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338 Edge high velocity?

 
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  #1  
Old 03-06-2009, 09:22 AM
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338 Edge high velocity?

I chrono'd my new Edge recently with 300 GR SMK's and 93.0 gr of H-1000 which it shoots better than the 92.0 grain load. No pressure signs at all, even the primers are not beginning to flatten one bit.

Chrono readings were 2898-2911 consistently with 3 shot groups. This is out of a 30" barrel.

Is this unheard of? I think my chrono is OK. It indicates my 300 Win with 210 Bergers and 75.7 gr of H-1000 is around 2880 and my AR-15 with 60 gr NBT's is 2780-2800. An AR-10 with 150's is 2720-ish. I've put 55 gr NBT's out of a 22-250 over it at 34-3500 fps too.

I was expecting 2800 or so based on what I have read.

Thanks.
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  #2  
Old 03-06-2009, 09:42 AM
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Re: 338 Edge high velocity?

What is your overall length? I don't get that velocity, but mine are pretty long to get close to the lands on my rifle. Generally, the longer a cartridge is, the slower it will be with the same amount of powder. Conversely, if it is short, the faster (and higher pressure) the load will be.

What kind of Chono do you have? Your readings seem a bit high.

AJ
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Old 03-06-2009, 12:58 PM
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Re: 338 Edge high velocity?

OAL is 3.910" at 0.010" off the lands.
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Old 03-06-2009, 08:22 PM
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Re: 338 Edge high velocity?

if the primers aren't even beginning to flatten, you might have another 50 fps to go with normal pressure. 2950 sounds pretty fast to me. i'd try another chrono.
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  #5  
Old 03-07-2009, 12:43 AM
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Re: 338 Edge high velocity?

Depends on the barrel.....I have built a few that run the normal 2850 out of a 30" barrel, and quite a few that run 2890-2920 out of a 30" barrel using the same charge and OAL. We run ours at 3.81" OAL, 93 gr H1000 and they both shoot 2930 for a 10 shot string. We have verified velocity and drop out to 1800yds while shooting with Shawn Carlock last summer.
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Old 03-07-2009, 10:12 AM
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Re: 338 Edge high velocity?

I have seen the same chrono read as much as 100 fps high on certain lighting conditions. The most accurate lighting conditions are overcast dull days with just enought light to make the chrono work. Bright light days always run faster and moving cloud days can give variable readings. If it still reads this high, shoot it at distance say 800-1000 yards to see what the drop is, this will positivily tell you if your chrono is lying to you.
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  #7  
Old 03-07-2009, 03:53 PM
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Re: 338 Edge high velocity?

I would say average accuracy loads in the rifles I have built have run around 2850-2875 fps with a 30" barrel. This got to the point that I just loaded a certain load for accuracy testing and never varied from that load as it was so consistant and that was right at 2850 fps.

That said, I have seen some rifles produce 2950 fps without any noticable pressure signs but remember one thing, there are some fast barrels out there but on average, velocity is a simple function of pressure and time. Pressure behind the bullet and the time the bullet is in the bore accelerating.

Some barrels will get X fps with varying amounts of powder but on average, they will still be generating very similiar chamber pressures even if the powder charges used to get the same velocity are very different.

A quality built rifle will show fewer obvious pressure signs then a conventional rifle. A rifle that has been accurized and has a min spec chamber will show very little if any pressure signs.

I one made a 257 STW for a customer and he was told he could get 4100 fps with a 100 gr TSX bullet out of his 28" barrel. This information WAS NOT offered by me.

He got to 3900 fps and noticed that a few cases were getting some gas smudges around the primer but did not think much of it as he was not overly experienced. Loaded up to 4000 fps and when he would eject a fired case, the primer would fall out of the case.

He was very upset and asked me why his rifle was doing this at such low pressures and velocities...... I asked him why he thought he was loading to low pressure and velocity when he was a full 150 to 175 fps over what he should have been loading to.

He replied that he could open the bolt with one finger on these loads and there was only a very faint ejector mark on the case head and that his primers even looked pretty round.

When the receivers are perfectly square, the bolt lugs are 100 % contact and the chamebr is set up tight, not allowing that primer to back out before powder ignition starts, you will get very little sign of high pressure and you can go from what appears to be a perfectly comfortable load to loosing primer pockets in just a grain or two of powder.

Best indicator I have found for pressure prediction, a known quality chronograph and monitoring your cases primer pocket tightness. If your getting 3-4 firings per case before the primer pockets loosen noticably, your pressures are max but usible. If your pockets are loosening with less firings to this, your pushing things to hard.

Now if this could be dangerous or not will depend on what receiver you have. In a custom receiver with larger bolt lugs and more steel behind the bolt lugs, you really not pushing things hard at all but you are running the risk of combining that high pressure with a case that may have a flaw in the case head. If the case head fails you will have a serious problem, if you just get gas blowby around your primer, you will get minor gas cutting on the bolt face but no real damage to the rifle.

If your usig a Rem 700, I would say load to 2850 fps and be happy with that, especially if your primer pockets are loosening with fewer then three firings on the case.
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