308 Win 168gr ELDM w/ H4895 Pressure signs

[zekepa]

Working on a load for 168gr ELD-M for T3x 308’s 20” Superlite and 16” Lite, using H4985. All shots suppressed AB Raptor10 w/5” reflex.

Loaded 10 at 43 gr H4895 COAL 2.8 Once fired LC15 brass

Shot them yesterday from the 20” T3x, temp around 70. Avg 2725fps had some flattened primers and ejector swipes on the cases, not all of them but some.

Hornady max load data list 2600 fps with 43.3 gr H4895. I was expecting somewhere around the 2600 fps but ended up 125fps faster.



Today loaded 20 at 42.3 gr H4895 was expecting around 2675 fps with the 20” T3x.

20” T3x 10 shot avg 2694

16” T3x 10 shot avg 2601

Weather today was similar temp to yesterday but more humidity. All 20 cases have ejector swipes with a couple of heavy bolt lifts.



I’m wondering if the AB Raptor 10 is somehow contributing to higher Velocity/ Pressure than expected. I didn’t think of it till on the way home from the range to shoot any of the rounds unsuppressed to check for velocity/pressure. Anyone else ever experience early pressure signs due to suppressor? I do know LC cases have less capacity than others, but still wasn’t expecting the pressure signs at 1 gr below max.



Going to drop down to 41.7 gr H4895 to see how that works.

 

[Sponge]

That does seem warm. Generally I will load to book max velocity, taking into account barrel length differences.
I would suggest measuring case H20 capacity and comparing to others, if you have some fired Hornady brass from your rifle even better- compare your LC case capacity to Hornady (Hornady generally used their brass for their load data)

Unsure about the suppressor.

With 168 ELDM, 41.0 of H4895 in virgin Starline I got 2571 from a 22" Sauer (which has tended towards being a little slow overall).

Gordons Reloading Tool is also useful, but measuring the H2O capacity of your fired cases is important.
With my load, my fired case capacity, my rifle's velocity - GRT predicts 43 gr H4895 would be safe pressure (58,900 PSI) and about 2690 fps.

 

[PopNFresh]

+1 vote for the brass, mil brass is probably thicker than what they did in their book, general advice is load down 10%ish when using thicker mil brass

 

[zekepa]

checked the H2O capacity for a LC15 and a Hornady round from a factory loaded 165gr interlock,

LC15 54.9
Hornady 54.4

Factory round 165gr interlock American whitetail was 2600 fps on Garmin for my 20" T3x with Raptor 10, box advertised as 2700 with 24" barrel

 

[pyratio]

My good friend made the mistake of offering to help me do load development for my 16" Sawtooth in 308. Boy oh boy has it been challenging. Initially he was going for velocity but that short barrel really limits speeds down to 2600fps or lower. We're dabbling in benchrest right now so we switched gears to find ideal SD and ES, then test seating depth to see if we can get below 0.5 moa. We started with Varget but have since learned 4064 and 4895 are some of the more preferred powders for short barreled 308s.

I have heard that the 4895 burns faster and is ideal for "shorter" barrels.. shorter than 24" that is so I've been itching to try that. We chanced upon testing PMC X-tac Match in 308 and shot amazing groups with that. 0.26 to 0.4moa. Consequently we decided to use the same bullets in our load development which are Sierra Match Kings 2200. I've recently picked up the AB raptor 8stack with 3 inch reflex and love what it does in reduction to concussion, recoil and even reducing barrel whip. Groups are tight. We found a 0.46moa node but the SD and ES aren't the best at 42gr flat. Trying to follow Erik Cortina's advice on focusing on ideal SD and ES instead of chasing lands, we went with 43.3gr which gave us single digit SD and ES. First seating depth testing will be done at the next match. At its worst I was getting 0.96moa. If we can't get close to 0.5moa we'll be switching gears and doing more load developments in the 42gr increments.

I can't say I've noticed an increase in fps since I switched off of my old Griffin Bushwhacker 46 to the AB raptor. We have loaded varget up to 44gr with no pressure or primer issues. But that 4895 is burning hotter and faster. If you were local to Austin, TX I'd suggest we try trading a pound of varget for you to test with for a pound of 4895. Are you loading for hunting or for matches?

 

[Sponge]

Well, that largely debunks that case capacity theory. Lower than advertised velocity for Hornady ammo doesn't surprise me.

How confident are you in your powder charges? Are you verifying your scale with check weights?

 

[zekepa]

Well, that largely debunks that case capacity theory. Lower than advertised velocity for Hornady ammo doesn't surprise me.

How confident are you in your powder charges? Are you verifying your scale with check weights?

The scale was my first suspect. I had 10 rounds loaded at 42.6 to try if the 42.3 were too slow. I obviously didn't shoot them after the pressure signs on the 42.3 rounds.

When I got home from the range, I calibrated the scale using the check weights and weighed the charges from those rounds. 9 weighed 42.6 the other was 42.5.

I have a balance beam scale around somewhere but I haven't taken the time to compare the two scales.

I mentioned the factory Hornady ammo just as a reference to what fps I should probably expect with reloads using 168 ELDMs

Appreciate the responses.

 

[zekepa]

Verified the my digital scale RCBS Rangemaster 750 with a balance beam scale. Spot on at 40 grs.

Shot 5 rounds loaded with 41.7gr H4895 avg was 2650, still some slight ejector swipe.

Going to try 41gr to see if I can get close to 2600fps