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- เผยแพร่เมื่อ 11 ก.ย. 2024
- In the previous episode we measured bullet jump -the distance from a seated bullet to the rifle's lands- using the Hornady OAL gauge and bullet comparator kit. We loaded 4 five-shot groups at various jump distances. Now it is time to shoot this for group and see the effect of bullet jump.
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Consistent ignition is key. High load density aids consistent ignition. The deeper seated bullets increase load density.
I don’t worry about seating depth until I work a load well under a inch is achieved ie powder and projectile working well first seating depth is fine tuning
Excellent. Interesting. Helpful.
Thank you very much
I’m not seeing enough consistency to draw any conclusions. I’m thinking a retest is in order.
Mark and Sam Afterwork has demonstrated that less pressure and higher velocities can be had with 300 win mag with larger freebore, longer I mean, with certain slower burning powders.
nice video, looking forward for the next one, thanks !!!
Thanks for watching and posting Javier Glock Savage
It seems illogical to me, but I've seen repeatedly that seating a bullet deeper results in LOWER velocity
Yes, it is odd isn't it. Sometimes it works out just as expected in other times ---such as this case-- they fly counter to what we expect. Thanks for watching and posting.
Keep them coming
Roger that! We have another video coming out in a few weeks that I think you will also like.
I think going closer to the lands and re-tuning the powder charge would produced the smallest groups with low SD?
I am indeed thinking about running through another optimal charge weight test now that the improved bullet seating depth was identified. Sometimes I wonder just how good I can get these rounds with careful adjustments.
That would make a great video 👍
@@josephhomen I will try to get some video when I do this. Take care.
Great vid!!
Thank you Cory. Thanks for watching also.
Thanks for the video 👍
Thanks Joseph. And thank you for watching and posting.
The entire sled is jumping rearward and the rifle is not sliding straight back in the rest. I’d suggest you improve that rifle rest before shooting for groups. That no.1 should shoot under an 1 moa group but your getting 2+ moa groups. Something is definitely wrong.. but you can’t fine tune your reloads if the rifle is recoiling inconsistently.
Yeah, that is the problem at our local range. Some of the benches are topped with a very slick concrete making everything slide after each shot. The rifle did end up performing very well with a sub-MOA group. I am not sure if you watched all the results.
@@sdkweber - Yes, a 0.55 moa group is performing very well! Thanks for sharing your process and take care..
I was told that bullet length can vary per box, and that consistent seating using base to OGIVE measurement is the best way to go. However you have very high quality bullets, so they may all be very close to same length. However I’m thinking your expected lengths of a given Base to OGIVE measurement change didn’t always give you the same change in COAL because of a variance in bullet length or error in measurement with caliper?
Also, I was always told that the closer the bullet is seated to the land would create an increase “or pressure spike” at same charge load, and one must be careful to back off charge weight when going closer to the lands. I would also assume more pressure would equal higher velocity. However this wasn’t noted by your test was it? Maybe a longer time in the barrel to getting the bullet started earlier “longer jump” makes more efficient use of the powders burn time and by starting off with a more gentle starting off push-through, rather than a higher pressure slap start?
Hello Mike and thanks for watching. The general rules you noted are correct. Bullets can vary in length, weight, and diameter of meplat. A good quality bullet will vary so little that its effect is not detectable.
Bullets seated close to the lands are typically not a problem for pressure unless the bullet jams into the lands when chambered. There are some minor exceptions to this but overall as long as the bullet is not making contact with the lands we should not see a pressure spike (the exception would be a long bullet loaded hot).
I am finding there are always exceptions to the general rules and there are also tolerances to bullet seating etc that as long as we operate within those tolerances, our ammo will be precise and reliable.
@@sdkweber Thanks for taking the time to reply. Have a great weekend my friend. 😎👍
@@repairfreak You are welcome Mike. It is nice to discuss this kind of stuff with fellow shooters.
Dude! Adjust your scope windage!
Combined Over All Length?
Cartridge Overall Length
Both are correct. More recently the term Cartridge overall length is used, but years ago "combined" was quite common. The "combined" was the case + the seated bullet.
This rifle and cartridge combination is so inaccurate that you can proof absolut nothing with it. Not one thing. The last group is as big as the first. I dont get it.
Hi mate I Struggle to get consistent seating depth why is that
Could be a few things Darryn, first take careful measurements of your combined overall length, but measure it to the ogive of the bullet instead of to the meplat. That is a more important and meaningful measurement. Second, a bullet seating die like the Redding makes consistent bullet seating much easier. Last, don't sweat small differences of only 1 thousandths (0.001) as it does not seem to make a difference.
Oh, and I should also mention, before any of this, be sure you have your cases trimmed to the same length. I hope all this helps. Thanks for watching and posting.
I just tested my factory Rem. 223 with sierra 69gr. hpbt / 25gr. CFE223 with rounds from 10 to 35k off the O'Give every 5K and found my best 5 shot groups were with 20k + - off the O'Give
Hey DLN1234. Good to hear from you again. Your results help to validate my reasoning and similar results I am seeing. That is, its not jump that matters but barrel harmonics. Modifying the bullet seating depth and CBTO can show improved precision at certain points, but that is the point where we see a harmonic node for that barrel.
I saw the same results with my .308 RPR, my 6.5 Grendel, and most recently my sons .308 H&K rifle... and now your results.
Thanks for posting this.