Going from jump to jammed.

[AKGuide]

I was wondering how much to drop in charge weight going from 0.010" jump to 0.010" jammed. Trying to get 230 bergers to shoot and have never jammed bullets before. I tried searching to no avail. As of now I am running 95 grains of h50bmg for a muzzle velocity of 2988 in a 300 RUM. Thanks a bunch

Reuben

 

[dkhunt14]

I like to jam the VLD's but before I jammed that 230 I would load a few at 30 jump, 60 jump and 90 jump to see if you have any improvement. You only need 3 of each. If it doesn't shoot 3 small it isn't gonna shoot 5 small. I would back off a grain to jam just to be safe. Matt

 

[gohring3006]

If I was going to work up a load I would start a jammed and work up to find my charge weight, then work back jumping if you start with a jump and work with seating depth towards jamming you could get some high pressures whit the same charge weight..

 

[MR.SWIFT]

just for kicks try reloader33, you will be impressed.

 

[AKGuide]

Thanks for the help guys. I will back off a grain or two and try kissing and jamming. .010" off shot the best with .090" off a close second. I used bergers recommended seating test but didn't jam to start.

Reuben

 

[snowpro440]

Read bergers website...a lot of info there on seating depth and pressure.

 

[Bill Johnson]

Thanks for the help guys. I will back off a grain or two and try kissing and jamming. .010" off shot the best with .090" off a close second. I used bergers recommended seating test but didn't jam to start.

Reuben

Be aware that "jamming" a bullet into the lands has 2 negative consequences. One is that you could possibly end up pulling the bullet, leaving it "jammed" into the rifling if, for some reason, you didn't want to shoot the round (or had a FTF) and unless you have a lot of neck tension and a hard crimp, the bullet will only seat into the land a little before it starts setting back in the case, reducing case volume and raising pressures.

I'm a cautious person but risk management is part of my trade. I'd pick a seating depth, reduce loads 5% and work up.

 

[sundance1972]

Be aware that "jamming" a bullet into the lands has 2 negative consequences. One is that you could possibly end up pulling the bullet, leaving it "jammed" into the rifling if, for some reason, you didn't want to shoot the round (or had a FTF) and unless you have a lot of neck tension and a hard crimp, the bullet will only seat into the land a little before it starts setting back in the case, reducing case volume and raising pressures.

I'm a cautious person but risk management is part of my trade. I'd pick a seating depth, reduce loads 5% and work up.

Had the above happen with my 338-06AI while out hunting. Had a bullet pull out and wound up with powder all through the action. Stupidly left my cleaning kit back at camp and had to stand on the hood of my truck and use my radio antennae to knock the bullet out. Felt like a total moron, but learned a couple good lessons that day!!

I would work up a new load with the bullet jammed, making sure it will still fit the mag properly first.

 

[kcebcj]

If I was going to work up a load I would start a jammed and work up to find my charge weight, then work back jumping if you start with a jump and work with seating depth towards jamming you could get some high pressures whit the same charge weight..

The above statement is very accurate. It's best to start at the lands find the charge weight then work away. QuickLoad specifies a 5000psi increase in pressure when against the lands or jammed. Berger has a good setup to follow on its web site that you should give a try.

 

[AKGuide]

Well found my load, but pulled a shot today and opened my .25" start to a 2" group at 300 yards. It's funny at 100 yards they don't shoot all that great, but at range they did awesome. I had to drop my jumped load 2 grains to maintain my max load. 97 grains jumped and 95 grains jammed. Here's the load and group.

Blue Printed Rem 700 with 28" Pac-Nor .338" neck
Nosler Brass
Fed GM215M
94.0 grains H50BMG
230 Berger Hybrid Target seated to kiss lands

 

[Mikecr]

It's best to start at the lands find the charge weight then work away.

This is old school thinking that doesn't actually work with most cartridges.
Any optimum jam charge will be completely different than optimum jump charge.
Like AKguide found, 2gr difference.
So unless your development increments are huge, you would be relying on pure luck to find best charge -while moving from jam to jump, etc.
So with charge adjustments first, you have load development in the lands(ITL) and separate load development off the lands(OTL).

Better is to back off and perform full blown seating depth tests right up front(incremental from off to in to off), and with best seating chosen from this continue with more credible charge testing. This seating testing can be done while fire forming new brass.
Now if you've decided or know that you need to be jammed for your cartridge, then there is no reason to test otherwise.
You'll save a lot of tail chasing with this either way.