Can you be tooo fast?

[hugo121175]

I had just gotten done a week ago working up a load for my Winchester Model 70 Pro 64 S/A. The barrel is chambered in 270WSM is a Hart SS Contour 10-MTU 26" long has a 1:10 twist.

I worked up IMR-4350 from 58gr to 62gr, Bullets are SMK 135gr, COAL +0.010" jammed, and ladder tested without any pressure signs. Best range was from 60.2gr to 60.8gr. I fired two five round groups from 60.2gr to 60.8gr COAL at +0.010" jammed in 0.1gr increments. The best overall groups were from the set of rounds loaded with 60.5gr COAL +0.010" jammed.

This week-end I shot over at TVP in Ohio. Until then I had not chrono-ed the round due to not remembering to bring the chrono to the range with me all five times I went. When I did chrono the rounds at TVP the average was 3250fps with +/- 25fps deviation.

With all that said..... Is it possible to be firing these pills too fast? The rifle shot well at TVP, and I check all my cases once I had gotten home. All my case were gtg without any pressure signs.

Should I just leave it as is, or do another ladder test starting at 55.0gr to 60.0gr, and see where the node is at lower velocities?

 

[rocky_lange]

Re: Can you be tooo fast?

Speed kills. The faster the bullet, the shorter the barrel life.

That being said, the faster the bullet, the more energy it imparts upon the target.

If all you will do is punch paper, then I'd look for an accurate node a little slower. If you are going to hunt with it, keep the speed.

 

[jrob300]

Re: Can you be tooo fast?

You might not know for a few more firings if these are too hot or not. They can show absolutely no signs of pressure and loosen primes pockets, so watch for that.

It's a little frightening when you realize you've fired them that way 2-3 times

John

 

[tatemarb]

Re: Can you be tooo fast?

Have you ever made up a dummy round at the COAL you are using (.01" jammed), chambered it, then extracted and measured COAL again? If you are pushing the bullet deeper in the case when you chamber then case capacity is decreased. That along with no jump for the bullet, will lead to higher chamber pressures.

And, like jrob said, pressure can be excessive and not show any pressure signs for some time if ever.

The only way to consistently/safely measure chamber pressure is with equipment designed to do so.

I would be careful of that load (temp especially).

tater

 

[TresMon]

Re: Can you be tooo fast?


A few thoughts:

To answer your initial question you can shoot bullet at too great a speed.
Occasionally you hear a long range match shooter say they had a bullet "disappear" and it's of course scored as a complete miss of the target. This is typically with guys shooting 6.5-.284 Norma rounds- running 6.5mm pills hot. Most of the time when a bullet comes apart in flight it is from heat. I'm with the crowd that believes the lead core liquifies. It's contained by the bore & jacket. When it exit's the bore the copper jacket alone is not strong enough to contain the centrifugal force of the spinning molten lead and thus the bullet comes apart in flight.

1. Are all your bullets making it to the target?
2. You said there were not signs of excessive pressures. So you should be good, but running safe but hot loads will junk out brass faster than mild loads.

3. The Sie load manual shows 3300f velocities for that bullet/cartridge reported with a 24" barrel. So you running a 26" tube would give you even more speed, so sounds like you have a safe load.

4. More times than not, not always, but often bullets just don't seem to shoot tiny little groups when fired above 3000 fps. Invariably two people will post photo's of great groups they shot with their 7 Rum shooting 3600 fps now that I said that but generally speaking, stuff just does not -tend- to do so good above 3000- is the general consensus at the 1000yd range I shoot at.

5. You mentioned a 25fps ES of velocities. For best accuracy at long range try to whittle that number to 12 or less.

Let me know how I can help.
T

 

[hugo121175]

Re: Can you be tooo fast?

Thanx for all the help guys. I'm going to be working up from 55gr to 60gr. Then I'll see were the node is at a lower velocity.

Guntard: That was what was concerning me..... Barrel Life. I'll be punching paper and ringing steel with this rifle, so maximum energy is not a must for me.

Jrob: Thanks for the heads up. I reload for a bunch of other cartridges (.223, 270Win, 270WSM, 30-06, 300WM, .338LM, and 10 different pistol calibers). I just haven't seen these velocities after a ladder test with book "Safe" max loads.

Tater: I do understand that if I load .01" over COAL that the bullet when chambered will be pushed back into it's case. That is what I want. Check out Tres's post: http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1713419#Post1713419

Tres: The bullets made it to all targets except the misses at 1165. They were "No Calls" by my spotter.

Like I said above, I'm going to drop down the powder weight to 55gr and ladder test up to 65gr. I think I'll just leave my chrono in the SUV, so it's not hard to forget.....

Hugo

 

[TresMon]

Re: Can you be tooo fast?


Personally if your shooting that far I'd get the heaviest match bullet I could come up with for the caliber.

 

[hugo121175]

Re: Can you be tooo fast?

I was thinking of trying those yellow box 150gr pills

http://www.midwayusa.com/viewProduct/default.aspx?productNumber=619128