Firing 300 grain OTM Berger in 7 twist: Will it damage my barrel?

[harry_x1]

I recently got a new barrel for my 33xc in 7 twist. I already have 50 rounds of 300 grain OTMs loaded from previous 9 twist barrel.

Can I fire these 50 catridges through the new 7 twist barrel as part of break in? Or there is a chance that the bullet might explode inside the barrel or something like that which can potentially harm my new barrel?

I understand this is a naive/stupid question...but I am fairly new to this...thanks for your assistance !

 

[rkb21]

You should have no problem shooting them in that twist

 

[SKWERLZ]

It will certainly fire them without hurting the barrel, make sure to video the shot trace because when 300 grains goes poof mid flight it makes an impressive gray cloud.
I’ve had a few cup/core bullets go poof with a bit milder spin than yours but the Berger’s held up better than I expected

Your combination will be spinning them 315K+!

 

[Wildcats]

7 twist is pushing the boundaries of jacketed bullets in a 33XC in imo.. if you are just going for barrel break in,you could chance it with mild loads.

 

[coldboreshot]

I recently got a new barrel for my 33xc in 7 twist. I already have 50 rounds of 300 grain OTMs loaded from previous 9 twist barrel.

Can I fire these 50 catridges through the new 7 twist barrel as part of break in? Or there is a chance that the bullet might explode inside the barrel or something like that which can potentially harm my new barrel?

I understand this is a naive/stupid question...but I am fairly new to this...thanks for your assistance !

I agree with the other contributor's inputs but if you want to be reasured, go to Berger's website to the Stability Factor Calculator and plug in you parameters. You should end up with an SG of 3.30-3.50. G7 Bc .421
Perfectly fine.

 

[shoot4fun]

I agree with the other contributor's inputs but if you want to be reasured, go to Berger's website to the Stability Factor Calculator and plug in you parameters. You should end up with an SG of 3.30-3.50. G7 Bc .421
Perfectly fine.

This brings me to a longtime burning question.
I have used Berger's Twist Rate Stability Factor Calculator many times and, no matter how crazy a twist number I put in, it always comes out with a stability factor and it always tells me the bullet is stable in my twist barrel.
It NEVER says anything to the tune of being above the "breaking point" where the bullet/twist rate I chose has a great chance of "poof".
Most bullet failures (the ones I have witnessed) occur outside the barrel. Proof of failure is the smoke cloud a failure produces. I have seen occasion where appropriate bullets were fired thru an appropriate twist barrel and failed about 25 yards past the muzzle. The barrel was just about 100 rounds old and in testing had never given any indication of bullet failure. In fact, it shot the break-in and load testing ammo amazingly well. My thought was that during range testing the owner had cleaned the barrel frequently and, once field testing began, the barrel did not produce bullet failures until it was the most fouled it had been allowed to be. Was it a seemingly insignificant and unnoticed rough spot in the barrel or maybe, being a major barrel maker's tight bore, could it have been caused by the fouling constricting an already tight bore?
Or maybe just a different lot of bullets that had less than the best jackets?
PS
I know this has nothing really to do with the OP's thread but just curious.

 

[SKWERLZ]

lots of things affect bullet integrity.
Jacket and bullet construction.
Supposedly 5r rifling is easier on bullets vs a 4 grove.
Barrel condition.
Brakes or suppressor effects?
Bullet damage from excessive seating force or sharp edges on cartridge necks.

Then there’s spin, once it sees 250k rpm rifle bullets are really seeing some force but it’s the 300k rpm range that is considered excessive for cup/core bullets.

 

[FeMan]

The stability calculators aren't set up to calculate stresses on bullets. Stability is a function of (among other things) air density and the stresses on a spinning bullet are independent of air density. The stability of a bullet and the outputs from the calculator change as altitude changes. The stresses on a bullet jacket are independent of air density.

Larger diameter bullets also have greater centrifugal stresses on the jacket than the smaller diameter bullets for a given rpm. I assume they have thicker jackets to compensate but I don't know for sure. I have never had issues with 6mm bullets at 300k rpms but have had 6.5s and 7mm blow up between 260k and 280k. Ive never blown up any 30s or 33s but the 250k upper limit seems sensible to me and 315k seems like a sure failure in a conventional 33 cal bullet.

 

[Benchrest Braxton]

as long as you aren’t running a suppressor you are fine, bullets might blow up but it won’t happen inside your barrel. i’m not saying its impossible but I have never seen or heard of one single account of this ever happening.

 

[SKWERLZ]

as long as you aren’t running a suppressor you are fine, bullets might blow up but it won’t happen inside your barrel. i’m not saying its impossible but I have never seen or heard of one single account of this ever happening.

That’s good advice!