Reloading velocity issue: I can't figure that one out!!!

[Mr.Boiler]

H4350 or IMR4350? There is a difference albeit slight. Just asking. Ive done it before.

[seabast]

H4350 or IMR4350? There is a difference albeit slight. Just asking. Ive done it before.

I use H4350.


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[skypilot]

I always use the actual drop data to validate my MV regardless of book values. It is literally how one "trues" their dope.

On the lower velocity using more of the same powder and yet a lighter bullet thing, consider a hotter or at least a different primer. Also case capacity difference because of different bullet length, weight, profile, case empty space, seat depth, neck tension etc. can affect velocity.

I shot a 243 and reloaded for it for decades. Varget is good and I use it quite a bit. Maybe we can help if you provide more info. It does seem counter intuitive to use more powder and a lighter bullet only to get slower speeds.

[jaycee]

Your velocity drop is due to several factors, going from a 100 gr. bullet to a 70 gr. , there is a noticeable difference in the bearing surface area of the bullet therefore you do not have as much friction and the bullet is out of the muzzle before enough pressure builds up. Shooting at dusk or twilight you will see a large muzzle flash , this is powder being burned up outside the barrel showing an inefficient powder burn and therefore causing your velocity drop .

When the firing pin hits the primer, the pressure caused by that flame alone is enough to get your bullet moving into the rifling and the subsequent burning of the powder sends it on up further till it exits, but being of light weight it has already exited before the powder has burned up completely and built up enough pressure to get the velocity you require, that is why you would see a long muzzle flash towards dark indicating an inefficient powder choice.

To get your velocity to where it should be, the powder should burn within the length of your barrel, using a light bullet and a slow burning powder doesn't allow for this to happen.
When shooting lighter bullets, you should go to a faster burning powder, varget has been suggested, myself I have had extremely accurate loads using imr 4320 powder, imr 4064 works also but is not as accurate in my rifle.
Your reloading manual will list several other powders that will give you the higher velocity that you are looking for.

This may all sound confusing, but I am having a hard time typing as I have a Gout Flare up in my right hand , and I may not be explaining things as clearly as I would like .

[Fox]

Your velocity drop is due to several factors, going from a 100 gr. bullet to a 70 gr. , there is a noticeable difference in the bearing surface area of the bullet therefore you do not have as much friction and the bullet is out of the muzzle before enough pressure builds up. Shooting at dusk or twilight you will see a large muzzle flash , this is powder being burned up outside the barrel showing an inefficient powder burn and therefore causing your velocity drop .

When the firing pin hits the primer, the pressure caused by that flame alone is enough to get your bullet moving into the rifling and the subsequent burning of the powder sends it on up further till it exits, but being of light weight it has already exited before the powder has burned up completely and built up enough pressure to get the velocity you require, that is why you would see a long muzzle flash towards dark indicating an inefficient powder choice.

To get your velocity to where it should be, the powder should burn within the length of your barrel, using a light bullet and a slow burning powder doesn't allow for this to happen.
When shooting lighter bullets, you should go to a faster burning powder, varget has been suggested, myself I have had extremely accurate loads using imr 4320 powder, imr 4064 works also but is not as accurate in my rifle.
Your reloading manual will list several other powders that will give you the higher velocity that you are looking for.

This may all sound confusing, but I am having a hard time typing as I have a Gout Flare up in my right hand , and I may not be explaining things as clearly as I would like .

The OP has a listed load with a listed velocity for a similar barrel length, how does your post make sense when directly contradicting published data?

[rippin_355]

There are so many variables. The OP's scales could be inaccurate. He could have a long throat and pressure is being bled off before the bullets engages the rifling. Also neck tension could be loose or the bullet not crimped and not building the same pressure. And last but not least his chronograph could be the issue. They are known to be all over the place.

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[jaycee]

The OP has a listed load with a listed velocity for a similar barrel length, how does your post make sense when directly contradicting published data?

By talking with people directly involved in the industry, my 59 years of reloading experience, 5 years commercially, and tons of reading about the subject [reloading] and it's variables, so that when I say something about it, I do not sound like someone who only thinks they know !

There are so many variables that in cross referencing my many reloading manuals, the published velocities for a particular caliber vary from one manual to the next.

[seabast]

I always use the actual drop data to validate my MV regardless of book values. It is literally how one "trues" their dope.

On the lower velocity using more of the same powder and yet a lighter bullet thing, consider a hotter or at least a different primer. Also case capacity difference because of different bullet length, weight, profile, case empty space, seat depth, neck tension etc. can affect velocity.

I shot a 243 and reloaded for it for decades. Varget is good and I use it quite a bit. Maybe we can help if you provide more info. It does seem counter intuitive to use more powder and a lighter bullet only to get slower speeds.

Pressure builds quicker in barrels as projectile weight increases. Land grove diameter verses bullet diameter also plays a huge part.

Try a different powder.

Your velocity drop is due to several factors, going from a 100 gr. bullet to a 70 gr. , there is a noticeable difference in the bearing surface area of the bullet therefore you do not have as much friction and the bullet is out of the muzzle before enough pressure builds up. Shooting at dusk or twilight you will see a large muzzle flash , this is powder being burned up outside the barrel showing an inefficient powder burn and therefore causing your velocity drop .

When the firing pin hits the primer, the pressure caused by that flame alone is enough to get your bullet moving into the rifling and the subsequent burning of the powder sends it on up further till it exits, but being of light weight it has already exited before the powder has burned up completely and built up enough pressure to get the velocity you require, that is why you would see a long muzzle flash towards dark indicating an inefficient powder choice.

To get your velocity to where it should be, the powder should burn within the length of your barrel, using a light bullet and a slow burning powder doesn't allow for this to happen.
When shooting lighter bullets, you should go to a faster burning powder, varget has been suggested, myself I have had extremely accurate loads using imr 4320 powder, imr 4064 works also but is not as accurate in my rifle.
Your reloading manual will list several other powders that will give you the higher velocity that you are looking for.

This may all sound confusing, but I am having a hard time typing as I have a Gout Flare up in my right hand , and I may not be explaining things as clearly as I would like .

Thanks you guys!!

I really had a hard time to believe that a barrel 2” shorter in association with a light bullet and a slow powder could affect the velocity that much but now I’m pretty sure it does.

Yesterday after reading your comments I looked for a faster powder used in this reloading data that I had in stock. Sure enough I had H4895 and lots of IMR3031. So, up I went to reload 5 shells of each (36g for IMR3031 and 37g of H4895). Both chrono very close to the reloading data, around 3250fps. IMR3031 grouped alright too.

The wind died and having more time on my hand I decided to quickly load up 5 more shells of 38g of IMR3031 that I could shot over 300 yards, after all that’s why I’m working a load for. Chrono average 3312fps and group around 4.5”.

Anyway I will keep H4350 for the 100g because it groups and chrono very well but I’m going to experiment a lot more with the 70g.
It’s pretty neat to learn something!

IMG_4353.jpg

[seabast]

There are so many variables. The OP's scales could be inaccurate. He could have a long throat and pressure is being bled off before the bullets engages the rifling. Also neck tension could be loose or the bullet not crimped and not building the same pressure. And last but not least his chronograph could be the issue. They are known to be all over the place.

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I had check most of these variable (scale and chrono works well), I don't crimp for my bolt action.

[seabast]

The OP has a listed load with a listed velocity for a similar barrel length, how does your post make sense when directly contradicting published data?

Sorry if I wasn't clear but my barrel is 2" shorter. I believe Jay and others were right, these 2" made a big difference in this case.
I never seen that with my 30-30 or 45-70 I assume it'sprobably because heavier bullets and faster powders are used?