Are Lube Grooves Necessary?

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  • Last Post 07 September 2016
cove posted this 26 July 2016

I am in the process of designing a bullet and need some input.  Plans are to have Accurate cut the mold which will be 30 cal, nose ride, plain base, to be breech seated in an 18 inch barrel with a 1 in 10 twist and shot at velocities below 1400fps.  Length will be in the 1.15 inch range to give a bullet weight of around 210gr using 20-1 alloy.  I have had consistent results using a light coating of Lee Liquid Alox and am considering a bullet without lube grooves.  Therefore, my first question is: Are  lube grooves necessary?  Second question: Does a wide groove near the base of a bullet allow the base to obturate and seal the bore?  If so is this this wide groove  a weak point, allowing obturation but creating the potential for the base to upset unevenly producing an unsquare situation? It seems to me that a plain (ungrooved) bullet has the best potential for casting and shooting accurately.  Any comments will be greatly appreciated. Bill Duncan (Cove)     

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Ken Campbell Iowa posted this 26 July 2016

oh oh :: here we go !!

my first thought ( NOT experience ) is that a breech seating system should be chambered/throated such that the breech seating leaves the bullet already fully tightly fitted ....... else why breech-seat ?

regarding grooves ...and base distortion .... consider the 22 rimfire bullet has * almost * no grooves .... and yet it's rebated base is much deformed at firing .....and yet it is amongst the most accurate of the lead shooting rigs .

thanks for starting ( reviving ) a very interesting subject .

ken

well, i do have some experience ... a pope system... harry thought you should breech seat them from the muzzle ...

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RicinYakima posted this 26 July 2016

Don't need lube grooves, but you will need a place for the displaced metal to go. Tail fins effect flight performances.

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onondaga posted this 27 July 2016

http://www.castbulletassoc.org/view_user.php?id=5751>cove

CORRECTLY TUMBLE LUBED BULLETS DON'T NEED LUBE GROOVES.  Tumble lube does not feed out of lube grooves anyway, lube grooves subtract lube area from tumble lube. Take a look at the 30 caliber  PP (paper Patch)  molds offered by Accurate Molds. They have no grooves and you can order to any desired cast size for your specified alloy. If you know exactly what diameter works to fit your chamber throat with your alloy, just specify that in the 30 Caliber pp mold. these bullets tumble lubed should should shoot very well and the flat nose ones make a nice hunting bullet too..

Your 1:10 should handle all the bullet weights but accuracy is usually best with 170 -190 gr 30 cal cast bullets

This one is a beauty for target or hunting, specify the diameter you need, most 30s need .310-.312. Specify exactly what you need:

http://www.accuratemolds.com/bullet_detail.php?bullet=30-172P-D.png>http://www.accuratemolds.com/bulletdetail.php?bullet=30-172P-D.png

If your bullet fit is good and your alloy is selected to match your load pressure, your tumble lube does not have a speed limit.

I use Lee LLA and Whites 45:45:10 Deluxe tumble lube. I like the Whites better, it dries tack free and clear. I pre-warm bullets and tumble lube so my bullets are dry and ready to load  in 3 minutes. I have used both tumble lubes to 2550 fps in .223. My application had no lube failure. I get lube stars on my muzzle at 20 shots with 2 light coats of tumble lube.

Gary

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joeb33050 posted this 27 July 2016

Works for me! You can borrow the mold.

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mtngun posted this 30 July 2016

cove wrote: my first question is: Are  lube grooves necessary?   Second question: Does a wide groove near the base of a bullet allow the base to obturate and seal the bore?  If so is this this wide groove  a weak point, allowing obturation but creating the potential for the base to upset unevenly producing an unsquare situation? It seems to me that a plain (ungrooved) bullet has the best potential for casting and shooting accurately.  Any comments will be greatly appreciated. Bill Duncan (Cove)        This subject came up twice in  Colonel Harrison's book, and in both cases the experimenter achieved better results with a grooved bullet, though they could not explain why.   I also submitted an article on the subject to TFS but dunno if it has been published yet (I'm several issues behind in reading TFS).

Short answer is that you can often get away with grooveless bullets at low velocities, and probably at 1400 fps in your rifle.   As velocities go up, it's important to have grooves EVEN IF YOU DON'T PUT LUBE IN THE GROOVES.    The difference in accuracy can be night and day.

Grooves have nothing to do with whether the bottom most band obturates.

Grooves reduce bullet distortion, not increase it, because they allow the rifling to engrave the bullet by pushing a little lead into the groove rather than squeezing the entire bullet like a tube of toothpaste.

While a grooveless bullet may work fine for your proposed application, anything a grooveless bullet can do, a grooved bullet can do, and more.   

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45 2.1 posted this 30 July 2016

Short answer is that you can often get away with grooveless bullets at low velocities, and probably at 1400 fps in your rifle.   As velocities go up, it's important to have grooves EVEN IF YOU DON'T PUT LUBE IN THE GROOVES.    The difference in accuracy can be night and day.

This is quite true.

Grooves have nothing to do with whether the bottom most band obturates.

That depends on alloy and pressure.

Grooves reduce bullet distortion, not increase it, because they allow the rifling to engrave the bullet by pushing a little lead into the groove rather than squeezing the entire bullet like a tube of toothpaste.

Not always true, that depends on alloy used and load pressure. Grooves on the bullet keep the patch from slipping in higher pressure loads. Recover some fired patched bullets and you'll see it for yourself. Ross Seyfried wrote an article long ago about patching jacketed bullets up to larger odd calibers.... that didn't do well until he roll engraved roughness on to them using a mill file so the patch didn't slip.... same thing here.

 

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joeb33050 posted this 30 July 2016

joeb33050 wrote: Works for me! You can borrow the mold. WernerEWolf cut this mold for me. I've experimented on and off for 20 years with it. It shoots fairly well in any 30 cal rifle so far, a plastic wad seems to help. But, it isn't the MOST accurate bullet in any gun so far. At 100-200 yards. The idea was to increase BC, reduce wind drift. I suspect it would shine > 500 yards, but don't know-nowhere to shoot. Werner also cut a 45 cal mold, NGG, that worked well. Bill McGraw and Mustafa Curtiss tried it. I'm out of the 45 business, sent the mold to Bill a few days ago.

Friction is about area-in-contact, not pressure. Grease grooves reduce area. So, we trade friction for BC. NB, jacketed bullets have o grease grooves.

It is a puzzlement.

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joeb33050 posted this 30 July 2016

mtngun wrote: cove wrote: my first question is: Are  lube grooves necessary?   Second question: Does a wide groove near the base of a bullet allow the base to obturate and seal the bore?  If so is this this wide groove  a weak point, allowing obturation but creating the potential for the base to upset unevenly producing an unsquare situation? It seems to me that a plain (ungrooved) bullet has the best potential for casting and shooting accurately.  Any comments will be greatly appreciated. Bill Duncan (Cove)        This subject came up twice in  Colonel Harrison's book, and in both cases the experimenter achieved better results with a grooved bullet, though they could not explain why.   I also submitted an article on the subject to TFS but dunno if it has been published yet (I'm several issues behind in reading TFS).

Short answer is that you can often get away with grooveless bullets at low velocities, and probably at 1400 fps in your rifle.   As velocities go up, it's important to have grooves EVEN IF YOU DON'T PUT LUBE IN THE GROOVES.    The difference in accuracy can be night and day.

Grooves have nothing to do with whether the bottom most band obturates.

Grooves reduce bullet distortion, not increase it, because they allow the rifling to engrave the bullet by pushing a little lead into the groove rather than squeezing the entire bullet like a tube of toothpaste.

While a grooveless bullet may work fine for your proposed application, anything a grooveless bullet can do, a grooved bullet can do, and more.   Ya know, the experiment results are sorta interesting. But here you're perilously close to the observer who can see exactly what happens from primer hit to exit from the muzzle. That observer rears his head now and again, but when asked, fails to provide photos. There are few times in the CB world when short declarative sentences are appropriate, and this may not be one of them.

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mtngun posted this 31 July 2016

Joe said:  "That observer rears his head now and again, but when asked, fails to provide photos."

Sorry Joe, I was deliberately being stingy with my information in order not to give the article away, if it has not been published yet.   Another bit of data:  in one particular comparison  at 2200 fps, a grooveless bullet could not stay on the target backer, while an otherwise identical grooved bullet shot a 2MOA 10-shot group.   Both bullets were coated & unlubed so it was apples-to-apples.  

My article cites similar examples from the Colonel's book and from one of Seyfriend's articles.   It also covers the function of grooves in solid copper bullets.   

William, perhaps grooved paper patch bullets do serve to help the patch grip the bullet, but that was not what Cove asked.   I dunno if it had anything to do with the Colonel's preference for grooved PP bullets.   PP is not my area of knowledge, but what little PP I've tried also did better with grooved bullets.  

There is a second example of grooved vs. grooveless in the Colonel's book that had nothing to do with PP.   It basically answers Cove's question, though the writer could not explain the how and why.

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358156hp posted this 31 July 2016

The makers of homogeneous copper allow bullets seem to agree that grooving is necessary in most applications. Barnes for example, did not groove their bullet shanks, and accuracy was a hit or miss proposition (no pun intended) in the early days. Another manufacturer was grooving their bullets, which Barnes actively criticized them for. After the original manufacturer faded from the scene, Barnes embraced the banded bullet concept, and uses it to this day. I believe banding was also used to reduce chamber pressures with solid DG bullets, which used harder alloys.

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Ken Campbell Iowa posted this 31 July 2016

grooves, heh ?? i notice that there is a 30 match lead bullet from lapua that has fore-and-aft grooves ( lengthwise ) ....

that would be an interesting way to put grooves into a home-swaged lead bullet .

hey how about pushing a plain swaged bullet through an inch or so of cut-off rifled barrel ?? maybe not deep enough grooves i spose . maybe . next .

ken

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cove posted this 02 August 2016

Well it seems that as with most aspects of cast bullets, the subject of groove versus no groove does not have a definitive answer.  Nevertheless, your input gives me information which I can use in my design.  The idea that grooves gives lead from an obturating bullet a place to go makes sense. Another problem as one of you guys has pointed out above, is swaging of lead at the base of a PB bullet to form a fragile skirt.  I have seen this on recovered  pistol bullets but do not have enough experience with PB rifle bullets to comment.  This morning I came across an article by Merrill Martin in FS #134-11 that states: It has also been shown---that many loads start the bullet out violently and unevenly, pushing on one side of it's base, causing cock.  Thanks again for the input. Cove 

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onondaga posted this 02 August 2016

 the the violent pushing you mention is easily overcome for cast rifle bullets by powder selection, that is why h4895 with its soft start pressure curve is so popular for cast rifle bullets.

Gary

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Myflatline posted this 01 September 2016

I would say the grooves depend on the application.  For this 35 Rem. application, it doesn't need grooves.  Tom at Accurate made it for me.

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Ken Campbell Iowa posted this 01 September 2016

to be continued .... i hope...

all to my nefarious scheme of those evil swaged bullets ....grooveless swaged bullets that is ...

ken

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muley posted this 02 September 2016

what number is this bullet from Accurate??/   thanks, Jim

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Myflatline posted this 04 September 2016

muley wrote: what number is this bullet from Accurate??/   thanks, Jim I had it made a couple of years ago, I'll see if I can find the number.  If not I can send you some samples to try , then have Tom make one.  I thought he had all designs in his catalog, but I didn't see it. Jim Accuracy is very good 

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Myflatline posted this 05 September 2016

All the mold says is 360200M, just no lube grooves. Bullet length is .841 with a gas check

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harleyrock posted this 07 September 2016

Go to Accurate's website, they have that bullet in their catalog.  That may tell you what you need to know.

Lifetime NRA since 1956, NRA Benefactor, USN Member, CBA Member

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Myflatline posted this 07 September 2016

Yes, they list the 200m but not the one with no lube grooves ( that I could find)

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