Heat and sabots in a traditional fast twist

cayugad · 06-12-2011, 06:35 PM

A strange day today. But I had to shoot so I got at it finally and shot a lot in a short time. This morning was 35ºs out (thank goodness the gardens did not frost over) and by this afternoon it was 72º and sunny. It might have been even warmer but none of the thermometers had the same reading.

I decided to shoot a traditional rifle, but I wanted to see the effect of heating the barrel up while shooting to see if sabots reacted strange. Well they sure did.

Rifle: Thompson Center Black Mountain Magnum 1-28 twist barrel.
Scope: Simmons 4x32mm Pro Diamond
Distance: 50 yards
Powder: Pyrodex P & Goex 2f
Sabots: Nosler .452 black sabots (believe they are MMP HPH-24) and Traditions Black .430 sabots
Projectiles: Buffalo Bullet 325, .430 240 gr XTP, 460 gr No Excuses conical
Ignition System: Musket Caps

I started out shooting No Excuses Conicals as fast as I could shoot and load. This rifle did not like conical bullets. Perhaps it is the OLA the barrel has or I have not found the right powder charge, but there was some real problems for only 50 yards.

I then swabbed the barrel clean with simple green. I let it cool down and got the Buffalo Bullet 325 grain SSB hollow points out. I decided to shoot Pyrodex P in the 85 grain range. And I wanted to shoot as fast as I could. So I shot three then swabbed, shot three, then swabbed. The barrel got really hot, but the group was not all that bad. This is the first time I tried these bullets in this rifle and I think with some powder work they could be a real good load.

I then swabbed the barrel clean and took some of the .430 diameter 240 grain XTPs in a Traditions 44 caliber sabot. The barrel was really hot now, and the hits started to react. Whether it was the heat of the barrel or the bullet I can not say, but they just started to walk upward on the target.

I then let the barrel cool (these hits are not show) and changed out targets. I let the barrel cool between shots and as it cool I heated up fighting off the deer flies. But the difference in the groups were very noticeable. Much tighter groups. The camera decided it wanted to die, so I never did get pictures of that target.

lemoyne · 06-13-2011, 05:50 AM

Dave, because it is much warmer where I live the problem of heat walking and soften sabots is much greater, I some times have to wait 5 or 6 minutes between shots.
I have done some experimenting to see what would help the situation and so far using 3 or 4 guns so that the first shot has enough time to cool before shooting it again. The other thing is that the Harvester sabots seem to withstand a higher temperature than the MMP. When you want to shoot where the temperature is close to 100 this time of year [it is supposed to get to 98 today] this is a ongoing problem I wish some one would make some heat resistant sabots like maybe out of Teflon. If you find any good solutions please post them.

cayugad · 06-13-2011, 08:35 AM

I was surprised just how hot the barrel got yesterday. I mean 70 is a long stretch from your temperatures. I have no idea how to combat heat related accuracy. I refuse not to shoot, so I guess all I can do is not take the groups all that serious until it starts to cool down again.

I have also done the three rifle shooting day. Makes for a long day on the range.

bronko22000 · 06-13-2011, 02:29 PM

I know the heat really affects my little .32 cal Cherokee. Even with only 20 - 30 gr of powder. It will start out shooting really nice little groups and then all of a sudden the entire group moves and opens up. Almost as if someone adjusted the sights. I'll let it cool for about 20 mins and its back to shooting fine. And this is with PRBs.