SUB-SONIC Grendel loads

[Rapier]

Well I drug the junk out to the range again Saturday, it was 91 degrees so a real cold snap. Luckily I decided to load the whole gambit again. I found that 2400 and #9 will not function the action reliably. It will shuck out an empty but not strip a round, sometimes, other times it opens the bolt and slams the empty back in the chamber, making it then hard to extract / eject by hand. Do not know what it is doing to the brass but it is a pain and it is not like the bolt just jarring open a touch and closing. I would use Unique if function was not required as extraction/ejection is no problem.

With a 3 oz buffer and rifle spring AA 2015 and H-335 functioned the action of my 16 inch with 160s, every time, but H-335 so far has a very high SD of 63-65 fps. AA 2015 however at 12gr ran the 160s at 1024 fps with a SD of 20fps and grouped at .625 @ 50 yards, all round holes with the 1-9. If I can get about 12.3gr to hold together at a low SD and run up to about 1060 to 1070 fps I would like that a lot.

Oh, I am running Win 7.62x39 brass, sized and fire formed with the CCI LR primers.
Ed

[txgunner00]

Good info Ed. I haven't had time to do any loading lately but that may change soon.

I'm using the same brass as you but with magnum large rifle primers. I wonder if that would help lower the SD of H335 loads.

[Rapier]

TX, I was wandering about the same thing yesterday myself.

I decided to clean the beast with a good wash last night, because of the sticky chamber business, and found what I really did not want to find, black sand in the action. So it appears one or more powders is not igniting completely and is either blowing back in the gas tube or dumping out in the chamber. That would certainly explain why some of the SD numbers were very high and if the chamber was full of grit, why a fired cartridge jammed back into the chamber would stick.

I used #9 in shooting steel for years and it has a reputation of being hard to ignite. I used rifle primers in my handguns with #9 for that very reason. With all of the powders being either ball or small granules it might be worth a try to switch to a LRM primer in the Win brass and a SRM or SRBR primer in the Hornady brass to get as hot a flame as you can, plus to check the effect on all the powders. But I do need to check the 2015 and H-335 for sure.

Of course it could also be a situation like 4227. With 4227 until you get to its required load density, it will not burn right. But as we go along we shall see if we can work a good burn into the subsonic velocity ceiling.
Ed

[Costa]

Just curious to those who are trying this. What gas length are you using? I know with my 300 Black Out the builder said that if I wanted to go subsonic with an AR the carbine length gas length would cycle the bolt back, while the mid and rifle length would wouldn't. Would there be any truth to this.

[Rapier]

Costa,
The info you were given is possibly correct in that my 16 inch upper has a carbine length gas tube and the data on the Whisper posted by J D Jones years ago, shows his upper to have a 16.5 inch barrel. I would guess he also used a carbine gas tube to get his gas pressure working early. J D's powders were also all pistol powders, but pistols as used in the IHMSA, including the unlimited class, with 14 inch barrels. Just keep in mind that J D is not limited by what is available, he has a good shop so he could also have built his own uppers with a specific tuned gas setup just for the Whisper by bullet and by powder.

I am working with a plane Jane carbine gas tube and a low profile gas block without adjustment.
Ed

[Rapier]

Hey guys,
I just stopped by Graft & Sons site and they have Hornady Blem 160s on sale for 17.99 per 100 with shipping at 4.95 in the lower 48 regardless of weight. If the discoloration bothers, just run them in your case cleaner.
Ed

[txgunner00]

Hey guys,
I just stopped by Graft & Sons site and they have Hornady Blem 160s on sale for 17.99 per 100 with shipping at 4.95 in the lower 48 regardless of weight. If the discoloration bothers, just run them in your case cleaner.
Ed

CAREFULL!! Those bullets are .268 (6.5 carcano), not .264. They might be OK for low pressure subsonic loads but I don't know for sure.

Good deal though. Might be worth buying a bullet re-sizing die from Lee.

[fanofflyn]

What's that? Subsonic Loads? Sorry, I can't hear!

[Rapier]

TX,
Well darn it, that is what I have been using all along. Now I know why my bullets are seated so deep. After you said that, I measured the base and they measure a true .267 Now at the nose where I measured the land marks I got .264 and thought I was measuring on the side, but not so.

Bad part is I finished my reserch this weekend and with these .267 bullets I have sub half inch groups, 1106 fps with 6 fps Extreme Spread and 8 fps SD over 10 rounds with full function 4+1 from the magazine. Basicly a perfect Sub Sonic load at 12.3gr of AA-2015. The load also seals the neck for no powder fouling in the chamber. It functions with the 3oz buffer and should function with the 6 oz buffer.

But, I would advise others to use the .264 bullets, because otherwise you must have a chamber that will allow the bullet's .0015 overage per side plus brass neck thickness and still have enough room to allow expansion when fired. My chamber works, yours may not. So be safe.
Ed

[txgunner00]

Can't argue with those results. I have wondered if the increased friction from a slightly oversized bullet would help with burn efficiency/ consistency.

[Rapier]

Well I can go ahead and post the results for those who are interested, with a warning, especially because I tested the Hornady brass as a last stage with H-335 in an attempt to gain better consistancey and a 62 ES with Win brass became a 176 ES with the Hornady brass. I think it is noteworthy that the 7.62x39 brass produced better consistancy with the sub sonic loads than did the Hornady brass, even with SR Bench Rest primers which are said to be the equivelent of SR Mag primers.

I do think it is important for us to come away from this thread with a workable sub sonic load in the Grendel even if we have to shoot ground corn cobs under polished rocks to get there. This round has a lot of potential for multiple use and night shooting of wild hogs close to populations is a definate need, and growing all the time.
Ed

[txgunner00]

I picked fire formed Win brass from the beginning because reduced capacity / increased load density should theoretically improve consistency. It's good to see some data to back up that assumption.

[Rapier]

[txgunner00]

Wow! Great write- up!

[hm2 clark]

There is a (said to be ) functional sub sonic Grendel load posted on the Reloders Nest in the rifle section