Mike1476

The BR-4 primers have the same cup thickness as the 450's and 41's (0.025"). They will work just fine for the 300 blackout, just be sure to start at the lower end of the powder range and work your way up...or down if you're loading subsonic. If you work up a load with the BR-4, and then switch to 450's or 41's, be sure to back off your load and work back up. Mike

Most of these aren't absolute necessities, but can come in pretty handy: Loading blocks, bullet puller, check weights for the scale. I assume you're priming on the press, but if not, a hand primer of some ilk. My bullet and headspace comparators get a lot of use, but those aren't "have-to-haves". I could make a much longer list of things I've bought that now just collect dust. Also, plenty of ammo boxes. I like to keep my casings separated by number of firings, and these keep them clean and organized. I keep everything well labeled as well.

Welcome from New Mexico

We have success! Had to go up to 0.0785, but now it runs as it should. Thanks again for all of the help!

So not this one then?

Drill bits were finally delivered. Drilled to 0.0700, and it wouldn't lock back on an empty mag, but it would pick up the next round. Went to 0.730, and first round locked back on the empty mag, but the next three wouldn't. Brass is landing at around 4 o'clock about 8 feet away. Any issues going up to 0.760? Still haven't heard anything from JP. Thanks!

Welcome from New Mexico.

Welcome from New Mexico.

Welcome from New Mexico.

Welcome from New Mexico.

Welcome from New Mexico.

Welcome from New Mexico.

Thank you very much! I’ll work up from 0.070 and post the results. I’ll also be sure to post any reply I get from JP. Thanks again!

The gas tube is 17.25" overall, and 16.56" from the receiver end of the tube to the center of the hole at the gas block. Gas block journal is .936". I actually did start with the gas block wide open, and only backed it down initially to see if it was overgas causing the issues. I do appreciate the replies, and very much appreciate the help!

Thanks to all for the welcome!

Is there a formula used to calculate the correct size of the gas port that can be shared...or perhaps just let me know if I'm on the right path. I've got a 260 that has not cycled properly since I assembled it. At best, it ejects the fired casing, but will not pick up a round from the magazine, and does not lock back on an empty magazine. Here's the specs on what I have: JP Supermatch .260 22" with XL gas length (end of gas tube is centered in the cam pin cutout); .936" journal at the gas block; 7" from gas port to muzzle; gas port diameter 0.0655.; SLR Sentry adjustable gas block. Fulton Armory upper and lower; buffer tube has 7" internal depth; buffer is 2.5" and 5.4oz; have tried Armalite EA1095 spring as well as Tubb flat wire. BCG is JP full mass weighing 18.9oz and has been well lubed during use; bolt is from JP and headspaced to this barrel. I've tried factory ammo of several weights from several manufacturers (Black Hills, Hornady, Federal) all with the same results. Am I correct in thinking that the gas port diameter is undersized? I have emailed JP Enterprises to see if this is within their specs, but I have yet to hear back from them (only been a few days). Any input is greatly appreciated! Thanks, Mike

Welcome from New Mexico.

I did a search for "260AR cycling issues" and this was the first site that came up, so I put the site search function to work. Found copious amounts of information relevant to the problems I was having with my rifle, along with other topics I didn't even know I needed to know.

Hi All, My attempts to diagnose a poorly functioning .260 led me to this forum, and it truly is a goldmine of great information! Long story short on the rifle, I believe it to be an undersized gas port (0.0655"). I've been reloading and tinkering with firearms since the early 80's, and am not ashamed to say that I've gone shooting for no other reason than I was out of brass to reload. I also own two Dremel tools and a tube of JB weld, so I'm pretty much a master gunsmith 🙂 Jokes aside, I mostly just wanted to say thanks to the members here, and hopefully I'll be able to contribute something positive somewhere down the road. Mike