Velocity Question

[HuntPA]

Start super and back down slowly in 0.3 or 0.5 grain increments. Bullets don't go much slower than 800 fps depending on barrel length before they stop in your barrel. Eventually the bullet will stop in the barrel. CHECK between EVERY round that the barrel is clear. Eye opening to me how much force it takes to move a bullet through rifling.

I have had luck with A1680 for a sub load in a 22 inch barrel.

 

[dellet]

Start super and back down slowly in 0.3 or 0.5 grain increments. Bullets don't go much slower than 800 fps depending on barrel length before they stop in your barrel. Eventually the bullet will stop in the barrel. CHECK between EVERY round that the barrel is clear. Eye opening to me how much force it takes to move a bullet through rifling.

I have had luck with A1680 for a sub load in a 22 inch barrel.

This really is important, with the gain on popularity of subs. There really still isn’t t reliable load data for the many combinations of cartridges, bullets and barrel lengths out there.

I was given a handful of 250 grain ATip when they first came out to try as subs in 300 Blackout. An interesting combination, with an interesting set of problems. Because of the length and weight of the bullet the window of suitable velocity and over pressure was pretty small. I was confident in the load I chose as being safe, and probably higher than needed in a 16” barrel, but chose to try it first in a 8” barrel. Less chance of a stick bullet.

First round measured 250 fps according to Lab Radar. Checked all the settings, second round 300 fps. Set up a second chronograph that confirmed the low velocity. Bumped the charge weight, no real change in velocity.

I was using data that had got 1400 fps safely for a 265 grain cast bullet. Pretty sure it was the bullet. After careful measuring I was stumped. Started reading reviews looking for excessively low velocity problems.

What I eventually stumbled on was people talking about the nice little gift that Hornady included with the individually separated bullets, everyone needs a Hornady logo rag. Turns out the bullets weren’t cleaned after manufacturing and still had on oil coating. The rag was to wipe off the oil. Velocity problem solved. A good example of friction, pressure, velocity relationship. It’s just really magnified with subs

 

[Bowhunter41]

Charlie b

Thanks for the responses I was also thinking of raising the muzzle up to ensure most if not all powder was near the primer.

More experiments to come. I found on sniperhidw forum guys using faster burning powder. When one looks at the hodgdon manual the one page has burn rates of powder froM fastest to slowest while a lot of people say Trailboss that burns relatively slower than say titegroup or tite wad.

 

[charlie b]

Just to add a caution. HuntPA mentioned bullets stopping in the barrel. Squib loads are common when trying to get the slowest bullet possible. When testing make sure you see a bullet hole in the target or a dust cloud of bullet impact on each shot. If not, pull the bolt and look through the bore to make sure there is not a bullet still in there. A bore obstruction may not cause an explosive event, but, it will bulge the barrel. I've had to 'tap out' more than a few bullets during testing.

Do not count on recoil to tell you the round fired properly. There just isn't much.

If you want more information than you can stand go to the CastBoolits forum and look up 'mouse fart' loads.

 

[Bowhunter41]

Charlie b. Totally agree with your statement. Better to be safe then sorry

 

[Bowhunter41]

Thank you all for your input

 

[Bowhunter41]

Ok so I was able to get some rounds out today.
1. I used the Hodgdon manual for H4895 and 175 sub-x. Every round was not subsonic when shooting. I have attached the chrono results.

2. I shot 5 rounds with Titegroup at 8.5 grains with 175 sub-x and chrono wasn’t working right but definitely not quite like I was hoping.

3. I then tried 8 grains of Clays with the 175 Sub-x and every round was nice and quiet with a nice group. Chrono data is also attached and you can see I was at roughly 1100fps.

Titegroup shots are also attached. This is the target with the extra dots for covering holes.

Clays group is next. I had one I pulled. Not a bad group. Again only 50 yards and will try farther later next week. Also going to try with 190g sub-x with 8 grains of Clays. No longer going to try the Titegroup or H4895