Ever get into a polite disagreement with someone who really should be old enough to know better?
This guy, clearly a man of enough years to have reloaded a few rounds, handled a few rifles, and should be some sort of tribal silverback of wisdom.
Instead, we get this:
The context is that a group member was trying to put together a 308 Win 110 grain load using H335 and was wondering why he was getting popped primers and having extraction issues with his semi-auto 308 rifle.
The issue is pretty simple, the max pressure for H335 even at max load is below the standard 50k CUP that most semi-auto 308 Win rifles are designed to function properly. In short, the “max velocity with lowest pressure” wisdom for long range shooting wasn’t helping out the original poster because as the bullet passed the gas port it likely had a bunch of H335 still burning in the bore trying to build pressure and then getting a pressure outlet from the gas port. Which means the brass swelled enough to grip the chamber, but not enough to push back against the bolt face, so the primer pushed out as far as it could and when the still burning powder added pressure to the gas port, started the bolt unlock sequence.
The only other possible explanation would be a secondary explosive event (SEE), but there were no other symptoms reported, so likely it is just low pressure with a too slow powder.
So it was recommend either IMR 4198 or H4198 because it will shift the bulk of the burning to before the gas port, and cause the correct “pressure curve” to make the rifle function. Seem like a reasonable suggestion given the symptoms reported.
With that, Mr. Kester Price inserts his opinion that H4895 is a better option, despite H4895 having essentially the exact same pressures has H335 because they are very similar in burn rate (although NOT similar in temperature sensitivity) although H4895 is listed as even slower by a few ticks than H335.
When you are reloading for a semi-auto, burn rate is very important.
Here’s a cut from the Hogdon Burn Rate chart showing the partial “sweet spot” for semi-automatic service rifles. And this is for service rifles from 5.56/223 Rem, 7.62/308Win, 30-06, and even 8×57. The lighter your bullet, the closer to the top of this portion of the chart is probably going to server you better in terms of velocity and accuracy, and as your bullet weight increases going down towards the H4895, IMR4064, and Varget (not pictured, but it’s two steps below Reloader 15 but on the top of the next column on the chart).
You want to load 40 to 55gr bullets in 223 or 110 to 125gr bullets in 308? Stick to the 4198s and H322. If you use slower powders, you end up with the symptoms of pushed out primers, excessively sooty cases, and poor cycling. If you have a manually actuated rifle (bolt, lever, single shot of some sort) you can get away with using a slower powder and getting a little more velocity at lower pressure.
As far as getting “too much powder” into a 308 Win and blowing yourself up that Mr. Price is worried about, it is impossible to double charge a 308 Win with either IMR 4198 or H4198. It is possible to cram more into the case than you should, but H4198 has a volumetric density of 0.750, and my favorite 308 powder, IMR 4064 has a volumetric density of 0.745 (you can check yourself at the handy chart Lee provides: https://leeprecision.com/cgi-data/instruct/VMD.pdf), which should make it really dang clear that you are getting to a very full case by the time you would hit a 42.5 gr max charge with H4895 in a 308 under a 110gr bullet. In fact, his opinion that “about the 90% mark for proper function” isn’t wrong, and 4198 does that nicely.
And again, I don’t recommend anyone take reloading advice from someone who thinks the R1 with an ARGOs gas system is representative of all semi-auto rifles. Many a Garand op rod was bent by someone looking at a reloading manual and going, “Huh, I can get more velocity, with less pressure, using a heavier bullet with a better BC, if I just use this IMR 4831 or 4350 with a max charge, should be safe because both can be compressed!” That load would have been perfectly safe in a 1903 or 1917 bolt rifle, but not in a stock Garand. That’s why there is a nice market for adjustable gas plugs, to give Garand owners more options on what powders and bullet weights they can use to feed their rifles.
And lastly, when someone has symptoms of low pressure, don’t recommend and even slower powder like Mr. Price did. All that will do is exacerbate the problem.