39 gr of little gun with 200 XPB too hot?

[jgilesg]

Hey all
I was at the range yesterday here in So Cal.
I had some 200 gr Barnes XPB loaded on top of 39 gr of little gun, I used a side crimp and a small taper crimp.
I am using Winchester WSR primers. I know they are not optimum but I have 1000 of them.
Shooting it though a 18" 1:24 Tronix barrel.

I finally got a Caldwell chronograph to test velocity.
I set the chronograph at 8 ft in front of the muzzle.
Heres the odd part. My FPS out of that load was
2618
2639
2643
2526
2531
That seems way out of control. I didn't shoot any more of them and when I got home I pulled a couple to make sure the load was correct. I tested it on 2 scales one being a beam and the load was correct.

i shot some other rounds. 36 gr lil gun 225 FTX with a taper crimp. they were
2060
2151
2087
2158
2147
The last set seems closer to what it should be but the first seems way to high. Can the heat affect the velocity that much?

Thanks for any help offered
JG

[Hoot]

Seems like an odd result with the 200 XPB. It took something like 41gr to get mine out of a 20" 1:24 AR platform, to even get up to 2500fps. Then again, it was in the the 60's outside. I try to test loads in any caliber, at temperatures close to what I'll be experiencing when actually hunting. However, I'm no fan of range days when its in the 20's outside, which would be more typical of deer season up here. I'm a creature of comfort, so 50 is about as low as I'll go. Ball powders like Lil Gun, will change their performance as a function of temperature, much more than extruded (stick) powders.

Hoot

[jgilesg]

Do you think it could possibly make that much of a difference Hoot?
In the AR reloading handbook it has the 200 XPB at 2328 with 39.0 gr of lil gun and 2429 at 43.5.
Aren't I getting in a dangerous spot at 2,600 FPS in an AR?
JG

[Hoot]

Do you think it could possibly make that much of a difference Hoot?
In the AR reloading handbook it has the 200 XPB at 2328 with 39.0 gr of lil gun and 2429 at 43.5.
Aren't I getting in a dangerous spot at 2,600 FPS in an AR?
JG

IMHO, in an AR platform, you're skating on thin ice. You didn't say what your temp was but it ifs what you will be hunting at, roll that load back a couple of grains. IIRC, the water shots I did were based upon an initial muzzle velocity of 2500 fps. That is the round I carry when deer hunting. Probably more like 2400 when its in the 20s and 30's. Back in my tougher days, I've sat in a stand when it was minus 7. That's where you shoot the first deer to come along, just so you can didi mau back to the truck and warm up.

Hoot

[jgilesg]

Ya I thought that was getting a bit to high. The temp on my Caldwell app said 97 degrees. My gauge in my car said 117, it was a terrible day, i even got rained on when there. I thought people came to CA cuz of the beautiful weather.
I do pig hunt in central CA and i have done that in the low 100's, my biggest concern on that is over pressure on the case and get it stuck and need a follow up shot.
I did have one get hung up.
Thanks
JG

[jgilesg]

By the way.
I read awhile back the importance of having a chronograph if you re-load. I am so glad I took that to heart and ordered one, this is an example of that importance.
If I loaded up to the 43.5 the book says is safe.
That could have been devastating.
JG

[Bmt85]

It seems to me the Tromix barrels are faster barrels, meaning higher velocity for same load. I remember seeing one guy getting close to 2400fps on a 275gr TSX in a Tromix barrel and only running something like 36-38gr of Lilgun. A couple others I've come across seem to be a bit higher than normal, or at least compared to Bushmasters. Actually IIRC, Tromix barrels seem to beat 20" Bushmaster barrels with factory ammo.

I pulled out the Lyman AR book because it has load data for both those bullets. All data was from a Bushmaster 16" upper.
200gr XPB and 39gr of Lilgun gets 2328fps. Using a faster barrel, that's 2" longer, a side crimp, and high heat, then maybe you could reach that speed.
Question is did you see any pressure signs, also what was your case head growth.

225FTX and 38gr of Lilgun gets 2154fps. Your almost there with 2gr less of powder. Not a huge difference though. Try working up to 38gr and see what the velocity is, just to cross reference.

[Hoot]

Ambient temperature aside, brass is a fairly good conductor of heat. If the chamber's hot, it doesn't take much time before the powder (and primer) in a chambered round is hot as well. IIRC, I read that Lil Gun in large caliber revolvers, reaches some avalanche point when it gets hot and behaves outside a predictable curve in terms of burn performance. Can't say I've ever hit that, but I have hit spikes when switching from one batch to the next.

Tried double side crimping both drive band grooves once and discovered that there is such a thing as too much retention. Had to pull down something like 40 rounds. You learn and hopefully, you survive to apply that knowledge.

Hoot

[jgilesg]

Thanks Bmt85
I'm glad to hear the Tronix' are a bit faster. I just swapped it out for my Bartz 16".
Sadly I forgot my catcher yesterday (one of those days) so I couldn't tell you what the growth was, I didn't collect it as I went. I did have one though, the last one, fail to eject and I had to use a cleaning rod to tap it out on the bench. I tossed that one in the trash when I was there so I'm sure the growth was excessive.

I actually built a second 450 with the 16" Bartz barrel I pulled off with an extra lower and upper I had laying around. I finished opening up the ejector door today so I think I'll take it to compare next time out.
I'm going to load some up at 36 and see how they perform next Thursday, its senior day at the range and I get in for 10 bucks. Hopefully, it won't be 100 plus degrees.
JG

[jgilesg]

Hoot
That reminds we of what I told my wife every time we gave a set of keys to our children when they first started driving. "They ALL are going to make bad decisions and make stupid mistakes, I just hope they survive them and learn from them."
Thank the Lord, they all did and they all survived it.
Appreciate all you guys
JG