Project for 2017 - BP short range target rifle

Here we post the results from any disciplined, scientific testing (primers, wads, bullets, lubes, powders and compression, etc.) along with any and all peer responses and criticisms. "Question everything!" "

ModeratorCOLON Rob Dorsey

martinibelgian
PostsCOLON 453
JoinedCOLON Sat Nov 26, 2005 5:31 am
LocationCOLON Belgium

Project for 2017 - BP short range target rifle

Post by martinibelgian » Tue Jan 03, 2017 11:40 am

Here in Europe, most BP target rifle matches are 100 to 300m, which makes the big .40 and .45 rounds a bit overkill - after all, it not as if you need that much bullet and powder to get to 300 max. Hence my ost recent project, for which the experimenting already started last year:
Image
Basically, a small-action Martini (f course!) rifle chambered for a period-correct round in order to see whether this little cartridge can deliver the goods out to 300 without giving up any significant accuracy at the longer ranges. Which is why the above rifle is a test mule:
.308 1:15 twist barrel, BSA 12/15 action converted to CF, and with - for now - the standard Parker-Hale front and rear sights.
Mind you, not a typical 32-20 - for starters, the faster-twist barrel allows the use of a heavier bullet - in the pic, a 150 PP bullet patched to groove diameter. I also have a GG bullet, and a 169gr Pope 308403 bullet which is pretty much a breech-seating proposition. It might also be a bit long for the rifling twist, even if accuracy at 75 nd 100m is very good.
Powder charge is somewhere between 16.7 and 18 grs of swiss 1 1/2Fg, for what is essentially a subsonic bullet. This one is wiped between shots, both for GG and PP.
The group shot above was actually the 1st try after firelapping what was essentially a trashed barrel, and shot at 75m (82yds for you guys). The lowest shot was actually the flier, the top 4 shots were shot in sequence. As usual, all shooting, prone, with sling, no artificial support. Already shot a few shots last year at 200 with promising results, even if these are the 1st and only shots fired at 200 (the lower right one being the 1st shot one paper, after which the sight was duly adjusted for the next 4 shots):
Image
Now for some 300m experimenting.... Although I'm not sure the sight will allow me to reach out that far: that might require something different than the PH7A.
But to summarize - the accuracy potential does seem to be there, and as is to be expected, recoil is pretty negligible - even in such a light, petite rifle. The big question is - how will she perform at 300?

gunlaker
PostsCOLON 375
JoinedCOLON Sat Aug 09, 2008 1:46 pm
LocationCOLON British Columbia

Re: Project for 2017 - BP short range target rifle

Post by gunlaker » Tue Jan 03, 2017 3:11 pm

I'll be interested to hear how well it works. I have a .32-40 that I plan on trying at 300 this year. Not for competition, but for practice and fun in general.

Chris.

Brent
PostsCOLON 1567
JoinedCOLON Sun Nov 20, 2005 9:12 pm
LocationCOLON the most boring real estate west of Illinois

Re: Project for 2017 - BP short range target rifle

Post by Brent » Tue Jan 03, 2017 3:22 pm

I can't say I know how it will perform, but I wonder if the vertical will become more accentuated. That would be my prediction, but only time can trial and error can say.
I'm not from here, I just live here.

martinibelgian
PostsCOLON 453
JoinedCOLON Sat Nov 26, 2005 5:31 am
LocationCOLON Belgium

Re: Project for 2017 - BP short range target rifle

Post by martinibelgian » Tue Jan 03, 2017 3:45 pm

I still have to do some chrono work with the cartridge, but initial results seemed pretty promising with an ES of around 10fps. And I was actually pretty surprised at the come-up between 100 and 200 (meters, that is): 17.5 minutes with an average MV of 1063fps, which does indicate a pretty decent BC.

Still, 300 will be a long way for this tiny round to be competitive, and the challenge will be in keeping the ES to an absolute minimum in order to reduce vertical, I agree. But if I can keep it below 3 MOA, I'd probably not give up anything competitively to the larger calibres, the ease of shooting it offsetting the fact that it might be running out of steam at 300.
Here I'm hoping that the fact that it's subsonic might also have a beneficial effect on wind drift. Time will tell... But the intention is to use it competitively at the 100m matches (where it will definitely have an advantage), and see if I can develop a load good enough for 300m use.
If I can shoot at 200 like the target posted (if you disregard that 1st sighter), I know I won't have any issues whatsoever in getting competitive 200m accuracy.

Brent
PostsCOLON 1567
JoinedCOLON Sun Nov 20, 2005 9:12 pm
LocationCOLON the most boring real estate west of Illinois

Re: Project for 2017 - BP short range target rifle

Post by Brent » Tue Jan 03, 2017 3:51 pm

Gert,more than the ES of the muzzle velocity (or SD for that matter), I think bullet stability and lack thereof will have more to do with vertical spread on the target.

Get some good clean, thick target backers and inspect bullet holes very carefully. That slow twist may do it, but it will be on the edge I think and occasional unstable shots will drop. You might make up some faster velocity smokeless rounds for comparisons. Likely, they will have larger ES/SDs, but less vertical. Maybe. Lots of guessing, but it will be interesting to see what you find.

Brent
I'm not from here, I just live here.

martinibelgian
PostsCOLON 453
JoinedCOLON Sat Nov 26, 2005 5:31 am
LocationCOLON Belgium

Re: Project for 2017 - BP short range target rifle

Post by martinibelgian » Tue Jan 03, 2017 4:11 pm

Brent,
I'm not really concerned as to the stability of the 150gr bullet - at .9 inches long, stability should be sufficient - even with a modest 1061fps. Both the Kolbe and the JBM calculator do predict good stability for this bullet. The 169 gr Pope bullet OTOH will probably develop issues at the longer ranges, which is to be expected. Which is why a 1:12 twist barrel is in the works :) .

BUTTON_POST_REPLY

Who is online

Users browsing this forum: 2 and 0 guests