Loose bore = Less Velocity?

[Shane Lindsey]

Greetings,

I have a rifle that is a wildcat. I am not getting the velocities without pressure that others have seemed to get listed on here. Not even close.
I am curious if a "loose" bore would cause the lack of velocity? Meaning, I am using more powder to get the same velocities, but the bore is so loose that it just doesn't get it moving??? I have had a tight bore on a Christensen barrel that pressured fast, usually around start loads.

When I push a patch through, it is kind of loose compared to my other 338 barrel.

Anyone else have this before?

 

[memtb]

Following with interest! memtb

 

[just_jon]

Your loose bore theory makes sense. One way to test it is to make a cast of your bore with Cerrosafe. If you go this way, be sure to give it 30 minutes after removal to return to bore size before taking measurements.

As for reaching pressure before desired velocity, I find that is an indication that a faster burning powder is needed.

 

[VinceMule]

I have seen bores that measured tight on the breach end and tight at the muzzle, opening up in the middle, and bores that measure tight on the breach end and open up toward the muzzle(called trombone barrels) exhibit issues like Shane describes.

There are many factors that can contribute, but barrels are individuals. Rough barrel bores are another type of animal to deal with.

The fouling build-up in the bore can do some strange things. I saw a 6.5 x 55 exhibit over max pressure on below minimum charge due to copper fouling.

 

[Varmint Hunter]

You should also be skeptical of what other wildcat shooters are getting with their rifles. If there was ever a bunch of guys who liked to push the outer limits of practical pressure, they reside in the wildcat crowd. No offense intended to anyone.

 

[Old Rooster]

Slugging the bore may give results unless like VinceMule says it may be loose in the middle which would be hard to see from slugging.
I'm following this also.

 

[Shane Lindsey]

Your loose bore theory makes sense. One way to test it is to make a cast of your bore with Cerrosafe. If you go this way, be sure to give it 30 minutes after removal to return to bore size before taking measurements.

As for reaching pressure before desired velocity, I find that is an indication that a faster burning powder is needed.

Have used RL17, Staball 6.5, H4350, Shooters World Precision, CFE223and finally settled on Varget.

Top velocities have absolutely no accuracy. I am basically at the top end of published load data for a similar/parent type cartridge. Velocity is slightly below what those published loads are, which is fine. Accuracy is now just MOA with 213 Hammers and Varget for 2677 FPS. Plenty of stomp for my Virginia woods.

 

[Shane Lindsey]

You should also be skeptical of what other wildcat shooters are getting with their rifles. If there was ever a bunch of guys who liked to push the outer limits of practical pressure, they reside in the wildcat crowd. No offense intended to anyone.

Oh yeah, I watch my pressure signs, especially with this as it said to hide pressure. I am nowhere close to others out there.
Buuuut, I am not looking to be a unicorn with a bolt sticking out of my head.

 

[Shane Lindsey]

I have seen bores that measured tight on the breach end and tight at the muzzle, opening up in the middle, and bores that measure tight on the breach end and open up toward the muzzle(called trombone barrels) exhibit issues like Shane describes.

There are many factors that can contribute, but barrels are individuals. Rough barrel bores are another type of animal to deal with.

The fouling build-up in the bore can do some strange things. I saw a 6.5 x 55 exhibit over max pressure on below minimum charge due to copper fouling.

I am a clean it after shooting it kind of guy. Rarely will they get 40 rounds through them before I clean them back to steel. Every few hundred or so, a little JB for throat maintenance as well.

 

[Lefty7mmstw]

One thing I've seen is some rifles just don't push with certain bullet weights and certain powders. I had a remmy lh 30-06 for a spell that pressured out at 2600 fps with 165 Hornady pills and I 4350. Every other 30-06 I've ever owned will do 2800-2900 fps with that combo. Odd thing was it would do 2550 fps or so with 200 Sierra's and I 4350.
I'd switch out what I'm doing with powder and/or bullet weight to see what's up. You may have to slug the pipe also as others have said.

 

[Shane Lindsey]

One thing I've seen is some rifles just don't push with certain bullet weights and certain powders. I had a remmy lh 30-06 for a spell that pressured out at 2600 fps with 165 Hornady pills and I 4350. Every other 30-06 I've ever owned will do 2800-2900 fps with that combo. Odd thing was it would do 2550 fps or so with 200 Sierra's and I 4350.
I'd switch out what I'm doing with powder and/or bullet weight to see what's up. You may have to slug the pipe also as others have said.

175, 200, 225, 213, 250s. Multiple pills. All seem to be about what the similar/parent case does.
Oh well.

 

[Lefty7mmstw]

175, 200, 225, 213, 250s. Multiple pills. All seem to be about what the similar/parent case does.
Oh well.

probably either a loose bore or too long of a throat then

 

[Calvin45]

Greetings,

I have a rifle that is a wildcat. I am not getting the velocities without pressure that others have seemed to get listed on here. Not even close.
I am curious if a "loose" bore would cause the lack of velocity? Meaning, I am using more powder to get the same velocities, but the bore is so loose that it just doesn't get it moving??? I have had a tight bore on a Christensen barrel that pressured fast, usually around start loads.

When I push a patch through, it is kind of loose compared to my other 338 barrel.

Anyone else have this before?

Any chance your wildcat cartridge has "Sherman" in its title? Not bashing that line of cartridges but I do distinctly recall some pretty awesome numbers quoted for the case volume…and a fair amount of folks not realizing those numbers

 

[Shane Lindsey]

probably either a loose bore or too long of a throat then

I loaded to the length advertised and nada. Just decided to try the Hammers as they were less sensitive to jump so I could load mag length.