Load development ...





rw blakemore

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i am more interested in your RPR and how it is shooting actually...my buddy has an AR-10 in 65CM with a proof barrel and that thing is a hammer.

back to the 300wm did that gun have a short barrel?
LongRange, was going to reply to you right after looking at Flying Zebra’s post but I forgot to do so. Sorry for the slow reply.

The 300 WM had a 22.5” carbon fiber barrel; 1:10 twist.

I built a 6.5Cm AR10 about 1.5 years ago. Was curious to see how well a 6.5 Cm semi-auto would work. I don’t enjoy semi-autos that much so I only used it enough to break-in the barrel and work-up a decent load for it. It liked 43.0 grains of H4350 and Berger’s 130 grain OTM Hybrid bullet traveling at 2840 fps. Used it at 60 F to 70 F ambient temps … shot .2 to .5 MOA consistently. Maybe I should bring it out of closet and park the RPR for a while. What do you think?
 

LongRange

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i thought that 300wm you talk about had a short barrel...i ran 28" barrels on the 300 i shot but it was not a hunting rifle.

im not into the gas guns either...i shot about 2k through an AR-15 and sold it...just didnt do anything for me.
 

rw blakemore

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i thought that 300wm you talk about had a short barrel...i ran 28" barrels on the 300 i shot but it was not a hunting rifle.

im not into the gas guns either...i shot about 2k through an AR-15 and sold it...just didnt do anything for me.
Good to hear from you. If all goes well I’ll be back in town Thursday and will shoot the RPR load matrix on Friday. Plan to shoot 3 rounds each of 40.9, 42.3, and 42.8 grain loads at .015”, .025” and .035” off the lands. Everything is loaded and ready to go. The place where I shoot will likely be muddy, so I plan to shoot everything at 100 yds. Less driving/walking through the mud that way. I know you wanted to see 400 yd results, sorry. I may take the best of each load from the Friday test and run them at 400 yds next week when things dry out.
I think we can tell from the 100 yd results what the loads will do at 400 yds. If we were using a bullet that didn’t “go to sleep” until it was two or three hundred yds out I wouldn’t be so confident. I developed all of my loads for RPR factory barrel at 100 yds. Never had any surprises using the 142 SMK out to 1000 yds.
 

rw blakemore

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Final Results …

I shot the matrix today. See the attached targets. I’ve also attached a revised version of the ladder chart that is shown in post #143. From all of this, I conclude the following:
  • For 40.9 grains, a COAL of 2.835 is an acceptable load.
  • For 42.3 grains, a COAL of 2.835 is an acceptable load.
  • For 42.8 grains, a COAL of 2.815 is an acceptable load.
  • The revised ladder chart shows a definite flat from 41.1 grains to 41.6 grains for a COAL of 2.825”. Many of the loads run through the new barrel, prior to our recent testing, consist of 41.4 grains of H4350 and COALs ranging from 2.810” to 2.830”. For these, the group sizes range from .3 to .6 MOA.
  • However, 42.3 grain and 42.8 grain loads are not on a flat but still appear to be viable loads.
  • QL is a good tool for estimating load and velocity relationships for a wide range of cartridge configurations (COAL changes, various powder and bullet combinations, etc.) A final configuration can only be determined by testing particularly if neck tension is a variable.
  • Shooting a ladder is a time tested method and if results are properly interpreted it can be used to arrive at a suitable load even though that load may not correlate to any QL node.
So, I’ve gone full circle with our testing. I’m inclined to stick with a load of 41.4 grain and go shooting a lot more. Please let me know your thoughts on the test results.

409 grains.jpg

423 grains.jpg

428 grains.jpg

RPR65Cm Ladder 2   7feb2019.jpg
 

LongRange

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now your saying(according to QL im assuming)you have a flat spot from 41.1 to 41.6...maybe im wrong here but im not seeing it because you or QL are using averages for your numbers.

lets take a look at the actual numbers here in terms of extreme spreads and not averages....
40.8-40fps
41.1-12fps
41.2-32fps
41.4-15fps
41.7-37fps
42-25fps
42.3-63fps
42.6-23fps
42.8-21fps
42.9-22fps
43-35fps

and looking at the number of rounds fired for each group it looks as though the more rounds fired the worse the ES are....42.3 looks like 18 rounds total were recorded for an ES of 63fps but on either side only 3 shots recorded and the ESs are about 40fps better/lower...again maybe im wrong here but when the ESs are jumping all over the place like this im just not seeing a flat spot so if im wrong someone please show me and straighten me out here.

and yes i see you did your seating test but the high ESs are still a concern for me and should be for you...if youd like your ESs lower id first suggest you try a CCI450 primer and if they dont come down id swap out the firing pin spring....with the combo your running your ESs should easily be in the high singles to low doubles.
 
Last edited:

rw blakemore

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now your saying(according to QL im assuming)you have a flat spot from 41.1 to 41.6...maybe im wrong here but im not seeing it because you or QL are using averages for your numbers.

lets take a look at the actual numbers here in terms of extreme spreads and not averages....
40.8-40fps
41.1-12fps
41.2-32fps
41.4-15fps
41.7-37fps
42-25fps
42.3-63fps
42.6-23fps
42.8-21fps
42.9-22fps
43-35fps

and looking at the number of rounds fired for each group it looks as though the more rounds fired the worse the ES are....42.3 looks like 18 rounds total were recorded for an ES of 63fps but on either side only 3 shots recorded and the ESs are about 40fps better/lower...again maybe im wrong here but when the ESs are jumping all over the place like this im just not seeing a flat spot so if im wrong someone please show me and straighten me out here.

and yes i see you did your seating test but the high ESs are still a concern for me and should be for you...if youd like your ESs lower id first suggest you try a CCI450 primer and if they dont come down id swap out the firing pin spring....with the combo your running your ESs should easily be in the high singles to low doubles.
I was looking at the brass last night. No sign of extractor recess marks or flattened primers on the higher charge loads (casts doubt on QL’s pressure estimates). However, the primers are “cratered” for all loads.

I’ve been using GMM205M primers in the RPR since new. The ES has always been erratic when they are viewed over a wide range of loads. For the 41.4 grain load I shoot the ES has always run mid to high teens and the SD, single digit. None the less, you’re right. The CCI450 primer has a thicker walled cup and is a better choice. I’ll get some and try them. Thanks again for your support and recommendation.
 

LongRange

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that RPR barrel is probably like a hotdog down a hallway LOL...or a little loose in more serious terms...as far as the cratered primers i would not worry about that so much because its a factory bolt...if you pull the bolt and drop the pin youll see pin to hole is probably pretty sloppy also when the pin hits the primer its not that far out of the bolt which makes it worse...id look more at primers and bolt lift for pressure signs.

like i said theres no true way to know where pressures are unless your running pressure trace equipment...but if you SEE signs you are already over pressure...im not saying its ok or safe but ive shot a 260 with a 142smk 17% over book max and a 300wm with a 210smk 16% over book max so the worst thing about shooting hot-ish loads is brass life.
 

rw blakemore

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Hello LongRange,

I wanted to wrap up this thread with some positive results.
I was away most of February and March. I spent a couple of weeks in early April continuing my load development using the SMK 142 grain bullet that was used during our earlier discussions. No matter what load configuration I tried, the results were no better than we saw during the time you were reviewing my load development process and results.

I gave up on the SMK 142 a few weeks ago. Using my version of the load development process you shared with me, I evaluated some other bullets I tried when I first starting shooting a 6.5 Creedmoor. Berger’s 130 grain AR Hybrid OTM provided acceptable and consistent results (Vm~ 2840 fps, ES= 14, SD=6, .35 MOA. I use this bullet in a 6.5 Creedmoor semi-auto.

Preferring a heavier bullet, I purchased some Berger 140 grain Hybrid bullets. I began by shooting a ladder with a load range of 39.6 to 42.4 grains. The starting COAL was determined by the maximum COAL I could stuff in the magazine I use. The bullet ogive was .060 inches from the leads. Ladder results are shown in the attachments. Loads using 40.0, 40.2, 41.0, and 42.4 grains of H4350 produced good results. Corresponding velocity nodes were 2710 fps, 2790 fps, and 2850 fps. I chose loads that would run around 2700 fps and 2780 fps for reasons we previously discussed.

Next test was to evaluate the change in accuracy/precision with COAL. I shot COALs of 2.855, 2.840, and 2.825 inches for both 40.0 grains and 40.9 grains. A COAL of 2.840 inches produced the best results. See the attachment labeled “RPR65Cm COAL”.

Finally, I wanted to see if case neck hardness change would significantly impact the previous results since new brass was used for those tests. I think I mentioned that I use an AMP annealer. The analyzer function built into the AMP machined recommended a code of “0152” to obtain a case neck hardness that would be very near the factory new brass neck hardness. Using this code to produce “nominal” neck hardness, I got results very near what I had seen using new brass. So, I went a couple of steps harder and a couple of steps softer to see if there was anything to be gained. Refer to the RPR65Cm Neck Hardness attachment for results.

To sum up, after all of our previous work I abandoned the 142 grain SMK bullet. The factory stock RPR barrel really liked the SMK bullet. The Proof Research barrel, not so much. I’ve gone to the range twice in the past couple of days and hit 1 MOA metal out to 1000 yards. Soon, I’ll put up some paper so I can see how the precision holds up at distance. I think I finally have a good load.

Thanks again for your help.

RPR65Cm Ladder1.jpg

RPR65Cm Ladder2.jpg

RPR65Cm COAL.jpg

RPR65Cm Neck Hardness.jpg
 

LongRange

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nice!!
so if you want to try and tighten that up any now is when you try different primers...id suggest you try fed210Ms if you do.

also you see that your test on the neck hardness had very little if any effect on your groups,ESs or SDs...is annealing important for consistency? sure it is but not as much as a lotta ppl think.