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Discussion Starter #1 (Edited by Moderator)
I replaced my factory barrel on my .223 RPR with a 1"8 twist 24" stainless barrel from Criterion. Have been reading web posts from folks who shoot the 77s with Varget and RL15. Many claim great groups with 24g of either powder. Have not put that may rounds through my new barrel and am getting tuned in to the best for my set-up. With my limited groups to average I now have a Varget powder charge and am working on the jump both sides of .015. In fact will be at the range tomorrow to give these a try.
Would like to hear from the Forum members, what your experience has been and/or any suggestions. Not asking for specific loads.
Have not found a lot of info from bolt gun folks but tons from the AR club.
Thanks.
How do you change the font size? Can hardly read the small type.
 

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The Shadow (Super Mod)
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Many claim great groups with 24g of either powder....

Would like to hear from the Forum members, what your experience has been and/or any suggestions. Not asking for specific loads.
Seems strange that you list a specific load, then ask for none specific.

I've had a few 9 twists that would happily shoot the SMK's, because they aren't very long. I used 748, but load data came from Hornady and Sierra.

Let us know how you like it.

Cheers
 

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Discussion Starter #3
Sorry Mike. Guess I have lost the knack of writing what is on my mind and expressing it clearly.
 

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I'm shooting a 26 in Criterion 8 twist in 223 in a Savage bolt gun. Although you mention working both sides of .015 off, you also imply you're loading to magazine length. That makes it harder to use high B.C. bullets that have a longer profile and get them close to the lands.

In my barrel I found a great load using the 69 gr lapua, however the longest OAL I could get, and therefore more case volume, was .010 into the lands. Any shorter and seating depth became unstable as the powder was pushing the bullet back out of the case. So I dropped the charge back down .9 gr and got a more reliable load. But then I switched to H335, a ball powder and got back the velocity AND the OAL I needed. More than one way to skin a cat.

The 73 Berger loads very long in the case due to it's more tapered cross section. I get plenty of room and find 25 gr Varget a good load.

The 80 gr A-Max also loads well, with room for 25 gr + of Varget.

But all of these are single load rounds. I don't shoot out of a magazine so I'm not constrained by OAL limitations.
 

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I shoot the 77 SMK and the 75 Hornady. Both over 24 gtains of RL15 in new primed Winchester factory
brass.
 

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I tried both Varget and H335. I had to switch to magnum primers with H335 but the results were much better than Varget. I don't shoot heavy bullets, just 55 grain but if you find the groups larger than you want you might give H335 and magnum primers a try.
 

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45LCRRIFLE,

Using font tags only makes your post's text different, and you already know what is in your post, so that doesn't help you much. Everyone else's posts will still be the same, so you'll still have trouble reading it.

For viewing, in Windows, just hold down the control key while you tap the + sign on the number pad, or hold down the control and shift key while you tap on the regular keyboard + sign at the end of the number row. This will make all text on the screen larger. To go back, just hold the control key down and tap the hyphen or the minus sign on the number pad.

CTRL and + for bigger
CTRL and - for smaller

There is nothing magic about 0.015" jump any more than there is with 0.020" jump or was with 0.025" jump or 0.030" jump, all of which have been claimed to be the best jump at one time or another. The reason for so many different "ideal" jump numbers is different guns and bullets like different jumps in different chamberings. If you read Berger's article on setting jump with VLDs, you'll find some bullets like to be 0.125" of the lands or more, while others want to be jammed into the lands.

In the 1995 Precision Shooting Reloading Guide, one of the authors described loading a 220 swift to 0.020" off the lands and never averaging better than 0.5" at 100-yard 5-shot groups (not adequate to a benchrest competitor). Then one day he changed to a bullet 0.015" longer and turned his micrometer-adjusted seating die the wrong way, so instead of keeping the jump at 0.020" he had increased it to 0.050" and had 20 rounds loaded before he noticed the error. When he shot those 20 rounds in 5-shot groups, to his astonishment, he got two 0.25 moa groups and two true bugholes in the 1's.

Note that jamming into the lands isn't magic either. People mention the associated pressure increase as if it happens suddenly right at contact, and any amount of jump short of that doesn't exhibit it. This is wrong. For conventional Spitzer bullet nose shapes, it is typically the case that the pressure increase happens between about 0.030" off the lands to contact. It actually increases fastest between about 0.030" and 0.010" and increases more gradually up to contact from there. At contact, the rise is about 20% in the peak pressure. That means you want to knock the starting load down about 10% from regular data and work up to the starting load as your maximum for land jamming. At 0.015" off the lands, you probably want to take the minimum and maximum down about 5%. None of that ultimately governs what your particular rifle might tolerate—your bore and chamber dimensions do that—but it's about right for starting expectations.

For other bullet shapes, the pressure change with jump is different. VLD's move back more than common Spitzers. Round nose bullets have to move really far back to cause the difference. Here's a plot from Dr. Lloyd Brownells 1965 study showing pressure change for a round nose, which needed to be back for a full 0.25" of jump before the pressure minimum. Seating deeper then started to raise pressure again due to taking up powder space in the case.

 

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