What is the difference between the Rem. small rifle 7 1/2 & 6 1/2 primers? I think they are both BR primers, but don't think that is important here. I have both and usually use the 7 1/2 loading my 300 whisper using either H110 or RL7. My guess is the 6 1/2 is a bit slower/weaker/gentler. Can you tell me or direct me to info on these primers? Make recommendation on which one to use, use either. Try both and see what I prefer? Thanks

I think you got it correct.

6 1/2 milder and meant for cartridges like .22 Hornet.

I think I will just load the 6.5 and see how they compare (speed) and how they performs. I have had some of the 7.5 primers not ignite; as if they were too hard. I may like the 6.5 better. I'll let you know. I have heard that the 7.5 are harder and thicker to take more pressure and need a strong firing pin spring. The subsonic 300 whisper loads may work well with the 6.5 Rem primers as they are softer and thinner. I need a primer to ignite every time, last time I had 25% not go off.

Rem 7 1/2 are my preferred primers for my 223, and I've had good results with them. They (Remington) are VERY specific about not using 6 1/2 primers in higher pressure cartridges or larger powder charges. It might be hard to get that information from them now; but it says the weaker power of the 6 1/2 may/can cause hangfires and or poor ignition, which can lead to odd pressure, etc. I remember reading this line very specifically when I was selecting primers for the 223.

quote:

Originally posted by Clayman:
Rem 7 1/2 are my preferred primers for my 223, and I've had good results with them. They (Remington) are VERY specific about not using 6 1/2 primers in higher pressure cartridges or larger powder charges. It might be hard to get that information from them now; but it says the weaker power of the 6 1/2 may/can cause hangfires and or poor ignition, which can lead to odd pressure, etc. I remember reading this line very specifically when I was selecting primers for the 223.

I recall this^^^ as well.

Another life ago, I worked in a sporting goods store and that's what the recommendations were.
Admittedly, I've never used 6 1/2 primers but have used a pretty decent pile pf 7 1/2's.

Zeke

What Clayman said. Cup thickness is greater on 7.5s. Matters with .223/5.56.

But I bought couple sleeves of 6.5s on closeout specifically for use in 9mm open bolt subguns.
Tried them in .38 Spl. Turns out they work fine in all our Smith revolvers. None have had trigger jobs, so....

"Inherited" some .223 brass primed with 6.5s, so loaded 55 gr fmjs ahead of a starting load (IMR 4320). About 10% of ejected cases evidence a slight perforation. Running them out with a high-mileage bolt.

Ken Waters used them in .222 and, IIRC, .223 bolt guns. That was decades ago.

I like 6 1/2 in .22 Hornet...nothing else.

The same loads in my 17 rem with the recommended 7.5 primers, pierced the primer of 6.5's. So yes, the cup is harder on the 7.5

CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS
http://www.sksboards.com/smf/index.php?topic=56422.0

With Remington small rifle primers, the 6 ½ primer has a thin cup and is not recommended for higher pressure rounds like the common .223 Remington. It was intended for the .22 Hornet. When Remington introduced their .17 Remington round in 1971 they found that the 6 ½ primer was not suitable to the high-pressure .17. The 7 ½ BR primer was developed for this reason. According to Remington, the 7 ½ has a 25% greater cup thickness and they state on their web site: "In rifle cartridges, the 6-1/2 small rifle primer should not be used in the 17 Remington, 222 Remington or the 223 Remington. The 7-1/2 BR is the proper small rifle primer for these rounds."


Remington 6 ½ - thin .020" cup, intended for older, lower pressure rounds Remington says do not use for the .223 Rem or other similar pressure rounds. Good for .22 Hornet, .30 Carbine.

I'm finding out that your all correct on these primers. The 7 1/2 Rem primers are thicker and harder; that is why my rifle only has 75% success in firing these "Hard" primers. Will not use in my 300 whisper again as too many misfires. The 6 1/2 work great, never had a misfire with these. I see a very small difference in velocity between the two primers. Loading 13.0 gr. of RL7 under 210 gr VLD Berger bullets I got 1056 ft/sec with the 6.5 and 1077 with the 7.5. With 220 gr SMK, same loading, I got 1082 ft/sec with the 6.5 and 1097 with the 7.5 (avg. of 4 shots). I usually get 4 or 5 rounds out of 20 that misfire using the 7.5 rem primers. Weak firing pin spring?? Maybe. I better try the 7.5's in another rife to tell me if I is my rifle or the primers are too hard (defective).