I wanted to mount my bench rest 284 Win barreled action in a chassis so I could mag feed it and shoot it from a bipod or tripod when shooting steel silhouettes at longer ranges. Before buying a chassis, I had questions about what I would need to mag feed the rifle. The Magpul Pro 700L chassis comes with two pMags. One is a 5-rounder for 30-06 family cartridges (stock # MAG671). The other is a 5-rounder for LA Magnums such as 7mm Mag (stock # MAG698). To be clear, Magpul doesn’t recommend either one of these magazines for use with 284 Win cartridges. Since I could not find any mags from any manufacturer that seemed to be purpose built and because I like pMags, I took to the online community. Several people said they were using one or the other of these pMags in 284 Win and some said they fed “flawlessly” with no modifications, while others had to “open the feed lips” on the Mag671 mags, or “modify” the feed lips on the MAG698 mags. This post gives details about my experience with these pMags with a Kelbly Atlas Rem 700 footprint action and the Magpul Pro 700L chassis.
Neither one of the mags fed flawlessly with no modifications in my chassis and action. First I tried the MAG671. I had changed scopes so I rezero’d the rifle using these mags. I noticed that after some shots the bolt wasn’t pushing the next round out of the mag, but it would if I bumped the mag upwards before closing the bolt. Later I took a closer look at this and found that during bolt closing, the bolt was hitting the top of the feed lips and pushing the mag down about 0.1 in or more. When only up to about 0.1 in or less downward movement occurred, the bolt would still feed the next round, but when the downward movement was more, the next round wouldn’t feed until bumping the mag bottom to push it back up. The 284 is larger diameter than 30-06, and I believe that by opening the feed lips, I could have made this mag work all the time. I also noticed that sometimes when the round was pushed out of the mag by the bolt, the 184 gr hybrid bullets were not hitting the sweet spot on the feed ramp and sometimes I had to short stroke it to get them up the ramp. I’m not sure how cleanly I could open up the feed lips, and with the feed ramp issue also, I decided to try the MAG698 magazine before I would do any modifications to the MAG671.
With the MAG698 mags, I quickly noticed that when I seated the mag on an open bolt, the bolt stopped when it hit the back of the feed lips. At first I though “case closed, I will use the MAG671 mags” but then I thought about a little more and decided to try inserting the mag on a closed bolt, then cycling the bolt. This time it fed flawlessly. So the secret was just to get the bolt to nudge the mag down just enough so the bolt could pass. I used a Dremel tool to make a small ramp on the back of the feed lips (see the picture) and this seemed to do the trick. These MAG698 mags fit a bit tighter in my mag well than the MAG671, and so far during shop testing I haven’t seen these mags get pushed too low to feed the next round, but I will have to do some field testing to be more sure. Very likely I will be using the MAG698. The issue with the MAG698 doesn’t seem to have anything to do with the 284 Win cartridge. The issue I saw with the bolt stopping would still occur with an empty magazine. This was an issue of having some subtle geometry differences in the interaction between the 700 LA clone and the bottom metal on the chassis vs the vertical fit with an actual Rem 700 action. I asked the guy that said he had modified the feed lips on the MAG698 a few times exactly how he modified them but he never answered that question - if he’s senior like me he probably just couldn’t remember, but I believe that he probably cut a ramp on the back of the feed lips.
I guess the lesson for me here is something that most of you already knew quite well, that there can be important differences between factory actions vs custom clones when it comes to feeding well from a magazine. I also have new respect for the guys trying to build mags that work well with a lot of different cartridges and highly similar but not identical actions.
Neither one of the mags fed flawlessly with no modifications in my chassis and action. First I tried the MAG671. I had changed scopes so I rezero’d the rifle using these mags. I noticed that after some shots the bolt wasn’t pushing the next round out of the mag, but it would if I bumped the mag upwards before closing the bolt. Later I took a closer look at this and found that during bolt closing, the bolt was hitting the top of the feed lips and pushing the mag down about 0.1 in or more. When only up to about 0.1 in or less downward movement occurred, the bolt would still feed the next round, but when the downward movement was more, the next round wouldn’t feed until bumping the mag bottom to push it back up. The 284 is larger diameter than 30-06, and I believe that by opening the feed lips, I could have made this mag work all the time. I also noticed that sometimes when the round was pushed out of the mag by the bolt, the 184 gr hybrid bullets were not hitting the sweet spot on the feed ramp and sometimes I had to short stroke it to get them up the ramp. I’m not sure how cleanly I could open up the feed lips, and with the feed ramp issue also, I decided to try the MAG698 magazine before I would do any modifications to the MAG671.
With the MAG698 mags, I quickly noticed that when I seated the mag on an open bolt, the bolt stopped when it hit the back of the feed lips. At first I though “case closed, I will use the MAG671 mags” but then I thought about a little more and decided to try inserting the mag on a closed bolt, then cycling the bolt. This time it fed flawlessly. So the secret was just to get the bolt to nudge the mag down just enough so the bolt could pass. I used a Dremel tool to make a small ramp on the back of the feed lips (see the picture) and this seemed to do the trick. These MAG698 mags fit a bit tighter in my mag well than the MAG671, and so far during shop testing I haven’t seen these mags get pushed too low to feed the next round, but I will have to do some field testing to be more sure. Very likely I will be using the MAG698. The issue with the MAG698 doesn’t seem to have anything to do with the 284 Win cartridge. The issue I saw with the bolt stopping would still occur with an empty magazine. This was an issue of having some subtle geometry differences in the interaction between the 700 LA clone and the bottom metal on the chassis vs the vertical fit with an actual Rem 700 action. I asked the guy that said he had modified the feed lips on the MAG698 a few times exactly how he modified them but he never answered that question - if he’s senior like me he probably just couldn’t remember, but I believe that he probably cut a ramp on the back of the feed lips.
I guess the lesson for me here is something that most of you already knew quite well, that there can be important differences between factory actions vs custom clones when it comes to feeding well from a magazine. I also have new respect for the guys trying to build mags that work well with a lot of different cartridges and highly similar but not identical actions.
