Small Rifle Primer Vs Large Rifle Primer

[mitch_04]

Hi All,
You may have been reading about my AR reloading woes. After getting my 6.8 to chamber, it was shooting very lower and with not enough power to eject the round. I double checked my load data, and I'm finding that most loads were determined with large rifle primers, while my Hornady cases use small rifle.

Could this be the source of my lower power? And does anyone happen to know any loads meant for the small primer?

 

[rain164845]

I don't have a 6.8 or know much about them, but are you trying a standard small rifle primer, or magnum small rifle primers? I suppose it could make a difference.

 

[jscandale]

Hi All,
You may have been reading about my AR reloading woes. After getting my 6.8 to chamber, it was shooting very lower and with not enough power to eject the round. I double checked my load data, and I'm finding that most loads were determined with large rifle primers, while my Hornady cases use small rifle.

Could this be the source of my lower power? And does anyone happen to know any loads meant for the small primer?

Mitch,
For what it's worth, and this is just my opinion, I really don't think that a large primer is necessary for a powder charge less than 40 grains. I really don't know why Remington incorporated the LR primer into the case. A standard SR primer will set off any charge stuffed in a 6.8 case which is why every other manufacturer of the 6.8 case decided to go with the SR.

JS

 

[NHgunNut]

try a small rifle magnum perhaps?

 

[DHD]

Have you tried CCI 450's? My Grendel really shoots well with them. I also does well with Wolf SRM's. I have not even fired a 6.8, and don't know the load data you are using, but if it will function with factory SR loads and not your handloaded ammo using SR primers, then you are not pushing them hard enough. Proceed gently my friend. Ain't loading for an AR fun and rewarding!

Too bad they are so much fun, otherwise I would drop them like a cheating good looking high maintenance woman and never look back!

 

[Ringostar]

What load are you using ? I load 27.5 gr of benchmark, and have never had a problem with either case. I use hornady and silver state for plinking on the 500 meter silhouette range. Remington for deer hunting.

 

[Laurie]

For what it's worth, and this is just my opinion, I really don't think that a large primer is necessary for a powder charge less than 40 grains. I really don't know why Remington incorporated the LR primer into the case. A standard SR primer will set off any charge stuffed in a 6.8 case which is why every other manufacturer of the 6.8 case decided to go with the SR. [JS]

Yes, the LR primer is not normally needed for smaller powder charges except maybe in extreme cold weather conditions in winter hunting. The reason military cartridges are often 'over-primered' (cf 5.45mm and 7.62X39mm Soviet designs) is the requirement to work in any combat conditions and that can include literally Arctic temperatures. Ballistic consistency is sacrificed for ultimate reliability.

One problem with the LR primer in 6.8mm Rem SPC is that its case has a small 0.358-inch dia. case-head falling between the .222 Rem family's 0.332" and the 7.62X39mm / PPC family at 0.378" which uses the large primer in military form, but small in its .220 Russian / PPC guise. Look at a large primer dimensioned 6.8 and there is not a lot of metal around the primer pocket. I suspect this is why the original chamber pressure spec for the cartridge had to be reduced after expanded case-heads allegedly caused extraction difficulty and rifle action jams in very hot conditions in Afghanistan. Hornady and Silver State Armory versions with the small primer size have a lot more meat and strength in the case and should give better results in civilian target shooting in normal temperatures.

Like other respondents, I'd recommend small rifle magnum primers in an AR type rifle or the Wolf / Tula AR model with the thick magnum brass cup but standard size primer pellet weight, not for good ignition rather cup strength to avoid extreme cratering and blanking.

 

[mitch_04]

I'm using IMR 3031, 28 grains. I'm going to check the accuracy of my scale, because it was supposed to be a compression charge. It did not seem to be full enough to be a compression. I'll reload some of my rounds from yesterday and update.

 

[jscandale]

The case head for the 6.8 is .421"

JS

 

[Laurie]

Correct, oops! - Hornady gives two diameters against the case-head in its drawing, 0.358 and 0.422" and I used the wrong one. I think, 0.358" is probably the extractor groove diameter. Nevertheless my point stands - compare the large and small primer versions of the case and you don't see much metal around the pocket in the large primer version, while the small primer version looks much healthier. Incidentally, 7.62X39 was all large primer apart from a Remington manufactured version packaged under its old UMC headstamp and brand name. When I had a 7.62X39mm Cz527 carbine, I always intended to try comparing the two types of brass / primer size with typical loads in suitable powders to see what difference they made to the MV and MV ES, but never gor round to it. I do have a 6.8 and intend to see with it in due course.

 

[mitch_04]

Aaaaannnnd now I feel absolutely retarded. Went and looked at my scale. Word to the un-wise(like me), tenths and grains are different. Yes, I had it set to 20.8 instead of 28. I imagine this will fix my ejection problems and my low shooting. I am glad that it's a simply fix, and that I accidentally went light instead of heavy. However, when I was seating my bullets I did notice that my seating die is leaving a ring around my bullets. The fun never ends!

 

[Laurie]

Yes, I had it set to 20.8 instead of 28.

Still .... better that way than the reverse, if you see what I mean!

 

[M-61]

Laurie's last post is very correct.....The other way around and you may never see again!
I find myself, even after 40+ years reloading, re-checking and re-checking. Only the one powder can on the bench....reloading notes (book- open) and in the end when I fill out my sticker for the ammo case I make sure I've done it right. I really try to find a time to reload when I will NOT be distracted. Have I made errors? You bet, but I've caught most of them right on the reloading bench. Most have been caused by being distracted.

 

[NHgunNut]

The Most annoying mistake I ever made, Forgetting to put any powder in a 9mm case. Went to a friend's house, shot about 10 of 100 planned rounds and PFT. primer managed to get the bullet half way down the barrel. No cleaning rod with me. game over. haha. then to make sure it didnt happen again I blasted the next 90 rounds at my own range. using a bullet puller 90 times was out of the question. and i was using a compressed powder load(unique) with random cases, so I couldnt even weight sort or "shake and listen". GAR!