I started the thread “Why all the lube grooves.” To see what is known about the need for multiple lube grooves so perhaps they could be eliminated. The thread has morphed into an interesting discussion about breech seat and especially breech seating with gas checks in bolt actions. Individually breech seating the bullet is an appealing idea. The known drawbacks are complicated devices and loading time at the bench. Nothing wrong with the fuss and I kinda like doing it myself but it is slow and complicated. I will be interested in the outcome of this experimentation being discussed on the Why all the lube grooves thread. However I am even more interested in doing breech seating or a close enough approximation to breech seating to get the good out of the principle but with fixed ammunition which would eliminates a lot of the fuss. It seems to me that John Ardito essentially accomplished that years ago with a system of bullet design, swaging, and fit to throat that shoots as well as the best breech seaters. Others have done it with different bullet designs and swaging bullets into a die cut with the same reamer as the throat. My interest is to find a bullet design that will approximate the benefits of BS in a factory chamber and without the swaging step or the custom chamber. What I have been shooting in competition is pretty close but limited by non-custom match grade barrels and throats, factory triggers, and my shortcomings. That is why I was trying to determine if those extra grooves were of any use. Although there are theories about what they might do that is useful as far as I know none of it has been proven. I think the main reason for them is that they were needed for black powder and now may just be customary. The only way to find out is with a bullet designed without them and with good fit at the time when only a short length bullet is in the case. It may take stepped case mouths and other tricks but progress in this direction would benefit competitive shooters in production or hunting rifle class and any of the military classes as well as anyone else wanting better accuracy in a factory rifle. How close are we coming to breech seating with fixed ammunition? And what is the best way to proceed? John
How close can we come to breech seating with fixe ammo?
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John,Your options are extremely limited if you can't throat the chamber. I believe production class does allow throating and the Hunter class doesn't, right? So, for Production, you can have a freebore that takes all the bullet, accept the GC. But, here you limit yourself to a paticular bullet design. For the Hunter class, all that you can do is to use a long bore rider and match the first band or multiple bands to the leade angle. Using the bolt to push the bullet with a steped mouth case, won't get you very much, at all with a bullet over 12 BNH. I designed a 270, loverin style bullet (160 gr) to do just that, using steped bands to match the taper of the leade. I only shot it once so, the jury is still out (2” group @ 100). The velocity was limited with that powder cavity (2.25 cc) to under 1700 fps with 4227 & 300MP in that test. I'll try a nearly full case of Varget, next time out. It's a machined case with a .272 hole back to the primer pocket and a .279, to match the base bands. It starts out jamed into the throat about .010, enough to engrave the bullet on all the throats area. For a long throated Production rifle, you can make a solid brass case and push the bullet in as far as the freebore will allow and adjust the freebore to get all but part of the GC in the throat. You could go shorter or longer with a adjustable, bullet size piston inside the case. You can, of course do the samething in the Heavy and Unrestricted classes. My 270 mold that matches the 270 Winchester throat. Frank
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What caliber?
I lapped the RCBS 165 Sil mould to make bullet bands larger and bore ride section .0005-.001 larger and more round. I then “lapped the throat area of barrel LARGER to accept the new larger size bore rider bullet". This allowed for easier chambering and extraction of loaded rounds, but also kept bore ride tight during trip down barrel. I can load rounds that have a better/longer over all length (front band touches rifling when chambered). My rifle has a free bore length of .090.
7mm-08 brass is longer and can be formed to 308 and be trimmed to longer 2.030 length. Case will shorten to 2.025 when fired.
Lately I have had good results using my 308 with 22grs of 4759 powder (1900fps), Wolf LR primers, RCBS 165 Sil cast with linotype (water quench), Lyman Moly lube.
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Things to consider:
Production rifles have up to .004 - .005 clearance between the chamber neck and cartridge neck.
When the powder gas expands the case, there is no way to keep the part of the bullet that occupied the neck, in alignment with the throat and barrel.
That same part of the bullet is free to expand itself (with enough pressure)to the limits of the expanded neck. It then has to conform back to the shape of the throat and barrel.
Remember that in front of the case mouth, there is a transition from the chamber neck to the throat or freebore. In most modern chambers that is 45 degrees and at can effect the size and transition back to the throat.
The hardness of the brass effects all the above, too so, two cases that have a different neck and shoulder hardness, can act differently.
BSing eleminates all the above and starts the bullet straight and concentric, into the bore.
Just thinking about it, I would say that the best bet for a Hunter chamber, would be to have a long bore rider with the base band, the width of the freebore and the GC (if used) next to base band.
Then put the grease groove and the front band in the taper of the angled leade. That band as large as it can be and still seat the bullet, say .304 in a .308 barrel and transition at the leade angle down to the bore ring nose. I would also start with the nose .002 over bore diameter to get as much purchace on the lands as possible.
Frank
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The RCBS 165 Sil bullet has a short enough band area so that you can get most of it inside freebore for good support. Gripping just the base of bullet with case neck, some bore riders are short enough to fit magazine.
Bore riders are boring, but can be made to shoot just as well as tapered designs IMO.
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The lapping, while being helpful, wouldn't comply with the rules in the Hunter class.
Frank
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How close are we coming to breech seating with fixed ammunition? And what is the best way to proceed?
John
I have been thinking about breach seating my Remington 700. I have read that you can put Dacron inside case to prevent powder from spilling. You may have to design a special bullet with very short band surface.
Is their an advantage? All of bullet is tapped into Free bore and throat with wooden dowel (guided by dummy case with hole drilled larger at primer pocket). A short band surface may slip/skid on rifling when fired? A factory rifle with long free bore (longer band surface) would have advantage. My factory Remington has a free bore length of .150"...longer would help more.
Would this guarantee better accuracy over fixed ammo?
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My friend Harry Williamson shot benchrest with a 30BR...he would bump the bullets ala Ardito and then turned the case neck, fire form and leave a donut inside the case...this shoulder was whatever distance he needed to force the bullet into the throat...seemingly breech seating with fixed ammo..the chamber was cut to fit his brass by one of the benchrest gunsmiths at the range I shoot at....Harry was a SEABEE in WWII, in the South Pacific and succumbed to cancer this year...look back in the fouling shot and his name appears
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It's a good question, and I wouldn't use the word “guarantee” very much when dealing with cast bullet shooting. However, breech seating the bullet to full engraving will eliminate the launch from the case neck, when even a tight chamber will leave the bullet somewhat unsupported for a fraction of a second as it moves into the rifling.
Larry Gibson has done several tests using his Oehler 43 Personal Ballistics Lab, and on the graphic printout of the bullet's pressure curve there is a small “blip” that signifies a slightly lower pressure AFTER the bullet leaves the case neck but BEFORE it engraves in the rifling. Breech seating would ensure an absolutely straight launch of the bullet, and down the road we'll have Larry do some breech seating to see if this method results in a more even pressure curve.
As for John's original question about how close we can get to breech seating with fixed ammo, my personal observation would say “not close enough", unless we start loading bore riders with undersized noses, or possibly size down the noses of other types bullets (I have a nose sizer made to fit in a Lyman 4500), but this form of loading has never given me any appreciable increase in accuracy.
Oh BTW I don't think dacron is the optimal method to stop powder spillage. Frnkeore mentioned floral foam; I'll be trying that before anything else.How close are we coming to breech seating with fixed ammunition? And what is the best way to proceed?
John
I have been thinking about breach seating my Remington 700. I have read that you can put Dacron inside case to prevent powder from spilling. You may have to design a special bullet with very short band surface.
Is their an advantage? All of bullet is tapped into Free bore and throat with wooden dowel (guided by dummy case with hole drilled larger at primer pocket). A short band surface may slip/skid on rifling when fired? A factory rifle with long free bore (longer band surface) would have advantage. My factory Remington has a free bore length of .150"...longer would help more.
Would this guarantee better accuracy over fixed ammo?
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Lot's of good comments. I have some comments on the comments.
Frank's comment in post#2 That for a factory chamber and throat a long bore rider is the best matches my efforts and it works fairly well if you can get the right dimensions. OU812 comments on the RCBS 165 SIL describe an example of approaching this with a commercial mold. Frank's “Things to consider” list sets out the problem as I too see it. As far as his proposed solutions the idea of a front band with tapered to match the leade sounds great but I have not been able to actually get that in a custom mold and have decided it is something I may be able to do without. It seems to me that the trick is to find that right dimensions for the bullet that will minimize the amount not supported when chambered but have enough driving band to avoid excessive skidding and still be able to chamber with reasonable force. I believe finding those dimensions will require being able to examine fired and undamaged bullets for one thing. Bjornb says: “my personal observation would say “not close enough", unless we start loading bore riders with undersized noses.” I believe you can get close enough to make it hot on other competitors using other approaches in the classes for factory chambers. I agree that a bore rider seems the only way to go for factory chambers and that's what I am trying to do except I am puzzled by the “undersized” description for the noses. The ideal size for noses would be big enough to get full length engraving and as deep engraving as possible without making chambering too difficult. Of course this depends on several things including alloy hardness. John
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My attempt at breach seating. Here is a bullet that I had drawn up and had Tom at accurate Molds cut for me. 31-220-T. It turned out to be 220 gr.bullet bore riding shooter and is only held by the case just a little past the gas check. Seating depth past the neck is .110. Bullet cast from my mold .3005 on the nose and .310 on the driving band. I shoot the bullet in my Remington 700 SPS Varmint rifle in 308W. I made no changes to the throat and size the bullet .3095. The nose is supported in the bore and the tapered part of the bullet in front of the lube grove is seated into the lands when loaded. OAL is 3.095. If you look real close at the picture you can see the marks from the lands on the bullet. On the target the first shot went high out of the clean barrel. The 10 shot group discounting the first shot measures about .850 C/C. I load 27 grs. 3031. Mr. Bill2
mrbill2
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Accurate Molds is a good, inexpensive source of molds, The only reason that I've not used him, is becauce he won't make spitzer noses. I think he would get between 1/4 and 1/3 more business if he would.
Frank
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John Alexander wrote: Lot's of good comments. I have some comments on the comments.
Frank's comment in post#2 That for a factory chamber and throat a long bore rider is the best matches my efforts and it works fairly well if you can get the right dimensions.
OU812 comments on the RCBS 165 SIL describe an example of approaching this with a commercial mold.
Frank’s “Things to consider” list sets out the problem as I too see it. As far as his proposed solutions the idea of a front band with tapered to match the leade sounds great but I have not been able to actually get that in a custom mold and have decided it is something I may be able to do without. It seems to me that the trick is to find that right dimensions for the bullet that will minimize the amount not supported when chambered but have enough driving band to avoid excessive skidding and still be able to chamber with reasonable force. I believe finding those dimensions will require being able to examine fired and undamaged bullets for one thing.
Bjornb says: “my personal observation would say “not close enough", unless we start loading bore riders with undersized noses.” I believe you can get close enough to make it hot on other competitors using other approaches in the classes for factory chambers. I agree that a bore rider seems the only way to go for factory chambers and that’s what I am trying to do except I am puzzled by the “undersized” description for the noses. The ideal size for noses would be big enough to get full length engraving and as deep engraving as possible without making chambering too difficult. Of course this depends on several things including alloy hardness.
John
John,what I mean by “undersized noses” is actually what mrbill2 is showing in his post. He has a bore rider that is perfectly matched to his rifle, and then I cannot call it undersized. However, testing has shown us that bore riders are only accurate up to a certain velocity; past this we need more bearing surface for accuracy. Here's a picture illustrating what we are working with: 
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Obviously trying to breech seat this bullet with fixed ammo won't work; it will get pushed back into the case. So you would either need a bore rider bullet, or else use a Nose Sizer (I have one, made by Buckshot over on Cast Boolits). It uses Redding style neck sizing bushings and will size the bullet nose down to match your bore dimension.
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If that bullet is the NOE 165, it's actually a re-sized tapered nose at tapers down to .299, It has bore riding aspects, you might call it a simi-bore rider, as it would be in the bore riding class until half way up the nose.
I'm not criticizing it, just classifing it. The nose is very simular to the RCBS 200 Sil.
Frank
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Well, this bullet is currently outshooting every cast bullet I've ever tried, at all velocities and in a multitude of rifles, and it's the bullet that Tim specifically made his breech seater for. It starts engraving immediately past the ogive: (Never mind the flat nose from beating it out of the bore)
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"I'm not criticizing it, just classifing it."
BSing is very design tolerant, as long as it doesn't take to much effort to get it in the barrel. I've always looked for higher BC's to help wind drift, too. Frank
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I know you weren't criticizing it Frank, I just wanted to brag about the bullet. Al Nelson at NOE did a great job with Tim Malcolm's design.
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Just a note: The cases I'm currently using are on the short side at around 2.005. I'm working on some longer cases made from 06 brass the will chamber in my rifle at 2.034, but need the make a mandrel to turn the necks. I should then be able to shorten the bullet by .020 from the rear and that along with the longer case move the bullet forward another .020. and still hold the bullet by just .110. I'm thinking that might improve performance just a bit. My velocity currently is 1800 fps.. All I'm doing is target shooting and that seem to work ok to punch holes.
mrbill2
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