Friend bought a .450 Bushmaster upper for his AR-15 and can't find any Large Rifle primers.
Ammo is roughly $2 a pop but you're left with a reloadable case afterwards.
He currently reloads for .45ACP and .45 Colt so he has bullets and powder that could possibly be used, along with Large Pistol primers and he thinks the two are interchangeable
I'm not so sure as I've heard rifle primers have a thicker cup to handle higher pressures.
Do any of you know for sure?
...oops wrong forum, oh well, do any of you know the answer?

Large Rifle primer pockets are deeper than Large Pistol. Using LP primers in rifles usually result in primer seated too deep. And yes, the cup is harder on rifle primers.

Dan

No they are NOT the same.

Some interchange of primers is okay, but what you mention is not. LP would only work safely for low pressure rifle loads, and that's not to mention the likelihood of LP primers being seated too deeply for reliable ignition.

Hey thanks for the reply you guys, he could use low pressure reloads with a light buffer maybe but I didn't know about the primer length difference.
I'll tell him to just wait for Large Rifle primers to become available and maybe that will happen in his lifetime.

...wow I thought that the previous .22 long rifle shortage was bad.
...hey this should work...💥

Diameters are the same, but LP primers are slightly shorter. Also they may fail under high pressures. Some do use LP primers for black powder or lightly charged rifle loads. Preferable to use LR primers for most rifle loads. I have used LP primers for loading .30-30, they worked OK for that. But that was long ago.

Hey friend just found some large rifle primers!
What an amazing coincidence!
Now he needs dies and some powder besides Bullseye and Unique.
Life is good!
Access Denied
Access Denied oh well he got some!

There are small enough differences that they could cause an issue. While some say they use them interchangeably, I would personally say not to. Better to err on the side of caution! The risk isn't worth the savings.

Just to give you guys an update, my friend now has all the correct components, either on hand or on the way to make up some .450 Bushmaster reloads and should have them ready to test by the time the weather permits him to show up sometime next week.
I will be observing his work from a distance.

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Here's something from one of my manuals.

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Thanks for the information yeah that is a rather significant difference.