Heat: Effect on handloads?

azredhawk44 · June 6, 2010, 06:44 PM

I just shot in a match today and I saw (I think) a distinct effect of heat on my loads.

Two boxes of ammo, 50rds each.

Prvi Partisan once fired .308 brass, trimmed to 2.005
CCI 200 LR primer
IMR 4895 42.0gr

Those are the common elements. Uncommon elements:

Box 1:
165.0gr Midway bulk bullets: polymer tip (red color), blemished lot @ discount
2.775" OAL

Box 2:
164.5gr Midway bulk bullets: polymer tip (brown color), blemished lot @ discount
2.760" OAL

The bullets were ordered as 1 lot of 500 bullets, 165gr blemished polymer tipped from Midway, which came in separate 100rd blue boxes. The weight differences per batch were surprising, as well as the differing construction materials. I had intended to load 100 identical rounds, but had used 50 of the first box for a different project and so loaded 50 for this match and realized I needed more (for the sighters), so I opened the second box and was surprised by the color of the tip varying and the weight being off by half a grain from the first box.

The OAL differences was due to the ogive being different from one bullet batch to the next. I hadn't worked up a load specifically for these bullets, and I guess it is a good thing I didn't, since they do vary so much.

The match was 50 rounds, with 5 sighter rounds allowed prior to beginning.

I shot my sighters with the 164.5gr bullets with the brown tips, then my standing and seated. I had shot 5 rounds from this box earlier at the next-door range to confirm a functional zero prior to the match beginning, so that made 30 out of 50 consumed, leaving 20 rounds for the slowfire prone stage.

For the rapid fire prone, I switched to the red-tipped box in order to save the last 20 rounds of the brown-tips that had a good zero.

However, I didn't notice that the sun crept forward and exposed the second box (the red-tips) to the direct sunlight. They were noticeably hotter than the first batch of brown-tips, almost uncomfortable to handle.

This second batch shot with a group center that was about 3MOA off from the first group, down and left towards 7:30 on a clock face. The groups also opened up a LOT. My rapid-fire prone is usually about 3MOA total for all 10 shots including mag change. This group blew up to almost 6MOA at 200 yards... 11 inches and change.

I went back to the other ammo (brown-tips) for my slowfire prone 20rd session and I am comfortable with the results of that.

Was the above rapid fire session with the red-tip ammo an overpressure situation where the groups go to heck as the load leaves the "sweet spot?" I don't have any intention of finding a pet load with these bullets and frankly I just used my Hornady 168gr BTHP load data as a starting point for these 165's, and I intend to use them for shorter-range matches and general practice. I have 500ct 168gr A-max bullets for some 600 yard matches coming up in a few weeks.

I'm just concerned about the possibility of my groups going to heck due to cartridge exposure to Arizona sunlight.

Should I be? Or is it likely that the bullet variation or OAL variation caused this anomaly?

gearheadpyro · June 6, 2010, 06:59 PM

Very possible heat could be the culprit. I've noticed that my loads do strange things when they get hotter (or colder).

To combat this I usually A) set my rounds in the shade in the summer, and make sure they stay in the shade, or B) set my rounds in the sun in the winter, or somewhere that my body heat will keep them warm(er). This combo seems to give me the best overall results.

Could also be something to do with using a different bullet. It may have a different bearing surface, be a lower grade (hunting bullet maybe?), or just be a crummy bullet (it was in the defective lineup). My experience is that you have to pay for the best, they don't usually come in blemished lines. Have the red tipped bullets shot well for you before (out of this lot)?

Just my .02.

azredhawk44 · June 6, 2010, 11:23 PM

gearhead:

Thanks for your input.

I just checked the remaining 100ct boxes. There is 1 more box of brown-tips that are copper-oxidized worse than I've seen outside of mistreated milsurp ammo, and 2 more boxes of red-tips that are pristine in appearance. The first box of brown-tips were nice and clean, like the red-tips. That makes 2 boxes of browns and 3 boxes of reds. I have not weighed the remaining boxes for uniform weight, yet.

So far, my reloading endeavors have included:

50rds:
Federal once fired brass
CCI #200 LR primer
red-tip
42.0gr IMR 4895

50rds:
Prvi Partisan once fired brass
CCI #200
red-tip
42.0gr IMR 4895

50rds:
Prvi Partisan once fired brass
CCI #200
brown-tip
42.0gr IMR 4895

I have not yet shot the Federals, and I still have 40 rounds of the red-tip Prvi loads left.

All in all, I'm wondering if the brown-tips are "good" bullets that are just oxidized, and the red-tips are bullets that are not uniform internally. I guess I won't know unless I go and shoot the red-tips for groups.

The Prvi brass has thicker walls than the Federal brass, so if I am close to accuracy-related overpressure it should show up as wider groups with the Prvi than the Federal loads, and the heat would have been the straw that broke the camel's back, so to speak. I'll test, and if it comes out that way then I will cut the load half a grain in the Prvi.

But, if they're just reject bullets, then it won't matter.

Of course... I could have just blown the rapid fire prone stage, too.

But it's so much more convenient to blame the ammo.

riverwalker76 · June 7, 2010, 12:06 AM

I've found heat does some funny things with my IMR 4895 loads. It has gotten to the point that I don't use IMR4895 for anything but hunting!

I've developed some really nice loads using IMR 8208 XBR and they work great whether it's 20 deg. Fahrenheit or 95 deg. Fahrenheit. Heat doesn't seem to affect the performance of 8208 like it does 4895.

azredhawk44 · June 7, 2010, 12:19 AM

IMR 4895 is not my first choice powder... back during the recent crunch I stepped aside from my preferred AA 2520 because I couldn't find any, and have been through 1 8lb jug of 4895 and working on my second in that time. I still have about 6 pounds left in the jug and I haven't been out to look for 2520 yet.

I don't have enough extreme hot/cold weather experience with 2520 to say if it is suitable for variable temperature use. I just seemed to have found my preferred consistent load with it.

Failing that, I've also used H335 with some success. Not as much as 2520, but I gave 2520 a longer run.

Anyone have experience with these ball powders in extreme heat environments?

June 6, 2010, 06:44 PM	#1
azredhawk44 Junior member Join Date: September 28, 2005 Location: Mesa, AZ Posts: 6,465	Heat: Effect on handloads? I just shot in a match today and I saw (I think) a distinct effect of heat on my loads. Two boxes of ammo, 50rds each. Prvi Partisan once fired .308 brass, trimmed to 2.005 CCI 200 LR primer IMR 4895 42.0gr Those are the common elements. Uncommon elements: Box 1: 165.0gr Midway bulk bullets: polymer tip (red color), blemished lot @ discount 2.775" OAL Box 2: 164.5gr Midway bulk bullets: polymer tip (brown color), blemished lot @ discount 2.760" OAL The bullets were ordered as 1 lot of 500 bullets, 165gr blemished polymer tipped from Midway, which came in separate 100rd blue boxes. The weight differences per batch were surprising, as well as the differing construction materials. I had intended to load 100 identical rounds, but had used 50 of the first box for a different project and so loaded 50 for this match and realized I needed more (for the sighters), so I opened the second box and was surprised by the color of the tip varying and the weight being off by half a grain from the first box. The OAL differences was due to the ogive being different from one bullet batch to the next. I hadn't worked up a load specifically for these bullets, and I guess it is a good thing I didn't, since they do vary so much. The match was 50 rounds, with 5 sighter rounds allowed prior to beginning. I shot my sighters with the 164.5gr bullets with the brown tips, then my standing and seated. I had shot 5 rounds from this box earlier at the next-door range to confirm a functional zero prior to the match beginning, so that made 30 out of 50 consumed, leaving 20 rounds for the slowfire prone stage. For the rapid fire prone, I switched to the red-tipped box in order to save the last 20 rounds of the brown-tips that had a good zero. However, I didn't notice that the sun crept forward and exposed the second box (the red-tips) to the direct sunlight. They were noticeably hotter than the first batch of brown-tips, almost uncomfortable to handle. This second batch shot with a group center that was about 3MOA off from the first group, down and left towards 7:30 on a clock face. The groups also opened up a LOT. My rapid-fire prone is usually about 3MOA total for all 10 shots including mag change. This group blew up to almost 6MOA at 200 yards... 11 inches and change. I went back to the other ammo (brown-tips) for my slowfire prone 20rd session and I am comfortable with the results of that. Was the above rapid fire session with the red-tip ammo an overpressure situation where the groups go to heck as the load leaves the "sweet spot?" I don't have any intention of finding a pet load with these bullets and frankly I just used my Hornady 168gr BTHP load data as a starting point for these 165's, and I intend to use them for shorter-range matches and general practice. I have 500ct 168gr A-max bullets for some 600 yard matches coming up in a few weeks. I'm just concerned about the possibility of my groups going to heck due to cartridge exposure to Arizona sunlight. Should I be? Or is it likely that the bullet variation or OAL variation caused this anomaly?

June 7, 2010, 12:06 AM	#4
riverwalker76 Senior Member Join Date: February 13, 2010 Location: Kentucky Posts: 993	I've found heat does some funny things with my IMR 4895 loads. It has gotten to the point that I don't use IMR4895 for anything but hunting! I've developed some really nice loads using IMR 8208 XBR and they work great whether it's 20 deg. Fahrenheit or 95 deg. Fahrenheit. Heat doesn't seem to affect the performance of 8208 like it does 4895. __________________ *Admiral Isoroku Yamamoto* - “You cannot invade the mainland United States. There would be a rifle behind each blade of grass.”

June 6, 2010, 06:59 PM	#2
gearheadpyro Senior Member Join Date: September 3, 2009 Location: Charleston, SC Posts: 169	Very possible heat could be the culprit. I've noticed that my loads do strange things when they get hotter (or colder). To combat this I usually A) set my rounds in the shade in the summer, and make sure they stay in the shade, or B) set my rounds in the sun in the winter, or somewhere that my body heat will keep them warm(er). This combo seems to give me the best overall results. Could also be something to do with using a different bullet. It may have a different bearing surface, be a lower grade (hunting bullet maybe?), or just be a crummy bullet (it was in the defective lineup). My experience is that you have to pay for the best, they don't usually come in blemished lines. Have the red tipped bullets shot well for you before (out of this lot)? Just my .02. __________________ www.southernmarksman.com Owner of & Chief Instructor for The Southern Marksman, LLC NRA Life Member, NRA CRSO, Multi-Discipline NRA Certified Instructor

June 6, 2010, 11:23 PM	#3
azredhawk44 Junior member Join Date: September 28, 2005 Location: Mesa, AZ Posts: 6,465	gearhead: Thanks for your input. I just checked the remaining 100ct boxes. There is 1 more box of brown-tips that are copper-oxidized worse than I've seen outside of mistreated milsurp ammo, and 2 more boxes of red-tips that are pristine in appearance. The first box of brown-tips were nice and clean, like the red-tips. That makes 2 boxes of browns and 3 boxes of reds. I have not weighed the remaining boxes for uniform weight, yet. So far, my reloading endeavors have included: 50rds: Federal once fired brass CCI #200 LR primer red-tip 42.0gr IMR 4895 50rds: Prvi Partisan once fired brass CCI #200 red-tip 42.0gr IMR 4895 50rds: Prvi Partisan once fired brass CCI #200 brown-tip 42.0gr IMR 4895 I have not yet shot the Federals, and I still have 40 rounds of the red-tip Prvi loads left. All in all, I'm wondering if the brown-tips are "good" bullets that are just oxidized, and the red-tips are bullets that are not uniform internally. I guess I won't know unless I go and shoot the red-tips for groups. The Prvi brass has thicker walls than the Federal brass, so if I am close to accuracy-related overpressure it should show up as wider groups with the Prvi than the Federal loads, and the heat would have been the straw that broke the camel's back, so to speak. I'll test, and if it comes out that way then I will cut the load half a grain in the Prvi. But, if they're just reject bullets, then it won't matter. Of course... I could have just blown the rapid fire prone stage, too. But it's so much more convenient to blame the ammo.

June 7, 2010, 12:19 AM	#5
azredhawk44 Junior member Join Date: September 28, 2005 Location: Mesa, AZ Posts: 6,465	IMR 4895 is not my first choice powder... back during the recent crunch I stepped aside from my preferred AA 2520 because I couldn't find any, and have been through 1 8lb jug of 4895 and working on my second in that time. I still have about 6 pounds left in the jug and I haven't been out to look for 2520 yet. I don't have enough extreme hot/cold weather experience with 2520 to say if it is suitable for variable temperature use. I just seemed to have found my preferred consistent load with it. Failing that, I've also used H335 with some success. Not as much as 2520, but I gave 2520 a longer run. Anyone have experience with these ball powders in extreme heat environments?