.375 Winch BB94 free bore problems

[R J Talley]

Veral, I bought a late 70s very early 1980 BB 94 in .375 Win a few months ago. Since that time I've fiddle and fussed with it trying to get it to both shoot and function with cast bullets. I've used both Lyman and RCBS bullets and in the process discovered a few things. First, that dang gun has a throat at least .425" long. I seated a bullet base first and chambered it.
The picture shows the results using an RCBS bullet. Second, to get the gun to feed, I need to seat the bullet out to the middle of the first lube groove and crimp there, not in the crimp groove. Accuracy is only about 2.5" for 5 shots at 50 yrads. Clearly I need a better bullet. What do I need to do? Have you run into this before? Also, it seems the chamber is cut long enough that I can use 38-55 cases without the slightest trouble. have you heard of this in these BB94s?
R J Talley
proud owner of 4 LBT moulds.

[Veral]

  That RCBS bullet looks like one of their better designs, so far as design alone and performance.

  Since your rifle will chamber 38-55 brass and the throat is too long, thats the brass I would use.  Also make your bullets as fat as will chamber easily so they can't tip on takeoff.  You didn't mention whether the RCBS bullet will feed when seated out to fill the throat.  If it does, use the grease groove for crimping but don't fill it with lube.  I see you are using LBT lube, which will easily prevent leading at the speeds possible with this rifle, with only two lube grooves filled. - What I'm saying here is, to see if you gan get a smile with the mold you have, size in the largest sizer die you have, or if your largest die is sizing the bullet at all, push into the sizer just enough to lock the crimp on, finger lube two grooves, seat to crimp in the grease groove that works, and see if it will shoot.  Also, do the same with bullets seated to contact the rifling.  No crimp, and hand feed single shots.  If it will shoot, you'll know the gun is OK as is.  If it won't, the bore probably needs lapping.

  My recomendation is one of my LFN's in the weight you want to shoot, but lean toward the heaviest you'd be satisfied with.  Diameter should be as large as will chamber easily.  It should not be made with a crimp groove, but should have a very heavy driving band up front.  Load this bullet long as possible, so it feeds smoothly and chambers without resistence, and crimp lightly with a Lee Factory crimp die.  If the barrel is smooth and straight, you will be able to do no wrong.  Any load that's safe to shoot (pressure wise) will shoot well.

  The RCBS bullet is definately weak on bearing up front considering such a long throat, and the bullet I would make will fix that problem.l

[R J Talley]

The bullets drop at just about .379. I use a .379 sizer die and only a few spots on the bullet are shiney. Obviously, the bullets are not perfectly round but they are dang close for a factory mould. The bullets will feed if, when using .375 Win brass, I go no farther out than the middle of the first lube ring. This does improve accuracy and it also reduces leading. The tough part is seating the gas checks. I have to open them up a tad first with an arbor punch that is just barely big enough to partially enter the cup. A very light tap with a brass hammer and the check will slip on the heel. Unfortunately, the heel is short and the check uses all of it. If I read your book correctly, the heel should be longer so there is room to hold scrapinging correct?

I want to slug the bore/chamber to get an exact measurement of the throat. If I under stand the process I must first get a steel rod that filles the case even with the mouth. Then I need to get a rod that is a couple of inches longer than the barrel and just a hair under bore diameter. I then warp a turn of tape around this to protect the bore. Then I get a pure lead slug that is just small enough to drop down the bore. i chamber the cartridge filled with the short rod. I drop the slug down a lightly oiled barrel. I lower the longer rod onto it and using a medium weight hammer and a good stout blow, smake the rod (how often?) to casue the soft slug to upset and fill the throat/lead/bore. Is this correct? Did I miss something? Do you have slugs that are close to .375 dia. ?

I think I'm going to have to have you cut me a mould. The twist in this gun is fairly fast, 1/12 IIRC. I'm thinking that may work best with 250-300 grain slugs. What do you think? Factory jacked ammo is all 200 - 220 grain.

[Veral]

  This rifle will stabilize 300 grain LFN's real easy.   With the huge long throat, and probably large diameter, 220 grain bullets are too short, even with jacketed, which probably explains the not to good accuracy with these rifles. (I'm supposing they were chambered so 38-55 ammo wouldn't be dangerous or wedge in the chambers, but made the 375 brass short and thick for higher pressure, which screwed up what should have been a very popular rifle, because people as a whole don't know how to deal with such built in problems. But you do now!) You are pretty close on how to make a chamber slug, and will get exact directions if you order throat slugs from LBT.  We have them for every caliber 22 up to 50 cal.  The rod diameter you'll have to use is 5/16 and will be available at your local hardware in 3 foot lengths, which is enough to cut of both the cartridge filler and the tamp rod.

  Yes, the short check shank is a problem, and is causing your leading problem, because it can't clean up.  If you want to prove me wrong, just file a larger groove ahead of the check on a few bullets and shoot them with a load that now leads.  Even though you'll mess up bullet balance a little, leading will stop and accuracy tighten.