Effect of C.O.A.L. on Bullet strike?

Always learning from you good folks here, I developed a load for my .223 Re. using 50 Gn. ZMax bullets; 26.0 Gn. Varget, Norma brass and Remington 7 1/2 BR primers.Around .25" at 100 yards, 2.200" COAL. So I loaded a small amount using that COAL; also a few at 2.2150" and a few at 2.220".

The 2.2200 COAL not only tightened the group to .1795" today's session (only 3 round group- don't get too excited) at 100 yards, BUT it apparently lowered the point of impact from approx. 1.5" high at 100 yards to almost exactly 1".

Curious mind wants to know; Why?

My thought train (which might be way off the track) is that since the case is VERY full at 26.0 Gn Varget, bumping the COAL out lessened the pressure somewhat- thus reducing velocity somewhat?

What say you who have knowledge in this area?

I don't know what the freebore of my gun is. I suspect it's relatively long; it's approx. 1992 vintage OEM Savage bull barrell 26". It's one HECK of an accurate gun but, as MANY of us do, I'm trying to get all I can in the accuracy / consistency arena.

Thanks so much for your insights.

Brian

I've been shooting once or twice a week for the past 18 months, and reloading just as long, which by no means makes me anything more than a novice. Having made my disclaimer, I am happy to add to the conversation nevertheless.

I shoot the Vmax and Zmax in 223 and I find the Zmax varies in wt by several tenths of a gram wereas the Vmax is very consistent. If you not sorting your Zmax by weight, that might explain what your seeing. Otherwise, your "test" was shot on different trips to the range and that by itself could explain the difference.
IMO Varget is a bit slooooooow for 50 gr. Your bullet is probably getting a good sized kick in the butt as it leaves the barrel due to unburnt powder (exit blast). Hard to argue about that group though, as long as it's consistent, that's worth crowing about (see what I did there…LOL)

I'd shoot 10 each 5 round groups before being satisfied it's a keeper load.

I use 3031, 8208XBR or Tac for my 50 to 55 grain loads. N-133 is also a good one to try if you can find it.

Save the Varget for heavier loads. IIRC it was made for the 308.

Almost forgot to answer your question about seating depth. I tried varying seating depth in 40 thou increments. I saw lowering POI as I got deeper into the case until I hit 120 thou deeper, then group hit much higher. Must have crossed that magic threshold where pressure increased, probably due to changed packing density of propellant.

Indeed, it is rocket science.

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Originally Posted by Texas10

I've been shooting once or twice a week for the past 18 months, and reloading just as long, which by no means makes me anything more than a novice. Having made my disclaimer, I am happy to add to the conversation nevertheless.

I shoot the Vmax and Zmax in 223 and I find the Zmax varies in wt by several tenths of a gram wereas the Vmax is very consistent. If you not sorting your Zmax by weight, that might explain what your seeing. Otherwise, your "test" was shot on different trips to the range and that by itself could explain the difference.
IMO Varget is a bit slooooooow for 50 gr. Your bullet is probably getting a good sized kick in the butt as it leaves the barrel due to unburnt powder (exit blast). Hard to argue about that group though, as long as it's consistent, that's worth crowing about (see what I did there…LOL)

I'd shoot 10 each 5 round groups before being satisfied it's a keeper load.

I use 3031, 8208XBR or Tac for my 50 to 55 grain loads. N-133 is also a good one to try if you can find it.

Save the Varget for heavier loads. IIRC it was made for the 308.

Almost forgot to answer your question about seating depth. I tried varying seating depth in 40 thou increments. I saw lowering POI as I got deeper into the case until I hit 120 thou deeper, then group hit much higher. Must have crossed that magic threshold where pressure increased, probably due to changed packing density of propellant.

Indeed, it is rocket science.

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Hi Texas10: Thanks for your response. Lots of "views" but lack of responses always leaves me wondering why not a lot of opinions...

BTW- I'm always 'crowing' about something LOL.

Don't know the main reason I usually shoot only 3 except that my gun only holds 4 rounds (blind mag, etc)- I do shoot 4 often; three rounds lets me "see" center of group if there is a spread; If I have shots outside the group I know which shot it was-determine if I blew it and finally here in Pa. where you can use centerfire cartridges, you can only load three. NOW- when I finally get a hunt out west for prairie dogs or ground chucks I'l probably wish I did do some 5 and ten round strings. I do shoot relatively fast, though- try to keep it as "real world" as possible.

I will do some 4 round shot strings to verify the Varget load.

RE: Varget- my thinking was that it's the powder that I have the most of and it is slightly faster than the burn rate of Winchester 748 which I've had terrific results using. However, W748 is a ball powder and is reportedly very temperature sensitive. I guess I figured since it burned slightly faster that the 748 it might be good.

I DO use it in my .308 and so far behind Hornady 155 Gn AMax and 130 Gn. Speer HP it is phenomenally accurate and consistent!

THANKS again for your comments- I'll do an update next week when I can get out to "verify" loads.

Brian

Don't worry about the others, I'm sure they'll chime in here soon. Probably just getting ready for contest season.

Have you used a gage to check your distance to lands with whatever bullet you might be loading? If the throat is eroded in your barrel, you might be a loooong way off the lands and what you do about seating depth is more likely to effect velocity/barrel timing than bullet engravement into the lands. Just my opinion.

My barrel is barely out of warranty and has 4000+ rounds down the tube. The throat is eroded to the point that this week as I checked the distance to lands on a new Berger 73 gn BTHP match bullet I was working up a load for, and at optimal seating depth (bullet heel at the neck/shoulder junction) I was still .170 off the lands. If I tried to seat it on the lands, it'd be out of the case neck entirely.

Shot it today at 200 yds in windy conditions and two loads 1/3 grain apart and just under max grouped under 1 moa. Not a bad start.

I was loading with IMR4320 but plan to try some 8208XBR in the near future. That works really well with 69gn SMK's in my 9 twist.

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Originally Posted by Texas10

Don't worry about the others, I'm sure they'll chime in here soon. Probably just getting ready for contest season.

Have you used a gage to check your distance to lands with whatever bullet you might be loading? If the throat is eroded in your barrel, you might be a loooong way off the lands and what you do about seating depth is more likely to effect velocity/barrel timing than bullet engravement into the lands. Just my opinion.

My barrel is barely out of warranty and has 4000+ rounds down the tube. The throat is eroded to the point that this week as I checked the distance to lands on a new Berger 73 gn BTHP match bullet I was working up a load for, and at optimal seating depth (bullet heel at the neck/shoulder junction) I was still .170 off the lands. If I tried to seat it on the lands, it'd be out of the case neck entirely.

Shot it today at 200 yds in windy conditions and two loads 1/3 grain apart and just under max grouped under 1 moa. Not a bad start.

I was loading with IMR4320 but plan to try some 8208XBR in the near future. That works really well with 69gn SMK's in my 9 twist.

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I'm not worried about the others- more worried I've asked a really dumb question. Compared to a lot of you guys I'm still a rookie!

I do not have that piece of equipment. The gun is older- early 90s as I recall the research here on this forum when I first got it. I tried to do the "slit-the-case-insert -the bullet" thing and got numbers that were pretty unbelievable- so I guess I'll be buying a proper Hornady gauge or similar soon.

I was told my gun's barrel more than likely had a long throat- not necessarily a bad thing. I intend to contact a smith in my area and ask him to bore scope it. IF it's eroded I'll probably shoot it until it really falls off (accuracy-not the barrel LOL) then decide to either get a new barrel or a new gun. It's kinda funky having a long action 223, but I've put so much time into it and the stock, replacing small parts etc. I am pretty attached to it. It weighs a ton but again, shoots well!

I usually start C.O.A.L at book spec- 2.200" +/- and have had VERY good results. When I switched brass, the same loads did not shoot as well, and I weighed cases primed, weighed again with water and adjusted charge weights. I got good grouping with the above load and when loading to confirm I bumped the COAL out as documented. ALL the groups fired were good- but the one out to 2.2200" was best.

4000 rounds! You are doing some serious shooting my friend! Great shooting at 200!

Brian

Where you able to identify your gun by it's serial number? If not, maybe you can post some pics of it. Someone here might be able to give you some valuable information as to what exactly you have there.

You did not ask a dumb question, Brian. In reloading, there's a lot of science, a bit of magic, and many instances of Whiskey Tango Foxtrot? I've been reloading for over 50 years, and am still occasionally surprised during the load development process. When you think of all the variables: powder type, lot number, and amount; bullet weight, length and seating depth; barrel length, twist and stiffness; primer type; shell casing; neck tension; altitude; barometric pressure; ambient temperature; and finally, but not the least of the issues, the kind of day the shooter is having; all these and more play into what we experience in the field and at the range. Control the things that you can during the reloading process, and then, when you want to change something, change only ONE thing at a time. Don't change COL and primer; primer and powder charge or type. One thing at a time, and take copious notes. While doing all this will not necessarily answer your specific question of why strange things happen, it will allow you to capture all the variable and then learn from them so you can repeat those "pet" loads.

Maybe i can answer your question and if not i can sure muddy the waters a bit. Whey you change seating depth you CAN change the pressure developed but unless you go from a large jump to a hard jam it will most likely not be a dangerous thing. It is possible to raise pressure by compressing the load also but unless you are starting with a compressed load i would doubt that with a 50gr lead core bullet you will have enough bullet in the case to worry about (darrker may have trace to show on seating and pressure relationship). When you reach out there to 300 yards plus you will find the seating depth will have more affect on your horizontal than your vertical. Point of impact is irrelevant as long as groups are tight.

+1 to Earl39.

UncleNick posted the chart which has Dr. Brownell's work on seating depth, found here:
https://www.shootersforum.com/handlo...-pressure.html

I do have several traces showing different seating depths with the same charge, in a Creedmoor. Just as with the chart, the difference is more of a subtlety.

My 308(Painless) is north of 4500 rounds fired to date. I have no doubt that the throat is eroded some. But since I didn't do a chamber cast when new, I can't accurately tell you how much. What I can tell you is that I can hold very fine accuracy to a mile still. Will I win the inter-galactic accuracy trophy? Heavens no, but it fits what I want to do with it, so I'm happy.

I honestly didn't read through this whole thread, but other than what Earl stated, here is a generality on pressure/depth.
Seating closer to the lands will raise operating pressures on the system, there is less gas by-pass around the bullet and there is a "studder" when the bullet engages the rifling without much momentum.
Seating the bullet deeper can raise the case pressure early-on, but that gas very quickly by-passes the bullet prior to land engagement; also the bullet has a much higher velocity when it does engage and will transition much smoother; thus lower system pressures.

Much of this is academic, and not terribly practical however. Every powder(same name, new lot) has different burning rates, and many have different burning curves. From our testing, the more progressive burning powders are less sensitive to seating depth, in terms of system pressure. It appears that the altering burning curve will compensate to a degree, whereas the old-tech traditional curves do not.
Again, this gets complicated by application. Just as "extreme" powders are NOT a universal thing, they application specific; so are the progressive burning powders. They do not burn and respond the same in every cartridge. Varget in particular is quite sensitive in the 223 with 50-55gr bullets, that does not mean you cannot find very fine accuracy only that some older ball powders do better in that application with regards to temperature.

Wow... thanks all! I'd be lying if I said I understood all of what you are saying- particularly the more scientific info, but it does give me a jumping off point and certainly expands areas to study and learn. Darkker I took a look at the curve chart but admittedly cannot relate it to whats going on in my specific case.

I should know better than to think there are absolutely absolutes in anything with this many variables. I tried and am trying loads with Varget because I have a quantity and I thought Varget was less pressure sensitive than my usual W748 in this caliber. I understand now (at least I think I do) that while Varget was developed as a less temp sensitive powder, it is not always-dependent on application and components used.

Because of the lack of controls I have, including no power over atmospheric conditions, I may be chasing the wind (no pun intended) by slightly altering the things I do in pursuit of tighter groups.

Earl39- I agree that point of impact is irrelevant if groups remain tight. I was and still am baffled tht my group ith the 2.2200" COAL shot tighter and noticeably lower than the other two groups as they were shot on the same target, within a fw minutes of each other.

ANOTHER point I had not considered is that the rnge I shoot at is slightly uphill- the more so as you get out to 100 then 200 yards (our range's maximum). Too, I'm not shooting from a "sled" and although I make every effort to replicate hold, trigger control, cheek weld, etc from shot to shot and group to group, I'm certain I'm not consistent enough to rule out better or worse technique (human error and fluctuation) from group to group.

Thanks for the info- I love to learn and to be challenged to learn and try to understand the things that, in my opinion, make reloading and shooting so much fun / enjoyable.

PS- Darkker- I've got to know what a .308 painless is? The other caliber I load for is .308 Win. Is this a reference between that and say, .338 Lapua...or...?

Brian

Varget was designed to be stable for ball ammo in the 308, isn't as awesome in the 223; especially compared to 748. 748 was the LOOOOONG time benchrest go-to in that case. 26.6gr behind a 55gr bullet held an awful lot of trophies.
Painless is simply the name of my rifle, it is chambered in 308.
This is Painless
http://i78.photobucket.com/albums/j8...psmsmefwpi.jpg

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Originally Posted by darkker

Varget was designed to be stable for ball ammo in the 308, isn't as awesome in the 223; especially compared to 748. 748 was the LOOOOONG time benchrest go-to in that case. 26.6gr behind a 55gr bullet held an awful lot of trophies.
Painless is simply the name of my rifle, it is chambered in 308.
This is Painless
http://i78.photobucket.com/albums/j8...psmsmefwpi.jpg

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COOL looking gun you've got there! Could I trouble to ask for the details / specs? Looks like the same safety thats on my 110 .223...is it an older gun? The safety on my Hog Hunter in .308 is newer / wider tear-drop shaped safety. What kind of stock, scope, bbl length...all th juicy details please! I'm sure you've articulated this before but I didn't see it...

Thanks! Brian

It's a standard factory 3-screw 10fp, sitting in a Ultimate Sniper. So 24" pipe. Bases& rings are some no-name crap I took on a trade, with about 15MOA worth of Aluminum foil as a shim. Weaver tactical 3-15(800363).
Currently has a few hundred rounds over 5,000 shots fired.
Painless has killed almost every legal animal in the Lower 48, been lugging it around since about '97.
The only jewelry on it is the Tacticalworks bolt handle. Saw something shiny and hung it on it, no other reason for it really.

Thanks for the info!

My 110 LA .223 has the 3 screw trigger, also. Weird having a long action 223 but it shoots well and I'm attached to it!

Thanks for all the info and insight!

Brian

"Painless" looks like a tried and true friend. Sweet gun.