8208 the sweetest thing

[Nimrod]

Yes, I am still using the mag primer, but would be interested in what others are using.

[GregP42]

I am also using 8208 in my Grendel loads, the load I am using that was fine last time was not today, last time temp was 60, today it was right at 90 on the firing line. I have brass that has nice shiny spots on it from the ejector, and the brass went a little farther than last time. So I don't agree that it is temperature insensitive. I am going to drop back .5gr and see what happens. Also I could tell from point of impact change that it was running harder.

Greg

[terrywick4]

I am also using 8208 in my Grendel loads, the load I am using that was fine last time was not today, last time temp was 60, today it was right at 90 on the firing line. I have brass that has nice shiny spots on it from the ejector, and the brass went a little farther than last time. So I don't agree that it is temperature insensitive. I am going to drop back .5gr and see what happens. Also I could tell from point of impact change that it was running harder.

Greg

How big of an impact change did you see?

[GregP42]

How big of an impact change did you see?

Terry,

I had a change of over 1.5 inches with the 8208 loads. I went back out this evening where it has cooled down and tried it and it was right back to where it should have been. But then I mounted my new brake and had to adjust the scope for it.

Greg

[Hoot]

Terry,

I had a change of over 1.5 inches with the 8208 loads. I went back out this evening where it has cooled down and tried it and it was right back to where it should have been. But then I mounted my new brake and had to adjust the scope for it.

Greg

This is important, albeit disappointing news. Greg, how close were you loaded to max with those. actually, what was the exact load specifics, including COL? Might give us a glimpse into the mechanics of it. We're you into the lands? I don't know about anyone else, but more than once, I've had a lightly compressed, max load go punk with a significant temperature shift upward, that didn't jump as quickly, when it was loaded a step or two below max. Not sure why. I assumed something related to the being into the compressed zone. Might be totally irrelevant to your situation though. Perhaps, s your results imply, 8208 is no better than spherical powders in terms of temperature stability. That's not what IMR implied, but I'll take field reports to sales hype. Really got to hit the hay. 04:30 comes early and Friday's can be hectic at work.

Hoot

[davidj]

I am also using 8208 in my Grendel loads, the load I am using that was fine last time was not today, last time temp was 60, today it was right at 90 on the firing line. I have brass that has nice shiny spots on it from the ejector, and the brass went a little farther than last time. So I don't agree that it is temperature insensitive. I am going to drop back .5gr and see what happens. Also I could tell from point of impact change that it was running harder.

Greg

It sounds like the Hodgdon family needs to re-think this interview.

http://bulletin.accurateshooter.com/2010/01/shot-show-report-hodgdon-talks-about-imr-8208-xbr/

[GregP42]

This is important, albeit disappointing news. Greg, how close were you loaded to max with those. actually, what was the exact load specifics, including COL? Might give us a glimpse into the mechanics of it. We're you into the lands? I don't know about anyone else, but more than once, I've had a lightly compressed, max load go punk with a significant temperature shift upward, that didn't jump as quickly, when it was loaded a step or two below max. Not sure why. I assumed something related to the being into the compressed zone. Might be totally irrelevant to your situation though. Perhaps, s your results imply, 8208 is no better than spherical powders in terms of temperature stability. That's not what IMR implied, but I'll take field reports to sales hype. Really got to hit the hay. 04:30 comes early and Friday's can be hectic at work.

Hoot

Hoot,

Yes it was a near max load, IMI brass, 27.8gr 8208, 120 Sierra HPBT, Federal 215M primmer, COL 2.190. Like I said I shot it again the other night when it was cool and everything was fine. I am going to reduce the load by .5gr and see how it does on a hot day again, weather this next week here is only supposed to get into the mid 60's so it will have to wait till it warms back up.

Greg

[LR1955]

Hoot,

Yes it was a near max load, IMI brass, 27.8gr 8208, 120 Sierra HPBT, Federal 215M primmer, COL 2.190. Like I said I shot it again the other night when it was cool and everything was fine. I am going to reduce the load by .5gr and see how it does on a hot day again, weather this next week here is only supposed to get into the mid 60's so it will have to wait till it warms back up.

Greg

Greg:

You used a compressed load of fast powder in reformed 7.62 X 39 brass with a magnum primer, shot it in 90 degree weather (God knows how hot the cartridges were if they sat in the sun), and you think the powder is more temperature sensitive than advertised? He, he, he.

8208 SBR is on par with a fast 4895. No matter how you cut it, the IMI brass is thick 7.62 X 39 brass and thus has quite a bit less case capacity than the standard Grendel cartridge. I figure to get the same issues with the Grendel brass you would have over 30 grains of 8208 XBR which isn't something I would do with a fast burning rifle powder and a AR-15.

The large rifle primer issue does play a role too as that part of the brass is weaker compared to brass using small rifle primers. Add that to the 10% less internal volume of the IMI brass and you will get into dangerous ground real fast. The magnum primers may or may not add some pressure too. I am not positive and I have used 215M primers with IMI brass and chronographed loads to compare primers.

So, what happened is that you pushed the brass pretty seriously and under those circumstances I bet a ammo temperature change of thirty degrees would show the results.

LR1955

[GregP42]

Greg:

You used a compressed load of fast powder in reformed 7.62 X 39 brass with a magnum primer, shot it in 90 degree weather (God knows how hot the cartridges were if they sat in the sun), and you think the powder is more temperature sensitive than advertised? He, he, he.

8208 SBR is on par with a fast 4895. No matter how you cut it, the IMI brass is thick 7.62 X 39 brass and thus has quite a bit less case capacity than the standard Grendel cartridge. I figure to get the same issues with the Grendel brass you would have over 30 grains of 8208 XBR which isn't something I would do with a fast burning rifle powder and a AR-15.

The large rifle primer issue does play a role too as that part of the brass is weaker compared to brass using small rifle primers. Add that to the 10% less internal volume of the IMI brass and you will get into dangerous ground real fast. The magnum primers may or may not add some pressure too. I am not positive and I have used 215M primers with IMI brass and chronographed loads to compare primers.

So, what happened is that you pushed the brass pretty seriously and under those circumstances I bet a ammo temperature change of thirty degrees would show the results.

LR1955

LR,

I thought about the less case volume, but it is only about 5cc less that the factory Hornady brass I have. I might have not figured it out right, but from the data I got from Hodgdon for using a 120gr Sierra HPBT match I am almost a full grain below max. I did not let the rounds sit in the sun, I learned that a long time ago. I try to keep my ammo in the AC for as long as I can. As for the mag primers, I was told to use them due to the regular primers having the possibility of a slam fire. I am going to switch to military primers to solve that issue. That load is just lightly compressed as it does not come up to the bottom of the neck in my cases.

Is all IMI brass equal? I had not heard the 10% less figure before, but I will get out my pipette and measure the capacity of both again. Best as I can remember right now it was 31gr water for the IMI and 36gr for the Hornady brass.

I was hoping that 8208 was not temperature sensitive like they had said it was. I know I have to drop a full grain on IMR4064 in my .220 swift in the summer vs the winter. But this is a new powder to me as well as a new round.

Greg

[LR1955]

LR,

I thought about the less case volume, but it is only about 5cc less that the factory Hornady brass I have. I might have not figured it out right, but from the data I got from Hodgdon for using a 120gr Sierra HPBT match I am almost a full grain below max. I did not let the rounds sit in the sun, I learned that a long time ago. I try to keep my ammo in the AC for as long as I can. As for the mag primers, I was told to use them due to the regular primers having the possibility of a slam fire. I am going to switch to military primers to solve that issue. That load is just lightly compressed as it does not come up to the bottom of the neck in my cases.

Is all IMI brass equal? I had not heard the 10% less figure before, but I will get out my pipette and measure the capacity of both again. Best as I can remember right now it was 31gr water for the IMI and 36gr for the Hornady brass.

I was hoping that 8208 was not temperature sensitive like they had said it was. I know I have to drop a full grain on IMR4064 in my .220 swift in the summer vs the winter. But this is a new powder to me as well as a new round.

Greg

Greg:

That 5cc is a huge amount when talking about the Grendel design. Most guys think 28 grains of TAC maxes out the IMI brass with a 120 and I agree.

I think you are trying to extrapolate or interpolate load data from real Grendel brass to IMI 7.62 X 39 brass. Or you are interpolating when using powder burn rate charts. If so, I advise you to seriously reconsider these techniques when using (very specifically) the Grendel. Many of us have found that the Grendel is not predictable when it comes to powders and pressures as a .308 for example. The Grendel is far less forgiving and no one has produced tested data using 7.62 X 39 brass. It will give you much higher pressures than Grendel brass and the pressure increases are not linear -- that much I will bet on. And they aren't proportional to loads that use Grendel brass. That much I will also bet on.

I believe you started out with a pretty stiff overload that was on the edge and a 30 degree change in powder temperature was enough.

LR1955

[GregP42]

LR,

I did make one mistake when I quoted my load, it is 26.8 not 27.8. I am new to this platform totally and I look to you guys to keep me straight I have to make my own data from what I get from the powder companies for two other rifles I have, a 6mmx284 and a 6.5mmx284, I use Winchester 284 brass for both of them. I keep saying I am going to get a strain gauge setup http://www.shootingsoftware.com/pressure.htm but I do thank you for the help you are giving me.

Greg

[street medic]

max load

just wondering -- the guys at sierra told me 28.5 max load for 120 hpbt out of 24 in barrel. still working up 27.5 last - not bad seemed like i would always have one flyer in the group. by the way what primers are you using

I have played with multiple different powders, almost had settled on 2520, but have had awesome results with 8208. I have fired 130gr Accubonds, 120gr Ballistic Tips, and 123gr Amax bullets with it. What is really cool is that I am getting almost identical points of imp
act with all three bullets. I can't post pics at the moment, computer crashed.

Rifle - Les Baer 20" barrel.

120gr Ballistic Tips
28.5gr
Average velocity - 2531 fps.
5 shot groups under .5"

123 Amax
28.5gr
Average velocity - 2524 fps
5 shot groups under .5"

130 gr Accubonds
27.5gr
Average velocity - 2387fps
5 shot groups .75"

I am getting better groups with 8208 than I was with 2520 and I really haven't had to sacrifice any of the velocity that you get with 2520. I am buying 8 pounds and sticking with it now.

[Nimrod]

The loads I posted are what I would consider max. I use CCI 450 primer.

You said the guys a sierra gave you a recommendation on a max, what department did you call to get that info, I never thought of calling the bullet manufactor to get info like that and would like to know who to call.

[CoolBarrelBill]

The loads I posted are what I would consider max. I use CCI 450 primer.

You said the guys a sierra gave you a recommendation on a max, what department did you call to get that info, I never thought of calling the bullet manufactor to get info like that and would like to know who to call.

Sierra has a "Ballistics hot line" you can call to get reloading info. I have called them many times they have always been helpfull.

http://www.sierrabullets.com/index.cfm?section=techservice&page=ballistictech

[longdayjake]

Does anyone know why they don't make powders into ball or flakes with powders like Varget, 8205, R15, H4350, IMR4350 and similar powders? I'm guessing it has something to do with the manufacturing process required to make powders burn at that rate and temperature.

It changes burn rates.