Reloading 223 short stroke issue

[DanielC]

I have a Sig M400 and I'm having a problem with short stroking. I've run a variety of factory ammo through my M400; 55, 62, 64 and 69 grain from Hornady, Winchester and other reputable companies. 500 to 600 rounds and no problem. I've started to do my own reloading. The following are .223 loads not 5.56 loads. Sierra 65 gr SBT with 23.9 grains of IMR4895, no cycling problems. Barnes 62 gr TSX with 23.9 gr Varget, no problems. Sierra 69 gr HPBT with 23.7 gr IMR 4895, no problems.

My problem is in using the Sierra 69 gr HPBT with 19.7 grains of IMR 4198. i.e. 1. Firing with one round in the clip the bolt does not travel back far enough to lock in place, most of the time. And 2. Firing with multiple rounds in the clip the bolt travels back far enough to pick up the next round but the round does not seat itself correctly on the bolt face and as a result the cartridge jams in the receiver. As an added note this problem is intermittent. I can fire two, three or sometimes four rounds before I get a jam.

I suspect that the pressure envelope (duration) of the IMR 4198 is not long enough to force the bolt to retract completely.

The question I have is; do I increase the powder load (from 19.7 to 20.0) which will increase the pressure spike but reduce the pressure duration or decrease the powder load (from 19.7 to 19.4) which will reduce the pressure spike but increase the pressure duration ?

Any help will be appreciated.

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[Swedish K]

IMR site says max load is 19.5 <broken link removed>

69 GR. SIE HPBT IMR 4198 .224" 2.235" 18.3 2706 46,300 PSI 19.5 2818 52,300 PSI

 

[rick benjamin]

Sierra 69 gr hpbt IMR4198
http://accurateshooter.net/Downloads/sierra223ar.pdf

IMR 4198 is the fastest burning powder on that data sheet.
I would use it for lighter bullets.
Watch for pressure indicators (flattened primers, etc)
Consider investing in a Chronograph (Midway sells the Shooting Chrony among others)

I use IMR 4064 for 69 gr bullets.

 

[rick benjamin]

I found two articles "Measuring Bullet Velocity"
Looks interesting.
[0812.4752] Acoustic methods for measuring bullet velocity
[physics/0601102] Measuring Bullet Velocity with a PC Soundcard

 

[balaperdida]

I found wo articles "Measuring Bullet Velocity"
Looks interesting.
[0812.4752] Acoustic methods for measuring bullet velocity
[physics/0601102] Measuring Bullet Velocity with a PC Soundcard

Has anyone seen an Android app for this? thx

 

[DanielC]

To Swedish K
According to the Sierra Reloading Manual 5th Edition, under 223 Remington (AR-15) section, page 221, the load data for the .2234 69 gr HPBT matchking COAL = 2.260" is:
18.8 gr, 2500 fps, no psi data to a max of 20.3 gr, 2750 fps, no psi data. I guess another way to ask my question is: "Have any reloaders run into this problem and if so do they have a solution? I have heard that IMR 4198 is a finicky powder to work with due to its faster burn rate.

 

[AMProducts]

DO NOT USE IMR 4198 IN .223 WITH AR-15's IT DOES NOT WORK

Also, this should be in the reloading forum. Not in the new-user forum

 

[DanielC]

DO NOT USE IMR 4198 IN .223 WITH AR-15's IT DOES NOT WORK

Also, this should be in the reloading forum. Not in the new-user forum

Thanks, new user my mistake....

 

[GFO270]

I know I am a couple years late to the party but I wanted to post my $.02 on IMR 4198 in ARs. It absolutely does work. Just like anything else you have to find the right load for your rifle. I use 21 gr of IMR 4198 and it cycles flawlessly through my Stag Model 2T. I have also shot it from my dad's Bushmaster and PSA build and my father and law's Colt. All have cycled it fine. I first tried 19.8 gr and that did not cycle great from any of the rifles except the Stag.

It is also worth noting that Sierra publishes different data for ARs as opposed to bolt action rifles. For bolts they max out at 20 gr of IMR4198 while they recommend not exceeding 20.3 gr for ARs while using a 69gr HPBT Matchking.

 

[v0lcom13sn0w]

start using imr 4320 and be done with it

 

[kod38]

I run 19 grains 4198 with 55gr FMJBT with no issues , and my brass ejects far as well.
I have a carbine length gas system, t2 buffer and muzzle break.
Are you running a mid length?
Also make sure gas block is lined up, bolt asm is in good working order etc.

 

[fredball]

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