Bore riding dia

[Flexy]

Hi there,

I'm brainstorming the right dimensions to order two molds from Mountain Molds... Bore riding diameter is what is bugging me. I already got some clarifying answers from Dan at MM... But what have you got to give me about this? Bore riding part would be seated within the brass, so it would not affect chambering of the round. I use the brass in only one gun, Marlin 1895 levergun 45-70 Gov, with micro grooving (12 grooves). So I dont need to resize them after shooting. I have used (and want to use) Lees Factory crimp tool for crimping. And Lees undersized molds, which had to be lapped severely to get the accuracy / get rid off keyholing... Also the push thru sizer had to be lapped to .4606 in the same tinkering session... After those, I got rid of keyholing and gained long distance accuracy.

OK, the question. The bore riding part, can it be larger than the bore diameter? I'm planning on using gas checks, so there should be no lead fouling because of the bigger than bore dia bore riding... And chambering issues should not arise, as that part would not be so far out the brass to meet the rifling after throat.

The main reasons for thinking about bigger than bore dia bore riding part is the fact that I've encountered some problems while lapping push thru sizing die and Lee undersized molds suitable for micro grooved barrel... namely the fact that bullet "fall" down in the brass during or after the crimping. I'm not using compressed load.

OK, thanks for any insights you might have. :)

[popper]

Bore riding part would be seated within the brass, so it would not affect chambering of the round
Then it isn't a 'bore rider'? IMHO. a bore riding boolit has drive bands in the case, bore portion chambers into the bore and nose may touch the lands. By that definition, the RD design in my MG 30/30 shot well. I've read that bore riders don't do well in MG barrels but have no evidence. I always size cast boolits to cull any undersized ones out of the mould.

[W.R.Buchanan]

Yes we need to define Bore Diameter and Groove Diameter.

Bore Dia.: is the hole size that is drilled and reamed thru the barrel blank prior to rifling. The material left after rifling is called the" Lands."

Groove Dia.: is the depth of the grooves created in the rifling process.

Typically grooves are .004-.005 deep on a side which means that if the Bore is .450 then the Groove Dia. is probably around .458 .

The nose section of the boolit, or the bore riding section, in this case, should be just below the bore dia. IE .449-.450.

The driving bands of the boolit want to be .001-.002 larger than the Groove Dia. so as to create a good seal in the barrel.

Bore Rider boolits are designed to establish the alignment of the boolit in the barrel prior to firing, as opposed to non bore riding designs where the boolit jumps from the case to the rifling and whatever the alignment is at the point of entry is what you get for that round.

However the biggest problem here is the fact that a bore rider boolit probably isn't going to work in your 1895 simply because the OAL of the cartridge can't be any longer than 2.550 which limits the nose section of the boolit to .450 long since the case is 2.100. The gun physically won't swallow a longer boolit unless you single load it.

This is why boolit designs like RCBS .45-300FN, .45-405FN,and .45-500FN have been so successful in these guns. They were designed specifically for Marlin and Winchester Leverguns with Tube magazines. All have the exact same nose section and the weight increases are gained by lengthening the boolit below the crimp groove creating more driving bands in the process..

Boolits like Lyman 311299 are very successful in .30 caliber rifles simply because the boolit is still able to fit into the magazine of the gun and yet when chambered the Nose section ,,, or Bore Rider section, is pushed into the rifling and functions exactly as intended.

Now if your gun was a single shot rifle such as a Sharps or High Wall, the bore rider design could be utilized to it's full extent.

Hope this helps your understanding of this subject.

Randy

[runfiverun]

Read what Randy typed again..

you are confusing the drive bands with the bore ride nose.
I want a bore riding nose to engrave the rifling by .001 or more but no more than .002.
most lever guns will not allow this, the 30-30's will, and I take advantage of that in them.

[Flexy]

OK, this clarifies it. Then, what I really want, is more driving bands. Thanks. :)

[44man]

I can't add anything, it has been explained as good as it gets.

[JimP.]

simple test, stick the bullet nose first in the end of the barrel, the bore riding bullet will go in and stop on the driving band, if its not a bore rider it will hang up past the ogive of the bullet and appear to be full diameter. I shoot single shots and only cast and use bore riding bullets, my fav is the SAECO 881, 500 gr round nose.