I have an issue with 6.5 Creedmoor or maybe just reloading

[AntiPattern]

I reloaded some rounds that I wanted to test using 140 RDF and RL-17. I tried to be super careful and meticulous with these loads. I loaded up a group of 25. From 41.1 to 42.3 in .3 increments. I'm using Hornady brass and CCI #200 primers. The first group I shot I was hitting 2850fps. When I got the 41.4 group, I had 2 shots at 2900 fps and blew a primer. Stopped there. I should have been seeing around 2700 - 2725 with these 2 loads. I purchased a Lyman digital scale with trickler. I would assume this would be a decent unit. I have re-calibrated, zeroed, etc. This is the second time I've loaded a group only to have them way hotter than expected. I set the oal at 2.87 because I measured my rifling at 2.9 and these still fit in my AI mags. I'm shooting a Thompson Performance Center LRR in 6.5 with a 24" barrel.

Where do I start figuring this stuff out? My only guess is that my powder grains reading is off and the scale is reading lighter than it should.

 

[Kmccord]

I would suggest you have a balance beam scale to measure what is thrown electronically, that is what I do, some even throw a charge a grain or two less and then trickle it on the balance beam scale.

 

[dok7mm]

I'd back off lands to at least .010"+. If I'm reading correctly, you may be right on lands. 2900 fps is max or above in my 24" CM.

You didn't mention what method you used to find your lands, but the stripped bolt method is very accurate. Work off your base to ogive measurements and do setting depth tests.

 

[338 dude]

I reloaded some rounds that I wanted to test using 140 RDF and RL-17. I tried to be super careful and meticulous with these loads. I loaded up a group of 25. From 41.1 to 42.3 in .3 increments. I'm using Hornady brass and CCI #200 primers. The first group I shot I was hitting 2850fps. When I got the 41.4 group, I had 2 shots at 2900 fps and blew a primer. Stopped there. I should have been seeing around 2700 - 2725 with these 2 loads. I purchased a Lyman digital scale with trickler. I would assume this would be a decent unit. I have re-calibrated, zeroed, etc. This is the second time I've loaded a group only to have them way hotter than expected. I set the oal at 2.87 because I measured my rifling at 2.9 and these still fit in my AI mags. I'm shooting a Thompson Performance Center LRR in 6.5 with a 24" barrel.

Where do I start figuring this stuff out? My only guess is that my powder grains reading is off and the scale is reading lighter than it should.

You can get a set of check weights cheap enough to verify your scale also a lot cheaper than buying aNother scale

 

[Scott E Ames]

I think your assessment that the scales are giving your a heavier than indicated load is likely correct. Looking at the Hornady manual the max RL17 load for 140's is listed at 41.3 grains. Maximum safe velocity is exactly what you state. You might want to invest in some calibration/test weights or as others have suggested a balance beam scale. The calibration weights, when working with near max loads, are always a good idea.
A blown CCI primer with those high velocities is certainly a very high or dangerous pressure sign.

Bill posted about the weights while I was doing my slow typing and checking the manual. I didn't try to steal his suggestion. Great minds think along the same lines.

 

[DUSTY NOGGIN]

wow way too hot

 

[AntiPattern]

Thanks for the info guys. I think I'll try to find some weights first and make sure my scale is working properly. I used the hornady gauge to check my lands. I also did it the old fashioned way with a slice in the neck and load the projectile. Both came in at 2.90 and 2.91 so I took the lower. I might try pulling back off the lands just a bit more as well.

 

[25WSM]

You probably have all the check weights you need. Bullets. Bullets are very close the the weight they say they are. Put a 55 grain bullet on there and see what you have. Most bullets are within a couple 10ths in weight. A couple 10ths won't hurt your loads if you start low and work up. When your loads are 200 to 250 fps faster than book you are definitely over pressure. You can safely push a 140 to 2850 in the Creed with rl26. But first things first borrow a scale and check yours out or borrow a check weight. Most scales come with a check weight of some sort. You can even let a friend weigh some nuts and bolts and use them for comparisons. If your scale checks out then you really just need to lower your charge weights to stay safe.
Shep

 

[Scott E Ames]

You probably have all the check weights you need. Bullets. Bullets are very close the the weight they say they are. Put a 55 grain bullet on there and see what you have. Most bullets are within a couple 10ths in weight. A couple 10ths won't hurt your loads if you start low and work up. When your loads are 200 to 250 fps faster than book you are definitely over pressure. You can safely push a 140 to 2850 in the Creed with rl26. But first things first borrow a scale and check yours out or borrow a check weight. Most scales come with a check weight of some sort. You can even let a friend weigh some nuts and bolts and use them for comparisons. If your scale checks out then you really just need to lower your charge weights to stay safe.
Shep

Larry Potterfield may want to pay you some hush money. He has $45 from me for the weights. Makes me feel like an idiot as I weigh most new lots of bullets and know how consistent the weights are.

 

[crystalgayleguy]

if you have some kind of wind flow air conditioning or fan it will bother the scales let us know

 

[25WSM]

Really the most important part of your scale is repeatability. If it's off a wee bit you just need to know how far off it is so you don't over pressure. Typically electronic scales once calibrated give a very accurate weight. But balance beam scales seem to be all off just a bit from each other. But I believe balance beam scales are more consistent than cheaper electronic scales. Once you get into sartorious and a&d scales your getting to quality that is repeatable. But you into big money too. The 10-10 and M5 balance beam scales are very good and can be picked up on eBay for 50 to 100 bucks. Do a little tune up on them and they will weigh to the kernel of powder. It is amazing how close bullets are to their stated weight.
Shep

 

[25WSM]

For sure wind of any type can mess with your repeatability. Also with electric scales you may need a line conditioner to get good results. Plus they need warm up time. PIA so I just stick to what I know works perfectly every time. Balance beam. There are some little tricks to get best results out of them but I tested my balance scales out against a Sartorious and the guy was amazed how consistent my powder charges were.
Shep

 

[ShtrRdy]

How many rounds does the barrel have through it? Is this a new or used gun? I'm wondering if the
barrel is fast.

 

[Stiltsville]

Buy a 30 buck electronic scale on Amazon. I have 2 of the Frankford Arsenal ones that have been dead on for several years.