imr4895 and 308

peterk123

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Time to move on to loading up some 308s. This is another new cartridge for me. I have loaded up approximately 50 rounds or so of various grains using 4895. I started at 42 and have gone as high as 44.5. Starting loads according to Hodgdon is 42.7. Have you guys tried loading below that, say 40 or 41 grains?

The loads I have shot so far have all been fairly accurate at 100 yards. Not sure if 100 yards is a good litmus test, but its all I got. Other than grouping should I be striving for certain velocities when working up rifle loads, or pistol for that matter?

Thanks

Pete
 

hv55maxx

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I've learned when asking specific questions here, you need to give specific details. what bullet brand, weight, OAL, primer, etc. also, YMMV from gun to gun. even the same model, two different items may like different loads. that the beauty and curse of rifle reloading.

general rule of thumb, if you go below minimum, you risk a squib. if you go above maximum, you risk a kablooey.

also, load data from Hodgdon may say one min and max, then the Hornady manual might say another of the same powder. and the Sierra manual may say something different. load data can be brand specific and should be (compare a Sierra 165gr vs a Barnes 165gr TTSX, one eats more case volume than the other.)
 

peterk123

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Hornady 165 grain SST. Tikka t3x Bolt action. I am getting 1 MOA with my 42.5 grains at 100 yards. Just curious if I back off the loads what will happen. I recently purchased a chrono but have not had a chance to really use it yet. That is one of the reasons I am asking the questions because I want to understand how to use the chrono as a tool, not just a novelty :)
 
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Lots of uses for a chrono. For building a load, I try to find an accuracy node that also has a very low standard deviation (I consider any S.D. under 10 to be good).

As long as you're not going below the published minimum, you should be fine to try going lower to find that node. How did you settle on 42.5?

Have you measured how far off the lands your COL is?
 
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peterk123

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Lots of uses for a chrono. For building a load, I try to find an accuracy node that also has a very low standard deviation (I consider any S.D. under 10 to be good).

As long as you're not going below the published minimum, you should be fine to try going lower to find that node. How did you settle on 42.5?

Have you measured how far off the lands your COL is?
I loaded up five rounds in .3 grain increments. So far, that worked 42.5 provided the tightest group. Not a huge difference between the loads, but it was the best. Not a lot of shots through the gun so I want to start from scratch when it gets a bit warmer out, also using the chrono.

By standard deviation, are you referring to consistent fps? That would seem to make a lot of sense. The other thing I was thinking of is to find the range where the amount of powder used can vary by .2 or .3 grains and really not have a measurable impact as far as accuracy. That would seem to make sense to me as well.
 

hv55maxx

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ive had groupings open up from 1moa to 3moa with a 0.3grain charge difference. again, YMMV

my personal take has two qualifications. first and foremost does it group well? if yes, should i explore a higher charge to get more velocity? a 30.06 load i worked up, i had two identical groupings. one was on the low end of the chart and one was closer to max. i chose the higher charge as it would give more impact energy for hunting applications and also 30.06 isn't rare, so i can replace the brass easily and cheaply.

the chrono is great to know your drops and find the low SD (think consistancy), so even if drops don't come into play at all, it can help give useful data to make a decision on a good load for you. (with my 458 socom load, the velocity is extremely useful to know when the brick being lobbed re-zeroes [ i have a zero at 25yds, and 100yds basically]).
 
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Sounds like you're on the right track. The Chrono really helped me when I started using it.

If you're trying to squeeze all accuracy possible, then you can start getting into COL, shoulder bump measurements, jump to lands....on and on and on...
 

jpm

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general rule of thumb, if you go below minimum, you risk a squib. if you go above maximum, you risk a kablooey.
NO NO NO!! That rule of thumb is completely wrong.

If you go below minimum you risk explosion just like going above maximum! Too little powder can go off like a grenade because there's still a huge amount of pressure with no place to go if its not enough to push the bullet down and out of the barrel. It has to get relieved somehow which means the case will most likely burst since that's going to be the weakest spot in the equation. And then whatever is the weakest part of the rifle around that area is also going to burst and so on. Don't screw with low powder charges unless the manufacturer publishes reduced loads like for H4895 which is NOT the same as I4895.
 

EddieCoyle

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Doing ladder tests or testing for OCW, you're likely to find several accuracy nodes. With everything being equal, you're better off with the highest velocity loads (flatter trajectory, less time in flight, less time to be affected by wind, etc).

It's not like you're an octogenarian shooting cast bullets from a century-old milsurp. You're shooting a modern bolt action rifle in a medium to light recoiling caliber, why would you want to down-load?

Like Stape said above, you're going to see that seating depth will have more of an impact on group size than super-fine tuning the powder charge anyway.
 

PatMcD

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NO NO NO!! That rule of thumb is completely wrong.

If you go below minimum you risk explosion just like going above maximum! Too little powder can go off like a grenade because there's still a huge amount of pressure with no place to go if its not enough to push the bullet down and out of the barrel. It has to get relieved somehow which means the case will most likely burst since that's going to be the weakest spot in the equation. And then whatever is the weakest part of the rifle around that area is also going to burst and so on. Don't screw with low powder charges unless the manufacturer publishes reduced loads like for H4895 which is NOT the same as I4895.
What?
 

RKG

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To be sure, IMR 4895 has been a classic propellant for .308 Win/7.65 NATO. That said, I have found superb results with Varget, IMR 4064, Win 748 and Reloder 15, with the last edging out the others by a small margin. Slug is 168 grain SMK, lit by CCI LP. My go to load for the bolt gun is 42.2 grains of Reloder 15; for the M14, 42.2 grains of Win 748 (simply because I can throw the 748 consistently with a powder measure, while I trickle up the R-15 for the bolt gun). I don't shoot at 100 yards (300 and 500), but the bolt gun (scoped) is consistently < 1 MOA, while the M14 (iron sights) varies between 1 and 2 MOA depending on how good the shooter is on the day in question.

I happen to think that, for the bolt gun, you will find that fine tuning group sizes will be dominated by experimenting with bullet jump rather than by small increments of powder charge. My bolt gun has a tight chamber, and I found its sweet spot to be 15 thou jump (which translates, for this particular rifle) to a COAL of 2.791". For the M14, COAL is held to the book spec of 2.800" for other reasons.

Both loads have been chrono'd. From memory, velocity (at 15' instrument) was around 2,600-2,650 fps.
 

PatMcD

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Here's one thread that gets into it. There's more out there. Loading density/ secondary explosion - Shooters Forum
It reads like "I've heard of this happening somewhere, at some point, under very specific conditions, but it has never been duplicated in a lab setting".

Bottom line, you're never going to blow up a rifle by shooting a light load in a .308 (assuming some fool doesn't use a pistol powder by mistake).
 

hv55maxx

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NO NO NO!! That rule of thumb is completely wrong.

If you go below minimum you risk explosion just like going above maximum! Too little powder can go off like a grenade because there's still a huge amount of pressure with no place to go if its not enough to push the bullet down and out of the barrel. It has to get relieved somehow which means the case will most likely burst since that's going to be the weakest spot in the equation. And then whatever is the weakest part of the rifle around that area is also going to burst and so on. Don't screw with low powder charges unless the manufacturer publishes reduced loads like for H4895 which is NOT the same as I4895.
jim bob may have had an issue somewhere sometime with something, but can you, by high empty case volume theory, explain subsonic 308 loads (some ~10grains of unique for example)?
 

EddieCoyle

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jim bob may have had an issue somewhere sometime with something, but can you, by high empty case volume theory, explain subsonic 308 loads (some ~10grains of unique for example)?
From what I can deduce, "detonation" has happened, but only in very specific circumstances:
  1. Very light loads (like less than half the minimum)
  2. Of very slow burning powders
  3. In large cases
Unique is too fast, and a .308 case might be too small.

One theory behind "detonation" is that with a normal charge of slow burning powder (in other words, a case that is >85% full of powder), the primer explodes, the powder charge burns progressively from back to front, and the bullet is out of the case and moving down the barrel (increasing the volume of space behind it) before the powder is fully engulfed. Peak pressure happens after the bullet leaves the case. If the charge is reduced by half, the primer blast is able to flash over all of the powder laying flat in the case, igniting it all at once, with peak pressure happening instantly with the bullet still in the case.

However it happens, nobody has been able to reliably duplicate it in testing.
 

hv55maxx

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From what I can deduce, "detonation" has happened, but only in very specific circumstances:
  1. Very light loads (like less than half the minimum)
  2. Of very slow burning powders
  3. In large cases
Unique is too fast, and a .308 case might be too small.

One theory behind "detonation" is that with a normal charge of slow burning powder (in other words, a case that is >85% full of powder), the primer explodes, the powder charge burns progressively from back to front, and the bullet is out of the case and moving down the barrel (increasing the volume of space behind it) before the powder is fully engulfed. Peak pressure happens after the bullet leaves the case. If the charge is reduced by half, the primer blast is able to flash over all of the powder laying flat in the case, igniting it all at once, with peak pressure happening instantly with the bullet still in the case.

However it happens, nobody has been able to reliably duplicate it in testing.

I'll never question your reloading knowledge. That said, the point I was making was that it may have happened, but it's not like it's an everyday occurrence.
 
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If your getting MOA already using the OCW method can help find a good powder charge.
In brief the OCW method is to find a powder charge range that delivers good solid groups with in a powder charge window. So even if you have a .3 or .5 powder change difference the “load” is going to still hit POI with in a small margin.

Now if you looking for reduced loads H4895 does very well here. Tou can find the instruction on Hodgdons web site.
I run some real powder puff 110-125 grain 308 and 3006 loads with both jacketed and cast bullets with H4895 and orher powders.

As for velocity... well you can neat yourself up crony testing. I personally wasted to much time crony testing.
Now if I Was shooting long range and loosing a round or 2 into the 9-8 ring vs Xs I might get a little deeper into why.

Consistent reloading practice will get you consistent results. I only have the Shooting Crony so relying on that for consistent accurate results in itself is sketchy.

It took me a little while for it all to come together
When skills, equipment and reloading methods all came together I started surprising myself on how I could get nice small groups.....getting them to the X ring ? Well thats another challenge.
 
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I started loading 308 around '94. Never had great results barely able to crack 1 MOA. I used all those old powders 3031, 4064 and 4895. Fast forward to 2015 and Varget. I wanted to give it a new try and see what the rifle would do. Using Varget and new LC brass and Hornady comparator/headspace gauges I'm now down to about .625" 5 shots @ 100yds. Not to bad I would say.
 

45collector

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Bottlenecked case reloading is still new to me, and I started doing it with .308 just last year for my CMP Special Grade Garand and FAL. The goal was to find a load that worked equally well in both rifles. I settled on 150gr jacketed with 43gr of H4895, in mixed brass. Literally any boxer primed .308/7.62 brass without regard to maker or headstamps. Now I read somewhere that it may not be wise to do this based on different case wall thicknesses and other factors, But other gleaned info told me for what I’m loading this caliber to,velocity-wise, it should be fine to mix brass. I have had zero issues so far, and groups are acceptable to me at 100 to 200 yards.
I don’t shoot rifle nearly as much as I do pistol, so I’m not too concerned with match-winning accuracy. Just something to shoot at the local yokel military rifle matches and have a chance to be in the top three. ;)
 
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Bottlenecked case reloading is still new to me, and I started doing it with .308 just last year for my CMP Special Grade Garand and FAL. The goal was to find a load that worked equally well in both rifles. I settled on 150gr jacketed with 43gr of H4895, in mixed brass. Literally any boxer primed .308/7.62 brass without regard to maker or headstamps. Now I read somewhere that it may not be wise to do this based on different case wall thicknesses and other factors, But other gleaned info told me for what I’m loading this caliber to,velocity-wise, it should be fine to mix brass. I have had zero issues so far, and groups are acceptable to me at 100 to 200 yards.
I don’t shoot rifle nearly as much as I do pistol, so I’m not too concerned with match-winning accuracy. Just something to shoot at the local yokel military rifle matches and have a chance to be in the top three. ;)
43 grains H4895 in NATO is a warm load per QL: not knowing your H20 case capacity its hard to say . I cant recall where I read it, maybe snipers forum or something but 762 NATO averages about 8% less capacity than commercial offerings.? I personally have not seen this much of a swing with my brass I have on hand. Rule of thumb I was told was 2 grains less from 308 loads when going to NATO case ?

heres a "generic" load from quick loads for 7,62 NATO with a 150gn Sierra FMJ with your 43 gn of H4895
1581774443054.png

now heres the same data but with 308 win sammi as the cartridge input
1581774596308.png

Dont know how well it shows but the info shows 308 win at a usable case case capacity(space available with bullet seated) of 50.22 VS 762NATO at 46.21 which is around 7% ish
so all things equal case resize/trim length/powder charge/bullet seating depth there is close to 8k psi swing between the 2 different cases.

Now I tried my best to weigh H20 between several cases and have yet to see a difference beyond 2.5 grains with the brass I have. Rem,ppu, various NATO cases.

one thing to note though is if you have some unexplained flyers you might want to sort by case manufacture and shoot them in lots.
 
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Wow yeah, 8k psi is definitely not a minor bump huh?
pm your load data and I can run your specific info
Bullet, seating depth , case trim length . Do your best to check H2O volume?
I tried using 98% isopropyl just to compare capacity between cases. It seemed easier to fill the cases and less air bubbles getting trapped at the shoulder? Its useless as far as data goes but it does show the differences .
 

gerrycaruso

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I've tried several powders including 4895 but I've gotten the best accuracy with reloader 15. The rifle is an M1A and it's been driving me crazy. They're not known for stellar accuracy.
 

PatMcD

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I've tried several powders including 4895 but I've gotten the best accuracy with reloader 15. The rifle is an M1A and it's been driving me crazy. They're not known for stellar accuracy.
Everybody expects then to shoot 1/2 MOA, but they just aren't capable of it. A match-tuned M14 done up by an armorer who knows what he's doing is a 1MOA rifle. That's 10 groups of 10 shots each. Not a single 5 shot group, which is what everybody puts out there as an example.
I got the best groups from mine with 45 grains of W748.
 

45collector

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pm your load data and I can run your specific info
Bullet, seating depth , case trim length . Do your best to check H2O volume?
I tried using 98% isopropyl just to compare capacity between cases. It seemed easier to fill the cases and less air bubbles getting trapped at the shoulder? Its useless as far as data goes but it does show the differences .
I think I’ll just bump the load down to 42 grains for any NATO brass from here on out.
 
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