Backwards results w/ HBn

[scout1]

I am confused with the results I've been getting over the last two trips to the range with HBn coated bullets. I'll explain my process and findings and hope someone can help me figure out whats going wrong.

I clean and dry all bullets before coating. My coating process was taken from the how to pages of the bulletin here on 6BR. I use a large pill bottle with steel BB's and HBn 70nm in a vibratory cleaner for 3 hours. I then roll them back and forth in a towel to clean off the exess. My coating turns out pretty good based on what I've read here. I also bought some 91 percent Isoprople Alcohol to use as a medium to suspend the HBn and precoat the barrel with a rod and patch.

Before starting my testing I had fired 115 rounds through a new Broughton 5c barrel chamberd in 7WSM. My base speed average as tested before starting this test was 3102 fps. Average was taken using a new CED M2 with IR screen set up.

I was told and have read that I should be seeing a decrease in speed of between 35 and 50 fps. However I have actually had an increase to 3146 fps with the same charge and seating depth. Can anyone make any sense of this or better yet has anyone else experienced this as well. I have 40 coated rounds through the barrel and I'm lost and don't know what to do . Please help.Thanks, Jon

 

[Heavies]

Are you getting any pressure signs or drop in accuracy?

I don't know what my before was with the HBN becase I started fresh load development when I started the HBN.

I too, am interested with other's experiences with HBN.

 

[scout1]

I'm not getting any pressure signs yet and POA and POI are the same at 100 yards. I didnt expect a change in POI as far as elevation at 100 yards but I did expect the chrono to tell me a different story based on my reading here.
The only real aggressive cleaning I;ve done on this barrel was right before I started this HBn process and used a borescope to check for carbon and copper. I started with a pre coated barrel as described above. I dry patched the barrel after my 1st 20 rounds last week to clean out the powder residue and precoated again this week before shooting the next 20 rounds. Last weeks average speed was 3115 and this week was 3146. Accuracy and POI has been the same throughout. I hope you can see why I'm so confused.

 

[Heavies]

Maybe you got a little biuldup of carbon, if you only dry patched. I usually do a light cleaning with CLP after a range session, and do a pretreat right before the next session. I have found a light coat of alcohol/HBN followed by one dry patch worked best for me. I have little or no need for foulers to get real POI, but I found that there is some carbon and copper, but cleanup is much easier with the HBN.

 

[scout1]

What calliber and bullet are you shooting? I am running the 162 A-max .005 off the lands with 68.4 grains of IMR 7828 ssc. This gives me 94% case fill and I was looking to bump this up to 100% with the HBN. All of my cases are prepped and sorted by weight, my bullets are sorted by bearing length and I'm using the Redding type S seater.
I'll try a light patching between sessions with a mixture of Kroil and Shooters Choice along with a pretreat before my next session. Still feel that I should be seeing results opposite of what I'm getting. I havent re-borescoped the barrel yet, maybe I'll break it out tonight and do that.

 

[Heavies]

I use HBN in my .30-06. I used it on 155-178-208 Amax's, 155 SMK Palma's. Many powders from Rl-22 to Varget, from compressed to 80% load density. I can't really attribute any problems in the HBN from the results I'm getting.
Let me know if you see anything with the scope. (I wish I had one, seem like a good tool to have.)

Any one else out there have issue or tips with HBN?

 

[jo191145]

Jon

If you read the original Patent application for HBN coating bullets it does state you will see higher velocitys. It does not clearly state those higher velocitys will be reached with the same load but it does seem to imply it. Its a little vague on the subject.
The theory is HBN creates a ceramic like coating in the bore that fills in any voids creating a consistent seal around the bullet. Hard to imagine your new Broughton has these issues but thats the theory.
The above is just my memory from having read the patent. No quarentees.

For starters if your just dry patching I would not recoat the barrel with HBN prep. Just shoot it.

I've been using HBN for two years now. I've never tried any side by side velocity tests so I can't prove velocity loss or gain either way.

It seems to me one of the greatest attributes of HBN is its ability to keep certain powders from building excessive carbon in the bore.
In my PPC and 6BR 14 twist Ramshot X-Terminator and HBN can shoot all season without cleaning. Without HBN they cannot do this. Other more popular powders and HBN cannot do this. These two together seem to be a perfect match.

 

[PGS]

Scout 1, it could be that your barrel has sped up a little. My Broughton barrel sped up after 200 or so rounds

 

[tonyb]

Another thing that could cause an increase in fps. and pressure is the outside air temp.

Tony.

 

[scout1]

didnt really think about the density, we have been having some really outstanding weather here and both 20 round strings were shot within 10 deg F and the humidity was in the 50's on both trips. I have dry swabbed my barrel and inspected it with my borescope. There are no copper streaks or deposits and the usual little bit of carbon just ahead of the neck right before the rifleing. I was really surprized with how clean the barrel looked ater I dry patched it as I purposely didnt clean it before I left the range.
I just loaded 25 more rounds with the same COAL and load but I pollished up the bullets with a terry cloth rag after I seated them to remove any exess. I'll report back after my next range trip this comming week, maybe Monday ot Tuesday

 

[scout1]

gunny, how many FPS did you gain after 200 rounds. I've seen and heard this as well, just wasnt expecting it right in the middle of my darn testing

Tony, if your not down this way you better get here before this weather decides to leave. Nothing beates shorts and flip flops in October.

Donovan, I'll run 12 and 12 an hour apart to see if that will give me any variations. My ES on my first outing was 19 and it was 37 fps on my second. hopefully things will even out for me.

Thanks guys, Jon

 

[PGS]

Scout 1, my barrel gained 70 to 80 fps, this was over a ced chrono

 

[Elwood]

I think your barrel has just gained speed as Gunny has said. My 7WSM gained 110 fps after about 150 shots, I had read a lot about this happening but had never experienced it with any other rifle until the 7WSM.

 

[btm_54]

http://www.accurateshooter.com/forum/index.php/topic,3741653.msg35834586.html#msg35834586

 

[people]

I do not have the stats on all the shots I have fired but from the book that is quite faster than what a 220gr should be going.

 

[scout1]

Well Gentelmen, here is what happened today at the range. Started the morning at 10am with the temperature at 72 deg F. Dry swabbed the barrel with a clean patch and fired a couple foulers. The first string of 10 averaged 3104 fps with an ES of 19 fps. The second string wasnt fired untill 12PM, Temp was 78 deg F and humidity was in in the low 50's Second string of 10 averaged 3107 fps with an ES of 31 fps. There were a couple of rounds in the second group that bought me above my morning average so I'm not too bummed out but I'm still hovering around my uncoated speeds. So, unless my barrel has gotten faster and I'm not seeing it because of a loss in pressures due to the HBn I'm still a little unsure of things. The load is just as accurate as it was before I coated the barrel and bullets. I'm thinking about borrowing a friends Hi-score rifle rest (the one with all of the adjustments and pneneumatic recoil shock absorber) and seeing just how well the load shoots. This rifle will outshoot me all day long.
Thanks to all that posted. I will continue to test and will post anything I feel might be of rellavence. I will check back on a daily basis for any other suggestions.

Thanks agian, Jon