Pressure signs?

[tt350z]

First off, I'd like to say that I am brand new to reloading and I don't personally know anybody that reloads centerfire ammo.

I usedthe sticky's by TreSMon and Lyman 49th as my guide.

Rifle used is in my sig, but here's the snapshot:
SAC built M2008
Bartlein MTU 1-11.25'' 30 cal barrel, chambered 308 SAC Match
Cut to 18.5 at muzzle from action face (20'' from boltface to muzzle)

Shooting condidtion:
64ºF
40% humidity
29.74 inHg
1600' ASL

Competition Electronics Pro Chrono Digital 10' from muzzle

I shot some factory loaded Nosler 168 gr Custom Competition ammo for a baseline to compare with my handloads to see if they had any pressure signs compared to the factory loaded stuff.

All pictures are linked to fullsize if you need to see a larger version.

Nosler 168 gr CC. The 3 on the left had signs of a small gas leak from the primer and the 4th on the right had the worst cratering. Some of the cases as slight mark from ejector

Advertised velocity 2750 FPS

Actual:
2737 FPS
2737 FPS
2726 FPS
2743 FPS

Avg: 2735 FPS




My loads:
1x fired American Eagle 7.62x51 MIA brass (what I have on hand)
shoulders bumped back .003''
cases trimmed to 2.005''
uniformed flash hole
SMK 175 gr
RL15
CCI 200 primer
.010'' into the lands
Ogive length 2.205''
OAL apprx 2.775ish'' (off the top of my head)

I started with loads from 40 gr increasing in .5 gr increments, all powder weight was hand trickled. I checked each and every piece of brass for any gas leak, ejector marks, flat primers, etc. I didn't notice any sticky bolt (other than the heavier bolt lift of the M2008 action). Nothing was out of the ordinary and actually showed less pressure signs than the facotry loaded Nosler's, IMO.

Below is 44.5 gr of RL15 (book max 44.3 gr)

Chronoed:
2743 FPS
2749 FPS
2737 FPS
2721 FPS
2721 FPS

Avg: 2734 FPS (seems pretty fast to me with my shorter barrel and heavier bullet. First time using the chrono, so it may be reading fast?)




Below is 45 gr of RL15

Chronoed:
2795 FPS
2772 FPS
2754 FPS
2749 FPS
2737 FPS

Avg: 2761 FPS




Does any of my max and max + loads show anything excessive/dangerous to you?

Any advise is greatly appreciated, thanks.

 

[turbo54]

Re: Pressure signs?

Top picture, bottom set of 4 cases, far right - primer looks pretty flat.

Other than that, all look fine to me.

 

[MALLARD]

Re: Pressure signs?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tt350z</div><div class="ubbcode-body"> Below is 44.5 gr of RL15 (book max 44.3 gr) ....I started with loads from 40 gr increasing in .5 gr increments
</div></div>

if im reading this correctly you purposely exceeded the max load data in your book. I dont think you should be doing that. I'd recommend staying .02 under max , not .02 over, or even a whole grain under max.

.5 increments is to fast , maybe for an experienced reloading just doing some initial pressure tests/observations it might be ok , but for a novice i think its to fast. but being honest , i dont think anyone should work up that fast.

starting at 40 grs is ok , maybe 38 grains wouldnt have hurt , doesnt matter now. Doing that might have given you some ideas of what low pressure ammo looks/acts like.

some of your primers are flatter then i'd be comfortable with. but I cant tell by looking at your pictures alone.

that last picture looks ok ,the frist and 2nd pics look hot. So , i guess your ok ? its hard to judge pressure without being able to see the cases in person.

 

[tt350z]

Re: Pressure signs?

Updated the original posts with the velocity that I chronoed. They did seem pretty fast to me, buts that's what my chrono said, so it's all I've got.

Mallard, I agree that .5 gr may have been a bit of a big jump. I did start with the 40 gr load and thoroughly checked all the brass for any leaking gas, extractor/ejector marks, or excessively flat primers before shooting another round. I felt confident enough to continue with the loads as none had any pressure signs matched or exceeded the factory loaded Nosler's.

Also, your opinion was that the last pictures look ok pressure wise. Those were the hottest loads I have and I also thought that they displayed much less signs of pressure than the Nosler's.

I'll post some pictures from the lower charged brass when I get a chance for comparison as well.

 

[damoncali]

Re: Pressure signs?

Back off. Those primers are flattening a little and cratering ("flowing" around the firing pin). You can also see what looks like a dark ring around some of the primers which indicates gas leakage (it's tough to see on the hand loads - the factory ones are pretty obvious, though). Those are definitely pressure signs.

 

[Mordamer]

Re: Pressure signs?

The notion that you cannot exceed book max charges without being in grave danger is wrong. Each chamber in each gun is different and most factory chambers will show pressure signs well above book listed maximums. If you work up slowly and check each piece of brass after you fire, you will be fine and you will also learn exactly how your chamber compares to the chamber used by whoever printed your reloading manual. You are not going to instantly blow up your gun by exceeding book max. The harsh warnings in the books are there to protect the companies that write the manuals. I'm done ranting. I just get tired of seeing people get chastised for exceeding book maximum values. I'll stop ranting.

Go up by a few tenths of a grain at a time. When you see real pressure signs then stop and know you have discovered the upper limit. You'll know when you get there.

 

[Mordamer]

Re: Pressure signs?

One more thing. The primer cratering is nothing to worry about in this case. Every one of his primers shows that crater. Many guns do this. It is simply an over sized firing pin whole in the end of the bolt. Even the low pressure loads will show that crater. Don't worry about it.

 

[damoncali]

Re: Pressure signs?

There is no good reason to push pressure limits. Use a bigger cartridge if you want more velocity. Working past book max based on what your case looks like (or other "real pressure signs", whatever that means) is a stupid idea. There is literally nothing to gain, and a heck of a lot to lose.

 

[Mordamer]

Re: Pressure signs?

Do what you want. Anyone with experience reloading knows that book max values are nothing to judge every gun by. Look at several different books and you will find in many cases that the max values from one book will be 2 grains lower than the max values for another book. Think about that for awhile and decide on if you want to trust book max values. I was just trying to point out that REAL max values can be approached safely and discovered for each individual firearm.

I see no signs of high pressure in the original posters hottest loads. The primers could have a much sharper radius and I don't see any brass flowing into the ejector hole.

 

[tt350z]

Re: Pressure signs?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mordamer</div><div class="ubbcode-body">One more thing. The primer cratering is nothing to worry about in this case. Every one of his primers shows that crater. Many guns do this. It is simply an over sized firing pin whole in the end of the bolt. Even the low pressure loads will show that crater. Don't worry about it. </div></div>

Another note to add is EVERY single ammo I've shoot through this rifle has the cratered primer. Ranging from the factory loaded American Eagle 7.62x51 168 gr OTM, Nosler 168 gr CC, my 40 gr load which clocked an avg of 2398 FPS all exhibited similar cratering. Except that the Nosler was the only one with gas leak and flattest primer.

I'll load up some very mild loads this weekend and have some pics of it.

I think the reason why the Nosler had the most pressure is because it is jammed into my rifling the most as well as a pretty warm load. The Nosler has a ogive length of 2.217'' while my + .010'' jammed load is 2.205''. According to TreSMon's guide, a jammed load should have the most pressure, which could explain why the Nosler showed more pressure than my loads while velocity were almost the same, despite using the heavier 175 gr SMK.

 

[psmith]

Re: Pressure signs?

Your reloads look a little hot but nothing that hasn't been done before. You might want to back down in case the weather gets a lot hotter and the gun might shoot a little better with slower loads.

I just got my gun back from SAC as well and Mark did a great job. Chamber is tight and the throat is a lot shorter than a stock remington, lol. I think my oal is around 2.790-2.795 and thats about .010 off the lands. I've noticed that the Bartleins are fast. I'm around 2750 or so with only 43.2 gr varget with a 1175 smk.

 

[phillik747]

Re: Pressure signs?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: psmith</div><div class="ubbcode-body">I'm around 2750 or so with only 43.2 gr varget with a <span style="font-weight: bold">1175 smk.</span> </div></div>

WOW that some crazy FPS your getting with that heavy bullet and such little powder combo!

Here is a really good read on working a load to find your rifle's max value:
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1713419#Post1713419

I have taken TresMon's whole writeup and converted it to PDF so I can print it out. If anyone want's a copy pm me.

 

[clmayfield]

Re: Pressure signs?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: damoncali</div><div class="ubbcode-body">There is no good reason to push pressure limits. Use a bigger cartridge if you want more velocity. Working past book max based on what your case looks like (or other "real pressure signs", whatever that means) is a stupid idea. There is literally nothing to gain, and a heck of a lot to lose.</div></div>

There is something to lose... an accurate node at a velocity that will keep you supersonic at 1,000.

Which book max should he use? The one published by the bulletsmith or the one by the powder manufacturer? They are likely different. Published loads are great for guidance when selecting charges to test, but the best bet is to always look for and know pressure signs. These can show up below book max as well as above book max depending on the chamber and bore.

My chamber is quite tight and I would blow my gun up if I used a load that others are using with no pressure signs at all.

The key is to work up slowly and proceed with caution, not to use the books as a Bible, because they clearly don't work that way.

On the above brass, I think they look OK. I think I see an extractor mark on one and an ejector mark on another. These won't show up well in photos, but are some of the best pressure indicators. The primers are some of the most unreliable pressure indicators, but most people use them anyway. Cratering is a perfect example. All of my primers crater to some extent. What I look for is how far the crater protrudes above the case head. If I turn the case sideways and see the crater flowing beyond the case head, I am at my pressure limit. That is a rough guide that works for my rifle, but may not work for every rifle.

 

[DBohn]

Re: Pressure signs?

Mordamer is right track when he says not to worry about the cratering. If you don't like that you can fix it with a bushing job.

I noticed you said the brass was once fired but was it fired in the gun you are shooting it in now? I have an Armalite .223 that with new Lapua brass loads I was piercing and flattening primers with minimum book loads. I didn't know what the hell was going on until I read around on this site and narrowed it down to a headspace problem. After using once fired brass from the same gun and bumping it back .002" those same loads were no where near over pressure. Check your headspace and see what the brass does after shooting it in that gun.

 

[clmayfield]

Re: Pressure signs?

BTW...

Here is a great link on pressure signs:
http://shootersforum.com/showthread.htm?t=58763

I won't reproduce it here, but I have ti saved on my hard drive. Very good stuff.