I am not sure if this post belongs here or in the "Magazine" forum; but since I do not know what the problem is I will start here.

During my second range session with my new 458 I have noticed a consistent problem - the bolt is frequently failing to completely chamber a round after picking it up from the magazine.  The round will start to chamber and then hang up, canted.  If I drop the mag an inch or so and pull the charging handle and release - the round chambers fine.  This does not happen every time; once the rifle warms up it happens less frequently and it seem more common at the top of the magazine.

For those  of you who may have advice, here are the particulars:
1. This is a RRA rifle with the heavier "green" buffer spring installed for 458, although I had the same problem with the standard spring.
2.  I have tried 2 different loads with 2 different bullets and 2 different mags with consistent results. (COL 2.10")
3.  I checked to make sure the mag is seated well; no visible marks on the brass indicating a problem in the chamber and the rifle is accurate.

I appreciate whatever help you have to offer.

Looks like another Hoosier is getting his 458 ready for deer season.

To try and help with your feeding issue, what kind of mags are you using? When i got my 458 upper (rock river) there was a card in there showing how to modify GI mags to make it feed more reliably. Someone posted that card on here once before. If you didn't get it let me know and i can scan it and send it to you.

It sounds like a mag issue.

I had problems with flat nosed bullets hanging up because they were not angled properly. This was even after notching the front of the magazine and inserting "Single Stack" followers. I used a pair of channel lock pliers and gently tweeked the forward lips of the magazines allowing the front of the cartridge to sit up a little higher.   Now I can switch back and forth from cast flat nosed to FTX without a problem.

As for buffer springs....I tried the "Carbine " buffer spring RRA sent with my upper and along with a noticeable change in recoil my brass started getting small nicks and scrapes so I went back to the spring that came with my adjustable stock.

Now if my new Bushnell will just hold together and not fall apart like my last two scopes......

Jack  

I had this same problam with PRI mags and Cammenga the bullet would slide along the magazine and it look like the case neck was catching on the end of the magazine then switched over to same cheap'ol AR mags and it worked perfect also the clear Tapco mags work perfect for me also which are the ones I like the most.

Indeed, this rifle was bought with the excuse of perforating Hoosier deer...

I own 2 magazines, the 30-round that came with the rifle and a 20-round AR-Stoner.

There was no card with my rifle on magazine modification - I would appreciate anyone who could post or link to it.  From reAding other posts and looking at some photos, it appears that cutting a slight bit away at the front of some mags does help.

Bottom is a standard mag

Top mag has the cut out - Dremel tool is your friend, 0.5" diameter sanding drum.  Be sure to remove sharp edge or burrs.  Also, what might help is making your mag lips less sharp:  Disassemble mag or push follower down with one hand.  Use sand paper to remove sharpness from the mag lips to reduce drag on cases.  Some mags have razor sharp edges from where they were stamped out of the sheet...

with the upper off and BCG removed will a loaded round fully chamber if you drop it into the chamber?
RRA has some history of tight chambers, also shine a flashlight into the Chamber and see how smooth the chamber is cut.
You (MAY) need to polish it.

Marty is there any benefit to using a Match sled (or what ever they call it)

Marty, thanks much!  Judging by the way the cartridges were hanging up this looks to be the ticket.  Jim