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1 in 7 twist 3 groove 7mm barrel no issues

 
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Old 04-04-2009, 08:12 AM
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Location: Tucson Az
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1 in 7 twist 3 groove 7mm barrel no issues

Approximately 6 months ago I had some discussions with members regarding the barrrel I ordered from lilja. It is a 30" 1 in 7 twist 3 groove in 7 mm. I was told the 3 groove would destroy the 180 Berger VLDs. I was also told the twist was too fast and could also cause issues.

I had it chambered with a Pacific Tool and Gauge reamer in 7 Rem mag.

After breakin, the initial loads with the 180 VLDs into the lands and RL-25 produced some fair groups. It came together with 69 grs for a velocity of 3100 fps. It doesn't show any signs of bullet disruption/damage.

In addition to this barrel a friend recently put together a 7 STW with the exact same barrel configuration. He is getting approx 3225 with the 180 Berger VLD also with no signs of bullet damage.

I was assured by Bryan Litz and Dan Lilja this barrel would not cause any issues. I thank them for their encouragement.

FYI both barrels are cleaning up very easily with very little copper showing up, just some powder fouling.

This site is all about sharing experiences. I figure this should be out there for others to read.
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Old 04-04-2009, 10:46 AM
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Re: 1 in 7 twist 3 groove 7mm barrel no issues

AZ, while I'm sure I was one of the ones who though it may be a concern .....I'm glad I was wrong as I hate seeing people having to spend more money to make things right.

I also didn't have any problems until I had close to 200 rounds down the pipe. It was very accurate out to 1000 yards and even when I had bullet dusting the ones that made it to the target continued to be accurate. I shot the my very best group at 1000 with that barrel at 3 3/4", accuracy was never an issue.

I'm glad its working for.

When they are available again you need to try the 200 grain Wildcats....they are really something. You'll probably drop 100 fps but it wont matter as the BC is just that much more impressive.
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Old 04-04-2009, 05:22 PM
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Re: 1 in 7 twist 3 groove 7mm barrel no issues

Oh great...so now I have to sweat the 200 round mark!!! <grin>

I did consider the 189 Cauterucio bullets but for now I will stay with the 180 Berger VLDs.
I'll keep the 200 gr Wildcats in mind.
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Old 04-06-2009, 06:31 PM
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Re: 1 in 7 twist 3 groove 7mm barrel no issues

I had to rebarrel 16, 7mm Allen Magnum rifles on my dime for just this reason. They were the original batch of rifles designed to shoot the 200 gr ULD RBBT wildcat bullets.

Every one of them shot amazingly well until they hit from 200-300 rounds down the barrel. Then it was like a switch was flipped and the rifles went from 1/4 to 1/3 moa rifles to having 50 to 100% of the bullets coming apart in flight.

That said, these were being loaded to a velocity of 3200-3350 fps with the 200 gr ULD RBBT bullets. After this occured, nearly every rifle still shot very well the 160 gr Accubond bullets loaded from 3400-3550 fps.

Obviously this is higher velocity levels then you will be dealing with so that may help you dramatically.

Also, I have found that the 180 gr Berger will take slightly more abuse then the 200 gr ULD RBBT. The reason is because the 200 gr bullets were made on 30 cal J-4 jackets that were reduced in diameter to work with the 7mm bore size. This certainly work hardened the jacket and this may also be the reason for the bullet failures once the barrels got 200-300 rounds down the barrel.

I will say that in my testing, the Berger 180 gr VLDs shot very well in most of these barrels as long as they were shot at velocities under 3300 fps on average..

That said, with the VERY fast twist which is much more then needed for either of these bullets, once the barrels get some wear on them and the throat roughens up, you may start seeing some issues but I suspect at the velocity range you are at you will not see this nearly as soon as the 7mm AMs did.

The cure was pretty simple, go to a 1-9, 4 groove barrel or a thin land Rock 1-8.7 5R barrel which seem to solve all the problem.

I have a 7mm AM that has a Lilja 1-9, 6 groove and it was tearing 200 gr ULD RBBT apart and last weekend I tested the 180 gr Berger in it and they shot very well, at least for a barrel with the number of bullets this one has down it, roughly 800 rounds.

Again, I would suspect you will see problems MUCH farther down the road then we did and possibly you may never see a problem before the barrel is ready to be replaced.
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Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

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Old 04-06-2009, 07:29 PM
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Re: 1 in 7 twist 3 groove 7mm barrel no issues

Thank Kirby for sharing your experiences. I know 1 in 7 twist is more than needed. Lilja said he doesn't make a 3 groove in any other configuration for 7 mm. If it doesn't work later in its life I can always switch to other bullets. I built it for the fun of it have no idea what I'll do with it for sure. Could use it for longer shots on coues wt as we don't walk around, just lots of glassing. If nothing else it will serve as a learning tool for other rifles in the future.
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  #6  
Old 04-07-2009, 08:50 PM
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Re: 1 in 7 twist 3 groove 7mm barrel no issues

Hi if you are after Carturio 189gr 7mm projectiles i have over 400 of them in my 7mm BSM with a Lawton 9 twist cut barrel they will not shoot i can shoot Sierra 175's and 168's and they shoot like stink but the Carturios wont shoot. I also tried the 162 A Max the first made it to the 600 yard target the next two turned to dust 10 yards from the muzzle. The case is a modified 270WSM case with the shoulder pushed back to give it a 370thou long neck then it is improved with a 60 degree shoulder. I was using 68gr of retumbo with CCI250 primers and am using 68.5gr H1000 with the 175gr Sierra Molly coated in a 32" barrel have not chrono'd it yet but it should be well above 3000fps i am thinking closer to 310fps it is my long range F Class calibre.

If you are interested in the 189's let me know and i will count how many i have left and work out a price posted to you.

Cheers Bill
Australia
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