308 over pressure?

H

Holeshot

Sergeant
Full Member
Minuteman
Sep 4, 2013
94
0
Indiana
#1
2djh9s.jpg


bottom to top: unfired handload,fired hand load and a fired factory federal with a 168 SMK

Hi all I am trying to develop a load for 308/168gr mk's or nos custom comp. Shouldn't be too hard. Its a very common combination. I have IMR 4895 powder. That should be a no brainer go to powder.

Here is The offical IMR load data:



168 GR. SIE HPBT IMR 4895 .308" 2.800" 41.0gr 2447 39,700 PSI 45.4C 2758 58,000 PSI

I loaded up 50 rounds to exactly 43.6gr. Pan weighed and trickled every charge.

I am using federal cases, standard large rifle winchester primers, and 168gr nos CC bullets.

I am shooting a remington 700 SPS tactical with the stock 20" barrell with a 1 in 10 twist.

I think my load of 43.6 should be right in the middle of a safe range.

Unfortunately I do not own a chronograph at this time.

I fired 2 rounds out of the batch I made and upon inspecting the cases the primers look VERY flat and they even took on some of the texture of the bolt face.

I got out my lyman reloading manual and it says that 42.5 should be the MAX load with IMR4895

What gives? Do you guys think this is a serious over pressure sign?

Do you think I should pull them apart? If so why would the MANUFACTURE publish loads that are way too hot? Im confused.

Any input would be appreciated.
 
#2
I was just checking my notes and didn't have that combo loaded.
I did do a test on 178 AMAX for my Rem 700 5R with IMR 4895.
37.5 ~ 42.0 ... only the 42.0 started to flatten out a wee bit but not as much in the picture.
I mainly use Varget in all my load and shoot mostly 178's in my bolt gun and 168's in my gas guns.
The Varget load was much better on the pressure signs.
I know that doesn't help you much but that is what I have got.
Also I loaded much longer too.
 
#5
The load data is going to depend on the brass used. FC brass is heavier than Win or RP, so going to.have less internal volume, therefore higher peak pressures. If it were me, I would have started around 41grs thinking to arrive at 42.5grs at my target velocity. If you do not have a chronograph you are flying blind.
 
#6
Thanks for the replies. I guess ill order a new chrono. Im going to pull these apart to be on the safe side. I knew I would be "flying blind" as you say without a chronograph but I guess I just figured with a common rifle, common bullet, common powder and so on I could just pic a medium warm load and go from there. I also wish I would have just loaded a few to test instead of 50. Oh well lesson learned. I'm still confused as to the published IMR load. What if I had said the hell with it and loaded that max compression charge? Blown out primers? Blown up gun? Lost an eye or worse? Crazy.
 
#7
Did you say you used Winchester primers? Because the ones in your picture look silver and the Winchester primers are normally gold colored, but it could be the picture...

Anyways, I've had trouble with Winchester primers not handling pressures that other primers can. You can always try changing components and see if you get the same signs.

Ultimately, I would start with a ladder test from min to max+ instead of guessing at a load. That way you can see what your actual max pressure is. Some rifles are just hard on primers, so starting at min would show you what normal pressure looks like.

Sent from my SCH-I535 using Tapatalk
 
#10
308H335168gr.jpg


Hodgdon max book load:
308 WINCHESTER, CASE: WINCHESTER, BBL: 24", PR: FEDERAL 210M, 168 GR. SIE HPBT COL: 2.800" H335, 42.0 gr., 2631 fps, 49,300 CUP

From left to right:
1) 43 gr. 2% overload, ok
2) 44 gr. 5% overload, cratered primer this and higher
3) 45 gr. 7% overload
4) 46 gr. 10% overload
5) 47 gr. 12% overload
6) 48 gr. 14% overload, mark on brass from bolt face extractor this and higher,
7) 49 gr. , 17% overload
8) 50 gr. 19% overload, extractor cut on brass expands .0020"
9) 51 gr. 21% overload, extractor cut on brass expands .0020"
10) 52 gr. 24% overload, extractor cut on brass expands .0110", primer fell out,

You can see between 49 and 50 gr, something bad happens. The brass starts to yield. That will mean short brass life. The primer does not fall out until 52 gr.
That is why I like to measure the extractor groove before and after firing in a work up.
Then I subtract off a safety margin, and there is my max load.
If I later found that the threshold was at 49.5 gr., I would subtract off 6% safety for a ball powder => 46.5 gr would be my max load. Not 42 gr like the book said.
 
#11
Sierra load data shows 41.3 as max
Nosler load data shows 43.0 as max
Hornady load data shows 43.3 as max
Speer load data shows 44.0 as max

Load data for the M14/M1A
(reloader magazine May-June 1989)
168 Sierra MatchKing
IMR-4895, 40.5 grains 2,626 fps
IMR-4895, 39.0 grains 2,544 fps

You need more manuals to average your data and you need to start much lower and work up.

Quickload only shows 50593 psi with 56.0 of H2O case capacity and your load data of 43.6 grains of IMR-4895 and 46.1 as a max load at 60160 psi. All this shows how much load data can vary with different firearms and components used.

This is why it is important to start low and work up looking for signs of pressure, reading your primers and measuring case expansion at the base of the case. As you can see above there is over 4.1 grains difference between the Sierra data and the Hodgdon's data for max load.
 
#12
Thanks guys. This is all very good information. It changes my perspective on how I was previously thinking. I don't claim that I know a lot but this makes me question things. Maybe one variable that I never thought of is that I am using small base dies. Not for any reason other than that's what I have. Sounds like time to back up and research and learn a few more things. Again thanks for the good information everyone.
 
#14
On another note, consider that Hodgon uses Winchester cases which have 2grs more capacity than Federal. That explains their higher max.

Federal cases weigh anywhere from 174 to 180grs. Could be this is a heavy case with less capacity.

ES is another factor. The fastest loads will show the flattest primers. If your load has a large ES, this could be the reason.
 
#15
Holeshot said:
Thanks guys. I am using small base dies. Not for any reason other than that's what I have.
Click to expand...

My RCBS small base dies only make my .223/5.56 cases .0005 smaller in diameter than my standard RCBS dies. The big difference is the small base dies size further down the case returning the cases to minimum dimensions.

I would check the case capacity of your Federal cases against Winchester cases or any other brand of cases you have on hand to see how much difference there is.

Also if you average your start loads from all available data and work up you will learn a lot about reading your primers and pressure. One of the first things you should notice is how the primer are protruding from the start loads and as the pressure increases the primers become flush with the base of the case. This is the point where the chamber pressure is great enough to make the brass stretch to meet the bolt face. As pressures increase you will see the primers start to flatten more and base diameter will also become larger.

Below, as pressure increases it reaches a point when it is great enough to cause the brass to stretch and meet the bolt face.

HeadClearance_zpsf30a3af1.gif


Below an exaggerated example of high pressure and expansion at the unsupported base of the case. This is where you measure for any expansion and anything over .001 is a sign to stop increasing your load.

flow_zps2b838d87.gif


Reading primers and measuring base diameter are "ball park" signs due to the different hardness of primers and cartridge cases. As an example military cases are made harder in the base than commercial cases and base expansion readings would indicate different pressure readings. Only actual chamber measuring equipment can give true pressure readings and anything else is just "pressure indicators" and "ball park" signs of pressure.
 
#18
Clark said:
The pressure, if it could be known, would be a red herring.

The weak link, the brass, it the real concern.
Click to expand...

All load data is a red herring unless you have the same identical firearm used and the same identical components. And I already mention the type and make of the cartridge cases giving different pressure indications in my posting above before your "redundant" fish smelling comment. And the OP has found this out with his "guesstimate" of a safe starting load using Hodgdon's load data, and using his cases and components.
facepalm_zpsf5c6ea89.gif
 
#20
Clark

You do not have the test equipment the firearms industry has and your tests are meaningless. In your above test you did not know the hardness of your Winchester brass or the pressures you were operating at. The firearms industry would know both these figures because they have the proper test equipment. All you have done is test one batch/lot of brass which means "NOTHING".

I for one do not understand what you "THINK" you are accomplishing in your test "BUT" I know the firearms industry knows far more than you do and has the test equipment to backup their data.

You talk about red herrings and seem to think your one single test has more worthwhile information than all the testing done by firearms manufactures, ammunition manufactures and the reloading industry.

Your ego is far bigger than your ability and your test are far from comprehensive, you did not even know the hardness of your brass or at what pressure point the brass started to flow. You lack any type test equipment used by professionals and then you have the balls to say the word red herring and chamber pressure in the same breath.

You did not invent the wheel Clark, you didn't even rediscover the wheel but you were run over by one single wheel and you don't even know the tire pressure of the wheel that hit you.

At the beginning of M16 testing the military told the ammunition manufactures their brass was too soft and set new hardness standards for military cartridge cases. And "YOU" do not even know what civilian brass hardness standards are.

Casehardness-a_zps14dbe0fd.jpg
 
Last edited:
#22
918v said:
Clearly, you know not with whom you speak.
Click to expand...

Clark is a electronics engineering consultant and doesn't work in any ballistic test lab, if he did he would have chamber pressure readings to go with his "experiment". Anyone reading this posting could pick up another lot of brass made on a different day and get different load pressure expansion results.

"WHY" would any sane person overload ammunition until the primer pocket failed and risk high pressure gas leakage damaging his firearm.

I'm not impressed with his pointless test because its one lot of brass fired in one firearm "WITHOUT" corresponding pressure data.

At least reloading manuals give you approximate chamber pressures and velocities, and the reloading manuals vary 4.1 grains for maximum loads used here. So "HOW" can Clark say "43 gr. is a 2% overload, and OK to shoot and 46.5 gr is his max load when he doesn't have any pressure measuring equipment to back up his test data.

Quickload shows Clarks 46.5 grain load at 63,466 psi and 3,275 over max rated pressure and 2.5 grains of powder over any loading manual. So much for his "safety" factor and intelligence about "SAFE" reloading practices.

From Quickload - 46.50 grains IMR-4895, 63466 PSI !DANGEROUS LOAD-DO NOT USE!

I have been reloading for over 46 years and never had a single case failure and would "NEVER" advise anyone to do what Clark does without some form of pressure measuring equipment. I don't know how many cases you have seen that Clark has taken past safe loading limits but you need to go back and look at them and ask just how sane his pressure testing is.
 
Last edited:
#24
1/42=2%

Therefore 43grs of H335 is a 2% overload if we assume Hodgdon's book max of 42grs is truly a max load. Not according to QL, though.

My QL says 51grs makes 87,421 PSI. I used 58.3grs for case capacity because a Winchester case fireformed in a SAAMI spec chamber holds 58.3grs of water. Didn't touch the burning rate. 52grs makes 93,508 PSI. I expect the primer to fall out at 93,508 PSI.
 
#25
918v said:
You don't know what you're talking about.
Click to expand...

I do know this, I haven't read anything written by 918v (Violent mental case) or a Clark in any firearms books, manuals or magazines.

Perhaps you and Clark could reveal your secret identity's and your claim to fame in the world of reloading. What I also know beyond a shadow of a doubt is there are thousands of posters in these forums who sit in front of their computers pretending to be giants and their feet don't even touch the floor. (meaning midgets)

But let me clarify my above posting, anyone who recommends loading a .308 2.5 grains of powder over any loading manuals max load is an idiot and an accident waiting for a place to happen in any forum.
 
Last edited:
#26
918v said:
1/42=2%

Therefore 43grs of H335 is a 2% overload if we assume Hodgdon's book max of 42grs is truly a max load. Not according to QL, though.

My QL says 51grs makes 87,421 PSI. I used 58.3grs for case capacity because a Winchester case fireformed in a SAAMI spec chamber holds 58.3grs of water. Didn't touch the burning rate. 52grs makes 93,508 PSI. I expect the primer to fall out at 93,508 PSI.
Click to expand...

The OP is loading IMR-4895 in Federal cases and doesn't know his case capacity, and the Winchester case capacities below do not agree with your math. And my point being case capacity can vary from lot to lot and Winchester brass wasn't the topic brass.

The Federal brass below has an average case capacity of 55.6 grains of H2O and the default capacity of Quickload is 56.0 grains and therefore the pressure readings would be higher. So if the OP uses your 51 grains of IMR-4895 the chamber pressure will be 89,349 psi and "OVER" the maximum proof pressure allowed for proof testing the .308 Winchester.

So again this is why you start low and work up with your firearm and components, and not use someone else's bad advice.

Brass capacity .308 (Win Brass & Laupa& Federal Brass)
 
#27
I do my own brass capacity testing. The reason the case capacities you cite do not agree with mine is because that guy sized his brass prior to testing. For QL you're supposed to measure a case fireformed to your chamber, not sized.
 
#28
josh.rizzo said:
Did you say you used Winchester primers? Because the ones in your picture look silver and the Winchester primers are normally gold colored, but it could be the picture...

Anyways, I've had trouble with Winchester primers not handling pressures that other primers can. You can always try changing components and see if you get the same signs.

Ultimately, I would start with a ladder test from min to max+ instead of guessing at a load. That way you can see what your actual max pressure is. Some rifles are just hard on primers, so starting at min would show you what normal pressure looks like.

Sent from my SCH-I535 using Tapatalk
Click to expand...

34i5mk5.jpg


Here are the primers I used. I have some remington primers that are brass colored. Maybe its the "new" winchester primers that are gold.
 
#29
It sounds like I have just underestimated a few things. One being the importance of a chronograph( I have owned one in the past but it was ruined by water). My previous experiences with reloading have always "worked fine". I currently reload 5 calibers and have never had this trouble. My chronograph results were always somewhat predictable and boring really. Just a confirmation that things worked out how I planned and the game always became trying to keep the "spread" of my velocities as tight as possible. If I thought I was trying some half cocked backwoods hot hot super hot recipe I would have never jumped right into the load I did. I understand the precaution of ramping up slowly and watching for signs of pressure. I have done this in the past and it always seemed like a waste of time as the MAX loads often produce NOTHING as concerning as these primers. I often "shortcut" on a real load development to save money. In my past experience picking a load in the middle of the PUBLISHED data is a safe bet to start from. I will be reevaluating this line of thinking. It seems another variable I have underestimated is case volume. I have understood for years how case volume can affect pressure but I believed it to be such a small change that it only caused me to sort my brass and use the same brand for "batches" and only do so for the consistency needed for accuracy. In retrospect maybe I have just been lucky......30,000 times. (sorry just being a smart ass to myself) The very flat primers made me freak out a little because I have never had trouble with pressure. But I feel like I also never "push the envelope". The fact that I may have inadvertently done so is a humbling thought. I still cant help but feeling like IMR's load data is crazy. Thanks for all of the very helpful advice and discussion. I have a new respect for case volume and components being exactly what is listed. I guess Ill order a chrono and look up future loads in several publications before I settle on a load range.
 
Last edited:
#30
bigedp51 said:
My RCBS small base dies only make my .223/5.56 cases .0005 smaller in diameter than my standard RCBS dies. The big difference is the small base dies size further down the case returning the cases to minimum dimensions.

I would check the case capacity of your Federal cases against Winchester cases or any other brand of cases you have on hand to see how much difference there is.

Also if you average your start loads from all available data and work up you will learn a lot about reading your primers and pressure. One of the first things you should notice is how the primer are protruding from the start loads and as the pressure increases the primers become flush with the base of the case. This is the point where the chamber pressure is great enough to make the brass stretch to meet the bolt face. As pressures increase you will see the primers start to flatten more and base diameter will also become larger.

Below, as pressure increases it reaches a point when it is great enough to cause the brass to stretch and meet the bolt face.

HeadClearance_zpsf30a3af1.gif


Below an exaggerated example of high pressure and expansion at the unsupported base of the case. This is where you measure for any expansion and anything over .001 is a sign to stop increasing your load.

flow_zps2b838d87.gif


Reading primers and measuring base diameter are "ball park" signs due to the different hardness of primers and cartridge cases. As an example military cases are made harder in the base than commercial cases and base expansion readings would indicate different pressure readings. Only actual chamber measuring equipment can give true pressure readings and anything else is just "pressure indicators" and "ball park" signs of pressure.
Click to expand...

Also this makes sense to me as another explanation of what could be happening or at least what can happen. Thanks. Good lesson.
 
Last edited:
#32
918v said:
I do my own brass capacity testing. The reason the case capacities you cite do not agree with mine is because that guy sized his brass prior to testing. For QL you're supposed to measure a case fireformed to your chamber, not sized.
Click to expand...

I have always considered brass capacity testing to be reserved for hole in hole benchrest shooters with $20000 90 pound rifles. Right up there with neck turning and measuring bullet concentricity. I understand all of these things contribute to accuracy/consistency but where do you draw the line? Im shooting a bone stock $600 rifle. Some people load "match grade" ammo on progressive reloaders and rely on powder throws. (gulp) What is the average deviation with extruded powder that meters like crap in a throw? Im just amazed that the slightly less volume federal cases have would be enough of a factor that they may have contributed to an overpressure situation. Ill just start over and be more careful about brushing off things I have previously though to be of little consequence. Again all of this information has been enlightening and really makes me want to tighten up my game and become a better and more informed handloader. Thanks!
 
Last edited:
#34
Holeshot said:
Some people load "match grade" ammo on progressive reloaders and rely on powder throws. (gulp) What is the average deviation with extruded powder that meters like crap in a throw? Im just amazed that the slightly less volume federal cases have would be enough of a factor that they may have contributed to an overpressure situation.
Click to expand...


It don't matter if it's a $600 or $6000 rifle. A chamber is a chamber and pressure is pressure. The difference between Winchester and Federal is substantial. While your hand load is not unsafe (as in going to explode your rifle), it certainly is hot and will cause your brass to fail within a couple of reloads. FC brass is soft and those primer pockets will loosen up quickly. Why go there? When you are near max, the cost of 100 FPS is 10,000 PSI. Not worth it to me.

The average deviation of a typical powder measure is half a grain. And if you are on the OCW node it will not affect group size or Point of Impact at 100 yards. But it will have a substantial effect further down range due to an increase in ES. I have recently replicated a pretty neat sniper load. I found that a .2gr deviation from the sweet spot doubles the ES. A .4gr deviation triples it. The ES goes from 15 to 30 to 50 FPS. And the sweet spot is different for different brass. And it's even different for new brass vs fireformed/sized brass.
 
#36
918v said:
I do my own brass capacity testing. The reason the case capacities you cite do not agree with mine is because that guy sized his brass prior to testing. For QL you're supposed to measure a case fireformed to your chamber, not sized.
Click to expand...

The brass in the posted link was once fired and still had the primer in the brass for his capacity testing. It would be nice if you read the link before jumping to the INCORRECT conclusion of WHY the differences in case capacity.

If you spend the money for Quickload software, reading the instructions would be part learning how to input the proper data.

QL-2volume_zps1e227374.jpg
 
#37
Holeshot said:
Im just amazed that the slightly less volume federal cases have would be enough of a factor that they may have contributed to an overpressure situation.
Click to expand...

Holeshot below are pressure/velocity charts from Quickload, the two charts show the pressure variations between cases with 30.6 and 28.0 grains of H2O capacity and over 6,000 psi in pressure variation.

Below a Lake City 5.56 case with 30.6 of H2O capacity and 25 grains of H335.

308_zpsf81bb4cc.jpg


Below a Lapua case with 28.0 grains of H2O capacity and 25 grains of H335.

288_zps26698a67.jpg
 
#38
Wow that is a big difference. I see now the error of my thinking. Like I said I knew it was a factor but I didn't realize how much. Great charts. Thanks! If I'm going to be changing loads and trying new things maybe I need to invest in some similar software.

I have some 220gr 300wm loads that I am questioning now.
 
#39
bigedp51 said:
The brass in the posted link was once fired and still had the primer in the brass for his capacity testing. It would be nice if you read the link before jumping to the INCORRECT conclusion of WHY the differences in case capacity.

If you spend the money for Quickload software, reading the instructions would be part learning how to input the proper data.

QL-2volume_zps1e227374.jpg
Click to expand...


I did read the instructions. FYI, the .308 Winchester IS a high pressure round.

Second, the link you provided shows Winchester data that mimics my RESIZED cases. Interesting.
 
#41
bigedp51 said:
Holeshot below are pressure/velocity charts from Quickload, the two charts show the pressure variations between cases with 30.6 and 28.0 grains of H2O capacity and over 6,000 psi in pressure variation.

Below a Lake City 5.56 case with 30.6 of H2O capacity and 25 grains of H335.

308_zpsf81bb4cc.jpg


Below a Lapua case with 28.0 grains of H2O capacity and 25 grains of H335.

288_zps26698a67.jpg
Click to expand...


Why don't you show him a QL chart appropriate to the topic which is .308 Winchester? It's only fair since you criticized Clark for not talking about IMR4198. Oh, I know why. It's cuz QL shows his load to only make 51,000 PSI which does not make sense cuz it's 2grs over Sierra's max.
 
#44
918v said:
Why don't you show him a QL chart appropriate to the topic which is .308 Winchester? It's only fair since you criticized Clark for not talking about IMR4198. Oh, I know why. It's cuz QL shows his load to only make 51,000 PSI which does not make sense cuz it's 2grs over Sierra's max.
Click to expand...

Do you always pout and act like a cry baby in forums when you are wrong.

crybaby_zpsac92aceb.jpg
 
#48
A quick note to those of you citing quick load for pressure numbers - you need to take into account different chamber dimensions. A wider chamber will allow the brass to absorb more energy as it expands, reducing the overall pressure reading, but potentially reducing brass life as well. I don't remember the source, but I read that pressure numbers are not as scientific as they sound, especially CUP units. The environment in a gun chamber is too dynamic to sum it up in a single number. I have fired some loads a good grain or two over what loading manuals say with no pressure signs, including case head expansion. Quick load is a great tool, but not the end-all tool. Not that I'm discrediting your conclusions, just something to keep in mind - you can't necessarily use quick load to tell the pressure in someone else's chamber.

This thread has some great info though. Keep it up!

Sent from my SCH-I535 using Tapatalk
 
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