I have been loading for over 30 years. Not a novice. Ran into a problem with loading my 375H&H. I have 3 of my own and load for 6 others. a couple of years ago I settled upon a load that worked extremely well in ALL of the above mentioned rifles. That load is Varget 73gr/WW cases/F215M/260 girandole Partition/3.585OAL/2750 f-s. All shoot and extract well. Cases last a long time-I am on my 7-8th reload on the cases. Then along comes my new custom rifle-the one with integral barrel furniture and custom stocked in fine walnut. I load up 20 rounds for this rifle and off to the range I go. Clean fresh bore. First shot gives sticky bolt lift and primers look like the ones shot in the other 375"s flat but not extruded. Slight possible smudging of the case head. Two more produced essentially the same results. Went home and down loaded the round to test for pressure. Loaded 3 each at 70 gr to 73.0 in half gr. increments. 71gr. seems to be good but not as accurate as 72gr. still some pressure signs.

QUESTION
1- Is this a tight chamber and tighter than factory barrel tolerances-Douglas barrel?
2-is this a overload?
3- the throat is more than long enough so no bullet jam problems
4- called Hogdon and talked to the ballistition who said that the load was above the 50,000CUP they recommend (Varget recommended 66-68 gr.)
5-Two loading manuals give a max for varget and a 250gr at 73gr.(Swift/Barnes)
6-Quick load says that this load should yield around 60,000 psi.
7-what is the relationship between CUP and PSI relative to reloading. Many manuals use both systems but not the same system for all of the loads in the same manual
Going to Africa soon would like toi take this rifle and shoot the same ammo that my partners are taking.

Hummm....

I found the useful range for the .375 H&H with bullets between 260 and 270 grains to be:
Varget From 61.1 grains to 75.1 grains
Remington 9-1/2M Primer

So, your load should be no problem.

There is no relationship whatsoever between CUP and PSI. I have seen several posts where people have claimed there is a formula they have devised, but in all honesty, their formulae are totally incorrect.

I have a table on my pages ( http://stevespages.com/crusher.html ) which lists the CUP and PSI for some of the more common cartridges.

I would say that your chamber is a tight chamber or if you did not used full-sized brass or once fired brass from that rifle, you cases may not match the dimensions of your chamber.

Case dimensions can be found at http://stevespages.com/cd375hollandandhollandmagnum.jpg

So if I use new full length sized brass for the rifle will it show pressure signs before it would with full length once fired brass?

Agree there is no relationship between CUP and PSI.

I'm uncertain exactly what you are defining as "pressure" signs. Sticky bolt lift? Could be nothing to do with the load but a mechanical function of a new gun. Primers are the poorest indicator of pressure signs simply because of the difference in cup material, firing pin protrusion, large firing pin hole in bolt face, etc. The one thing that would truly concern me is the powder residue on the case head. Accounting for that is difficult. Only two things would account for that, a mechanical problem in the chamber allowing the spent gases to bleed back toward the bolt face and that would scare the hell out of me, or the other possibility is insufficient expansion of the brass, establishing no seal and allowing the gas to escape. All bad and dangerous possibilities.

Chronographing the load and measuring velocity would tell you whether your load is within published maximums and be some indicator of whether or not you have high pressure. Pressure=velocity.

You may also have differences in bore sizes. It's amazing the differences in bore sizes in barrels, particularly between a custom and a factory barrel. I've see as much as .0007" difference in groove diameter, but about .0004" is not unusual between factory and custom. That will also affect pressures.

A chamber significantly tighter than normal WILL end up giving higher pressure. In a similar situation with a couple of 338 Win Mags, the difference was about 1g between the tight and sloppy chamber. You might try reducing your load at least to the max Hodgdon recommendations and seeing if you have the same results. If you don't, then you may have pressure problems. If you do have similar signs, you have a mechanical problem. Chronographing will tell you a lot. Good luck.

Bob338, the smudging on the case head I was refering to was brass smearing not soot. The reduced loads did in fact appear to be less problimatic but still had the bolt lift idiosyncracy. Will try again and chrono all the loads.
Thanks

LB404-Does the factory or reloaded brass chamber
hard.Might be a rough chamber if it does.Also check lug seats with marker on back of lugs, to see if both are bearing even or if lug seats are smooth.If factory brass chambers real easy, perhaps headspace is long, and you need to use reloads sized short of the shell holder, to get length.Too much headspace will cause case to slam back on firing giving brass smudge.Ed.

The abrasion of the brass would likely be the reason for the "stickiness" you feel on bolt lift. That's what's turning when you extract. If the chamber is also rough and the brass does NOT rotate, which is normal, the bolt is obviously binding on the brass and creating the stickiness you feel. Likely it will disappear when the bolt face smooths out.

The bottom line is that the load of 73 grs seems too hot.

Can you get a bullet into a fired neck by hand?

I have experienced sticky bolt lift that was not due to pressure excesses in 2 rifles due to 2 different reasons:-

First Rifle - 6.5x55 on Argentine 09. Sticky bolt lift on all but minimum loads due to the bolt face not being opened up the 10thou or so that the 6.5x55 is wider in the rim by. The bolt face was scudging over the rim. Opening up the bolt face allowed normal loads to extract perfectly.

Second rifle - Chamber cut to guage ie min SAAMI spec. Rifle does not like RWS brass as it has greater length (ie less headspace) and the bases smear as you describe.

I would check the bolt face and the dimensions of full length sized cases vs your chamber. With a custom chamber it may be that your die is not sizing enough even when fully adjusted.

It would help to chronograph the loads from both rifles to give a clue as to what is going on.

Sticky bolt lift, as others have noted, can occur without excessive pressures, due to imperfections in the bolt face or lugs. Assuming it to be a new action, try lapping judiciously with some compound to see if it smooths up.