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Yesterday (Sunday) I finally got all the pieces of equipment assembled to begin rational, controlled test-shooting and ammunition development.
Bob's the Builder's standing rest is exactly what I wanted and needed: the height, slant and rigidity are excellent. The legs are of 3/4" pipe, threaded into flanges bolted to the bottom of the table, and angled outward for stability; the whole can be assembled or disassembled in a minute. Three 25 lb. bags of shot serve for the front hand rest, and add further stability to the assembly, while a piece of carpet over the top cushions the elbow. Bob wouldn't take any money for the work (except the materials - $50), though he did ask where he could get a pair of Gila monsters (presumably for his Ark) - I told him where I had seen several recently, but had to decline helping him with the roundup (which is somewhat illegal) - and I am completely ignorant of (and completely uninterested in) how one goes about sexing Gila monsters (the critters apparently CAN figure it out amongst themselves) - I'll have to do something else nice for Bob to return the favor.
The resurrected Oehler chronograph is working perfectly again, and I was able to obtain measurements on all shots fired.
As I had already shot this load (109 grs. IMR 4831 surplus, 570 gr. Woodleigh SP, WLRM primer in Rigby HS brass), I shot only three pairs to obtain velocity and check regulation and POI. Results were: high velocity 1943 fps, low velocity 1888 fps, average velocity 1927 fps, extreme spread 55 fps, SD 20.
The standing rest also proved its worth in consistent POI: all shots were nicely clustered about the POA (average 1" high) with an average spread between rights and lefts of about 1 1/2", rights to the right and lefts to the left of CL, but with enough horizontal consistency to make me believe that I may want to make a minor adjustment in the rear sight windage, as shooting progresses.
Some comments are appropriate here: first, the velocity spread (and there was only a single shot recorded below 1923 fps) is probably due to inconsistent crimp: I noticed when I got the brass that it is not all the same length, (which is why I want to have the means to trim it) and this makes for problems in crimping the case mouth, which I am certain is quite necessary for consistent ballistics with compressed loads in straight cases - the .458 is certainly a good example. Secondly, the brass (which I believe is actually by Bertram) has a noticeable 'ridge' inside the case mouth, which would be removed by trimming and/or deburring - this is also undesireable, and I knew it was there when I first loaded the cases - my only excuse is lack of means to trim the brass, and the desire to start shooting the rifle without delay. Mea culpa. But I WILL resolve the issues with the brass.
The next steps (after homogenizing the brass) will be load development to achieve full ballistics and consistent regulation - later, cast bullets and paper-patched. I'll likely have to try another batch of IMR 4831 - which I have - (versus the WW2 stuff I first used), and other powders as appropriate. I'd like to stay with compressed loads of suitable powders, but may have to branch-out to something else. I'd be happy to have any information your experience can provide.
Much more to do - will report.
mhb - Mike

P.S./ Afterthought: I almost forgot a very significant thing - my thumb and my dignity got through this session without further damage. :-/

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Sancho! My armor!

Edited by mhb (25/10/05 02:21 AM)