300prc with magnum powder too hot

[wywindsor]

The gun a browning xbolt. 26'' barrel stock to the bone. load 80grs of ramshot magnum 212eldx same CBTO as the hornady factory loads. Problem is the fps at 2750 and flat primers. Seems awful low compared to all the info I have gathered. Especially the flat primers, which were cci LRMP. No ejector marks, just flat primers. However the factory Hornady eldx212 shot 10 under to 50 over the advertised speed and had flat primers. Ideas as I'm no where close to the factory speed of the Hornady and ramshot i should be about the same?

 

[RustyInBend]

The sweet spot for my 300-PRC is 77.4gn of Retumbo ... gives me almost 2900 ft/sec and single-digit SD's shooting Berger 220's. Your 2750 does seem a little slow.

 

[wywindsor]

This was over 2 chronographs. One magetospeed and one labradar.

 

[Mike TackleBerry]

Quickloads is showing your loads at 2809 FPS, With a COAL of 3.700 out of a 26" barrel! With a COAL of 3.800 the velocity dropped to 2776 FPS!

 

[Old Navy]

Flat primers in not a good indicator of pressure.

 

[boltfluter]

Pushing the shoulder back to far on your reloads will give you nice flat primers with moderate loads. Just a thought.
Paul

 

[Nealm66]

N570 gives me the best velocities with 230/245 gr bullets. Lrt is second best. I’m using imr 8133 for 212 eldx’s at 2850fps

 

[Darkside]

Retumbo and N-570.

 

[wywindsor]

What is the best way to determine over pressure?

 

[Darkside]

#1 flattened primers, then faint ejector marks, then shiny ejector marks, then and I seldom if ever go as far as having heavy bolt lift. I don't mind being around flattened primers to find a node. And I seldom worried about fps. IMO

 

[Mike TackleBerry]

Heavy bolt lift, Ejector swipes on the brass! Do not use flattened primers as a solitary sign of overpressure! With CCI 400s i was getting flattened primers on my 6BR with a 105 at 2780 fps (Moderate load, Nothing heavy), When i switched to CCI450 the flattened primers went away!

 

[FeMan]

Over-pressure loads typically have flattened primers, but as stated above flattened primers do not necessarily mean over-pressure. Heavy bolt lift and/or any ejector marks on the case head are tell-tale signs.

 

[wywindsor]

I'm going to try n570, h1000 next with a load from the Hodgens and vih, data pages to see if the magnum powder is hot. The Hornaday factory loads were close to advertised speed give or take some. I have reloader 26 as well. I'm looking for speed and accuracy. I live in Wy. where the wind blows like hell everyday. Even a 300 yard shot on some days will challenge the best. A one moa gun out to 500 is fine. Not so good on an animal past that IMO. And I'm good on steel out to what I can hit.

 

[TrapperBR549]

I helped my son work up loads for his 300prc. We didn't have some of the powders mentioned but H1000 performed well with several different bullets. With was for hunting and the Nosler ABLR's shot great.

 

[FrankG]

Different barrel length as mine is 32" but 230gr bullets and 76gr of H1000 and CCI200 primers... I'm right at 2900fps.

The other thing to the OP... you don't know if the barrel is made to spec. If it's undersize on the bore and groove size that will drive up pressures as well. Wouldn't be the first time I seen a factory barrel not to spec let along undersize.