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Having problems with getting consistant velocity

 
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  #15  
Old 12-21-2001, 11:07 PM
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Join Date: Jul 2001
Location: San Antonio, Texas
Posts: 244
Re: Having problems with getting consistant velocity

Well hell! I just hate it when someone says here are a few things that may be the problem and I have to check off damn near every one.

1. Bullet olgive the same? Well there all from the same lot. I assumed that Matchkings would be fairly consistant. Using a stoney point comparator the seating depth varied by no more than .002 for most all the loads. But I'm still waiting for a set of Starret dial calipers so can't work on this one yet.

2.I use a digital (calibrated each time) for quick weight check but use a powder measure to get within a grain then trickel the rest into an RCBS 5-0-5 scale. I use calibration weights to check both scales every time I use either.

3. Nope! I've been sizing the full length of the neck. I use the Redding bushing neck die w/no expander.

4.Bullets are making it to the target. I checked for key holing and to make sure that one bullet made one nice little hole. They are making it to the target intact.

5.Nope! Not weighing bullets. I just weighed 10 and they seem to be right at 134.9-135gr.

6.Chrony brand. I know, but just trying to pay for the best equipment all at once is damned expensive. Plus I bought this one three years ago before I knew any better. An Oehler 35P is on my christmas list along with a strain gage. I'll just have to keep dreaming for a little while longer.
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  #16  
Old 12-22-2001, 12:03 AM
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Join Date: Jul 2001
Location: San Antonio, Texas
Posts: 244
Re: Having problems with getting consistant velocity

I just went through and found a couple of pieces that weighed 269.2 and 270.4. Both were unfired. Filled with water and an inverted primer(each weighed 5.0gr) inserted they weighed 386.7 and 387.6.

(386.7 - 5.0 - 269.2)= 112.5 gr H2O
(387.6 - 5.0 - 270.4)= 112.2 gr H2O

.9 gr difference in brass only equated to .3gr water difference.
I repeated this 3x only once did the numbers differ by more than .1gr or so. The first try I failed to get an air bubble out of one case. Problem was found and corrected.

Moving it up 2gr moved it from 3611 to 3615. Going from 3611 to 3727 took 4 additional gr of powder. I just can't see how such little variation could effect speed so much when it took 4gr more powder to increase 116fps.

[ 12-21-2001: Message edited by: txhunter ]
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  #17  
Old 12-22-2001, 12:44 AM
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Join Date: May 2001
Location: Pennsylvania
Posts: 1,757
Re: Having problems with getting consistant velocity

Come on now Tx

You asked for help and we are certainly trying to do our part.

It is a pain in the rear end sometime trying to figure out what the problem is on these guns.

I think you called the shot though with the Chrony cronagraph. I'll bet that's your problem.
I have seen two of them together be off from 75 to 200 fps between shots.

I'd say your deviation is not what you think it is because you have checked and corrected everything else the way you should have.

Go out and shoot the hell out of that 270/300 Ultra and have some fun.

I have always said, the smell of burning gunpowder makes me horney even at my older age. I always try to shoot as much as I can for obvious reasons.

Have a nice Holiday season.
Good Shooting Always.
Darryl Cassel
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Darryl Cassel
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  #18  
Old 12-22-2001, 09:55 AM
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Join Date: Jul 2001
Location: San Antonio, Texas
Posts: 244
Re: Having problems with getting consistant velocity

Yes, you are doing alot to help!

I had a feeling this problem would be simple. Its been jumping up and down yelling here I am here I am, hey dumb ass over here. I still wouldn't have notice even if it had jumped up and bit me on the ass. I was to busy trying to figue out what I was doing wrong. All this thinking is hurting my brain, think i'll go shoot some rocks. I just love seeing them explode!

Thanks for the Help!
Yall have a good Christmas and a great New Year.
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  #19  
Old 12-22-2001, 02:58 PM
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Join Date: May 2001
Location: Sask. Canada
Posts: 2,410
Re: Having problems with getting consistant velocity

I envy your going out rock shooting, ours all pretty much disappeared the last couple of days under a hell of a snowfall. Problem is the snow closes a lot of roads and trails so we can't get back in the boonies to shoot.
Like you, I love shooting rocks - it should be an Olympic sport, right!

A while back my partner and I painted targets and mild-dot grids on a big rock with the intent of hurling .308 match bullets from across a big valley. Problem was we were not across from our shooting location as we thought, damn rock was way down the valley, over 2000 yards and our bullets didn't even kick up dust out that far.

Rock-chucking, smucking or whatever other discriptive 'ucking term you might call it, is a fine way to burn ammo.
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  #20  
Old 12-23-2001, 10:40 AM
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Join Date: Jul 2001
Location: San Antonio, Texas
Posts: 244
Re: Having problems with getting consistant velocity

No rocks exploded by me yesterday. About twenty minutes before I was going to get ready the bottom fell out. Shoot'n in the rain just ain't no fun!
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  #21  
Old 12-23-2001, 01:26 PM
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Join Date: May 2001
Location: Arco, ID 83213
Posts: 80
Re: Having problems with getting consistant velocity

Unless you are jumping the bullets a long ways to the lands then a large velocity spread of 75 fps. will almost always be attributed to inconsistent ignition and burning of the powder. I would suggest 1. Trying different powders, and 2. trying different primers, in that order. Even in large cases you can get the SD down to under 15 fps. Fifty fps. spread at 1000 yds. is worth .7 minute of angle with your 150s.

High velocity is not a cause of inaccuracies but high pressure can, and often is, a cause. Consistent ignition and complete and consistent powder burn is the holy grail of accuracy loads. It is often the case that the most efficient powders for a given cartridge and rifle will give the best velocity and accuracy. It is not very often, however, that the best accuracy is obtainable at the highest safe velocity. That is, in fact, quite rare.

[ 12-23-2001: Message edited by: Warren Jensen ]
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