308win load trouble @ 300 rds down the tube

[Miyka-el]

Tried Varget, 4064, CFE 223, Benchmark, H322 and I found that none compared to IMR 8208 XBR for consistency, plus temp insensitive. It's my go to powder! A little pic of a load dev I did for a friend's Savage Palma with 8208 XBR, 155 Amax

Needless to say, he was impressed...almost 1/5 MOA at 100m

 

[liltank]

Another powder you may want to try is Power Pro 2000MR. It is a good powder for heavier bullets for .308. RL17 will definitely get you in the higher velocity range. I think Varget and RL15 are a little too fast for the 208 in the .308.

 

[eric32]

you didn't by chance shoot your cold bore through the chrony screens did you? I usually send a couple down range first before I send them through the screens. that will throw things off otherwise

i zeroed the rifle with about 10 shots just to confirm at 300 yards. then strapped my magneto speed on so i dont have to hassle with any screens.

I cant find any other powders in my area and online orders are just about impossible with the gun frenzy i am going to try and drop half a grain and work up agian maybe with the temp swing it will be as easy as that. then use the barrel tuner for the groups

Could a seating depth help the ES spread as well i could just tune that.

Another powder you may want to try is Power Pro 2000MR. It is a good powder for heavier bullets for .308. RL17 will definitely get you in the higher velocity range. I think Varget and RL15 are a little too fast for the 208 in the .308.

but if i ever to get my hands on the power pro 2000MR i will try some

 

[amlevin]

You will find that during the COOL to COLD months where there is a high pressure system (low humidity) IMR 4064 works GREAT... But start heading towards a humid summer and you need an "extreme" powder... Varget or even RL-15 would be my lick AND in that order... I hope this helps..

If this is true then why has the Military gone to IMR-4064 for it's MK316 Mod 0 "Sniper Round"? Temperature stability was one of the criteria for the testing/acceptance. Not Varget or RL-15, but another Hodgdon product IMR-4064

According to "insiders" the "build" for the MK316 Mod 0 round is 41.7 gr IMR-4064 in a Federal Case, a 210M primer, and a 175gr SMK.

I'm loading the Nosler Custom Comp instead of the SMK with 42.5 gr of IMR-4064 and shooting 1/2 MOA at 300 yards from my 5-R Milspec. Thursday's range outing resulted in a nice neat little 3/8" group at 200 yards.

As for Humidity/Temp, I've shot this load in the "teens" and also in the "70's" with no perceptible change in accuracy. I'm almost afraid to chrono the load for fear it will reveal that this combination is no darn good 8) On the not of a chronograph, I expect to see mine again someday. It's been living at the PACT factory for the last several months awaiting warranty repair. They don't seem to be too anxious to repair it and return it.

 

[liltank]

Seating depth will effect your ES. I would try setting them about .010"-.015" off the lands. That has been an optimal seating depth for all of my load development and tighter ES numbers.

 

[thefitter]

I don't think the small velocity change is that unusual for that temp change. And I believe the ES is off because the velocity change. I think you should try and match the original velocity by dropping the charge just a tad and see if the ES comes down.

Another question- how often have you been cleaning the barrel?

 

[Gman]

You will find that during the COOL to COLD months where there is a high pressure system (low humidity) IMR 4064 works GREAT... But start heading towards a humid summer and you need an "extreme" powder... Varget or even RL-15 would be my lick AND in that order... I hope this helps..

If this is true then why has the Military gone to IMR-4064 for it's MK316 Mod 0 "Sniper Round"? Temperature stability was one of the criteria for the testing/acceptance. Not Varget or RL-15, but another Hodgdon product IMR-4064

According to "insiders" the "build" for the MK316 Mod 0 round is 41.7 gr IMR-4064 in a Federal Case, a 210M primer, and a 175gr SMK.

I'm loading the Nosler Custom Comp instead of the SMK with 42.5 gr of IMR-4064 and shooting 1/2 MOA at 300 yards from my 5-R Milspec. Thursday's range outing resulted in a nice neat little 3/8" group at 200 yards.

As for Humidity/Temp, I've shot this load in the "teens" and also in the "70's" with no perceptible change in accuracy. I'm almost afraid to chrono the load for fear it will reveal that this combination is no darn good 8) On the not of a chronograph, I expect to see mine again someday. It's been living at the PACT factory for the last several months awaiting warranty repair. They don't seem to be too anxious to repair it and return it.

I agree with the Pact comment. I sent my chrono to them 2 years ago, and it took 7 months to get it back.

 

[cmillard]

to be honest, I don't buy into that whole temp insensitivity crap. supposedly, there is little variation with hodgdon powders in the broad temp changes. to be honest, I think this is hogwash. if you take some loaded ammo, split it in half and put half in the deep freeze over night and let the other stuff bake in the 90 degree sun for a while, there is going to be a major shift in velocity when you shoot it. I think this is true for all powders. but, this is just my opinion

 

[eric32]

I am sorry but just because the military picks a product to use as there own doesn't mean a whole lot. i am in the military and some of the stuff we buy and use doesn't make a whole lot of sense since there are products out their with half the cost and twice the productivity. But i am not as they say " A Big Picture kinda guy "

I did notice something very strange was i was reseating my ammo a rather loud pop was happening when push further down into the case

As to seating depth goes i have re-seated all my ammo to

@ the lands

.10thou jump

.20 thou jump

all with 41.0 gr of 4064 and WLR primer i hope i find something suitable to use in competition as the regional match at Blakely,GA is 1 week away.

 

[chuckbuster243]

I have never heard a pop on any ammo when reseating other than the military ammo that has the black sealant on it.... Thats an odd thing, the bullet may have cold welded in the case... Or allot of neck tension... You got us wondering thats for sure. My Criterion sped up very little after break in, around 25-50 fps.... On a side not have fun in Blakely I am planning on shooting it. Hopefully both days if I can find somebody to split a cabin with. Matt

 

[eric32]

the POP was one some bullets and not others like i said the ammo was sitting for well over a month or so. but If this seating tests turns out a ES lower then 20FPS ill be there 100% in force

 

[jlow]

to be honest, I don't buy into that whole temp insensitivity crap. supposedly, there is little variation with hodgdon powders in the broad temp changes. to be honest, I think this is hogwash. if you take some loaded ammo, split it in half and put half in the deep freeze over night and let the other stuff bake in the 90 degree sun for a while, there is going to be a major shift in velocity when you shoot it. I think this is true for all powders. but, this is just my opinion

This whole temperature sensitivity thing is more complex than simple air temperature.

The reason I say this is because when it gets hot, not only does air temperature directly affect the temperature of the powder but it has a huge indirect effect. What happens is when it is hot outside, your chamber and barrel cools down much slower and depending on how many rounds you have just fired and how long you leave that round in your chamber before you fire it, it can heat up to temps much much higher than the air.

When the air temps is cold, this is less of a problem but when it is hot – big problem especially if you don’t “cook” the round consistently. An extreme example of this is when a round is left in the chamber of a machine gun that has undergone sustain fire, the chamber is hot enough to “cook” off the round.

And "oh no" not the "pop" thing again! ;D

 

[ARIZONA_F_CLASS]

I use Varget which is one of the best powders for temp changes. But if you want see a load act up, shoot 10 rounds then put a round in the chamber , close the bolt and wait about 10 seconds then fire. The pressure will be higher!

Temperature changes do matter. Especially if you have a great load.

 

[jlow]

+1

 

[eric32]

i would love to use Varget if it wasn't as hard to find as BIG FOOT!

 

[ARIZONA_F_CLASS]

Eric, keep an eye on Powdervalley and Bruno's. Powder valley just had some but sold out in about 8 hours. Bruno's has had it pretty regularly lately.

 

[eric32]

i found a place that might have it by the end of the week but ill keep my fingers crossed

 

[broncman]

Not sure where you live, but I know if several places in western North Carolina that had varget in stock as of last week.

If you dont believe temps makes a difference, shoot about ten rounds over a chrony, then let one set in chamber for about 20-30 seconds. See what that does to your es/sd.......

 

[eric32]

i dont doubt anyone that says if you leave the round in the chamber it will heat up thus have more pressure and throw off your barrel node.

No i live no where near western NC wish i did.

 

[dickn52]

Same Chrony. I know you said you had a magneto, but is it what you used originally?