Lazzeroni Firebird/velocities & accuaracy

[elkaholic]

I can't speak for Kirby but it takes a LOT of velocity to make up for much twist. It is not of much consequence normally. I am not familiar with the new 195 but an 8.5 twist does sound like a lot for a 195 .308" bullet?....Rich

 

[LazzInc]

I am going to start on a new rifle for myself this week, using a .284 9 twist polygon barrel, chambered in the Lazzeroni caliber 7.21 Firebird ,,,,

should do pretty well with the long 168-180gr 284 PILLS that everyone is hollering about ,,,,,,, I will keep you posted ,,,,,,,

 

[rooster721]

I am going to start on a new rifle for myself this week, using a .284 9 twist polygon barrel, chambered in the Lazzeroni caliber 7.21 Firebird ,,,,

should do pretty well with the long 168-180gr 284 PILLS that everyone is hollering about ,,,,,,, I will keep you posted ,,,,,,,

John, we've been out twice-more since I last posted info on these Berger loads.. and basically, after averaging-out all the numbers since I started collecting data, my averages are bouncing about 50fps (this way & that) from 3130 - based on the humidity-differences each day I shoot. The 7828 is obviously affected by the humidex-swings. 3130fps is where I settled for my charts and has balanced-out nicely (and very accurately with-in those humidex swings) When shooting 650/700/800 & 900yard targets, 3130 gives me consistent "gongs"

Looking closer at my 100yard groups, an 86gr charge is consistently giving a guy a 5/8 of an inch group.. that charge was my most accurate on paper (off bi-pod) and most consistent through the chronograph (often only 2-5fps differences, with the odd one straying up to a 12fps difference)

...this all SHOULD give you a very-good starting point for your own tests w/the Bergers - is really a shame they can't take the heat of anything-much faster than 3200. Am anxious to try the "coming" 195's for hopeful-differences.

 

[Fiftydriver]

Rooster,

I can not say for sure that a 1-9.5 will stabilize the new bullet until I get some in the air. If I had to guess, I would say it would be marginal.

That said, the 1-9 twist works great with the old 200 gr ULD RBBT from Wildcat in chamberings as small as the 7mm Dakota and 7mm STW. I have tested these bullets with a muzzle velocity of 3000 fps out to 1500 yards in the 1-9 twists at my 3400 ft elevation in temps from 10 degrees up to 90 degrees and they shot extremely well.

When I refer to the Dakota and STW as "Small", please remember that I compare everything to my 7mm Allen Magnum which in comparision, makes both of these magnum chamberings seem pretty small in performance and capacity.

Looking at previous Berger bullet designs, I would not be surpised to see the 195 gr be slightly longer then the 200 gr ULD RBBT but again, until they are in out hands, hard to say. The 200 gr ULD RBBT designed for the 7mm AM had the meplats closed to a pin point for two reasons, increase BC but more importantly, ****** expansion slightly to help them perform more consistantly on big game. If I had to guess, the 195 gr Berger and old 200 gr Wildcat will likely shoot well out of the same twist rate.

In my testing with the wildcat bullets, baring surface compression was a very important aspect of getting fine accuracy and the highest velocity possible with fine accuracy. IF baring surface compression was above 21-22% there were severe bullet integrity issues. This is one reason I settled on Lilja 6 groove and 4 groove barrels and a specially designed thin land Rock barrel design with a 1-8.7 twist. All of these worked great long term with these bullets.

The new Berger bullet will likely solve some of the issues with velocity as the other Hybrid designs have allowed higher velocity levels then the standard VLD Berger bullets.

Back to twist rate. When we started working with the 200 gr Wildcat bullets, and I keep referring back to this bullet simply because its really the only bullet that we can use to compare to the possible performance of the new 195 gr Berger bullets, Using all the computer models to predict required twist rate, they all predicted we go with a twist rate of 1-7 to 1-7.5. As such, we wanted to make sure these bullets would stay on point so we went with the 1-7. We also went with a 3 groove rifling design hoping to get the most barrel life possible out of the 7mm ALLEN MAGNUM chambering.

After several months of work, it was proven that this was a very bad barrel choice for a Heavy, Long, J4 jacketed bullet. Twist rate was far to fast for anything over around 3250 fps and the baring surface compression was FAR to high and after 200 rounds down the barrel, every bullet fired would come apart no matter what velocity we were using.

I tested nearly every twist rate and rifling design including 3 gr, 4 gr, 5 gr and 6 gr and the Lilja 6 and 4 grooves along with the specially designed Rock 5 groove barrels worked the very best for accuracy, velocity and long term rifle performance. It was also found that 1-8.7 to 1-9 twist rate was ideal when you had muzzle velocities over 3000 fps.

I never tested anything smaller to see what lower velocity levels produced as far as accuracy as I personally feel if you have a chambering smaller then the STW, a 200 gr 7mm bullet is really to heavy and your better served with the 175 to 180 gr bullet weights to bring velocity back up to that +3200 fps range which I prefer for long range hunting.

Would agree that if a bullet is not stable at lower velocity, adding 200 fps likely will not get fine accuracy, especially at long range and every envornmental condition such as extreme elevation changes and temp changes.

In the end, it would come down to the specific chambering being used but this is mainly because of the muzzle velocity potential of the chambering more then anything as to which bullet weight I would recommend.

If I had to order a barrel now for these bullets I would not go faster then 1-8.5 and would not go slower then 1-9. There are just as many problems going to fast in twist rate with these bullets as well so you have to be careful there as well. These are very long and heavy bullets for caliber. That bring up special issues. One I call "Bullet Wringing". Basically, this is when the bullet engages the rifling but because the bullet has so much length and mass, the rear section of the bullet resists this rotational force. The front of the bullet starts to rotate while the rear resists this movement and the center section of the bullet is very stressed. Like WRINGING out a wet towel. This weakens the jacket/bore bond which can often cause accuracy issues at best and total bullet failure in flight.

The only way to prevent this is to use a jacket with enough integrity to support these stresses which generally means a thicker jacket. The Berger Hybrid bullets seem to be much better at controlling this problem and allowing higher velocity ranges with these heavy, long bullets.

Shorter, lighter bullets, even driven to higher velocity do not seem to have nearly the trouble with this issue because the shorter the bullet, just like the barrels, the more rigid they are.

Hope this helps some.

 

[Brado16]

I have a 7.21 Firebird that I am going to start playing with soon. It has a 27'' Lilja 1-10 twist on it. I was hoping to be able to shoot the 168 VLDs from this but after reading through this post, it sounds like I shouldn't waist my time, also dont know if the 1-10 would be fast enough to stabilize the 168 VLDs.

Was hoping to use a heavy- high BC bullet to use that as a long range hunting rig since it weighs much less than my 338 LM. Any suggestions as to bullet or load data of where to start?

Thanks in advance.

 

[LazzInc]

LAZZERONI model 2012 rifle barrel choices now also include a 9 twist barrel for the 7.21 (.284) Firebird caliber ,,,,,,

take a look at it all by using the new "Build-Your-Own-LAZZERONI-Rifle" application on the homepage at www.Lazzeroni.com ,,,,,,

should be interesting even if you are not yet in the market for a Lazzeroni model 2012 ,,,,,,