7mm Berger 168gr. VLD keyholing

hhunter318 · July 30, 2012, 12:55 PM

This might not be the most intelligent question but here it goes.

I have a 30 1/2" Pac-Nor barrel with a 1:9" twist chambered to a 7mm WSM. I started out shooting 175gr Sierra Matchkings and was shooting consistent .3 MOA groups at 100 yds. I decided to use the gun to hunt whitetail so I decided to switch to 168gr Berger Hunting VLDs. I loaded some using H1000, RL 17, IMR 7828ssc, and couldn't get them to shoot worth a crap. I played with the seating depth, still nothing. I shot them at 300 yds one day and every shot keyholed.

My question is, why would a lighter bullet like that not stabilize but a heavier bullet stabilize perfectly. Shouldn't it be the other way around? I've never had a 175gr Matchking keyhole. I want to use this gun for hunting but don't really want to use a Matchking. The 180gr Bergers maybe?

Clark · July 30, 2012, 01:21 PM

I have (5) 7mmRemMag rifles and I can't measure the twist rate accurately.
I can measure the difference between 10" from 9" twist, but I can't measure the difference between 9.25" and 9.5" twist.

I have shot 180 gr VLDs, and I cannot predict at what range that bullet will go unstable.

I am now back to Nosler Ballistic Tip bullets, because of the better terminal ballistics.

Creeper · July 30, 2012, 01:46 PM

Berger's recommended twist is 1:10 for the 168 match hunting VLD. However, I find it hard to believe that shot from a 1:9 twist, even a 30.5 in. barrel, that the bullet would destabilize or over-stabilize.
They do have a thin jacket though, so I suppose anything is possible. Have you been able to recover any bullets?

Call Burger... ask for Eric Stecker. If anyone can figure out why you're having issues, Eric will figure it out.

Also... read this.

Cheers,
C

math teacher · July 30, 2012, 02:05 PM

I believe the twist rate in the 7mm Rem Mag is close to yours. I find that 160 grain Nosler Accubonds shoot well in every 7mm mag I have tried and my friends and I have killed numerous deer, elk, and moose with them. My limited experience with keyholing has been with underloads which fail to give enough velocity to stabilize the bullet. If you didn't download them, try another bullet. If you only used starting loads, try working up the load and see if that helps.

hhunter318 · July 30, 2012, 02:49 PM

I was running about 65.5 grains of H1000 or so if memory serves me correctly. Like I said, I wouldn't be as surprised if this would have been the other way around with the 168s stabilizing and the 175s keyholing, but this just baffled me. I have since switched powder, sticking mainly to Reloder 17 for the 7mm WSM, so I might load a few just to test. I ordered 100 Berger 180s so we'll see how they shoot. I have a friend that loaded some in his 7mm RUM and his exit wounds looked like a frag grenade had exploded.

89blazin · July 30, 2012, 04:48 PM

Although the weight does play a part in stabilizing bullets through various twist rate / length barrels, don't forget that bullet length plays a larger role.

Creeper · July 30, 2012, 04:52 PM

Quote:

Although the weight does play a part in stabilizing bullets through various twist rate / length barrels, don't forget that bullet length plays a larger role.

Yep... the good old Greenhill formula still has validity.

C

**Unclenick** · July 30, 2012, 05:24 PM

Yes, length matters most. Weight second. Velocity for a given twist rate is third in the hierarchy.

In your case you went to a bullet both longer and lighter. Both moves in the wrong direction. For a given length, heavier is more stable. This is the problem with charts that show certain bullet weights associated with certain twist rates: they are assuming same bullet construction and same bullet shape so that weight always goes up with length and not the other way around, as happens sometimes in real life.

That said, though, the Berger should still be plenty stable in a 9" twist and is on the three stability calculators I have. I get gyroscopic stability factors from 1.6 to 1.9 with them, so you should have plenty of spin. So something else is happening here.

One thought that occurs to me is to suggest you might have core stripping. Try loading down at starting load levels or even lower. Maybe like 58 grains of 7828, and see if the keyholing stops?

243winxb · July 30, 2012, 05:43 PM

The bullet is coming apart? Depends if you have old or new Berger?? http://benchrest.com/showthread.php?...-test&p=384475

hhunter318 · July 30, 2012, 08:45 PM

Thanks guys for all of the helpful info. That chart is pretty helpful. I might load down some of the 168s I have left, but don't plan to buy more. I've had too good experience with the heavier bullets to decrease bullet weight and sacrifice b.c. Thanks again for all of the info.

mrawesome22 · July 30, 2012, 10:17 PM

Maybe you don't have the twist you think you have?

An insane amount of runout

Bullet bases are all screwed up?

sudo apt-get update

**Unclenick** · July 31, 2012, 08:05 AM

That's a good thought. Get out the patches and cleaning rod and double-check the twist rate.

old roper · July 31, 2012, 08:47 AM

Here is copy of the Greenhill Forumla

http://kwk.us/twist.html

The Berger 7mm 168gr VLD bullets I have length various between 1.445" to 1.450".

You might want to read this

http://www.24hourcampfire.com/ubbthr..._Barrel_Groves

**Unclenick** · July 31, 2012, 09:45 AM

For a more modern estimator that takes velocity and some atmospheric conditions particulars into account, use this one.

old roper · July 31, 2012, 11:38 AM

You can get this from Brian Litz see at the bottom of article

http://02b0516.netsolhost.com/blog1/...cs/twist-rate/

hagar · July 31, 2012, 11:57 AM

Try the 162 Amax, and you might never look back.

hhunter318 · July 31, 2012, 04:05 PM

Barrel is a 1:9 twist. It's Pac-Nor's Select Match Grade barrel so the bore is a mirror finish. It's not run-out, I'm meticulous about my case prep. Trim to length, neck turn, uniform flash holes, etc. Measure concentricity after loading also. Just a freak thing I guess. I will let you guys know how the 180gr Bergers shoot.

July 30, 2012, 12:55 PM	#1
hhunter318 Senior Member Join Date: September 15, 2010 Posts: 163	7mm Berger 168gr. VLD keyholing This might not be the most intelligent question but here it goes. I have a 30 1/2" Pac-Nor barrel with a 1:9" twist chambered to a 7mm WSM. I started out shooting 175gr Sierra Matchkings and was shooting consistent .3 MOA groups at 100 yds. I decided to use the gun to hunt whitetail so I decided to switch to 168gr Berger Hunting VLDs. I loaded some using H1000, RL 17, IMR 7828ssc, and couldn't get them to shoot worth a crap. I played with the seating depth, still nothing. I shot them at 300 yds one day and every shot keyholed. My question is, why would a lighter bullet like that not stabilize but a heavier bullet stabilize perfectly. Shouldn't it be the other way around? I've never had a 175gr Matchking keyhole. I want to use this gun for hunting but don't really want to use a Matchking. The 180gr Bergers maybe?

July 30, 2012, 01:21 PM	#2
Clark Senior Member Join Date: December 4, 1999 Location: WA, the ever blue state Posts: 4,678	I have (5) 7mmRemMag rifles and I can't measure the twist rate accurately. I can measure the difference between 10" from 9" twist, but I can't measure the difference between 9.25" and 9.5" twist. I have shot 180 gr VLDs, and I cannot predict at what range that bullet will go unstable. I am now back to Nosler Ballistic Tip bullets, because of the better terminal ballistics. __________________ The word 'forum" does not mean "not criticizing books." "Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist. Are we a nation of competing ideas, or a nation of forced conformity of thought?

July 30, 2012, 01:46 PM	#3
Creeper Senior Member Join Date: September 9, 2008 Location: Woooooshington Posts: 1,797	Berger's recommended twist is 1:10 for the 168 match hunting VLD. However, I find it hard to believe that shot from a 1:9 twist, even a 30.5 in. barrel, that the bullet would destabilize or over-stabilize. They do have a thin jacket though, so I suppose anything is possible. Have you been able to recover any bullets? Call Burger... ask for Eric Stecker. If anyone can figure out why you're having issues, Eric will figure it out. Also... read this. Cheers, C __________________ Shoulder Drive Nicholson Club

July 30, 2012, 02:49 PM	#5
hhunter318 Senior Member Join Date: September 15, 2010 Posts: 163	I was running about 65.5 grains of H1000 or so if memory serves me correctly. Like I said, I wouldn't be as surprised if this would have been the other way around with the 168s stabilizing and the 175s keyholing, but this just baffled me. I have since switched powder, sticking mainly to Reloder 17 for the 7mm WSM, so I might load a few just to test. I ordered 100 Berger 180s so we'll see how they shoot. I have a friend that loaded some in his 7mm RUM and his exit wounds looked like a frag grenade had exploded. Last edited by hhunter318; July 30, 2012 at 02:54 PM.

July 30, 2012, 04:48 PM	#6
89blazin Senior Member Join Date: March 13, 2009 Posts: 107	Stable bullet Although the weight does play a part in stabilizing bullets through various twist rate / length barrels, don't forget that bullet length plays a larger role.

July 30, 2012, 02:05 PM	#4
math teacher Senior Member Join Date: February 5, 2012 Location: Southwest WA Coast Posts: 558	I believe the twist rate in the 7mm Rem Mag is close to yours. I find that 160 grain Nosler Accubonds shoot well in every 7mm mag I have tried and my friends and I have killed numerous deer, elk, and moose with them. My limited experience with keyholing has been with underloads which fail to give enough velocity to stabilize the bullet. If you didn't download them, try another bullet. If you only used starting loads, try working up the load and see if that helps.

July 30, 2012, 05:24 PM	#8
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	Yes, length matters most. Weight second. Velocity for a given twist rate is third in the hierarchy. In your case you went to a bullet both longer and lighter. Both moves in the wrong direction. For a given length, heavier is more stable. This is the problem with charts that show certain bullet weights associated with certain twist rates: they are assuming same bullet construction and same bullet shape so that weight always goes up with length and not the other way around, as happens sometimes in real life. That said, though, the Berger should still be plenty stable in a 9" twist and is on the three stability calculators I have. I get gyroscopic stability factors from 1.6 to 1.9 with them, so you should have plenty of spin. So something else is happening here. One thought that occurs to me is to suggest you might have core stripping. Try loading down at starting load levels or even lower. Maybe like 58 grains of 7828, and see if the keyholing stops? __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

July 30, 2012, 05:43 PM	#9
243winxb Senior Member Join Date: July 26, 2011 Location: USA Posts: 1,730	Berger bullet failure test The bullet is coming apart? Depends if you have old or new Berger?? http://benchrest.com/showthread.php?...-test&p=384475

July 30, 2012, 08:45 PM	#10
hhunter318 Senior Member Join Date: September 15, 2010 Posts: 163	Thanks guys for all of the helpful info. That chart is pretty helpful. I might load down some of the 168s I have left, but don't plan to buy more. I've had too good experience with the heavier bullets to decrease bullet weight and sacrifice b.c. Thanks again for all of the info.

July 30, 2012, 10:17 PM	#11
mrawesome22 Senior Member Join Date: November 9, 2005 Location: Ohio, Appalachia's foothills. Posts: 3,779	Maybe you don't have the twist you think you have? An insane amount of runout Bullet bases are all screwed up? sudo apt-get update

July 31, 2012, 08:05 AM	#12
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	That's a good thought. Get out the patches and cleaning rod and double-check the twist rate. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

July 31, 2012, 08:47 AM	#13
old roper Senior Member Join Date: June 11, 2007 Posts: 2,155	Here is copy of the Greenhill Forumla http://kwk.us/twist.html The Berger 7mm 168gr VLD bullets I have length various between 1.445" to 1.450". You might want to read this http://www.24hourcampfire.com/ubbthr..._Barrel_Groves __________________ Semper Fi Vietnam 1965 VFW Life member NRA Life Member

July 31, 2012, 09:45 AM	#14
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	For a more modern estimator that takes velocity and some atmospheric conditions particulars into account, use this one. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

July 31, 2012, 11:38 AM	#15
old roper Senior Member Join Date: June 11, 2007 Posts: 2,155	You can get this from Brian Litz see at the bottom of article http://02b0516.netsolhost.com/blog1/...cs/twist-rate/ __________________ Semper Fi Vietnam 1965 VFW Life member NRA Life Member

July 31, 2012, 11:57 AM	#16
hagar Senior Member Join Date: February 20, 2000 Location: Colombia, SC Posts: 745	Try the 162 Amax, and you might never look back. __________________ I don't have time for busy people

July 31, 2012, 04:05 PM	#17
hhunter318 Senior Member Join Date: September 15, 2010 Posts: 163	Barrel is a 1:9 twist. It's Pac-Nor's Select Match Grade barrel so the bore is a mirror finish. It's not run-out, I'm meticulous about my case prep. Trim to length, neck turn, uniform flash holes, etc. Measure concentricity after loading also. Just a freak thing I guess. I will let you guys know how the 180gr Bergers shoot.