I have been having trouble with my new 375 H&H. I canget groups of .5 to .75 but the odd one will be as much as an inch away. I have done every thing I can think of. We were checking the run out on the brass and bullets and found that the brass was thicker on one side than on others. When measuring bullet run out do you actually put the dial indicator on the bullet and rotate the shell or do you measure at some point on the neck. The latter was the way I was doing it and was haveing high run out to .oo7. We decided that bullet run out should be on the bullet not on the neck. Is this the right way to measure run out? We also found that the TSX bullets have high variability in olgive as with a in line bullet seater die the rounds all have different lengths. The cure? get different brass and bullets??

Bullet runout is measured with the dial indicator on the bullet nose just forward of the shank.

Case runout is measured with the dial indicator on the neck.

Turn the necks, seat with a match-type seater, take away the runout, and see if accuracy improves. It could be your load too.

quote:

We decided that bullet run out should be on the bullet not on the neck

That is correct; runout should be measured on the bullet, not the neck.

Bullet runout can be caused when pulling the expander ball out of the case. Try polishing your expander ball with fine crocus cloth and be sure to lube the inside of case neck (I use powdered graphite). This will reduce friction somewhat and help runout.

I was having trouble w/30-06 long range target ammo and found that the expander ball tilted the case in the shell holder enough to pull the case neck off several thousandths. Had my die neck machined to fit my rifle so that no expander needed and that solved my runout problem.

IMHO runout doesn't cause many problems @ 100 yds, however; the longer the range, the more runout affects accuracy.

I was having similar problems w/my 375 and found the fliers were caused by not getting exactly same eye relief on the scope each shot. Amazing how much difference a slight variation in how firmly the rifle is held, cheek pressure, etc. can make on the larger calibers. (Of course my progressive bifocals make eye position even more critical from shot to shot.)

Regards,
hm

As the other guys have stated, you can measure runout on either the case (neck) or on the bullet (I usually measure around the point on the ogive, where the bullet will first meet the lands). Whether you do one or the other, depends on what you want to establish. If you want to see whether your sizing process produces straight cases, you measure the case. If you want to assess your end-product, and figure out whether both sizing and seating operations are up to scratch, you measure on the seated bullet.

0.007" of runout is a fair amount. Even though this may not be the cause of your occasional flyers, it would be interesting to figure out what in your reloading process brings you up as high as this. The first culprit considered is normally your sizing die with an expander. But there are other potential offenders - I know some of my seating processes have introduced runout, though not as much as .007. You really have to measure the outcome of each stage to get an idea where the gremlin might lie.

Brass that is thicker on one side (measured on neck, assumed to be the same down the case), is certainly one potential culprit for your flyer problem. Have you established this with a case neck gauge of some sort?? And have you sorted your cases accordingly, and still get the flyers with brass with low variation in case neck wall thickness??

You can turn your brass to obtain consistent necks, if it was me shooting a .375 H&H in a factory chamber, I would probably not start out with techniques usually deployed in BR to reduce group sizes maybe 0.1 or 0.2". But hey, we all choose different paths. If you do decide to turn your necks, you really have to make sure you turn them minimally, otherwise you'll just end up working the thinner brass a bunch more between your (likely) ample chamber neck size and what the your die sizes them down to. Overworking your brass can't be a positive step in your quest.

When you seat your bullets, do you get the feeling of consistent resistance from bullet to bullet??
- mike

To expand on what LB404 was saying, we were using a Sinclair runout tool. If the front rollers and the indicator were on the bullet we had runout of .001 but if we put the rollers on the case and the indicator on the bullet the runout would read as high as .007 on the same bullet.
We have tried at least 4 sets of dies, including Redding, Hornady, Lee and Forster. And have tried 2 different "Benchrest" quality seaters including a Forster and a Z-Hat custom seater.
I'm thinking the WW brass is goofy. Neck thickness varies from .009 to .012 on individual cases.
By measuring runout with the rollers and indicator on the bullet, I think it's showing that the seater is seating square with the base of the bullet but that the brass is too lopsided to show the same when the rollers are on the brass. Does this make sense or am I thinking wrong here?

The other thing about worrying so much about 375 accuracy is that LB404 is shooting one of the nicest custom 375's that you've ever seen and it is capable of 1/4minute accuracy when we get the ammo right - I've shot 1/4" groups at 100 with it, but for whatever reason it's not shooting that good now..................DJ

Here's what you do:

Turn the necks, then FL size without the expander ball. Measure neck runout. It should be .001" or less.

FL size again with the expander ball, then measure neck runout again. If it is more than .001" then you have identified part of the problem. If not, then your seater is causing the runout.

Ralph, We did as you suggest. When you size it without the expander ball it's good because the last thing to touch the outside was the sizer die. With the expander ball going back through and we get too much runout youi either have a funky expander ball or brass with varying neck thicknesses...........DJ

quote:

Originally posted by djpaintles:
Ralph, We did as you suggest. When you size it without the expander ball it's good because the last thing to touch the outside was the sizer die. With the expander ball going back through and we get too much runout youi either have a funky expander ball or brass with varying neck thicknesses...........DJ

In addition to polishing the expander ball and lubricating inside of case neck, you may try to adjust the expander ball as high as possible in the die, being careful that it is below the neck sizing portion of die. This allows the expander to enter the case neck while still being centered by the neck of case in die as it is withdrawn from the die.

I usually place a thin rubber o-ring under the expander stem lock nut and tighten the nut only finger tight. This lets the stem move very slightly to center in case.

Regards,
hm

quote:

Originally posted by hm1996:
you may try to adjust the expander ball as high as possible in the die, being careful that it is below the neck sizing portion of die. This allows the expander to enter the case neck while still being centered by the neck of case in die as it is withdrawn from the die.

I hadn't thought of that yet. Great idea thanks.......DJ

I don't much like dies with an expander, for the reasons indicated above. But if you have to have one, it is better placed high in the die, as opposed to the usual just at the mouth of the die. This is one advantage of the Forster FL dies, their expanders are way up into the die. All the better, if you can make the expander "float" by using a an o-ring either on the die itself or just on the expander, as hm1996 mentioned above.

Better still, avoid the darn expander all together. Use a Lee Collet Die with a Redding Body Die, if you can get them for the cartridges you want to reload.

Sadly, the .375H&H is kind of hard to find Redding Body Dies for. As an alternative, consider that both Hornady and Forster will alter one of their FL sizing dies to size down to a specified loaded neck diameter. The charge is very reasonable, 10-20$ if memory serves. That will allow you to get rid of the expander, but may work best if you sort for case neck thickness, or turn your necks.
- mike

Just an inch out with a large caliber is still pretty good shooting but I know you want perfection.

One can argue with ease that any variable might throw things off. It's sort of garbage in if your finding necks with different wall measurements. Make sure that your measuring the necks right and not measuring a burr in the case mouth etc.

I would just buy some other brands of brass and sort thru them. You can also FL size with a smaller expanding button from a .300 die and decap that way or polish the expanding button down some as its easy to do.

Make sure the chamfer is good on the inside of the case mouth when the necks are smaller like that. I prefer a 14 degree angle. Keep in mind that FL sizing and neck sizing do not really make cases better but just smaller. Try to do as little "work" to the brass as necessary and lube the insides of the necks good and in a uniform way if the button touches.

Another thing to do is to throw out cases that make bad shots and even cases that show a variable button drag when pulling the expanding button out.

Again thats still good shooting. Even a crow would not be safe at 200 yds.

Measure the runout of the bullet, not the case neck.

Case neck runout will show differences in neck wall thickness.

When you find a case with one side much thicker than the other, measure runout with and without the expander assembly. The same brass will show less runout with the expander removed. This is because you are measuring only the outside of the case. The bullet will do what the expander ( the one you removed ) was originally doing, it will move this variation in brass thickness to the outside of the neck where it will be measurable ( again ).

It's all abot the hole in the middle, not the outside of the case neck.

Crooked bullet = bad
Case neck walls not perfect = normal ( in the real world )

Measure the bullets runout, it's what really matters.


Travis F.