Effects of 3 and 4 Groove Barrels on thin Jacketed Bullets

[Tmmdcampbell]

I have a lilja 3 groove 6.5 PRC built on a tikka. I have 300 rounds down the tube shooting hornady,s match 147 and hunter143. The 147 are flying at 2894 and the 143 are clocking in at 2993. No problems yet. Very accurate barrel.

 

[J300UM]

I may be able to add to this discussion. Sunday I shot a small whitetail buck at 545 yards. I'm shooting a 264 win mag with a Kreiger 4 groove barrel with an 8 twist. Impact velocity was ~2475. The bullet broke a couple ribs on the way in, did a fair amount of internal damage, and lodged in the off side rib cage. In my mind the bullet should have passed through easily as this deer was really no bigger than a pronghorn. Last year I shot a pronghorn at 330 yards with the same load. The bullet entered in the crease behind the shoulder, took an odd turn, went through the gut, and lodged in the off side hind quarter. The buck was standing broadside when I shot him. I also shot my cow this year with the same load. 290 yards, broadside, impact in the crease. The near side lung was destroyed. The far lung was untouched. Granted, all of these animals died relatively fast but I've been scratching my head trying to figure out why my results have been so different from a friend of mine shooting the same bullet. It's starting to make more sense as he's using a 5r barrel. His results have been consistent and much more predictable.

 

[Broz]

J300UM I assume the bullet is of the thin jacked nature?

Jeff

 

[J300UM]

Yes sir. It's the 140 Berger Elite Hunter. To add to my experiences, years back, I had a splash from a 210 VLD on a spike bull at 120 yds. The muzzle velocity was 3050. I hit him square in the shoulder (bad shot on my part) and not a single bit of the bullet got through the scapula. The bullet was fired from a 3 groove Lilja.

 

[Broz]

Yes sir. It's the 140 Berger Elite Hunter. To add to my experiences, years back, I had a splash from a 210 VLD on a spike bull at 120 yds. The muzzle velocity was 3050. I hit him square in the shoulder (bad shot on my part) and not a single bit of the bullet got through the scapula. The bullet was fired from a 3 groove Lilja.

This was what I found years ago in a detected pattern among this same type of reports. It is so easy to just blame the bullets, but sometimes we create the storm.

Jeff

 

[Broz]

Yes sir. It's the 140 Berger Elite Hunter. .

The 140 VLD Hunting or Target may have a thicker jacket and they also make a 140 LR hunter too I believe. I would look for jacket thickness and try something else in your barrel. It would be very interesting to see if you notice a change.

EDIT to add: I dont think the hybrid line will be better.

https://bergerbullets.com/product-category/bullets/?caliber=6-5-mm

 

[J300UM]

I might give one of the others a try and see if their performance is a little more consistent and predictable.

 

[Mark Carew]

I am very new here; this topic is very interesting and timely for me. Yesterday at the range, I had 67 grain match bullets keyhole most every shot at 100 metres out of my 6 mm AI; at first I couldn't get on the paper. I tried at 25 metres thinking my sights were way off, yet the results were predictable round holes. Back to the 100 metres, two bullets keyhole first try. I thought the bullets must be hitting the ground and bouncing up to the target. This is a four groove barrel, one in eight twist. I have heard of this problem from a fellow club member with a Pac-Nor barrel from last year. So tonight, I took at look at the remaining bullets in the box; I can't believe how thin the jackets are on these bullets. Its more like a copper veneer than jackets.

I have been using 140 grain VLD hunting bullets in my 6.5 x 284 Improved with a 32 inch, four groove barrel at 3240 fp/s with absolutely no problem. Tonight, I sectioned a competitor's 140 grain VLD hunting bullet; again the jacket is very thin, too thin to be called a hunting bullet in my book. Perhaps this is the problem, where the jacket is so thin that it separates from the core in flight due to the thin jacket being ripped off the core as one would skin a rabbit? I don't have a camera phone suitable for good pictures, unfortunately.

 

[Choovhntr]

Don’t mean to play devils advocate here, and I have talked to people where 147 eld-m bullets are coming apart on faster twist barrels with 3 and 4 groove, but so far my 4groove 7.5 twist barrel has been ok. Velocity is averaging 2940 and the barrel is brand new at 15 rounds. Not a large sample size I know, but i figured I’d test them out for barrel break in just to see and for a factory option if something goes wrong with reloads on a hunt. This may change though when the barrel speeds up. My rifle is a 6.5 PRC with .188 freebore on a xm action. Short action guys running the .130 for factory ammo may see something different with the bullets closer to the lands.

 

[Choovhntr]

Well I went out and finished the box of factory hornady match ammo with the 147 ELD-m in my 6.5 PRC and wouldn’t you know, first shot didn’t make it to the target. I guess it’s possible I pulled real bad But I doubt it because all other rounds were under 1/2 MOA. So out of 20 rounds, one bullet didn’t make it. So far I haven’t had any problems with the 156 Berger’s which isn’t surprising.

 

[Broz]

Well I went out and finished the box of factory hornady match ammo with the 147 ELD-m in my 6.5 PRC and wouldn’t you know, first shot didn’t make it to the target. I guess it’s possible I pulled real bad But I doubt it because all other rounds were under 1/2 MOA. So out of 20 rounds, one bullet didn’t make it. So far I haven’t had any problems with the 156 Berger’s which isn’t surprising.

Shoot the Bergers or a Cutting Edge

 

[Broz]

To bring this article back up as I feel it has even more merit now than when I wrote it close to 3 years ago. I have recently learned that due to the very problem I predicted, PROOF has now went to 5 groove barrels. At least in their 6.5's and I assume some others. History did indeed repeat itself here.

 

[Georgiashooter]

To bring this article back up as I feel it has even more merit now than when I wrote it close to 3 years ago. I have recently learned that due to the very problem I predicted, PROOF has now went to 5 groove barrels. At least in their 6.5's and I assume some others. History did indeed repeat itself here.

This is good to know. I’ve been steering clear of the proofs for this reason. As a matter of fact, I’m finishing up a 6.5 PRC build on a benchmark CF, 5 groove 7.5 twist. This barrel is a little heavier but I think the bullet making it to the destination is a great trade for a few ounces!!

 

[Jasent]

Very interesting thread.
I have a 243 that’s 28” 1:7 twist 5r
For fun I tried 64gr Berger coulomb bullets in it see haw fast I could get them or if they’d pop. No trouble at all even at 4K. Same results with 58gr vmax’s.
I’m thinking the radius shape of the lands does help not tear up the jacket

 

[Broz]

Very interesting thread.
I have a 243 that’s 28” 1:7 twist 5r
For fun I tried 64gr Berger coulomb bullets in it see haw fast I could get them or if they’d pop. No trouble at all even at 4K. Same results with 58gr vmax’s.
I’m thinking the radius shape of the lands does help not tear up the jacket

5 R or 5C barrels have been good to me

 

[Canadian Bushman]

Anybody throwing bullets apart with a cut rifled barrel?

 

[OSOK - Crash]

5 R or 5C barrels have been good to me

Does anyone know where I can find a pic or illustration of what 5C rifling looks like? Trying to visualize it isn't helping.

 

[Broz]

Anybody throwing bullets apart with a cut rifled barrel?

Oh heck yes. All PROOF barrels are single point cut rifling I am pretty sure and the biggest part of this storm this time was Proof's with 147 ELD M's in 6.5 PRC's

 

[matt_3479]

Hey Jeff,

I also found this topic extremely interesting. The question I have is, this issue is more known on velocities pushing 3000+fps and fast bullets? The reason I’m asking is because when you look at br records and such a lot of guys shoot 4 groove Krieger barrels. Now I know a lot of them are running different bullets then we use but I don’t recall reading or hearing many issues with that crowd. Would this be partially due to bullet and velocity’s they are running such as 6 br’s, 30 br’s, 6 dasher etc?

When I was purchasing my 2 20 cal barrels and my 224 barrel I was recommend from 2 different manufacturers to go 6 groove due to this issue.

 

[Canadian Bushman]

Oh heck yes. All PROOF barrels are single point cut rifling I am pretty sure and the biggest part of this storm this time was Proof's with 147 ELD M's in 6.5 PRC's

Have you ever slugged one of your proof barrels?

 

[Broz]

Hey Jeff,

I also found this topic extremely interesting. The question I have is, this issue is more known on velocities pushing 3000+fps and fast bullets? The reason I’m asking is because when you look at br records and such a lot of guys shoot 4 groove Krieger barrels. Now I know a lot of them are running different bullets then we use but I don’t recall reading or hearing many issues with that crowd. Would this be partially due to bullet and velocity’s they are running such as 6 br’s, 30 br’s, 6 dasher etc?

When I was purchasing my 2 20 cal barrels and my 224 barrel I was recommend from 2 different manufacturers to go 6 groove due to this issue.

Velocity is definitely a factor. So is very thin jackets. You mix the two, as with a 147 in a 4 groove with decent velocity and you have the perfect storm.

 

[Broz]

Have you ever slugged one of your proof barrels?

Yes, the one that was tumbling bullets at 100 when I had two barrel for the rifle. The one tumbling the bullets was tight in the middle. The other one shot them ok

 

[matt_3479]

Velocity is definitely a factor. So is very thin jackets. You mix the two, as with a 147 in a 4 groove with decent velocity and you have the perfect storm.

Is there a place for 4 groove barrels in your mind? So if 6 groove are best for small caliber high velocity, and 5r or 5c are best for medium calibers+ high speed to average speed when would someone look into getting 3 or 4 groove barrels

 

[Broz]

Is there a place for 4 groove barrels in your mind? So if 6 groove are best for small caliber high velocity, and 5r or 5c are best for medium calibers+ high speed to average speed when would someone look into getting 3 or 4 groove barrels

Short answer is No. I have only one 4 groove left, and it will be the last one. All the barrels I have other than that one are 5 or 6 and all I have on order are 6 groove. Even my newest 338 is a 6 groove.

 

[Canadian Bushman]

There are so many facets to this problem. Thats part of the reason why you hardly ever get a consistent cause-effect scenario.

A major contributor is button rifled barrels with a low number of lands. This results in the button displacing a larger area of material and sometimes leaving insufficient lands forming knife edges which cut into the jacket.

Ive had 3,4,5 and 6 groove barrels and done so with very little problems. Land configuration only exaggerates problems with manufacturing. It is NOT the only or even MAIN contributor.

Manufacturing is huge. If someone is making barrels with worn out tooling, improper procedures, or specialized tooling with “custom geometries,” a lot of wacky stuff can happen.

Another common condition is smearing of a jacket in the throat when a heavy bullet ( high inertia ) is forced into a tight twist barrel rapidly. Usually this gets worse with longer throats, shallower lead angles, worn throats, and obviously faster bullet velocities.

The one factor that exaggerates both these conditions is thinner bullet jackets. Thin jackets are great. They offer lots of great characteristics to bullets performance, but when they come apart you are obviously too thin for your combination of factors.

The best way to determine what is causing you bullets to come apart is to look at a few key points.

Bullet RPM
Maybe one of you guys can correct me but i feel like 300,000-320,000rpm+ is where things start coming apart pretty easily. If you shooting here you may see very small factors causing issues. Also you may wanna look at mono’s just for the sake of balance and durability.

Rifle throat
If your throat is worn out, fire-cracked, or showing ratcheting, this can be a cause. Some hot rod rounds get crazy once the throat wears past a certain point. If your gun was shooting great, then suddenly bullets start coming apart. Look here first.

Barrel rifling
Slugging a barrel can tell you a lot. It will also allow you to see what the rifling is imprinting on the bullet. Which sometimes can appear quite differently than what one would suspect by scoping a barrel and just looking at the rifling. Gain twist are a good example of this.

Bullet jackets
This is the easiest and the first thing to try if changing barrels isnt a good option for you. Switch to a thicker jacketed bullet and see if it goes away. We all have gobs of bullets laying around. By now we know which ones are thick jacketed. Its just an easy test to run.

 

[Canadian Bushman]

One more thing.

Bullet inertia is directly proportional to bullet weight. The area of a bullet grows on the square to surface area. So as bullets get bigger they have much more weight to surface area than a smaller bullet has. This is why their BC’s get higher, right?

So if we are using rifling around the surface to drive the bullets entire mass down a barrel, eventually we are gonna get to a point where the drive side of the rifling just isnt enough to get the bullet rotating.

This is why tanks, howitzers, and naval guns have 68, 84, or 100+ grooves all an 1/8 of an inch deep. They do this to increase the area of of the drive side of the rifling to handle the stress of initiating the rotation of large projectiles.

So as you guys keep going up in bullet diameter and shooting heavy for caliber bullets with big cases full of slow powder. Keep this in mind.

 

[Rhovee]

Almost all of the BR shooters use 4 groove currently. I have recently seen some extremely impressive groups with a Lilja 3 groove 300 saum improved by Wheeler. It's a hunting rifle and dude is shooting VERY impressive groups with it. 3/8" at 200, 5/8" at 300. Very repeatable. 185 Juggernauts at 3000 fps with 24" barrel. RL 15.5.

I do prefer a 5R or 5C for my larger rifles. They seem to take more powder. With the odd number of grooves I don't think you can get as concentric of a throat, but I can't make it show on paper. How deep the grooves are cut seem to be more of an issue for me.

 

[matt_3479]

Short answer is No. I have only one 4 groove left, and it will be the last one. All the barrels I have other than that one are 5 or 6 and all I have on order are 6 groove. Even my newest 338 is a 6 groove.

Thank you, so between the 5 and 6. Have you noticed differences? Why to go one way over the other? A preference for a specific reason? Is there anything related to velocities, accuracy, cleaning, longevity or calibers to go 5 over 6 or vise versa

 

[Broz]

Thank you, so between the 5 and 6. Have you noticed differences? Why to go one way over the other? A preference for a specific reason? Is there anything related to velocities, accuracy, cleaning, longevity or calibers to go 5 over 6 or vise versa

No, I haven't seen any difference between 5R 5C or 6 groove. But I am only one source of data. Others may be better versed on this. I will say that I have never owned a 6 groove that didn't shoot well. Some of the best shooting barrels I have seen in all times were Hart Barrels and they have been all 6 groove. Some people like even numbers so there is a lan across from each lan offering an equal load. That kind of science is above my pay grade.

 

[dennisinaz]

I thought i would weigh in, i had two barrels that ate bullets. The first was a Chanlynn 8 twist left hand 6.5. It was shooting .1 and .2 @ 200. I cleaned it good and sent it along with 3 others to be melonite treated. It shot good for another 60 rounds and then started destroying bullets; 4 into ¼" and one 12" away. Then a bullet would not hit the target. Mostly i used 130 Norma Diamonds.140 Bergers were right behind. This was way before ELDs were even on some engineer's RADAR. I messed with that barrel quite a bit. I sent it to a large barrel manufacturer who bore scoped and lightly lapped. Still terrible. I pulled it.

Second one is a Winchester 70 in 22-250 that i had Danny Pedersen rebore to 708 ( sentimental rifle) it also would throw a bullet out if group. We lapped it with appropriate flex- hone and it works fine.


I think both barrels ended up with really sharp corners which cut the jackets. The Pedersen barrel is 6 groove. I believe the Chanlynn is 5.

I just got an 8 twist 22-250 so I'll try to year some jackets with it. Point is, there is some misunderstood dynamic at play that rates is ugly head on occasion