Author Topic: Chopped down my 17HMR (Read 687 times)

KN · « **on:** November 17, 2003, 01:52:41 PM »

After reading Bullberrys test on velocity and the 17HMR I decided that my 23" factory barrel was probably longer than it should be. So I trimmed it to 18" and re-crowned. When test firing it I found some thing surprising. When the barrel was stk length my best groups were shot with one hand resting on the scope turret for support as the rifle had a tendency to jump just a little bit. But after shortning it no longer jumped! I can now shoot the rifle without supporting it. After thinking about this I came up with the theory that if the powder was no longer pushing the bullet at about 18" then it would be running the last 5" of barrel with nothing but momentum. That I figured was a force that is pulling on the barrel before the bullet exits. Thus causing some ill effects accuracy wise. By the way, indoors at 25yds it will stack them real easy. Cant wait to get it out to 100. What do you all think of my theory? KN

Tdot · « **Reply #1 on:** November 17, 2003, 03:05:12 PM »

I don't buy it!
Jerry

KN · « **Reply #2 on:** November 17, 2003, 03:42:26 PM »

Why not? KN

Tdot · « **Reply #3 on:** November 17, 2003, 06:05:40 PM »

KN,
Response to: Why not?
After reading Freds test results.
In my opinion, I reasoned that the pressure resulting from the burning powder peaked at about 19".
I did not conclude that the bullet would continue on down the remaining barrel with nothing but momentum driving it.
In my opinion, the pressure is still a driving force even past the peak.
I don't understand. "That I figured was a force that is pulling on the barrel before the bullet exits."
In my opinion, I don't think the 23" barrel would cause some ill effects accuracy wise, unless there was a crown problem.
I am glad that you are satisfied with your cutting and recrowning of the barrel and hope that it holds true at 100 yds and more.
I still don't buy it, but thats just my opinion. Every body has one!!
Jerry

KN · « **Reply #4 on:** November 17, 2003, 07:07:42 PM »

My reasoning was that the bullet is slowing down after it hits 19" therefore there can't be enough preasure to overcome the friction/weight of the bullet going down the last few inches. So, the friction/weight/momentum of the bullet in the barrel would be putting a forward thrust on the barrel as it exits. Like I said, this is just a theory. I have no proof this is happening, It just seems logical to me. Thats why I asked for oppinions. as far as accuracy goes it was pretty good before I cut it. Under an inch at 100 meters. I'm just kind of a fanatic when it comes to accuracy. My 14" barrel would out shoot it though, 3/4" at 100 is typical on a calm day. I appreaciate any feed back I get on this, just trying to pick some brains. KN

Sean · « **Reply #5 on:** November 19, 2003, 05:43:32 AM »

Pressure doesn't just disappear after it peaks. Sean

KN · « **Reply #6 on:** November 19, 2003, 12:29:32 PM »

No it doesn't, But the bullet is slowing down before it leaves the barrel. So what do you think is happening as far as forces on the barrel are concerned? I still think that since the bullet is slowing down, the barrel is being pulled forward just before the bullet exits. The force behind the bullet has to be less than the force needed to slow the bullet in the barrel. Thats why I think its pulling on the barrel. KN