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Re: Back yard shooting

Postby Grimstod » Sun Jan 19, 2014 9:12 am

Jerry they are jumping a freakishly long way. 0.032 Wish I could find longer bullets. This really limits my options to experiment.

So how far should you let the bullet jump to the lands? Every book I read on reloading says that seating you bullets to deep has a detrimental affect on accuracy in most cases. Another correlation I have noticed is that as a barrel gets shot out the lands move father forward and so accuracy goes down.
I have a brand new Lothar Walther Barrel and the distance to the lands is far out. Using Seirra HPBT 174gr seated just badly into the brass I still have like .032 to go to the lands. I had planned on experimenting but seams like I can only move the bullet deeper. Cannot get it any closer. I feel rather cheated here cause I can't really experiment like I would want to.
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Re: Back yard shooting

Postby Shepard » Sun Jan 19, 2014 3:48 pm

Here is the article on OAL. The books say one thing and the professionals say another. The numbers they give in the books are to make sure you don't over-pressurize the the chamber. You can load the bullet as long as it stays in the case. I measure each chamber of each rifle and it gets its number for AOL.


http://www.larrywillis.com/OAL.html
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Re: Back yard shooting

Postby Grimstod » Sun Jan 19, 2014 5:47 pm

A good article Jerry.

Here is somthing I found helpful in it.


" Finding the optimum OAL for maximum accuracy usually requires you to reduce the distance that the bullet travels before it contacts the rifling. This also helps maintain concentric alignment between bullet and the bore, so that your bullet gets a good start down the barrel. "
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Re: Back yard shooting

Postby Shepard » Sun Jan 19, 2014 6:45 pm

I not sure you will understand this -- I have a throating reamer which cuts a forcing cone in the beginning lands. I taper the lands - remember there only .004 high -- with a squared edge at the end where the chamber reamer stops. I remove a little bit off the lands right there so it has a funnel effect or a forcing cone is the right term. That way the bullet enters the bore without hitting the abrupt edge of the rifling. This way when you "long" load to fit the gun it doesn't have that dangerous pressure spike trying to get the bullet started. You know -- like in the article - the car trying to drive over the bumper block.
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Re: Back yard shooting

Postby Grimstod » Mon Jan 20, 2014 3:14 am

Yes I understand this stuff. Jerry can you ream te chamber deeper to fix this? I may have to draw up how I want it done. Should be pretty simple. Will have to make the extractor groove deeper and take some metal of the shoulder of the barel so it can thread in one turn. Not to hard a thing to do. I already have it planned out in my head.
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Re: Back yard shooting

Postby Shepard » Mon Jan 20, 2014 5:13 am

Grimstod wrote:Yes I understand this stuff. Jerry can you ream te chamber deeper to fix this? I may have to draw up how I want it done. Should be pretty simple. Will have to make the extractor groove deeper and take some metal of the shoulder of the barel so it can thread in one turn. Not to hard a thing to do. I already have it planned out in my head.


What I do can be done with it assembled. With the problems you've been talking about, --- cutting the chamber deeper will not get the bullet closer to the lands. Did you ever ask Lothar who makes there reamers, mine came from PT&G. They are ground to SAAMI standards. With reaming the throat will make your problem worse, I was commenting on the AOL article. It is the nature of the beast, ask around the forums your on -- most guys have the same problem you're having getting the bullet close to the lands.

I long load -- the rounds I gave you were to long and you wanted me to re press them after they were crimped [remember]. When I long load there may only be an 1/8 or so of the bullet in the brass then I crimp to hold it in place -- keeping it .014 off the lands. This allows it to build pressure before the bullet pops out the case and enters the rifling. This is the only safe way of increasing your bullet speed with out adding more powder or changing powder. I don't worry bout the high pressure spike cause the forcing cone is tapered and causes the bullet to line up to the bore without the big bumper block like in the article.

Also in talking with Ken from RSI, he suggests that you crimp ALL rounds. Don't matter who makes or loads it -- even surplus with steel cases. Makes the claim that it improves your grouping ability. Being he's a more then qualified shootist and manufacturer -- business owner who uses hand loads to test his own produce I believed him and use his suggestion.
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Re: Back yard shooting

Postby Grimstod » Mon Jan 20, 2014 3:00 pm

"Finding the optimum OAL for maximum accuracy usually requires you to reduce the distance that the bullet travels before it contacts the rifling. This also helps maintain concentric alignment between bullet and the bore, so that your bullet gets a good start down the barrel."
"In most cases a -.002" jump to the rifling is ideal."




Jerry I was talking about your reamer and using that to Moving in the chamber a little deeper to take some off the shoulder of the barrel and deepen the extractor groove.

I don't want the lands to have a forcing cone. This is bad for VLD bullets. Here are some drawings of what I am thinking.

Image
Image
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Re: Back yard shooting

Postby Shepard » Mon Jan 20, 2014 4:09 pm

Grimstod wrote:"Finding the optimum OAL for maximum accuracy usually requires you to reduce the distance that the bullet travels before it contacts the rifling. This also helps maintain concentric alignment between bullet and the bore, so that your bullet gets a good start down the barrel."
"In most cases a -.002" jump to the rifling is ideal."




Jerry I was talking about your reamer and using that to Moving in the chamber a little deeper to take some off the shoulder of the barrel and deepen the extractor groove.

I don't want the lands to have a forcing cone. This is bad for VLD bullets. Here are some drawings of what I am thinking.

Image
Image


Your over exaggerating your drawing -- throating as I do it is much shorter. Start at the end of the chamber -- remembering that the lands are .004 high in a .308 barrel. I remove about .002 off the lands. There is no free bore without rifling. Back your tapper back so half of it is not there. Please remember the rifling starts at the end of the chamber - throating only removes a small amount - not all. If you have a bore with no rifling in it -- that wasn't me -- that was the people who made your barrel. Even if I was to re-cut your chamber with my reamer -- you will have the same as your started with. PT&G ground my reamer to SAAMI standards. You can cut 5 inches off your barrel re thread it and chamber it with mine or any other reamer and you'll have the same problem -- it the nature of the beast.

In my opinion you have the best of the best. Your chamber is as short as it can be. If you remember the day we put your barrel on your receiver -- I cut the face of the barrel so when we put a round in it there was .001 spacing between the inside of the cartridge rim and the chamber or barrel face. This keeps your brass as close to perfect as possible. It also alleviates the need for a Bump die that forces the case shoulder back down into the proper position. This is a step thats necessary if you neck size only but can be eliminated with proper barrel setup. If you neck size only without the proper setup -- after about 2 or 3 reloads you will find it hard to close the bolt till you Bump the should back down. This is why I full size a case every 3 loads. Anneal after 3-4 reloads keeps your brass healthy.

Please post your info on VLD bullets
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Re: Back yard shooting

Postby Shepard » Mon Jan 20, 2014 4:54 pm

I'm going down to the Reloading part of the page.
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Re: Back yard shooting

Postby Grimstod » Mon Jan 20, 2014 5:31 pm

Sorry the drawing was rushed and I had a bad surface to work on.
Here is a better one. I am thinking about this for my Desh project.

Image
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