Pressure Signs or rather the lack of pressure signs

Topic: Pressure Signs or rather the lack of pressure signs (Read 290 times) previous topic - next topic

Pressure Signs or rather the lack of pressure signs

April 08, 2021, 12:11:59 AM

I have a friend I shoot with regularly. We both shoot 6.5 CM. Due to the recent bullet shortage he found some 145 gr Barnes match burners and decided to give them a try. Long story short is the velocity he is getting. The flat spot 2805 fps with 41.4 grs of IMR4451 .020 off the lands. The load ladder started at 41(2769 fps) and ended at 41.7 grs(2820 fps). New Starline LP brass, CCI 200 primers. Velocities were recorded with a magneto speed chono. I see a little flattening of the primers no cratering. Nothing excessive. No heavy bolt lift or swipe. I even had him measure the case heads on the fired brass from the load ladder and new unfired brass. They both measured the same. These were fired in a Benchmark barrel 1 in 8 twist 26"

What if anything am I missing? I cannot explain the velocity he is getting.

I fired a similar load ladder with 145 gr. Barnes MB in my RPR. 41 gr(2673 fps) gr to 41.9 gr(2749 fps) with H4350 .060 off the lands. CCI BR2 primers. With no pressure signs. Barnes maximum is 42.1 gr of H4350. Minor flattening of primers. Criterion 1 in 8 twist 26".

Tim

Re: Pressure Signs or rather the lack of pressure signs

Reply #1 – April 08, 2021, 05:07:04 AM

Tim i dont think your missing any thing.. your comparing two different barrels with two different loads even though their using the same bullet and powder.. you cant really expect the same results..

Re: Pressure Signs or rather the lack of pressure signs

Reply #2 – April 08, 2021, 08:10:07 AM

Actually you are comparing two different powders as well.

Most 26” barrels will push the 140-143 gr Bullets to the lower 2800s without pressure - if the correct powder is used. The 145 is a little heavier but seems to agree with his barrel well.

It would be interesting to see you run his ladder through your RPR and then compare velocities. The won’t be the same but it would be interesting to see how close they are.

I hope you try that. I would like to hear the results.

Re: Pressure Signs or rather the lack of pressure signs

Reply #3 – April 08, 2021, 11:05:46 AM

Tim; as Grant said, you can't even compare loads with the same
barrel maker. Each will act slightly different and you two are using
two different powders and different barrel makers. We've seen barrels
as much as 100fps difference.
Always treat your barrel as an individual and has it's likes and dislikes.

We have top rated shooters that have 2 barrels done at the
same time and they act differently.

Re: Pressure Signs or rather the lack of pressure signs

Reply #4 – April 08, 2021, 06:49:59 PM

Sorry for the confusion. I was not comparing our loads. I was worried that I might have missed something. I wasn't sure about pushing the 145 gr bullet that fast. Saftey first.

I would have expected to see more pressure signs.

The ladder that I ran shows a flat spot starting at 41.7 grs(2753 fps). I will re-run it up a little higher to find the jump. If I find no pressure signs 41.5 to 42.3 grs.
41.7 grs 2753 fps
41.8 grs 2752 fps
41.9 grs 2749 fps

These are my loads in my gun do not use with out proper load work up.

Thank you for your replies

Tim

Re: Pressure Signs or rather the lack of pressure signs

Reply #5 – April 08, 2021, 07:04:11 PM

Quote from: jvw2008 on April 08, 2021, 08:10:07 AM

Actually you are comparing two different powders as well.

Most 26” barrels will push the 140-143 gr Bullets to the lower 2800s without pressure - if the correct powder is used. The 145 is a little heavier but seems to agree with his barrel well.

It would be interesting to see you run his ladder through your RPR and then compare velocities. The won’t be the same but it would be interesting to see how close they are.

I hope you try that. I would like to hear the results.

Re: Pressure Signs or rather the lack of pressure signs

Reply #6 – April 08, 2021, 07:43:27 PM

We did talk about trying his load ladder in my gun.
It could be interesting. If we load it up I will post the results.

Tim

Re: Pressure Signs or rather the lack of pressure signs

Reply #7 – April 08, 2021, 07:53:08 PM

the speed with the 145 match burners are probably in line with say a 140 gr. eldm or other 140 class bullets... no experience with the match burners but i suspect the bearing surface length is close to most other 140 gr. bullets... so there shouldnt really be any problem getting them in the low 2800's unlike the 150 class bullets that has a longer bearing surface...makes them harder to get in the 2800's with the 6.5 creedmoor.... length of the bearing surface has more to do with pressure than weight of the bullet in my opinion...

also your flat spot needs to be wider than a .2 grain spread tim... it needs to be at least a .6 gr. spread...

Re: Pressure Signs or rather the lack of pressure signs

Reply #8 – April 08, 2021, 07:55:41 PM

I use H4350 in my RPR with a 26” Hawk Hill. No problem getting to 2830 with 140s. Pretty sure you could get the 145s there without excessive pressure.

Re: Pressure Signs or rather the lack of pressure signs

Reply #9 – April 08, 2021, 07:57:29 PM

. it needs to be at least a .06 gr. spread...

Typo Grant?

Re: Pressure Signs or rather the lack of pressure signs

Reply #10 – April 08, 2021, 08:24:02 PM

Quote from: jvw2008 on April 08, 2021, 07:57:29 PM

. it needs to be at least a .06 gr. spread...

Typo Grant?

yes jerry... i fixed it...lol

Re: Pressure Signs or rather the lack of pressure signs

Reply #11 – April 08, 2021, 09:39:45 PM

I don’t put a lot of faith in flat spots generated by 3 rounds per charge weight. But if I did I would be happy with a spot that spanned a 0.3 gr range of powder charge. “Happy” is a relative term. If that flat spot did not coincide with target support of a node, it would further my belief that flat spots can be misleading.
We’ve had this discussion before I guess. Just not a fan of the Satterlee approach to load development.

Re: Pressure Signs or rather the lack of pressure signs

Reply #12 – April 08, 2021, 10:23:14 PM

A typical velocity ladder with a 6.5 creedmoor.. with a pretty fresh barrel.. it couldnt show the low 2800 node any clearer.. 42.5 is what i run the 140 amaxes at .. and get 1/4 moa or less at 430 yards.. it may not be bench rest worthy but it works for me.. we have had this discussion and i know you dont put much stock in a velocity ladder but i have had pretty good luck with them.. the cool part is we all go about it a little differently.. main thing is will it get ya where you want to go.. each of us has to figure that out on our own..

Edit.. this load works in my gun.. as you can see in the pic i started low and worked my way up.. never start with someone else load..

Re: Pressure Signs or rather the lack of pressure signs

Reply #13 – April 09, 2021, 07:39:44 AM

Quote from: tg2403 on April 08, 2021, 06:49:59 PM

Sorry for the confusion. I was not comparing our loads. I was worried that I might have missed something. I wasn't sure about pushing the 145 gr bullet that fast. Saftey first. I would have expected to see more pressure signs.

The ladder that I ran shows a flat spot starting at 41.7 grs(2753 fps). I will re-run it up a little higher to find the jump. If I find no pressure signs 41.5 to 42.3 grs.
41.7 grs 2753 fps
41.8 grs 2752 fps
41.9 grs 2749 fps

These are my loads in my gun do not use with out proper load work up.

Thank you for your replies

Tim

love it when you find flat spots like this

Re: Pressure Signs or rather the lack of pressure signs

Reply #14 – April 10, 2021, 11:07:50 AM

I would like to post a PDF file how can I do this? It is a line chart of 145 Barnes MB

Grant,
I am running a ladder higher to try and find the .06 wide spread on the powder. I think I caught half of it at the end of my first ladder. I value your input and all of members of this Forum.

I have been reloading since the mid 70's. In the past 5+ years though I have been chasing that damn RABBIT. I went deeper than some and not as deep as others following that nasty little critter. I know I am not done either.

In the past 2 years with the unknown help of this forum mostly. I have read the info others have posted and compare it to mine. I have gotten down to single digit SD's and ES's. I look for the flat spots and find the jump in and out on the flat spot.

I now look back at what I have learned. I can only say Thank You for sharing what you and the other members have learned and posted.

Tim