1897 Remington RB #5 7x57 Keyholing

[shafer44]

I have an 1897 Remington RB #5 in 7mm SM. I have slugged the barrel and it is .2864 diameter. One of the guys here on CB sent me some tumble lubed 170gr. gas checked boolits sized .290. I was getting keyholes from some, but not all of the j-word bullets that I shot thru it. Well, I loaded up some of these cast boolits and to keep pressure down, I used 27gr of IMR 3031 for about 2000 fps and pressure below 15000. I just shot at 50 yards and they kind of grouped, but I have not done anything to the trigger yet and it is about 7lbs, so that makes it pretty hard to shoot consistently. The problem still is that 3 or 4 of the 10 shots I fired still keyholed. The others were perfectly round holes. The barrel rifling still looks good, I don't see any pitting in the bore, the boolits are over groove diameter, they were tumble lubed and gas checked, I cannot figure out why it keyholes. I would appreciate some opinions on what I should try next. Should I bump up the velocity? Most info i have researched says 40K for pressure or below.....I am not even near 20k yet. I don't have a mold or sizing die yet, I wanted to try before buying both. I could also switch powders to use one that has more pressure at lower velocities.

[shafer44]

oh, and I tested the boolits with my Cabin Tree and they are really hard at 22 or linotype hardness.

[Geezer in NH]

I would go softer and bigger IMHO

[Reverend Al]

I bought a South American 7x57 RB a short while ago and haven't shot it much yet, but the PO gave me his load of 34.0 of IMR4064 with a 165 to 175 grain bullet. Although I'm sure I have a pound of 4064 somewhere I just couldn't find and so I tried 34.0 of 3031 instead with some old Winchester 175 grain semi-spitzers. I shot a 5 round test group with them and the first round went right to point of aim and the next 4 went about 2" right of point of aim into a nice 1 1/2" cluster. Mild recoil and seems to be low pressures looking at the fired cases. Mine is a typical well used and worn and torn example of a South American 7x57 roller with a fair bore so I am more than happy with it's performance so far. Now I need to find a suitable 175 grain 7mm mould to try some boolits in it ...

[marlinman93]

I wouldn't go larger, as the size seems perfect to me. I'd go lighter though, as the 7mm Roller with cast bullet can't be pushed fast enough with cast to give it the same spin the original jacketed bullets did. I'd find some 140-150 gr. cast bullets, and try them with a velocity of around 1400 fps. If you found a little lighter then the 140 gr., I would try those also, and see how they worked.