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#6042254 - 11/21/15 04:14 PM Shooting 300 win mag at elevation.
fast88 Online   content
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Registered: 10/13/13
Posts: 533
Loc: Smithville TX
So this year for my hunting rifle I decided to load up 210 vlds. At my home elevation around 600 feet and my load of 79.5 grains of Retumbo with the bullet seated to the lands produced a 1/2 in group at 300 yards with no signs of pressure. I didnt chrono it because I hunt at an elevation of 3000-4400 so I wanted to get the correct velocity at the ranch. I chronoed there today and was suprised at the velocity 2997 avg and ES of 21 over 15 shots but they are now showing a light extractor mark on the brass but no flattened primers. Is a pressure increase common at elevation changes?

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#6042292 - 11/21/15 04:43 PM Re: Shooting 300 win mag at elevation. [Re: fast88]
FiremanJG Offline
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Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
What was the ambient temp at each location?

Is it the same powder lot?
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#6042392 - 11/21/15 06:19 PM Re: Shooting 300 win mag at elevation. [Re: fast88]
Cleric Offline
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Registered: 03/11/12
Posts: 2579
Fresh brass or once fired?

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#6042821 - 11/22/15 06:37 AM Re: Shooting 300 win mag at elevation. [Re: Cleric]
fast88 Online   content
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Registered: 10/13/13
Posts: 533
Loc: Smithville TX
Originally Posted By: FiremanJG
What was the ambient temp at each location?

Is it the same powder lot?


The powder was the same lot # and out of the same 1# canister.

Ambient temp during load development was 91° ambient temp during chrono was 48°

Originally Posted By: Cleric
Fresh brass or once fired?


2nd time I fired this brass from this gun. Brass is hornady

Thanks

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#6043055 - 11/22/15 09:49 AM Re: Shooting 300 win mag at elevation. [Re: fast88]
Wader Offline
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Registered: 12/02/09
Posts: 688
Loc: Krum, TX
Freshly loaded or loaded back in the summer? If it has been sitting a while it could be a slight cold weld between the bullet and the case. I wouldn't think a couple of months or few degrees would make that much difference, but if there is anything that shoot has taught me - it is that the unexpected is the norm.

-ww
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#6043817 - 11/22/15 05:27 PM Re: Shooting 300 win mag at elevation. [Re: Wader]
fast88 Online   content
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Registered: 10/13/13
Posts: 533
Loc: Smithville TX
Originally Posted By: Wader
Freshly loaded or loaded back in the summer? If it has been sitting a while it could be a slight cold weld between the bullet and the case. I wouldn't think a couple of months or few degrees would make that much difference, but if there is anything that shoot has taught me - it is that the unexpected is the norm.

-ww


Ammo was loaded about 1 month prior.

thanks

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#6044081 - 11/22/15 07:34 PM Re: Shooting 300 win mag at elevation. [Re: fast88]
FiremanJG Offline
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Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
Second time fired. Was the brass sized with a .002" bump on the shoulders?

Did every piece of brass show a light extractor mark or some pieces of brass?
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#6044571 - 11/23/15 06:18 AM Re: Shooting 300 win mag at elevation. [Re: fast88]
fast88 Online   content
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Registered: 10/13/13
Posts: 533
Loc: Smithville TX
The brass trimmed with a giraud and was sized with a full length RCBS die. I didnt do anything different than I normally would.

All brass had the extractor marks. They where very faint and hard to see or I would show a picture


Edited by fast88 (11/23/15 08:16 AM)

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#6044761 - 11/23/15 08:29 AM Re: Shooting 300 win mag at elevation. [Re: fast88]
DStroud Offline
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Registered: 11/02/11
Posts: 1156
Loc: Waco
Could be as simple as a little lube on cases or they were so light you did not notice first go round.
Did you clean the gun after the first range session? Change lot number on bullets?

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#6044804 - 11/23/15 08:54 AM Re: Shooting 300 win mag at elevation. [Re: fast88]
FiremanJG Offline
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Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
Originally Posted By: fast88
The brass trimmed with a giraud and was sized with a full length RCBS die. I didnt do anything different than I normally would.

All brass had the extractor marks. They where very faint and hard to see or I would show a picture


Sized how much?

In any case, all my short actions will have an extractor mark on some of the brass in a box of 50. Last week my 7 Rem Mag with 71.2 of Retumbo under a 180 VLD showed an extractor mark after seven rounds. I attributed it to getting the rifle a bit hot. It was 65F and I had worked up that load in 100F three years ago.

In short, I personally don't fret over light extractor marks, they seem to be more of the norm for me than the exception. Everyone has their own safety margin, though.
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#6054389 - 11/28/15 10:36 AM Re: Shooting 300 win mag at elevation. [Re: fast88]
jeffbird Online   content


Registered: 03/09/09
Posts: 1717
Originally Posted By: fast88
So this year for my hunting rifle I decided to load up 210 vlds. At my home elevation around 600 feet and my load of 79.5 grains of Retumbo with the bullet seated to the lands produced a 1/2 in group at 300 yards with no signs of pressure. I didnt chrono it because I hunt at an elevation of 3000-4400 so I wanted to get the correct velocity at the ranch. I chronoed there today and was suprised at the velocity 2997 avg and ES of 21 over 15 shots but they are now showing a light extractor mark on the brass but no flattened primers. Is a pressure increase common at elevation changes?


Originally Posted By: FiremanJG

In short, I personally don't fret over light extractor marks, they seem to be more of the norm for me than the exception. Everyone has their own safety margin, though.



Reading your description, check the COAL. The loads might be slightly compressed. After sitting on the shelf, the pressure of the compression can cause the bullets can slip out in length, thus resulting in the bullet jamming in the lands and driving up pressure. In any event, elevation does not change muzzle velocity, only temperature would. The velocity is 150 fps too high, which is another measure of excessive pressure. Check COAL and back it off a bit. If compression is an issue, H1000 works well with the 210's and fills it a bit less.



I usually agree with FJG, but this time, I have to disagree, and strongly so.

These are red flags. Pay attention and heed the warning signs.

Everything will be fine - until it isn't.

The gun is unlikely to blow up, but case failure is the most likely risk.

When there is a case failure, your eyes are at risk at a minimum.

I was running a small match, and witnessed this case failure when a friend was shooting.

Gas and powder particles blew back in his face.

Thankfully, I made everyone wear eye protection despite all of their moaning and groaning. Now, no one argues.





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#6054464 - 11/28/15 11:31 AM Re: Shooting 300 win mag at elevation. [Re: jeffbird]
FiremanJG Offline
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Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
Like I said, everyone has their own margin of safety.

Seems I work up loads looking for consistency. If a group has an extractor mark on each piece of brass then I do not use that powder charge. But take a load that had no extractor marks during load development, shot tight, and had a low ES. Reproduce said load 50-100 times and there seems to always be at least some that had an extractor mark. I noticed, Thursday morning 100 pieces of 7 Rem Mag that had been fired twice. About 7 pieces had an extractor mark on them. It seems to happen with every rifle I load for, and most are not loaded to max charge.
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#6054481 - 11/28/15 11:41 AM Re: Shooting 300 win mag at elevation. [Re: fast88]
jeffbird Online   content


Registered: 03/09/09
Posts: 1717
FJG,

If you are seeing extractor marks, that is a warning sign of excessive pressure.

Also, seeing the extractor marks is a reflection of pressure on that part, which increases the likelihood of the extractor sticking sooner or later. Having the extractor hang up is another reason to avoid it.

Loading books and data are just rough guidelines. The thing they are helpful on is showing the max velocities. How much powder it takes to get there will vary rifle to rifle.

Most "match" rifles are cut with tighter chambers and better quality barrels, which ofter are tighter over their length. Thus, at least in my experience, tend to hit the pressure limit well before a "hunting" rifle in the same chamber.

As an example, a R700 in 308 shooting 175 SMK's can typically take 45 grains of Varget to reach 2600 - 2650, while a "match" rifle will hit the same speed with 43.5 - 44.0.

Anyway, sooner or later, a primer pocket will have a gas leak or the case will let go at the web as above.

It just is not worth pushing for the extra bit of velocity.

Make sure to wear some sort of glasses to guard against the gas leak.

In the original post, 3000 fps with 210's in a 300 WM is an objective measure that pressure is too high. 210's should top out around 2850 +/- fps in 24 - 26 barrel. The velocity alone is a warning sign.


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#6054610 - 11/28/15 01:05 PM Re: Shooting 300 win mag at elevation. [Re: jeffbird]
FiremanJG Offline
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Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
I'm not disagreeing with you. I know you know your stuff!

I'm saying, for me, a light extractor mark is an early sign. During load development I note if there was an extractor mark and/ or sticky bolt lift. And I've developed loads that did not have extractor marks, ran with them, then ocassionally see an extractor mark on brass for hundreds of rounds later. Same brass that has been annealed, same powder lot, same bullet seated to the same relationship to the lands. I've suspected brass with a .002" bump showed an ocassional extractor mark, but did not show a mark when virgin.

Months ago I was helping a friend test loads on a .338 LM shooting 300 gr. Bergers atop +/- 90 gr of Retumbo. As we worked up from minimum, about 3/4 of the way, we got an extractor swipe. Each progressively hotter charge had a more pronounced swipe. I actually said we need to quit before we shot the two hottest loads. Lemme tell you, I had safety glasses on, but sitting behind a bolt holding 90 gr. of Retumbo and a 300 gr. Berger will make you wonder if the bolt lugs are gonna hold. sick

I should've taken pics of that .338 LM brass to share here. It was quite obvious when thr charge got hotter the extractor swipe got deeper into the brass.
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#6054691 - 11/28/15 01:53 PM Re: Shooting 300 win mag at elevation. [Re: FiremanJG]
jeffbird Online   content


Registered: 03/09/09
Posts: 1717
Originally Posted By: FiremanJG
sitting behind a bolt holding 90 gr. of Retumbo and a 300 gr. Berger will make you wonder if the bolt lugs are gonna hold.


up

338LM, 7WSM, and a 308.



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