Slow Barrel

[Rummer]

Hello all:

I was chronographing loads for my .35 whelen.  I found that my velocities were consistently lower than advertised.

With both 200 and 250 grain remington factory loads My average was 85 fps below remington's ballististic charts.  I initially attributed this to the fact that remington uses 24" barrels in their testing and my whelen has a 22".

Then I chronographed 58.5 gr of IMR-4320 behind a 200 grain bullet.  My average was 2590, my manual lists this load at 2700.

Could the fact that I have a .357" barrel be a factor.

Rummer

[Brithunter]

Hi There,

     Sorry but I have no ideas other than it does happen. My .308 CZ-Brno model 601 seems to have a slow barrel as chrongraphed velocities are down frm what they should be according to manuals. However the Deer and foxes that have fallen to it don't seem to have noticed  :grin:

[beemanbeme]

its been said a fellow should never chronograph his favorite hunting load....... :grin:
Since I seldom come up with an exact match of components between the manual and what I have, I don't pay a whole lot of attention to what the book sez about velocity.  Some of my loads are faster; some slower.  I chrony my graduated loads and when the velocity gain starts to flatten out, I call that near max (other things being equal), back off a bit and call it happy.  The velocity falls where it may.  If it is considerablely below what I think the cartridge can do, I look to another powder.  
I don't feel there's any real life difference between a bullet going 2700fps and one going 2900fps.

[mountainview]

Rummy, could be your load may not exactly match what the factory used and then there are other factors, environment when loading, air density/humidity, etc, etc. Sounds like you are within 10% of published value so I would not be overly worried as long as the load shoots accurate and otherwise does what you want it to.

[Rummer]

I can certainly live with that bullet travelling at 2590.  That is still faster than many .358's push a 200 grain bullet, and if it works in the .358 it will work in the whelen.  I don't see 100 fps less than advertised as a handicap in the field.  That 200 grain loading is going to be my deer load this fall.  


I was really trying to figure out:
1) Do I have a slow barrel?
2) What are the causes.

Thanks for the replies guys.

Rummer

[riddleofsteel]

You can take two factory produced rifles with serial numbers very close together and get wide variations in muzlle velocity given identical loads. I have a 25-06 Remington Sendero that produces 3250 FPS with 53.5 grains of H4831 and a 117 grain Hornady SPBT and a BR2 primer. This load shoots 1/4" groups at 100 yards. I have two friends that bought identical rifles from the same dealer within two weeks on my purchase. One of the rifle's serial number is only 50 from my serial number. Neither of these rifles can be made to produce over 3100 FPS with these componets without signs of high pressure. However, all three rifles will shoot 1/2" or under groups with this powder, bullet and primer combo.
In an attempt to discover the difference we casted the chambers on all three rifles. The chamber neck on my rifle is a TINY bit larger than the other two chambers and my chamber shoulder is a TINY bit forward compared to the other two rifles which means my chamber and chamber neck is slightly over sized. It has not affected my accuracy but it has given me a "FAST" rifle compared to most of the other 25-06's I have compared it to, even those with 26 barrels like mine.
I truely do not know why some seemingly identical rifles shot faster with the same loads than others. But I would be willing to bet that if you examine all the varibles you will find differences that make the difference.