4227 in 45/70 question?

bswiv · June 10, 2007, 04:02 PM

Had a 45/70 at the range today using some 300 grain reloads in front of 29, 31 and 33 gr of 4227. Loads came from the Hornady #4. Trapdoor pressures.

Cases were about 1/2 full. Used a measure that was checked against two scales and then a load or two checked during the process.

On the chronograph they were very inconsistent. As much as 200 fps different.

This was in a O/U rifle. In every instance the top barrel, which was firing second, produced higher pressures.

Wondering if this could be caused by the partially empty case setteling the powder between shots from the recoil.....or something we totally missed?

We know we're going to have to make another trip with the chronograph to see what is happening but we'd like some input as to what to look for or do to find out what is going on here.

Trapper L · June 10, 2007, 04:15 PM

I'm not sure the question but if your expectations that both barrels were going to shoot the same- you would be wrong. No two barrels will shoot the same or have the same pressure. Minute differences in machining will make each different. Chamber dimensions may not be perfectly the same, the bore may be slick in one and a little rough in the other. That's why one load doesn't always shoot in every gun. You are going to have to treat each barrel just like it was a different rifle. And if it was easy- anybody could do it.

bswiv · June 10, 2007, 04:23 PM

That was our first thought, that the dimentions were not the same, as you explain.

If that is indeed what we are experencing, and so long as the regulation is good, which it is, then how do we be sure it's the normal variation in dimentions and not a powder issue?

Jim Watson · June 10, 2007, 05:15 PM

200 fps sounds a bit extreme, presumably the 'smith used the same brand barrel and the same reamer for both.
Is the selector still functional?
If so, what happens if you fire the top barrel first?
What if you shift and shake the gun around between shots to shake the powder loose after it is shifted by recoil?

There is a good deal of position sensitivity with nitro powders in the BP cases. I have shot revolver loads in which it makes a LOT of difference as to whether the muzzle was up, down, or in recoil before shooting.

Accurate Arms 5744 is advertised to be less position sensitive than most.
Ed Harris said 2400 was, too.

There are some other little tricks like case fillers, which I am not real comfortable with; and there is some data on loading a case full of VERY slow rifle powder which gives Trapdoor pressure and velocity levels and no position sensitivity because it can't move.

bswiv · June 10, 2007, 05:38 PM

Selector works. I guess we should have thought of shooting the barrels in oposit sequence to see if that made a difference. Will do that next trip, along with the shaking thing between shots.

If those actions make a difference in the velocity spread then I'm guessing we should try another powder, one that fills the case more fully....

And yes the barrels were both done with the same reamer, both are Douglas as far as I know.

We also looked at the fired cases. It must be that the pressures, even with the variation in velosity, are still rather low as the primers were not flat and showed little sign of flowing back. Cases came out of rifle easy too.

crowbeaner · June 11, 2007, 07:37 PM

I'd try Reloder 7 or IMR 3031 and tinker with the charges to try to get both barrels to regulate. Any good loading manual should have data for trapdoor level loads. I'd be a little leary of using faster burning powders, but cast bullet manuals usually use pistol powders.

June 10, 2007, 04:02 PM	#1
bswiv Senior Member Join Date: June 4, 2006 Location: NE FL....... Posts: 1,081	4227 in 45/70 question? Had a 45/70 at the range today using some 300 grain reloads in front of 29, 31 and 33 gr of 4227. Loads came from the Hornady #4. Trapdoor pressures. Cases were about 1/2 full. Used a measure that was checked against two scales and then a load or two checked during the process. On the chronograph they were very inconsistent. As much as 200 fps different. This was in a O/U rifle. In every instance the top barrel, which was firing second, produced higher pressures. Wondering if this could be caused by the partially empty case setteling the powder between shots from the recoil.....or something we totally missed? We know we're going to have to make another trip with the chronograph to see what is happening but we'd like some input as to what to look for or do to find out what is going on here.

June 10, 2007, 04:15 PM	#2
Trapper L Senior Member Join Date: November 20, 2006 Location: South Texas Posts: 804	I'm not sure the question but if your expectations that both barrels were going to shoot the same- you would be wrong. No two barrels will shoot the same or have the same pressure. Minute differences in machining will make each different. Chamber dimensions may not be perfectly the same, the bore may be slick in one and a little rough in the other. That's why one load doesn't always shoot in every gun. You are going to have to treat each barrel just like it was a different rifle. And if it was easy- anybody could do it.

June 10, 2007, 04:23 PM	#3
bswiv Senior Member Join Date: June 4, 2006 Location: NE FL....... Posts: 1,081	That was our first thought, that the dimentions were not the same, as you explain. If that is indeed what we are experencing, and so long as the regulation is good, which it is, then how do we be sure it's the normal variation in dimentions and not a powder issue?

June 10, 2007, 05:15 PM	#4
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,542	200 fps sounds a bit extreme, presumably the 'smith used the same brand barrel and the same reamer for both. Is the selector still functional? If so, what happens if you fire the top barrel first? What if you shift and shake the gun around between shots to shake the powder loose after it is shifted by recoil? There is a good deal of position sensitivity with nitro powders in the BP cases. I have shot revolver loads in which it makes a LOT of difference as to whether the muzzle was up, down, or in recoil before shooting. Accurate Arms 5744 is advertised to be less position sensitive than most. Ed Harris said 2400 was, too. There are some other little tricks like case fillers, which I am not real comfortable with; and there is some data on loading a case full of VERY slow rifle powder which gives Trapdoor pressure and velocity levels and no position sensitivity because it can't move.

June 10, 2007, 05:38 PM	#5
bswiv Senior Member Join Date: June 4, 2006 Location: NE FL....... Posts: 1,081	Selector works. I guess we should have thought of shooting the barrels in oposit sequence to see if that made a difference. Will do that next trip, along with the shaking thing between shots. If those actions make a difference in the velocity spread then I'm guessing we should try another powder, one that fills the case more fully.... And yes the barrels were both done with the same reamer, both are Douglas as far as I know. We also looked at the fired cases. It must be that the pressures, even with the variation in velosity, are still rather low as the primers were not flat and showed little sign of flowing back. Cases came out of rifle easy too.

June 11, 2007, 07:37 PM	#6
crowbeaner Senior Member Join Date: June 4, 2007 Location: Upstate SC Posts: 1,943	I'd try Reloder 7 or IMR 3031 and tinker with the charges to try to get both barrels to regulate. Any good loading manual should have data for trapdoor level loads. I'd be a little leary of using faster burning powders, but cast bullet manuals usually use pistol powders.