New 308 reloader seeking input on pressure signs.

[jlow]

These pieces of brass are from my 18” OBR that I am developing a load for.

This first series came from a ladder shot with 42.0 to 45.0 gr of Varget loaded in new Win brass and capped with 147 gr SMK seated with OAL of 2.800 and Rem 9 ½ primers. No MV data since my chrono was down that day.

This second series of brass came from two loads I was testing – the top row was with 43.5 and the bottom 43.0 gr of Varget. Both five round groups ended up being sub MOA. Chrono was working and the average MV was 2428 ft/sec (43.0 gr) and 2455 ft/sec (43.5 (edited) gr).

I am currently interested in using the 43.0 gr weight since it was the most accurate (0.827 MOA). In the ladder group, I see a little primer flattening in all the brass with increasing degree of flattening at the higher powder range although some primer radius was still visible at 45.0 gr. Primer crater was also visible in all the primers. Extractor mark was visible at the three highest weights.

In the brass from the two loads (i.e. 43.0 and 43.5 gr), slight primer flattening, cratering was visible in all the brass and interestingly extractor mark was visible in three out of five pieces of brass from each group.

The last graph shows the diameter of the brass case head described above together with two control groups i.e. five unfired Winchester cases and five fired WCC 7.62x51 NATO 147 gr. FMJ cases all fired from the same chamber.

This graph below summarize the data. First, the data for the unfired Win brass I put in as 41.00 grain (blue box) just so that it is in the graph. Second, the data from the WCC 7.62x51 NATO 147 gr. FMJ I put in as 46.00 gr. (red box) again so that it is in the graph.

The results appear to show a progressive increase in case head size going from 42.00 to 45.00 grains but with none of the currently tested Varget powder weight exceeding the WCC induced changes. The 43.00 gr. weight that I am currently interested in appears to be lower than that of the diameter seen for the WCC brass.

So my question is based on what I have described above, would it be reasonable to conclude that the 43.0 gr of Varget is a safe to shoot? I am developing the rounds for shooting at a 600 yards range.

Thanks ahead for your input.

 

[want2Baccurate]

Re: New 308 reloader seeking input on pressure signs.

I am really new to reloading, so take my advice with some skepticism. My grandfather told me that a possible reason for marks like that in a semi auto is due to the round pushing against a bolt that is not all the way seated. I guess it is just enough off to provide more bolt thrust. My grandfather told me that if I have cases like that when I reload for my AR that I should try neck sizing only some once fired brass from my gun. If I get marks like that with the new brass then it is not a locking problem.
I apologize if this info is incorrect, or doesn't make sense. Like i said, I'm new.

 

[jlow]

Re: New 308 reloader seeking input on pressure signs.

Thanks for the input, guess we are in the same boat!

Interesting ideas and I can see how if it was once fired brass that has not been resized may be just a bit too big to fit back in the chamber resulting in a not totally closed bolt.

However, in my case, I probably cannot blame that since the brass was new.

 

[BCP]

Re: New 308 reloader seeking input on pressure signs.

All of your loads are fine, the marks on the cases are fine, the case growth is fine. If you notice chambering problems consider a small base full length resizing die.

FWIW my go-to load is 43.5 varget + 178 amax in win brass and it is easy on the brass and the rifle. 2450fps out of an 18".

With a 150 I use 45 varget, it is also easy on the brass, around 2650-2700fps.

 

[jlow]

Re: New 308 reloader seeking input on pressure signs.

Thanks! Much appreciated! I settled on that powder range because in my survey of the web, it appears to be what people are using, that and Hodgon publish data also appears to agree this was a reasonable powder range, just a little concern when I saw the extractor marks. Looks like we are getting the same MVs which is great confirmation (I corrected my typo).

I actually tried to chamber the all fired 43.0 gr. case and the bolt went in without too much pressure and extracted the same way, so my guess is the regular full length resizing die will work fine for me.

I am also glad to hear that this load is easy on the brass and rifle. This seems like a pretty accurate load and would hate to have to balance beating up the brass and accuracy, but it looks like I can have my cake and eat it too in this case.

Thanks again for your help and input.

 

[turbo54]

Re: New 308 reloader seeking input on pressure signs.

I recently ran 3 ladders with Varget and 168, 175 and 180gr SMKs.

Went to 47.5gr on the 168, and 46.5 on the 175 with no bad pressure. Slight cratering, but VERY slight. Found pressure at 45.5gr on the 180. Cratering was a bit worse and I had a bit of resistance in opening the bolt. This was in an FN SPR. For comparison, 43 gr with a 180smk is a MAX load in my savage. Was chronoing with a buddy at the gun club today, and we found FLAT primers (no radius left at all) at 46gr with a 168SMK. Rifle was a GAP crusader (nice rifle)

Your loads are fine, and im sure you could go a good bit hotter without too much pressure.

 

[jlow]

Re: New 308 reloader seeking input on pressure signs.

Thanks turbo54. Good to hear that my loads are GTG.

Sorry for the slow response, but I kinda lost the thread as I originally posted this in the “Semi-Auto Rifles” board by mistake and did not realize that it was moved here until today.

 

[MitchAlsup]

Re: New 308 reloader seeking input on pressure signs.

My 308 long range loading has a heavier bullet (155gr) and a heavier powder charge (47.8gr Varget) and shows no particular pressure signs. In one lot (100 pieces) I have had 30 reload cycles on the brass and not lost a primer pocket of a neck (I did loose 4 cases on cycle 29 fom body crack and incipient case head separation.)

Note: The above is for a bolt gun, and is a very stiff loading (just inside sane pressure limits). It might not be acceptable for a gas gun.

 

[aquinas]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: want2Baccurate</div><div class="ubbcode-body">I am really new to reloading, so take my advice with some skepticism. My grandfather told me that a possible reason for marks like that in a semi auto is due to the round pushing against a bolt that is not all the way seated. I guess it is just enough off to provide more bolt thrust. My grandfather told me that if I have cases like that when I reload for my AR that I should try neck sizing only some once fired brass from my gun. If I get marks like that with the new brass then it is not a locking problem.
I apologize if this info is incorrect, or doesn't make sense. Like i said, I'm new. </div></div>

Not to be a (fill in favorite expletive), but your grandfather sounds like an idiot. Maybe he doesn't like you or something. Necksizing only ANY autoloader is dangerous. Could getch kilt, or very hurt. Not likely, but can still happen on an AR. Why tempt fate?

 

[aquinas]

Re: New 308 reloader seeking input on pressure signs.

This thead is very interesting. I am loading the same brass with 4895 and 168's. I'm also getting the same looking marks, and it's not all the time.

So what do we look for as far as pressure signals are concerned?

IMO, all your primers look fine. Most military style rifles with floating pins crater all primers, regardless of load.

 

[jlow]

Re: New 308 reloader seeking input on pressure signs.

Good question.

My thoughts are to look for primers that are really (not slightly) flat i.e. lost the radius on the side. The extractor mark is also definitely pressure related (see the first batch with increasing pressure), but they are only in some of the two loads I was testing, so perhaps consistent extractor marks on majority of the brass….?

 

[Clark]

Re: New 308 reloader seeking input on pressure signs.

With this "me too" post, I wanted to see if I could display data that had meaning for my real limit, loose primer pockets.

 

[aquinas]

Re: New 308 reloader seeking input on pressure signs.

Cool post. Where'd you get that? is that your pic?

So...as long as the extractor is not noticibly denting the head, all is well? Assuming no pressure signs from the primer.

So the 2nd pic from the right looks as if primer metal has flowed into the radius...right before blowing the primer.

You refer to your "real limit." What do you mean by that? Are you saying a loose primer pocket is the fer sure, no doubt pressure sign and all the rest are iffy.

All this stuff is so subjective. I have M14's that always crater and flatten primers...even with the mildest of loads.

do each one of those pics correspond to the load increment at the bottom of the chart?

 

[Clark]

Re: New 308 reloader seeking input on pressure signs.

That was my first digital camera. I am now on my 3rd.
My test in 2003:
Pacific .308 Win reamer, VZ24 trued action, A&B fluted stainless 24" F54 barrel, H335, CCI200 primer, 2.9" OAL, Speer 168 gr. HPBT Gold Match, brass: Win308Win:

 

[turbo54]

Re: New 308 reloader seeking input on pressure signs.

Clark: Is there a .5gr diff between the far right case, and the one directly to its left?

I ask because the primer looks flattened, but not FLAT on that case. Thats about how my go-to load for my FN looks, and I haven't been sweating it, because I've been .5gr higher (Varget), and noticed a slightly sticky bolt lift. I guess I'm just surprised that .5gr more blew the primer out, when the primer looked pretty ok (high pressure, but not scary high).

I see you're using H355, which I have zero experience with. I assume that makes a big difference.

 

[500grains]

Re: New 308 reloader seeking input on pressure signs.

note to self: 49.0 Varget.


Does the bullet weight matter?

 

[Clark]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">Clark: Is there a .5gr diff between the far right case, and the one directly to its left? </div></div>
My pic shows 43-52 gr in 1 gr steps.
42 is only on the graph because that is the max book load.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 500grains</div><div class="ubbcode-body">..Does the bullet weight matter?..</div></div>
Heavier bullets need less powder, unlike heavier dogs that need MORE dog food. Your wife can explain that to you.

 

[jlow]

Re: New 308 reloader seeking input on pressure signs.

LOL! You lost me. If the graphics show a test with H335, and Hodgdon’s max is indeed 42.0 gr, what are you doing testing 43 to 52 gr of the stuff?

 

[BCP]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">Good question.

My thoughts are to look for primers that are really (not slightly) flat i.e. lost the radius on the side.</div></div>

Reading primers isn't the way to go. Look for very pronounced marks on the case head and case head growth. An easy way to test for growth is to take your shell holder to the range with you and see if your fired cases fit easy or not.

edit: soft primer pockets (ie, the primers just "pop" right in with zero effort) is another sign. Your 43 varget 150 grain bullet 308 load is anemic so your brass should last forever.

 

[jlow]

Re: New 308 reloader seeking input on pressure signs.

Thanks for the input. I agree about the primers as not being very predictive, but I do look at them together with the other signs. That graph I have in the OP is actually a measurement of the case head so we are on the same page. The idea of bringing a shell holder to the range is a good idea, just a clarification though, when you say shell holder, you mean case length headspace gage?

As for the anemic load, slight misunderstanding, I am loading 175 gr and not 150 gr bullets.

 

[sandwarrior]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BCP</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">Good question.

My thoughts are to look for primers that are really (not slightly) flat i.e. lost the radius on the side.</div></div>

Reading primers isn't the way to go. Look for very pronounced marks on the case head and case head growth. An easy way to test for growth is to take your shell holder to the range with you and see if your fired cases fit easy or not.

edit: soft primer pockets (ie, the primers just "pop" right in with zero effort) is another sign. Your 43 varget 150 grain bullet 308 load is anemic so your brass should last forever.</div></div>

I'll have to disagree, I think reading primers is the first best way to tell if you're getting hot. But, the qualifier with this is you have to have tight rounds in your chamber. Meaning factory sized rounds (minimum size) are going to be flatter from a larger chamber than a smaller chamber. Remember gun manufacturers use chamber reamers on a lot of rifles before they get sent in and sharpened. They can be sharpened down to a minimum size. So, there is a 'range' of chamber sizes. The larger chambers will show more pronounced flattening of primers.
In those chambers you will need to have at least once fired rounds pushed through them to be able to read the primers accurately.
<span style="text-decoration: underline">I will agree</span> that you can't read the primers accurately without them going through a known tight chamber (to the case). It's really a matter of the accuracy of being able to read them, not that you can't. In most 'first firings' and semi-autos it's tougher to read them. It's also tougher to determine whether case head marks are due to loose cases or hot cases. Most AR's leave marks when extracting the case.

Looseness of primers is the definite tell-tale if a round is loaded too hot. The primers may look a little flat or cratered but if they seat well it's not too hot, it's looseness of the case in the chamber. If they won't go in firmly then it's <span style="text-decoration: underline">too hot for that case.</span> I say that because there is a difference between cases as to hardness. One of the reasons people like Lapua is they have consistently hard headed cases that don't expand unless they get loaded way too hot. Conversely, Federal cases tend to expand no matter what. Norma has great consistency, but they too tend to expand in the head area when loaded close to max.

 

[sandwarrior]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">LOL! You lost me. If the graphics show a test with H335, and Hodgdon’s max is indeed 42.0 gr, what are you doing testing 43 to 52 gr of the stuff?</div></div>

He worked up to know where "his" rifle's max load was. Oftentimes a manufacturer gives the lowest 'high' they can to limit liability. In many cases where the lands have eroded because of shooting (such as competition) the loads will run up to five grains over the maximum load given by either a bullet or powder manufacturer. What you are seeing is normal up to the point where he had the primer blow out. Based on what I see with the previous case I wouldn't have stopped the ladder either.

 

[aquinas]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BCP</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">Good question.

My thoughts are to look for primers that are really (not slightly) flat i.e. lost the radius on the side.</div></div>

Reading primers isn't the way to go. Look for very pronounced marks on the case head and case head growth. An easy way to test for growth is to take your shell holder to the range with you and see if your fired cases fit easy or not.

edit: soft primer pockets (ie, the primers just "pop" right in with zero effort) is another sign. Your 43 varget 150 grain bullet 308 load is anemic so your brass should last forever. </div></div>

Idiot question of the day:

Where do you measure the case head? Do you measure it just above the rim? 1/8th of an inch above the rim?

 

[aquinas]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BCP</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">Good question.

My thoughts are to look for primers that are really (not slightly) flat i.e. lost the radius on the side.</div></div>

Reading primers isn't the way to go. Look for very pronounced marks on the case head and case head growth. An easy way to test for growth is to take your shell holder to the range with you and see if your fired cases fit easy or not.

edit: soft primer pockets (ie, the primers just "pop" right in with zero effort) is another sign. Your 43 varget 150 grain bullet 308 load is anemic so your brass should last forever.</div></div>

I'll have to disagree, I think reading primers is the first best way to tell if you're getting hot. But, the qualifier with this is you have to have tight rounds in your chamber. Meaning factory sized rounds (minimum size) are going to be flatter from a larger chamber than a smaller chamber. Remember gun manufacturers use chamber reamers on a lot of rifles before they get sent in and sharpened. They can be sharpened down to a minimum size. So, there is a 'range' of chamber sizes. The larger chambers will show more pronounced flattening of primers.
In those chambers you will need to have at least once fired rounds pushed through them to be able to read the primers accurately.
<span style="text-decoration: underline">I will agree</span> that you can't read the primers accurately without them going through a known tight chamber (to the case). It's really a matter of the accuracy of being able to read them, not that you can't. In most 'first firings' and semi-autos it's tougher to read them. It's also tougher to determine whether case head marks are due to loose cases or hot cases. Most AR's leave marks when extracting the case.

Looseness of primers is the definite tell-tale if a round is loaded too hot. The primers may look a little flat or cratered but if they seat well it's not too hot, it's looseness of the case in the chamber. If they won't go in firmly then it's <span style="text-decoration: underline">too hot for that case.</span> I say that because there is a difference between cases as to hardness. One of the reasons people like Lapua is they have consistently hard headed cases that don't expand unless they get loaded way too hot. Conversely, Federal cases tend to expand no matter what. Norma has great consistency, but they too tend to expand in the head area when loaded close to max. </div></div>


That explains everything for me: I use a small base die for my autoloaders and that is apparently why I see ejector marks on just about every case, no matter. They are very light marks, by the way.

Also explains why my primers flatten.

Just ordered Tubb's Carrier Weight System today. That might help.

 

[turbo54]

Re: New 308 reloader seeking input on pressure signs.

His post also explains something I've been wondering about:

7.62 NATO ammo has lower pressure than 308, yet every piece of once fired nato brass I see has a FLAT primer. Mil-spec M14s have loose chambers...

 

[jlow]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">LOL! You lost me. If the graphics show a test with H335, and Hodgdon’s max is indeed 42.0 gr, what are you doing testing 43 to 52 gr of the stuff?</div></div>

He worked up to know where "his" rifle's max load was. Oftentimes a manufacturer gives the lowest 'high' they can to limit liability. In many cases where the lands have eroded because of shooting (such as competition) the loads will run up to five grains over the maximum load given by either a bullet or powder manufacturer. What you are seeing is normal up to the point where he had the primer blow out. Based on what I see with the previous case I wouldn't have stopped the ladder either. </div></div>

Thanks! That makes sense. When I was researching 308 loading, the first table I ran across was the one from Sierra and their load range for 175 SMKs and Varget was between 36.3 and 41.7 gr which was a stark contrast of 42.0 to 45.0 in Hodgdon's published data for the same round/powder. So I can see the liability factor in there.

To continue my education, my question is when the lands erode, can I assume that this will reduce pressure which shows up as a drop in MV under the same load, and the increase in powder weight is an attempt to bring the pressure/MV back to original levels?

 

[500grains]

Re: New 308 reloader seeking input on pressure signs.

Clark,

What about battering a semi auto like an AR10 or M14 all to crap BEFORE max pressure is reached, unlike a bolt gun?

I wonder how to find the reasonable limit without beating a $3K gun to shiite.

 

[sandwarrior]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BCP</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">Good question.

My thoughts are to look for primers that are really (not slightly) flat i.e. lost the radius on the side.</div></div>

Reading primers isn't the way to go. Look for very pronounced marks on the case head and case head growth. An easy way to test for growth is to take your shell holder to the range with you and see if your fired cases fit easy or not.

edit: soft primer pockets (ie, the primers just "pop" right in with zero effort) is another sign. Your 43 varget 150 grain bullet 308 load is anemic so your brass should last forever.</div></div>

I'll have to disagree, I think reading primers is the first best way to tell if you're getting hot. But, the qualifier with this is you have to have tight rounds in your chamber. Meaning factory sized rounds (minimum size) are going to be flatter from a larger chamber than a smaller chamber. Remember gun manufacturers use chamber reamers on a lot of rifles before they get sent in and sharpened. They can be sharpened down to a minimum size. So, there is a 'range' of chamber sizes. The larger chambers will show more pronounced flattening of primers.
In those chambers you will need to have at least once fired rounds pushed through them to be able to read the primers accurately.
<span style="text-decoration: underline">I will agree</span> that you can't read the primers accurately without them going through a known tight chamber (to the case). It's really a matter of the accuracy of being able to read them, not that you can't. In most 'first firings' and semi-autos it's tougher to read them. It's also tougher to determine whether case head marks are due to loose cases or hot cases. Most AR's leave marks when extracting the case.

Looseness of primers is the definite tell-tale if a round is loaded too hot. The primers may look a little flat or cratered but if they seat well it's not too hot, it's looseness of the case in the chamber. If they won't go in firmly then it's <span style="text-decoration: underline">too hot for that case.</span> I say that because there is a difference between cases as to hardness. One of the reasons people like Lapua is they have consistently hard headed cases that don't expand unless they get loaded way too hot. Conversely, Federal cases tend to expand no matter what. Norma has great consistency, but they too tend to expand in the head area when loaded close to max. </div></div>


That explains everything for me: I use a small base die for my autoloaders and that is apparently why I see ejector marks on just about every case, no matter. They are very light marks, by the way.

Also explains why my primers flatten.

Just ordered Tubb's Carrier Weight System today. That might help.</div></div>

Cool! Let us know how that works?

 

[sandwarrior]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">LOL! You lost me. If the graphics show a test with H335, and Hodgdon’s max is indeed 42.0 gr, what are you doing testing 43 to 52 gr of the stuff?</div></div>

He worked up to know where "his" rifle's max load was. Oftentimes a manufacturer gives the lowest 'high' they can to limit liability. In many cases where the lands have eroded because of shooting (such as competition) the loads will run up to five grains over the maximum load given by either a bullet or powder manufacturer. What you are seeing is normal up to the point where he had the primer blow out. Based on what I see with the previous case I wouldn't have stopped the ladder either. </div></div>

Thanks! That makes sense. When I was researching 308 loading, the first table I ran across was the one from Sierra and their load range for 175 SMKs and Varget was between 36.3 and 41.7 gr which was a stark contrast of 42.0 to 45.0 in Hodgdon's published data for the same round/powder. So I can see the liability factor in there.

To continue my education, <span style="font-weight: bold">my question is when the lands erode, can I assume that this will reduce pressure which shows up as a drop in MV under the same load, and the increase in powder weight is an attempt to bring the pressure/MV back to original levels?</span></div></div>

Yes and no. It <span style="text-decoration: underline">is</span> true when you are 'chasing' the lands. Meaning if you seat into the lands for accuracy and keep seating your bullet out more and more <span style="color: #3333FF">{added: as you experience erosion}</span>, you will lose pressure and need to make it up by adding powder. But, if your bullet shoots just fine without chasing the lands you will usually get an increase in velocity. <span style="text-decoration: underline">Not pressure though</span>. What's happening is the bullet gets that little bit of extra freebore to gain velocity. Seated down in the case to a given height that cartridge will produce the same pressure initially as before.

 

[Clark]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 500grains</div><div class="ubbcode-body">Clark,

What about battering a semi auto like an AR10 or M14 all to crap BEFORE max pressure is reached, unlike a bolt gun?

I wonder how to find the reasonable limit without beating a $3K gun to shiite. </div></div>

500G......... funny name, are you an African American rapper?

You are trying to increase your status with expensive guns.
I don't own an AR10 or M14, because they cost too much.
I do have FALs with gas by pass adjustments for hot and wimpy ammo.
BARs have gas regulators [a nut with a hole in it, like a carburetor fixed jet], and I make my own from scratch or ream out factory regulators, to compensate for my hot ammo.

Avoiding battering can get more complicated.
My father was here Saturday and I was asking him about one of his machine gun designs for the marines. I understood everything but the "Flow control Valve" which is set on the first round. There are 5 types of ammo, from wimpy "zone 1" ammo, to hot "zone 5" ammo.
Off the recoil cylinder he has fluid going in and out of a Nitrogen filled accumulator. In between is this valve that is a piston pushing on a spring and fed by a check valve. There must be different ports exposed with different positions of the piston. The idea is to return to battery at 1/2 the free recoil velocity expected from the next round. On the last round, the mechanism goes forward and encounters a parabolic taper, of a pistol-cylinder fit, that stops the gun without battering.

 

[jlow]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">LOL! You lost me. If the graphics show a test with H335, and Hodgdon’s max is indeed 42.0 gr, what are you doing testing 43 to 52 gr of the stuff?</div></div>

He worked up to know where "his" rifle's max load was. Oftentimes a manufacturer gives the lowest 'high' they can to limit liability. In many cases where the lands have eroded because of shooting (such as competition) the loads will run up to five grains over the maximum load given by either a bullet or powder manufacturer. What you are seeing is normal up to the point where he had the primer blow out. Based on what I see with the previous case I wouldn't have stopped the ladder either. </div></div>

Thanks! That makes sense. When I was researching 308 loading, the first table I ran across was the one from Sierra and their load range for 175 SMKs and Varget was between 36.3 and 41.7 gr which was a stark contrast of 42.0 to 45.0 in Hodgdon's published data for the same round/powder. So I can see the liability factor in there.

To continue my education, <span style="font-weight: bold">my question is when the lands erode, can I assume that this will reduce pressure which shows up as a drop in MV under the same load, and the increase in powder weight is an attempt to bring the pressure/MV back to original levels?</span></div></div>

Yes and no. It <span style="text-decoration: underline">is</span> true when you are 'chasing' the lands. Meaning if you seat into the lands for accuracy and keep seating your bullet out more and more <span style="color: #3333FF">{added: as you experience erosion}</span>, you will lose pressure and need to make it up by adding powder. But, if your bullet shoots just fine without chasing the lands you will usually get an increase in velocity. <span style="text-decoration: underline">Not pressure though</span>. What's happening is the bullet gets that little bit of extra freebore to gain velocity. Seated down in the case to a given height that cartridge will produce the same pressure initially as before. </div></div>

OK, I understand. From that standpoint, I am pretty luck as I did have to seat to the lands for my AR-15, but for the AR-10, it appears to be sub-MOA seated to mag length i.e. 2.800, so I dont' have to chase the lands.

 

[500grains]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 500grains</div><div class="ubbcode-body">Clark,

What about battering a semi auto like an AR10 or M14 all to crap BEFORE max pressure is reached, unlike a bolt gun?

I wonder how to find the reasonable limit without beating a $3K gun to shiite. </div></div>

500G......... funny name, are you an African American rapper?

You are trying to increase your status with expensive guns.
I don't own an AR10 or M14, because they cost too much.
I do have FALs with gas by pass adjustments for hot and wimpy ammo.
BARs have gas regulators [a nut with a hole in it, like a carburetor fixed jet], and I make my own from scratch or ream out factory regulators, to compensate for my hot ammo.

Avoiding battering can get more complicated.
My father was here Saturday and I was asking him about one of his machine gun designs for the marines. I understood everything but the "Flow control Valve" which is set on the first round. There are 5 types of ammo, from wimpy "zone 1" ammo, to hot "zone 5" ammo.
Off the recoil cylinder he has fluid going in and out of a Nitrogen filled accumulator. In between is this valve that is a piston pushing on a spring and fed by a check valve. There must be different ports exposed with different positions of the piston. The idea is to return to battery at 1/2 the free recoil velocity expected from the next round. On the last round, the mechanism goes forward and encounters a parabolic taper, of a pistol-cylinder fit, that stops the gun without battering.
</div></div>

Was that design validated by issuance of a patent?

 

[Clark]

Re: New 308 reloader seeking input on pressure signs.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 500grains</div><div class="ubbcode-body">
Was that design validated by issuance of a patent? </div></div>
I have a big note book of his patents here, and 4,353,285 looks like the "flow control valve".
http://www.freepatentsonline.com/4353285.pdf
Maybe I should read this and stop asking him dumb questions.