened up feed ramps appreciated. I'm fairly adventurous. Nothing money can't cure - in moderation.

By the way, the 7.62x39 round that started this was the PRVI round nose supersonic with a good bit of exposed lead up front. The leading edge of the bullet jacket would "catch" as well as the case mouth. My ASC mags were tossed in favor of Duramags as well.

I'm working on another x39 today and might give it a whirl. About half jokingly told a friend that if he did a particular something I'd give him an AR and sure as heck. LOL


Thank you for the comments.

Nice work on that feed ramp!

My favorite mags are the 28-round Duramags.

I have a couple ASC mags in 10-round and 20-round. They have functioned well enough, but the Duramags have some different kind of mojo. When I load the Duramags, they just feel like they are loading up smoothly and easily.

Boomer, I just went and looked, it is the Privi RN that was giving me trouble, not S&B!

Son_of_the_Gael, yes those have worked well for me in the past. I switched over to the hornady 125 during the last panic and haven’t gone back over.

Thats interesting on the mags. I've never had a problem with ASC but have not had an X39 thats mine. They work well in the spc cases, Grendel etc...

Interestingly I had the same impression loading the 10-round ASC 7.62x39 mags, like I was fighting them.

Still hoping for a Pmag ARx39.



About Dremel time.

Right on. I am not alone it seems....

Yep, especially those 10-rounders.

I went ahead and did this. Just followed the lines of the two and connected. Hopefully try it out today.

Seems to work, even with the short PRVI round noses previously mentioned. Eats up Barnul and Wolf steel cased. Cerakoted then rattle canned LOL.

Appreciate the inputs!

Nice!

Nice work.