Seating VLD bullets to mag length

[oaken]

Right, this weeks possibly daft question…………… why does the velocity drop by nearly 100fps when

seating a VLD bullet back into the case, deep enough to clear the internal magazine of my .223?

I use a fairly mild accuracy load for the 80gr VLDs so I figured that I could just push the

bullet back in the case without fear of pressure.

I know this is generally not done, but not sure why. Could it be because in order to gain

clearance I had to shorten the oal by 140thou resulting in some of the bullet projecting inside

the body of the brass? Incidentally, the resulting accuracy was significantly bad.

Is it worth persevering with some load development to find a load/length that feeds thriugh the mag

or should I continue treating it like a target rifle and stick with feeding single shots?

Rup

[duey]

having pushed the bullet back off the lands you are probably reducing the pressure rather than increasing it as the act of the bullet against the lands has a greater pressure effect than that of pushing the bullet into the case

VLD bullets also are not great generally with a jump to the lands hence the drop off in accuracy

you could try seating a bit further back in order to try and find a sweet spot again, may need to be as much as 50 thou but obviously be aware at all times of pressure and do it in small steps of 5 thou each time and you may have to adjust powder charge accordingly

 

if possible fire each round over a chrono and see how your velocity compares to that of your original accurate round

 

good luck

[Guest richness]

I' ve found sometimes pressure goes up just as much shortening a round as it does whacking it into the lands. This "the further you get towards the rifling the higher the pressure" is nonsense IME; i'm not saying it is untrue, i'm just saying it is not a directly proportional thing. either way, you've changed your load significantly and it will not shoot the same as before by any means.

Therefore in your case, my thoughts would be that if you change the length AT ALL, you need to go back to the range and test the sweet spot for seating and powder both. I personally doubt you'll be too impressed with the VLDs that far out and might advise you toward one of the flat base designs that are better further out or perhaps 75gr amax?

ATVB Richard

[oaken]

Thanks for the advice. I did not really expect accuracy without some load dev, I just didn't expect it to be that bad! Similarly with velocity, not what I expected.

I had the rifle rebarrelled with the intention of using the 75 Amax but I couldn't get them to shoot....... I tried them long, short, fast and slow and with 3 different powders....... then I tried the VLD and had almost instant success. I think the Amax responds well (or better) by being driven faster than .223 can go, without putting it on the limit.

Been doing some reading and it looks as though the pressure generated when the powder goes off is distributed over a larger area, ie the extra surface created by the bullet poking back in the case is enough togenerate higher pressure but lower velocity, sounds far fetched but vaguely possible. The brass showed no signs of pressure.

I am going to stick with single feed.