Please HELP!! Low pressure???

Colin78

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Hey guys, I have an issue I have never seen before and from what I have read I think it may be low pressure. I took my new 6.5 saum gap 4s with a 22” barrel to the range today to fire form some brass and play with some starting loads. Since this is a wildcat and no published dada I used what little info I could find. I loaded 3 each of H1000 and 129 ablr with F215 primers in brand new ADG brass starting with 60.5 grains up to 62 grains. I also tried H4831sc from 53 grains to 55.7 grains. In the majority of the cases I am getting a little dent in the shoulder. Some of them also have black powder residue down the case body. After doing some research this sounds like too low pressure. I will also add the velocity was quite a bit lower than I was expecting. The H1000 loads in the 2800's and the H4831sc loads from 2560 to 2760. Gees that’s creedmore velocity, way way lower than other folks are reporting with those charges in a 22” barrel 6.5 gap. Now I will say we throated this LONG. So my bullets are seated way out there not taking up much case volume at all. Would having a couple / few more gains of case capacity results in low pressure? And based on my initial loads where do you recommend I go from here? Not gonna lie I’m a little nervous. I want to increase my powder charges but I don’t know how much. If I increase the charge but it’s still too light am I createing a bigger hazard for myself? Or since I’m already in low pressure zone and didn’t blow myself up will any increase in charge/ pressure be safer than I have already had? My hottest H1000 load was 62 grains at 2900 FPS and still had dented shoulders, so do I go ahead and jump up to 63 grains or should I go to 62.5? Same with H8431 my hottest load was 55.7 grains at 2746 FPS. How big of a jump should I go to next for it? I really appreciate all the help I get on here for you folks that have tons more experience than me.
 

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MagnumManiac

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If you are not getting hangfires, it is quite safe to keep adding powder, even a grain at a time, until you get slightly stiff bolt lift. Then back off 2 grains.
I built 2 rifles within a year of the 300WSM coming out in 25-300WSM (Pronghorn as it is known) and the 2 rifles exhibited exactly what you are experiencing, my buddy and I loaded the exact same components/powder/primer and we had dented case shoulders, soot all the way to the case head and backed out primers. Wasn’t until we approached 257 Weatherby data that it went away. Also experienced it with a 7RUM I built, had me as nervous as a chook in a fox den.
I am building a 6.5SAUM as we speak, so watching with interest to the outcome.

Cheers.
 

243winxb

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https://thefiringline.com/forums/showthread.php?t=476535

Need- mag primer, more neck tension, faster burn rate powder, bullet shank in full contact with case neck.

A secondary pressure spike is possible, with your current loading. Bullet moves to soon. Acts like a plugged barrel.

Now I will say we throated this LONG. So my bullets are seated way out there
Not helping the problem. A guess?

Get someone to run Quickload data for you. May just need more powder??
 

orch

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Are you set on using the 129gr Ablr’s? I assume when you said you weren’t finding much info it was for the 129’s... there’s lots of info out there on the 6.5rsaum but it’ll mostly be for 140+ class of bullets.. anyways ya if it’s throated long so your bullets got a long jump and you are at speeds like that with a 129 I’d suspect it’s not expanding that case enough to seal off the chamber before your bullet leaves the case mouth...

Exactly how long is it throated for?

Possible solutions:
keep working up your charge weight until you get those cases expanding... you’re in low pressure now so 1/2 gr increments should be ok... I’ve had 143’s up over 3200fps in two of my 6.5rsaums before any signs of pressure so if you aren’t hitting 3000fps with a 129 you have plenty of room to push it...one caveat may be you are getting slow speed because gas is leaking all the way past your case but I’m pretty sure you’d notice that...

Check your neck tension, are you using a bushing die?...not likely an issue but if your cases are barely gripping the bullet and you have a long jump you could be getting gasses back around the case from poor case expansion

Switch to a faster burning powder for the 129’s and get a quicker pressure spike to get that case expanding

Switch to a heavier bullet, more mass means more energy required to move it... also bigger bullet means longer and it will be closer to the lands and should increase your pressure...

Orch
 

Colin78

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I’m going to start going up in half grain increments only loading 1 case for each charge for both H1000 and H4831 and head back to range in the morning. Y’all say a prayer for me. Not gonna lie I’m probably going to be pretty dang nervous with each squeeze of the trigger till I get out of this pressure issue.
 

Colin78

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I failed to mention I also had some 140 Berger Elite Hunters with H1000 that did the same thing. I only shot a couple of them.

Yes neck tension is only around .001 I have another bushing on order to get that up around .0025

I don’t want to keep ruining this ADG brass. I also have some Hornady brass I’m going to load for tomorrow. Once I get a ball park of where I need to be I will go back to the ADG brass.

I really really appreciate all of your reply’s. Anyone want to come pull the trigger in the morning? Lol
 

Colin78

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Are you set on using the 129gr Ablr’s? I assume when you said you weren’t finding much info it was for the 129’s... there’s lots of info out there on the 6.5rsaum but it’ll mostly be for 140+ class of bullets.. anyways ya if it’s throated long so your bullets got a long jump and you are at speeds like that with a 129 I’d suspect it’s not expanding that case enough to seal off the chamber before your bullet leaves the case mouth...

Exactly how long is it throated for?

Possible solutions:
keep working up your charge weight until you get those cases expanding... you’re in low pressure now so 1/2 gr increments should be ok... I’ve had 143’s up over 3200fps in two of my 6.5rsaums before any signs of pressure so if you aren’t hitting 3000fps with a 129 you have plenty of room to push it...one caveat may be you are getting slow speed because gas is leaking all the way past your case but I’m pretty sure you’d notice that...

Check your neck tension, are you using a bushing die?...not likely an issue but if your cases are barely gripping the bullet and you have a long jump you could be getting gasses back around the case from poor case expansion

Switch to a faster burning powder for the 129’s and get a quicker pressure spike to get that case expanding

Switch to a heavier bullet, more mass means more energy required to move it... also bigger bullet means longer and it will be closer to the lands and should increase your pressure...

Orch
I don’t remember exactly what it’s throated for, gotta call my smith Monday and discuss all this with him. I know he was very curious as to what I could do with it. I will say this the 129 ablr's are .02 off the lands and all of the boat tail is in past the case neck but that is all. So I am getting full grip on the bullet.

What powder would you recommend? Is H4350 faster than H4831? Would that be the next to go? I only use hodgdon extreme powders.
 

Bill Cauley Jr

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I don’t remember exactly what it’s throated for, gotta call my smith Monday and discuss all this with him. I know he was very curious as to what I could do with it. I will say this the 129 ablr's are .02 off the lands and all of the boat tail is in past the case neck but that is all. So I am getting full grip on the bullet.

What powder would you recommend? Is H4350 faster than H4831? Would that be the next to go? I only use hodgdon extreme powders.
6659E983-BDCC-4B9E-9577-7D95FCB7012B.png
 

Buster Hemlock

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Absolutely agree that you are experiencing low pressure based on your loads you shared and the soot and dents on your brass. For wildcats it's common to look to other cartridges with a similar design and capacity and adjust up or down a little. In your case the 6.5 SAUM has around 3 grains more capacity than the 6.5 PRC. Using a middle to upper level charge for the 6.5 PRC would be a safe starting place. The long throat and light neck tension isn't helping either. If you want quickload data let me know and I can run it for you.
 

Colin78

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Absolutely agree that you are experiencing low pressure based on your loads you shared and the soot and dents on your brass. For wildcats it's common to look to other cartridges with a similar design and capacity and adjust up or down a little. In your case the 6.5 SAUM has around 3 grains more capacity than the 6.5 PRC. Using a middle to upper level charge for the 6.5 PRC would be a safe starting place. The long throat and light neck tension isn't helping either. If you want quickload data let me know and I can run it for you.
I would love to have you run quick load. Thanks. What all info do you need?

I am at the range now and got out of the low pressure issue and my velocity is up where I was expecting. I will post up my results when I get home. Would be cool to see how quick loads compares to my field testing.
 
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