6.5 Grendel subsonic load

[AndyA]

Looking at loading my Howa Mini 6.5 Grendel with some subsonic loads for pest control. Looking to use the 147gr ELDM or similar. Will also be running suppressed. Ideas?

 

[Spook]

kwickload is saying 7.0 of H110 would give you 988 fps out of a 20 inch barrel.
...and 9 grains of H4198 would give you 1091fps.

 

[Oso]

300BO uses super heavy bullets because at subsonic velocity it needs the added mass to generate enough force to properly function the bolt in AR15.

In a bolt rifle you can use any weight bullet for subsonic. You can just as easily use a light bullet in the 6.5 Grendel (90gr-100gr).

What type/size of pests are you trying to put to sleep?

 

[AndyA]

Raccoon and woodchuck mostly.

 

[AndyA]

Giving 5gr of Promo a try. Should give 1100 fps in my 22" barrel.

 

[AndyA]

Well that didn't work. Had to use the cleaning rod to push these out of the barrel (not at the same time). Will up the charge to 6gr and 7gr.

 

[linebaugh]

Sounds like your FPS was a little low. (Just making a joke)

H110/296 was mentioned above. I have had very good luck with that subsonically. Case fill is not great but it ended up being the most stable and accurate in a 375 subsonic build. I was surprised by this and only mention as it may be worth a try. Very quiet also.
Conversely I have had very little luck with the "shotgun" type powders.

 

[Oso]

H110/W296 work in 300BO for both supersonic and subsonic. It performs best at higher case fill. For 300BO subsonic loads the 200gr-220gr bullets are seated deep into the case, which effectively decreases the case volume As a result a +9gr H110 charge is approaching full case fill on the available/reduced case capacity in subsonic loads.

With the Grendel the 147gr bullet will be mostly seated in neck and outside of case so there will be a lot of empty space inside the case body. A faster burning powder will do better handling the excess space while still having consistent ignition without being affected by inconsistent powder distribution. You might consider using Titegroup or Bullseye, or even something like Accurate #9.

 

[SKWERLZ]

H110/W296 work in 300BO for both supersonic and subsonic. It performs best at higher case fill. For 300BO subsonic loads the 200gr-220gr bullets are seated deep into the case, which effectively decreases the case volume As a result a +9gr H110 charge is approaching full case fill on the available/reduced case capacity in subsonic loads.

With the Grendel the 147gr bullet will be mostly seated in neck and outside of case so there will be a lot of empty space inside the case body. A faster burning powder will do better handling the excess space while still having consistent ignition without being affected by inconsistent powder distribution. You might consider using Titegroup or Bullseye, or even something like Accurate #9.

This seems like reasonable advice.

 

[Evlshnngns]

Well that didn't work. Had to use the cleaning rod to push these out of the barrel (not at the same time). Will up the charge to 6gr and 7gr.

How far down the barrel did it go?

 

[AndyA]

How far down the barrel did it go?

about 16-18". Barrel is 22". Always best to check before firing again when doing this stuff.

 

[Oso]

A piece of advise given to me by an old school reloader was that when developing a subsonic load without credit source of reloading data:

It is far worse to get a bullet stuck in the barrel then it is for the bullet to break the sound barrier. Pushing a stuck bullet out of a barrel can be a PITA. Easier to make certain that the bullet clears the barrel (higher charge weight), and then gradually reduce the powder volume until it drops down to your desired velocity.

In 300BO the charge weight to optimize a for subsonic in 8” barrel is different than charge weight for 18” barrel. The additional barrel length results in increased friction/drag on bullet which slows it down. Most subsonic recommendations assume 8”-16” barrel length. This could be an issue for longer barrels, and may require a slightly higher powder charge to ensure it safely clears your firearm. Always bring a cleaning rod

 

[AndyA]

Loaded up some more 147 ELDM with H110. Used 8,9,10, and 11gr to tryout. Hope I remember a cleaning rod.

 

[PGW Steve]

I played around with some old 155 gr Sierra Match Kings in a Grendel with Trailboss. It was a 25.5" long barreled 527 MTR, and thankfully no stuck bullets. That was a few years ago, and what I recall was I could estimate the velocity by the impact point at 100 yards. I wish there was an easy way to get low ES with subsonic rounds. It was just a fun experiment, not practical in Canada where we can't own suppressors.

 

[SKWERLZ]

A piece of advise given to me by an old school reloader was that when developing a subsonic load without credit source of reloading data:

It is far worse to get a bullet stuck in the barrel then it is for the bullet to break the sound barrier. Pushing a stuck bullet out of a barrel can be a PITA. Easier to make certain that the bullet clears the barrel (higher charge weight), and then gradually reduce the powder volume until it drops down to your desired velocity.

In 300BO the charge weight to optimize a for subsonic in 8” barrel is different than charge weight for 18” barrel. The additional barrel length results in increased friction/drag on bullet which slows it down. Most subsonic recommendations assume 8”-16” barrel length. This could be an issue for longer barrels, and may require a slightly higher powder charge to ensure it safely clears your firearm. Always bring a cleaning rod

That’s the route I took with my 338 arc.
Start high and work down.

 

[AndyA]

Went to the range today to shoot the H110 loads. Started with the 11.0 gr and worked my way to the 8 gr. 11,10, and 9 all shot complete with the 10gr load the most "accurate". 8gr stuck in the barrel. Going to work on the 10gr load.

Try this at your own risk.