308 gas gun loading

[mic2377]

I would be very surprised if the Sierra 155's don't shoot well for you, especially the 2155's. A very forgiving bullet. I have a shot a bunch of those through my rifles, and they seem to shoot very well across all of them with really no load tuning. The BC isn't the best but they work just fine out to the 700 yard range. They are also lower recoil.

I haven't commented on powders before, but I prefer IMR/VV extruded powders for moderate AR loads. Compared to Varget, or many ball powders, they still shoot well at lower nodes, and I feel the lower nodes are more forgiving as well. They don't need to be loaded all the way to MAX to get food accuracy.

Many of the other posters have already corroborated these findings, good luck on your next round of loads.

 

[kevinbritvec]

I attached a pressure test comparison using Lake City brass and maximum loads of IMR-4895 with 168 grain SMK's. Changing primers and brands of brass can change peak pressures considerably.



I started reloading .308 for NRA high power tournaments in 1984. I have never needed small base dies, instead I bump my shoulders -.003" from the fired measurements and polish the expander ball to achieve .003" of neck tension to hold the bullets in place. I never crimp.

Your loads are too hot IMO by at least 1.0 full grain of powder. I look at 2500 to 2550 fps from a 20"-barrel shooting 168/175 grain bullets as being maximum from a semi-auto. That would compare to 2600 to 2650 fps from a 24" bolt action. The velocities posted above were fired from a 24"-barrel universal test receiver.

It's normal to subtract 25 fps for each inch your barrel is shorter than the tested barrel. BTW-Federal brass isn't well suited for use in a semi-auto rifle, it's soft and won't hold up to very many reloads. Because it's soft, I use Lake City data when reloading it.

 

[kevinbritvec]

I am currently using 41.5 grains of N150 in Lake City or IMI 7.62x51mm brass under 168 grain SMK's to good effect in my semi-autos and bolt action rifles. I would start there in Federal brass and work higher.

 

[jlorenzo]

I attached a pressure test comparison using Lake City brass and maximum loads of IMR-4895 with 168 grain SMK's. Changing primers and brands of brass can change peak pressures considerably.

View attachment 1655463

I started reloading .308 for NRA high power tournaments in 1984. I have never needed small base dies, instead I bump my shoulders -.003" from the fired measurements and polish the expander ball to achieve .003" of neck tension to hold the bullets in place. I never crimp.

Your loads are too hot IMO by at least 1.0 full grain of powder. I look at 2500 to 2550 fps from a 20"-barrel shooting 168/175 grain bullets as being maximum from a semi-auto. That would compare to 2600 to 2650 fps from a 24" bolt action. The velocities posted above were fired from a 24"-barrel universal test receiver.

It's normal to subtract 25 fps for each inch your barrel is shorter than the tested barrel. BTW-Federal brass isn't well suited for use in a semi-auto rifle, it's soft and won't hold up to very many reloads. Because it's soft, I use Lake City data when reloading it.

View attachment 1655475

Thanks for all the info. What speed would you be looking for with 150gr bullets out of a 20" gas gun?

 

[kevinbritvec]

2600 fps to 2650 fps would be prudent IMO.

 

[mac86951]

i just measured 2730 with a 147 from a 20" barrel using 45.0 wc846 at 6800ft elevation. not a good choice its a scatter gun pattern, but functioned and needs more dial in. I'm switching to 4064 powder next for what i hope is 2MOA or better, but generic FMJ, dont hold your breath.

 

[danny]

I started reloading .308 for NRA high power tournaments in 1984. I have never needed small base dies, instead I bump my shoulders -.003" from the fired measurements and polish the expander ball to achieve .003" of neck tension to hold the bullets in place. I never crimp.

Thanks for the good posting. Your experience mirrors mine, but there can be exceptions, sometimes. I have never needed a small base die for my Garands, AR 15s and M14 clones, except for once. I had a lot of once fired brass from Jeff Bartlett (probably machine gun fired) that was not sufficiently sized for an M1A SuperMatch I have. I don't know why people are spreading rumors that if you have a self loader, it automatically means you need small base dies. It is just not true, except for when it is, and that is rarely.

Danny

 

[jlorenzo]

Some results with the 150gr Hornady fmj and Ramshot Tac, best powder so far with these bullets. I see some promise. Will try more 43gr and I think I'll have a nice cheap plinking load.
Also want to try IMR 4895 but prefer a ball powder for throwing.

Also on the subject of small base dies, I saw Johnnie's Reloading bench on youtube stick a case in the exact same Krieger barrel, bolt and upper I have. I then tested a sized piece of brass will my regular FL die, (.004" shoulder bump) it was indeed harder to eject with the charging handle, definitely was sticking in there a bit.

I did NOT want to deal with this on a 800$ barrel.