168gn SMK sub-sonic w/carbine gas system

[Flewis]

I'm looking for a little cheaper sub-sonic load for my AR15 based whisper. I currently have it running great with 220 SMKs and 11.6gn of AA1680. It is a 16" barrel with a carbine length gas system. The gas port is opened up to 0.125.

Wideners has some 168 grain match bullets that are very similar (looking) to a SMK.

http://www.wideners.com/itemdetail.cfm?item_id=8439

Does anyone have any experience shooting a 168gn sub-sonic in a rifle similar to mine? Just wondering if I can expect it to cycle and what powder seems to work best.

Thanks

[Colohunter]

I haven't tried the 168gr SMKs, but I did get a load that works for 150gr Hornady FMJs with AA1680. They are quite a bit cheaper than the 220grs. I am sure that if the 150s worked you could get your 165s to work.

[Flewis]

Do you remember your load data? Just curious for comparison.

[Colohunter]

I'm at work now, I'll try to get it out when I am back at home. The AA1680 worked with both 150grs and 220grs. The only thing I didn't get was bolt lock back after the last round on the 150gr load. I decided that was adequate for my use, I didn't want to have to mess with opening up the gas port or anything like that if I didn't have to.

[Colohunter]

I actually found the info from a previous post I did, this is the info that I got from AA1690 with both 220gr SMKs and 150gr Hornady FMJs:

11.7gr of AA #1680, 220gr Sierra HPBT, 1089fps-avg
All rounds ejected, cycled and the bolt locked back after the last round.

10.5gr of AA #1680, 150gr Hornady FMJ, 1095fps-avg
All rounds ejected and cycled, but the bolt did not lock back after last round.

[Flewis]

I actually found the info from a previous post I did, this is the info that I got from AA1690 with both 220gr SMKs and 150gr Hornady FMJs:

11.7gr of AA #1680, 220gr Sierra HPBT, 1089fps-avg
All rounds ejected, cycled and the bolt locked back after the last round.

10.5gr of AA #1680, 150gr Hornady FMJ, 1095fps-avg
All rounds ejected and cycled, but the bolt did not lock back after last round.

Thanks for the info! I think I'll give the 168 grain bullets a try.

They also have 175 grain match bullets for the same price. They look like SMKs except they have an exposed lead base. I would try them but I'm afraid I'll wind up with lead in my suppressor and gas system... I'm assuming some amount of that exposed lead would burn off going down the barrel.

[Medic650]

I looked at the 175gr bullets at Widners also and was wondering about the lead exposed at the base. I posted a question about the exposed lead at the base and leading a suppressor on SilencerTalk. Response I got there was that a small amount of lead would vaporize but would be burned out of a suppressor when it heated up. I may try some of those 175 gr bullets.

[JFettig]

Medic, most FMJ bullets have lead at the base and thats a lot of times primarily what people shoot. Especially in pistol calibers.

I don't know for sure but I'm gonna say that I doubt it. I'm pretty sure its from the lead bearing surfaces that get so hot and vaporize. FMJ bullets still have copper bearing surfaces.

Jon

[Flewis]

Well, I picked up some 168 grain Hornady bullets to test with. Running at about 1080 fps (10.6 grains AA1680).

Cycles just fine, but doesn't lock the bolt back on an empty mag... no big deal there.

However, I'm getting poor accuracy at 100 yards (2 to 2.5 inch groups) and its obvious that they are starting to tumble as I'm getting slight keyholing on the paper.

Colohunter, what twist barrel were you using with the 150's?

I can't really push them any faster or they'll go super-sonic. Is the 1:8 twist rate too fast for 168's? Any idea where my instability could be coming from?

http://rx7.voodoobox.net/images/168kh.JPG