What gives? (keyholes)

[shiner]

I loaded up some 180gr. Nosler ballistic tips with 12gr. of Trail boss. I wanted to start high and work down to subsonic. I Shot two shots at 100yrds- here is what that looked like:

I then shot three over the chronograph- they were 1268, 1216, and 1218. I have a 20" barrel, but I don't know what the twist is. What might the problem be and where do I go from here?

Thanks for the help,
~Shiner

 

[KHOOKS]

Re: What gives? (keyholes)

Man we need somemore info on the rifle. What caliber and the twist. Take a cleaning rod and put pitch on a jag. Mark the top of the cleaning rod and start with mark up. Push the rod in until the mark turns a full turn and is back to up position then mark the cleaning rod at muzzle. Pull rod out and take measurment from the end of jag to the mark. Thats the twist ie if it went in 10" that a 1 in 10 twist.

My first guess is to heavy of a bullet for twist rate. But who knows without more info.

 

[shiner]

Re: What gives? (keyholes)

Sorry, I should have mentioned- It is one of the FN .308 barreled actions that I purchased from the CDNN buy. I need to check the twist, I tried once without much luck, but I'll try again. Perhaps someone out there knows what twist they are?

Edited to add- Looks like it's 1:12 twist.

 

[Seventy 1]

Re: What gives? (keyholes)

I'm guessing its a 1:12 and mv is too slow. Rounds are not stabilizing.

 

[shiner]

Re: What gives? (keyholes)

Do I need a faster twist just to shoot the 180's sub-sonic, or to shoot ANYTHING subsonic?

 

[MontanaMarine]

Re: What gives? (keyholes)

180gr roundnose usually stabilizes in a 1/12 twist at subsonic velocity.

I tried 220 roundnose, and they were wobbly at 1050 fps, 1/12 twist.

 

[ChadTRG42]

Re: What gives? (keyholes)

Most of the time you see SP, FP, or RN flat base bullets for sub sonic. The Nosler Ballistic Tip is a BT bullet, pointed, and is pretty long. Length is what requires more stability. So, you might need to switch to a SP, FP, or RN bullet for it to work. But, it looks like they are consistant, and a bullet going sideways will still mess something up!

 

[jasonk]

Re: What gives? (keyholes)

+1 Go to a RN bullet, long pointy bullets are not made to be subsonic. The RN bullet will be cheaper than the other option which is going to be replacing the barrel with a 1-10" twist.

J

 

[shiner]

Re: What gives? (keyholes)

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> a bullet going sideways will still mess something up!</div></div>
I have been thinking the same thing. But I'm afraid that they might mess up my suppressor in the process. LOL.
I haven't been loading to the lands- I have been loading to fit in the magazine.
Apparently I need to get away from the ballistic tips- These are 165's that I shot today- you can tell they're BT's!-

I have some 110 Sierra Varmint bullets- they have a flat base- do you think it would be going too far in the other direction?

BTW, thanks for all of the help,
~Shiner

 

[ChadTRG42]

Re: What gives? (keyholes)

Correct. Stay away from the 110's. They are too light for subsonic stuff. The one's that have worked for me are the 170 grain 30-30 FP and the Hornady 180 grain SP flat base.

 

[shiner]

Re: What gives? (keyholes)

I've heard it said that "it's all in the wrist"- Well thanks to you guys and your help and advice I learned that it's really all in the proper projectile selection. I loaded up some Hornady 180gr. SP's with 11, 11.5 and 12 grains of Trail Boss and went back to the range. The shorter, flat based bullets stayed stable at 100 yards and only the first round (the 12 gr load) broke the sonic barrier; all subsequent shots were subsonic! Success! Here are three stable shots of the 11 gr. load:

Thanks for all the help with this confusing little experiment,
~Shiner

 

[Guest]

Re: What gives? (keyholes)

If your really looking to run heavy boat tail bullets slow, in a slow twist barrel, load them in the case backwards.

Go ahead Laugh if you want,....

 

[shiner]

Re: What gives? (keyholes)

I've read that elsewhere- it might be my next project.

 

[Rovieairto]

Re: What gives? (keyholes)

I was just about to mention shooting them backwards.
They will give you some stability margin for temperature changes and other variables.
The bullets BC will also improve (make sure it's a boat tail).
It is just as dangerous to load them forwards.

 

[ChadTRG42]

Re: What gives? (keyholes)

Awesome. Good to hear!