Pressure Diagnosis Please: Varget + 155 Scenars

03psd

03psd

Sergeant
Full Member
Minuteman
May 27, 2006
567
33
Oklahoma
#1
Tried to improve on my past performance of this same load but had some pressure signs I need help diagnosing.

Rifle is a 700 LTR.
Load is 47.5 gr Varget
155gr Scenar
Federal Brass
CCI 200 Primer
2.935" COAL

This load at 2.905" performed well on a 70* day. Today loaded longer and 40* was 1" plus and bolt lifts where slightly heavy, not bad by any means but a little heavy. Some brass showed pressure signs from the ejector, others did not. the primers also appear cratered.

So what gives? Is my quest to load them as long as possible into the never ending Remington throat causing the problem, or was it the temperature, or was it I am up above the maximum my rifle will shoot well in terms of powder.

Thanks in advance for any input.

DSC03397.jpg
 
#2
Re: Pressure Diagnosis Please: Varget + 155 Scenars

You can clearly see the pressure sign on the case on the right with the obvious extractor mark. I load mine at 47.4 grains and 2.910". With this much Varget, we are at the ceiling end of the powder curve. When you start pushing it into the lands, that's going to drive the pressure up. Don't know how hot it gets in the summer time where you are, but you may have problem with that in the summer time. I would probably back out the lands a bit without sacrifying accuracy to be safe. FWIW, for me loading it long so I can get the accuracy I want rather than anything else. Certain bullets, such as the Berger VLD, you need to ram them into the lands, but Scenars you don't have to do that.
Stay safe.
 
#3
Re: Pressure Diagnosis Please: Varget + 155 Scenars

Without knowing much else, I'd say it was the loading longer that increased the pressure. A 30* DROP in temp will reduce (DROP)pressure not increase it. How far into the lands are you at this tested OAL vs. your OAL before?

Have you tested this load in 90+* temps with the original seating depth to be safe during the warmer months?

Don't get me wrong my Scenar/Varget load is at 47.7gr so I'm not insinuating that you haven't tested. Just something to think about when temps get around 90 or above. We're clearly running above published max loads and really warm temps are where the pressure has a chance to increase greatly even with everything else remaining exactly the same. I know of several other folks here running well above max with Varget and 155 scenars - IIRC the highest I saw was 47.8gr without pressure signs, but I don't think their seating was quite as long as yours.
 
#4
Re: Pressure Diagnosis Please: Varget + 155 Scenars

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mavrick10_2000</div><div class="ubbcode-body">Without knowing much else, I'd say it was the loading longer that increased the pressure. A 30* DROP in temp will reduce (DROP)pressure not increase it. How far into the lands are you at this tested OAL vs. your OAL before?

Have you tested this load in 90+* temps with the original seating depth to be safe during the warmer months?

Don't get me wrong my Scenar/Varget load is at 47.7gr so I'm not insinuating that you haven't tested. Just something to think about when temps get around 90 or above. We're clearly running above published max loads and really warm temps are where the pressure has a chance to increase greatly even with everything else remaining exactly the same. I know of several other folks here running well above max with Varget and 155 scenars - IIRC the highest I saw was 47.8gr without pressure signs, but I don't think their seating was quite as long as yours. </div></div>

No, havent tried this load in the heat of the summer. I dont think I am into the lands at this length. It must be damn close though! I only tried this length because my seating die was set up for 168gr SMK and at its current adjustment it seats them at a hair over 2.905. I wanted to try the Scenars longer so I tried one with the SMK die adjustment and got 2.935". the round chambered without a problems so I gave it a shot.

I agree, I think its the length. But am confused by the "jump" issue. I know some bullets tolerate a larger jump but with that logic, a shorter jump would be preferable with any bullet. I think I have a very samll jump with this load and in addition to pressure signs, my accuracy went to shit.
 
#5
Re: Pressure Diagnosis Please: Varget + 155 Scenars

Here's some data from the Hogdon powder home site.

155 GR. SIE HPBT Hodgdon Varget .308" 2.775" 44.0 2759 41,300 CUP 47.0C 2909 49,400 CUP

You're shooting over the listed max powder charge and over the listed length. Your case head is showing pressure signs. Any time I have pressures strong enough to leave marks where the ejector was and a clean swipe behind it, I back off. I would advise you to back off the length a bit first. If it still shows ejector "swipe" back down on the charge.

But as always, it's your rifle and your choices. Do as you wish. All I can do is offer an opinion.
 
#7
Re: Pressure Diagnosis Please: Varget + 155 Scenars

In my opinion, The pressure is not overly high, in my opinion.

This opinion is based on the roundness of the primer caps in the primer pocket. Yes, there is ejector wipe on the case, however, remember these are Remmington cases. I suspect that these marks will go away with Winchester or Lapua cases. In any event, you are close to the edge of sane pressures, and with the Rem brass likely too close.

Also, in my opinion, depending on how you determined the length of the throat, shooting at 40dF can cause the chamber to shorten so the first several shots may actually be at the lands instead of 0.010 from the lands you expected. This could push the pressure higher than expected in cold weather and result in the marks on the cases.
 
#9
Re: Pressure Diagnosis Please: Varget + 155 Scenars

Diff books give you diff max charges. My Nosler book list win brass, 48.5grs of Varget and 150/155gr bullets in a Lilja barrel which I know has a shorter throat then my remington, doesn't everything? I have my bullet set out pretty far also and I am not into the lands yet. I am using the 48.5grs of powder right now and I am showing no pressure signs. I need to try this load in the summer time to make sure it doesn't spike on me but I would try to set the bullet back in the case a bit before I worry about backing off the charge yet. If it still gives you problems, then back off of the charge a little. Also some brass is softer than other brass and this could also be the reason you are seeing extractor marks.
 
#10
Re: Pressure Diagnosis Please: Varget + 155 Scenars

Shit can that Fed brass, its really soft, thats one big reason FGMM shots so good, but there brass sucks for reloading, get some Winchester or Lapua and redo your load development.
 
#11
Re: Pressure Diagnosis Please: Varget + 155 Scenars

Quickload says that load is about 62,400 PSI at 74 degrees. At 100 Degrees, the pressure goes up to 65,488 PSI. Ad about 7k PSI for seating on the lands per OL.

Be careful with that load. not much room for error
 
#12
Re: Pressure Diagnosis Please: Varget + 155 Scenars

ditto on shit canning the FC brass. I had the same problem until I got some Lapua brass and am now running load much higher with no pressure signs and better results.

(hint: check Dan Newberry's OCW site for charge beta and load just under mag length)
 
#14
Re: Pressure Diagnosis Please: Varget + 155 Scenars

Several years back when Hodgdon began their 'Extreme' product promotion, they charted the temp vs velocity data for Varget. There was a small but significant <span style="font-style: italic">increase</span> in velocity as temperatures dropped significantly.

Loading heavier charges than published max, one should expect pressure issues, especially if other factors are modified in favor of higher pressures

Decreasing/eliminating jump will normally steepen pressure curves and escalate peaks.

Any one of these circumstances, by itself, could explain an emergent pressure issue. Taken together, they paint a mental image of the Dragon's Tail being twisted.

Referencing prior experience with the load, one surmises that this is not new brass. Case length growth would be expected. This one can sneak up on you if you're not watching for it. If the case neck gets overly long, it can curtail bullet release, spiking pressures. If any of the loads exhibited bolt drag while <span style="font-style: italic">closing</span>, I'd consider that condition to be significant to this issue.

Greg
 
#15
Re: Pressure Diagnosis Please: Varget + 155 Scenars

I think you have three issues here.
1. As others have said Federal brass is known to be soft in the head area. Try other brass.
2. In my experience I have come to the conclusion that jamming bullet into lands does not help the situation and running max loads to achieve a velocity window above the case design is not desirable.
3. Although not a perfect indicator of pressure the primers do show reverse striker movement during the rise of the pressure curve.
This can be caused by two things, over pressure loads and tired striker spring. I talked to a Remmy engineer two weeks ago and he told me they had relaxed their striker indent to go along with the SAAMI "standards" of .016" striker indent on COPPER. The old standard was .020" indent on copper. I really like to see energy up in the .022+ range.
Note: The indent on the primer has no relation to the actual energy imparted on it and cannot be relied up to determine striker energy.
I had the same scenario with a Remmy 7615 about two years back and this same problem exhibited itself among others (bore that had a wondering bore line so crooked I could not sight it in at 100 yards trying 3 scopes to do so.)and thusly I sent it back.

I advised striker energy was too low and they did nothing about it. I was getting this condition on MILSPEC primers and that is extremely serious as I knew the load was not max.

I ordered hammer springs from Wolff Springs, replaced the hammer spring and problem went away immediately as the new spring gave a much heavier striker energy. Wolff makes three spring strengths for Remington actions. Factory and two above that. I would go with either of the "higher energy" springs. If you like Remmys it is cheaper to get a dozen "bulk pack". I suspect when you pull the bolt down to change springs you will find the "issue" spring has become shorter in a unconfined condition.

Some long range competition shooters install new striker springs at the start of each season. If you do install new striker spring measure the free length with caliper and record it in your data book. At end of season pull down bolt and remeasure ans see if it has become shorter. Spring engineers will tell you a properly made spring will never take a set, only problem is the only way to determine this is to measure free length or energy after use.

If you continue to shoot it as is--you are border line to having a blanked primer which means there will be a separation at the little raised portion around the striker indent allowing a disc of primer material to become dislodged.
This may or may not result damage(flame cutting) to striker nose, gas down striker tunnel and may result in the little disc becoming lodged in the striker tunnel where it may cause misfires due to jamming the striker movement. It is somewhat rare but I have seen it about three times and they can be a real pain to remove.
 
#16
Re: Pressure Diagnosis Please: Varget + 155 Scenars

great information all.

To clarify and answer some questions.

1. The brass is 1x fired FL sized and trimmed to 2.005"
2. The firing pin assembley is brand new PGT (Pacific Guage & Tool) installed by AZ Precision when he did the bolt knob.
3. While I am not the original owner of the rifle I am sure the hammer springs are original. I will look into getting a stiffer spring.
 
#19
Re: Pressure Diagnosis Please: Varget + 155 Scenars

is this a trick question??

I follow the directions. raise the shell holder to its highest point. thread in the die till it contacts it. lower the shell holder. screw in the dies 3/8 - 1/4 more turn to take the slop out of the turret. decapper hanging about 1/8" out of the bottom of the die.
 
#21
Re: Pressure Diagnosis Please: Varget + 155 Scenars

Whats wrong with Fed brass?

Is it only bad for max loads?

I've got a bunch of loadings on mine, but I don't push my loads either.
 
#22
Re: Pressure Diagnosis Please: Varget + 155 Scenars

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jdgray</div><div class="ubbcode-body">Whats wrong with Fed brass?

Is it only bad for max loads?

I've got a bunch of loadings on mine, but I don't push my loads either. </div></div>

Yeah, I dont get the brass thing either.I will agree that it is soft but if we can agree that the brass is a fusable link of sorts, why would you want brass that hides pressure signs. Not seeing them doesnt mean they arent there. It would seem to me that you would want to know when you are pushing the maximum versus have that fact remain hidden and have something else go arye.

I may be completely off base on this and welcome correction.
 
#24
Re: Pressure Diagnosis Please: Varget + 155 Scenars

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308sako</div><div class="ubbcode-body">03psd, You make a good point about the fuseable link aspect, but most (me included) would argue that the setting for the fuse is too low. Meaning that "pressure signs" are shown before dangerous over pressures are reached. I would prefer that my brass, primer and bolt lift all send me the same "signals" as pressure approachs a level where a prudent reloader knows the limit has been reached.

Mostly I have found Federal brass accurate and reusable for milder loads and in some cases good in other calibers. </div></div>

This makes perfect sense now.

Thanks
 
#25
Re: Pressure Diagnosis Please: Varget + 155 Scenars

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308sako</div><div class="ubbcode-body">03psd, [snip] "pressure signs" are shown before dangerous over pressures are reached.</div></div>
Please define "dangerous over pressures".

Heck, please define what you think is a "safe" over pressure situation.

Just curious about how far you are willing to venture into the safety margin of the brass. Typically, that's the weak link, or the primer. Rifles are much harder to blow, absent a metallurgical problem.
 
#26
Re: Pressure Diagnosis Please: Varget + 155 Scenars

The problem in case, 155 Scenars like to be pushed hard, very hard, Fed brass is not at all the best choice for hot loads, a 175 going 2650 would be fine, a 155 going 2950+ is hard on brass, hard on primers, Lapua is a far better choice in this case.
 
#27
Re: Pressure Diagnosis Please: Varget + 155 Scenars

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308sako</div><div class="ubbcode-body">

The reason this question is being asked is that you may be creating too much headspace. I would strongly recomend the redneck method of headspace verification: Take a round and fired .40 S&W case and knock out the primer, invert and put over the mouth of a fired .308 case and measure the total length. </div></div>

Or spring for this Hornady Lock N Load headspace tool
 
#30
Re: Pressure Diagnosis Please: Varget + 155 Scenars

There is no point in running the Scenars if you can't run them at 2900 or more. If you can't get the performance out of them, they have no redeeming qualities.

My max so far has been 47 grains, which gave a mean of 2899 out of my factory 24" tube in LC brass at about 2.895".
 
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