Home Forums Hunting & Shooting Ask The Gunwriters JB: Another Twist Question for the Guru!

OK, I just shot a bunch of 45 grain Hornday Soft points in my .204...they shot great!

Question is, after learning the hard way about TTSX at close to sea level, will these stabilize in my 1 in 12 twist Remington Barrel at close to sea level?

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Tom,

They're designed to stabilize in a 1-12 twist so no doubt will!

You could always measure the length of one and run it through the Miller program on the Berger site. Flat-based bullets will be more stable than the formula indicates, as explained in GACK.

Example of one, is they shot but not well. Same rifle keyholed 40gr Vmax. 1-12" twist.

Which would lead me to guess they are marginally stable, but they are a fair amount shorter.

Thanks JB...it is a flat base and I'll take your word for it!


Now.....gotta make a plan to send one Air Mail Express into a pig's brain!

Messing with a 1 in 9" .223, I found it interesting how just a little length could affect stability. 75gr Amax's shoot 5-6" groups, and 77 TMK's, which are just a little shorter, do about 1 MOA. Berger's 77gr OTM tactical is about .100 shorter than the Amax, and it does 1/2-3/4" at 100 yards - even though Berger's program says it is marginally stable.

I've seen the wheels fall off summer time loads shot in January too.

No kidding....I'm shooting now at about 50 degrees...which will be close to the temp. Id be shooting pigs in Texas next winter.. should be OK.....

It's been awhile, don't that 45gr look a lot like a Sierra 63gr SMP? Seems it was squat and not overly pointed

Sorry for the slow reply...but yes Scott...it is relatively " short and fat"

The 45 204 Horn is a goatphuq.....but like you a friend bought the Midway, Graf's or whatever special.


They will stabilize, but realize I have deemed them a goatfuque....

You lazy bastid, read JB's book "Gun Gack" and you won't have to ask him a question he already answered in his book!

Shut up! I'm still mad at you for selling my motorcycle!

Just got back after a couple days on the road.

Twist isn't the only influence on how well certain rifles shoot certain bullets. For a while I had two really fast .224 centerfires, a .223 WSSM with a 1-9 twist Lilja, and a .22/6mm Remington (also known as the .224 Texas Trophy Hunter) with a 1-8 Brux. The case capacities of both cartridges are just about identical, so they're capable of the same velocities--but the .223 WSSM shot 75-grain V-Maxes very accurately, and the .22/6mm didn't. Which is one reason I still have the .223 WSSM but not the .224 TTH.

I checked out your recommendation of the twist rate calculator on the Berger site...pretty handy!


Thanks!

Have had accurate results with it many times!

Aside from the difference between boattails and flat-bases, the biggie you have to consider is plastic tips. Their weight is considerably lighter than lead tips, or even hollow-points.

As an experiment, I clipped off one plastic tip from a 180-grain .30 caliber bullet, then clipped off the same length of the hollow-point on a typical high-BC 185. The plastic tip weighed 2 grains and the tip of the hollow-point 7 grains.

That makes a difference in weight distribution, and as a result the formula works better for plastic-tips if you plug a slightly shorter bullet length into the formula. I've started subtracting 2/3 of the plastic tip's length when using the formula, which seems to match range results.

Good to know JB...thanks!

That's the kind of info that keeps me around here, thanks MD

Good evening folks,

I was recently introduced to the site located at the link below which gives you the opportunity to account for the plastic tip (measure and enter info) on those types of bullets. If you're not already aware, maybe this will be worthwhile.

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

Regards,

JR

Somewhere around, there's a spreadsheet (think maybe Michael Courtney created it?) that does the same calculations, but you can archive the results, look at multiple rows calculations simultaneously, etc. Handy tool if you're moderately Excel-friendly.