if the peak velocity is reached at 18" i would say a 20" barrel would be the ideal length, this would get everything out of the powder charge and give the pressure 2" to normalize for shot consistancy and accuracy.given that you knew that the peak velosity was reached at 18", this would be a logical guess on the 17hmr-with the slightly larger powder charge over a 22lr i would say peak veloicity was at 20" so a 22" barrel would be the optimum lenghth.

 

Heck, it's easy. Get the 26 incher and start cuttin' it down! Piece o' cake.

Actually there's another thing to consider, and that's the tightest spot in your barrel. Lots of high-end rimfire shooters are starting to "slug" their barrel to find out A) where the tightest spot is, and B) just how much that spot squeezes the bullet. Then they (some of them) cut and recrown the barrel at that point, assuming it's a realistic length.

According to them, after a bullet is squeezed, it just "rattles" down the rest of the barrel. (That's exaggerating, but you get the idea) If the tight spot coincides closely with the maximum velocity, then you have nothing to gain, and accuracy to lose.

'Course that's the extreme.

In the meantime, I've got a Saws-All you can borrow. :laugh: :hoboy: :laugh:

Skein

 

On a serious note, have you ever been out to Varmint Al's web page? If not, look him up and read his tests of the 17HMR. I thought it was going to be the usual fare, but I ended up impressed and informed by his report. Well worth the time to read.

Skein

 

On a serious note, have you ever been out to Varmint Al's web page? If not, look him up and read his tests of the 17HMR. I thought it was going to be the usual fare, but I ended up impressed and informed by his report. Well worth the time to read.

Skein

Thanks Skein,

I have been to Varmint Al's, but haven't looked at what he had to say about the .17 HMR.

It's only been recently that I've had my interest piqued on this. Having a two .22 Hornets (rifle, pistol), a .222 Sako HB, and a 40X in both .223 and .220 Swift, it's easy to overlook "recent developments" in the (mistaken?) attidude of "What For?"

But then, we know "What For"! It's a new cartridge and that means new/different guns to play with! :cheers:

That's What For! :grin:

 

I checked with Hornady on this and they told me that the max velocity for the .17 HMR occurs in 22". The velocity will remain the same for another inch or two then friction will start slowing it down.

Shorter than this they say (in rifle lengths) will decrease the velocity by ~25fps/inch.

 

They did a test of this at Bullberry. It looks like their highest velocity was reached at 19 inches. They did the same type of test, starting at 22" and cutting off one inch at a time.

You can find the resutlts here.

Ni!

 

Interestin results...

Did you notice that the 21" barrel shot faster than the 20" barrel (with the 19" barrel shooting the fastest!)?

It's interesting to note that one EXTRA-slow round in the 20" 5-shot string dropped the average velocity for the entire string's average.

With those lower velocities occuring in several of these strings and none in others, it seems like the results could be skewed a little. Did you notice that while the 22" barrel had the lowest velocity round in it, it also had the HIGHEST velocity round also.

Seeing this, I'm surprised they didn't try something like 20-shot strings in an effort to reduce the effects of anamolous data points.

It looks to me like you could get 4 out of 5 "faster" rounds in any barrel length between 19" and 22" and have gotten the highest velocity. In other words a "luck of the draw" situation.

 

Yeah, that test they did doesn't seem to be the most scientific in design. It would also have been useful to try the test with several different barrels, but I guess they didn't want to spend that kind of money.

What that data set tells me is that the results will probably vary somewhat from barrel to barrel, and that as long as you're in that 19 to 22 inch range, you can probably call it close enough and make your decision on other factors such as brand, weight, balance, price, etc.

Ni!