PP bore or groove diameter?

[martinibelgian]

While I got some pretty amazing accuracy with the bore-diameter PP bullets, there was the questions on how it compares with grove-diameter PP. Which is why I gave the groove-dia. variety a 1st try (in the rebarreled rifle, I might add, which up to now only saw bore-dia. PP bullets.) last weekend.
Of course, you're giving up powder space - but this isn't necessarily a bad thing with the no.2 Musket cartridge, also known as 500/450 no.2.
Whereas my standard go-to load consists of 2 drops at the 9.6 setting of my RCBS uniflow, the load for the groove-dia. bullet was FG, 2 drops at the 8.7 setting, with the bullet occupiyng most of the case neck. This is about 83 grs of Swiss fg.
I had a 1st try last WE at 300m - as usual, all shooting prone, with sling, unsupported. Quite a bit of mirage, which made it impossible to see impacts on the target with the spotting scope.
Still, While POI was quite a bit off when compared to the go-to load, it pproduced a nice, round group with very pleasing vertical - not taking into account some 'nut-behind'-errors. Accuracy was at least equal to the bore-dia. variety.
I do have to say this was with very tight, min-spec fireformed cases in order to optimize bullet-to-bore alignment. The case prep is retty extensive and time-consuming, but on the other hnd you have the option to either turn the necks to the right diameter for groove-dia. bullets, or leave them as is for bore-dia. Just don't mix the 2 varieties...

[beltfed]

Martinibelgium,
Read the thread in Shooter to Shooter re.
PP bullets in competition.
DT has a good discourse on what we have been doing in Two Diameter PP bullets,
Just now particularly for our 40-65 rifles that have freebore chambers- Bob Wood's
Brg BPCR, my custom Orig Hi Wall, and DT's long freebore 40-65.
As Jim pointed out, one needs to design for the particular chamber unless you want to
rebarrel, etc to a dedicated PP chamber for straight bore size bullets.
Bob and I have been shooting the first one Jim cut I spec'd/ designed for Bob and my rifles.
and now one for his own particular chamber as he described.
Having very good accuracy , even out to long range in our 16 twist rifles.
You might want to look at this concept.
Bruce Moulds , an Aussie has also worked with two diameter bullets successfully.
beltfed/arnie

[bruce m]

well arnie i thought i was a pioneer, that is until i discovered you were ahead of me.
a few of us have now gone this route independantly and come up with the same answer.
keep safe,
bruce.

[BFD]

the Modern re-emergence of groove diameter paper patching was pioneered back in the 1980s and 90s. It is was not new then, just rediscovered.

[beltfed]

Brent, you are correct. nothing new in Groove Dia PP bullets in the modern era.
Actually,
The/a Modern Emergence of groove diameter PP bullets was back in the 1960s.
I followed Col. Harrison's (of NRA) development of groove dia pp bullets for 30-06, 308, and even the 300Win Mag for target shooting.
Got my first mold for that in late '60s- the Lyman 301618, a 160 gr PP bullet. Patched it with
Crane 100% rag bond paper, and shot it thru my '03 Springfield M1941 Sniper rifle over full loads of smokeless powder to 2700fps.
I also developed groove dia PP bullets for my 358 Win deer rifle- 250 gr RN at 2350fps, and even my 375 HH Imp -265 PP at 2700fps
for hunting.
And, of course nowadays "re-development" in BPCR.
beltfed/arnie

[martinibelgian]

Arnie,

The nice thing with my chamber is that I have both - a bore-dia. PP chamber requiring no neck sizing, and a groove dia. PP chamber when I turn the case necks. Not possible with the 45-70/90/100/110 cases, but no problem with the no.2 Musket, using .470 NE as basic brass. Lots of work, but the best of both worlds...

[martinibelgian]

Just got home from a match in Alsfeld, Germany where I shot both varieties. There actually were 2 300m matches this weekend, both 300 meters.So I shot the bore-diameter PP ammo in the 1st match, and the groove diameter PP ammo in the 2nd . Both loads were shot in the same rifle, A Martini chambered in the Brit no.2 Musket cartridge, with a gaintwist 9-groove barrel, final twist 1 in 16.
Ammo details below:

Bore-dia. PP cartridge
Converted federal .470 NE brass - fireformed case mouth diameter is at .451.
.443 BACO money bullet patched up to .451, 540 grains, 1:16 alloy
2 drops at the 9.6 setting of the Uniflow Powder measure of Swiss 1 1/2Fg - about 87grs.
Thick card overpowder wad
CCI BR2 primer

Groove-dia. PP bullet
Converted Kynamco 500/416 brass, neckturned for a snug fit with a .458 bullet.
.451 Mike Neumann Metford copy bullet patched up to .458, 540 grains, 1:16 alloy. Bullet is 1.5" long
2 drops at the 8.7 setting of the Uniflow Powder measure of Swiss Fg - about 83grs (the Fg being quite abit heavier for the same volume than the Fg).
'Normal' card overpowder wad
CCI BR2 primer

According to the competition rules, all shooting from the prone position, no support, but with (2-point) sling allowed - no shooting sticks though. The 1st match where I shot the bore-diameter bullet was 20 shots, the next day's match with the groove diameter variety was 15 shots.

Results? There will be of course the 'nut-behind' variable in the equation, but I was only able to put 2 shots in the 10-ring with the bore-diameter bullet (out of 20) with lots of 9's, whereas I got 7 out of 15 in with the groove-diameter bullet. For reference purposes, the 10-ring on the 300m ISSF target we use would be 10cm or 3.94 inches - so just a bit more than MOA. The 9-ring is double that (20cm or 7.87 inches).

Is this a final judgment? By no means, I do believe my shooting was better the 2nd day - But I do have the impression that the groove-dia. bullet tended to perform better than the bore-dia. variety at this same range.
The Alsfeld 300m range is pretty good for accuracy testing in that it is walled (no roof though), so the influence of wind is pretty small - which makes these matches a pretty good test of shooter and load, wind being the factor of lesser importance in this case.

But most importantly, 2 very good BP matches in Germany, they have awesome range facilities - a real shooting complex. Wish we had something similar here in Belgium...

[bruce m]

good report gert.
it will be interesting to follow your journey.
i do recall montana charley writing an ongoing report about shooting groove diameter pp bullets that went on for some years.
might have been on cast boolits.
keep safe,
bruce.

[beltfed]

Of course, Enter the two diameter PP bullets:
patch body to bore and a base band to groove/neck I.D, diameter
Several of us are having good success with them.
And, Bruce you have worked with them too.
beltfed/arnie

[bruce m]

yes arnie.
the beauty of them is you can design a bullet for any chamber, including freebore chambers.
with big greaser chambers, they are pre bumped up to what they would do anyway when they are fired.
this minimizes 1 lot of lead movement, as well as allowing finger seating of bullets in fired cases and no sizing.
does gert's chamber have freebore?
i found montana charley's thread on cast boolits.
it follows his journey over quite a long time.
it is called paper patching my way if you want to search. many pages.
interesting the nay sayers thet joined in.
keep safe,
bruce.

[Ray Newman]

Brucem: could you post a link to MT Charlie's thread?

[bruce m]

ray,
try this.

castboolits.gunloads.com/showthread.php?42529-Paper-Patching-my-way/page2

2 things,
read the whole lot, as the journey matters.
also charlies dialogue with kurt is like any time kurt speaks - well worth taking note of.
and he is always civil.
keep safe,
bruce.

[bruce m]

http://www.castboolits.gunloads.com/sho ... ing-my-way

[martinibelgian]

Bruce, to answer your question - no, no freebore in my no.2 Musket chamber. And no sizing either, brass for groove-dia. Bullets is neckturned for the. .458 to fit, brass for bore dia. Bullets not, the .451 bullet is a perfect fit in normal fireformed brass. So not really a need for 2-diameter bullets, unless I want to use the groove dia cases.

[Ray Newman]

Bruce: thanks for the link.