20 practical reloading ( high pressure signs)

[bobcat93]

Ok guys need some pointers here
I built an AR-15 chambered in 20 practical
I tried something new and no one would confirm if it would work or not, not even the barrel makers I talk to.
I used an 18" barrel with a mid length gas system. I had a hell of a time getting it to cycle and had to open up the gas port a little. Now it runs like a champ.
It shoots like a laser beam and is more accurate then I could imagine
But I'm getting high chamber pressure.
My last load was
Lake City brass
40 gr. Hornady v-max
Remington 7 1/2 br primer
Alliant reloader 10 x
Stared at 20.5 gr. These loads left the start of an ejector mark on the case head
I went up in .5 gr increments and pressure signs increased with flatten primers, ejector marks on the case heads, extractor marks on case rims.
So I stopped pulled all the bullets resized cases and that is where in at.
I've searched the internet and collected more reload data for use with other powders. H-335, VH 133 , reloading 15
I started with all suggested start loads still too hot
Then I tried 20 tactical data..same thing
Could it be I need to start even lower then suggested start loads?
How low should I go?
I was thinking if the lightest load I listed above of 20.5 gr. of reloader 10
Was looking like my max load I could work backwards in .5gr. increments untill I found something that shot good and seemed a little more safe..at least not beating up my brass..
What trouble could I get in other then getting a bullet stuck in my barrel..
A few AR-15 gurus told me this is new territory because it's a wildcat configuration..
I know this isn't normal practice but I know my rifle is 100% nothing wrong..could be it just won't work right with a 18" barrel and mid length gas system..but I won't know that till I've exhausted my reload combinations..
So there then a stuck bullet and letting the gas bleed off any one see an issue with my plan of working backwards on load development. I would assume I would see cycling malfunction before a stuck bullet..
Hope this all makes sense
Thanks for any tips or suggestions

 

[hogpatrol]

I would try switching primers. I don't know what it is but small Remington BR primers have boosted my pressures in every small case rifle I own from the .17FB to the .223. I use VV133 in the 20 practical with CCI BR4s and no issues, bolt or AR. The AR is a Whitley conversion with 24" barrel I've been shooting for over five years. It loves the Vmax and BKs but BIB 40s are the most accurate a longer ranges.

 

[Artpro]

I agree that neck turning could help. Milsurp brass is often thicker than is coml. brass-and necking down would make the matter worse.

 

[L.Sherm]

20 practical in an AR is not new territory it's nothing more than a 223 necked down to 20 cal. Call your barrel maker and find out what the neck dia. they reamed your barrel with should be min..232 if your not turning your necks.

 

[jepp2]

Milsurp brass is often thicker than is coml. brass-and necking down would make the matter worse.

Actually not for 5.56 brass. The thicker brass necks come with Lapua, Starline, and FC.

Agree with the above advice to find your neck diameter. You should be able to come pretty close by measuring your fired case necks and adding 0.001".

I have lots of 32 grain bullet loads that work well in my 20P's. Bolt and gas guns. And yes, using 20 Tactical loads should work well in your rifle. All mine have .233" necks, and the Lapua is the only one close to needing turned. Loaded Lapua run .2305".

 

[bobcat93]

I just tried that last loading . I turned all necks because I thought the same thing. Not the case but everything is nice and consistent now..there is a build up of brass after sizing down to .20 Cal.
I have tried CCI BR4 same issue
Would someone share a few loads they tried with starting load and max load..I have quite a few powders I could try.
Thanks

 

[jepp2]

Would someone share a few loads they tried with starting load and max load.

All the normal disclaimers, these were safe and not max loads in my rifles. But since you have a different rifle, using different powder lots, start low and work up. I can send you chrony data for any loads you want.

 

[hogpatrol]

Try VV133 with BR4 primers. Start at 22.5 & work up in .2 increments. Jump .010 40Vmax or 39BK.

 

[searcher]

First - about your initial cycling problem. That is more common than not with the .20 practical as well as .223's shooting light bullets. next time, rather than opening the gas port, buy a Wolff 'reduced weight' mainspring. A ten dollar fix without permanent mods will do the job more often than not. I have had so many problems with cycling on the small bullets, I install one in every build i do if they will be using those small pills. For loads, When you neck down to .20, you end up with thick necks. I'd load up a dummy cartridge and drop it into your chamber and see if it is entering the chamber all the way - and whether it will freely come right back out. Maybe put some die on the outside of the neck to indicate tight clearance. I turn all my necks to bring them down to the thickness they were before necking down and it greatly improves accuracy for me. Also check the length of your brass, as excessive length my be pinching the bullet when the chamber closes, creating high pressure. I use Redding bushing dies to give exacting control on the neck tension. Load a few dummies and let the bolt slam them home. After ejecting them, check overall length of the round to see if maybe the bullet is sliding into the lands when the bolt closes - which can also cause pressure spike. On a load:
L/C cases L/C cases Rem case
Tula .223 primer Federal A/R primer 22.2 H-4198
40 V-Max 39 Blitz King 32 v-max
22.3 grns. LT-32 Powder 22.3 LT-32 Federal A/R primer
Fired at 38 deg. temp / 3,500 f.p.s. Fired at 38 deg. temp. / 3,528 f.p.s. 3,881 FPS/ temp not noted
These are not remotely hot in my rifle and are very accurate. (Avg. .400" 5-shot groups or less) Hart 26" 1-8 tw.

While these are reasonably mild in my rifle, I'd drop to start! I'd also change the incremental increases from 1/2 grain to 3/10th grain as the entire accuracy window will be around 1/2 grain to 6/10 most often with this cartridge. Much harder to figure out where you are in that window with big jumps. I'd really look hard at your neck situation. Good luck

 

[searcher]

Forgot to mention you need to chrono your loads.l if you are at "red line" with what are normally considered to be starting loads, backing off may be all that is in order after ascertaining there are no safety risks with the necks, etc.

 

[bobcat93]

Good tips guys thanks..I tried to lighten my buffer, I have an adjustable gas block..like I stated I've done all the checks in my opinion before I opened up the gas port.
I've worked through this rifle with a couple of the knowledgeable guys over at AR-15.com ( I trust there knowledge)
The only thing some one stated case trim length..what are you guys trimming your brass to for the .20 practical 1.75"
Oh and I'm shooting aroumd 3300 fps. From my 18" barrel..

 

[nmkid]

Not much help here as I have a bolt action. I keep my case at 1.760 with CCI BR and 25.0 grs. of H-335 pushing a 40 Vmax. Hope you get things figured out. The 20P is a blast to shoot!

 

[bobcat93]

Not much help here as I have a bolt action. I keep my case at 1.760 with CCI BR and 25.0 grs. of H-335 pushing a 40 Vmax. Hope you get things figured out. The 20P is a blast to shoot!

NMkid, is that your max load..can I reduce this load by 10%

 

[LitLBoy]

8208 with Fed. Gold Match primers. I shoot 26 gr. with 39 gr. blitz kings. Bolt gun load.
LitLBoy

 

[nmkid]

NMkid, is that your max load..can I reduce this load by 10%

Yes, that is my max load for my rifle. I show just the beginning signs of pressure on the case. Note; I did have my firing pin bushed. I'll have to see what the case tells me in summer temps'. I hope they will be OK. If not, I'll go down in .1 increments. So I guess a 10% starting load would be around 23.5 grains. Ironically, that is what I used as a starting load and of course went up from there. Magneto Sporter reads an average of 3750 fps out of my 28" barrel. Have seen some guys, (Internet commandos?) post those speeds with 24"-26" barrels. Maybe there are powders that will do it for them but, I'm satisfied with what I'm getting.

 

[Smalltruck]

Mines a bolt gun with a 27 inch barrel. 10x just gave me headaches. My favorite is h332 at a max of 25.0 with a 32grain varmageddon. Velocity was 4000fps at 4700 feet elevation. But it's really unhappy in the wind here in Wyoming. Using cci primers the Remingtons had pressure problems.

 

[nmkid]

Mines a bolt gun with a 27 inch barrel. 10x just gave me headaches. My favorite is h332 at a max of 25.0 with a 32grain varmageddon. Velocity was 4000fps at 4700 feet elevation. But it's really unhappy in the wind here in Wyoming. Using cci primers the Remingtons had pressure problems.

I had my firing pin bushed and it resolved cratering primers to a large degree.

 

[chuckshooter]

I hesitated to speak up, because my three 20p's and two 20t's are bolt guns, but IMO 10x is the wrong powder for this cartridge,it spikes pressure too easily. you are working up a load , every thing seems fine and then too much pressure. I shoot 2015 or 322 in mine and no issues. there are other good powders choices as others have said, just not 10x. I also don't like rem 7 1/2 either, CCI 450's is what I use.. you asked for tips or suggestions., this is my two cents worth

 

[fredo]

Another opinion to recommend changing powder...

Ditch the 10x.

I tried it in my .20TAC AR and experienced pressure issues as well. To the point of having to hammer a stuck case/froze bolt out with a piece a 2x4". Don't ask...

Try either Benchmark or H322. 35Bergers scream with 322, and 39BKings did same with Benchmark.
Keep realistic and don't expect too much velocity from that short 18" barrel, though. A 20cal wants a couple-6" more length to show it's true colors. Mine was 23", and that was as short as I cared to limit it to...

Be careful & have fun!

 

[Alvan]

Bobcat93, any update on your load development?
I am in a similar situation with a BHW 18.5" 1:10 (gas block 12.75" from barrel flange) medium contour barrel built up for a somewhat lightweight coyote gun to carry while pushing ditches and brush. I have not had issues with cycling, as recommended in forum earlier, built with Wolf light buffer spring.

I have not done enough load development yet, but a fairly light load of 22.8g H322 with 40 Nosler BTV was around a quarter size at 100 yards, but I have not ran through chrono yet. I really would like to get as high a velocity as I can to minimize holdover out to around 300 yards.

I only use this gun for hunting, so I wanted as temp stable a powder as possible, and can just take time reloading for the few rounds actually needed. Now if I was going to go PD hunting, I might consider ball like Tac, BLC2, or H355.

Unfortunatel, or fortunately, depending how you look at it. I have 4 other guns I need to do load development on, but I will post my findings when I get the 20P work done.
Looking forward to hear your results, as there is not much data out on shorter 20P barrels.

Thanks