over pressures 6.5 grendel

[dellet]

odd , the new brass max charge H335 i loaded did not kick the brass forward but out to 4 o clock not one of the powders i used sent them forward

To send the brass forward, it has to be sent rearward with great force. It has to bounce off the deflector. That is bolt speed determining where the brass will land. It need to be kicked out to 5 o’clock before it can bounce back to 2 o’clock.

Bolt speed is determined by pressure, but peak pressure has little to do with it. Other than typically the higher the peak, the faster pressure drops off and the lower it is 7-12” down barrel where ports are generally located.

300 Blackout drives this issue home. People want to shoot low pressure subs, and high pressure supers, the problem is enough gas for subs, without over gassing the supers. Basically an impossible scenario. Powder choices span Reloader 10 to N105. When you are on the edge of reliable cycling subsonic loads using fast powders, and are already at a higher velocity, 1050 fps +, moving the bullet out often solves the problem. Lower load density reduces initial pressure, which slows down and lowers peak pressure. This in turn flattens the burn rate curve and in turn raises pressure all the way to the muzzle. More importantly at the port for cycling.

I’m not saying that ann over pressure load is off the table. Only that you might want to treat it as two separate problems. It’s very easy to over gas a load that will not flatten a primer.

It’s also easy to have a load that is both over pressure and over gassed. But typically their are more signs than a flat primer.

There is a reason Hornady seems to be crimping more and more of the primers in their loaded ammo.
Is it due to high pressure rounds?
Or consistently turning out brass that measures below SAAMI minimum?

They have had problems with primers coming out, the crimp is a bandaid.

 

[misser]

To send the brass forward, it has to be sent rearward with great force. It has to bounce off the deflector. That is bolt speed determining where the brass will land. It need to be kicked out to 5 o’clock before it can bounce back to 2 o’clock.

Bolt speed is determined by pressure, but peak pressure has little to do with it. Other than typically the higher the peak, the faster pressure drops off and the lower it is 7-12” down barrel where ports are generally located.

300 Blackout drives this issue home. People want to shoot low pressure subs, and high pressure supers, the problem is enough gas for subs, without over gassing the supers. Basically an impossible scenario. Powder choices span Reloader 10 to N105. When you are on the edge of reliable cycling subsonic loads using fast powders, and are already at a higher velocity, 1050 fps +, moving the bullet out often solves the problem. Lower load density reduces initial pressure, which slows down and lowers peak pressure. This in turn flattens the burn rate curve and in turn raises pressure all the way to the muzzle. More importantly at the port for cycling.

I’m not saying that ann over pressure load is off the table. Only that you might want to treat it as two separate problems. It’s very easy to over gas a load that will not flatten a primer.

It’s also easy to have a load that is both over pressure and over gassed. But typically their are more signs than a flat primer.

There is a reason Hornady seems to be crimping more and more of the primers in their loaded ammo.
Is it due to high pressure rounds?
Or consistently turning out brass that measures below SAAMI minimum?

They have had problems with primers coming out, the crimp is a bandaid.

BCA side charger's dont appear to have deflectors

 

[Laurie]

have ever sized a brass,sliped it into the chamber and let the bcg slam shut , then rechecked the measurement of the brass ? shorter ?

My 6.5 Grendel rifle is as stated a Howa Mini (ie bolt-action), so this situation didn't apply. In any event, the cases were new from Lapua as they went into the chamber, and quite gently at that, and their case-head to shoulder distance was too short at that point creating excess headspace. They came out of the chamber longer not shorter after firing having been fireformed.

Before you suggest the rifle's headspace was incorrect, I'm in the UK and every firearm has by law to be proof-house tested before sale. This includes checking headspace, so there was no question of that being incorrect as the rifle was brand new and fresh from proof. These were the first rounds fired through it, bar the proof-house's single proofing round.

 

[Mark611]

NO, BCA side chargers do not have deflectors, every AR I have is a right-side charging upper, I'm a south paw shooter, I do not like AR rifles to begin with! and if it weren't for the side charging uppers I would probably never own an AR type rifle! I have had a few rear cockers in the past, I don't care for them at all! I'm not a fan boy of AR style rifles, even after owning an ARMALITE AR10 Match rife, for me the AK or M1A in a gas gun is my preferred choice, that said, all of my AR are RSC guns and I have spent a lot of time working with them to prefect them, with my own builds from the lowers to the upper, using quality parts and 2 stage match triggers, I know this is a bit off the topic, but If I'm putting this much effort to the 6.5GRR in an AR plat form that should tell something, That's how much I like the cartridge, along with the 223/5.56 in these guns, I hand load all my ammo, with 40yrs of reloading experience of doing so, when I hear a topic like this it only brings out my experiences from what I have learned, a lot of good advice has been givin here, from other guy's on this forum, Cheers!

 

[dellet]

BCA side charger's dont appear to have deflectors

The case can still bounce of the rear of the ejection port if it hasn’t completely cleared the bolt by then. Remember the definition of over gassed is the bolt traveling faster than designed. If the ejector can’t push the case off the bolt faster than the carrier can bottom out, you’ll have ejection problems. A bolt can also travel faster than a magazine can feed.

Your other question about crushing the case when chambering, happens all the time. Part of the reason to push the shoulder back .001-2” more than on a hand fed action. If it’s easier to crush the brass, than snap the rim over the extractor, the case will colllapse at the shoulder. Might be an indication of too heavy of spring if the set back is more than that.

I am not aware of any way that a case can be thrown forward, with our either bouncing of something, or staying on the bolt until the bolt has started back forward.

Would love to see high speed film of it if it’s out there.