Pressure Signs from what should be a moderate load

[Former0302]

Relatively new to reloading (only about 3 years), but this load for .308 is flattening primers and occasionally creating a sticky bolt. This "should be" a moderate load, right?

OAL: 2.80
Powder: 45.5 gr of Varget
Brass: Lake City LR (two or three firings)
Primers: CCI-BR2
Bullet: 168 gr SMK

 

[UNRL Ghandi]

Re: Pressure Signs from what should be a moderate load

I was using Varget at 43.5 grains in my .308 and was getting good velocity out of it (2700 fps). I was using the CCI-BR2 with Federal Gold Medal brass and 175 SMKs. I ended up switching over to IMR 4064 and down to 43.3 grains. I'm getting 2750 out of it. My brother's gun (Tikka T3 .308 24" barrel) was only getting 2600 FPS out of the same load and we jumped his up to 45.0 grains in order to reach 2750 velocity. Started seeing some pressure signs at that load and moved it back down.

I'm still new to reloading too (2 years) so I'm stating this all as my own observations. Not sure if the difference in actions made a difference in the amount of pressure build up or not (Sako vs Surgeon), but when I was using Varget, a 45.5 grain load would have been too much for my .308.

By the way, I see you're from Baltimore County. I'm over in Howard. You ever shoot up at Hap Baker in Westminster at all?

 

[MtnCreek]

Re: Pressure Signs from what should be a moderate load

That's likely a hot load. You're near max and using brass that may have less capacity than typical commercial brass.

 

[Derek01]

Re: Pressure Signs from what should be a moderate load

I'm by no means an expert. Hodgdon lists 46.0 as a max compressed load for 168 SMK. Could be the LC brass. Thicker case, less capacity. Reaches higher pressure much sooner.

 

[roggom]

Re: Pressure Signs from what should be a moderate load

The max for Varget is 46.0C (per the Hodgdons online manual for 308W), the LC brass is 7.62 nato with thicker walls and less powder capacity. With the bullet seated to spec and the smaller internal capacity it may explain the pressure. Try backing down to the lower node (somewhere around 44.5-44.8) and give it a try.

Looks like I pushed the reply button too late.

 

[2Shots]

Re: Pressure Signs from what should be a moderate load

Most of the guys here run varget with 175's, I usually load 43.5 or 44 grains, you might just be a little hot for that case/chamber. You have to let the rifle decide what is hot, if I ran 45.5 in a thick wall brass like you are it would probably do the same thing. I would back down to 44 or so and maybe pick up some rem or win brass and see what they do.

 

[AZIROC]

Re: Pressure Signs from what should be a moderate load

I must be the only 1 using it, but I prefer XBR 8208 over Vargant

 

[RyeDaddy]

Re: Pressure Signs from what should be a moderate load

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZIROC</div><div class="ubbcode-body">I must be the only 1 using it, but I prefer XBR 8208 over Vargant</div></div>

No, you're not.

As to the original question: Your load is overpressure.

Hodgdon data shows 46.0 grains of Varget to be max. I wouldn't consider anything within 0.5 grains of that to be a moderate load. Hodgdon uses Winchester brass in their data, which has more capacity than Lake City. This, combined with your SAAMI compliant overall length (to a much lesser degree) has pressures in the red in my opinion. I would back the load down by AT LEAST 2.0 grains and start again with load development.

This may be elementary to you, but I'll put it out there anyway: primers may or may not be a reliable indicator of pressure for many reasons. However, sticky bolt IS a reliable warning, as is case head expansion. I use them to determine whether I'm over pressure. If the bolt sticks, back off the load. How are your primer pockets after firing this load? Loose? What kind of velocity are you getting with what barrel?

It's sometimes difficult to figure out what a reliable load is with all the data out there on the internet, especially with all the posts made by people that report reliability with loads above book max. Their rifle's chamber and throat length may enable them to go higher, but working up from less than book max is the only way to determine ehat is safe in YOUR rifle.

 

[Former0302]

Re: Pressure Signs from what should be a moderate load

Stopped shooting it, but was curious if it could be something besides too much powder.

I'll back it off. Hear you about the bolt not lying.

Velocity was measured at 2725-2750 fps though, which didn't seem like a significantly hot load out of a 24 inch barrel.

Thanks gents.

bk ghandi, yep I sometimes shoot over at Hap Bakers. Let my AGC membership run out at Marriotsville this year so that's my go to place usually. Don't get a chance to get there as much as I'd like though with 3 young kids.

 

[RyeDaddy]

Re: Pressure Signs from what should be a moderate load

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: former0302</div><div class="ubbcode-body">

Velocity was measured at 2725-2750 fps though, which didn't seem like a significantly hot load out of a 24 inch barrel.

</div></div>

Hmmm... Seems high, but not TOTALLY unreasonable. I was expecting you to say something like 2800 fps. Every rifle is under it's own rules though. Have you shot any lower loadings in the same brass while working up or did you just pick a load and it worked so you stuck with it?Everybody's done this at least once I think, especially when new at reloading. Not that I'm an expert, but I'm curious about whether it could be oversized brass causing the issue. I've not run into that, but just a thought.

Factory chamber or is it a custom barrel?

 

[RotARy15]

Re: Pressure Signs from what should be a moderate load

Every rifle is different. I get 2800 out of 175 SMK's over 45.0 of Varget in Winchester brass with CCI 200's. Savage 10 FCP-K 24 inch.

Post number 308 FTW!

 

[Former0302]

Re: Pressure Signs from what should be a moderate load

I worked up from 42 grains, in .5 grain increments and things tightened up there.

The load was flattening primers but otherwise was working fine for a while, but the last time out (earlier in the summer) got the sticky bolt. Perhaps temp difference tipped me over the edge, but didn't think Varget was that sensitive. Maybe I was just on the tipping point.

Custom barrel, from a Tactical Rifles build (I know, I know...if I knew then what I've learned now..., it does shoot really well though)

I did just recently anneal the brass though. Thought I was careful to not cook it too long, but maybe too much?

 

[MtnCreek]

Re: Pressure Signs from what should be a moderate load

Take a piece of fired brass (un-sized) and put a bullet in it. Does it fit tight or slide in easy?

 

[Raider Power]

Re: Pressure Signs from what should be a moderate load

I've shot Winchester and LC brass through my AAC-SD and saw very little difference in pressure signs between the two cases. My final loads were usually identical powder charges. For example, 44.5 grains of Varget behind a 178 grain AMAX produced the best load for both cases. While this is not a maximum charge, it's close. From my experience, when you get close to max, things can change quickly.

This is not .308 related, but it was a good reminder to follow sound load work up procedures because you never know exactly how a given load will work. A while back I was working up a practice load for my .40 s&w and wanted to try to the 135 grain Nosler JHPs. I started with the minimum charge listed for whatever powder I was using and worked up to max. When I went out to shoot, the starting charge peoduced recoil that seemed a good bit heavier than anticipated. When I looked at the cases, there were some obvious signs of max loads. I thought this can't be right so I tried the next step up. The cases showed even more pressure signs so I stopped there an decicded to go another route. When I tried the 150 grain noslers in the same gun, I got all the way to max with no excessive pressure signs. Morale of the story, start slow and work up carefully, you never know when you'll hit a combo you gun thinks is too hot.

 

[UNRL Ghandi]

Re: Pressure Signs from what should be a moderate load

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MtnCreek</div><div class="ubbcode-body">Take a piece of fired brass (un-sized) and put a bullet in it. Does it fit tight or slide in easy? </div></div>

MtnCreek, what does this test prove, I'm curious? Hadn't seen this recommended before. The looser fit would show too much pressure?

 

[Greg Langelius *]

Re: Pressure Signs from what should be a moderate load

I think the load would be peppy with commercial brass, and maybe too peppy with MilSpec brass, with case capacity being the denominator.

Otherwise, when pressures are unexpectedly higher, the first thing I look at is case length, with neck length trimming in mind.

My load is 175SMK at 2.815" OAL, Rem .308 brass, 42.2gr of IMR-4064, and a decent Large Rifle Match primer. Some will load more 4064, but I consider this to be as close to max as I'd like to go. Ths load is specifically intended to reach 1000yd supersonic out of an M1A/M14, but it works well in a variety of rifles, including blt guns.

Greg

 

[MtnCreek]

Re: Pressure Signs from what should be a moderate load


<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Originally Posted By: MtnCreekTake a piece of fired brass (un-sized) and put a bullet in it. Does it fit tight or slide in easy?

MtnCreek, what does this test prove, I'm curious? Hadn't seen this recommended before. The looser fit would show too much pressure?</div></div>

Loose fit would be normal. If the fit was tight, the chamber is too tight for the brass or the brass is too thick for the chamber.

The chamber could be out of spec or it could be a custom 'tight neck'. If this is the case, either the chamber neck area needs work or the brass needs turning.

Too tight a fit can also be caused from forming brass from another, larger cartridge.

 

[Former0302]

Re: Pressure Signs from what should be a moderate load

Bullet slides into a fired / unsized case easily.

 

[s4b1106]

Re: Pressure Signs from what should be a moderate load

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

Originally Posted By: MtnCreekTake a piece of fired brass (un-sized) and put a bullet in it. Does it fit tight or slide in easy?

Too tight a fit can also be caused from forming brass from another, larger cartridge. </div></div>

Been there, done that. In college, really poor, (yeah, who isn't) resized 30-06 mil brass to 270 win. Dad said ya could! He didn't know about neck thickness, though. Blew the ejector on my Rem 760. Lesson learned.