Have a subsonic short barrel load to share?

[CTinNV]

I finally got my Noveske 10.5" barrel with pistol length tube and tried out some loads using 8.8gr of AA#9 and 240gr SMKs. Velocity was where I wanted it to be (about 1000fps), but the operation was erratic. (i.e. short strokes, usually ejecting with no next round feed). The rifle is using a standard buffer and the lighter AR15 semi carrier.

My first instinct is to drill out the gas port and use an adjustable tube to dial it back, but I'm wondering if the load is just not right for the barrel length. Is there a different powder I should be using for this setup? Thanks!

[buffetdestroyer]

You may have to increase the velocity slightly to get reliable function.

I am starting to experiment with VVN110 because my load with Alliant 2400 has a very small gap between where it cycles the action and stays under the sonic barrier (8 to 8.5 grains on a 220 gr.). I finally got my new Chrony out yesterday and was surprised at how high the velocity was (between 1125-1175 fps). When it has been hotter (sonic barrier was higher), it has been more forgiving at staying subsonic with my 8.5 grain load of 2400. Yesterday I ended up with a few sonic cracks (over 1168 yesterday) as it was a few degrees cooler (about 15 degrees and thus the sound barrier was lower).

I would check out the Sierra manual for additional powders if you can't get the AA#9 working. AA#9 is the fastest of the different powders listed, so if you are having issues with AA#9, you may have better luck with a slightly slower powder. AA#9 at the fast end; 2400, the 110's, and 296 are in the middle; and AA1680 is on the slower end.

Your other option would be to use a lighter bullet (or one with less surface area) as you can usually push them with less powder and still cycle the action (I am guessing due to less resistance past the gas let-off. 175 grain matchkings work great in my action with 7.5 grains of 2400 and are around 850-900 FPS.
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[mak91]

Im running 8.6 grn of AA#9 under 240 smk and it runs fine in my 3 guns. One is a 7 inch with the gas port move back 1 1/2, the other two a 10 inch and a 16inch with a pistol gas port opened to about .110 I think. This load locks back the bolt and cycles fine with all 3 guns. This is also a pretty quiet load and the powder seems to meter very well. I like it the best so far for heavy bullets. Do you know what size port your running? You might need to open it up to run that powder as its kind of fast for a semi. I've had good results with 8.2 - 8.5 grn of LiLGun under 180 - 240 smk in these guns also. Its a little slower than the #9, meters well and burns clean. If you have any of that you should give it a try. For a cheap subsonic plinking load I've been using 9.6 grn of SR4759 under surplus 147fmj. This powder is bulky and doesn't meter that well but it does a good job of filling the case when used with small bullets. I've loaded subsonic loads with bullets down to 110 grn with that powder that will cycle all 3 guns.

[Scalce]

I have had good luck with 175 SMKs and around 9.5 grains of H110.

I have had 100 reliable cycling in my AR and it is accurate out to 300 yards.

[CTinNV]

I guess my first mistake was with the speed of sound (I thought it was lower), which caused me to come in a little short. I could go a bit faster and probably make my loads work, but as experienced by others, there might be little leeway between short stroking and going supersonic.

Looks like I'll be trying a slower powder and see how that goes. Thanks for the replies.

[Scalce]

Actually 1000 fps is where you want to be but sometimes you need to go lower as some bullets will make noise in the Transonic range.

I was chronoing all the rounds when working up the loads but now I am going stricly by the sound and accuracy of the loads instead.

Remember that weather factors in to your loads.

In SC it has been 90+ for weeks so I may need to adjust my loads when the temps drop.

[alorton]

I have the same barrel you do (10.5" Noveske) and I've had good luck with 8.5 grains of 2400 under a 240 SMK or 8.0 grains of 2400 under a 208 A-Max. Both cycle my rifle reliably (I've never had a short stroke with either load) and are quiet. I've chronographed both loads at between 1000 and 1040 fps. They are also accurate at 50 yards (1/2" or less). I haven't shot them out further yet though.

[Scoop]

220 SMK, 9.0 gr H110, 205M Primer, LC04 Brass, 2.190 C.O.L Gave me better than 1 moa accuracy and averaged 1010 fps out of a 10.5 Noveske that I had awhile back.