7.5" barrel with suppressor. 178 grain Hornady A-Max.

Friend of mine wants to work up a load for his rifle. I suggested IMR4227 powder with 8.5, 9.0, & 9.5 grains. He has an adjustable gas chamber and different springs if he gets into cycling problems. I could find no data books for subsonic with such a light bullet. All subsonic I found started at 208 grains.

Anyone have experience with this?

I got 3O bullets loaded up for subsonic. 15 with IMR4227 and 15 with Accurate 1680. Hornady 178 grain A-Max. Now for some range time.

I run 175's at 1050 with 9 gr of H 110.....they run fine in my 16".
There is subsonic data for the lighter weight bullets on " load data" which you have to subscribe to. You are on the right track with your reccomrndations for 4227, I run 10 gr for 1040 fps with 175-180 bullets.

Well, I can't recommend 4227 since I haven't shot it yet! I'll post info once we've been to the range.

You're using 10 grains of 4227 with a 16" barrel? Maybe I should load up 5 more rounds at 11 grains for his 7.5" barrel. This is still quite a bit below maximum. Talking subsonic here.

I have never gone beyond the 10 gr load, I wanted to keep it subsonic, but to get as much velocity that I could while still keeping it sub. Pretty much my " go to " load with that bullet weight and running suppressed.

Yeah , I know. We will be able to tell if 11 pushes it sonic.

7.5" is not a rifle...........

it is a long M17 Glock.

That was my thoughts too.

IMO a powder a bit faster such as Accurate #9 would be something to look at. It will permit a load a bit closer to "maximum" which should help reduce variations in velocity due to position issues.

Might even take a look at Accurate #7. I use #7 for my hard cast loads because it keeps the velocity of of my 20 inch rifles low enough to eliminate the need to do any cleaning of leading in the barrel. It's also great for a real powder puff Magnum that is real easy on the shoulder in a Cowboy Match.

For subs I start high a couple grains (but below published max load) and work down. The reason is to avoid a squib load and the problems that come with it.