Case design:

[Pete Wass]

I have been wondering if there might be something to be gained by allowing longer necks on cases. Specifically, I make 30-44 cases and have to cut a lot off them to get them down to the "Standard" neck length that came on the reamer I bought. I pushed the shoulder back on a 300 Savage case last evening and noted that I have around .600 of neck to work with. Does anyone know if a longer neck might provide extra life for a barrel? I once saw an article in PS that showed a method of finding the optimum angle to keep the fire inside the case but I give them out to the local gun club at every annual meeting. Can anyone shead some light on this? Thanks, Pete

 

[alinwa]

Pete, pictured below is my 1st design shortened .30 from about '95. It has a long neck This is an ultimate expression of "Protecting The Throat!"

I have no evidence that it lasts longer than it's counterpart with a short neck.

The theory that you're referring to is probably the "Turbulence Point Theory" or TPT as proposed by Mic McPherson back in the day. On paper it looks really attractive with lines converging in the throat and cool vortices full of unburnt powder swirling about...... in REALITY it ain't quite so simple.

I'm an unbeliever.

There are people who believe that the 6MM Rem with it's longer throat is "easier on barrels" than the short necked .243. If you believe this then you may well ascribe it to "TPT"..... If you DON'T believe it then I guess you've experienced differently.


In my case I was experimenting with using the neck as a guiding means to support and center the case. I call this BadBoy the .308 I.C. and it shoots bugholes. JUST like it's shortend version, the 30X47L which has nothing special at all about it's neck and JUST like Nyhus' Wolf Pup which has NO NECK to speak of. Now if Al will chime in and tell us his throats wear out quick.......... maybe I'll start to believe.


Until then???


Nawwwww



al


I just HAD to add this edit, just to pick on TheotherAl from The Forbidden Zone..... Sir Nyhus MAY WELL CHIME IN about his throat wear, but I'll betcha' HIS throat wear comes from howling along with 80's era Rockers!! Yowling along to Aerosmith WILL CAUSE PREMATURE THROAT WEAR!!

 

[Big Al]

A neck length of one and a half times the caliber is considered as a close to ideal neck length, at a minimum.

Of course the thinking behind this is the ability of the neck to hold the bullet while chasing the ever wearing throat/lands.

When you examine the .243Winchester and compare it to the 6mm/.244 Remington the neck length makes it a clear looser when it comes from the hand loaders stand point, the 6mm Remington being the winner.

One of the rules (if you want to call them that) of case design is the one and a half times the caliber, (minimum) for neck length.

It also lets the bullet rest out of the powder, and not seated in the charge.

 

[alinwa]

I can get with that, a longer neck is more versatile, but the TPT theory brings in the idea that a longer neck protects the throat, keeping it from wearing. THIS I don't agree with.

 

[Big Al]

I can get with that, a longer neck is more versatile, but the TPT theory brings in the idea that a longer neck protects the throat, keeping it from wearing. THIS I don't agree with.

For a good discussion on the topic, see "designing and forming CUSTOM CARTRDGES for rifles and handguns" by Ken Howell. Please if you don't have a copy of this book and want it, buy direct from the author and not from PS magazine. I was directly informed by Doctor Howell that PS will not pay him for the sale of his books.

ken1931@gilanet.com
Location: Box 28 (17 Church St), Quemado, NM 87829 — (575) 773-4342

 

[jackie schmidt]

Pete

For the purposes that this Forum Represents, I doubt neck length is of much consequence.

There are many theories floating around about this, many date back even before you and I were born.

How would this be for a test. Take a Rail Gun to Gene Beggs Tunnel. Have one barrel chambered in a standard 6ppc, the other in a 6PPC that is trimmed shorter, but with the shoulder blown forward so that the neck would be about 1/2 as long, but the powder capacity would be the same in both cases.

Arrive at an accuracy potential for each barrel, then shoot them untill you can actually detect a fall off in accuracy.

That would be the only way to answer the question with any degree of certainty. But even then, shooters would say things like, "what about larger cases, smaller, different tapers,etc.

We have a good example of a high capacity case with a rather short neck, that is also a proven chambering for accuracy as it pretains to large cases. That is the 300 Win Mag. Thousands of shooters have much hands on experience, many in the 1000 yard Arena.

It would be interesting to here their perspective.........jackie

 

[Al Nyhus]

alinwa: We've shot the .085 neck length .30 WolfPup for three seasons now in three different guns (two HBR and one VfS) and used seven different barrels....three Kreigers, one Kostyshyn, one Broughton, and two PacNors. All told, Stan and I have spun more than 12,000 bullets down these barrels between testing and competition.

There has been no difference in throat wear when compared to our previous chambers which were essentially a 308W shortened .165 with the standard 308W neck length.

 

[Pete Wass]

Nuf said

I guess if there was an advantage someone would have ascertained it waaaaaay before this. It was the Aardvark that got me to thinking about this. I guess I could have emailed someone who has one and asked them directly but though it might make a good, non-controversial topic to offer.

What's next?

 

[JerrySharrett]

What's next?

Six more weeks of Winter and then.....and then.....and then the Shamrock!!!!

 

[Al Nyhus]

If only those 12,000 rounds through 7 barrels had been via 6PPC chambered Rail Guns....maybe we'd know something.

Sigh..............

 

[HPC]

6mm Giraffe

PS article mid 90's on the 6mm HLS referenced a previous article where a real rocket scientist stated, a 14 caliber neck was required to eliminate flow turbulence with the goal of less throat erosion.

 

[alinwa]

If only those 12,000 rounds through 7 barrels had been via 6PPC chambered Rail Guns....maybe we'd know something.

Sigh..............

"If only if only" the woodpecker sighs, "the bark on the trees were as soft as the skies...."


ahhhhh



al

 

[f d shuster]

Neck & Shoulder

Neck and shoulder angle may be what Mic McPherson has in mind with his 5.35 "pop bottle shoulder": an attempt to keep the turbulance point and powder burn inside the case for better (?) ignition. Also has a somewhat longer neck length: one of the designs of the 222 Rem., especially as compared to the 223. I was always "told" the case neck length should be at least bullet diameter, longer is better. And yet, as mentioned, short neck cases like the 300 Winchester Magnum, and the 223 Rem. can deliver out-standing accuracy. It will be interesting to see how the McPherson design develops over the test of time.

 

[seasterl]

You'll have to forgive my (stupid) questions, but in order to reduce throat erosion, could you just use a slower-burning power and increase barrel length, or would that make it worse? If worse, then what about shortening the case and use a faster-burning powder. What about changing the primer and/or flash hole to get more burn inside the case? (You guys can tell that I haven't read that book listed above, but would love to own a copy so I can read it.) BTW, and this is really off the wall, but isn't this what Weatherby was all about when he designed that funky-looking rounded shoulder. He also designed his rifles to be freebore, if that's what's it's called. I don't know much else about his rifles and bullets, but is there anything that can be learned from him to reduce throat erosion?

 

[alinwa]

You'll have to forgive my (stupid) questions, but in order to reduce throat erosion, could you just use a slower-burning power and increase barrel length, or would that make it worse? If worse, then what about shortening the case and use a faster-burning powder.

I, for one, am working with the faster powder/smaller cases believing that it helps.

What about changing the primer and/or flash hole to get more burn inside the case? (You guys can tell that I haven't read that book listed above, but would love to own a copy so I can read it.) BTW, and this is really off the wall, but isn't this what Weatherby was all about when he designed that funky-looking rounded shoulder. He also designed his rifles to be freebore, if that's what's it's called. I don't know much else about his rifles and bullets, but is there anything that can be learned from him to reduce throat erosion?

I also believe that primer/flashhole can play a part..... and thet Roy Weatherby made lots of money converting the American public to "Magnumites," other than that his chamberings offer no gain.

al

 

[seasterl]

..... and thet Roy Weatherby made lots of money converting the American public to "Magnumites," other than that his chamberings offer no gain.

I agree that he did push the magnums too much, but I didn't know if he was onto something with the rounded shoulder design, even though he did use belted magnums. Suppose the PPC had a rounded shoulder. Would it reduce erosion? I'm sure if there was an easy way to double the life of a BR barrel that the design would change overnight. It would be nice to speak to someone that has tried everything under the sun and said that the current PPC is as good as it gets, or if they'd admit to just not getting around to trying many ideas. That would be a great job, huh? Imagine getting paid to do something like that all day!

 

[alinwa]

I agree that he did push the magnums too much, but I didn't know if he was onto something with the rounded shoulder design, even though he did use belted magnums. Suppose the PPC had a rounded shoulder. Would it reduce erosion? I'm sure if there was an easy way to double the life of a BR barrel that the design would change overnight. It would be nice to speak to someone that has tried everything under the sun and said that the current PPC is as good as it gets, or if they'd admit to just not getting around to trying many ideas. That would be a great job, huh? Imagine getting paid to do something like that all day!

Welll.....

I don't get PAID to test weird ideas but I DO perty much spend my paychecks doing it! IMO The PPC really IS about as good as it gets. There are several other rounds which can hang with it but really nothing to better it in any significant way. And I have spent a few tens of thousands of dollars to find this out.....

al

 

[Bnhpr]

alinwa: We've shot the .085 neck length .30 WolfPup for three seasons now in three different guns (two HBR and one VfS) and used seven different barrels....three Kreigers, one Kostyshyn, one Broughton, and two PacNors. All told, Stan and I have spun more than 12,000 bullets down these barrels between testing and competition.

There has been no difference in throat wear when compared to our previous chambers which were essentially a 308W shortened .165 with the standard 308W neck length.

Al,

What sort of bbl life did you get out of your .165 short 308?

Ben

 

[alinwa]

Al,

What sort of bbl life did you get out of your .165 short 308?

Ben

Ben mine is .200 short and I DON'T KNOW..


I'm only comparing two barrels in 30cal (and following closely the progress of other shooters, like Al Nyhus, Randy Robinett etc.....)

My two barrels are both Kriegers and one is a .308-.200, the other a 30X47L which I've just started to wring out. I've got three stocks for the 30X47L and I've been pounding it trying a get a grasp on stuff like barrel torque, bag setup and the recoil disruption of this hot little round.

The two chamberings are so identical that I use the same Neil Jones fitted die for them, with different bushings of course.

I've only been able to monitor the throat wear on mine by observing the retreat of the lands and the shape of the marks on my bullets. I've only got 1125rds thru the long-necked one and only 800+ through a short-necked one and neither of them show any wear at all using this method of observation. The lands still mark the bullets square and sharp and I haven't had to adjust my seating depth. I'm in murky waters here as many folks claim to "chase their lands" a WHOLE lot more than I do! But I clean very carefully and slowly using a bore guide. I don't heat my barrels up and I shoot fast, efficient powders. I've used H322, N130 and N133 in these barrels and the shortened .308 likes to run at about 3000-3050 where the 30X47L runs hotter at around 3250. The shortened .308 will run up to 3250 but ONLY by wrecking brass so I've backed it down "to the next lower node" IMO.


Because of this my "reason" tells me that these two Krieger barrels should have "similar wear." (The shorter necked one runs hotter but has fewer rounds) And they do, none to speak of.

I admit that my personal experience with these two rounds isn't in any way definitive in this regard. I should also have added that my beliefs regarding throat wear aren't based just on the limited data from these two rounds. I've formed this opinion from the experience of others and from my own experience with other chamberings. For instance I spent 7 yrs dinking with the .243AI, .243 and 6MM in various forms.


Also, and this again runs counter to popular conception, these two .308 chamberings have shot well through their entire lives..... no "break-in" and no falling off yet. I probably will never shoot out the old .308-.200 because it's been supplanted by the new 30X47L, the old one will probably just become a squirrel rifle.... it's now boring. Or I'll rechamber it. Meanwhile I'm using it for fireforming

al

 

[Bnhpr]

Al,

I built a .165 short 308 with no freebore, Krieger 17 twister for an HBR rifle. I have maybe 300 rounds through it. My only complaint is trimming the brass. I have to get a better setup there.

I've heard I might be able to form a 30x47 case into it?

I have an expaniron to neck up 6.5x47 brass? Should I buy the brass and try it?

I'm shooting new brass with H380 and Speer 125 tnt's and then H322 and Berger 110's after that.

The funny part is that I have been doing just as well with the TNT's and H380 as the latter.

Both loads outshoot me.

Ben