CHANGING OAL, SAME POWDER WEIGHT

[gemini1]

When I first chrono'ed a 62 grain FMJ lead core with 24.6 grain load of H335, the COAL was between 2.247 - 2.255".
The data I got was - AV 2889, ES 93.62 and SD 29.24 While the other load was 24.8 grains and the AV was 2939, ES 87.84 and SD 22.04

Using Hodgdon's online data, I followed the 63 grain info

63 GR. SIE SP H335 .224" 2.200" 22.5 2820 41,000 CUP 25.0 3051

I did get some good groupings on the 10 shot test. The other load was 24.8 grains, but the groupings were terrible.

So I've made new batches for re-testing. Same 24.6 gr weight loaded on an 1.750" LC09 brass, Tula SRP.
But this time, I made a batch with diff COAL 2.217-2.219", 2.235-2.240" and a batch with the original oal of 2.250-2.256"

The idea or what I'm trying to accomplish is to get the same or better groupings while maybe increasing the velocity a bit for seating the bullet a little deeper.
My one concern is the type of bullet used on the online data, SIE SP vs my FMJBT lead core

What do you guys think, good idea or bad?
Oh and here's another question. If the Hodgdon load data has a max velocity of 3051 at 25.0 grains, it doesn't say what barrel length was used, but I assume its 20"
Since I have a 16" barrel which as some say losses about 150 fps over a 20"
Can I safely get the same max velocity as the 20" if I load over the max? Assuming I watch out for any pressure signs, can the rifle handle the stress?

[Dark Mod]

You can certainly do it, but I would never advise anyone too. Everyone knows their own skill level and can assess the risks of exceeding max load accordingly. I wil say I've never cared about velocity in rifle. That is to say, I've never tried to squeeze out a few hundred fps, i prefer consistent velocity.

Consistancy is key for me in rifle cartridges, that usually means longer OAL, and slightly below max load. Yeah you can make some hot rifle rounds, but if they are all over the place at 100 yards what's the point?

Ill make nuclear loads all the time in handgun cartridges, the variation is never really all that noticeable at 15 yards. This hobby is kind of about doing what you want however, so don't think Im pressuring you to not experiment. If your gonna exceed max published data, go slow and watch for signs like anything else. You'll get more consistent results from increasing the charge than lowering the seating depth.

[thenodnarb]

I always try and increase COAL to the max my magazine or chamber can handle. The less the bullet has to jump before it hits the lands, the more accuracy you will get (generally). Although some advise to make sure the bullet doesn't actually touch the lands because it can lead to an increase in pressure, which is a problem if you are already at max published data.
FWIW, I've experienced better accuracy from slower loads, but it depends a lot on the barrel, twist rate, and bullet shape.
I assume you are going for accuracy, but at what distance? If you are really trying to max distance, then velocity may come into play at the extreme distances(due to the bullet going transonic and beginning to tumble or otherwise become unstable).
IF however, you are only interested in shooting to 100, 200, or 300 yards max, I would instead focus on experimenting with different powders at lower velocities. In my rifle, I have much more accuracy from BLC-2 than I do with Varget, all else being equal.
Bullet weight compared to twist rate and length of barrel is important too. My barrel is a 1 in 7" twist, and I don't feel I get good accuracy from mid weight bullets. I feel they are spinning too fast, exaggerating any inconsistency in concentricity. Instead I have more luck with 69 and 75 gr HPBT.
If you are only loading for one rifle, I would encourage you to only neck size as well, as this can lead to better alignment within the chamber, getting the bullet started off right.
So overall I say experiment with other powders and different velocities first. More speed doesn't necessarily equal more accuracy. Decide what you want the load to be able to do, and tailor it to that.

[ar15barrels]

FMJ bullets usually are not real accurate so most efforts to get better accuracy are limited by the quality of the bullets themselves.
If your end goal is improved accuracy, you would do better to use some better quality bullets than to fiddle with seating length.

[gemini1]

AH, thanks for your input guys. One of the other reason I thought of doing this, was because of the recommended OAL (2.200"), I figured if I got good groupings with the longer OAL, why not try making it less and see if it changes anything?

[mark501w]

Generally getting closer to the lands & grooves helps accuracy. I set my magazine guns to the longest length that will function reliably. Pressure is pressure & increasing pressure doesn't necessarily give you higher velocity the idea is to get high velocity with low pressure. With auto loading rifles you don't have as much leeway as a bolt gun. Look for loading data that has pressure info & this may give you some idea to go with your weight of bullet. A carbine is just that a short barreled rifle & a lower velocity gun.

[Whiterabbit]

Generally getting closer to the lands & grooves helps accuracy.

I read this a lot, but not in my experience. Maybe this is some sort of SMK and berger thing? or whatever people tend to shoot the most, anyways. none of the bullets I shoot will improve being closer to the lands. There's a very specific pattern to most of my rifles actually:

seated ON the lands is accurate. Great load. as I pull back, the accuracy drops off. Then I hit another node, and it's pretty far away from the lands. .05 to .1". and it's WAY more accurate than ON the lands.

So none of my loads are anywhere near the lands.

Maybe that would change if I shot popular bullets?

[mark501w]

Every gun is a rule unto itself.