reloading subsonic .308
- Thread starter savage M110 BAS
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A few thou overbore isn't going to make any difference. Under normal circumstances the bullet is swaged into the lands anyway. Adding a couple of thousands of an inch to that equation won't make any difference.
It might not make tremendous difference but there will be some.There has to be. Another potential issue with using over bore jacketed bullets is neck thickness. If you have a tight chamber, some people may be unable to chamber rounds without forcing them. I can't imagine this to be a desirable situation.
I can't shoot .311" bullets in my .300 Blackout with converted IVI and Winchester brass. Haven't tried other brass but if things are getting that tight, I don't want to knowingly create a situation where reliability could be a concern.
To each there own. If the over size bullets work fine without issue there's no point in not using them. I was simply trying to point out there were more reliable methods of boosting ignition.
Higher pressure tends to bring more unifrom results and better accuracy. But higher pressure brings higher velocity. I was loading for supressed rifles, so had a velocity limit.
So I went with a fast powder and an over-sized bullet that would give a good pressure spike to promote good ignition, but the faster powder would drop pressures quickly and not be too fast.
The canned rifle had a 20" barrel. With 178 gr Hornady flat based, round nose bullets (.311") I got subsonic velocity (about 1050fps) with 10.5 to 11.5 gr of 2400. I load 308 with only factory primed virgin cases. These results are with Berdan-primed cases, since Berdan cases have tiny flash holes which help produce more uniform ignition, especially with small powder charges.
With the 190 gr Sierra RN bullet, 10.5 gr of 2400 got 1050 fps.
With the 220 gr Sierra RN bullet, 12.5 gr of 2400 got 1050 fps.
Been thinking about trying reduced loads in the 30 cals for quite a while now and finally got around to doing some research and making up a load using what I have on hand. Didn't use the 308(don't have one)but I'm trying some loads for the 7.62x54. From what I found on line I came up with a load using a .310 150gn cast bullet seated to the max for chambering(2.76) over 8gn of Clays. I also opened up the flash hole a little and seated a magnum pistol primer. Can't wait to try these out and once I perfect the load move on to my other cartridges.
Most info I found suggested the flash hole be enlarged as well to use the magnum primers. I opened her up by a 1/32 or so,so not that huge a difference but hopefully it will help with ignition. Thanks for the insight Ganderite. Does seem like Berdan would be the logical answer,but maybe not so practical for me. Where to find Berdan brass and primers? Brass and primers more expensive? I'll have to wait and see the results and go from there.
I work in a factory that has primed brass by the barrel. We just use whatever works best for a given application. Re-loading Berdan is not an issue.
Personally, I load for many calibers, and only one of them requires Berdan. I have the primers and it is not all that difficult, but I only load 20 or 40 at a time.
The only place a larger flash hole helps is when using wax bullets in a revolver.
Since you have modified some brass, try shooting them over a chrony and the same load with un-modified brass. See which has the lowest ES and SD.
Personally, I load for many calibers, and only one of them requires Berdan. I have the primers and it is not all that difficult, but I only load 20 or 40 at a time.
The only place a larger flash hole helps is when using wax bullets in a revolver.
Since you have modified some brass, try shooting them over a chrony and the same load with un-modified brass. See which has the lowest ES and SD.
What you're saying here is contrary to conventional wisdom on this topic. I've heard plenty of arguments for drilling out flash holes but absolutely "NONE" for making them smaller.
I would think the ES & SD spreads you speak of can potentially be explained that enlarging flash holes isn't exactly easy, it's imprecise, and consistency can/will suffer as a result. These induced variances will no doubt affect velocities in a negative manner.
Short of manufacturing a particular cartridge case with both small and large flash holes and then conduct testing, I don't see how it's possible to make the claim you are. I certainly respect your knowledge in reloading as you are very knowledgable and experienced.
The rifle cartridges that I'm aware of that have manufactured cases in both flash hole sizes are .398 Win. and 7.62x39mm. The .308 Win cases are likely easier to source as Lapua makes them.
Might be a worth while endeavour to test your assertion.
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I know. That is why I share this information. SD is inversely proportional to the size of the flash hole. The only sign I have seen of that being applied is the new Lapua 308 Palma brass. It has a flash hole so small that a standard decapping pin does not fit it.
What you're saying here is contrary to conventional wisdom on this topic. I've heard plenty of arguments for drilling out flash holes but absolutely "NONE" for making them smaller.
I would think the ES & SD spreads you speak of can potentially be explained that enlarging flash holes isn't exactly easy, it's imprecise, and consistency can/will suffer as a result. These induced variances will no doubt affect velocities in a negative manner.
Short of manufacturing a particular cartridge case with both small and large flash holes and then conduct testing, I don't see how it's possible to make the claim you are. I certainly respect your knowledge in reloading as you are very knowledgable and experienced.
The rifle cartridges that I'm aware of that have manufactured cases in both flash hole sizes are .398 Win. and 7.62x39mm. The .308 Win cases are likely easier to source as Lapua makes them.
Might be a worth while endeavour to test your assertion.
This has been done by a major manufacturer working on a military contract that had an enhanced accuracy requirement. I assume it has been done by others, as well. the results were conclusive. SD v. hole size graph was almost a straight line of inverse relationship.
I can't publish the report, it is confidential. I suggest that anyone contemplating enlarging flash holes run an experiment before drilling out very many.
This is true when we are talking about a case full of powder in a conventional loading. Not so for subsonic loads which may only have a 1/3 load density. With small amounts of pistol powder we want as much flash as possible to hit the powder all at the same time. Otherwise partial ignition can become an issue. and trust me I'd much rather suffer through a wide velocity spread than have the rifle explode in my face ... every time.
This is not really anything new or shocking. The PPC cases have had small flash holes for decades for exactly this reason. But none of what you are saying takes into account a small amount of powder in a large case. Getting all the powder to burn is the primary goal. Accuracy is secondary in this case.
I would caution anyone playing with subsonic loads in large rifle cases to be EXTREMELY cautious about the potential for SEE or incomplete ignition. It can and has blown rifles up. If you do not want to drill out flash holes then make sure you are using a powder that fills the case at least 65-75%.
Cast bullets are naturally lubed. Jacketed bullets are not.
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No chronograph yet,but one of these days. Can still load up some brass with unaltered flash holes like you suggest Ganderite and compare with the altered brass. Guess I'll do it the no tech way for now though
You're flying totally blind and taking un-necessary risk by doing so. For .308 Win. loads there are plenty of combinations that don't require the modification of flash holes providing that the load densities are within reason. Without a chronograph you have no basis on which to collect data or know which method performs best for you. The only measurement will be what you're shooting on paper and with subsonics that simply isn't going to be good enough.
This is true when we are talking about a case full of powder in a conventional loading. Not so for subsonic loads which may only have a 1/3 load density. With small amounts of pistol powder we want as much flash as possible to hit the powder all at the same time. Otherwise partial ignition can become an issue. and trust me I'd much rather suffer through a wide velocity spread than have the rifle explode in my face ... every time.
You are using logic.
I am referring to lab results.
The primer energy is constant. A small flash hole seems to give better ignition with small powder charges. I have never bothered to figure out why. I have assumed that the result is a much longer squirt of flame into the case - but that is just a guess. Don't much care why, once I know what works best.
But your mileage may be different. Easy to try both and make your own choice.
You are using logic.
I am referring to lab results.
The primer energy is constant. A small flash hole seems to give better ignition with small powder charges. I have never bothered to figure out why. I have assumed that the result is a much longer squirt of flame into the case - but that is just a guess. Don't much care why, once I know what works best.
But your mileage may be different. Easy to try both and make your own choice.
Though not a load density issue, I can relate to wanting complete ignition 100% of the time.
Last year on one particularly cold day I had a slow ignition on a 11.5gr. Trail Boss load in .308 Win. that I was shooting. I can't scientifically say it WAS the cold temperatures, however, I'd fired many hundreds of this load before in warmer temps without an issue. It scared the sheet out of me. Rifle was fine but I junked the case as a result of it. From that point on, the only cartridge I'll shoot subs in the cold with is .300 Blackout. I'm sure magnum primers might have prevented the situation from happening but it's hard to know for sure and I'm not interested in taking un-necessary risk.
I hear you bud. Gonna get one ASAP but for now I think I'll be alright.
