Varget ?

[Bearcatrp]

Was shooting my reloads last week testing different powders (6). Was surprised that my AR10 handled the varget loads well to the point that even at max loads, no issues. But 2 other powders blew primers at max loads, IMR 4064 and IMR 8208 XBR. The max loads were Varget 44.0 gr, IMR4064 44.0 & 44.5, and IMR8208 42.0 . Have seen many posts folks praising varget so finally bought some to try. Its seems great so far. Something different about this powder than the others in regards to blown primers at about same charge?

[Seismic Sam]

Uhh, EVERY powder is different in one or more ways, so apart from the case where the same powder is sold by two companies (like H110 and 296) they are ALL different. How can depend on a lot more than burn rate, and that's a very complicated topic.

If for any reason you are working up a load and have even 1 blown primer, that is a big red sign to stop immediately, take your remaining loads home, pull the bullets and weigh EVERY powder charge, and compare those weights to as many manuals as you have. There may be something different about your gun that is affecting the pressure, or too much crimp, or if you are shooting rounds through the magazine, the recoil of the gun could be making the bullets move in (which will result in higher pressure) or move out, and if the bullet jams in the rifling the pressure will really go through the roof. I'm glad you and your gun are still in one piece!!

[Bearcatrp]

I did not crimp on these loads but you have me thinking on bullet set back. I put 5 rounds in the magazine. Only 1 of the 5 blew the primer but did notice flat primers on the rest. Could be the primer not tight as others when seating but doubt it as I insure they are the same with the rcbs hand priming tool. I worked up another batch of varget for when I go again but this time I expanded my range to see whats up. Think this time I will load 1 at a time to rule out bullet set back. I have another post in the general section about bad range trip that lists my specs. I like to experiment with multiple powders in the event I cannot find one I like and need to load another. So far I am liking varget though. Burn rate is hotter with 4064 (95) and 8208 XBR (86) vs varget (101).
https://www.hodgdon.com/PDF/Burn%20Rate ... 4-2015.pdf

[JJ]

Think this time I will load 1 at a time to rule out bullet set back. I have another post in the general section about bad range trip that lists my specs. I like to experiment with multiple powders in the event I cannot find one I like and need to load another. So far I am liking varget though. Burn rate is hotter with 4064 (95) and 8208 XBR (86) vs varget (101).
https://www.hodgdon.com/PDF/Burn%20Rate ... 4-2015.pdf

To check bullet setback, you need to be chambering and measuring each round with a caliper, both hand feed and magazine feed. You can have a bullet set back, as well as set forward (esp on auto guns).

As for your powder burn rate comment, Varget is a slower burning powder than the other two you have listed. Burn rate is not burn temp, it is the speed in which the powder combusts. its a faster/slower scale, not hot/cold scale.

[Seismic Sam]

As I said above, burn rate is just one of about 5 or 6 variables that are used by a program like Quickload to determine actual pressure factors, and the others have to be determined by pressure testing in a laboratory in Germany. As such, going by burn rate alone can lead you pretty far astray, and may or may not get you into deep trouble. Blown primers are caused by excessive high pressures, and NOT by one primer being a little smaller than the rest. The initial start of the powder burn generates enough pressure to make the primer cup expand to fill the case head, so blaming primer size is a red herring. It don't work that way.

[Bearcatrp]

Always measure OAL at 2.800 and each round is verified with a caliper. Plan on sliding bolt forward with charging handle to insure no slamming.

[Erud]

Always measure OAL at 2.800 and each round is verified with a caliper. Plan on sliding bolt forward with charging handle to insure no slamming.

OAL is not a reliable way to measure loaded rounds. If you're adjusting your dies so that each loaded round measures the same OAL, you can be causing major variations in pressure. Measure 10 bullets from the same box and you will see why. Distance from ogive to lands is the important number if you want consistent pressure. OAL is really only good for making sure rounds will fit in a magazine.

Bullet setback is not a likely culprit, unless you are running absolute minimum neck tension. I haven't crimped any AR rounds in at least 10 years and have never experienced an issue with .002-.003" tension. Riding the charge handle forward is a great way to make AR's not work right. Didn't you take a class from OldManFCSA or something a while back?

[Bearcatrp]

Didn't you take a class from OldManFCSA or something a while back?

That was for 50 BMG. Been using AR's long enough to know how they work and operate. Never had an issue loading a round this way, ever!

[crbutler]

A few things to mention

First off, each gun is a rule into itself with regards to pressure. If the rifle doesn't handle it, who cares what the book says...

However, I think part of what maybe happening with this is that an AR works with a gas system tube, and if you are using a powder that is very different in speed (burn rate) you can have the action start to open before Pmax is over.

If that happens, the primers back out under pressure, showing signs of flattened primers and blown out primers even if it is a safe load.

If you have an adjustable gas block, you can deal with this, if not, you need to use a powder in the proper range for the rifle.

The varget is a bit slower than the others, and is likely what the gun is set up for. This was the sort of issue some folks were having with commercial hunting ammo with garands (actually the other way around) and were damaging guns.

I have not had any issues with neck tension with AR rifles but I have had issues where an adjustable gas block caused problems like you are describing.

[Erud]

Didn't you take a class from OldManFCSA or something a while back?

That was for 50 BMG. Been using AR's long enough to know how they work and operate. Never had an issue loading a round this way, ever!

I guess the question about taking a class was more about reloading practices than AR function. If you've been soft-loading your AR's with no malfunctions, then more power to you. The things that are important for loading .50 are the same with smaller calibers. Using your provided data and generic case capacity numbers, the load of 44.5 grains of IMR4064 generates 62,727 psi, and has 108% case fill. It's what QuickLoad refers to as a ***DANGEROUS LOAD - DO NOT USE*** Blown primers would not be a surprise with those numbers.

All kinds of other factors play a role in pressure. Things like short chambers, tight barrels, excessively fouled barrels, excessive neck tension, etc can make loads that should be safe into loads that aren't safe. How much neck tension are you using on these rounds?

[Bearcatrp]

Looking at hodgdon load data web site for 168 gr barnes ttsx (close to hornady 168 a-max) for IMR 4064, max load shows 45.0 (compresses) vel 2743 and pressure at 58,900 psi . Not sure where you are getting 62,727. they don't list Hornady but the density and coefficient are real close. Have always read DPMS rifles are always over gassed but thats just reading different forums. I use a rcbs die (black box for AR's) to size my brass. Bullets go in a little snug when setting. Don't test neck tension with any tools. Don't crimp when I test loads either.

[Seismic Sam]

You're not listening or reading properly. He said his data was from QuickLoad, which I also swear by. You're cooking up some very hot stuff with multiple powders at once, and that in itself is a mistake. Just because the book says it's safe doesn't mean DIDDLY SQUAT with your rifle, scale, brand of brass, and chamber dimensions. If Quickload says the pressure is in the 60's, then that's what it is. Could somebody please post the upper right panel of the Quickload screen to show him all the stuff that goes into calculating this. Better yet, just post the whole screen that shows this load to be in the 60's.

[Erud]

Here you go:

[Erud]

And actually, I just noticed that QL shows the 168 AMAX to be a little shorter than Bryan Litz measured it in his book. If I change it from 1.265" to 1.282", the pressure gets even higher:

[Erud]

If you want to get the most from your hand loads, you need to understand neck tension and know how much of it you are subjecting your bullets to. "A little snug" could be anything, especially for someone new to reloading with no frame of reference. You also need to know the distance your bullets are from the lands. These are both MAJOR factors for pressure. You are blowing primers with loads you believe should be safe. You have a pressure problem, regardless of what the Hodgdon website tells you should be good for a different bullet.