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I knew up front the Palma 95 chamber was tighter and shorter freebore than standard, but I am surprised to find it this short.
With a SMK 168 I am in the lands at 2.785" OAL, and with Lapua Scenar 155's in the lands at 2.800".
Does this sound right? Doesn't this preclude the use of commercial rounds like Federal GMM?
Any help greatly appreciated.
Jeff
Palma chambers were never intended for FGMM. They are intended for 155gr bullets that tend to have short bearing surfaces and short seating depths; typical WTC95 Palma reamers (basically what they used) have almost no freebore.
Thanks for your response.
Could you and/or others then share or direct me to some loading data? Few powders seem to qualify without significant compression. I have read here before purchase that folks are sending 175 SMKs from their Palmas, but you sure can't get much Varget, a favorite among .308ers into the case then. Most standard .308 recipes don't seem to work well.
And the Lapua Scenar 155s I have also seem to be a bad choice because of the seating depth requirements.
Thanks again.
Jeff
I haven't fooled much with 175 bullets of any flavor in a Palma chamber in any gun. I may have to remedy that, as the question seems to come up regularly. There are a number of special .308 'match' reamers floating around out there, more than a few of which are basically either an Obermeyer (what the 12 F/TR uses) or a 95 Palma reamer, throated slightly longer to accept a S175MK seated to make more use of the available magazine length (generally 2.810-2.820"). As such... trying to stuff a S175MK in a *regular* 95 Palma chamber may not be the best route, and I'd seriously have to wonder if a Berger 175gn VLD would be much better off. However... Berger does make a 175gn LR BT bullet - basically a 'big brother' to the 155.5 gn LR BT 'Fullbore' bullet. I've fondled/measured some of the B185LRBT and B210LRBT bullets, and they have fairly short bearing surface sections compared to older designs from other makers - just like the B155.5BT (and admittedly the newer S155MK Palma bullet aka '2156'). Being closely related and all that, I'd bet the B175LRBT probably has a shorter bearing surface than a S175MK... so you might get luck in that it doesn't take up as much case capacity when seated into or near the lands.
From previous experience with S175MK bullet in *other* barrels and chambers, about 2.800-2.810", either 43.8gn RE-15 or 44 gn Varget in a Winchester case seemed to work really well.
As mentioned, both the new B155.5BT 'Fullbore' and the new S155MK 'Palma' bullets are longer (like the Lapua Scenar) and have a much shorter bearing surface than previous models. As such, you can easily seat them out far enough to get enough powder behind them to make rated speed.
The downside is... the 1-13" twist is/was more ideal for the traditional (old) S155MK and its clone, the Nosler 155 Custom Competition bullet, and the old B155BT & VLDs. The much longer Lapua 154gn Scenar and the new Berger/Sierra bullets are probably more ideally suited to a 1-12" twist, and wouldn't be out of place in a 11 twist. Note there is a difference between 'not ideal' and "won't work at all". I've used B155.5BTs over 46.8gn N150, about 45 thou off the lands, in both my 12 F/TR and in my 12 Palma. Accuracy in the 12 F/TR could be described as 'surgical', while the 12 Palma wasn't exactly slacking off - though I was less concerned about it as I use that particular rifle as an iron-sight gun.
YMMV,
Monte
Excellent and helpful info, Monte. Thanks.
So the dimensions I listed, in the lands at 2.800" for the 155 Scenars and 2.785" for the SMK 168s aren't out of the ordinary for the Palma chamber?
Seems I have to change my thinking on powders. I'm an IMR fan, but it seems they are not going to work for me with this gun.
Thanks again.
Jeff
Some folks were playing with IMR 4895 and the Lapua Scenar... for some reason 45.6 in a Lapua case, maybe 46.5 in a Winchester case, rings a bell. They were getting some pretty good velocities and acceptable accuracy. Might want to back down at least a grain in light of the short throat, especially if you haven't played with one before. The first one I had on a 30" custom 40X Palma rifle, combined with some Winchester Palma cases (heavier than normal Winchester cases, but not quite as much as Lapua), had me running a mere 45.2gr of Varget (as opposed to over 47gr in a loose SAAMI chamber and throat on a 700VS 26" barrel). I have an 8# jug of IMR 4895 I started using, and then sold that rifle. Haven't got a load developed to use it and the 2000 odd S155MK 2156 bullets I have sitting around used up... ;)