Any issues with bore riders and autoloaders?

[thehouseproduct]

Hi all, I am getting my first chunk of Cerrosafe shortly to make a casting of my 300 Whisper chambers. I am looking to get a custom mold made for my AR15 Whisper to maximize weight of the boolit to better fit the magazine and cycle the gun easier. Are there any issues with bore riders being used in auto loaders that I should be aware of? I use a Lee C309-200-R now with fairly good results.

[GaryM]

I have used the same bullet in my AR type whisper without any issues.
I would not advise using it with a suppressor though, it can leave deposits that are a real bitch to clean out. Of course if your suppressor can be disassembled for cleaning then you might want to try it.

[Bret4207]

I'm not sure what fit in the mag has to do with bore riding, but then, I don't shoot those kind of rifle$$$. As far as the bore riding goes in the barrel, you want something that will fit in the throat most importantly and will be a slight interference fit as it rides the lands. Keeping in mind I dislike bore riders, even though I use them, I would make a chamber and throat casting with cerrosafe, a throat and a barrel slug. I'd figure the shrinkage on the cerrosafe and compare it to the slugs. Then I'd aim for something in the area of a half to a thou over bore size on my nose and of course a good +.002 on the body over groove size ( the easy sizing part). I'd take and send those measurements with a drawing of what you think you want along with a sample of the alloy you want to use to the mould maker so he can figure shrinkage and alloy effect. Explain in detail what you want to achieve and consider any advice he may give.

It might be a good idea to do your measuring and post some pics and drawings here to let the guys who are better with numbers help guide you.

[pipehand]

Yup, there sure can be issues with bore riders in semiautos. Most military gas guns have a floating firing pin, and the possibility of a slam fire is real. While it can be advantageous to have the nose of the boolit lightly engrave on a bore rider in a bolt gun, the same situation in an AR might bring on an out of battery firing experience. A lot of what is brought up in the Cast Loads For 7.62x51 thread in the Military rifle section applies to the AR as well.
I've never messed with the Whisper, and all my AR's are in 5.56mm, but the chamber should be set up to shoot 240 grain MatchKings- a very expensive projectile- with that bullet taking up a lot of the powder room below the neck of the cartridge. A heavy boolit should do the same, and while I try to keep the gas check in the neck of the cartridge, seating them below the neck hasn't ever shown any adverse effects for me.
Good luck with your project, and please do keep us informed.