100fps
- Thread starter sako2
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stagpanther
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I guess because of the smaller cross section and lighter weight of the 257 compared to 264 maybe I'm getting different burn characteristics, AA4350 and IMR 4955 did markedly better in my rifle than ram magnum and retumbo. The suggestion of staball is an an interesting one--I've wondered about it before (and I have plenty of it).
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Pathfinder45
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What barrel length are we talking about?
stagpanther
New member
From the sounds of it--you have lost velocity consistently across all powders you've tried, no? When you start from a clean bore, do you see big deviations in velocities until they stabilize? You said I think your groups are generally tight, right? I have experienced drop-offs in velocities a few times when increasing the charge weight, I think it generally was with incremental compressed loads though it might have been an error on my part in loading. In my 25PRC bore I was seeing lots of residue down my bore when using the extra-slow burning powders, pure conjecture on my part, but I figured I was possibly getting an inadvertent early start on the bullet and then an uneven "finish" on the combustion of the powder column.
Typically I do find variations in neck tensions between manufacturers so I don't think that's all that unusual.
Typically I do find variations in neck tensions between manufacturers so I don't think that's all that unusual.
Yes Stag it does shoot very good. The 10 shots yesterday where in a hole I could cover with a quarter. Very happy with the way it shoots. I have 3000 rounds down the tube. I wish i could find some imr enduron powder to try. The 5 shots of 7828 had a es of 18 and sd of 8. Rl26 gave me a es of 9 and a sd of 3.
stagpanther
New member
3000 is a lot for a PRC, I'll be happy if mine makes it to a 1200 and still shoots as well as yours does!
IMR 4955 is an enduron powder.
IMR 4955 is an enduron powder.Both QuickLOAD and GRT estimate the volume difference alone will account for about 25-26 fps of velocity loss and that half a grain of powder would make up for it. With a drop of 100 fps, something else about the case is affecting what is happening. It could be, for example, a difference in neck wall thickness or yield point (different manufacturers use different brass alloys), letting pressure open the neck a little faster so you get more gas bypass around the bullet before it arrives at the throat. One way to address this is to seat the bullet out a little further if you have room to do that.
The other thing to be concerned about is an actual drop in velocity with load increment, so I would back the charge down a little just to make sure you haven't landed in one of those drops. Velocity drop can be a high-pressure sign because it can indicate the chamber is stretching or the brass is flowing at the pressure you are reaching.
The other thing to be concerned about is an actual drop in velocity with load increment, so I would back the charge down a little just to make sure you haven't landed in one of those drops. Velocity drop can be a high-pressure sign because it can indicate the chamber is stretching or the brass is flowing at the pressure you are reaching.
You changed to a different case that has different properties and you got a different result shooting them. Why is that a surprise?
Someone else doing exactly the same thing even using the next ser# rifle off the production line could have different results.
Usually not much different, but the potential for significant differences always exists.
Sometimes, you can alter the measurable MV simply holding the gun slightly differently.
With all the possible variations of all the huge number of factors involved, the amazing thing to me, is that guns work as consistently as they do...
Always remember that your exact situation could be in the middle OR at either end of the bell curve probability range.
Someone else doing exactly the same thing even using the next ser# rifle off the production line could have different results.
Usually not much different, but the potential for significant differences always exists.
Sometimes, you can alter the measurable MV simply holding the gun slightly differently.
With all the possible variations of all the huge number of factors involved, the amazing thing to me, is that guns work as consistently as they do...
Always remember that your exact situation could be in the middle OR at either end of the bell curve probability range.
Pathfinder45
New member
Since I'm not familiar with the 6.5 PRC, I'm wondering about the difference in case volume between it and 6.5-06 or even 270 Winchester. I'm suspecting you didn't use nearly enough H-4831 or IMR- 7828 in your testing, but again, not being familiar, I can't be certain.
We all know that accuracy is a lot more important than velocity; we just don't believe it in our hearts.
We all know that accuracy is a lot more important than velocity; we just don't believe it in our hearts.
stagpanther
New member
Sako--just out of immense curiosity I decided to experiment with LRT since Hogdon does list it for some of the bigger 6.5PRC bullets. The closest I could come to a "weight class" bullet was a 135 gr hybrid in the 25PRC. I used 63.7 grs which is well under the suggested max for a larger 6.5 bullet. Even at that lower charge I was getting slightly flattened primers. This was just a "quickie shot in the dark" off the hood of my truck at 107 yds (I'm limited to close range for now due to construction activity) but I have to admit I'm very surprised it shoots as well as it does--it's compared to being close to retumbo but I never got anything close to this with retumbo. Sorry, I didn't set up the labradar.
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stagpanther
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Don't mean to offend, but considering your barrel is about at twice the normal "accuracy life expectancy" I wouldn't think twice about a slight drop in velocity if it still lasers them in.
Pathfinder45
New member
Indeed. After further research, I'm thinking that should be easily outrunning my 270 Winchester, yet the opposite is true. Nevertheless, I expect your rifle is easier to get stellar accuracy with. There are powders that can deliver the velocity for you, but if you can't get them you'll just have to make do. Can you get Norma MRP?
stagpanther
New member
I thought by definition anything 6.5 was man-bun? Or is that exclusively reserved for creedmoor?
I know on this forum we have the world's foremost expert on the man-bun, maybe he could clarify. I think I get your meaning, if you're going to sacrifice barrel life, should be in the cause of markedly better velocities then something very close that isn't a blast furnace. My 25 PRC barrel is about the hottest burning cartridge I've ever shot. In about 3 shots the barrel is very hot to the touch, even when spacing the shots out 3 or more minutes apart.
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I'm beginning to think all the data and stuff you read on forums about the velocities others are getting is B.S. Only load I have that comes close is rl26. I didn't loose anything when I went ADG cases to Hornady. Guess that's what throw me for a loop. For a factory Savage rifle it's very accurate and fun shooting. Hope to shoot it over a 1000 yds some day. I got some lapua brass to try.
stagpanther
New member
Savage makes high value rifles for their price points, but there's a pretty good reason why there's a thriving after-market for savage pre-fit barrels. I've bought lots of savage rifles but never have gotten the kinda of service life you have, particularly for a hot cartridge, especially for a conventional chrome moly barrel. My savage 6.5-284 and 300 win mag had great accuracy while they lasted, which wasn't very long considering the typical bench shooting load testing I do. I don't think I made it to 1,000 shots with either of them before the barrels were shot out.I still marvel that you made it to 3,000 and it still shoots accurately with the kind of shooting you do.
jetinteriorguy
New member
Hey, I don’t mind my 6.5CM being the man-bun, but I will never consider my beautiful old Swedish Mauser a man-bun cartridge.I thought by definition anything 6.5 was man-bun? Or is that exclusively reserved for creedmoor?